how to build your own bathinov mask

while i'm waiting for my new finderscope to arrive, i tried to build my own bathinov mask

When i took those images of jupiter last summer, i had a heck of a time focusing the scope correctly. A bathinov mask should help get a correct focus, although (i think) it only works with deep sky objects.There are a couple of sites on the internet that offer free and downloadable instructions on how to build your own mask. So I downloaded a bathinov mask in pdf format and printed in on regular paper and then glued that onto some cardboard. But it's such an intricate pattern, that i immediately messed it all up : )

I've put the source file in my public folder at me.com. Here's the link: http://public.me.com/baierfamily - the password is "nexstar" and there's a folder called "Bathinov mask".

By the way, here's what the mask looks like:

Your're supposed to attach this mask to your telescope and take a couple of shots with your DSLR with different focus settings. Once the image appears like a concentric star, then the scope it supposed to be focused correctly. Here's how its supposed to look like:

I then read on cloudynights.com that someone had had the same problem cutting out the shape and instead printed the whole mask on a transparent sheet. So the next day i printed the mask at the office and just had to cut out a nice circle - which proved to be much less challenging : )

I then used some wooden sticks with added duct tape for extra thickness that went through the two holes on the top and that's how the mask looks "hung" over the optical tube:

And here's just the mask by itself:

The only thing that's missing now is to actually go out and test the thing. I hope that once it gets a little warmer or once i get my remote control setup up and running, that i'll be able to report on how the mask works.

Important addition: If you are planning to use your mask on a cold night where you'd use a dew cap then make sure you cut out your mask to be big enough to fit onto the dew cap. The particular mask that you see pictured here fit perfectly on the scope, but was to small for the dew cap - it "fell" inside when hung over the dew cap. So i had to print out another one of the suckers : )