Yes indeed Dunk. Nice field of view at the f 5.5. That looks like Unity at that sub length, is it? Did you try longer subs, or a mix to find where they might start to "over cook" ?
Regarding going below unity in future, just keep in mind the fact that this is only a 12-bit camera, so you want to do lots of short subs which will get that effectively back to 16-bits (or above), lest you incur some posterization.
I've gleaned lots of interesting nuggets about this camera from the "other side" but I'm also a believer in finding the sweet spot, which may vary from unit to unit.
According to Pixinsight, my camera has maximum dynamic range (a full 12-bits) at gain=75. I have captured a couple of subjects at that and I can't see the difference I've not noticed any posterisation either, maybe I'm just blind
Looks better in yours than mine, slightly wider field
Disregarding the slight difference between each camera there is only a 22% increase in dynamic range between Gain 75 and Unity. Gain 75 has a little more than double the well depth BUT the read noise is lower at Unity so only about half the exposure time is needed to be read noise limited.
From the single run of calibration frames that I used for my testing (there may be some variance if I did another run as there always is) I was getting 11.93 bit at Gain 75 and 11.25 bit at Unity. Now every camera is a bit different as well and if I run it again it may be different also.
Ray uses a Gain of 100 so your thought of half way between the two may be very well on the money
Nice detailed images there Dunk. I've settled on 75 myself, seems to get me the best star colours. No science used, just tried various length subs at differing gains to decide the setting visually. I believe my eyes. But I may be lucky, had some bloke in CN saying he didn't believe that I could do 10 min subs and still get good star colour.
Hoping you do yet more experiments on varying settings, but the weather is back to intermittent here and whenever the skies clear I just get greedy for photons!
Thanks Simon! I should probably post a shot of the core at full resolution
I'd imagine there are at least a few variables at play in getting good star colour. I've used 200 and been happy with the results too it's a very versatile camera!
Regarding going below unity in future, just keep in mind the fact that this is only a 12-bit camera, so you want to do lots of short subs which will get that effectively back to 16-bits (or above), lest you incur some posterization.
For those that are curious...here's a crop around an area with contrast/details. This is 100% resolution, barring saving as a JPEG of course
When processing, I haven't "progressed" to masking regions and applying different levels of enhancement, so I look at the image and see what works well across a few carefully selected regions before picking the settings I like best.
And just keep in mind...this is 72 minutes of exposure time with a 4" apo, I'm sure it could be improved upon
For those that are curious...here's a crop around an area with contrast/details. This is 100% resolution, barring saving as a JPEG of course
When processing, I haven't "progressed" to masking regions and applying different levels of enhancement, so I look at the image and see what works well across a few carefully selected regions before picking the settings I like best.
And just keep in mind...this is 72 minutes of exposure time with a 4" apo, I'm sure it could be improved upon
Looks great to me, Dunk, if there's any posterisation there then my eyes aren't good enough to detect it. I'd be very happy with that data :-)
Nice Dunk the Eta neb looks quite magnificent in B&W and I agree with M&T, when I compare with work I did over 30 years ago with film and cold cameras etc....the mind boggles
it's a very versatile camera!
