Visual Back replacement

[kon1966]

Hi guys,
have a standard Bintel 2 inch diagonal om my 8se. Does anyone know of a short visual back I can replace it with because when using my 6.3 reducer and cannon 1100d I cannot reach focus. Using a 1/14 diagonal works but the light cone is smaller.

I also have the celestron T adapter but as all know, there is a base clearance issue.

Have googled it but cannot find a replacement.

Regards
Kon

[Don Pensack]

like this?
http://agenaastro.com/baader-ultra-short-10mm-sct-female-t2-male-t-adapter-sct-t-2958500b.html

[kon1966]

Hi Don,
missed your post, will this screw onto my standard 2 inch diagonal replacing the standard tube or onto my eos T adapter.

Regards
Kon

[kon1966]

Hi all, have attached a photo of what I need. Please see photo, is there a short replacement available or even a whole new 2 inch diagonal with shorter ends. I have a 8SE.

Regards
Kon

[Don Pensack]

The EOS t-adapter. the male end is t-thread.

[kon1966]

Thanks,
I want to use the 2 inch diagonal and leave permanently on with the 6.3 reducer. I suppose there is no 2 inch diagonal with shorter tube ends available. Without the reducer it focuses, I just need that little bit extra as it is so close to focus, only 2 turns.

Regards
Kon

[Don Pensack]

The shortest 2" diagonals are the SCT thread-on variety (as in your picture).
These are usually short enough to clear the base on the 8SE.
Something you should know about the SE:
You can loosen the bolt that holds the OTA on the arm and slide it forward. The limit is when the rear cell of the scope hits the plastic cover on the arm.
If you file a deeper notch in the plastic cover of the arm, you can slide th OTA even farther forward.
Doing so gives you even greater clearance between the 2" diagonal and the base.
By doing so, I've been able to slide the OTA far enough forward that a 2" diagonal easily clears the base--even the refractor style of 2" diagonal wherein the forward-projecting tube on the diagonal slides into a 2" tubular adapter threaded onto the back of the scope.
The threaded-on 2" diagonals cannot hold a 2" filter on their front ends, typically have several millimeters less of clear aperture, and are significantly harder to rotate to the side (which makes the scope much easier to use when the scope is pointed near the horizon).
So the obvious answer is not a shorter diagonal, but sliding the OTA farther forward in its cradle. If you look closely, you'll see that the part that holds the scope is a pair of angled aluminum clamps. The plastic of the arm is merely cosmetic.
If you have a Dremel tool, the plastic on the arm can be notched a few centimeters deeper in only a few seconds, and allow you to slide the OTA forward to increase the clearance with the base.
I am not certain why Celestron chose to limit the forward movement of the scope so much, but at least the owner of the scope can rectify that.

Let me know if my explanation is not clear.
Even if it is clear and you would prefer to have a threaded-on diagonal, they are generally available from many on-line retailers.

[kon1966]

Hi Don,
done that by buying another dovetail and attaching to original so the OTA has double dovetails and is moved slightly right and then forward to clear the base. I saw that online under the name of Robs mods I think. So clearance is all good, just focus is issue as all my eyepieces and accessories are 2 inch. Do not want to keep unscrewing and screwing between diagonals.

Regards
Kon

[Don Pensack]

The 8SE has about 8" of back focus, so you should easily focus all 2" eyepieces and accessories.
So perhaps I'm misunderstanding what you need.

[mikerr]

Kon, you may find some answers in this Cloudy Nights thread. Have a look at the Baader diagonals discussed.

http://www.cloudynights.com/topic/494618-using-the-63-reducer/

I ended up machining a shorter eyepiece holder section for my 2" GSO Diagonal. Had to remove 10mm so that I could easily reach focus using the .63 reducer with a Baader 8-24mm Zoom eyepiece.

Michael

[kon1966]

Hi Don,
I looked at the bintel diagonal and found there is a thin reducer which unscrews from the front tube. It is a m42 thread so any T adapter will screw into the diagonal. What you suggested will work, Female SCT to m42 male thread which there a number of.

Thanks for your help all.

Regards
Kon