This image of the globular cluster NGC 1846 was taken by Hubble in 2006, and "remastered" in 2011. If you look straight down from the cluster center, you'll see a tiny green blip: that's the death throes of a star. Details and explanation are in my blog.

blogs.discovermagazine.com/badastronomy/2011/11/22/the-gr...

Image credit: NASA and The Hubble Heritage Team (STScI/AURA), with P. Goudfrooij (STScI)

Celestron 127SLT, Canon 1100d, 1x 20sec exposure

Messier 22 / M22 / NGC 6656 / The Great Sagittarius Cluster

NGC 6642 / The Tadpole Cluster

The Great Sagittarius Cluster is the brightest cluster visible from mid-northern latitudes, outshining famous clusters like the Great Hercules Cluster and the Great Pegasus Cluster. M22 contains over 80,000 stars and it is about 10,600 light-years away, orbiting the Milky Way. It is estimated to be 12.0 billion years old. A dense starfield surrounds this cluster because of its position near the Galactic Center (the center of the Milky Way).

NGC 6642 is a globular cluster about 26,400 light-years away. It is heavily obscured by interstellar dust. The cluster appears as a golden clump in the upper right.

Total integration: 5 hours 22.5 minutes (322.5 minutes)

07/18/19: 176 x 30 seconds ISO800

07/22/19: 197 x 30 seconds ISO800

08/25/19: 40 x 60 seconds ISO800

06/30/20: 4 x 120 seconds ISO200

07/14/20: 44 x 120 seconds ISO200

Location: Coral Springs, FL

SQM: 18.18 mag/arcsec^2 (Bortle 8/9)

Camera: Canon T3i (stock/unmodified)

Average camera temperature: 104 F (40 C)

Telescope: Explore Scientific ED80 f/6.0 Apochromatic Refractor (with ES field flattener)

Mount: Orion Sirius EQ-G

Guide scope: Svbony 50mm f/4.0 Guide Scope

Guide camera: Orion StarShoot AutoGuider

Software: N.I.N.A. with PlateSolve2 and PHD2

Pre-processed with PixInsight, processed with PixInsight and Paint.NET

Edited montage (created by NASA) of Hubble Space Telescope images of the globular cluster NGC 6752 and a dwarf galaxy hiding behind it.

Original caption: The universe is very cluttered. Myriad island cities of stars, the galaxies, form a backdrop tapestry. Much closer to home are nebulae, star clusters, and assorted other foreground celestial objects that are mostly within our Milky Way galaxy. Despite the vastness of space, objects tend to get in front of each other.This happened when astronomers used the Hubble Space Telescope to photograph the globular star cluster NGC 6752 (located 13,000 light-years away in our Milky Way's halo). In a celestial game of "Where's Waldo?", Hubble's sharp vision uncovered a never-before-seen dwarf galaxy located far behind the cluster's crowded stellar population. The loner galaxy is in our own cosmic backyard, only 30 million light-years away (approximately 2,300 times farther than the foreground cluster).The object is classified as a dwarf spheroidal galaxy because it measures only around 3,000 light-years at its greatest extent (barely 1/30th the diameter of the Milky Way), and it is roughly a thousand times dimmer than the Milky Way.Because of its 13-billion-year-old age, and its isolation - which resulted in hardly any interaction with other galaxies - the dwarf is the astronomical equivalent of a living fossil from the early universe.

A globular cluster is kind of a miniature galaxy containing thousands of stars rather than billions. This one is large for a globular cluster, containing hundreds of thousands or perhaps even a million stars. It's is usually called "The great globular cluster in Hercules" or M13 as it's the 13th object on Messier's list of deep-sky objects. It's about 25,000 lightyears away and orbits our own Milky Way. It's located on Hercules' thigh or side, depending on which stick figure of Hercules you choose to see. Under exceedingly dark skies (think rowboat in the middle of the pacific ocean) with no moon, this is visible to the naked eye as a small light gray patch on a darker sky.

My full shot also caught a nearby galaxy but it was just a couple lighter grey pixels, not worth seeing. :)

This is something like 22 images, each at 25 seconds with a digital rebel XTi, aligned and stacked in IRIS. It was under a full moon which was washing out everything. :( Taken with an 8" newtonian telescope.

Edited European Southern Observatory/Deep Sky Survey 2 image of the globular cluster NGc 3201, set in a field of stars. Color/processing variant.

Original caption: This wide field view shows the sky around the globular star cluster NGC 3201 in the southern constellation of Vela (The Sails). As well as the rich cluster itself, which appears at the centre, this view also reveals huge numbers of stars within the Milky Way, along with a few much more distant galaxies. This picture was created from images forming part of the Digitized Sky Survey 2.

Edited Hubble Space Telescope image of the globular cluster NGC 6638. Color/processing variant.

This star-studded image from the NASA/ESA Hubble Space Telescope shows the heart of the globular cluster NGC 6638 in the constellation Sagittarius. The star-strewn observation highlights the density of stars at the heart of globular clusters, which are stable, tightly bound clusters of tens of thousands to millions of stars. To capture the data in this image, Hubble used two of its cutting-edge astronomical instruments: Wide Field Camera 3 and the Advanced Camera for Surveys. Hubble revolutionised the study of globular clusters, as it is almost impossible to clearly distinguish the stars in globular clusters with ground-based telescopes. The blurring caused by Earth’s atmosphere makes it impossible to tell one star from another, but from Hubble’s location in low Earth orbit the atmosphere no longer poses a problem. As a result, Hubble has been used to study what kind of stars globular clusters are made up of, how they evolve, and the role of gravity in these dense systems. The NASA/ESA/CSA James Webb Space Telescope will further our understanding of globular clusters by peering into those globular clusters that are currently obscured by dust. Webb will predominantly observe at infrared wavelengths, which are less affected by the gas and dust surrounding newborn stars. This will allow astronomers to inspect star clusters that are freshly formed, providing insights into stellar populations before they have a chance to evolve.

