250px flex tube primary mirror

[dcwales2012]

Hi,

Doing the out of box collimation of my new 250px flex tube, but I cant see any of the primary mirror clips in my cheshire, or collimation cap, is this normal on 10" scopes. Secondary was so far out, it was in another county, thankfully its now aligned.

Laser collimator says mirrors are aligned, as does cheshire.

I just want to check everything is how it should be.

David

[mdstuart]

Try a star test. Go for Polaris...defocus both sides of focus using a high power eyepiece.

If you see nice round disks with a reflection of the spider and little circles both sides of focus you are as good as it needs to be for visual use....IMHO...

The clips are just out of view on my 250px solid tube...

Mark

[dcwales2012]

Hi Mark,

Thanks for taking the trouble to reply.

Good to know the primary clips are out of sight, is the norm on a bigger dob.

David

[Avocette]

On a 250px solid Dob there are six clips which are all 'just visible' when you look through a 35mm film canister as a cheap collimating cap (find canister which just fits focusing tube, cut bottom half off, drill small hole in centre of lid). They're not visible if you look through a 'collimating eyepiece' (Cheshire with sight tube and cross wires) which has a narrower field of view.

[Guest]

Cant see it in my 250px either

[HIP3802]

The clips are just visible in a collimation cap for my 250 flex - but it is often a struggle to get them there. As Mark suggests, a star test might be a better indication of collimation than the clips.

Martin

[dcwales2012]

Thanks for replies.

Have done a star test and happy with results, just curious  why I couldn't see clips and wondered if it was the norm with 250px. The collimation cap didn't  give any further insight, so Its just one of those things.

[Moonshane]

it's important to be able to see the whole secondary mirror to ensure this is central and rounded in the drawtube. to do this I put a piece of paper in between the primary and secondary and then it's not possible to see the clips of course. with most fast scopes, you need to use an extension or pull out the cheshire a bit to see the whole secondary.

http://stargazerslounge.com/topic/186348-collimation-tip/

[dcwales2012]

Thanks for link.

I placed a red sheet of card directly below focuser, and a piece of green card between the sec and pri mirrors. Out of the box  the secondary was too far down the tube so altered accordingly. I then collimated with Cheshire and laser,but I will definitely give extending the Cheshire a go.

Thanks again.

[Stargazer_00]

My 14 inch doesn't even have clips