Focusing a webcam with a Scope

[Kerrp30]

Hello,

I have a CPC800, a webcam and a bahtinov mask and would like to image the moon. The only trouble is focus does not seem to be that great, so I bought a mask to allow me to get the focus correctly but I cannot seem to get the 6 lines you need to bring the horizontal line to the intersection of the 2 diagonal lines.

Question is how do I use the mask.

Do I

1. Get a star in the centre of my scope using an eyepiece

2. Swap over to the webcam - This is where I see no star what do I need to do?

or do I

1. Set it up during the day and focus it up on a target then wait till the moon comes around.

I use sharpcap

TIA

Paul

[Freddie]

Get the star in the middle with an EP and then move to your 17mm EP and make sure the star is exactly in the middle. Then put in the webcam and increase gain and exposure. The star will be out of focus, so adjust focus until the star is focussed as best you can. Now put on the mask and fine tune focus. The FOV is VERY small (especially when using a barlow) so make sure the star is definately in the middle of the FOV before putting in the webcam.

[JamesF]

And if you struggle to be sure it is in the centre, consider a cheap illuminated reticle eyepiece. It makes life much easier.

James