WO ZS71 + P-FLAT-F6 + APS-C problems

[Takashi]

Hi! I have the following setup:

1. William Optics Zenithstar 71

2. P-FLAT-F6

3. Standard T2 ring to Canon adapter

4. Canon 600D

It looks like the attached picture (except for camera)

According to this website:

https://agenaastro.com/william-optics-2-0-8x-apo-reducer-field-flattener-6-p-flat-f6.html

It says the distance from flattener to sensor should be 55-57mm.

The canon 600D has 44mm flange to sensor distance. The T2 ring is the normal common one which I think has around 12mm, so I should get around 56mm distance.

But whatever I do, the picture looks horrible in the corner with a APS-C sensor. See this image for example:

https://www.nineplanets.se/imageViewer_dark.asp?ID=97

Look at the corners... 😞

What am I doing wrong? Anyone else has experience with this combination?

This is the second WO telescope + flattener I have the more or less same problem with... so I guess I'm missing something?

[newbie alert]

Looks like tilt rather than spacing , these type of fixings can cause issues as they push the internal tube into strange angles.. personally I don't think it's spacing

[Takashi]

Thanks for fast response. Those two screws adjust a compression ring, and no matter how much I adjust these, the result looks the same.

[newbie alert]

4 hours ago, Takashi said:

Thanks for fast response. Those two screws adjust a compression ring, and no matter how much I adjust these, the result looks the same.

Spacing issues look far different from what you have , you can put your image through ccd inspector and it will show the faults such as sensor tilt..

I'm a big fan of solid fixings and solid aluminium spacers, I used delrin before and the thickness differs on different parts of the same ring.. once I'd sorted my spacing issues out and used solid rings my stars actually look like stars ..

This shows spacing issues

[Takashi]

Sorry, CCD inspector?

Delrin spacers?

Yes I agree, the problem looks a little like "Spacing too close" in your picture.