Finderscope + webcam - where/how to focus?

[iceman (Mike)]

I want to have a webcam in a spare finderscope, so I can use it for aligning the telescope with the DMK in the focuser at a long focal length..

That is, the webcam + finderscope will have a nice wide field of view in which I can centre the planet (for example), and it then appear in the long-focal length view with the DMK.

Ultimately, I can then hopefully guide using the webcam + finderscope to keep the planet centered when I haven't bothered with accurate polar alignment.

I know Bird (Anthony) does exactly this.

So is there any trick to it?
I've got a Celestron 6x30 finderscope that I want to mount to my 12".

I got my old ToUcam out, unscrewed the eyepiece end of the finderscope and held the ToUcam up against it (during the daytime), and I couldn't recognise anything that looks like what i'm pointing at. I found that by taking off the 1.25" adapter of the ToUcam, with the eyepiece off the finderscope, I can hold the ToUcam up to the end of the finderscope and find that the focus point is about 5mm out from the end -when focusing on an object about 2-3 metres away.

I can't get it to focus on something further away, probably because I don't have an adapter or any way of ensuring the light path is hitting the ToUcam.

How do you focus it in this arrangement? Where should the focus point be for an object at infinity (ie: stars and moon)? Where does the ToUcam need to be placed?

Thanks

[[1ponders] (Paul)]

Interesting challenge Mike. I've only been successful using a finderscope (Stellarvue) that could have eyepieces changed, (ie has a 1.25" holder built in). But, I had to add the lenses of a barlow to get to focus. It wouldn't come to focus with a normal illuminated reticle either. Using a Focal Reducer didn't work either.

In your situation you may find it necessary to create some sort of bracket to hold the ToUcam, with it's original lens, to shoot afocally.

[Dennis]

Mike

With all my refractors, to focus close for terrestrial objects using a DSLR, I have to add extension tubes.

To focus at infinity, I remove the extension tubes thus moving the DSLR inwards, so you need to move the ToUcam inwards.

This is the same with my Mewlon and C9.25. To focus at infinity, the Primary/Secondary spacing is at a minimum and to focus on terrestrial objects, I have to increase the Primary/Secondary spacing using the focus knob.

Cheers

Dennis