Jump to content
  • Join the East Midlands Stargazers astronomy community today!

    Test

djpaul

In Need of advise

Recommended Posts

djpaul

Hi All

 

Need some help with a focusing issue

I bought a secondhand Skywatcher 120ed 3 years ago ithad been upgraded with a T.S Optics R96 Focuser.

All has been great using it with a Star Diagonal over the 3 years i have had it .

However i bought a DSLR to take some shots of the moon this year and i cant get it in Prime focus.

Its very close to focus but just before it gets sharp i run out of inward focus

I have tried various extenders as people have told me i need more back focus 

But surely it if almost in focus before i hit the inward focus stop . it means the focser body must be longer than the stock skywatcher focuser?

 

Any help would be great

Paul

Share this post


Link to post
Share on other sites
Bino-viewer

This is why binoviewers need some sort of amplification (quite often anyway) to reach focus.

A bino + diagonal adds about 150mm or so to the focuser, hence back focus is all important.

 

I'm surprised you can't get a DSLR to focus as this quite a bit smaller in terms of focus travel requirements.

All i can suggest is try using a different camera. Do you have a MIL option ?

 

If not, other than using a Powermate, the only other thing to do is go to a machine shop of some sort and have the tube length cut down by the required amount.

Share this post


Link to post
Share on other sites
Graham

I thought you were going to change the focuser.?? 

You have removed the diagonal before trying the camera. 

Edited by Graham

Share this post


Link to post
Share on other sites
philjay

Are you using a diagonal with the dslr? If so take the diagonal off. Normally these scopes reach easy focus with a dslr with a short extender and no diagonal. I cant imagine your non stock focuser would be so much longer than the sw one. Just looked at TS site re the r96 focuser, it isnt much different from the sw one so you are probably using the diagonal in which case you will not reach focus as described.

Edited by philjay

Share this post


Link to post
Share on other sites
djpaul

No I'm not using the diagonal. 

I certainly do not want to cut the scope down In size.

Paul 

 

Share this post


Link to post
Share on other sites
djpaul
6 hours ago, Graham said:

I thought you were going to change the focuser.?? 

You have removed the diagonal before trying the camera. 

I was going to replace the focuser. But all shops are telling me there's no need toand it could be an expensive thing if it makes no difference. 

Paul 

 

Share this post


Link to post
Share on other sites
Graham

Fair enough. 

Not a cheap item to replace. 

Still can't understand why your scope won't reach focus. 

It defies all logic. 

Can you post up a photo of your focuser. With the DSLR attached. 

Edited by Graham

Share this post


Link to post
Share on other sites
djpaul

I'm presuming there can't be anything wrong with the 120ed as it works fine with the diagonal fitted using eyepieces. ?

Paul 

Share this post


Link to post
Share on other sites
Ibbo

As above if you post a picture of the setup with the DSLR attached it would help

Edited by Ibbo

Share this post


Link to post
Share on other sites
philjay

The ts focuser is a good one, monorail I think they call it. A touch better tgan the SW standard si I wouldnt rush to change it. As Ibbo suggests, give us a couple of snaps of the configuration thats giving you trouble

Share this post


Link to post
Share on other sites
philjay

If your down to reducing things by millimeters to reach focus then something is not right. The scope should reach focus as described, a few mm here or there shouldnt make any difference, we would be able to give better advice with pics of the of the setup

Share this post


Link to post
Share on other sites
djpaul

Problem solved.

It was back focus.

I bought one of those adjustable large extensions that you can fit an eyepiece into.

Used it without an eyepiece. Adjusted the extender and gained focus straight away.

Thanks to all that helped.

Regards paul 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.