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Pages: 1 thesubwaypusher professor emeritus Reged: 07/08/04 Posts: 691 Loc: New York City vignetting       #2084379 - 12/30/07 09:33 PM Edit   Reply   Quote Quick Reply   Hey guys: I was out with my Denk IIs the other night and noticed that I had vignetting along the sides of the image in the focal reduction mode on the Powerswitch when viewing DSOs. Yet on the bright moon, I noticed that the entire image was intact in the 19mm Pans. So, vignetting on the dark images, none on the bright. Is this a product of the exit pupil? Any help would be appreciated. Thanks, Chris -------------------- 7" LX200 MAK GPS (AKA the best telescope ever made :-) 12" LX200 ACF Tak FSQ-85 (AKA - second best scope ever made :-) ETX-125 Tak diagonal T-Rex altaz mount Extender Q Celestron Edge HD-11 Televue Bino-Vue w/ 24mm Panoptics Powerswitch diagonal Dewbuster TV 2x barlow 21mm Ethos 6mm Radian 2.5mm Vixen Canon 40D Post Extras:       Derwin Skotch super member Reged: 03/11/05 Posts: 157 Loc: PA, USA Re: vignetting [Re: thesubwaypusher]       #2088377 - 01/01/08 07:13 PM Edit   Reply   Quote Quick Reply   I see you are from New York. Were you observing DSO's from light polluted skies? Vignetting is most obvious with a uniformly illuminated field like you would get with light pollution or looking at the sky before dark. Probably the light cone is being cutoff with the steeper light cone you get with the reducer. Try looking at a star with the focus off enough to see the image of the primary. Start with the star in the center of the field and move the scope till it reaches the edge of the field. Any restriction will be easily seen. Even with my large aperture binoviewer, there is vignetting when in reduction mode, but it is not noticable most of the time. -------------------- Derwin Celestron 9 1/4" SCT Meade 6" Schmidt Newtonian Edmund 4 1/4" Newtonian Siebert Echelon 35 binoviewers Denkmeier Dielectric S2 Power X Switch Diagonal Post Extras:       thesubwaypusher professor emeritus Reged: 07/08/04 Posts: 691 Loc: New York City Re: vignetting [Re: Derwin Skotch]       #2089070 - 01/02/08 01:36 AM Edit   Reply   Quote Quick Reply   Is that really your name? That's one KOOL name! Thanks for the response, Derwin. The vignetting is there, that's for certain. But not on the bright moon, that's what I don't get. And I travel to a dark site on Long Island. Chris -------------------- 7" LX200 MAK GPS (AKA the best telescope ever made :-) 12" LX200 ACF Tak FSQ-85 (AKA - second best scope ever made :-) ETX-125 Tak diagonal T-Rex altaz mount Extender Q Celestron Edge HD-11 Televue Bino-Vue w/ 24mm Panoptics Powerswitch diagonal Dewbuster TV 2x barlow 21mm Ethos 6mm Radian 2.5mm Vixen Canon 40D Post Extras:       Derwin Skotch super member Reged: 03/11/05 Posts: 157 Loc: PA, USA Re: vignetting [Re: thesubwaypusher]       #2090679 - 01/02/08 06:00 PM Edit   Reply   Quote Quick Reply   Maybe it could be a combination of the pupil in your eye being smaller than the exit pupil of the scope when using low power on a bright object that hides the vignetting when looking at the moon. What magnification and size scope were you using when you looked at the moon? -------------------- Derwin Celestron 9 1/4" SCT Meade 6" Schmidt Newtonian Edmund 4 1/4" Newtonian Siebert Echelon 35 binoviewers Denkmeier Dielectric S2 Power X Switch Diagonal Post Extras:       thesubwaypusher professor emeritus Reged: 07/08/04 Posts: 691 Loc: New York City Re: vignetting [Re: Derwin Skotch]       #2091564 - 01/02/08 11:22 PM Edit   Reply   Quote Quick Reply   I was using a 7" Meade LX200 Mak with 19mm Panoptics. Thanks, Chris -------------------- 7" LX200 MAK GPS (AKA the best telescope ever made :-) 12" LX200 ACF Tak FSQ-85 (AKA - second best scope ever made :-) ETX-125 Tak diagonal T-Rex altaz mount Extender Q Celestron Edge HD-11 Televue Bino-Vue w/ 24mm Panoptics Powerswitch diagonal Dewbuster TV 2x barlow 21mm Ethos 6mm Radian 2.5mm Vixen Canon 40D Post Extras:       thesubwaypusher professor emeritus Reged: 07/08/04 Posts: 691 Loc: New York City Re: vignetting [Re: thesubwaypusher]       #2091576 - 01/02/08 11:27 PM Edit   Reply   Quote Quick Reply   As a matter of fact, my setup