Spacing, or tilt issue?

[Matzi]

I've been noticing some weird looking stars, all around the edges and corners of my last two images.
I tried to figure out what it could be, but spacing shouldn't be the issue with this, as I see tons of people using pretty much same setup, just different DSLR cam.
Also I tried the same setup with a Nikon D5300 with no issues at all.

My setup is:
SW Evostar 80ED
0.85x SW Reducer/Field Flattener
First Light Optics Nosepiece
Nikon D5600a
SW Heq5 Pro mount

Please zoom in on the image to really see the star shapes.

[michael8554]

Need to see a single sub, stretched if necessary.

Looks like guiding otherwise.

Nikons have 46.5mm back focus, Canons have 44mm, did you adjust accordingly?

But if no issues with the other Nikon then I'd say guiding.

Michael

[Matzi]

But still wouldn't guiding affect ALL stars, and not just those around the corners? 

[Matzi]

Here's a single stretched, non-calibrated sub. But guiding was between 0.50-0.80" RMS

[michael8554]

I felt the stack had very slight elongation TL to BR on the whole frame. 

The single sub, maybe BL? 

Too close to call. 

I'd examine all your subs and make a judgement, could be tilt, Coma,  good guiding isn't perfect.

Sorry, no help at all really. 

Michael 

[Matzi]

But coma with a reducer/field flattener dosen't make sense?

All my subs are like this, stars are fine in a "circle" around the middle, but everything outside this "circle" and the stars are looking like this.
When I did some flats awhile ago, which are now deleted, as I deemed them unusable, they clearly showed a circle in the middle of the image, which makes sense with the stars in the light subs.

Edited March 26, 2020 by Matzi

[Adreneline]

You could download a 30-day trial version of CCDInspector and run your subs through that and see what it tells you.

 

[alacant]

Hi

The flattener needs to be closer to the sensor. Make sure there is nothing preventing mating surfaces meet, there are no spacers fitted and no crossed threads. This should also cure the slight tilt. Usually simply dismantling, cleaning and reassembling fixes stuff like this.

If not, try another t ring. Make sure it's on the 9mm side of 10 and that the threaded section is held firmly and squarely to the bayonet ring.

HTH

Edited March 26, 2020 by alacant

[Matzi]

10 minutes ago, alacant said:

Hi

The flattener needs to be closer to the sensor. Make sure there is nothing preventing mating surfaces meet, there are no spacers fitted and no crossed threads. This should also cure the slight tilt. Usually simply dismantling, cleaning and reassembling fixes stuff like this.

If not, try another t ring. Make sure it's on the 9mm side of 10.

HTH

I heard that this telescope, reducer fitted with a DSLR dosen't need any spacing, as it fits directly, even FLO said this to me. Again I used a Nikon D5300 with this exact setup with no issues.

 

 

12 minutes ago, Adreneline said:

You could download a 30-day trial version of CCDInspector and run your subs through that and see what it tells you.

 

Actually I'm on it right now to see.

[alacant]

3 minutes ago, Matzi said:

I used a Nikon D5300 with this exact setup

The same t-ring?

[Matzi]

1 minute ago, alacant said:

The same t-ring?

Yes

[alacant]

OK. You missed focus a bit, so any aberration will be magnified as you move from the centre. Otherwise, I'm out of ideas. Nail the focus and it will look better.

Good luck anyway and stay safe.

Edited March 26, 2020 by alacant

[Matzi]

25 minutes ago, Adreneline said:

You could download a 30-day trial version of CCDInspector and run your subs through that and see what it tells you.

 

I couldn't find the trial version, I downloaded it, installed it. And it let me use it once. Then it couldn't open cause it said I need to buy a license..

[Matzi]

1 minute ago, alacant said:

OK. You missed focus a bit, so any aberration will be magnified as you move from the centre. Otherwise, I'm out of ideas.

Good luck anyway and stay safe.

If it's only a focus problem, I'm relieved, but wouldn't focus affect ALL stars, including those in the middle?

[Adreneline]

4 minutes ago, Matzi said:

I couldn't find the trial version, I downloaded it, installed it. And it let me use it once. Then it couldn't open cause it said I need to buy a license..

Weird. I downloaded it last week and I'm now part way through my trial period - I've got 20 days to go still. Not sure then as the site says you get 30 days.

Edited March 26, 2020 by Adreneline

[alacant]

4 minutes ago, Matzi said:

wouldn't focus affect ALL stars

Hi

Yes, it has. If you were in focus the central stars would be smaller and the edge aberration reduced, probably to the point of being acceptable.

Cheers

[Matzi]

3 minutes ago, alacant said:

Hi

Yes, it has. If you were in focus the central stars would be smaller and the edge aberration reduced, probably to the point of being acceptable.

Cheers

I was in perfect focus before I started, but maybe focus shifted. I imaged another target for 40 mins before this one. So slewing, cables hitting the focus knobs during slewing, slight temperature change might have changed iy.

[Matzi]

I figured out how to use the CCDinspector, to inspect my subs, not sure if I used it correctly, but I'll upload the results I found.

 

[alacant]

20 minutes ago, Matzi said:

I was in perfect focus

Hi. Lack of blue chromatic aberration suggests you focused on the blue, making all the stars bigger.

HTH

EDIT: look at the fwhm values. I can't remember what we got with ours, but this would suggest poor focus. Maybe a current ed user can confirm?

Edited March 26, 2020 by alacant

[Matzi]

Focused on the blue, what do you mean by that? I used a Bahtinov mask, and focused on the yellow star Pollux, all the spikes were perfectly alligned.

[Matzi]

Found a 3D curvature of all images combined.

[alacant]

2 minutes ago, Matzi said:

I used a Bahtinov mask

IIRC, the mask will give you the dominant colour. If blue is in focus, red and green are out and vica versa. Do I notice green star halos? (I'm certainly not the one to ask about colour!)

I remember looking at a bright star and re-focusing until the blue fringe JUST disappeared; no mask.

[Matzi]

Well I never really had any previous problems with focusing using a Bahtoniv mask.

But being all new to that CCDinspect software, I did get this result from using all 23 images combined.