focus help

[nightfisher]

Hi all,

managed "second light" with my old evostar yesterday (at long last)

the scope performed perfect but when i inserted the spc900 at prime focus i could not get a true focus, as im new to this i could use some pointers/advice........its got me thinking the 120mm evo might not be suited to imaging! any tips on getting the focus sorted, thanks in advance:icon_confused:

[nightfisher]

Just an after thought, when trying to image with the above set up do you leave the diagonal mirror in place or remove it and fit spc900, and will an ir/uv filter help with focusing

[simon84]

I'd remove the diagonal from the setup personally as it can add unwanted flexure in the imaging train.

Was the focuser racked all the way out? If so an extension tube should help you here, next time your out, even in daylight, aim at a target and then slowly pull the camera out of the focuser drawtube until you achieve focus, then a quick measure of that distance will tell you how far you need to extend.

The cut filter will help with imaging but not focusing, it will also keep the sensor in the camera free from dust.

HTH.

[nightfisher]

focus tube was not all the way out, will keep at it try a few things, i have a meade no; 8 filter in place more as a dust shield but gonna get a ir/uv to replace it.

[ollypenrice]

I can't see why a diagonal would add more flexure than an extension tube, an idea which only recently came to me. In fact it might reduce it by putting less of a moment on the draw tube since the camera would be closer to the objective. However, I was thinking about guiders at the time and for imaging the optical confusion of a diagonal is not wanted.

Olly