Hi,
I would really value the community's feedback on my first astrophotograph as an amateur. For over 30 years, I was a professional astronomer, having cut my teeth on CCD imaging and spectroscopy since the early 1980s. I was privileged enough to work at some of the best telescopes and sites in the world, including La Palma, La Silla, Hawaii and Siding Spring. I was lucky enough to be an early member in the Supernova Cosmology Project team, where extensive CCD imaging started us on the road to discovering the acceleration of the Universe. During my time as a professional astronomer, I always marvelled at the ability, knowledge and dedication of the "amateur" community. If ever there was a misnomer it is the word amateur applied to what you do. After moving away from research due to leadership commitments - I was Director of both the Anglo-Australian Telescope and Australia Telescope National Facility as well as Australia SKA Director - I have now retired to rural New Zealand, where one of the activities I would like to pursue is astrophotography. The photos on this site are the inspiration to me.
I took this photo of the LMC last night and I would value any advice you could give me.
This was taken on Canon 5D Mk II on Sky Adventurer mount with 105mm zoom lens at f/5.6 with 135 x 30 sec exposures. Reduced with PixInsight. Background correction and colour correction only applied post porcessing.
Yes I know this was a big stack - but I didn't trust myself to get the Polar alignment right.
A few things I noticed in the processing - average ellipticity 0.72. But FWHM = 2.5. I guess I focussed pretty well but the ellipticity is (presumably) dominated by the coma toward the field edge. I have a second-hand Canon 200mm f/2.8 prime lens on order for when the lockdown ends.
The average shift between individual 30sec exposures was 0.3px, increasingly largely monotonically over 30-50 frames (15-20 minutes) when there would be a jump of 10px over a single frame. Is this normal behaviour for the Sky Adventurer? [Gear worm?] The jumps usually coincided with a lower SNR ratio, and were discarded from the final stack, as were a few taken in twilight - I found the SNR to be unacceptable until about 15mins before astronomical night. [As a professional this also usually marked the start of useable data for me].
Is 0.3px in 30sec an acceptable polar alignment with a 105mm focal length? Should I try to better? Or invest in auto guider? [Or better mount?]
Finally on the picture itself. While I have a preference for natural colours - should I be looking to bring colours out more? Also is there more to bring out of the LMC's outer regions with an 75min exposure on an 105mm f/5.6 lens? It may be an aperture a few hundred thousand times less than the biggest telescopes I am imaged with but just as satisfying.
Thank you for welcoming me into your community.
Brian Boyle
I would really value the community's feedback on my first astrophotograph as an amateur. For over 30 years, I was a professional astronomer, having cut my teeth on CCD imaging and spectroscopy since the early 1980s. I was privileged enough to work at some of the best telescopes and sites in the world, including La Palma, La Silla, Hawaii and Siding Spring. I was lucky enough to be an early member in the Supernova Cosmology Project team, where extensive CCD imaging started us on the road to discovering the acceleration of the Universe. During my time as a professional astronomer, I always marvelled at the ability, knowledge and dedication of the "amateur" community. If ever there was a misnomer it is the word amateur applied to what you do. After moving away from research due to leadership commitments - I was Director of both the Anglo-Australian Telescope and Australia Telescope National Facility as well as Australia SKA Director - I have now retired to rural New Zealand, where one of the activities I would like to pursue is astrophotography. The photos on this site are the inspiration to me.
I took this photo of the LMC last night and I would value any advice you could give me.
This was taken on Canon 5D Mk II on Sky Adventurer mount with 105mm zoom lens at f/5.6 with 135 x 30 sec exposures. Reduced with PixInsight. Background correction and colour correction only applied post porcessing.
Yes I know this was a big stack - but I didn't trust myself to get the Polar alignment right.
A few things I noticed in the processing - average ellipticity 0.72. But FWHM = 2.5. I guess I focussed pretty well but the ellipticity is (presumably) dominated by the coma toward the field edge. I have a second-hand Canon 200mm f/2.8 prime lens on order for when the lockdown ends.
The average shift between individual 30sec exposures was 0.3px, increasingly largely monotonically over 30-50 frames (15-20 minutes) when there would be a jump of 10px over a single frame. Is this normal behaviour for the Sky Adventurer? [Gear worm?] The jumps usually coincided with a lower SNR ratio, and were discarded from the final stack, as were a few taken in twilight - I found the SNR to be unacceptable until about 15mins before astronomical night. [As a professional this also usually marked the start of useable data for me].
Is 0.3px in 30sec an acceptable polar alignment with a 105mm focal length? Should I try to better? Or invest in auto guider? [Or better mount?]
Finally on the picture itself. While I have a preference for natural colours - should I be looking to bring colours out more? Also is there more to bring out of the LMC's outer regions with an 75min exposure on an 105mm f/5.6 lens? It may be an aperture a few hundred thousand times less than the biggest telescopes I am imaged with but just as satisfying.
Thank you for welcoming me into your community.
Brian Boyle
