ST 80 focus problem

[den12386]

I have a Skywatcher ST 80 refractor and as it has a threaded end on the focus tube I attached my Nikon dslr with  a T ring to take a quick shot of the moon but the focus tube is not long enough to focus the image in the camera. I don`t understand why they put a threaded end on a focus tube which is to short to focus with a camera attached. Does anyone know what I need to get round this problem to achieve prime focus shots with the scope?

[RikM]

You need to add a T-thread extension tube or two. http://www.firstlightoptics.com/adaptors/baader-t2-extension-tube.html

You might want to think if it is really worth it though, the ST80 is not very good (I'm being polite ) for imaging with a DSLR. The field isn't flat and it will show lots of blue halos around stars.

[steppenwolf]

The ST80 has a star diagonal to allow you to focus with an eyepiece and this increases the light path distance. With the diagonal removed, you do need to replace this lost light path and the best way of doing this is to use a 'T' extension tube.

[steppenwolf]

Ooops, doubled with Rik.

[RikM]

[den12386]

Thanks for the help, yes the tube extenshions look to be the answer, thanks again...........Dennis

[IanL]

If you have a barlow, you can usually unscrew the lens element and use the body as an extension tube.  Might save you the cost of an extension tube if you decide the image is not up to scratch.