Finderguider focusing help

[1981suede]

I'm tearing my hair out trying to achieve focus with my PHD, SPC900 and 9x50 finder. I just can't figure out what I'm doing wrong. Can anyone with this setup help with settings etc? Exposure, gain etc. Also, how far out should I have to unscrew the focus in the finder?

I thought I would try to focus the moon using sharpcap as that should be easy it being so bright, but no. I just get a bright fuzzy ball on the laptop. Arrghh, so frustrating. I normally give up quite quick as I hate wasting the minimal clear skies we get. I can't even see a star on the screen.

Someone please help

[ollypenrice]

A guest was using one of these last night and had to take the front lens right out to its very limit to fnd focus.

Olly

[themos]

Which adaptor are you using to mate the finder to the webcam?

[1981suede]

A guest was using one of these last night and had to take the front lens right out to its very limit to fnd focus.

Olly

Thanks Olly, I shall give that a go.

Which adaptor are you using to mate the finder to the webcam?

I am using a DIY adapter made from foam pipe lagging. I have a 1.25" adapter for it which fits snugly into the lagging. I then push that into the finder so it is level with the end of it.

[themos]

Ok, what I would do is put the webcam in then unscrew the front lens as much as poss, take an exposure, then screw it in half way, take an exposure, then screw it in all the way, take an exposure. Frame a distant streetlight or Venus if you can. The different blobs should tell you which way focus lies.

[1981suede]

Ok, what I would do is put the webcam in then unscrew the front lens as much as poss, take an exposure, then screw it in half way, take an exposure, then screw it in all the way, take an exposure. Frame a distant streetlight or Venus if you can. The different blobs should tell you which way focus lies.

So you think I should take an actual image rather than monitoring it using sharpcap? Can you make any suggestions for exposure/gain settings etc? I've not had any luck finding a point of light as small as venus to be honest. The moon is a struggle

[themos]

I was thinking you could shoot long exposures but you probably can't. Ok, then, start by pointing it at something close, less than 1 meter away, then something further and so on. You should be able to tell if the image is getting any sharper. If nothing works, the webcam is too close to the lens, so either work it further away or unscrew the front lens.

[1981suede]

Cheers, I shall give it a try. just trial and error I guess. no reason to suppose it won't work at all just need to get it right.

Oh, I see you are just down the road from me!

[themos]

So I am!

[themos]

remember, the image can't be formed any closer to the lens than the focal length of the lens. I think the lenses in these finders are about 175mm focal length (or is it 185mm?)