Why the same region of sky twice? (See other image in my photostream.) This one isn't even taken in total darkness (note dark blue background). Enlarge the image with the 'all sizes' button and you will see an interesting satellite track at the top of the frame. A slowly spinning satellite with reflective panels creates a dashed line across the image. I watched it spin about once every two seconds while the image was being taken.

Two faint constellations between Aquila and Cygnus. Sagitta is partly seen at the bottom and the upper part of the image takes in part of Vulpecula. At the upper left there is a greenish 'planetary' nebula (a dying star really) called M27, The Dumbell Nebula. At the bottom there is a distant globular cluster of stars (M71) which looks like a fuzzy patch. Taken with a Pentax K10D, 135mm f2.5 lens set to f4, ISO 400. Exposure around 3 minutes.

There's nothing special about my images, especially when compared to the amazing stuff other people create, except for a couple of things; I use a bog-standard 135mm lens and single exposures. No stacking, no expensive CCDs, no expensive filters, no big telescopes, no long journeys to remote dark places. So, anyone with a limited budget and limited time (the biggest factor I find) can do what I do.

M13, also designated NGC 6205 and sometimes called the Hercules Globular Cluster, or the Great Hercules Cluster, is a globular cluster of several hundred thousand stars in the constellation of Hercules.

Discovered by Edmond Halley in 1714, and often described by astronomers as the most magnificent globular cluster visible to northern observers. About 145 light-years in diameter, M13 is composed of several hundred thousand stars, with estimates varying from around 300,000 to over half a million. M13 is 22,200 to 25,000 light-years away from Earth, and the globular cluster is one of over one hundred that orbit the centre of the Milky Way.

LATEST VERSION: flic.kr/p/2oKjm3J

Messier 13 / M13 / NGC 6205 / The Great Globular Cluster in Hercules

NGC 6207

The Great Hercules Cluster is the brightest globular cluster in the northern sky and it contains about 300,000 stars. It is about 22,000 light-years away, orbiting the Milky Way, and it is estimated to be 11.65 billion years old. M13 is often compared to M3, another bright northern cluster: flic.kr/p/2oKdnJe

NGC 6207 is an edge-on spiral galaxy about 30 million light-years away. It is visible towards the lower left of M13.

Total integration: 15 hours 24 minutes (924 minutes)

04/02/20: 101 x 120 seconds ISO200

04/03/20: 129 x 120 seconds ISO200

04/09/20: 50 x 120 seconds ISO200

04/22/20: 66 x 120 seconds ISO200

05/02/20: 96 x 120 seconds ISO200

05/04/20: 6 x 120 seconds ISO200

05/12/20: 14 x 120 seconds ISO200

Location: Coral Springs, FL

SQM: 18.18 mag/arcsec^2 (Bortle 8/9)

Camera: Canon T3i (stock/unmodified)

Average camera temperature: 95 F (35 C)

Telescope: Explore Scientific ED80 f/6.0 Apochromatic Refractor (with ES field flattener)

Mount: Orion Sirius EQ-G

Guide scope: Svbony 50mm f/4.0 Guide Scope

Guide camera: Orion StarShoot AutoGuider

Software: N.I.N.A. with PlateSolve2 and PHD2

Pre-processed with PixInsight, processed with PixInsight and Paint.NET

M13 as seen in Menlo Park.

This is a collection of two nights of data taken with the Mak. I started with a stack of 50 lights and let DSS select the best 80% - leaving 40 lights to use. Was using the Pentax K10D with the cooler set to -10C - giving CCD temps of 15-16C. Ambient temps these evenings were about 15C so this effort neutralized the camera heat. Also, it was cool and damp enough to cause concerns for dew, so I used the dew heater at the lowest setting. Interestingly, this seems to help with the focus shift due to temperature.

I looked deeply at the darks that I'd captured earlier in the week and realized that they were also flawed with light leaks. Back to the drawing board for those files. Also, I looked at my efforts of using cold darks for bias to try to eliminate the amp glow. That's not so great, either, so I'm using my old bias files as well. Using these two major changes to the stacking set gave much smoother, lower noise back grounds.

It also helps that I'm dealing with an object that is mostly point source rather than extended, just the kind of target that the Mak will excel on with the high f ratio.

Once I brought the file into PI, I ran DBE, ACDNR (which gave some surprising results), masked stretch, curves, and a histogram stretch. I'd have liked to do more to drive the noise floor lower, but I think that most of what's remaining is because of the local light pollution.

Tracking for the night was problematic. I had the mount set to use .8x guide rate and I believe that this made it hard for Maxim to guide without oscillation. Thus, all the stars are elongated by about 1 pixel. Now that I think about it, I probably should have run that step to compact it a little. Drift was still not perfect - polar alignment is within 30arc seconds of true north.

I'm still testing, but so far this seems to work well. More trials are coming. I'm finding light leaks and stopping them when I can. I'm also working on the power budget. Letting everything run with the dew heaters, camera power, cooler, etc until sunup uses about 40-50 Amp Hours. This is 50-60% of the capacity of my battery and I don't like draining it that much. Recharge times take too long and I can't sustain that kind of dependence on daily recharges while at GSSP.

Here's the image resolving data from PI:

Image Plate Solver script version 1.51

============================

Referentiation Matrix (Gnomonic projection = Matrix * Coords[x,y]):

+0.000006205388 -0.000212175788 +0.245648531490

+0.000212053604 +0.000006270321 -0.408066179228

+0.000000000000 +0.000000000000 +1.000000000000

Resolution ........ 0.764 arcsec/pix

Rotation .......... 91.668 deg

Focal ............. 1458.00 mm

Pixel size ........ 5.40 um

Field of view ..... 48' 5.4" x 30' 53.3"

Image center ...... RA: 16 41 44.354 Dec: +36 25 45.93

Image bounds:

top-left ....... RA: 16 42 57.245 Dec: +36 01 15.52

top-right ...... RA: 16 43 05.027 Dec: +36 49 18.49

bottom-left .... RA: 16 40 24.493 Dec: +36 02 10.01

bottom-right ... RA: 16 40 30.693 Dec: +36 50 13.53

============================

This is a Hubble image of the globular cluster M 53, a ball of hundreds of thousands of stars orbiting the Milky Way galaxy.