is pictured in my ad to sell the Pans in the Eyepiece section of the Classifieds. -------------------- 7" LX200 MAK GPS (AKA the best telescope ever made :-) 12" LX200 ACF Tak FSQ-85 (AKA - second best scope ever made :-) ETX-125 Tak diagonal T-Rex altaz mount Extender Q Celestron Edge HD-11 Televue Bino-Vue w/ 24mm Panoptics Powerswitch diagonal Dewbuster TV 2x barlow 21mm Ethos 6mm Radian 2.5mm Vixen Canon 40D Post Extras:       EdZ Professor EdZ Reged: 02/15/02 Posts: 18806 Loc: Cumberland, R I , USA42N71.4W Re: vignetting [Re: thesubwaypusher]       #2092851 - 01/03/08 02:19 PM Edit   Reply   Quote Quick Reply   In my Denk Big Easy, the prism does not completely span across the circular metal opening on the prism shelf. This leaves a chord of open space approx 1 to 1.5mm exposed along one edge. When used with low power (wide field stop) eyepieces this is easily seen as a dark line along one edge of the fov. When used with higher power eyepieces with smaller field stops it is not noticed. edz -------------------- Teach a kid something today. The feeling you'll get is one of life's greatest rewards. member#21 Post Extras:       thesubwaypusher professor emeritus Reged: 07/08/04 Posts: 691 Loc: New York City Re: vignetting [Re: EdZ]       #2149626 - 01/27/08 04:57 PM Edit   Reply   Quote Quick Reply   Hey Ed: You say it will be along one side. Wouldn't that mean that something in the optical train is not straight? Shouldn't that line or edge, be on both sides? Mine is on the left with my 24 Pans. Thanks for your response, Chris -------------------- 7" LX200 MAK GPS (AKA the best telescope ever made :-) 12" LX200 ACF Tak FSQ-85 (AKA - second best scope ever made :-) ETX-125 Tak diagonal T-Rex altaz mount Extender Q Celestron Edge HD-11 Televue Bino-Vue w/ 24mm Panoptics Powerswitch diagonal Dewbuster TV 2x barlow 21mm Ethos 6mm Radian 2.5mm Vixen Canon 40D Post Extras:       EdZ Professor EdZ Reged: 02/15/02 Posts: 18806 Loc: Cumberland, R I , USA42N71.4W Re: vignetting [Re: thesubwaypusher]       #2149644 - 01/27/08 05:11 PM Edit   Reply   Quote Quick Reply   it appears the prism is not quite wide enough to completely span across the metal prism opening. If the edge of the prism is covered by the rounf metal on one edge, but not the other, it could show just one straight edge, yet still be squared to the optical path. edz -------------------- Teach a kid something today. The feeling you'll get is one of life's greatest rewards. member#21 Post Extras:       thesubwaypusher professor emeritus Reged: 07/08/04 Posts: 691 Loc: New York City Re: vignetting [Re: EdZ]       #2150227 - 01/27/08 10:22 PM Edit   Reply   Quote Quick Reply   Gottcha! -------------------- 7" LX200 MAK GPS (AKA the best telescope ever made :-) 12" LX200 ACF Tak FSQ-85 (AKA - second best scope ever made :-) ETX-125 Tak diagonal T-Rex altaz mount Extender Q Celestron Edge HD-11 Televue Bino-Vue w/ 24mm Panoptics Powerswitch diagonal Dewbuster TV 2x barlow 21mm Ethos 6mm Radian 2.5mm Vixen Canon 40D Post Extras:       TheRock sage Reged: 01/13/08 Posts: 303 Loc: Bergen County, NJ Re: vignetting [Re: thesubwaypusher]       #2154540 - 01/29/08 08:35 PM Edit   Reply   Quote Quick Reply   Chris, When you say a dark site sky in Long Island, do you mean compared to NYC? Thanks, TheRock -------------------- Richard -------------------- "Get busy living, or get busy dying" - The Shawshank Redemption (1994) -------------------- 11" Celestron CPC1100 GPS 18" ƒ/4.2 Truss Dobsonian - OMI Optics Post Extras:       thesubwaypusher professor emeritus Reged: 07/08/04 Posts: 691 Loc: New York City Re: vignetting [Re: TheRock]       #2171358 - 02/05/08 11:37 PM Edit   Reply   Quote Quick Reply   Well, anywhere is darker than NYC! No, it's pretty dark out there. Not better than the country but...we do what we can. -------------------- 7" LX200 MAK GPS (AKA the best telescope ever made :-) 12" LX200 ACF Tak FSQ-85 (AKA - second best scope ever made :-) ETX-125 Tak diagonal T-Rex altaz mount Extender Q Celestron Edge HD-11 Televue Bino-Vue w/ 24mm Panoptics Powerswitch diagonal Dewbuster TV 2x barlow 21mm Ethos 6mm Radian 2.5mm Vixen Canon 40D Post Extras:       Pages: 1

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