Celestron guide scope won't come to focus

[StarLord101]

I just had my celestron 80mm x 600mm guide scope out to try for the first time.... And I can't bring it to focus. Using eyepiece or Orion planetary imagery (glorified web cam). Pointing at a random patch of sky, I can't make out a single star or light from the whole range of focus. When I pointed it at something big and bright like saturn, I can find a blurry out of focus disk that covers about 1/3rd of the view, and racking the focus all the way in and out slowly and it only partially gets smaller heading towards focus, but still a ways off. This is directly into the rear opening, no diagonal and it didn't come with extensions. I don't see anything obvious to explain or visible damage, and it doesn't rattle when moved around. Thank GOD I decided to test it randomly tonight before I went into the bush relying and expecting it to guide my avx! Just goes to show you, looks can be deceiving. Saw no damage and everything moved perfectly on pre purchase inspection. I can understand maybe situations where extension is needed for camera, but is it reasonable that even an eyepiece couldn't come to focus with something branded and sold as a guidescope? It only mentions extensions when talking about guiders or cameras that I can see. If not that, could it be collimation issue?

[JayTee]

That is weird.

So you say even an eyepiece won't come into focus, correct?

The first place I would start would be to take a tape measure start where the objective is then measure to the focuser and see where 600mm occurs on the focusing tube.

Cheers,
JT

[SkyHiker]

Looking at the Celestron page for that product, it should come with an extension for focusing that you say you don't have. Could that be the issue?

[StarLord101]

Looking at the Celestron page for that product, it should come with an extension for focusing that you say you don't have. Could that be the issue?

It certainly could be, but they mention the extension to help cameras come to focus. Eyepiece doesn't either and the focuser is sized to accept eyepiece. Also, if it was mandatory to be able to focus at all with the product, I would expect to see that somewhere or that it would come with it. I got it from a very reputable shop that wouldn't sell it partial without saying so

[StarLord101]

That is weird.

So you say even an eyepiece won't come into focus, correct?

The first place I would start would be to take a tape measure start where the objective is then measure to the focuser and see where 600mm occurs on the focusing tube.

Cheers,
JT

Yes correct, that's eyepieces going directly into the back, no diagonal or extension. I'm pretty sure it had been able to come to focus when I first tried it out a few years ago but had it in storage, safely I may add.
I almost wondered if it could be a collimation issue which isn't common for refractor

[Lady Fraktor]

Even if it was out of collimation it would still be able to come to a reasonable focus just not a sharp focus.
It sounds like your focuser may be out of alignment a bit and that you at least need a short extension to use an eyepiece straight through.

If you can tell you are looking at Saturn while trying to get best focus it will be something simple to get it right.

[JayTee]

What about your measurement? Where does the 600mm point occur?

JT

[Graeme1858]

I'm with Henk.

I use a Celestron 80mm 600mm as a guide scope and it came with an extension tube, which is required to be in place to get focus.

https://www.celestron.com/products/80-m ... pe-package

Regards

Graeme

[StarLord101]

Yep, so despite no clarifying anywhere that it was required to have the extension (only mentions extension tube as an included accessory to help come to focus for cameras), I figured why waste time with complex possibilities and just test it end of story. Inserted a diagonal from my refractor and boom, confirmed it can now focus with the eyepiece. As far as using the camera with it though, I think that's a different thread because I could not get a single hint of light or stars with my camera (Orion starshoot solar system planetary imager).

[Gfamily]

The optics say that the prime focus of your scope will be 600mm behind the objective lens.
If you're using a camera (or any imaging sensor) that's where the focal plane needs to be.
However, for visual use, the eyepiece needs to be a certain distance behind that plane - how far depends on the eyepiece design, but basically, that's why an extension tube or diagonal is used if you're using an eyepiece.