Tej Dyal
M13 Great Hercules Cluster via 80mm refractor from London living room window on Alt Az mount
This image of the Great Hercules cluster is by far not the best tribute to this glorious globular cluster as I imaged this in all the worst conditions possible as a challenge to see what can be achieved which I'll give details later for those of you interested.
But first, I just want to say something about the M13. Yeah its a bunch of stars clustered up together, what's the big deal?
The big deal is that globular clusters are ancient relics of the universe, many of the stars being nearly as old as the universe itself, born just a few hundred million years after the big bang. Older than our own galaxy itself. Some of these stars are just second generation. We never see any first generations stars because they were mostly born as giant stars that live short lives, explode and give birth to heavier element second gen stars. So when I look at the M13 through my telescope, I do so in awe, at the fact I dont need Hubble to show me the near beginnings of the universe, we have it just outside our backdoor of the Milky Way as Globular Clusters hover below or above the plane of our galaxy.
So back to the actual motions of my attempt at imaging this from
Obstacle 1: Imaged in Inner London (Peckham) which of course is one of the heaviest light polluted cities.
Obstacle 2: Imaged from inside my living room window with my telescope mounted on a sturdy table but on a rickety floorboards!
Obstacle 3: Using an Alt-Az mount (no tripod) just resting flat on a table. Alt Az mounts limits exposure times due to field rotation.
Using an 80mm refractor and a normal unmodified canon 650d dslr camera. No filters.
Result aint half bad methinks. So if any of you have limited equipment and find it hard to get out and enjoy astrophotography in darker skies, there are ways to get around enjoying astrophotography from the warmth of your home ;) Although, it aint that warm when you got the bloody window open, much to the annoyance of the rest of the family sitting on the sofa trying to watching Strictly Dancing.
More advanced astrophotographers use advanced astro cameras and narrowband or LRGB filters to image some wonderful nebulas and clusters in London, such as Jaspal Chadha and Rupert Smith (look up their excellent flickr galleries). But we lesser imaging mortals can achieve something with lesser dedicated equipment.
There is a big caveat to all this though. I had to take hundreds of frames at very short exposure times to combat the light pollution and limitations of the Alt-Az mount. Altogether, I took 1500 frames (500 at each ISO of 1600, 3200 and 6400). This is not healthy for your dlsr shutter which has a finite shutter use. So probably best not to make this a frequent thing.
Because I am using an Alt-Az tracking mount, hundreds of frames were unusable. due to the "step stagger" type of tracking from the Alt Az (An equatorial mount has a very smooth tracking, so allows much longer exposures to be taken with fewer to no bad frames).
I took a mixture of ISO frames at 1600, 3200 and 6400. I would have liked to add 800 too but ran out of time. I took dark frames and bias frames for each ISO setting too. Used DSS to stack them all in one go, which took 11 hours! And that's on my pretty high powered laptop. DSS is amazing in that it also de-rotates the images as my Alt-Az mount rotates the field of view over time unlike an equatorial (another reason to image with equatorials)
That's another drawback of doing imaging in light polluted skies, the many more short frames takes longer to process. What surprises me is that because I have the 1600 ISO included in the stacking, I am able to get colours from the stars, after some adjustments on curves, levels and RGB alignment. If I had time to do iso 800 frames, I wonder if I could get even more colour out of the stars. I will test that again in another session. I did actually image with my bigger scope 8" SCT at the living room window too but only had time for ISO 6400 frames and although more detail in the cluster, I couldn't extract any colours so confirming that lower ISO gives a wider dynamic range. Will have another "Living room rickety table" session and take lower ISO images on my 8" next clear sky evening :)
I noticed as I zoomed in on the stars, my focuser slackened and so over the time of the capture period the scope tilts further upwards as it tracks M13 but the weight of the camera shifted the focuser which I think I forgot to tighten up. Oh well.
Info:
Telescope: 80mm Equinox APO refractor with a field flattener
Mount: Nexstar 6/8SE Alt Az on a sturdy table but on rickety floor boards!
Camera: Canon 650D unmodded
1240 X 4 Sec Light frames (about equal amount of 1600, 3200, 6400 ISO)
50 Dark frames ISO 1600
50 Dark Frames ISO 3200
50 Dark frames ISO 6400
Stacked with DSS (Deep Sky Stacker). Manually adjusted RGB levels.
Used curves, levels, and saturation in Photoshop.
