I'd been eyeing this area in Camelopardalis for awhile because of the concentration of dark nebulae. Barnards 8-13 are the dark nebulae on the lower left.

It was a bit of a let down to process - It's not nearly as neat as the the dark nebulae in Taurus or Cepheus, in my opinion, but it was fun to explore anyway. I almost didn't post it because it's a bit underwhelming, but since there aren't too many images of this area, I decided to post anyway.

Fujifilm X-T10, Samyang 135mm f/2.0 ED UMC @ f2.0, ISO 1600, 50 x 60 sec, tracking with iOptron SkyTracker Pro, stacking with DeepSkyStacker, editing with Astro Pixel Processor and GIMP, taken on Nov. 24, 2019 under Bortle 3/4 skies.

Equipment

Imaging Telescopes Or Lenses

TS-Optics 6" f/4 UNC Newtonian Telescope - Carbon

Imaging Cameras

ZWO ASI 183 MM PRO

Mounts

Sky-Watcher NEQ6-Pro

Filters

Baader B 1.25'' CCD Filter · Baader G 1.25'' CCD Filter · Baader R 1.25'' CCD Filter · Baader L 1.25'' Filter

Accessories

ZWO EAF Electronic Auto Focuser · TSOptics TS Off Axis Guider - 9mm · Pal Gyulai GPU Aplanatic Koma Korrector 4-element

Software

Luc Coiffier DeepSkyStacker (DSS) · PHD2 Guiding · PhotoShop CS5 · FitsWork 4 · CCDCiel

Guiding Telescopes Or Lenses

TS-Optics 6" f/4 UNC Newtonian Telescope - Carbon

Guiding Cameras

Astrolumina Alccd5L-IIc

Acquisition details

Dates:

April 4, 2021

Frames:

Baader B 1.25'' CCD Filter: 17x180" (51') (gain: 53.00) -20°C bin 1x1

Baader G 1.25'' CCD Filter: 17x180" (51') (gain: 53.00) -20°C bin 1x1

Baader L 1.25'' Filter: 35x180" (1h 45') (gain: 53.00) -20°C bin 1x1

Baader R 1.25'' CCD Filter: 17x180" (51') (gain: 53.00) -20°C bin 1x1

Integration:

4h 18'

Canon 135mm f/2 lens (stopped down to 2.8) attached to SX Trius 694 via a Geoptik adapter with internal 7nm Ha filter,piggybacked to main scope on CEM60 mount.

Each image comprises of 12 x 300sec subs stacked in Deepskystacker,mosaic created and processed in Photoshop CS2.

Taken 05/01/22

20 superimposed images with DeepSkyStacker

50 mm

f/1.8

ISO 1600

13 x 20 seconds

(JPEG editing only)

Location : France

Just starting to learn things in astrophotography of course with the help and support of GeoAstro team ^_^

27 frames were shot with Nikon D5100, 200mm lens f/2.8, ISO 3200, Exp. 30"

Processed in Deepskystacker and retouched in Photoshop cs6.

Part of the famous Veil Nebula supernova remnant. The bright star with the reflection halo is 52 Cygni.

Unfortunately, this has the frequent problem I get with bloated stars towards the lower right. Not got to the bottom of it yet, but something in the optical chain must be getting out of alignment. I do check collimation before each session. Anyway, I was pleased with the detail in the nebula, so have posted despite the flaws.

Manually, off-axis guided for 11 x 4-minute exposures at ISO 1600, f/4. Modified EOS 600D & Revelation 12" Newtonian reflector telescope.

Registered and stacked using DeepSkyStacker; initial curves adjusted in Canon Photo Professional; final curves & colour-balance adjusted using Paint Shop Pro; noise reduction via CyberLink PhotoDirector.

35 x 8 minutes, ISO 400

30 darks, 100 flats, 100 bias

Equipment: Canon 450D (full spectrum mod), Orion 8" f/3.9 Newtonian Astrograph, Orion Atlas EQ-G, Orion SSAG/80mm, Baader MPCC

Acquisition: EQMOD, Cartes du Ciel, Backyard EOS, Astrotortilla, PHD

Calibration and Post-processing in DeepSkyStacker and Pixinsight

After weeks of cloudy skies, I finally had the opportunity at grabbing a couple of shots of Lovejoy on it's passage past us towards the Sun.

