Orion Short tube CT80 won't focus.....

[happy-kat]

when you take it apart there are two elements, this youtube is helpful and gives you info to help you with your ST80, it's a great telescope well worth fixing

https://www.youtube.com/watch?v=Ylb7xnc_03U

 

 

[Higgs_Bozon]

15 hours ago, John said:

But no extension tube ?

It is beginning to seem as if there is something amiss with the objective lens of the telescope. Maybe it has been taken apart for cleaning and one of the lens elements put back in the wrong way around ?

 

The objective lens seems to be screwed incorrectly, there's a slight tilt. It seems the person tried to screw it in the wrong way and now it's stuck, not moving. What should I do to take it out?

[Higgs_Bozon]

Update: I've managed to dismantle it properly, now what should be the correct order of the two lenses and the thin ring? I suppose the thin ring is between them but which one comes first?

Edited November 11, 2023 by Higgs_Bozon

[AstroNebulee]

1 hour ago, Higgs_Bozon said:

Update: I've managed to dismantle it properly, now what should be the correct order of the two lenses and the thin ring? I suppose the thin ring is between them but which one comes first?

Follow the video that @happy-kat posted about 4 mins in will show you. 

Lee

Edited November 11, 2023 by AstroNebulee

[happy-kat]

Also be careful to keep the small spacers that are between the lenses, but it might be your thin ring is the spacer, if it where then when you took your lenses out I would have expected the thin ring to be in-between the two lenses

This is my Orion ST80 that I took apart following that video. Lenses at the start, note the tiny spacers.

 

Edited November 11, 2023 by happy-kat

[Higgs_Bozon]

15 hours ago, happy-kat said:

Also be careful to keep the small spacers that are between the lenses, but it might be your thin ring is the spacer, if it where then when you took your lenses out I would have expected the thin ring to be in-between the two lenses

This is my Orion ST80 that I took apart following that video. Lenses at the start, note the tiny spacers.

 

Thanks for the video link, I watched and followed it, using the ring as a spacer, but just wanted to confirm, the lenses were still touching each other even with the ring in between them.... Is that supposed to happen?

[John]

24 minutes ago, Higgs_Bozon said:

Thanks for the video link, I watched and followed it, using the ring as a spacer, but just wanted to confirm, the lenses were still touching each other even with the ring in between them.... Is that supposed to happen?

No. There should be a very small gap between the lens surfaces.

The optical layout looks like this:

 

 

Edited November 12, 2023 by John

[happy-kat]

My lenses had a tiny space because there were 3 tiny spacers

If you did not have three tiny spacers when you took your lenses out and only that really fine ring then go with using that. You'll have to try your ST80 on the stars to see if it looks ok now.

There is also a video somewhere on dealing with deep scratches on a lens, if I find it I'll link it.

Edited November 12, 2023 by happy-kat