Precise Star Focus : Bahtinov Masks
Bahtinov Focusing Mask Generator is at
http://astrojargon.net/MaskGenerator.aspx
Using Laser Printer and Copier Transparency Film,
you can print 2-4 filters on a single A4 sheet !
Cost will be about 1$ for that !
Also contaction an On Line Laser Cutting Cie as
customlasercutting in the US or sculpteo in France
you can
ask for a Laser Cut filter and verify size on line.
For a filter 76 x 76 mm, 3mm thick black acrylic like described just
below, it would cost max. 25$ a piece ...
Examples of HP LaserJet verified settings and results (output are .svg files to print directly from inside your navigator (IE, ...) :
Case 1 : Nikon 180 mm, 1:2.8 manual
Looking like this but don't use this image (low res) and print directly from .svg !!
I just made one on LP Transparency Film !
then an artificial star test at 100% size with SonyA7s and 180 ( (APS-C mode then F= 290 mm), f:2.8, 12800 ISO at 5 m distance :
Below, same enlarged 5x
Note : very easy to remove without touching it : just pull back the lens hood :)
Test on the real sky !
Bad (L) and good (R) focus on Vega (500%) :
Part of Lyra (50% of original RAW size), DSS with 5 frames, only light images :
Lyra, M57 (100%) ... Stars to about 12.5 Mag are detectable !
Case 2 : Nikon 50 mm, 1:2.8, manual
Looking like this but don't use this image (low res) and print directly from .svg !!
General use :
![]() |
![]() |
Main line not centered ...
bad focus
|
Line centered
... Very good focus !!
|