Used 7 x exposures at 100mm, via Deepskystacker, which has removed the green tint from the Comet that shows up single exposures - obviously I need to do some reading up on the Software :)

6sec exposures, ISO5000 at f/2.8 - cropped down to 50%

Guess who got an ED80 for his birthday then? :)

This is my first half successful attempt at using the thing with my new go-faster budget guiding kit :) Guiding was fine, but I ran out of vis towards the end, and as the Reading Fest had just kicked off, I had to contend with searchlights passing through the frame every 20 seconds or so! So on that basis, this ain't too bad - even though it needed a little encouragement during the processing :) Horrendously noisy, hence the small image :)

SW ED80/EQ5

Nikon D70 modded, iso 1250, Baader Neodymium filter

15 x 6 mins for a total of 1 hour 30 minutes

Guiding: Quickcam Pro4000/9x50 finderscope, PHD

Stacked in DSS and processed in CS5

Taken using Olympus E-P5 with Panasonic 14mm f/2.5 lens at f/4.

Stack of 52x 13 second exposures at ISO3200, 11 mins total exposure.

Stacked in DeepSkyStacker, edited heavily in Photoshop to bring out the Galaxy.

46 x 30sec images

My first foray into using a dedicated astro camera.

Images were taken on the first opportunity of a cloud free night (or close to it) but there was however, a full moon.

I suspect the full moon took away some of the finer details and the blues/purples. Time will tell.

These image files (FITS) were stacked with DeepSkyStacker and then edited in Adobe Photoshop.

Gear used:

ZWO ASI Air Pro

ZWO ASI294

Skywatcher EQ6r

ZWO ASI290 guide camera

William Optics Redcat 51

Latitude:

42deg South

My first attempt to capture Horse Head nebula.

Too much light pollution to capture as expected.

Canon 500D

Sigma 120-400 @120mm

f 6.3

ISO 800

35 frames x 120 seconds

58 frames x 60 seconds

total exposure about 128 minutes

60 darks

61 bias

45 flats

After I have spent hours to watch the starry sky, I tried to realize a image of our nearest neighbor galaxy : Andromeda M31.

Wihtout using a tracking mount, I took 64 images (+ 20 darks) that I superimposed with DeepSkyStacker software.

In order to improve the clarity of the photograph, I used lightroom. But the focus is not perfect unfortunately...

Tehnical datas :

Canon T3i on tripod

50 mm lens

f/1.8

64 x 8 s = 8.5 minutes of exposure

ISO3200

JPEG editing

Taken with a TMB92L, Canon T3i DSLR, and Celestron CG-4 mount. Consists of 41 light and 23 dark frames, each a 35-second exposure at ISO 800, stacked in DeepSkyStacker and processed in Photoshop.

[English]

The Orion Nebula, also known as Messier 42, M42, or NGC 1976, is a diffuse nebula situated south of Orion's Belt in the constellation of Orion. It is one of the brightest nebulae, and is visible to the naked eye in the night sky. M42 is located at a distance of 1,344 ± 20 light years and is the closest region of massive star formation to Earth. The M42 nebula is estimated to be 24 light years across. It has a mass of about 2000 times the mass of the Sun.

Nikon D90 - Meade LX200 10" - f/6.3 - 1600mm - ISO 800 - 14 minutes of total exposure - 42 frames of 20 seconds, stacked with DeepSkyStacker. Tweaked with Adobe Photoshop CC.

Information taken from en.wikipedia.org/wiki/Orion_Nebula

[Español]

La nebulosa de Orión, también conocida como Messier 42, M42, o NGC 1976, es una nebulosa difusa situada al sur del Cinturón de Orión. Es una de las nebulosas más brillantes que existen, y puede ser observada a simple vista sobre el cielo nocturno. Está situada a 1.270±76 años luz de la Tierra, y posee un diámetro aproximado de 24 años luz.