Credit: ESA/Hubble & NASA

This colorful image of the globular star cluster Terzan 12 is a spectacular example of how dust in space affects starlight coming from background objects.

A globular star cluster is a conglomeration of stars, arranged in a spheroidal shape. Stars in globular clusters are bound together by gravity, with a higher concentration of stars towards the center. The Milky Way has about 150 ancient globular clusters at its outskirts. These clusters orbit around the galactic center, but far above and below the pancake-flat plane of our galaxy, like bees buzzing around a hive.

The location of this globular cluster, deep in the Milky Way in the constellation Sagittarius, means that it is shrouded in gas and dust which absorb and alter the starlight emanating from Terzan 12. The cluster is about 15,000 light-years from Earth. This location leaves a lot of room for intervening interstellar dust particles between us and the cluster to scatter blue light, causing only the redder wavelengths to come through to Earth. The interstellar dust clouds are mottled so that different parts of the cluster look redder than other parts along our line of sight.

The brightest red stars in the photo are bloated, aging giants, many times larger than our Sun. They lie between Earth and the cluster. Only a few may actually be members of the cluster. The very brightest hot, blue stars are also along the line of sight and not inside the cluster, which only contains aging stars.

Terzan 12 is one of 11 globular clusters discovered by the Turkish-Armenian astronomer Agop Terzan approximately a half-century ago. With its sharp vision, Hubble has revolutionized the study of globular clusters ever since its launch in 1990. Hubble observations have shed light on the relation between age and composition in the Milky Way galaxy's innermost globular clusters.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.

Image Credit: NASA, ESA, ESA/Hubble, Roger Cohen (RU)

For more information: www.nasa.gov/image-feature/goddard/2023/hubble-sees-glitt...

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Captured with my William Optics FLT91 + F6AIII reducer. ZWO ASI2600MC Pro with Optolong L-Pro 2" filter.

Basic post processing with Affinity Photo 2 to enhance contrast and crop it.

Acquisition details here: astrob.in/gi1ddn/0/

Equipment: Nikon D5300, Tamron SP 70-300mm f/4-5.6 Di VC USD lens, and iOptron Skytracker. Taken at 300mm, f/8.0, ISO 6400, 55 frames of 30 seconds each plus 60 darks. Stacked in Regim and cropped/processed in Lightroom.

Image of M13. Also in the image are galaxies NGC 6207 and IC 4617

Telescope: Celestron Ultima 8 with PEC and 6.3 focal reducer

Camera: Hutech modified Canon Rebel DSLR

Location: Long Island, NY

Exposure: 20x30 second images stacked. 20 dark frames subtracted.

ISO: 1600

Processed with MaxDSLR and Photoshop.

No guiding was used. I think my focus may has slipped a little before I took this image. I used a Bahtinov mask, to initially achieve focus, but after that I had to point the telescope to near the zenith, which may have caused the mirror to shift slightly.

The brightest globular cluster in the northern hemisphere. Experimental colour image taken with QHY22 camera on an autoguided 300mm F/4 Newtonian telescope. 30x30s exposures through Red, Green and Blue filters for a total of 90 exposures. Captured and processed in Nebulosity 3. Tweaked in StarTools.

Here is a Globular cluster NGC 104 known as 47 tuc, this can be found near the small Magellanic cloud, we used our Meade LX90 8-inch SCT and a ZwoASI120mc-s planetary camera, we had this set on a 10-second exposure this image is raw no processing involved.

DARK SKY PROJECT Photo taken by Igor Hoogerwerf - Location: University of Canterbury Mt John Observatory, Lake Tekapo, New Zealand. For some stunning Dark Sky Project time-lapse animations, please refer to Dark Sky Project on You Tube.

This globular cluster was the first one to be discovered by Charles Messier himself. It is now also designated as NGC 5272. This cluster is approximately 33.9k light years from us and is almost 334 light years in diameter.

Hubble picture of the cluster Terzan 5, which may be the tattered remnants of a dwarf galaxy eaten by the Milky Way. My blog post about it: blogs.discovermagazine.com/badastronomy/2011/05/23/specta...

Image credit:ESA/Hubble & NASA

M13 (also NGC6205) is the very first deep sky object I viewed with my Celestron Nexstar 8SE in April of 2014. It is a jewel of Hercules and one of the easiest objects to find, as it is located in the main body of the constellation. First noted by Edmond Halley in 1714, it is on the edge of naked eye visibility. The cluster containing hundreds of thousands of stars is approximately 145 light-years across at a distance of 22,200 light-years from Earth. In 1974, a message was sent from the Arecibo radio telescope to the cluster (en.wikipedia.org/wiki/Arecibo_message).

Nearby spiral galaxy NGC6207 in the bottom right of the image is located around 30 million light-years away. It was discovered by William Herschel on May 16, 1787.

In the top left are barely visible galaxies NGC6197, NGC6196, and IC4614.

Acquisition:

Imaged over 6 nights in February, March and May 2017 from Lake St Louis, MO

Integration: 8 hours (LRGB)

Luminance: 24x600s @ 1x1 (240')

R/G/B: 16/16/16 x 300s @ 2x2 (80'/80'/80')

Equipment:

Scope: William Optics GTF 81 5 element refractor (535mm focal length)

Upgraded with Moonlite CF focuser with motor

Imager: QHY9Ms with Olivon OAG and QHYCFW2-s filter wheel

Guidecam: ASI120MM

Filters: Baader LRGB

Mount: Orion Atlas EQ-G

Processing and Software

Guiding with PHD2

Acquisition with Sequence Generator Pro

Integration and processing with PixInsight 1.8

M13: flic.kr/p/XGbdxg

Annotated image: flic.kr/p/WEQWUB

Edited Hubble Space Telescope image of the globular cluster 47 Tucanae. White dwarf stars were found here that are migrating to the outskirts of the cluster. Ultraviolet version.

