Bahtinov Source

[groberts]

Can anybody direct me towards a Bahtinov mask for a 50 mm guide scope - external dimension 58mm.  Alternatively a comparable DIY version.

Thanks, Graham

 

[PeterCPC]

You can make your own if you want http://astrojargon.net/MaskGen.aspx?AspxAutoDetectCookieSupport=1

Peter

[Tinker1947]

Guide scopes don't need to be pin sharp, some softness of focus helps the guiding.....

[glowjet]

If you want to experiment, try using a "Y" mask. This gives the same effect as the Bahtinov type, without blocking too much of the light. You can construct the "Y" out of wire, or thin black plastic strip, the gauge or width of strip you will have to experiment with to give the best result, but set off with something like 1.5mm or a 1/16".

I seem to recall the story of one Astronomer, who forgot to take his mask with him on an imaging expedition, cut a thin Y twig from a nearby bush, which worked well. The ingenuity of Astronomers knows no bounds  

[SilverAstro]

There is also the X mask (aka "Carey" or "Bow tie") similar to the Y, but mechanically slightly more robust being two diametrical tapes /bars /rods which can be under tension, with less chance of tearing the Y if you want to make it out of card.

Nice description of one implementation here :-

http://synergous.com/flatpress/index.php/2012/05/16/the-bow-tie-focus-mask-an-hybrid-diffraction-mask/