Eggy stars - my sensor too close?

[michael8554]

Your 3 minute sub has little or no tilt, but does show guiding errors, all the stars are elongated at 45 degrees to the horizontal.

You need a short exposure, stretched if necessary, to show star shapes without guide errors.

Michael

[AstroNebulee]

2 hours ago, michael8554 said:

Your 3 minute sub has little or no tilt, but does show guiding errors, all the stars are elongated at 45 degrees to the horizontal.

You need a short exposure, stretched if necessary, to show star shapes without guide errors.

Michael

Thank you. I was getting the same issue with a 30 second sub too. I haven't got the inage on me as yet, it's on my laptop. But will post it soon and really hoping to get out and test the 5mm spacer. 

 

[AstroNebulee]

Update number 1054. I managed to get out with my scope last night and try out testing the additional 5mm of extra spacing in my imaging train. It appears to be so much better, there's just and issue of tilt in the bottom left corner now. This is a 30 second single sub on Regulus my test and focus star. So my back spacing is now 60mm. This consists of long tube version of sw 72ed, sw rotator, ovl FF, 60mm of spacing including zwo tilt adjuster and zwo 294mc pro. Just got to figure out which grub screw to alter on my tilt adjuster to sort eggyness in bottom left. I'm much happier than I was Tuesday night when it was all pants before the 5mm spacing was added for Friday night test. I'll add that guiding was good when it was first clear but then the transparency deteriorated a lot. 

Edited February 26, 2022 by AstroNebulee

[AstroNebulee]

Hopefully the final update of my eggy star issue.  I've added a 1mm T2 spacer to my imaging train and another slight adjust to the tilt adjuster and on this 3 min crudely stretched M51 the stars are much rounder now and I'm happy this has been mechanically sorted (it may need another thin spacer to be added in the future) Then whilst searching through my star tools software there's a heal function with warp or redistribute algorithm to help with any oval eggyness in images as long as it's not to bad, so tried this and wow. (I know it's cheating in the processing but mechanically it looks OK too) I'm so so happy now, after 2. 5 months of adjusting, purchasing parts, waiting for clear skies, stress, more adjustments and ballache I think I'm finally hopefully there. 

First image is the crudely stretched 3 min sub without the Startools heal function 

And the second is using the Startools repair module then redistribute algorithm. 

 

This thread is entwined with this thread about scope or sensor tilt 

Cheers 

Lee 

Edited March 10, 2022 by AstroNebulee

[Turbocoo]

Hi Lee seems I'm at the same place you were and it's doing my head in, especially as I have few clear skies. 

I've got the newer 72, ovl flattener, rotator and started with 55mm.

I also centered the focuser with the laser but my pics are rubbish. 

Any advice greatly appreciated. 

Tempted to send it back and stick with my 130pds! 

[Turbocoo]

[AstroNebulee]

3 minutes ago, Turbocoo said:

 

Looking at your M31 images shows tilt too, only the bottom right corner looks ok to me when pixel peeping. 

I have the older (longer tube version) and use 64mm of backspacing atm 

Lee

[Pitch Black Skies]

20 minutes ago, AstroNebulee said:

Looking at your M31 images shows tilt too, only the bottom right corner looks ok to me when pixel peeping. 

I have the older (longer tube version) and use 64mm of backspacing atm 

Lee

Lee can you take a look at my thread in the imaging section. I'm having a similar problem. I can upload a raw sub for you.

 

Cheers,

Alan

[AstroNebulee]

3 minutes ago, Pitch Black Skies said:

Lee can you take a look at my thread in the imaging section. I'm having a similar problem. I can upload a raw sub for you.

 

Cheers,

Alan

Will do Alan 

[Pitch Black Skies]

Just now, AstroNebulee said:

Will do Alan 

 

[Turbocoo]

21 hours ago, AstroNebulee said:

Looking at your M31 images shows tilt too, only the bottom right corner looks ok to me when pixel peeping. 

I have the older (longer tube version) and use 64mm of backspacing atm 

Lee

Thanks Lee,  yes the tilt is really bad and you are correct, only 1 corner seems OK. 

I managed to get 2 subs rotated 180 apart here's the pics along with their respective curves 

[AstroNebulee]

Both your images show the same level of tilt, the bottom right stays the best over the 2 frames you've taken suggesting that indeed it is sensor tilt and not scope tilt. 

Though in your ccd inspector images it appears different? 

There's a link here from zwo about sensor tilt. 

https://astronomy-imaging-camera.com/tutorials/reason-of-field-tilt-problems-and-how-to-solve-it.html

Lee

Edited August 14, 2022 by AstroNebulee

[Turbocoo]

On 13/08/2022 at 14:30, AstroNebulee said:

Looking at your M31 images shows tilt too, only the bottom right corner looks ok to me when pixel peeping. 

I have the older (longer tube version) and use 64mm of backspacing atm 

Lee

Lee, 64mm!!?  9mm above the recommended 55mm. 

Are you satisfied with the field at that spacing? 

Besides my tilt I'm really having second thoughts.... Keep putting money and precious few clear skies into experiments with the 72ed and ovl ff spacing , or buying the dedicated ff, or returning the 72ed with its poorly supplied collimation and biting the bullet and get a something that can produce decent results from the get go with similar wide field. 

Best Bryan 

 

[AstroNebulee]

1 hour ago, Turbocoo said:

Lee, 64mm!!?  9mm above the recommended 55mm. 

Are you satisfied with the field at that spacing? 

Besides my tilt I'm really having second thoughts.... Keep putting money and precious few clear skies into experiments with the 72ed and ovl ff spacing , or buying the dedicated ff, or returning the 72ed with its poorly supplied collimation and biting the bullet and get a something that can produce decent results from the get go with similar wide field. 

Best Bryan 

 

Yep 64mm (I remember a thread here somewhere where others using the old 72ed, rotator and ovl FF had to increase spacing) though I've upped that now to 64.6mm as I've introduced my 2 inch filter drawer back into the frame and had to add 0.6mm because of the thickness of the L3 filter and previously 64.3mm wasn't enough (see attached sketch, it's crazy, hence why I've asked for 9mm spacer to do away with my 7mm and 2mm of shim) I used to have the filter in the rotator and not used the filter drawer (experiment) but I think my images should be sharper and less bloating as the last thing the light passes now is my filter. 

I'm sure my spacing issue is a combination of the older 72ed, rotator and ovl FF. I haven't tried my setup since move the filter back yet but previously there was still a touch of tilt in the bottom left but only if you pixel peeped and really don't want to tweak the tilter if I need to, but may have to at some point. One day I may strip it all back down to basics no shim or added spacers, reset tilt adjuster and start again 🙄. 

I did try the dedicated sw FF reducer but couldn't achieve focus not enough inward travel as its the old 72ed. 

I think the ovl FF isn't the best combination so maybe try the dedicated one as your scope is compatible. One thing with the 72ed is that the focus draw tube isn't the best and can have slop which can cause collimation issues, I had to re-tension and re-collimate mine. 

If I had the money I'd buy a WO gt with all the gubbins but I can never afford that. 

Could you send your 72ed back if it's under guarantee to be checked over? 

Lee 

Edited August 15, 2022 by AstroNebulee