Focusing the new way

06:25 5/8/2009 UTC

Focusing is a very important task while preparing to take a good astrophoto. I say it is the hardest part if you want repeatedly a good focus, at least with my equipment. Nebulosity2 has very good routine for fine focusing and I've gotten very good results with it, but it takes time to confirm the best focus. Seeing, filters and star brightness also varies the absolute measures of focus from night to night. Enter Bahtinov mask. This clever focusing aid generates three bright diffraction spikes around a star. When these spikes cross each other symmetrically, the telescope is focused. And this is not affected by seeing in any way, so repeating good focus from night to night should be easier and faster. Of course it's cloudy here, so I'll have to wait to test it in practise. I bought mine from Kendrick Astro Instruments, but this should be relatively easy to do it yourself also.