Original caption: Using NASA's Hubble Space Telescope, astronomers have captured for the first time snapshots of fledgling white dwarf stars beginning their slow-paced, 40-million-year migration from the crowded center of an ancient star cluster to the less populated suburbs.

White dwarfs are the burned-out relics of stars that rapidly lose mass, cool down, and shut off their nuclear furnaces. As these glowing carcasses age and shed weight, their orbits begin to expand outward from the star cluster's packed downtown. This migration is caused by a gravitational tussle among stars inside the cluster. Globular star clusters sort out stars according to their mass, governed by a gravitational billiard-ball game where lower mass stars rob momentum from more massive stars. The result is that heavier stars slow down and sink to the cluster’s core, while lighter stars pick up speed and move across the cluster to the edge. This process is known as "mass segregation." Until these Hubble observations, astronomers had never definitively seen the dynamical conveyor belt in action.

Astronomers used Hubble to watch the white-dwarf exodus in the globular star cluster 47 Tucanae, a dense swarm of hundreds of thousands of stars in our Milky Way galaxy. The cluster resides 16,700 light-years away in the southern constellation Tucana.

"We've seen the final picture before: white dwarfs that have already sorted themselves out and are orbiting in a location outside the core that is appropriate for their mass," explained Jeremy Heyl of the University of British Columbia (UBC), Vancouver, Canada, first author on the science paper. The team's results appeared in the May 1 issue of The Astrophysical Journal.

"But in this study, which comprises about a quarter of all the young white dwarfs in the cluster, we're actually catching the stars in the process of moving outward and segregating themselves according to mass," Heyl said. "The entire process doesn't take very long, only a few hundreds of millions of years, out of the 10-billion-year age of the cluster, for the white dwarfs to reach their new home in the outer suburbs."

"This result hasn't been seen before, and it challenges some ideas about some of the details of how and when a star loses its mass near the end of its life," added team member Harvey Richer of UBC.

Using the ultraviolet-light capabilities of Hubble's sharp-eyed Wide Field Camera 3, the astronomers examined 3,000 white dwarfs, tracing two populations with diverse ages and orbits. One grouping was 6 million years old and had just begun their journey. Another was around 100 million years old and had already arrived at its new homestead far away from the center, roughly 1.5 light-years, or nearly 9 trillion miles, away.

Only Hubble can detect these stars because ultraviolet light is blocked by Earth's atmosphere and therefore doesn't reach ground-based telescopes. The astronomers estimated the white dwarfs' ages by analyzing their colors, which gives them the stars' temperatures. The hottest dwarfs shine fiercely in ultraviolet light.

The dwarfs were tossed out of the rough-and-tumble cluster center due to gravitational interactions with heftier stars orbiting the region. Stars in globular clusters sort themselves out by weight, with the heavier stars sinking to the middle. Before flaming out as white dwarfs, the migrating stars were among the most massive in the cluster, weighing roughly as much as our Sun. The more massive stars burned out long ago.

The migrating white dwarfs, however, are not in a hurry to leave. Their orbits expand outward at about 30 miles an hour, roughly the average speed of a car traveling in the city. The dead stars will continue this pace for about 40 million years, until they reach a location that is more appropriate for their mass.

Although the astronomers were not surprised to see the migration, they were puzzled to find that the youngest white dwarfs were just embarking on their journey. This discovery may be evidence that the stars shed much of their mass at a later stage in their lives than once thought.

About 100 million years before stars evolve into white dwarfs, they swell up and become red giant stars. Many astronomers thought that stars lose most of their mass during this phase by blowing it off into space. But the Hubble observations reveal that the stars actually dump 40 percent to 50 percent of their bulk just 10 million years before completely burning out as white dwarfs.

"This late start is evidence that these white dwarfs are losing a large amount of mass just before they become white dwarfs and not during the earlier red giant phase, as most astronomers had thought," said Richer. "That's why we are seeing stars still in the process of moving slowly away from the center of the cluster. It's only after they lose their mass that they get gravitationally pushed out of the core. If the stars had shed most of their weight earlier in their lives, we wouldn't see such a dramatic effect between the youngest white dwarfs and the older ones that are 100 million years old."

Although the white dwarfs have exhausted the hydrogen fuel that makes them shine as stars, these stellar relics are among the brightest stars in this primordial cluster because their brilliant hot cores have been exposed, which are luminous largely in ultraviolet light. "When a white dwarf forms, they've got all this stored-up heat in their cores, and the reason we can see a white dwarf is because over time they radiate their stored thermal energy slowly into space," Richer explained. "They're getting cooler and less luminous as time goes on because they have no nuclear sources of energy."

After making it through the gauntlet of gravitational interactions within the crowded 1.5-light-year-wide core, the traveling white dwarfs encounter few interactions as they migrate outward, because the density of stars decreases. "A lot of action happens when they're 30 million to 40 million years old, and continues up to around 100 million years, and then as they get older the white dwarfs still evolve but less dramatically," Heyl said.

The 47 Tucanae cluster is an ideal place to study the mass segregation of white dwarfs because it is nearby and has a significant number of centrally concentrated stars that can be resolved by Hubble's crisp vision.

Edited Hubble Space Telescope image of the globular cluster 47 Tucanae. White dwarf stars were found here that are migrating to the outskirts of the cluster.

Original caption: Using NASA's Hubble Space Telescope, astronomers have captured for the first time snapshots of fledgling white dwarf stars beginning their slow-paced, 40-million-year migration from the crowded center of an ancient star cluster to the less populated suburbs.

