WTB: 2" Visual back for SCT with 1.25" adaptor

[VinSnr]

Hi,

SCT <-- 2" SCT diagonal <---2" eyepiece <--- DSLR camera

IMHO, you don't need a 2" diagonal even you do eyepiece projection. The 2" diagonal will just add more aberration to your image.

For prime focus:
SCT <-- SCT to 1.25"/2" adapter <-- 1.25"/2" T-Adapter <-- T-Ring <-- DSLR
or
SCT <-- SCT to T-Thread <-- T-Ring <-- DSLR

For eyepiece projection:
SCT <-- SCT to 1.25"/2" adapter <-- 1.25"/2" T-Adapter <-- 1.25"/2" Eyepiece Projection Adapter with eyepiece <-- DSLR

Anyway, ScopeStuff do sell them ( http://www.scopestuff.com/ss_adt2.htm ) or you can ask Astro Bargains to get it for you.

Have a nice day.

The reason why the diagonal was used is to make the whole setup as secure as possible. He uses a Orion camera clamp to mount the camera onto the eyepiece. Using the diagonal, the eyepiece and the camera will be vertical with the CG of the eyepiece & camera inline with the CG of the diagonal. This will also removes flexure and it is very firm and secure. The only "weak point" is between the diagonal and the eyepiece because that point uses a compression ring to tighten but as the below picture shows, the eyepiece is always pointed upwards, so no issue on that



If we use the straight-through method, the resulting setup will be pretty long and I am not sure how nerve-wrecking it can be with the camera at the end pointing downwards! Furthermore it will be neck strain to look into the viewfinder.

[weixing]

Hi,

He uses a Orion camera clamp to mount the camera onto the eyepiece

Why use the Orion camera clamp for DSLR?? Hmm... using afocal coupling on a DSLR?? IMHO, afocal coupling is best for compact camera and DSLR should use eyepiece projection instead. Also, IMHO, the problem using those clamp is that it's difficult to align the optical axis of the eyepiece to the camera lens. For afocal coupling, IMHO it's best to use compact camera and those adapter eyepiece design for this purpose, such as William Optics Digital Camera Lens eyepiece.

If we use the straight-through method, the resulting setup will be pretty long and I am not sure how nerve-wrecking it can be with the camera at the end pointing downwards! Furthermore it will be neck strain to look into the viewfinder.

Ya... It's a bit long and to be honest, I was quite worry about it initially, but it's turn out to be more stable than I thought... I even mount my quite big size video camera on my previous MCT using afocal coupling to video the Moon, Jupiter and Saturn with quite good result. I was quite surprise that the single screw of the barlow can hold the weight of my video camera and the WO-4337 adapter eyepiece... but of course, you still need to be very careful. Anyway, I don't recommend using the straight through method for those using those camera clamp.

Now using a Newtonian, eyepiece projection with DSLR is quite unstable if use a 1.25" T-Adapter on my 1.25" eyepiece projection adapter, so I now use a 2" T-Adapter on my 1.25" eyepiece projection adapter and the setup was more stable. By the way, to solve the neck strain issue when looking into the viewfinder of DSLR, I use a right-angle viewer on my DSLR.

Have a nice day.

PS: Sorry for the hijacking your WTB thread... will transfer to a new thread if more discussion is needed.

[VinSnr]

Why use the Orion camera clamp for DSLR?? Hmm... using afocal coupling on a DSLR?? IMHO, afocal coupling is best for compact camera and DSLR should use eyepiece projection instead. Also, IMHO, the problem using those clamp is that it's difficult to align the optical axis of the eyepiece to the camera lens. For afocal coupling, IMHO it's best to use compact camera and those adapter eyepiece design for this purpose, such as William Optics Digital Camera Lens eyepiece.

Because the 2" 30mm 80 degree rpd eyepiece fits into the lens of the Canon DSLR like a glove! No need any adaptor. Totally no vignetting. And it works very well.

This setup was done in the past because couldn't get hold of the T-rings, T-adaptors, etc. So this is the easiest way out. Now that he has the T-rings, T-adaptors, of course the better way is to just do prime. And he doesn't have the right angle viewer also.

I already know all his constraints before I comment because it was me who borrowed him all the required parts.

[wucheeyiun]

I would actually recommend the Vixen flip mirror diagonal with the straight thru portion to screw on a t adapter...for any dslr.

This will reduce the distance between the camera and the telecope, then reaching to focus will not be an issue.

You can still use the 1.25" eyepiece for tracking purpose.

So in this case you will still need a compression ring 2" visual back for sct.

[weixing]

Hi,

I already know all his constraints before I comment because it was me who borrowed him all the required parts.

Oh... so you give him a "push" into the Astrophotography "black hole"... ha ha ha

Have a nice day.

[yanyewkay]

Hi,

I already know all his constraints before I comment because it was me who borrowed him all the required parts.

Oh... so you give him a "push" into the Astrophotography "black hole"... ha ha ha

Have a nice day.

no lah.. actually I asked to be pushed in..
It has been something i wanted to do all along

[VinSnr]

I would actually recommend the Vixen flip mirror diagonal with the straight thru portion to screw on a screw on t ring...for any dslr.

This will reduce the distance between the camera and the telecope, then reaching to focus will not be an issue.

You can still use the 1.25" eyepiece for tracking purpose.

So in this case you will still need a compression ring 2" visual back for sct.

as usual, I do not encourage the use of compression ring to hold diagonal when you have a DSLR behind. It's just too risky. If you have a refractor, then there is not much choice. But when it's a SCT, why not make use of those SCT threads by using a proper SCT diagonal which could screw on securely?

Imagine this, I used to clamp a 1.25" diagonal and a Pentax 5.2XL on my WO 66mm. After the mount (EQ mount) has turned many times, I noticed that the diagonal started slipping especially when the mount moves into some awkward angle due to the weight of the diagonal and the Pentax eyepiece. What's more if you have a 2" diagonal and a DSLR behind?

[yanyewkay]

I would actually recommend the Vixen flip mirror diagonal with the straight thru portion to screw on a screw on t ring...for any dslr.

This will reduce the distance between the camera and the telecope, then reaching to focus will not be an issue.

You can still use the 1.25" eyepiece for tracking purpose.

So in this case you will still need a compression ring 2" visual back for sct.

It's ok, I can reach focus now with a off axis guider without problem. I've tried it already. The distance is good, any closer and my cam body hits the focussing knob of the SCT.

[VinSnr]

I would actually recommend the Vixen flip mirror diagonal with the straight thru portion to screw on a screw on t ring...for any dslr.

This will reduce the distance between the camera and the telecope, then reaching to focus will not be an issue.

You can still use the 1.25" eyepiece for tracking purpose.

So in this case you will still need a compression ring 2" visual back for sct.

It's ok, I can reach focus now with a off axis guider without problem. I've tried it already. The distance is good, any closer and my cam body hits the focussing knob of the SCT.

I should have given you the T-adaptor that night. Off axis guider is good only if you intend to guide, if not a T-adaptor is better.

Remember to cover the top hole of the off axis guider (or simply insert any eyepiece into that hole), if not stray light will get into that guider.

[yanyewkay]

yah i'm having a hard time guiding by hand thru the eyepiece..

I'll just stick to the SCT threaded diagonal then.
(got 1 offer but a bit over my budget, need to save a bit more before buying it from him)