Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_supernovae_remnants.thumb.jpg.0a6deb4bf0886533629e2bdc08293bc9.jpg

Thommy

Collimation of an imaging setup

Recommended Posts

I collimate my Maksutov-Newton without the imaging train (filter wheel, off-axis guider, guide camera and CCD camera). First, I collimate the secondary mirror with a laser collimator, then the primary mirror with a modified Kroupa. Visually this works like a treat, but when the imaging train is installed the focuser flexes a bit depending on target. How do you solve this? Do you somehow collimate with everything attached?

Thanks,

/Thommy

Share this post


Link to post
Share on other sites

Since the flexing depends on where the scope is pointing, and this changes during the night, there's really only one solution: throw money at it and upgrade the focuser.

Share this post


Link to post
Share on other sites

Of course, you're right, but right now that is not an option. I'm looking for a "second best" solution. Now, for the first time I tried to collimate with all the equipment (minus CCD) mounted. I placed the telescope in a "typical" direction for imaging. Actually, there was a significant miscollimation, but if this relies on the new setup is not clear.

I thought this was an issue experienced by many imagers - surely not all use the best focusers available. I'm a bit surprised that there are no more responses.

/Thommy

Share this post


Link to post
Share on other sites

Do you have the possibility to "tighten up" the focuser? SkyWatcher focusers can be adjusted to become stiffer. This could possibly improve the flex situation.

Another option is to use extension rings. If you normally need to have the focuser tube half way out, then adding a short extension, you can have the focus tube longer in, and it may be stiffer.

Edited by wimvb

Share this post


Link to post
Share on other sites

Thanks Wim,

Yes I adjusted the focuser to be as stiff as possible. I have the Skywatcher MN190 where there is a retractable part of the focuser. This added a lot of flexure, so I drilled two holes in the foucuser to secure the retractable part with screws. Even so there must be some flexure remaining in the focuser.

/Thommy  

Share this post


Link to post
Share on other sites
3 hours ago, Thommy said:

I have the Skywatcher MN190

I'm very interested in this scope as my next imaging upgrade. Can you show what modifications you made to the focuser?

On 02/11/2018 at 13:07, Thommy said:

a modified Kroupa

Just curious, but what's a "Kroupa"? Google only came up with prof. Pavel Kroupa.

Share this post


Link to post
Share on other sites

Sure, I will post some pictures, but is travelling a lot these days, so it will have to wait. I will not forget, though. There are a lot of threads on replacing the MN190 focuser, but that's because it it a very cumbersome task where a lot of people have failed.

Sorry, it is a "Krupa" collimator - my fault. It works really good. Mine is made so I can use it as it is, looking into it, or I can put a webcam onto the collimator which has the advantage that I can see the changes in collimation live, while adjusting the primary.

/Thommy

  • Thanks 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×

Important Information

By using this site, you agree to our Terms of Use.