Nikon D90 - Meade LX200 10" - f/6.3 - 1600mm - ISO 800 - 14 minutos de exposición - 42 fotos de 20 segundos, apiladas con DeepSkyStacker. Postprocesado con Adobe Photoshop CC.

Imagen recortada de la original.

Info de Wikipedia (es.wikipedia.org/wiki/Nebulosa_de_Ori%C3%B3n)

This is now 275 subs over 8 sessions totalling 17 hours, and is slowly getting there. Still needs more time, but I suspect it will have to wait until next year now. Used a different processing technique to my previous sad looking version, and it seems to have done the trick. Got Hubble's Variable thingy in there this time as well :)

I won't be sorry to see the back of this :)

SW ED80/EQ5

Nikon D70 modded, Baader Neodymium filter

275 subs, 3-6 mins, iso 800-1600, total 17 hours

Guiding (RA only): Quickcam Pro4000/9x50 finderscope, PHD

Stacked in DSS and processed in CS5. Spikes courtesy of Star Spikes Pro

The Pleiades M45, shot from a dark location in the Black Forrest at almost 1000 m. It was taken on December 3rd in a clear and moonless night.

This was the first field use of my Celestron AVX mount and my new guiding setup.

Camera: Canon EOS 600D, modified

Lens: Canon EF 200 L 2.8 @ f/4 with aperture stopper (I don’t like spikes)

Mount: Celestron AVX

Guiding: ALccd5L-IIc with PHD

Shot Info: 16 x 600 s, ISO 800, total time 160 minutes, 20 bias, no darks, no flats

Software: Astro Photography Tool for Imaging, DeepSkyStacker and PixInsight

Meade LXD75 N6 unguided, SW LPF

11X Lights (120s ISO 1600)

8X Bias

5X Darks

5X Flats

Skywatcher Esprit 100mm triplet APO and Canon 6D full spectrum with Astronomik L (IR/UV cut) XL clip filter 40x180sec at iso1600. Stacked with Deepskystacker and processed with Pixinsight 1.8. Image dates 21 and 22 july 2015.

Press L (followed by F11) for the best view.

M-51 Whirlpool Galaxy

C-11 @ F/2 Hyperstar CGEM-DX on Pier

23 subs 60 sec iso1600 unguided

0 flats, 0 darks, 0 bias

Total integration 0 hours 23 minutes.

Canon 6D Baader Mod – by Hap Griffin.

Filter - LPS2

seeing - average

5th time on target.

Stacked in Deepskystacker

Had a session on this last night, and combined with last year's effort for a total of 2 hrs 23 mins.

Not sure that I've gained much, although a little less noisy in the wispy bits, and a couple of fuzzies visible. Don't think I'll get much more out of this target without a serious upgrade of kit! :)

SW 200p, EQ5 unguided

Nikon D70 modded, iso1600, Baader MPCC and Neodymiun filter

142 x 60sec

darks, bias and flats.

Stacked in DSS and processed in CS5

Eskimo Nebula or Clown Face Nebula.

Not my best attempt as I went a little too long with the exposures I think, but still not my worst .

NGC 2392 can be found in the constellation of Gemini about 5,000 light years away.

First spotted by William Herschel in 1787. It's thought that this planetary nebula started to form around 10,000 years ago.

Planetary nebulae are formed from dying stars that have burnt through all their fuel supplies and start shedding off outer layers in to space.

Boring techie bit.

Skywatcher quattro 8" S & f4 aplanatic coma corrector

EQ6 R pro mount guided with an Altair 50mm & Altair GPcam

Canon 450D astro modded with Astronomik CLS CCD EOS APS-C clip filter. Neewer Intervalometer used to control the exposures.

60 exposures of 120 seconds each with the best 75% stacked together with calibration frames.

Software used, PHd2, DeepSkyStacker, StarTools.

2 Panes - Total 4hrs

Red/Blue 12x300sec each pane

Stacked in DeepSkyStacker, processed in PS2 (Synth Green).

Camera: Atik 314L+ Mono

Filters: Baader Red & Blue.

Scope: Sky-Watcher Equinox 80ED .

Mount: AZ EQ6-GT goto, PhD guided with Orion 50mm guidescope with SSAG.

El equipo empleado fue...

