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ambro

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About ambro

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    Nebula
  1. You can platesolve online http://nova.astrometry.net/uploadand sync telescope manualy.
  2. I have MN190. The advantages are lack of a spider, lower coma, flat field. Collimation is more difficult because you have to align three optical elements.
  3. DSS dosen't have dark scaling feature. Another software withn dark scaling is PixInsight http://www.pixinsight.com/tutorials/master-frames/index.html#Dark_Frame_Scaling_Considerations.com/tutorials/master-frames/index.html#Dark_Frame_Scaling_Considerations
  4. Some programs has dark frame scaling feature: http://www.cyanogen.com/help/maximdl/Dark_Frame_Calibration.htm
  5. From left: - Velour - At the bottom - black paint with acrylic mat with talcum powder, at the top - the same plus a black matt spray on top - At the bottom - black paint with acrylic mats on top of the same plus a black matt spray on top - Matte black spray plus talc - Black matt spray - Fumed sheet Numbers mean average reads from pipette. Looking straight ahead: an angle about 45 degrees: an angle of about 15 degrees: Velour achieved the best results Source: http://www.forumastronomiczne.pl/index.php?/topic/7537-ma%C5%82y-test-wyczernienia-tuby/
  6. Mercury, Moon, Jupiter, Mars, Venus from 11.10.2015
  7. Helo, Star test is easier for SCT because central obstruction is concentric. Fast Newt has big offset. If you defocus too much you will see offcenter shadow from secondary. I am using central mask bigger than SM (about 70mm for 63mm SM diagonal) to move shadow at center for star test time. With mask you can adjust main mirror correctly. Cheshire or barlowed laser will show the same results. Examples from aberrator: No offset small offset big offset Clear Sky, Robert
  8. I think it may be clouds or fog, dew etc. In case of small dust (without flats) it is good to use dithering and median stack method. If you have cooled cam with low dark noise it is better to dither and do not add darks.
  9. Field around Polaris. Previous shot was near Pleiades. Both images are from the same sesion. I have to make longer exposures with better focus and guiding.
  10. My last results of collimation. Not best, but stars shapes are good. I didn't have time to setup guider. Telescope was not cooled completely and there was some clouds. Examples are from Canon APS-C sensor. I will use 2/3" Sony chip (ATIK 16HR). I think my current collimation will be sufficient. Flat from image: Curvatre map: Flat on ceiling: Clear Skys, Robert
  11. Hello Gents, In my previous post my offset calculation is the same like yours 2.99 x 1,41 = 4,2mm. My current offset is 4.2mm at telescope. I have almost even illuminated field. (I used double side adhesive tape). I have made more accurate calculation with (equations from http://www.telescope-optics.net for Newton) Results bellow: H is distance from SM to focal plane and S is distance from primary to secondary , f=S+H. I don't have telescope at home. I dont know H value but I aproximate it is about 230 mm. It is simple to measure S (distance from PM to SM = focuser axis. It's mean offset should be about 3.7 mm along mirrored surface. If it is true, my offset is now only 0.5mm too big. I don't know if I was so accurate. My current flat looks good. I am not sure data and equations for this calculation. Probably PM is biger than corrector (>190mm), native focal lenght of mirror is slightly longer than 1000mm, it is MN. I think good way to know correct value would be measure offset in right working scope (Per friend scope for example ). I asked Orion USA (Orion MN 190 version is almost like Skywatcher) about offset. They said it is old product and not produced from years. I don't speak English well. Maybe someone form UK could phone Orion USA Support. Offset is responsible for even iluminated field: http://www.cloudynights.com/ubbthreads/showthreaded.php/Cat/0/Number/4242330/page/0/view/collapsed/sb/5/o/all/vc/1 Quote from http://www.telescope-optics.net/newtonian.htm "Offsetting Newtonian diagonal flat doesn't influence image quality, but evens up field illumination and makes collimation easier, by centering the flat in the focuser opening (for near-minimum size diagonal flat, offsetting may also prevent a small light loss at the field center)." Wrong offset is not directly responsible for oblong stars at corners. I haven't made test shots. Yesterday weather was verry good but wife ..... Maybe tomorrow .
  12. short axis = 63mm long axis = 63 mm x 1,41 = 88.83 D is most important for me, then A or C
  13. Helo Olivier, Thank You for sharing experience. Barlowed laser projection will be helpful to check offset away from focuser. I don't have this central spot at SM. Could some one measure location of the spot and longer axis of spot eclipse?. This data is required to make paper template and paint spot on secondary.
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