White dwarfs are the burned-out relics of stars that rapidly lose mass, cool down, and shut off their nuclear furnaces. As these glowing carcasses age and shed weight, their orbits begin to expand outward from the star cluster's packed downtown. This migration is caused by a gravitational tussle among stars inside the cluster. Globular star clusters sort out stars according to their mass, governed by a gravitational billiard-ball game where lower mass stars rob momentum from more massive stars. The result is that heavier stars slow down and sink to the cluster’s core, while lighter stars pick up speed and move across the cluster to the edge. This process is known as "mass segregation." Until these Hubble observations, astronomers had never definitively seen the dynamical conveyor belt in action.

Astronomers used Hubble to watch the white-dwarf exodus in the globular star cluster 47 Tucanae, a dense swarm of hundreds of thousands of stars in our Milky Way galaxy. The cluster resides 16,700 light-years away in the southern constellation Tucana.

"We've seen the final picture before: white dwarfs that have already sorted themselves out and are orbiting in a location outside the core that is appropriate for their mass," explained Jeremy Heyl of the University of British Columbia (UBC), Vancouver, Canada, first author on the science paper. The team's results appeared in the May 1 issue of The Astrophysical Journal.

"But in this study, which comprises about a quarter of all the young white dwarfs in the cluster, we're actually catching the stars in the process of moving outward and segregating themselves according to mass," Heyl said. "The entire process doesn't take very long, only a few hundreds of millions of years, out of the 10-billion-year age of the cluster, for the white dwarfs to reach their new home in the outer suburbs."

"This result hasn't been seen before, and it challenges some ideas about some of the details of how and when a star loses its mass near the end of its life," added team member Harvey Richer of UBC.

Using the ultraviolet-light capabilities of Hubble's sharp-eyed Wide Field Camera 3, the astronomers examined 3,000 white dwarfs, tracing two populations with diverse ages and orbits. One grouping was 6 million years old and had just begun their journey. Another was around 100 million years old and had already arrived at its new homestead far away from the center, roughly 1.5 light-years, or nearly 9 trillion miles, away.

Only Hubble can detect these stars because ultraviolet light is blocked by Earth's atmosphere and therefore doesn't reach ground-based telescopes. The astronomers estimated the white dwarfs' ages by analyzing their colors, which gives them the stars' temperatures. The hottest dwarfs shine fiercely in ultraviolet light.

The dwarfs were tossed out of the rough-and-tumble cluster center due to gravitational interactions with heftier stars orbiting the region. Stars in globular clusters sort themselves out by weight, with the heavier stars sinking to the middle. Before flaming out as white dwarfs, the migrating stars were among the most massive in the cluster, weighing roughly as much as our Sun. The more massive stars burned out long ago.

The migrating white dwarfs, however, are not in a hurry to leave. Their orbits expand outward at about 30 miles an hour, roughly the average speed of a car traveling in the city. The dead stars will continue this pace for about 40 million years, until they reach a location that is more appropriate for their mass.

Although the astronomers were not surprised to see the migration, they were puzzled to find that the youngest white dwarfs were just embarking on their journey. This discovery may be evidence that the stars shed much of their mass at a later stage in their lives than once thought.

About 100 million years before stars evolve into white dwarfs, they swell up and become red giant stars. Many astronomers thought that stars lose most of their mass during this phase by blowing it off into space. But the Hubble observations reveal that the stars actually dump 40 percent to 50 percent of their bulk just 10 million years before completely burning out as white dwarfs.

"This late start is evidence that these white dwarfs are losing a large amount of mass just before they become white dwarfs and not during the earlier red giant phase, as most astronomers had thought," said Richer. "That's why we are seeing stars still in the process of moving slowly away from the center of the cluster. It's only after they lose their mass that they get gravitationally pushed out of the core. If the stars had shed most of their weight earlier in their lives, we wouldn't see such a dramatic effect between the youngest white dwarfs and the older ones that are 100 million years old."

Although the white dwarfs have exhausted the hydrogen fuel that makes them shine as stars, these stellar relics are among the brightest stars in this primordial cluster because their brilliant hot cores have been exposed, which are luminous largely in ultraviolet light. "When a white dwarf forms, they've got all this stored-up heat in their cores, and the reason we can see a white dwarf is because over time they radiate their stored thermal energy slowly into space," Richer explained. "They're getting cooler and less luminous as time goes on because they have no nuclear sources of energy."

After making it through the gauntlet of gravitational interactions within the crowded 1.5-light-year-wide core, the traveling white dwarfs encounter few interactions as they migrate outward, because the density of stars decreases. "A lot of action happens when they're 30 million to 40 million years old, and continues up to around 100 million years, and then as they get older the white dwarfs still evolve but less dramatically," Heyl said.

The 47 Tucanae cluster is an ideal place to study the mass segregation of white dwarfs because it is nearby and has a significant number of centrally concentrated stars that can be resolved by Hubble's crisp vision.

Edited montage (created by NASA) of Hubble Space Telescope images of the globular cluster NGC 6752 and a dwarf galaxy hiding behind it. Color/processing variant.

Original caption: The universe is very cluttered. Myriad island cities of stars, the galaxies, form a backdrop tapestry. Much closer to home are nebulae, star clusters, and assorted other foreground celestial objects that are mostly within our Milky Way galaxy. Despite the vastness of space, objects tend to get in front of each other.This happened when astronomers used the Hubble Space Telescope to photograph the globular star cluster NGC 6752 (located 13,000 light-years away in our Milky Way's halo). In a celestial game of "Where's Waldo?", Hubble's sharp vision uncovered a never-before-seen dwarf galaxy located far behind the cluster's crowded stellar population. The loner galaxy is in our own cosmic backyard, only 30 million light-years away (approximately 2,300 times farther than the foreground cluster).The object is classified as a dwarf spheroidal galaxy because it measures only around 3,000 light-years at its greatest extent (barely 1/30th the diameter of the Milky Way), and it is roughly a thousand times dimmer than the Milky Way.Because of its 13-billion-year-old age, and its isolation - which resulted in hardly any interaction with other galaxies - the dwarf is the astronomical equivalent of a living fossil from the early universe.