Telescopio: ED80 Sky Watcher

Montura: LXD75 Meade

Cámara: QHY163m

Guiado: MiniScope 50mm Orion, CámaraGuia/QHY5 L-II c

Adquisición: APT (AstroPhotographyTool)

Apilado y procesado: DeepSkyStacker, PixInsight, Photoshop

Tomas

L: 6x600s

Expo Total: 1h

Temperatura sensor: -10°C

Distancia Focal: 600mm

F/ 7,5

celfoscastrofotografia.blogspot.com/2018/08/noche-de-pers...

The North America nebula and surrounding area in the constellation Cygnus.

28 x 4min @ ISO 1600 & f/4

Stacked with DeepSkyStacker

Processed in Photoshop CS3

Canon 350D modified

Canon EF 100mm f/2.8 Macro USM

Astronomik CLS filter

Astrotrac TT320

Télescope C11 - 280 mm - Focale 2800 mm

Monture Skywatcher EQ6-R Pro

Nikon D5200

346 photos - ISO 6400 - 15 sec

50 Darks - 10 Flats

Post-Traitement :

DeepSkyStacker, DxO, SIRIL, Topaz AI Denoise et Sharpen, GIMP

...that is the question. ;)

Nikon D70 modded, 55-200 Nikkor at 185mm (cropped), f6.3, 800iso, Baader Neodymium filter.

12 x 3 min, unguided EQ5

Darks, flats and bias

Stacked and processed in DSS and CS5, with a little help from Noel's tools.

Unspiked

The Butterfly Nebula and Sadr in Cygnus September 2013. Yet another collaboration between myself and Dave Williams (we'll run out of things to do soon).

This is a difficult one for me as the un-focal-reduced ED80 is a little slow, but the Ha helps. Added 35% Ha to the red channel to give it a boost, as well as using it for luminance.

RGB:

SW ED80/EQ5

Canon 500D modded, Baader Neodymium filter

101 x 180 second subs, iso 1600, for just over 5 hours

Acquisition: APT

Guiding: Quickcam Pro4000/9x50 finderscope, PHD

Stacked in DSS and processed in CS5

Ha (Dave Williams):

Stats to follow :)

Central region of the Milky Way visible through the constellation Sagittarius.

A couple of galaxy images from the rare clear night on Saturday.

29 x 1-minute exposures, ISO 6400, f/4. I also included a handful of 10-minute exposures at ISO 1600, taken previously, to further reduce digital noise. Modified EOS 600D & Revelation 12" Newtonian reflector telescope.

Frames registered and stacked in DeepSkyStacker software; curves adjusted in Canon Photo Professional; noise reduction in CyberLink PhotoDirector.

25x60s@iso400

65x30s@iso400

150mm (750mm FL) F5 Newtonian with GSO coma corrector.

First try with autoguiding using PHD2. Unfortunately the 3D printed guidescope mount was not nearly robust enough. 2/3 of the exposures were thrown out.

Stacked with DeepSkyStacker and post processed in Photoshop.

Unfortunately a large number of Geo satellites were present in the view and created streaks.

Next -- attempt to remove that pesky light gradient from the background

North-American and Pelican nebula imaged on the night of September 2, during a few hours of nautical/astronomic twilight in Tromsø. I opted for "mono" 12nm-filter as there was still a lot blue in the Arctic autumn twilight night sky. Seeing conditions were unusually stable compared to the usual turbulent atmosphere on the coast of northern Norway. Auroral activity was also quite low.

Canon EOS2000D (Baader modified)

Astronomik 12nm Ha-filter

Samyang135mmf2.0@f2.8

Skywatcher Staradventurer2i

ISO800, 129x60sec lights (+flats+darks+bias).

Stacked in DeepSkyStacker

Edited in Pixinsight using MLT, STF+HT and finally CT.

