Twistlock adaptor or diagonal replacement?

[globular]

I'm a newbie just getting to grips with my new equipment.

I want to hold my 2" eyepieces in my 2" diagonal with a twistlock or similar mechanism - rather than the 2 screw method that came as standard because that seems less secure, harder to centre and might mark my eyepieces.

Is there an adaptor that will do this?  I've seen 2" to 1.25" but not 2" to 2". And if they do exist, will it add too much to the light path making focusing harder in some cases?

Or is my only/best option to replace my diagonal with one that has a twistlock built in?

And on that note, I don't know if my diagonal (that came with the scope) is any good anyway and maybe "should" be replaced?  It's a Celestron 2” mirror diagonal #93519 that doesn't appear to be a current model so I can't find out anything about it.  My scope is a Celestron 8" Edge HD.

Advice gratefully received.

Edited August 17, 2020 by globular

[Louis D]

If the diagonal uses a compression ring, it won't mark your eyepieces.

Baader is the only brand with interchangeable barrels on their diagonals to my knowledge.

Personally, I really like the GSO/Revelation dielectric diagonals.  They do have compression rings on both the 2" holder and the 1.25" low profile adapter.

[globular]

My diagonal doesn't have a compression ring - just 2 screws that poke through the barrel and directly grip the EP nose.
I'm pretty careful and haven't marked my EPs yet; nor had any fall out; but I know the time will come when I'm all excited to change by EP to take advantage of some perfect seeing and I'll have an accident.

I've found a 2" Bresser 35mm Extension Tube that terminates in a compression ring or a 2" Altair 50mm Extension Tube that has a Positive Lock.
But it doesn't feel right to add 35mm or 50mm to the light path when I don't 'need' to. 
Am I worrying over nothing?

 

[Louis D]

Yes, you'll be moving your scope's mirror well away from its optimal design position to counteract the increased back focal distance.  There would be a touch more spherical aberration.

Alternatively, you can substitute nylon screws for the metal ones.  Probably M3 or M4 screws would work.

Edited August 20, 2020 by Louis D

[johninderby]

Deleted

Edited August 20, 2020 by johninderby

[globular]

On 19/08/2020 at 17:43, Louis D said:

Baader is the only brand with interchangeable barrels on their diagonals to my knowledge.

Louis, your comment above prompted me to look closely at my Celestron #93519 diagonal and I discovered the barrel does indeed unscrew revealing a 2" SCT female thread on the eyepiece side of the diagonal.

I've ordered a baader 2" SCT female to 2" SCT male inverter ring that will then allow connection of a 2" baader clicklock SCT onto the eyepiece side of the diagonal - giving me the very nice clicklock mechanism I was after to hold my eyepieces in place.

Thank you so much for your help.

Edited August 20, 2020 by globular

[Louis D]

2 hours ago, globular said:

Louis, your comment above prompted me to look closely at my Celestron #93519 diagonal and I discovered the barrel does indeed unscrew revealing a 2" SCT female thread on the eyepiece side of the diagonal.

I've ordered a baader 2" SCT male to 2" SCT male inverter ring that will then allow connection of a 2" baader clicklock SCT onto the eyepiece side of the diagonal - giving me the very nice clicklock mechanism I was after to hold my eyepieces in place.

Thank you so much for your help.

Sounds good.  Let us know how it works out.

The GSO/Revelation 2" diagonal also uses an SCT thread.  I screw an SCT threaded extension tube into it and then thread a TSFLAT2 field flattener onto the other end's M48 thread to flatten my refractors' fields.

[globular]

Here is my solution.

Start with 
* Celestron 2" Diagonal #93519
* Baader 2" Inversion Ring #1508020
* Baader 2" ClickLock SCT #2956220 

Remove the eyepiece barrel

Add the inversion ring

Add the clicklock

Nasty screw grip barrel replaced with nice clicklock.
And the light path is roughly the same (2mm shorter).

Thanks again Louis for the inspiration.

Edited August 22, 2020 by globular

[Louis D]

Glad it all worked out for you.