Helical Focusers - Does the camera rotate as well?

[UBoat]

I'm setting up an ultraportable imaging rig and considering the Televue TV-60. Can anyone tell me if an imaging camera would rotate with the helical focuser? Or whether the coarse focus drawtube would change the orientation?

Thanks, Peter

[bojan]

Depends on design.. but yes in general.
However, in those cases camera orientation is adjustable independently.

[phomer]

Peter,

It depends on the design, you will need to ask the manufacturer.

If you need one for a camera you should also consider whether it can be motorised as that is likely to be very important.

Regards

Paul

[astro744]

The TV-60 is a visual telescope and designed for use with a star diagonal which remains in a fixed orientation but can be rotated by unlocking the compression clamp. When focusing it does not rotate either in coarse focus (draw tube) or helical fine focus. It can be used photographically in both prime focus (T-Adaptor+T-Ring, no eyepiece or star diagonal) or afocal (Digiscoping with star diagonal and eyepiece in place) modes. (Eyepiece projection and Tele-extending i.e. Powermate would likely be possible). Visually the TV-60 is a joy to use offering great views at both low and high power with suitable eyepieces.

Note the TV-60 has a 1.25" draw tube and visual back and therefore requires a 1.25" T-Adaptor. When photographing remove the diagonal and use T-Adaptor. The camera will remain in a fixed orientation locked in place by the compression clamp that will hold the nosepiece of the T-Adaptor. You will also need a T-Ring to match your camera body mount.

There is no appreciable vignetting with an APS-C sensor (may depend on what T-Adaptor you use) but likely with full frame. There is however slight field curvature but this is to be expected for such a short visual doublet. The TV-60is has a field flattener to correct this for photography (see below). I do not know if a 1.25" field flattener (if exists) could be used for photography and a 2" version simply wont fit.

Tele Vue brought out the TV-60 and TV-60is, the latter being a photographic version with 2" focuser and field flattener. Unfortunatley the TV-60is has been discontinued which is a pity because it had a lot to offer for the photographer. You may be able to find one used.

See the following links for some info on the TV-60is:

http://www.televue.com/pdf/literature/Tele%20Vue-60is%20Operating%20Guide.pdf

http://www.robertreeves.com/TV-60isEldorado.htm

http://www.billsastro.com/Astronomy/Equipment/Telescope%20Folder/TV-60is/TV-60is.htm

[UBoat]

Many thanks for those suggestions and to Astro for the links and detailed reply. That lays my concerns to rest! Also I'll look out for the TV-60 IS as I'm considering the Orion Thin OAG in my search for portability and it just might work on the TV-60IS.

Peter

[astro744]

No worries. Here is the link to TV-60 manual:

http://www.televue.com/pdf/literature/Tele%20Vue-60%20Operating%20Guide%20Booklet.pd f

and all other Tele Vue manuals from this page:

http://www.televue.com/engine/TV3b_page.asp?id=11