Eyepiece And Mirror Not Aligned?

[Torutro]

Hi all!

I’m not exactly sure as to where I should post this, but since I’m a beginner with basic questions, I assume this is the correct forum.

So I’ve gotten the hang of my Celestron 130EQ over the last two months and collimated it with ease. As usual, I did a star check to see if the secondary mirror was aligned (it was not) and I brought it inside and angled it towards a lit wall for better light. When I looked down the eyepiece tube, I saw that only half the of the primary mirror could be seen and the other half was the wall of the telescope tube (photos attached).

I assumed with my basic knowledge that the secondary mirror was angled the wrong way, so I tried to adjust it until the screws began to come loose, and stopped to prevent any further damage via my lack of proper skill.

Any ideas on what exactly happened, and how I could fix it? 
 

Sincerest regards,

Torutro

P.S: I know the primary mirror isn’t collimated, but I couldn’t get the full field of view to do it properly.

 

Edited December 14, 2020 by Torutro

[Moonshed]

Hi Torutro,  What you have described is a little confusing. You say you have collimated your Celestron, what this means is you have made adjustments to the secondary mirror, using those three screws, in order to correctly align it with the main mirror. You can check this has been done correctly by looking at an out of focus star and ensuring the dark centre spot and concentric rings are centralised when you look through the eyepiece, like target rings. Perhaps you mean something else when you say you collimated it?

 

EDIT: sorry, my mistake, I thought your scope was a different type known as a Schmidt-Cassegrain, but on checking discover it’s a reflector, very different way of adjusting these. Nonetheless if it’s collimated it means the mirrors are correctly aligned.

Edited December 14, 2020 by Moonshed

[Louis D]

Can you loosen all of the secondary mirror's screws, and then see if it tips enough to point straight at the primary mirror?  You also need to ensure it is rotated such that it looks like a circle in the sight tube.  That part is fairly straight forward.

Once you have the secondary square on with the focuser (round circle) and tipped properly, tighten up all the screws little bit by little bit, readjusting at each step as needed.  Once that is done, you shouldn't need to touch your secondary again.  They generally don't shift between uses.

[Torutro]

Thanks for the advice! I’ll give it a go and try to fix the issue.

 

[Torutro]

So, I managed to physically adjust the secondary mirror holder with my hand until the primary mirror’s reflection filled up the field of view.

However, the secondary mirror’s reflection at the center of the spider vanes is still off, and when I try to fix it by regular collocation, the entire secondary mirror rotates and once again moves out of alignment.

Does anybody know why this is happening? Is it normal for a secondary mirror to become loose?

[Geoff Lister]

There is a definitive guide to collimation written by Astro Baby. If you do a search, using "Astro Baby", on this site, there should be links to the document, and other excellent advice to get you going.

The most important advice that I have gained from the experts on this site, is to adjust the secondary with the main tube horizontal, so that if anything falls, it will not drop onto the primary mirror.

Geoff

[Torutro]

Thanks for the guide, it really helped!

Somehow though, once I look down the focused tube, the edge of the secondary mirror holder is visible on the primary mirror (Circled in the photo). I figured it may be due to the tilt of the holder, but I’m still unsure as to how I can adjust it without putting everything out of alignment again. 

Is this normal to be happening? If not, how should I go about fixing it?

 

[Merlin66]

From your image the secondary doesn't look centred to the focuser tube....

Look at the large outer circle, this is the inside of the focuser. The outline of the secondary should be circular and concentric with the focuser.

Your secondary looks too far to the left and too low.

Can you see this?

[Louis D]

Good point about the secondary centering.  Do you have a sight tube?  If so, insert it so far into the focuser that the end of it looks to be the same size as the secondary when viewed from the peephole.  It will be obvious if the secondary isn't dead centered in the sight tube view.  There are generally nuts or screws/bolts at the ends of the spider vanes to adjust the X/Y position of the secondary over the primary.  There is also generally a single bolt with nuts at the center of the secondary spider to adjust the Z position (toward/away) of the secondary relative to the primary.  After loosening and adjusting this one, you may have to make sure the secondary is still square with the focuser again by rotating it before tightening everything down again.