M13 Great Hercules Cluster via 80mm refractor from London living room window on Alt Az mount
This image of the Great Hercules cluster is by far not the best tribute to this glorious globular cluster as I imaged this in all the worst conditions possible as a challenge to see what can be achieved which I'll give details later for those of you interested.
But first, I just want to say something about the M13. Yeah its a bunch of stars clustered up together, what's the big deal?
The big deal is that globular clusters are ancient relics of the universe, many of the stars being nearly as old as the universe itself, born just a few hundred million years after the big bang. Older than our own galaxy itself. Some of these stars are just second generation. We never see any first generations stars because they were mostly born as giant stars that live short lives, explode and give birth to heavier element second gen stars. So when I look at the M13 through my telescope, I do so in awe, at the fact I dont need Hubble to show me the near beginnings of the universe, we have it just outside our backdoor of the Milky Way as Globular Clusters hover below or above the plane of our galaxy.
So back to the actual motions of my attempt at imaging this from
Obstacle 1: Imaged in Inner London (Peckham) which of course is one of the heaviest light polluted cities.
Obstacle 2: Imaged from inside my living room window with my telescope mounted on a sturdy table but on a rickety floorboards!
Obstacle 3: Using an Alt-Az mount (no tripod) just resting flat on a table. Alt Az mounts limits exposure times due to field rotation.
Using an 80mm refractor and a normal unmodified canon 650d dslr camera. No filters.
Result aint half bad methinks. So if any of you have limited equipment and find it hard to get out and enjoy astrophotography in darker skies, there are ways to get around enjoying astrophotography from the warmth of your home ;) Although, it aint that warm when you got the bloody window open, much to the annoyance of the rest of the family sitting on the sofa trying to watching Strictly Dancing.
More advanced astrophotographers use advanced astro cameras and narrowband or LRGB filters to image some wonderful nebulas and clusters in London, such as Jaspal Chadha and Rupert Smith (look up their excellent flickr galleries). But we lesser imaging mortals can achieve something with lesser dedicated equipment.
There is a big caveat to all this though. I had to take hundreds of frames at very short exposure times to combat the light pollution and limitations of the Alt-Az mount. Altogether, I took 1500 frames (500 at each ISO of 1600, 3200 and 6400). This is not healthy for your dlsr shutter which has a finite shutter use. So probably best not to make this a frequent thing.
Because I am using an Alt-Az tracking mount, hundreds of frames were unusable. due to the "step stagger" type of tracking from the Alt Az (An equatorial mount has a very smooth tracking, so allows much longer exposures to be taken with fewer to no bad frames).
I took a mixture of ISO frames at 1600, 3200 and 6400. I would have liked to add 800 too but ran out of time. I took dark frames and bias frames for each ISO setting too. Used DSS to stack them all in one go, which took 11 hours! And that's on my pretty high powered laptop. DSS is amazing in that it also de-rotates the images as my Alt-Az mount rotates the field of view over time unlike an equatorial (another reason to image with equatorials)
That's another drawback of doing imaging in light polluted skies, the many more short frames takes longer to process. What surprises me is that because I have the 1600 ISO included in the stacking, I am able to get colours from the stars, after some adjustments on curves, levels and RGB alignment. If I had time to do iso 800 frames, I wonder if I could get even more colour out of the stars. I will test that again in another session. I did actually image with my bigger scope 8" SCT at the living room window too but only had time for ISO 6400 frames and although more detail in the cluster, I couldn't extract any colours so confirming that lower ISO gives a wider dynamic range. Will have another "Living room rickety table" session and take lower ISO images on my 8" next clear sky evening :)
I noticed as I zoomed in on the stars, my focuser slackened and so over the time of the capture period the scope tilts further upwards as it tracks M13 but the weight of the camera shifted the focuser which I think I forgot to tighten up. Oh well.
Info:
Telescope: 80mm Equinox APO refractor with a field flattener
Mount: Nexstar 6/8SE Alt Az on a sturdy table but on rickety floor boards!
Camera: Canon 650D unmodded
1240 X 4 Sec Light frames (about equal amount of 1600, 3200, 6400 ISO)
50 Dark frames ISO 1600
50 Dark Frames ISO 3200
50 Dark frames ISO 6400
Stacked with DSS (Deep Sky Stacker). Manually adjusted RGB levels.
Used curves, levels, and saturation in Photoshop.