30 replies to this topic

[ChristianG]

I probably shouldn't have taken the scope apart and cleaned the primary mirror without checking this first (...)

Well, I might agree with you here. Unless you know what you are doing and have significant experience working with optical instruments, there is a very good chance that the alignment of the system is messed up. And that the mirror coating is damaged. Our local astronomy store (now gone) used to have a star diagonal whose mirror had been 'cleaned' by its former owner. It was perfectly fine, ended up completely ruined. They used it as a cautionary example.

 

But many of these big dobsonian telescopes do indeed require some extension tube. This was the case for a 10" Sky-Watcher dobsonian purchased by a local club here. Took quite a while for them to figure it out because they were always trying it at night.

 

All you have to do is to look at something far during the day, like the top of a communication tower, and see how the whole thing works. Good luck!

 

--Christian

[Nut2But]

I have nothing to add here. Hopefully the extension tube gets you squared away. This is such an awesome hobby. Would hate to see you throw in the towel.

[WillR]

The first thing I will say is wait until warm weather and have another go at it. It’s winter in Buffalo, not a good time to mess with a telescope or try to sell it. You put is aside for 4 years. Wait another few months.

 

Now to your issues. Unless the azimuth bearing is binding on something, this is a simple fix requiring some lubrication. I use simple soap. Make a solution and spread it on the bearing surface and let it dry.

 

As for not reaching focus, if it does need an extension tube, there is a simple way to find out. Slide the eyepiece partly out of the focuser or even completely out and see if the focus gets sharper. In that case you need an extension tube. Don’t fault the seller, because many of these come without them, and different eye pieces like 2”, or 1 1/4”, or zooms can have very different focus points.

 

As for collimation, you just have to learn it. I figured everything out by reading books, this forum, and trying things out. I have a club, but they are only meeting virtually and the members are very spread out, so I have had to learn all this on my own. And there is a lot to learn. But it’s worth it. It’s a great hobby so don’t give up just yet.

Edited by WillR, 15 February 2025 - 12:52 PM.

[A Star Geezer]

Just a thought is the focuser coming all the way out? mine did not at first till I adjustede the tension screw

[39.1N84.5W]

Just try to get focus on the moon firstly.

Can you post pictures of your telescope?

[TheBrianNebula]

You mentioned taking the objective out to clean it, so I wonder if you're having the same problem I had last summer after I did so. I complained on here about stars focusing to funny shapes even though I had it perfectly collimated, and somebody told me I had "pinched optics", because I'd overtightened the rubber pads holding the mirror on. I loosened them and fixed it, easy.

 

Can't help you with the azimuth bearing though.