7 replies to this topic

[Cathexis]

Greetings,

 

I recently moved and know I have to do a proper collimation of my Celestron Edge 11". I do have a Hotech device, video etc.

[ My CRC 6 actually fell over in the moving van when they hit a curb! They had it standing upright loose, ready to off-load while they backed into the new driveway. But at least I had that well, well padded in a Pelican Long Storm-style case. I was using harsh language about that!!] 

 

My worry may sound silly, but I can only ask. When trying outside I used to just eyeball it by looking and then twiddling the 3 adjustment screws, it sometimes seems like those screws are getting awful loose! Is it possible I could accidentally back them out so far the 2ndary just drops loose into the main tube? That really would be a disaster!! Is this possible? Or is there some kind of locknut or washer that gaurantees the 2ndary is not just going to fall off like a muffler off an '82 Pontiac?? 

 

If this is really stupid then hey, I'd rather be foolish than full of woe!

 

TIA,

 

Andrew

 

P.S. The Edge was gingerly transported in my rear seat and in the Celestron padded carry case, but still...

 

Edited by Cathexis, 21 March 2023 - 06:35 PM.

[Keith Rivich]

When I collimated my 8" SCT I simply pointed it at a bright star and took it out of focus so I could see the offset in the stars image. I would then stick my finger in the light path so I could see the shadow on the star image. I would move my finger to align with the offset then pick a collimation screw that aligned with my finger, turn it a bit, and recheck. Continue until the star image was nice and round. Worked great. 

[Cathexis]

Wow! Well, that was a "Doh!" moment for me, thanks!  I still hope others might answer my question about potential for disaster or offer other advice but thank you for yours!

[WadeH237]

Is it possible I could accidentally back them out so far the 2ndary just drops loose into the main tube? That really would be a disaster!! Is this possible? Or is there some kind of locknut or washer that gaurantees the 2ndary is not just going to fall off like a muffler off an '82 Pontiac?? 

Yes, it is possible to simultaneously remove all 3 screws, such that the secondary mirror falls into the primary.

 

But don't go looking for trouble.  The proper way to adjust the collimation screws is to only tighten them.  At some point, all the screws will be tight, so that you can't reasonably tighten any of them further.  When that happens, if you would normally need to tighten a particular screw, you would then loosen the two opposite screws, but only by a fraction of a turn.  Just enough, so that you can tighen the target screw just a bit.

 

You do that iteratively until the scope is in collimation.  By using this technique, there is virtually no risk of accidentally dropping the secondary mirror.

[AhBok]

Once properly collimated, I have always used just 2 screws for subsequent collimation on any mirrored telescope type. This prevents the screws traveling to extreme positions. It is really not difficult to do this once you get used to it. Just choose one screw that you always leave alone. Only 2 screws are required (after the initial collimation and assuming nothing major such as after a disassembly/reassembly of the optical train.)

[12BH7]

As WadeH237 said, tighten. This works until you start to feel resistance in the screw being tightened.

 

I had to back out all the screws two or three turns on one of my scopes after 35 years of doing that. Then re-collimate.

 

I had to do a rough collimation first then do a star collimation.

 

Here's a link to the rough collimation. It surprisingly worked quite well. http://www.mira.org/...ures/collim.htm

Just make sure you know where the secondary shadow is then take it from there.

 

Then read this link. It REALLY changed my view on collimating.  https://www.cloudyni...imating-my-sct/

[Cathexis]

Bingo! ALL these replies were just what I was hoping for. Thank you, CN!!

[Nippon]

If your scope has the original screws and you use a small screwdriver that has the proper tip but a rather narrow diameter handle it is pretty hard to cause damage. I would say you want to end up with the screws firmly snug. I have seen bulged plastic secondary cells on a few Celestron C8s