Home-made Bahtinov, how accurate ?

[badgers]

Dear SGLers,

I've made my own Bahtinov Mask using the template online from:

astrojargon - Bahtinov Focusing Mask Generator: Overview

I plugged in the standard numbers for fl 750 and 150mm aperture for my skywatcher.

Obviously I can't cut as accurately as a laser and there are a few ragged edges.

Will this matter much when using the mask ?

Any advice on how I might mount it over the scope ?

I was thinking of cutting it circular to completely cover the aperture with three tabs to velcro over the edges.

[hemihaggis]

looks good , give it a try

[glowjet]

Looks fine to me, its a pain cutting all those slots, although fine sharp edges are better, you will still get the same result. You could have tried a Y shape first of the same dims as your bar widths, lets more light through and works just the same. For fixing I have used an embroidery loop which is wooden and adjustable, stuck some Velcro sticky back velvet on the inside and tacked the mask to the front with three brass pins, when it was a fit. The embroidery loops come in 1 inch increments from 4" up to quite large, available from your local Haberdashers or Arts & Crafts. If your loop is slightly to large then just glue some felt blocks on the inside. HTH

John.

[badgers]

Good advice, thanks!

[en51nm]

I did the same and made a DIY one. Mine is by no means perfect but still works a treat :-)

[Bizibilder]

That will work fine. For my own I use two methods of attachment. Firstly I have a mask with four foam blocks (about 3cm cube in shape and size), these are positioned to just push over the end of the scope (SW 200P). The second has a foam ring about 2cm thick that is glued to the mask and just fits over the scope (80 and 120mm refractors). Both methods work well.

[badgers]

Just tried my little creation on venus....

Worked an absolute TREAT.

Really chuffed... only cost me £1.40 for a craft knife : )

[kernowstargazer]

This might sound really dumb but what are they used for?

[Psychobilly]

They provide a method of determining precise focus by generating a line which moves across an "X" and is centered when your focused...

Peter

[malc-c]

This might sound really dumb but what are they used for?

To get the focus spot on...

You place it over the front of the scope, with the scope pointed at a bright star. You get this sort of image when viewed or photographed

If the focus is out the center line is above or below the intersection of the other two... you adjust the focus until the center line is in the middle like the image above

[Freddie]

You can use a bit of free software "Bahtinov grabber" to get it spot on perfect.

[kernowstargazer]

Cheers for that guys ive been wondering what they were used for for quite a while.