Collimation

[Jessi]

I have a Celestron Powerseeker 114 eq that I decided to try out my new laser collimator on. I've had the scope for 3 Years and have only used a collimation cap on before. Anyway, today I noticed the secondary mirror was off. When I went to make adjustments, I discovered that the adjustment screws were all loose. Now what? I'm guessing that the adjustment screws shouldn't be loose and the mirror should be secure. I found the mirror again when looking through the focuser...that's a good thing I guess.

Any help would be greatly appreciated.

[Sureshks]

Hi Jesse,

Yes, those screws should be tightened. Or at least, they should be secure enough that the secondary mirror isn't moving and stays in alignment.

If you bring it to the next BSIG event on July 8th, we can take a look at it and try to fix the problem.

Suresh

[SEmert]

Hi Jessi, What is the focal length and the physical tube length of your Powerseeker? Just asking to verify if it is a standard Newtonian or is it a Jones-Bird Newtonian. If the focal length is way too long, like double the physical length of the tube, it is a Jones-Bird. Another sure thing to verify the type is to look in the focuser tube and see if there is a lens inside there. If the focal length somewhat matches the physical length, it's a standard Newtonian.

If it's a standard Newtonian, good news. Suresh is right that we can easily fix it at the next BSIG observing event, or you could bring it to the MAS meeting and we can easily fix it there.

If you want to continue before then, if you're seeing all the three secondary collimation screws are loose, it means that actually the center screw is loose. That one is the pivot point that levers against the three collimation screws. It mainly is used to center the secondary mirror directly under the focuser. So, look down the focuser, make sure the secondary appears pretty well lined up under it, and that it appears "round" (rotated properly), and tighten it up a bit which should tighten the collimation screws. If it is no longer centered up and down along the length of the tube, you'd then want to loosen it a bit, turn all three collimation screws in or out equally to get it centered radially, then be sure it is snug, and then you can collimate with the three collimation screws individually. But hopefully you don't have to get that far.

If there is a lens inside the focuser tube, it is a Jones-Bird Newtonian and it gets more complicated, and you'd really have to have one of us that has done it before collimate it.

[Jessi]

The focal length is 900 mm f/8. I also have a Jones-Bird too, but that headache is stored away for now. I will bring it to the next meeting. I'm not sure if I will make it to the next BSIG.

[SEmert]

Ok, I'll try to remember to bring my sight tube and laser collimator and screwdriver and allen wrenches to the meeting.

[Jessi]

Thanks! I can bring my tool bag too...make sure I have what I need.

[BradNasset]

Here is a diagram I made for someone awhile back. You may know this, but might help to visualize

Visualizing Collimation of Newtonian.pdf

.
Brad