xx Ash xx Posted February 21, 2013 Share Posted February 21, 2013 Hi,I'm attempting to create a DIY Bahtinov Mask...I'm using the website http://astrojargon.net/MaskGenerator.aspx to generate the template and I'm using a Helios Skywatcher 150 with the following spec:f=1000md=150mmThe total diamter of the enitre tube is 175mmJust to be on the same side as i'm a little unsure of what is meant by "Clear Aperture", can somebody a lot more knowledgable than I am advise on what numbers I should be using in the generator?Thanks Link to comment Share on other sites More sharing options...
dephelis Posted February 21, 2013 Share Posted February 21, 2013 I've come across a few differing interpretations of 'clear aperture'. As far as the Bahtinov generator goes, this should the diameter of your primary mirror, so 150mm in your case. Link to comment Share on other sites More sharing options...
xx Ash xx Posted February 21, 2013 Author Share Posted February 21, 2013 Thanks, taking into account the total diameter of my tube and including the f=1000mm & d=150mmWhen the mask is printed off, i'd expect the whole template to be 175mm wide but it isn't. It comes out to 1500mm wide. Link to comment Share on other sites More sharing options...
xx Ash xx Posted February 21, 2013 Author Share Posted February 21, 2013 Thanks, taking into account the total diameter of my tube and including the f=1000mm & d=150mmWhen the mask is printed off, i'd expect the whole template to be 175mm wide but it isn't. It comes out to 1500mm wide.Nevermind, it was me..... Sorted now !! Link to comment Share on other sites More sharing options...
dephelis Posted February 21, 2013 Share Posted February 21, 2013 Glad it's all sorted Link to comment Share on other sites More sharing options...
xx Ash xx Posted February 22, 2013 Author Share Posted February 22, 2013 No,thought i'd got it but something still isn't right.I just can seem to get the correct dimensions for the Mask.I'd made a miscalculation and the total diamater of my tube is 194mm. Therefore, my scopes spec isFocal Length =1000mmAperture =150mm (Primary Mirror Diameter)Tube Diameter = 194mm (Resulting in an Edge Thickness of 44mm)So, taking measurements into account, I'd expect the total mask diamater to be 194mm with the slits being 150mm in diamater.... However, when printed the mask is coming in at about 10mm short in covering the front of my scope.I've tried different edge thicknesses but I can't get my head round it.I'm saving the .svg file, then opening it with Inkscape, using Inkscape to save as a .png and then printing off. Link to comment Share on other sites More sharing options...
xx Ash xx Posted February 24, 2013 Author Share Posted February 24, 2013 Hi,Anybody out there that can point me in the right direction or am I reading too much into it...... Link to comment Share on other sites More sharing options...
Bizibilder Posted February 24, 2013 Share Posted February 24, 2013 Have you scaled the print on the printer? 194mm is outside the normal margins for A4 printing and the printer may be "scaling to fit") - you'll find the tick box in "Printer Properties". Link to comment Share on other sites More sharing options...
nigelg Posted February 24, 2013 Share Posted February 24, 2013 import the image into a program such as PhotoShop, then scale image to 107% save and reprint.Nigel Link to comment Share on other sites More sharing options...
glowjet Posted February 25, 2013 Share Posted February 25, 2013 You can of course use a Y mask, as plenty on here have done, just make a plastic Y to the same dimensions of the bars of the Bahtinov, will work just the same and less cutting, try one, should not take long to make and worth the experiment John. Link to comment Share on other sites More sharing options...
BargeGazer Posted February 25, 2013 Share Posted February 25, 2013 From your dimensions I think you may have the wrong figure for edge thickness. As you have both diameters for tube and aperture the thickness should be half the difference. The formula wants aperture Diameter but Thickness is difference in Radii.At least that was where I went wrong when looking at one formula.David Link to comment Share on other sites More sharing options...
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