Haven't had the scope out for a while :) Unfortunately means a return to 60 sec exposures (and half of them I had to ditch). Bit of mist up there noticeable when the moon put in an appearance. May try adding more data to this over the next couple of days - if the forecast is to be believed. :)

200p/EQ5 unguided

Nikon D70 modded, iso1600, Baader Neodymium Filter

78 x 60 secs

Darks, flats and bias

Stacked and processed in DSS and CS5

Acquisition details:

OTA: Celestron 8" newtonian reflector, C8N

Filter: Astronomik CLS eos-clip

Corrector: MPCC

Mount: Celestron CGEM DX

Camera: Canon 450d mod BCF, 70F

Exposure: 29x2min ISO 800

Guided with PHD, SSAG, 9x50

Captured with BackyardEOS

Registered and stacked with DeepSkyStacker

Photographed from Round Rock TX (Orange zone

Tamron 55-200 zoom lens set to 85mm attached to an Atik 314L piggybacked to scope. 50 subs at 1 second each stacked in Deepskystacker and processed in Photoshop CS2.

Image taken early evening 03/04/20.

Total 2hrs 34 min

H-Alpha - 8x600s + 8x60s, Oiii 6x600s + 6x60s. (60s for the Core)

Stacked in DeepSkyStacker & processed in PS2. (Synth green)

Camera: Atik 314L+ Mono

Filters: Baader H-Alpha 7nm, Oiii.

Scope: Sky-Watcher Equinox 80ED .

Mount: AZ EQ6-GT goto, PhD guided with Orion 50mm guidescope & SSAG.

Skyobjekt: Messier-42 ( Orionnebula & NGC1977)

.

Equipment

Nikon D5300

Sigma 150-600mm

IBresser Messier EXOS-2 EQ GoTo

.

Lense 600 mm

ISO 2000

f/ 6.3

Lights 60x 60 sec

Darks 20

Bias 30

.

Edit

DeepSkyStacker

PixInsight

Photoshop CC

Lightroom CC

Three sessions over the last month or so resulted in 276 x 60 second subs for 4 hours 38 minutes. I find this a difficult one to process but I'm pleased with M82 (maybe a little bright), less so with M81, which is very noisy (are 276 subs not enough?!) First upload for a while :)

SW 200p, EQ5 unguided

Nikon D70 modded, iso1600, Baader MPCC and Neodymiun filter

276 x 60sec

darks, bias and flats.

Stacked in DSS and processed in CS5

Canon EOS 6D + Canon EF 70-200 F4 L IS, 191mm, F4. Stacking con DeepSkyStacker di 62 fotogrammi "light" (1sec, ISO 12800), 22 "dark" e 21 "bias", dal terrazzo di casa, in zona ad elevato inquinamento elettromagnetico.

Vuol essere semplicemente una prova per affinare il metodo di acquisizione e di post, sperando quest'estate, durante un soggiorno ad alta quota, di avere occasioni per fare scatti del genere, con risultati migliori grazie al cielo buio delle Alpi.

_________

Orion Nebula, astrostacking with DeepSkyStacker. Single photos taken in the nearby of Florence. This is simply an attempt made ​​to improve the technique in view of a stay at high altitude next summer, when I hope to be able take these kind of photos away from sources of light pollution.

40min total (8x300s@800iso)

Broadway Village 11/1/14

Takahashi FSQ106ED f/5

Celestron Advanced Vx Mount Guided

Canon D1100 (modified) CLS filter

BackyardEOS, PHD

Deepskystacker, Photoshop CS6

This is a stack (to reduce the noise) of 3 frames for the sky and 10 frames for the ground/sea. All 20s exsposures at f/2.8 and ISO 6400 taken with a Canon 60D & 14mm Samyang.

On clear summer nights, under a good dark rural sky, I can stare up into this region of space forever. Unlike the Sagittarius region, however, the Cygnus region just defies photography. I have imaged it many times and I'm seldom satisfied with the results.

Taken with my 400D and kit lens at 18mm. Typically I've left the lens wide open at f/3.5 to bring in as much light as possible; this time I stopped down to f/4.5 to try and bring a little better definition to the eleventy billion stars visible in the frame.

Stack of 6 five-minute shots, 18mm, f/4.5, ISO 1600; total 30 minutes exposition time. Stacked in DeepSkyStacker and processed further in Canon DPP.

Total of 44 minutes exposure (various settings, taken during different sessions). Modified EOS 600D & Revelation 12" f/4 Newtonian reflector telescope.