Image of M4

Telescope: Celestron Ultima 8 with PEC and 6.3 focal reducer

Camera: Hutech modified Canon Rebel DSLR

Location: Long Island, NY

Exposure: 21x30 second images stacked. 20 dark frames subtracted.

ISO: 1600

Processed with MaxDSLR and Photoshop.

No guiding was used.

Salut à tous,

Voici la deuxième photo de cette formidable nuit du 22-23.

"Pegasus Cluster"

Nous ciblons M15, un amas globulaire situé à environ 35 000 années lumière de nous (le voyage est long).

La particularité de cette capture réside dans la présence d'IFN (Integrated Flux Nebulae) proches de notre cible.

Ce sont en quelque sorte des nébuleuses qui ne sont ni des nuages ionisés (nébuleuse en émission) ni des nuages éclairés par une ou plusieurs étoiles (nébuleuse en réflexion) mais de vaste nuages éclairés par la lueur globale de notre galaxie.

Ils font sans doute partie des objets les plus difficiles à capturer !

En effet, la qualité du ciel, l'absence de lune et un instrument rapide sont ici recommandés.

Objets notables :

IFN

M15

NGC7068

Informations :

Lieu / date : La Fosse (Manhay, Belgique) - 22/08/2023

Constellation : Pégase

Acquisition : 55 x 90 sec (01h22.5)

Monture : Skywatcher EQ6R pro

Tube optique : Celestron RASA 8

Caméra : ZWO Asi2600MC (gain 100 / -10°)

Filtre : Aucun

Accessoires : ZWO EAF - ZWO ASIAIR PRO

Traitement : Siril - Pixinsight - Lightroom

Haute résolution : www.astrobin.com/full/995z3u/0/

Bon ciel à tous

Messier 3 is a bright globular cluster that passes nearly directly overhead for observers in the mid-northern latitudes during the spring of each year. This is a small-scale, widefield view covering several degrees of the sky around the cluster. Extremely sharp eyed individuals may be able to pick out the 13.4 magnitude galaxy NGC 5263 that appears immediately above the cluster and about one half way to the top edge of the photo (warning, it's small and faint and you may not be able to see if except in the large, full-sized version of the image).

Photographed on the evening of April 28, 2014 using an Astro-Tech AT65EDQ telescope and a Sony NEX-5N digital camera (ISO 800, a stack of 16 images that were each exposed for 30 seconds, producing a total exposure integration time of 8 minutes). There were no dark, bias, or flat frames and this is just a quick draft before I work on the full set of data that should produce almost two hours of integrated exposure time (over ten times the exposure that was used here).

This image is best seen at full size or against a dark background.

All rights reserved.

Mars is getting smaller every night and the seeing wasn't very good, so I did some deep sky imaging instead of doing planetary stuff. This time of year bring warmer nights, but it sure is late when the sky is truly dark.

Anyway, this is Messier 3, one of the three finest globulars in the Northern sky. M3 is 34 kly away and it is about 180 ly across. It contains about a half million stars.

After processing this image I noticed that M3 contains a lot of blue stars, which is peculiar - globulars are old and generally have geriatric, yellow stars. After a bit of research I found that these blue stars were equally puzzling to professional astronomers, who eventually came up with the theory that these stars were originally yellow, but had their outer layers stripped away when they passed through the centre of the cluster.

Discovered by Johann Elert Bode in 1777, this 6th magnitude globular cluster in Hercules is naked eye visible in very dark skies. Messier 92 is located about 26,700 light-years from earth. Extremely old, the cluster exhibits very low metallicity, containing mostly Hydrogen and Helium and is located above the plane of our Milky Way.

There is a nice chain of small galaxies towards the bottom left of the image. NGCs 6323, 6329, 6332 and 6336 all resolved fairly nicely in the field for such a small telescope. I am particularly fond of the structure of NGC6332 and NGC6336. There is a nice article about this chain in a 2006 version of S&T (www.skyandtelescope.com/observing/celestial-objects-to-wa...).

As always, I welcome any suggestions or comments and hope you all enjoy the image!

Acquisition:

Imaged over 6 nights in May & June 2017 from Lake St Louis, MO

Integration: 8 hours (LRGB)

Luminance: 24x600s @ 1x1 (240')

R/G/B: 16/16/16 x 300s @ 1x1 (80'/80'/80')

Equipment:

Scope: William Optics GTF 81 5 element refractor (535mm focal length)

Upgraded with Moonlite CF focuser with motor

Imager: QHY9Ms with Olivon OAG and QHYCFW2-s filter wheel

Guidecam: ASI120MM

Filters: Baader LRGB

Mount: Orion Atlas EQ-G

Processing and Software

Guiding with PHD2

Acquisition using Sequence Generator Pro

Integration and processing with PixInsight 1.8

M92 & Friends: flic.kr/p/23K47Km

Annotated Image: flic.kr/p/23MXq3R

I previously imaged M92 in 2015 with an 8" SCT and DSLR: flic.kr/p/wqUrxp

Imaging scope: AstroProfessional 102mm refractor (focal 714mm) with reducer 0.8x

Imaging camera: Atik 314L+ (-15°c)

Imaging software : Artemis capture

Mount: EQ6 Pro autoguided

Guide scope: Takahashi FS60

Guide camera: DMK31 B&W

Guide software: PHD Guiding

Luminance : 30 x 2 min (Astrodon filter), binning 1x1

RGB : 10 x 2 min each layer (Astrodon filter), binning 1x1

Processing with Iris: pre-processing (15 offsets, 9 darks, 11 flats for each filter), global register, arithmetic addition, DDP, black, saturation

Location: Saint-Etienne-les-Orgues (Alpes de Haute Provence - FRANCE)

SQM : 21.2 mag/arcsec²

A fantastic sight in just about any scope, and an amazing object to image. M13 is about 25,000 light-years away, and was the chosen destination for a "Hello, there" message transmitted into space from the Arecibo Radio Telescope in 1974. We might know in 50,000 years whether or not anyone got it.

