2" SCT Visual Back

[digitaldave]

Does anyone know where I can get a 2" SCT visual back? I would like to get one for my C9.25 so I can use my William Optics 2" diagonal without having to use the WO SCT threaded nosepiece, as it's a bit awkward to adjust in the field. Using the SCT threaded nosepiece, if you want to rotate the diagonal, you need to loosen the collar at the back of the scope, which can get quite stiff in cold conditions with cold hands, so it'd be much easier to have a visual back like the 1.25" one that came with the scope using thumb screws.

I've seen the WO SCT-2" adaptor, but I'm sure there are going to be cheaper ones out there. I know GSO do one, but I can't seem to find a UK dealer that sells it.

Hope that makes sense .

Thanks,

Dave.

[John]

This might be what you are after Dave:

2" SCT to Push-Fit Adapter (Female to Female) | Adaptors | Accessories | Astronomica

You do loose some of the clearance at the rear of your scope with this approach (ie: the visual back and diagonal stick out further) so just check it will still clear your mount if the scope is fork mounted.

John

[digitaldave]

John,

Thanks for that, it looks like just the thing. I'm sure the WO piece is very good, but it's twice the price of the one you linked, and unlike other parts of the optical chain, I doubt there would be much difference in use between them.

I'm using an EQ6 mount, so no worries about fork clearance .

Dave.

[brianb]

I'm using an EQ6 mount, so no worries about fork clearance

There's still the fact that the SCT threaded nosepiece gives a shorter optical path than the SCT->2" adapter so, when a 2" diagonal is fitted, the back focus distance (and consequently the focal length of the scope) will be nearer to the design value i.e. the optics will be better corrected.

The only problem with the SCT nosepiece is that it can come unscrewed, but so can the SCT -> 2" adapter.

For 11" & up scopes get the "large SCT adapter" to fit the 3.25" threads, that way you get a wider unvignetted field.

[digitaldave]

Brian,

Thanks for that, it's not something I had considered. Hopefully my EPs will all reach focus with the adaptor in place...

[John]

Brian,

Thanks for that, it's not something I had considered. Hopefully my EPs will all reach focus with the adaptor in place...

You should be fine - I used one on my old C8 and had no problems with a wide range of eyepieces. The only thing it did mean was that my F/6.3 focal reducer did not work as far as I can recall.

The Astronomica adapter has a brass compression ring fitting which is a good feature considering the price of the item.

John

[m.tweedy]

Have you considered a crayford focusser. I use one on my C8 and get much finer focus than the standard focusser on the back of the sct.

[digitaldave]

I actually used to have a Feathertouch crayford, but I got rid of it. The problem **for me** is that I didn't really need the accuracy of the two speed focuser, the regular focuser was fine for my use, which is purely visual. If I did astrophotography, I'd still have it, as it's a really well engineered piece of kit.