Frames registered and stacked in DeepSkyStacker software; curves adjusted in Canon Photo Professional; noise reduction in CyberLink PhotoDirector.

Taken in, and around, Algonquin Park, ON. My second attempt at stacking pictures seemed to work out favorably :) I forgot to take the dark and bias frames when I was there, so I stuck my camera in the fridge to bring the temperature down.

4 shots at ISO6400, f/3.5, 10mm, 30" stacked in DeepSkyStacker with dark and bias frames subtracted.

Slightly bigger one!

Moon+cloud = reprocess :) Also flipped to give the preferred orientation.

Almost full frame. 200mm is not a good lens with which to capture M31 :) Hey ho.

Nikon D70 modded, 55-200 Nikkor at 200mm, f5.6, 800iso, Baader Neodymium filter.

30 x 4 min, unguided EQ5

Darks, flats and bias

Stacked and processed in DSS and CS5

Please view large on black!

This is my first successful attempt at astrophotography! The first night was a bust, but I learned what not to do. I'm impressed this is even possible with just an (unmodified) dSLR, a fast lens, a tripod, and special software to process a number of images! The entrance to the park area of Tuttle Creek Lake is reasonably dark and shielded from the lights of Manhattan.

I am currently using Deep Sky Stacker, a free program, to process the individual images. It is critical that the stars do not have star trails, otherwise there tends to be problems precisely registering the images so that they align perfectly. I am using the highest ISO that gathers actual data as opposed to just adding noise. This is dependent on the camera model; it seems to be ISO 1600 for the Canon T2i. Prefer a fast prime lens to a zoom lens, especially when no kind of tracking is available. I used other ISO speeds in an attempt to gather more color information.

Be sure to turn off the display when you are taking pictures. The display will add extra heat to the inside of the camera, which will needlessly add extra heat to the CMOS sensor. For a CCD based sensor the noise doubles for every 6C (10.8F) increase in temperature. I don't know if these numbers conform exactly to a CMOS based sensor, but the principle still applies. While running technical tests on the Canon T2i by shooting a series of dark pictures, I found that the sensor noticeably heats up and produces far more noise. With a comparable set of darks with the display turned on, the sensor heated up even faster and produced a corresponding amount of extra noise. As a side note, with all things being equal and with a camera that isn't temperature controlled, it is better to take astrophotographic pictures while it is cooler outside for essentially the same reason. The cooler ambient temperatures keep the CMOS sensor cooler, which keeps the amount of noise down.

I found the Magic Lantern firmware to be immensely helpful in correctly focusing my lens in live preview and also providing an intervalometer. Focusing with the live preview is helpful, but it is best to take test pictures and compare them on a laptop before you get too far. It is just too hard to tell for sure if the focus is perfect on the LCD screen of the camera. It is better to spend more time upfront than to come back and find that all of your pictures are out of focus.

In the 151 image stack there were 3 sets of images. In each set there were about 50 light frames, 20 dark frames, and 100 bias frames. The dark and bias frames help to greatly reduce the noise in the image. I used photoshop to bring out as much detail and color as possible without emphasizing the noise too much.

Comparing visible stars to the catalog in Stellarium, it appears that the faintest recognizable star is around 13.7 apparent magnitude in the 151 stacked image versus 10.8 apparent magnitude in the single non-stacked image. [Apparent Magnitude]

I initially thought that 14x times more light was being picked up in the stacked image. (2.512 ^ (13.7 - 10.8) = 14.46) because the faintest recognizable star went from 10.8 to 13.7 apparent magnitude when comparing the single image to the stacked image. I'm not 100% sure any more. I previously thought that light was being gathered in a non-linear fashion with multiple exposures. A discussion on the Deep Sky Stacker Yahoo group, claims that an additional amount of exposure worth of light isn't being gathered in the stacking process. Instead, they say stacking greatly improves the signal in the resultant image, such that the faintest recorded stars are visible above the noise. The faint stars are in all of the exposures, but they are buried in noise. And additionally Blair MacDonald mentions that "In order to be detectable in the image a single star must be about 3 standard deviations above the noise floor."

