Alan Lehman 8" Newt homebrew and hand-figured optics; Moonlite focuser; Atlas EQ-G TV 2x Barlow; 5x Powermate Basler acA640-100gm; Astronomik LRGB 2c; XAGYL wheel
The most incomprehensible thing about the Universe is that it is at all comprehensible....Albert Einstein http://www.trevsastronomy.webs.com/
Quote:Another curious thing is that when I image Mars and Saturn on the same night, within and hour or so of each other, my Saturn has no spurious effects (rind/onion), but my Mars will have the edge-rind. I might have missed this in your article, but I wonder if the issue has to do with the albedo of the particular planet (under certain seeing conditions) to a degree too?
Bart Declercq Orion Optics 300mm F/4.8 Newton Teleskop Service 15cm F/4 Fotonewton William-Optics 80mm F/7 APO Mesu-mount ASI120MM & SBIG STL-4020M http://www.bartcentral.be/
1986 Compustar C11 ASI120MM, Flea3, DMK21, Toucam Astronomik Type2 + IFW Wheel ST-4/C90, Nikon D70s
Quote:There are many excellent images that do not show this edge effect, for example this fine image from Damian posted this morning:http://www.damianpeach.com/mars1112/2012_03_14rgb01.jpgSo it seems clear that the edge effect is not intrinsic in mars imaging.cheers, Bird
Steve Verba 76mm Tasco 10TE 180mm Astro-Physics StarFire 20in. Obsession 15 x 15 Rolloff (Backyard Observatories)
Quote:The concept that this effect is diffraction related makes no sense. Is it ONLY Damian Peach's scope that is immune?
Emil author of AutoStakkert! 2.1 (check out the beta versions!). Webcam Astrophotography - Deepsky, ISS, Sun, Moon & Planetary Images,
Quote:Quote:The shape and intensity of the first diffraction ring is very sensitive to the collimation, seeing and tube currentsI took the wavelength-dependence RGB image I had in the website article that prompted this thread and boosted the contrast of the outer ring before pasting back the unadjusted planetary disc itself. What is interesting is the fact that where the dark artefact is worse the outer ring is the faintest. Does this suggest that the artefact might be related to miscollimation of the scope. I need to try this on other images and see if this still holds.Martin
Quote:The shape and intensity of the first diffraction ring is very sensitive to the collimation, seeing and tube currents
Quote:I'm currently doing some analysis in matlab on these images, to try to find the location of the diffraction pattern
Quote: Defocus will make it worse. And sadly thats where seeing comes into play as the atmosphere can defocus during the capture. The problem will be magnified at longer wavelengths. Smaller apertures will be more effected. And finally a large obstruction (sorry SCT guys) also makes it worse.
The Hole in the Trees Skybox
CPC1100, SXVR-H694, ASI120MM
Imaging automation by Sequence Generator Pro and FireCapture
Quote:These were the distances that I found: Blue: 47Green: 53Red: 59Infrared: 74
Quote:"However I think the main thrust of this thread is about *other* effects, maybe coming from places that we can control - miscollimation, ghosting in the filters, poor seeing (ok we can't control that one :-) ) etc.
Quote:So the answer is you airbrush it away?
---John 14.5" Dall-Kirkham w/Royce optics Celestron 11 AP140EDF,TEC140,Tak FS60-C ZWO ASI120MM and ASI120MC DMK21AU618.AS SBIG ST-10XE http://www.spacescenes.com