Idea for tilter for EOS camers, to compensate for sensor tilt..

[bojan]

Since I have a small tilt issue with my Canon 60D now, after IR filter removal (~20-25 /um, it was not easy to put the sensor tilt screws back in precisely the same position), I came up with idea how to sort it out without dismantling the camera again and without putting a too big hole in my budget..

The solution is to modify existing T2-EOS adapter (from ebay) (https://www.ebay.com.au/itm/145545608721?itmmeta=01HSCGE0Z9BB2X PAS96XKVN4WP&hash=item21e331be11:g:Z1MAAOSwZGJcn c6S&itmprp=enc%3AAQAJAAAAwD9WFPhCgj0vMF gFZqUymzF7PHKvIfWaawyDrV4ZhCeo6K4wr GGMidPdg63%2BCCWPKVc8yqVCu76KXXAJ%2 FtNuqHiG4nWMjp734ywLg3kkoRvxK8VcqdG 4h0dg1x0BmggI7pzJfvuQft8mgaTM0GLL3i YNwZmVCjN%2FiCzI8KcLYiOOlfDhXfjFDBG 3rxDeu6IW3xPyc71%2BU9uKKLVaxtJsFTF7 nLtGa8JsP4ZVO%2BaE%2Fu0x9ZsnnXZQuJ7 2SJ8ZW9VWiw%3D%3D%7Ctkp%3ABk9SR_qPu JDLYw)to allow tilt.
All I need to do is to widen a hole in outer ring (with EOS adapter), and to add a collar (and glue it) on inner ring (with T2 thread).

Such new, enlarged adapter insert has to be machined (add curvature on outer edge) to allow tilting and three M3 threads need to be added on the bottom side for tilt adjustment.
Also, something elastic (rubber ring? steel spring?) needs to be inserted to allow precise adjustment for those couple of 1/10's of mm.


EDIT:
Of course, the simpler solution is to add suitable shims between insert and outer ring, with just a small reduction in insert ring diameter (0.2~3 mm to allow for tilt).
This solution is better for smaller tilt adjustment.. I will have to check first with shims between camera and adapter (bayonet)

[Cyberman]

Bojan, looking at your abberation analysis, it might be the distance from sensor to corrector that needs adjustment.The coma looks similar in all 4 corners. I could be wrong as I am only a beginner. I am sure there are more experienced people than me on IIS that could help. Rob.

[Ryderscope]

Just to back up what Rob has said, it is worth getting the set back distance correct before trying to adjust the tilt. The concentric stars around the edge of the field indicate that there is too much spacing and therefore the set back distance needs to be reduced. See attached diagram. Reviewing your attached aberration diagram, it does indicate that the stars in the top right have a very slightly reduced concentric nature to them so you may find some residual tilt there once the set back distance is correct.

A quick test that can be done to confirm this is to move the focuser inwards by very small amounts whilst taking test images. You should see the concentric stars move towards round stars whilst the stars in the centre go out of focus.

CS,
Rodney

[bojan]

Thanks Rob and Rodney for comments :-)
As to distance from flattener... My setup is C11 and FF-FR.

I believe the image Rodney supplied is applicable to refractors only..
After hours spent playing with varying sensor to FF-FR distance by +/- 10mm, and using both Celestron and Meade FR, there was no significant differences in behavior that I could detect. So my conclusion was it was FR thing, and sudden increase in field curvature away from centre (both C and m Meade behave almost the same way), in the area already affected by vignetting (~6mm away from sensor centre).. So I decided to crop out the corners of the frame and keep only central square where those aberrations are not visible.
https://www.iceinspace.com.au/forum/showthread.php?p=1558975#post155897 5


Generally there is not much info on the subject out there.. just a lot of confusion..
Funny thing, the best results re filed curvature I obtained with my "own" flattener - 50mm doublet (200mm FL) that came from old russian binoculars, but the coma and CA is slightly increased. (BTW, I have thread on this subject on forum, link is here (https://www.iceinspace.com.au/forum/showthread.php?t=198994&highlight=focal+reducer).

Anyway.. at the moment I put this project (tilter) on hold for a while, but I will revive it when my circumstances allow.

[Ryderscope]

I’m interested in the observation that the spacing diagram is applicable to refractors only. Ive heard this stated before but have never been able to track down any primary sources that confirm this. Do you have evidence to state that it is applicable only to refractors? If yes, I would very interested to peruse this. Also, it would informative to execute the test with racking the focuser in and out as I mentioned above with your system as I believe that it would give you more clues as to the issue. It could also answer the questions as to whether the diagram is applicable to refractors only.

[bojan]

No other evidence, except only a note on the top of the diagram (attached), which appears to be the same/similar to images you supplied but from the whole page (??)
Also, as I mentioned earlier, my setup is C11 (SCT), and I haven't observed much difference between star images in corners of APS sensors when I varied the distance... definitely nothing similar to what diagrams suggest.


BTW.. in this post (link below), there is a link to Telescope Optics website (https://www.telescope-optics.net/miscellaneous_optics.htm), where simulation of the C11+FR can be found.
At the time I was dealing with this, I had only Meade FR, which is slightly different in design to Celestron, but similar in performance.
I was thinking about putting those numbers into OSLO and play with simulation.. maybe soon.



https://www.iceinspace.com.au/forum/showpost.php?p=1559324&postcount=37