tornado33
03-10-2020, 11:53 AM
The other night under full moon wanted to test how the EOS Ra handles longer subs. With accurate polar alignment to within a few arc secs thanks to Sharpcap, and the off axis guider, I felt that half hour or longer should show nice round stars, depending on the Human Guider of course haha.
With bright moonlight, used the Duo Narrowband filter that lets in only Ha and O3 light. Live View sensitive enough to pick up one star to focus on, the seeing wasnt great, a seeming very rapid boiling that made the stars a little soft, I could see it in the highly magnified guide star image.
Set ISO to 800 and off I went, 2 x 30 minutes. Raw subs looked ok with the histogram roughly in the middle and surprisingly not a lot of thermal noise, amazing for an uncooled sensor. I was worried much of the pixel well depth would be taken up by thermal noise but not so. Also happy I could manually guide to get round stars over 30 minutes. Should I try 1 hour subs next time? The full thickness pyrex mirror might have still been a bit warm too as I started imaging as soon as it was dark not long after I set the scope up. Processed as usual in IRIS finished in Photoshop. Off axis guiding rocks, no flexure to worry about.
Full res view here https://www.astrobin.com/dehtmw/
Scott
With bright moonlight, used the Duo Narrowband filter that lets in only Ha and O3 light. Live View sensitive enough to pick up one star to focus on, the seeing wasnt great, a seeming very rapid boiling that made the stars a little soft, I could see it in the highly magnified guide star image.
Set ISO to 800 and off I went, 2 x 30 minutes. Raw subs looked ok with the histogram roughly in the middle and surprisingly not a lot of thermal noise, amazing for an uncooled sensor. I was worried much of the pixel well depth would be taken up by thermal noise but not so. Also happy I could manually guide to get round stars over 30 minutes. Should I try 1 hour subs next time? The full thickness pyrex mirror might have still been a bit warm too as I started imaging as soon as it was dark not long after I set the scope up. Processed as usual in IRIS finished in Photoshop. Off axis guiding rocks, no flexure to worry about.
Full res view here https://www.astrobin.com/dehtmw/
Scott