You are not logged in. [Login] Entrance · Main Index · Search · New user · Who's Online FAQ · Calendar Observing >> Lunar Observing Previous   Index   Next   Threaded   Pages: 1 Tim sage Reged: 08/04/04 Posts: 349 Loc: North of Toronto Viewing the Corona and Color in the scope       #2338837 - 04/19/08 06:17 PM Edit   Reply   Quote Quick Reply   I was out last night viewing the moon Something that I havent done in some time. I just purchased a new refractor ed doublet earlier in the day.I dont have any real experience with refractors and when viewing the moon there was a green ring almost all the way around it. I was using my Panoptic 24 and 15 eye pieces. I figured that something was wrong with the refractor possible as it was showing colour (my belief was that I shouldnt be seeing any) I went in today to the dealer to tell him I wasnt happy with the optics and he had asked if there was a CORONA around the moon. I think that there may have been. He told me that even his Televue refractor shows colour when viewing the moon with a corona. My question is has that been your experience as well? The dealer did offer to take back the refractor and give me my money back no questions. I opted to order another one and see if that made a difference. I am wondering If I may have taken back a perfectly good refractor? -------------------- Vixen Sphinx sxd Coronado PST.Vixen Porta Mount Canon dslr, Neximage, MX5c Camera Vixen Super Polaris Mount Nexstar 9.25 gps Stellarvue 78 Blackhawk refractor 8" Meade f6 sct thats going to get deforked. 6" Meade sct Newtonian ota Televue Panoptic eyepieces, binoviewer 8' dome Post Extras:       revans scholastic sledgehammer Reged: 09/26/05 Posts: 811 Loc: Fitchburg, MA Re: Viewing the Corona and Color in the scope [Re: Tim]       #2341728 - 04/21/08 07:13 AM Edit   Reply   Quote Quick Reply   If your refractor was an achromat (instead of an apochromat) then there is going to be a fair amount of color fringing around bright objects such as the moon. You can try using a fringe buster or minus violet filter. These filters will make the fringing much less prominent. There used to be a device, probably available only used nowadays called a Chromacor that would largely eliminate color fringing in achromats but the device was expensive... and you had to know which of several types to buy... Rick Evans -------------------- Rick Evans http://www.freewebs.com/revans_01420/ Post Extras:       Tim sage Reged: 08/04/04 Posts: 349 Loc: North of Toronto Re: Viewing the Corona and Color in the scope [Re: revans]       #2342579 - 04/21/08 03:49 PM Edit   Reply   Quote Quick Reply   thanks for the response Rick. The refractor was a doublet and supposed to be an APO but seemed to perform like a Achromat. Its gone back to the manufacture and I will get another one to see what its like. Possible the one I had was out collimation or something. Based on the responses (or lack of them) I guess that people with apo refractor dont see color when viewing the moon when a Corona is present. -------------------- Vixen Sphinx sxd Coronado PST.Vixen Porta Mount Canon dslr, Neximage, MX5c Camera Vixen Super Polaris Mount Nexstar 9.25 gps Stellarvue 78 Blackhawk refractor 8" Meade f6 sct thats going to get deforked. 6" Meade sct Newtonian ota Televue Panoptic eyepieces, binoviewer 8' dome Post Extras:       desertstars Deja moo Reged: 11/05/03 Posts: 30032 Loc: Tucson, AZ Re: Viewing the Corona and Color in the scope [Re: Tim]       #2342620 - 04/21/08 04:08 PM Edit   Reply   Quote Quick Reply   What is meant by "corona" in this context? Was your dealer discussing the aura of refracted light sometimes seen around the Moon due to high thin clouds? If so, even my reflector shows that color to some degree when the clouds are present. You would know this was the case because the ring of color can usually be seen by the naked eye alone. -------------------- Tom W. SVP8 'She turned me into a 3-legged Newt' EQ Ralph, the All-Purpose 102mm Refractor Under the Desert Stars Alcohol and calculus do not mix. Please don't drink and derive. Post Extras:       Tim2723 The Moon Guy Reged: 02/19/04 Posts: 5121 Loc: Northern New Jersey Re: Viewing the Corona and Color in the scope [Re: desertstars]       #2343226 - 04/21/08 09:05 PM Edit   Reply   Quote Quick Reply   Hi Tim, Sorry for the sparsity of responses. I read your post as being somewhat academic since you'd already taken action. As I'm sure you know, there are any number of kinds of atmospheric phenomena related to the Moon; halos and such. They can, of course, show color, and if you were looking at that then there's no problem. Chromatic aberation (the defect I think you're alluding to) normally shows itself as a violet margin touching the bright edge of the Moon, or in extreme cases, as a violet haze across the FOV. It's not usually green, and that kind of stumped me. I'm not sure what kind of optical defect would cause a green ring. I've had a refractor wildly out of collimation, but never saw green as an optical defect. Did this happen in your Blackhawk as well (or is that the scope with the problem?). -------------------- The crwth will set you free! Post Extras:       Da Bear sage Reged: 11/21/06 Posts: 499 Loc: Kali-Forn-Ya Re: Viewing the Corona and Color in the scope [Re: Tim2723]       #2345813 - 04/23/08 01:17 AM Edit   Reply   Quote Quick Reply   In an achro, if you move you eye rearward or forward a few mm and the color changes or disappears, than that is CA. I have seen green CA on a Vixen 80mm while lunar viewing, very pronounced in fact. Baader makes a CA filter that is wonderful for stopping CA on the moon. Da Bear -------------------- Telescopes are instruments of hope and faith. Hope that a better, clearer and brighter universe can be observed. Faith that we can bring these discoveries back to our small planet and create positive changes for all of it's inhabitants. Edited by Da Bear (04/23/08 01:18 AM) Post Extras:       Pages: 1 Previous   Index   Next   Threaded   Extra information 0 registered and 0 anonymous users are browsing this forum. 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