Orion Nebula under a full moon

[Iem1]

Morning guys,

I went out under a full moon on a bit of a test drive this evening to trouble shoot and test some theories. Thought I would shoot the brightest thing I could. Long story short, I found my focus to be shifting through the imaging session. About 30-40 minutes worth of data into my imaging session I did a check (Stopped imaging and zoomed in on my Canon screen to check PA and focus etc) and noticed it had shifted (even after I 'locked' focus on the scope), so I refocused and went again.

It was quite a bit out too, think now I know why images appear soft.

After refocusing, I shot for another 30-40 minutes and checked again and the focus had not shifted, so I am assuming it is temperature related. It was freezing out (Ice on gear) so I think I will trying setting up my rig and leaving it for a good 30-40 minutes. Does this sound like it might be the culprit, the scope adjusting to temperature? Its is a William Optics Z73 III 430mm APO refractor.

Anyway, I managed a grand total of 25 minutes of data on Orion, but at least this time I had a semi decent focus (I think)  

x50 30 second subs OSC Canon 600D

Also, do the stars looked trailed on the right hand side of the image? Seem ok to the left, but a bit off to the right? There is no doubt a bit of trail anyway as I am still using the SGP and it is horribly balanced, but never noticed that before.

[Iem1]

Bit more data added, ~1.5 hours 

There is more in the image to be had, but the flats on the second night are not very good, quite the gradient to contend with and it becomes really obvious with a stronger stretch!

I tried to DIY some new flats, but they were the same. Setup has been moved around now so it is as good as it gets I think.

Not sure why, but uploading it here blurs the image a bit. Looks a lot sharper when it is just opened on my laptop or in PS etc

 

Stacked Tif if anybody wants a play

result.tif

[Richard_]

You hit the nail on the head! Focus will change as ambient temperature rises or falls through the night, and the amount of defocus depends on the telescope/lens used. People with auto focusers tend to refocus after the temperature has changed by a certain amount (eg 2°C) and/or after a certain amount of time has elapsed. 

I'd recommend keeping an eye on the temperature and manually check the focus through the night. If you have one of those wireless weather station thingies you could place the probe near your camera and use that as a guide to go out and check/adjust focus? 

PS your image looks lovely, nice work even with a full moon out! 

[A P B]

I made it more vibrant in PS. Is this sort of thing ok? Or do you not process images like this?

Adrian

[Iem1]

Thank you Richard, did not realise how much and how quickly the temp could affect focus. Will definitely look into getting one of those  

And it looks great APB! Nice job!

New Process, doesn't look much different from the original 25 minutes of data! But I think I handled the stars and the gradient a bit better. Removed stars earlier and did a background extraction on the starless layer. Siril auto stretch does produce some of the faint surrounding dust, but at the expense of the rest of the image. Becomes far too noisy and the gradient is too much, this is as good as I can get it. 

 

 

Edited January 19, 2022 by Iem1