NGC6726, NGC6727, NGC6729 and more. A widefield view nebula in Corona Australis, the Southern Crown.

Taken with a Takahashi FS60C and QHY-8, colour camera.

Taken with TMB 130/1200 with 0.6x reducer. The cluster was not well placed in the sky with a fair amount of light pollution in that area, despite that it turned out fairly well. The reducer turns an f9.23 scope into an f5.5 scope, which is considerably faster for imaging. There is distortion at the corners, but cropping took care of that. Stack of 116 frames in total.

M13 - Globular Star Cluster in Hercules. 38 images x 60sec. Asi 533 mc camera with an Orion Astrograph 8 inch Newtonian

COMET LEONARD: WIDE ANGLE (2021-12-03)

Shot between 09:55 and 13:27 UTC, in Pinnacles National Park, California, USA. Me and my partner in crime climbed up to the Bear Gulch Reservoir, scouted a nice and secluded spot before the sunset and returned back in the night (it wasn't the best idea to go through those places in the dark, one needs to be very and very cautious in doing so!). I decided to go lightweight and not take my tracker with me that night, as the weather forecast was looking rather iffy (it turned out to be way better closer to the time when the comet started rising above the horizon, but hey, quite often these predictions resemble gambling, lol). While my Nikon D610 and 15mm f/2.4 lens were shooting generic wide angle timelapses, for the comet I went with my ZWO ASI533MC and Rokinon 16mm f/2 lens. It was yet another gamble, as I wasn't sure how impressive it will look at a such a short focal length (spoiler - not much, but better than nothing!). We were able to find and observe it using binoculars, which was cool, our first encounter with the comet! Luckily, framing was correct, which is why there is a segment before the appearance of the comet (I've started shooting way ahead of time, to see how the setup behaves). What I do like in the timelapse - beside the movement of stars across the sky, we can also can notice the movement of the comet across the star field (fun fact - the bright "star" right above the comet is actually the globular cluster M3)!

Technical Details:

SIRUI tripod

ZWO ASI533MC Pro (gain 100, temperature -10C, 10 seconds exposure)

ZWO EF lens adapter

Rokinon 16mm f/2 lens (fully open)

INDI server (ASI + GPS drivers)

Custom script to handle timelapse shooting (KStars prone to random crashes)

Siril for pre-processing (flats + darks), debayering, MTF, SCNR and TIFF export (last 2 operations through a custom script)

Sequator in timelapse mode (29 frames per stack, with foreground masking)

RawTherapee for post-processing tweaks

Luminance HDR for tone-mapping (helped bringing up the foreground)

Enfuse to merge the previous 2 results

Custom script for preliminary extraction of the comet zoom-in view

Siril to align the results above

RawTherapee for post-processing tweaks

ImageMagick for overlaying the comet zoom-in

ffmpeg to create the timelapse video

YouTube Audiolibrary for the soundtrack

MKVToolNix for adding soundtrack

FAQ:

- Where are the planes, satellites and meteors?

- Removed by the stacking, nice side-effect, I hate the airplanes flying in my frames!

- Why foreground is so static? Was it masked in?

- Again stacking is the answer here, completely nullified the movement caused by the wind

- What are those ghostly things moving across the sky at the start of the video?

- Clouds. Yet again stacking had an impact here, creating a strong blurring effect

- Where is the color, beside the green coma of the comet?

- It has been mostly killed off in the post-processing, to hide all the ugly artifacts. Not happy about it, but didn't have much choice (and skill)

- What is the soundtrack?

- Piano March by Audionautix is licensed under a Creative Commons Attribution 4.0 license.

M3, NGC5272 in Canes Venatici, one of the largest and brightest globular clusters, made up of around 500,000 stars. It is estimated to be 8 billion years old. It is located at a distance of about 33,900 LY

M13 as seen in Menlo Park.

This is a collection of two nights of data taken with the Mak. I started with a stack of 50 lights and let DSS select the best 80% - leaving 40 lights to use. Was using the Pentax K10D with the cooler set to -10C - giving CCD temps of 15-16C. Ambient temps these evenings were about 15C so this effort neutralized the camera heat. Also, it was cool and damp enough to cause concerns for dew, so I used the dew heater at the lowest setting. Interestingly, this seems to help with the focus shift due to temperature.

I looked deeply at the darks that I'd captured earlier in the week and realized that they were also flawed with light leaks. Back to the drawing board for those files. Also, I looked at my efforts of using cold darks for bias to try to eliminate the amp glow. That's not so great, either, so I'm using my old bias files as well. Using these two major changes to the stacking set gave much smoother, lower noise back grounds.

It also helps that I'm dealing with an object that is mostly point source rather than extended, just the kind of target that the Mak will excel on with the high f ratio.

Once I brought the file into PI, I ran DBE, ACDNR (which gave some surprising results), masked stretch, curves, and a histogram stretch. I'd have liked to do more to drive the noise floor lower, but I think that most of what's remaining is because of the local light pollution.

Tracking for the night was problematic. I had the mount set to use .8x guide rate and I believe that this made it hard for Maxim to guide without oscillation. Thus, all the stars are elongated by about 1 pixel. Now that I think about it, I probably should have run that step to compact it a little. Drift was still not perfect - polar alignment is within 30arc seconds of true north.

