Double Dohnuts!

[Graeme1858]

After discovering that the Horsehead fits nicely into my field of view a while ago I've been waiting for my chance to have a go at it. Right now it is idealy placed and Saturday night was clear. I captured 50 x 180 second subs, then 20 flats and 20 dark flats using the NINA Flats Wizard. Didn't do Darks because my alarm was set for 05:00 next morning.

Something is amiss! I've got double dohnuts (pun intended!) The target went past the meridian but not by much and the CGX is supposed to be able to go 20° past. If the camera moved I would expect the stacking to have failed. NINA has a % of Histogram of Mean Target setting and I did flats at both 30% and 50% just to experiment with but the effect is the same with either in the stack. In fact I get the same problem in an uncalibrated stack.

Any ideas?

Fairly pleased with how it came out otherwise though after spending time rotating the camera to place NGC2023 in the corner of the frame.

Regards

Graeme

[goldstar]

I had double donuts too. Didn't want them and didn't pay for them. They seemed to be caused by droplets of something that arrived on my DSLR sensor window and evaporated away as imaging progressed. I could see this from RAW frame to RAW frame. Heck knows what it was. May have been an insect using my sensor as a toilet.....

[Graeme1858]

I had double donuts too. Didn't want them and didn't pay for them. They seemed to be caused by droplets of something that arrived on my DSLR sensor window and evaporated away as imaging progressed. I could see this from RAW frame to RAW frame. Heck knows what it was. May have been an insect using my sensor as a toilet.....

RAW frame to RAW is a good idea. I captured 50 and discarded 7 or 8 due to cloud and guiding hichcups, I'll try a quick stretch on each one to see if I can see what's happening.

I hope it's not insect wee!

Regards

Graeme

[Graeme1858]

So I went through the frames and from 18:47 to 20:11 I have 23 subs showing the doughnuts and then from 20:30 to 21:41 I have 21 more subs showing the doughnut in a slightly different position. The gap is where I paused for clouds.

The image below was processed from the second set. The double doughnut has gone and I'm left wondering if I had a problem with the camera moving or if I had a mirror flop at meridian or something else.

Also the flat frames were less than perfect! Flats and Dark Flats are automatic in NINA, you set a % of mean histogram target and the exposure is calculated. I did 30% and 50%, neither were good.

Anyone got any flat frame tips?

Regards

Graeme

[Gordon]

The second image looks great! But hey.... Worst comes to worst, grab a cup of coffee to go with the donuts and your all set!!!