Got my Chesire, I think the collimation is out slightly

[acharris77]

Hey all, I had my chesire eyepiece and today I put it in my scope to finally check my collimation, I think it is out slighty but not sure if it enough to make a difference. Below is a pic through the chesire if someone could take a look I would be greatful:

Not the best pic I know, but looking the crossair going across, the chesire seems to be a bit lower than the line, and the dot in the middle is out. Is it worth collimating this?? Thanks.

[RobH]

Hello Anthony.

Yes, your collimation is out, and yes, collimating it will make a big difference

Cheers

Rob

[acharris77]

Thanks for that, I have checked the 3 mirror clips visibility and they appear to be pretty equal and visible when looking down the focuser, so I think I would be right in assuming that it is only the Primary I would need to adjust, also I used Astro-baby guide and measured the vanes and they are equal distance.

Just want to check, also do you undo the locking screw first then slacken the adjuster or the other way around. thanks.

[RobH]

Undo the locks first Anthony.

You want to get everything looking dead central.

If your collimation is out, although it won't affect the brightness of the image, it will affect the detail.

Cheers

Rob.

[Jason D]

Anthony, refer to first attachment. You need to pay attention to the cross-hairs (cyan), primary mirror center spot reflection (yellow), and the cheshire/sight-tube combo pupil hole reflection (red). Adjust the secondary mirror to line up the cross-hairs with the primary mirror center spot reflection (cyan+yellow). Then adjust the primary mirror until the pupil reflection is aligned with the center spot reflection (yellow+red). When finished, you should get something similar to the second attachment. Good luck!!!

Jason

[albedo0.39]

I agree with Jason... primary and secondary are out .. but a fix is only a few turns of a screwdriver away !

Follow the advice, take your time and enjoy !

Steve

[acharris77]

Hey all, I have been having my first try at collimating tonight thanks to the wonderful advice given on this Forum. Anyway here is my attempt, though I am not sure of the secondary is far too offset, even though F5 scopes have an offset. Pic below:

Advice be appreciated. Thanks.

[Chris H]

Does not look quite right. Have you looked at Astro Baby's web site Astro Babys Guide to Collimation

If your finding that your going around in circles mess everything up and start again from the beginning. You'll get there.

[Jason D]

The photo is not clear enough to see whether you have the cross-hairs aligned with the primary spot and whether you have the primary spot aligned with the cheshire pupil reflection.

However, one clear misalignment in the photo is your sub-optimal placement of the secondary mirror under the focuser. You have what is known as rotate/tilt secondary mirror error. In your case, the secondary silhouette (dark shadow encircled in cyan color) is elliptical and not pointing in the primary mirror direction. It should be circular and pointing towards the primary mirror -- see my avatar.

Jason

[acharris77]

Hey thanks for the replies, but not fully sure what it means above. So I got to go back and re-adjust the secondary using the 3 screws on the front till I move it back to the center or until I get the shadow into a circle???? Hoping I will get there, but thanks for advice for a 1st time collimator.

Also I have read Astro-baby's guide and think I will go back and hopefully get it aligned all up (though not got faith at the moment)

[kniclander]

Also I have read Astro-baby's guide and think I will go back and hopefully get it aligned all up (though not got faith at the moment)

keep the faith. there are probably lots of people benefitting form this thread. me amonsgt them.

[Doc]

Ant can you see that the black area on your photo is not circular it's eliptical, what you need to do is rotate or tilt the secondary until that black shadow becomes circular.

[sgazer]

I'm following this thread with interest too having just tried to collimate my 150p with a cheshire. My secondary shadow is not quite circular either, but if I tilt it to make it circular, then the reflection of the paper ring is not aligned on the cross hairs. Adjusting the secondary to align it on the cross hairs then makes the shadow oval again.

[sgazer]

actually, my collimation looks like this one from astro baby's guide, so it might be ok for a fast scope

[acharris77]

Well I had another attempt and I think things look a bit more aligned and centered as shown below in the pic, the shadow is more round and center of the primary:

Hope this should be ok now. Thanks for all the help and advice, and hope the pics help people who are following this thread about collimation my errors and mistakes help other users to get there collimation set.

[TheThing]

This is about the clearest, most concise guide to collimating on the web. Watch thru it a couple of times and then have a go yourself and you should have it cracked.

[acharris77]

Thanks I have viewed it a few times and astrobaby guide printed out, this is closest I can get the black shadow to a circle and looking at Jason D post #5, I dont think I am that far away, just wondered if I should mess more or leave it and try it on a clear night and star test. Thanks.

[storebror]

I'm really glad you posted this Anthony because the replies and the photos have been really helpful - I only collimated my last scope twice and hated doing it - I was never really sure I'd got it quite right. I have yet to collimate my Skywatcher 150!

[Jason D]

Thanks I have viewed it a few times and astrobaby guide printed out, this is closest I can get the black shadow to a circle and looking at Jason D post #5, I dont think I am that far away, just wondered if I should mess more or leave it and try it on a clear night and star test. Thanks.

Anthony, your last photo looks great -- not perfect but great. I would advise to stop at this point at enjoy your scope.

Here is some info I posted on cloudynights.com sometime ago that might be of interest to you.

First reading: The 2nd and 3rd posts of this thread

Telescope Reviews: Concise thread about autocollimators+improvements

Second reading: All posts on the first three pages of this thread

Telescope Reviews: Useful info about secondary mirror alignment

Jason

[Jason D]

Here is an animation from one of the two threads I referenced in my last post. I put together this animation to show how the secondary mirror silhouette (dark shadow reflection) changes/follows the movement of the secondary mirror appearance under the focuser.

The primary mirror direction in the animation happens to be in the right/bottom (or 4:30 o'clock) direction.

Jason

[acharris77]

Well I took the scope out tonight for a test drive after collimating her, and I have to say that even though it is not perfect, the difference is great. I had some better detail on saturn and saw some banding and the shadow across the planet from the rings.

Though seeing werent allowing me more than my 10mm with my 2x meade barlow, as using my 3x barlow I was pushing it as though I could a larger disc, I was losing more detail, than using the 2x to give a sharper image. Also the star test was OK, as the disc was more airey with better concentric circles than before, so I am quite happy except for the fact the moonlight killed the DSO's, never mind though.

[johnkirkpatrick]

great thread very helpfull