I'm still testing, but so far this seems to work well. More trials are coming. I'm finding light leaks and stopping them when I can. I'm also working on the power budget. Letting everything run with the dew heaters, camera power, cooler, etc until sunup uses about 40-50 Amp Hours. This is 50-60% of the capacity of my battery and I don't like draining it that much. Recharge times take too long and I can't sustain that kind of dependence on daily recharges while at GSSP.

Here's the image resolving data from PI:

Image Plate Solver script version 1.51

============================

Referentiation Matrix (Gnomonic projection = Matrix * Coords[x,y]):

+0.000006205388 -0.000212175788 +0.245648531490

+0.000212053604 +0.000006270321 -0.408066179228

+0.000000000000 +0.000000000000 +1.000000000000

Resolution ........ 0.764 arcsec/pix

Rotation .......... 91.668 deg

Focal ............. 1458.00 mm

Pixel size ........ 5.40 um

Field of view ..... 48' 5.4" x 30' 53.3"

Image center ...... RA: 16 41 44.354 Dec: +36 25 45.93

Image bounds:

top-left ....... RA: 16 42 57.245 Dec: +36 01 15.52

top-right ...... RA: 16 43 05.027 Dec: +36 49 18.49

bottom-left .... RA: 16 40 24.493 Dec: +36 02 10.01

bottom-right ... RA: 16 40 30.693 Dec: +36 50 13.53

============================

NGC 7006 is a globular cluster about 135,000 light years away.

Credit: ESA/Hubble & NASA

Arguably the most spectacular global star cluster on the northern hemisphere.

Full capture data available at www.astrobin.com/lyxfor/

The scattered stars of the globular cluster NGC 6355 are strewn across this image from the Hubble Space Telescope. NGC 6355 is a galactic globular cluster that resides in our Milky Way galaxy's inner regions. It is less than 50,000 light-years from Earth in the constellation Ophiuchus.

Globular clusters are stable, tightly bound groups of tens of thousands to millions of stars that are associated with all types of galaxies. Their dense populations of stars and mutual gravitational attraction give these clusters a roughly spherical shape that holds a bright, central concentration of stars surrounded by an increasingly sparse sprinkling of stars. The dense, bright core of NGC 6355 shines in crystal-clear detail as Hubble is able to resolve individual stars in the crowded area toward the center of this image.

Hubble has revolutionized the study of globular clusters. It is almost impossible to distinguish individual stars in globular clusters with ground-based telescopes. Hubble’s unique capabilities and vantage point above Earth’s light-distorting atmosphere allow it to capture a globular cluster’s constituent stars in detail.

Credit: ESA/Hubble & NASA, E. Noyola, R. Cohen

For more information, visit: science.nasa.gov/centers-and-facilities/goddard/hubble-ga...

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I figured I would put M92 in the corner of this shot to see how many of the galaxies in the adjacent regions of the sky I could get from my light polluted backyard.

I did not expect a result like this from a stack of 20 3m30s exposures. I will post the non-annotated version later.

M54 is a globular cluster that's actually located in the core of another galaxy!

Edited Hubble Space Telescope image of the globular cluster NGC 1466 in one of the Milky Way's satellite galaxies, the Large Magellanic Cloud. Color/processing variant.

Original caption: This image from the NASA/ESA Hubble Space Telescope reveals an ancient, glimmering ball of stars called NGC 1466. It is a globular cluster — a gathering of stars all held together by gravity — that is slowly moving through space on the outskirts of the Large Magellanic Cloud, one of our closest galactic neighbours. NGC 1466 certainly is one for extremes. It has a mass equivalent to roughly 140 000 Suns and an age of around 13.1 billion years, making it almost as old as the Universe itself. This fossil-like relic from the early Universe lies some 160 000 light-years away from us. Nestled within this ancient time capsule are 49 known RR Lyrae variable stars, which are indispensable tools for measuring distances in the Universe. These variable stars have well-defined luminosities, meaning that astronomers know the total amount of energy they emit. By comparing this known luminosity to how bright the stars appear in the sky, their distance can be easily calculated. Astronomical objects such as this are known as standard candles, and are fundamental to the so-called cosmic distance ladder.

Single frame

10 seconds

1600 iso

Celestron C8 f/10 2000mm focal length

Canon EOS 1100d

Processed in Iris:

deconvolved to correct tracking errors

correct colour balance

gaussian noise reduction

reduced colour saturation

Image of a globular star cluster. This image was taken with Kodak 3200 color print film which increased film grain but allowed for a much shorter exposure.

Discovered by Johann Elert Bode in 1777, this 6th magnitude globular cluster in Hercules is naked eye visible in very dark skies. Messier 92 is located about 26,700 light-years from earth. Extremely old, the cluster exhibits very low metallicity, containing mostly Hydrogen and Helium and is located above the plane of our Milky Way.

There is a nice chain of small galaxies towards the bottom left of the image. NGCs 6323, 6329, 6332 and 6336 all resolved fairly nicely in the field for such a small telescope. I am particularly fond of the structure of NGC6332 and NGC6336. There is a nice article about this chain in a 2006 version of S&T (www.skyandtelescope.com/observing/celestial-objects-to-wa...).

As always, I welcome any suggestions or comments and hope you all enjoy the image!

Acquisition:

Imaged over 6 nights in May & June 2017 from Lake St Louis, MO

Integration: 8 hours (LRGB)

Luminance: 24x600s @ 1x1 (240')

R/G/B: 16/16/16 x 300s @ 1x1 (80'/80'/80')

Equipment:

Scope: William Optics GTF 81 5 element refractor (535mm focal length)

Upgraded with Moonlite CF focuser with motor

Imager: QHY9Ms with Olivon OAG and QHYCFW2-s filter wheel

Guidecam: ASI120MM

Filters: Baader LRGB

Mount: Orion Atlas EQ-G

Processing and Software

Guiding with PHD2

Acquisition using Sequence Generator Pro

Integration and processing with PixInsight 1.8

M92 & Friends: flic.kr/p/23K47Km

Annotated Image: flic.kr/p/23MXq3R