However, I'm not convinced that no additional exposure worth of light is being added during the stacking process. In an exchange with someone else he says that "… a modern SLR is truly sensitive enough to capture and digitize individual photons. The read noise is generally between 2-20 equivalent photons, so that definitely gets in the way, because the light source you're trying to measure itself has noise (Poisson distribution). But yes, you can stack almost infinitely dim sub-exposures to get a result. The extra time required goes up dramatically at some point, because the read noise accumulates, but it is possible. This is why, all things being equal, longer exposures are better. But most of the time all things are not equal."--anonymous. If cameras are that sensitive, I can see how given enough sub-exposures and stacking, a periodic photon source at a particular pixel that only shows up in every x sub-exposures could still be translated into a luminosity value above zero.

To my knowledge everyone is recommending a certain number of sub-exposures to deal with practical issues, such as noise and tracking issues over very long exposures. John Smith released a couple of papers that are useful in determining the number of sub-exposures in imaging a particular deep sky object. I have created a spread sheet based on his work that should be useful to others getting started with astrophotography. You put in an initial sub-exposure time and total exposure time and it updates two tables. One table shows different options for keeping the same SNR but adjusting the number of subs-exposures and individual exposure times. The other table shows how SNR changes by keeping the total exposure time constant, but varying the number of subs-exposures and the individual exposure times. You can find it here. You should be able to open the spreadsheet either in Open Office or Excel.

There are some options for choosing the number of sub-exposures, but there is a practical minimum exposure that is needed to record the object. The practical minimum will depend on a number of factors. Some of them include the background sky luminosity, the camera/sensor being used, and the target object's luminosity. Keep this in mind when looking at the spreadsheet.

On a related note, I went out again and took over 1,400 images of the Orion Nebula with 200 dark frames! The outing was a bit of a bust because the images were slightly out of focus and had star trails. Despite the problems, I processed them as a massive stack with sigma clipping in Deep Sky Stacker. The image was virtually noise free and it appeared that there was slightly more exposure, but not by a huge amount given the number of pictures. The faintest recognizable star may have been about .5 magnitude dimmer in the 1,400 image stack. Maybe if it had been more in focus, there would have been a more dramatic improvement?

I am working on building a barn door tracker so that I can take much longer exposures and get images that are not practically possible for me right now. Being limited to 1 to 2 seconds at 85mm is very restrictive! It will use an Arduino and a stepper motor for automated tracking. From what I have read, I should be able to get 15x as long exposures (or more) before star trails show up.

In the process of learning more about lenses and astrophotography, I found out that chromatic aberration can be particularly problematic with the use of lenses. Most photographers are more familiar with the variety known as lateral chromatic aberration. But a special kind of chromatic aberration known as longitudinal chromatic aberration (or axial color), shows up as colored fringing that completely incircles objects such as stars. This is caused by the lens being unable to focus all wave lengths of visible light at the same point. My 85mm lens is not apochromatic and thus exhibits this flaw. I have gone back and replaced the original image that I uploaded with a hand corrected version that attempts to visually minimize the color fringing. Color tends to build up perceived contrast, so I greatly reduced the saturation of color in the purplish fringes and replaced the color with a small amount of random color from the background sky. I feel that this change is a noticeable improvement over the original. If anyone has thoughts on this, I welcome their input.

my identifier: orion nebula d

First deep sky stacked image: Andromeda with 8 stacked images and some calibration images, made with Canon Eos 5D mkii, Pentax 75sdhf, skywatcher az-gti, DeepSkyStacker and Photoshop.

I was going to have another crack at the horsehead tonight, but the high cloud was still about so I went for this instead (Alnitak doesn't like high cloud). Glad I did really - I've never got so much out of M42. Had to stop at 35 minutes because the clouds rolled in, but I had planned for 90 minutes - shame. First process, slightly hurried. I'll do it again when I get the chance.

200p/EQ5 unguided

Nikon D70 modded, iso1600, Baader Neodymium Filter

10 x 5 secs (core)

35 x 60 secs

Darks, flats and bias

Stacked and processed in DSS and CS5, with help from Noel's Tools

More time added and reprocessed here