ST80 and QHY5II spacing question

[Skipper Billy]

I am setting up an ST80 and a QHY5II mono for guiding with PHD2 piggybacked on my ED80.

It seems that I need to have the draw tube all the way out to the stops plus an 80mm (approx) extension tube to get focus. 

Does that sound right ???  It will make a long flimsy tube and prone to movement I would have thought !!??

Might I be better off converting my SW 10x50 finderscope????

Thanks in advance.

[Uplooker]

Most people unscrew the lens from a SW Barlow and use that as an extension tube.

Ian

[johnrt]

Most people unscrew the lens from a SW Barlow and use that as an extension tube.

Ian

Exactly what I do, the ST80 / QHY5 combo is a tried and tested combo, don't worry too much.

[lensman57]

I am setting up an ST80 and a QHY5II mono for guiding with PHD2 piggybacked on my ED80.

It seems that I need to have the draw tube all the way out to the stops plus an 80mm (approx) extension tube to get focus. 

Does that sound right ???  It will make a long flimsy tube and prone to movement I would have thought !!??

Might I be better off converting my SW 10x50 finderscope????

Thanks in advance.

Your ST 80 was never designed for imaging or guiding for that matter, it is a terrestrial scope and hence needing a diagonal. You need to replace the missing length of the optical path of the diagonal with an equivalent extension tube.

A.G

[Skipper Billy]

Thanks guys.

[red dwalf]

Think I used a 63 mm t2 extension tube, about a fiver from astroboot .

[Skipper Billy]

Quick update for anyone doing the same thing - a Barlow with the lens removed isnt long enough - the minimum extension required is 60mm - 80mm gives a deeper seat for the camera.