The problem is that the diffraction spike diverges from single line (near the bright star center) into two lines with increased distance proportional to distance from the focused bright star center. The problem is not that dimm stars have small diffraction spikes and bright have large spikes, that's obviously pretty normal. I may also try to capture diffraction rings of a defocused star (though the secondary offset should make the circles not being round at this fast F/3.6 speed).Īt the moment I am still "convinced" the problem is in spider vanes being not in-line. I may also try to focus in mid/half position from center of the image to the image edge (this pre-zero light (test) ) was done with precise focus, but in the middle of the field. I may be able to increase BFD next time by a 1mm and see. What I may be able to check next time is the backfocal distance (though we precisely calculated I need camera adapter of some 21.79mm which ASA produced for me because I got OAG from ASA too). and the infinity doesn't fit the 2" clamp very well - there's (big enough) wobble making a use of precise infinity useless. Using infinity is not easy as I can't do both tasks - look into the infinity and use the hex allen keys to turn the collimation screws. Gmalits - I have checked the collimation now (if it lasts after driving 220km) and it is "almost" OK checked with tuBlug Howie Laser. Thank you guys for now, I asked ASA on their opinion. I'd like to make a real first light this year. Please, let me know what you think, I really need exact and precise answer and proposed solution. Here is the full sized image, ignore the vignetting of the window, that will be fixed today on my camera: I very much hope it's caused by improper collimation and not by some other mechanical problem of my astrograph (I have both hands "left hands" so I can't fix anything myself without a visit to specialized laboratory - someone with mechanical skills). I do own, already, all CatsEye tools from Jim Fly and all tools from Howie Glatter so I know it's not perfectly collimated (infinity always shows a residual error, howie shows "almost OK"). So far I did not touch secondary nor tested axial error of the focuser (I simply trust ASA ). I have touched collimation only slightly, only of the primary mirror. In my pre-zero light first night of testing new AG in the field, I made few tests to see how the ASA really works. I am a new user of N-series astrograph, more precisely, I am a newbie user of Newtonian system at all (so far I've been imaging with refractors and cassegrains only) though I find myself already to be an experienced astro imager.ĭo you know what is the exact root of this issue? I can see double reflection on diffraction pattern around bright stars.
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