IC 1396, Elephant's Trunk in SHO

Great Elephant's Trunk @rickwayne ! Like it a lot !

Thanks for posting !

Great shot Rick,

Hey, I bought the ZWO 183MM Pro about a year ago and have been struggling with some banding or patterns in my photos. I am using 6nm Astronomik filters. I see you are doing 600" subs. I usually do 300' but did try 600" and I think I still saw the same issues. Can you tell me what gain and offset you are using? Are you noticing any of that in your photos? My latest OIII photos look like the amp glow is not being eliminated completely too. I have contacted ZWO and sent them a dark frame and they say it looks OK to them.

Thanks, Tom

PS- I see you're in Wisconsin. I am just across the lake from you in Norton Shores, Michigan.

For narrowband, I am using gain 173. Offset is 50, which is really just a magic number I pulled off a forum somewhere. 600" blows out the stars pretty fiercely, but I invariably shoot at least a little bit of 30" RGB for that purpose anyway. Then I composite those in instead of the stars I removed via starnet++. Of course sometimes I have to commit sins against Photoshop to fix the bloated bits left behind in the NB images after removal, a skill which I am, ahem, still developing, shall we say.

Actually I frequently use 300" subs for narrowband, I think it was just a really good night and I decided to try longer ones. I don't think 600" buys me much over 300" or even shorter subs, other than disk space and processing time. Elon is less of a problem in that bit of the sky vs., say, Orion, where it's practically de rigeur to use a ton of short subs so the statistical algorithms have enough to chew on while eliminate all the Starlink trails.

You're probably already doing it right, but I've found that the 183's amp glow is so strong that the calibration frames have to absolutely nail the values of the lights and flats -- "close enough" isn't, a seemingly minor discrepancy in the temp, gain, or exposure time and the dreaded starburst starts peeking out at you from your images.

If you just stretch the living heck out of an uncalibrated light, flat, or dark, does the pattern show up in any of them? Are you using bias, or dark flats? Whichever you use, you could try the other, just to see. If you're using bias, what exposure?

I am actually a Michigander by birth, so Wolverines represent! (Also it is SO WEIRD that the Lions don't suck this year but I like it. Not that I follow sports but osmosis is a powerful thing.)

I saw on a Cloudy Nights post by John Rista ( I think that's his name ) he was testing this camera and using gains of 111 and 53. I have tried them both and works fine for stronger Ha signal but not as well for OIII and SII. I always used gain 120 with my 183MC Pro and my next test was to try gain 150. I thought that seemed high but if you're using 173 I will give it a try. I don't think I have tried stretching a single shot but the pattern does show up in a master flat. I thought it might be adding the pattern to the final photos but I would expect it to take it out. I use dark flats but did just take some .1" bias frames to see if that makes any difference and it did not. Yeah, I don't follow sports much either but if you watch the news it's kind of hard to miss. Thanks for the info. 

Tom

If memory serves, 53 is a good "low gain" setting for the 183 and 111 is just about unity gain -- one ADU per electron. You give up a lot of headroom at higher gains, since the 183 only has a 15Ke full-well capacity at zero gain to begin with, but if you're not trying to capture bright stars and dim nebulosity in a single exposure, there's enough dynamic range, I find.

Yeah, Rista is the king of sensor expertise.