Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_solar_25_winners.thumb.jpg.fe4e711c64054f3c9486c752d0bcd6f2.jpg

rubbertoebooks

Prime Focus Problems - Help!!!!

Recommended Posts

I have a Skywatcher Explorer 150pl to which I have attached a Nikon D60 DSLR.

I purchased a T -Ring which on removing the eyepiece holder lets me attach the camera directly to the scope which has allowed me to take a few pics of the moon.

http://stargazerslounge.com/imaging-lunar-solar/82638-few-beginner-prime-focus-pics-lunar.html

However....:)

My problem is when I keep the eyepiece holder in, using a T Adapter to hold the camera , I can't reach focus.

Similarlily , should I want to use a barlow lens for more magnification I cannot get to focus. Focus only becomes attainable whenever I attach the camera direct through the threaded T-Ring.

Any solutions?

Thanks in advance.

RTB

Share this post


Link to post
Share on other sites

RTB

If you replace the EP holder with a low profile one, then you may be able to reach focus. Not sure if you could still focus with a barlow though. The other alternative is to move the primary mirror up the tube a little. From what I've read, a few millimetres is all it needs.

HTH

Steve

Share this post


Link to post
Share on other sites

I've shifted it over to Eqpt help. Is it that when the camera is at prime focus you are at the innermost end of the focus tube travel ? If so, then this is probably the issue. Rather than using a Barlow... try using a Nikon fit Teleconverter. This doesn't move the focus point yet works in much the same way as a Barlow. I've had good results using a 2x TC on my C80ED (on the moon at least).

Share this post


Link to post
Share on other sites

This is a common problem with Newtonians and as suggested, moving the primary closer to the secondary can help but it may be worth getting s custom adapter turned up for you to bring the whole attachment point closer to the tube.

Share this post


Link to post
Share on other sites

My problem is when I keep the eyepiece holder in, using a T Adapter to hold the camera , I can't reach focus.

Similarlily , should I want to use a barlow lens for more magnification I cannot get to focus. Focus only becomes attainable whenever I attach the camera direct through the threaded T-Ring.

RTB

I think as other's have said, that keeping the eyepiece holder in place and using a T-adapter brings the camera to far out (ie away from the OTA) to achieve focus. It will need to be the same distance from the tube as when you mount it without the eyepiece holder.

As for using a barlow, in my experience, this requires moving the camera further out, away from the OTA. I have a barlow with a T-thread on the end, which is presumably similar to yours, I think that when you fit it to the camera, you might need an extention tube between it and the focuser to be able to position the camera far enough away from the OTA to achieve focus.

I also think the lens of the barlow could be too far from the camera sensor when fitted, it might be worth dismantling the barlow and removing the middle section (if possible) to bring the barlow lens closer to the camera sensor.

I hope this helps

Share this post


Link to post
Share on other sites
I've shifted it over to Eqpt help. Is it that when the camera is at prime focus you are at the innermost end of the focus tube travel ?QUOTE]

Yep, I'm at the innermost end of the tube. It has got to be close though , when looking through the eyepiece I can feel I'm very close to full focus!!!, if I could only turn the focusers another tiny bit!!:)

Thanks for the help everyone..

RTB

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.