What do people think of these stars ?

[Spaced Out]

Hi All

I've been wrestling with tilt when using a heavy mono camera and filter wheel on my stock Skywatcher 130PDS focuser. After a lot of trail, error and faffing I have managed to eliminate the worst of the tilt by removing the flaky SW autofocus motor and adding more tension to the focuser.

Having done this and mucked about with things in the process I could see what appeared to be a little coma in all corners radiating inwards. I played about with various spacers for a couple of hours to get it as good as I could. By 1am my little brain was tired and I couldn’t fathom things out anymore so I packed up.

This single test shot shows how things looked when I left it. At the time it seemed like if I added 0.5mm things got worse and if I removed 0.7mm things got worse. However, by this point I was just seeing stars everywhere I looked !

So, I’m just wondering what people think of the stars around the edges/corners ? To my eye they look a little 'eggy' in places. Does it need more spacing ? Is it overspaced ? Is there still an element of tilt going on here ?

Thanks

Edited March 19, 2020 by Spaced Out

[tooth_dr]

Hi Gary

When you say 5mm and 7mm is that not a lot? I’ve spacers that I use that add 0.3 0.5 and 1.0mm, to fine tune. 

[Spaced Out]

10 minutes ago, tooth_dr said:

Hi Gary

When you say 5mm and 7mm is that not a lot? I’ve spacers that I use that add 0.3 0.5 and 1.0mm, to fine tune. 

Yes of course ! Sorry, I meant 0.5mm and 0.7mm. I've amended the original post 👍

Edited March 19, 2020 by Spaced Out

[tooth_dr]

5 minutes ago, Spaced Out said:

Yes of course ! Sorry, I meant 0.5mm and 0.7mm. I've amended the original post 👍

I can see the slight eggy shape. Hard to know what to do. 

[Davey-T]

Wouldn't worry about it myself, not worth loosing imaging time over, it may look better once stacked and processed and on that target you could just crop it a bit which will improve the focus of the image IMHO.

Dave

[Spaced Out]

28 minutes ago, Davey-T said:

Wouldn't worry about it myself, not worth loosing imaging time over, it may look better once stacked and processed and on that target you could just crop it a bit which will improve the focus of the image IMHO.

Dave

Thanks, that wasn't really a target, it was just overhead for a quick test shot.

Trouble is, once I notice un-round stars it really bugs me ! I want to try and get them as good as possible 🤔. Can stacking improve the shape then ?

 

[Davey-T]

34 minutes ago, Spaced Out said:

Can stacking improve the shape then

Usually helps.

Dave