Astro Camera Not Focusing

[Alkaid]

Hi everyone,

I'm posting for a mate of mine who is not on the forum.  He's getting into Astro as a hobby and I recently sold him a Celestron 150mm F5 newt.  He bought a 1.25" USB Astro camera from a retailer and is having issues with focus.

He tells me that he is unable to focus on Venus - I have a feeling that there is not enough focus travel but with myself being a visual only guy, I haven't a clue what he needs to do.   Does he need an extension tube?

He has no issues focusing with a standard visual eyepiece.

Thanks for looking - Steve

[happy-kat]

Hi, is he running out of inward focus travel or outward when he is trying to reach optimum focus? 

[Alkaid]

I'll ring him again now, he said he's got 'good travel both sides' - which leads me to believe that focus should be perfectly achievable so that's why I'm a bit puzzled....back soon...and thanks.

[Astrosharkey]

I never had enough out focus with my Newt, just use an extension tube or a parfocal ring on the camera.

[Alkaid]

Thanks, I do think that he's got muddled up and actually does not have enough out-focus.  

[Bruce Leeroy]

If he has a barlow lens with removeable lens he could use the body of the barlow as an extesion tube. I've been known to stack 2-3 barlows like this to achieve focus.

[Alkaid]

Excellent, I had not though of that and it will get him going at least.  I'll get him to try it on a distant terrestrial object now.

[rickwayne]

If it still doesn't work, they could try it on a closer terrestrial object too -- I hear of more problems with Newts not having enough inward travel than outward. If they can achieve focus on something close-up but not far away, that's the prob.

If they have a DSLR available, they could take the lens off, hold the body up to the focuser, and see if they can achieve focus with that. Quick way to see what you've got without tubes or having to look off to the side at a computer screen.