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nytecam
Postmaster
Reged: 08/20/05
Posts: 5756
Loc: London UK
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As spectroscopy is my main-game I thought this a raw test spectrum in late twilight of Altair [alpha Aql =A-type star] prior to homing in on nova V459 Vul may be of interest. It shows the blue/violet flare caused by chromatic aberration [inability to bring to a common focus] of the Meade ETX-70 70mm 2-element OG. As an adjunct it also demonstates the efficiency of the Rainbow and Staranalyser gratings to a form a bright 1st order spectrum and conversely very weak other orders of spectra that are not used.
However spectro is extremely cruel to refractive optics - wonder how pricy APOs get on  Needless to say exclusively reflective optics can't show chromatic aberration 
PS: Despite my cutting remarks for OGs the spectrum of V459 Vul turned out great and confirms via the H-alpha emission this is a nova something that a non-spectro image only shows the star is just an 'interloper' 
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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+e-finder+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9+Lodestar CCDs/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-my videos
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walt r
Post Laureate
Reged: 02/13/07
Posts: 3463
Loc: Doylestown, PA
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Interesting Nytecam. Do I also see slight flaring in the IR?
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Walt
Obsession 18" f/4.45 #1370 AN/SC
MK67 Deluxe 6" f/12 Mak-Cass, Super Polaris GEM, JMI MicroMax DSC
DIY 60mm f/6 Achromat
Cookbook 245 CCD
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nytecam
Postmaster
Reged: 08/20/05
Posts: 5756
Loc: London UK
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Quote:
Interesting Nytecam. Do I also see slight flaring in the IR?
You do indeed Walt depending on the star's colour index and more evident on this M27 field eg bright F-type star above the planetary neb - the OG is presumably 'corrected' [eg in common focus] for visual ~450-650nm 
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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+e-finder+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9+Lodestar CCDs/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-my videos
Edited by nytecam (01/03/08 11:48 AM)
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DAVIDG
Carpal Tunnel
Reged: 12/02/04
Posts: 1989
Loc: Hockessin, De
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Nytecam,
APOs are nice but a Schupmann medial refractor has a couple of advantages. First it is perfectly color corrected using just simple glass so it's inexpensive to build. Second by tipping the field mirror it turns into a spectroscope. So anytime I want to check out the spectra of the object in the eyepiece I just tweak the tilt screw. Two for the price of one.
- Dave
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Homemade 'scopes 8"f/7,6" f/5", 6"f/4, 4.25" Schief. 60mm Coronagraph,60mm H-alpha system, 4.25" White-light Solar Newtonian,solar spectroscope, 4.5" f/16 Schupmann Medial refractor, 14 Stellafane awards 7 in optics
Engineering = Taking what you have and making what you need.
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nytecam
Postmaster
Reged: 08/20/05
Posts: 5756
Loc: London UK
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Thanks Dave - a true ATM scope  do you have sample spectra 
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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+e-finder+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9+Lodestar CCDs/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-my videos
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DAVIDG
Carpal Tunnel
Reged: 12/02/04
Posts: 1989
Loc: Hockessin, De
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The 'scope doesn't have a drive so no images of a spectra. I'm working a 9" version that will be driven thou. The spectra I get in the scope compares well to the ones I get in my GOTO spectroscope. The field mirror tips in both planes so I don't need a cylinder lens to spread out the spectra in both directions and the object is easily centered in the eyepiece in normal observing mode and then the mirror adjusted into spectra mode. For "fun" type spectrum viewing it works very well.
- Dave
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Homemade 'scopes 8"f/7,6" f/5", 6"f/4, 4.25" Schief. 60mm Coronagraph,60mm H-alpha system, 4.25" White-light Solar Newtonian,solar spectroscope, 4.5" f/16 Schupmann Medial refractor, 14 Stellafane awards 7 in optics
Engineering = Taking what you have and making what you need.
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