Camera tilt..

[xelasnave]

I never thought I would be concerned but I think the time has come...how do you guys do it? Camera tilt? I thought it was just the sensor but maybe that is too simplistic.

I was just going to get some Allen keys and have a fiddle but in my attempt to find out which screws to adjust I run into a video where the guy has built a rig with a laser and is talking about tilt of the pixels, sensor and the glass cover from what I can tell...I saw Andy from here put up a video saying he has attended to stuff like that but no usable specifics...any pointers on which screws to play with would be a help (zwo 2600)...

Any advice or input gratefully received.


Alex

[Retrograde]

Hi Alex,

I'm at a similar stage to you in that I want to correct for tilt with my ZWO 2600mc but haven't been sure how to go about it.

A few days ago I stumbled across this thread on Cloudy Nights: https://www.cloudynights.com/topic/809050-tilt-discussion-astap/ which discusses using the program Astap to quantify tilt & adjust for it. I'm still new to using Astap but have analysed a couple of my images using it and it looks like a way forward. The thread is extremely long however but hopefully it's of some use to you.

A good idea might be labelling the adjustment screws and keeping a log of your changes so you can back them out if they go the wrong way & make things worse. With your RASA being such a fast focal ratio it would be particularly sensitive to tilt.

Hopefully others with more experience doing this might chime in.

[Startrek]

Alex,
I had camera tilt issues using my 2600MC , fiddled around with those adjustable grub screws etc…, and so posted my problems on the ZWO forum and received lots of replies saying back off those crappy spacer grub screws and tighten your tilt plate hard down level on the camera.The GSO focusers on my Newts have fairly flat bases and so when the camera is pushed home and tightened up , my tilt issues disappeared
This may not be the case for a RASA though but folk advised don’t use the tilt plate on the camera to correct tilt ( their advice worked for me )

Cheers
Martin

[AdamJL]

If you use NINA, there's a plugin (plugins are excellent!) you can download called Hocus Focus. Not only is it the best autofocuser out there, but it comes with an aberration inspector that can tell you how much your backfocus needs adjusting and how bad your tilt is and in which direction.

For the 2600s, they come with a tilt adjustment plate which you can play with using the tilt adjustment screws to push/pull three points to fix your tilt, once you know which side is impacted.

[sunslayr]

You can also use a bahtinov mask to check the corners. A tilt free camera should look the same in all four. Then if you set the same focus in the middle as the edges you will have the right backfocus. This works with a field flattener, should work with a coma corrector too, might be tricky if you have a lot of coma though.

[bojan]

That is correct, provided colimation is OK.

[Joshua Bunn]

This is how I do it...
Get to know which side of your tilt adapter corresponds to what side of your downloaded camera image. do focus runs in each corner of your chip, this will determine where each corner sits relative to the optical plane. from this, you can then see which corners are too close and too far back. Now you can adjust the tilt sensor with confidence, knowing which screw to move and in which direction.


Joshua

[xelasnave]

Thanks to every one you have no idea how your help has uplifted me. Getting this RASA to work has it's ups and downs and just when I thought I was ahead as I found that I wasn't.

I post a link to a video here that although somewhat tedious may be interesting to folk who have a RASA.
He refers to a guy who helped him so I have se t him an email to see if I can get my hands of a solution to the issues of fitting a camera etc

https://youtu.be/or7jRVgcgGE


Alex

[xelasnave]

I find your post very encouraging.
Thank you very much.
ALEX

[The_bluester]

Pretty much the way I worked it. I must do it again and really dial in mine one day.

The advantage I had was using Voyager to capture focus test images. I set up a script to do a focus run ((On a single centered star) then step outward by a given about (Say 100 steps of the focus motor) then take an image, then step in by 10 steps, take another image, and repeat that until I was 100 steps inside the "Best" focus. You can then use ASTAP to analyse the images and spit data out in to excel which can plot a graph to show where each corner and the center of the chip were at best focus. If I wanted to get really tricky I could calculate how many microns per step to work out distances as well.

[xelasnave]

Hi Paul..thinking about it maybe just knock off some metal with the angle grinder to level it up:D

I wish I still had my first wide field of the Milky Way shot with the trusty 300d canon on auto focus...the stars were a sixteenth of an inch in diameter but I just thought it can't get better than this ...priot to it was chopped up digital cameras or web cams....and when someone helped out with the suggestion to use the manual focus option I just could not believe my results...and then I got a t ring...I had arrived but find myself still running after the bus.

The RASA is for me a challenge so I am very lucky to be presented with a challenge at my stage in life..things just keep getting better.

Alex

[xelasnave]

I received a reply to my enquirey about the fitting to manage tilt and back focus from the USA..$1200 US plus maybe $200_$300 postage.

I am test imaging right now and happily moving the filter drawer close to the camera seems to have made things better..there is a pertrusion of an internal ring that means you can not insert a filter drawer unless you back it off a couple of turns, which I do, insert the drawer and tighten it up which holds the filter drawer in nicely which is good because I worry about the filter falling out as the magnet does not seem very powerful..in any event things are much better such that I do not feel inclinded to buy the fitting from the USA at this point. A simple solution is to crop the image or to work with a smaller sensor size...not ideal but at least you never realise the crook stars are there..anyways right now the stars seem ok but the cloud is coming in and out so not ideal for testing.
Alex

[floyd_2]

I’m with you re the filter drawer seeming like it could fall out as the magnets don’t seem that strong. I use an elastic band around the filter drawer. I’m thinking of using one of those hair elastic bands because they’re chunky and easier to use. Hopefully my kids won’t miss one…

Interestingly I had a tilt problem at one stage and it turned out to be those thin spacers causing the tilt. I removed the spacers altogether and tightened the whole imaging train up a little more and the problem was solved. I didn’t need the spacers after all and they were causing the tilt. I felt very lucky to have had such an easy solution.

[xelasnave]

My tilt seems better but I have a few things to attend to before I work more on tilt..last night things seemed ok but I may have to file down that bit that is in the way and go for a rubber band ... good idea as prior I was using duct tape:D

That felt on the first attachment to the scope on the RASA has me thinking that it would best be gone as in a set up where they say "width of half a human hair tolerance" has me thinking it may be unstable...

alex

[MarkInSpace]

If you are using a zwo filter drawer, there is a hex key adjustment that can tighten things up.

[floyd_2]

Thanks Mark. That'll teach me to read the doco properly. I tightened that screw up ever so slightly and it's much better. They should have had a spring loaded ball bearing there with adjustable tension.

[Shiraz]

hey Alex.

Starlight express have a really neat way of adjusting the sensor tilt to get the sensor lined up with the front plate ....using a laser pointer. They suggest a green laser, but it worked OK for me with a red pointer. It takes a bit of setting up, but in the end is waay easier and quicker than just trial and error. You need to be able to rotate the camera precisely and I used an old focuser draw tube with a 2 inch adapter on the front of the camera. Have to be a bit careful with laser safety as well..don't look anywhere near the beam
https://www.sxccd.com/support/maintenance-information/aligning-the-ccd-in-an-sxvr-camera/

Cheers Ray

[xelasnave]

Thanks Ray I will go look at the link. I have seen similar to what I think you are talking about.. your idea for holding the camera is excellent..the jig I saw required a huge thing to hold the whole camera and I was put off as finding something like that would be difficult but your approach seems much more practical.....thanks again
Alex
Alex