Help me evaluate spacing/tilt (CCD-inspector)

[MartinFransson]

I have problem when using my Skywatcher 150-PDS newtonian and my ASI1600MM-Cool. I know I have some tilt but I think there is also an issue with the spacing. Could someone help me evaluate these CCD-inspector results?

Do I need to add spacing or should it be less? The images where taken using the Zwo Lum-filter. When using an Astrodon 3nm Ha filter (thicker), how should the spacing be altererd then?

 

[MartinFransson]

And here is a sub from my Sigma 500mm tele lens. Does it look OK or are there issues here too?

[Xplode]

I don't think there is any way to judge if spacing should move one way or the other way in CCD Inspecter, your best bet is to adjust spacing and look yourself if the images are better or worse.
Using different filter thicknesses isn't optimal, but it should not affect the spacing much with a f5 scope, you will probably not see the difference.

The sigma lens looks very good

[MartinFransson]

Just for comparison - here is the same scope/camera as in the first post, but with Astrodon 3nm Ha-filter. Less spacing issue it would seem?

Edited October 5, 2019 by MartinFransson

[spillage]

I think the 150pds is not looking that bad and I would be tempted to check how the finished images look. 

It might be worth checking that the focus tube is adjusted correctly and able to move around. I find that when connecting my kit to the skywatcher focuser I really need to take my time ensuring its sat as flat as possible in the focus tube. If I remember correctly I found that add too much spacing would cause the image in ccd to bend the opposite way to yours, so I would try adding maybe 1mm or 1.5mm and see how it then looks.

[Corpze]

Hi Martin.
I think we are on the same track trying to evaluate ccd inspector.. Trying to fine tune my new N-AG10
The spacing of my system was only shown on "real" images, not ccd inspector... maybe on the fwhm values as they are a value on how good focus you have.
The focus itself is represented of the background color in the "curvature" in ccd inspector. Black is best, whit is worst.
I measured my spacing with a skjutmått. (caliper?)

The tilt is just as it sounds, the camera ship in relation to the image field. in my case, the focuser (the starlight feathertouch focuser base has tilt adjustment screws, so it makes it quite easy for me)
the curvature is a effect of how good the corrector is doing it´s job, i don't think you could do anything about that other than to get secondary mirror centered correct, and the focuser tilt as good as you can.

/Daniel

[MartinFransson]

On 10/10/2019 at 14:44, spillage said:

I think the 150pds is not looking that bad and I would be tempted to check how the finished images look. 

It might be worth checking that the focus tube is adjusted correctly and able to move around. I find that when connecting my kit to the skywatcher focuser I really need to take my time ensuring its sat as flat as possible in the focus tube. If I remember correctly I found that add too much spacing would cause the image in ccd to bend the opposite way to yours, so I would try adding maybe 1mm or 1.5mm and see how it then looks.

 

On 10/10/2019 at 22:16, Corpze said:

Hi Martin.
I think we are on the same track trying to evaluate ccd inspector.. Trying to fine tune my new N-AG10
The spacing of my system was only shown on "real" images, not ccd inspector... maybe on the fwhm values as they are a value on how good focus you have.
The focus itself is represented of the background color in the "curvature" in ccd inspector. Black is best, whit is worst.
I measured my spacing with a skjutmått. (caliper?)

The tilt is just as it sounds, the camera ship in relation to the image field. in my case, the focuser (the starlight feathertouch focuser base has tilt adjustment screws, so it makes it quite easy for me)
the curvature is a effect of how good the corrector is doing it´s job, i don't think you could do anything about that other than to get secondary mirror centered correct, and the focuser tilt as good as you can.

/Daniel

Could it be a collimation issue? I noticed that my images has a darker edge, suggesting something blocking the light path. I then started thinking that maybe the secondary should be centered when looking down the focuser? It was not. I then made some adjustments, trying to move the secondary to a more centered position and the adjusted the mirrors so that the laser dot is centered in the marking on the primary mirror and that the reflected dot "dissappears" in the hole on the laser collimator. This is what the camera see now, if I take a photo down the focuser. Looks OK or am I totally off?

The camera lens looks centered on the cross formed by the spider vanes but the central marking on the primary (faintly visible ring) is not. Is that correct?

Maybe I´ll start a new thread since this has gone from CCDinspector to collimation...

P.S. The black, flat thing blocking the light to the right is the focuser tube.

 

Edited October 13, 2019 by MartinFransson