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Olivier18
newbie
Reged: 09/12/09
Posts: 3
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hello,
I work on the problem of coma for newtonian telescope for my studies. I work more precisely on coma correctors.
And i need some caracteristics about a Coma Corrector (focal lens...) in order to complete my theoretical study. I asked to Baader but they didn't answer me.
I have a model (ROSS), but i would like to compare real measures with theoretical measures. SO i need caracteristics about a paracorr.
thanks
Olivier
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csa/montana
Wild Spirit
Reged: 05/14/05
Posts: 40281
Loc: montana
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Olivier, Welcome to Cloudy Nights! Glad to have you join us on the forums.
I'm not sure exactly what information you are looking for on the Paracorr; but here's the information on it.
Paracorr
Other members will be along to assist you with your questions shortly.
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Carol
AstroTech 16" Dob (Thanks ASTRONOMICS!)
Vixen 80MF/AstroTech Voyager
Masuyama's 7.5, 15, 25W, 35mm,
Pentaxes; 5XW, 7XL, 10XW.
14mm Meade 4000 UWA
TV Panoptics; 22, 35
DreamCatcher Dobservatory, #2
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MitchAlsup
super member
Reged: 08/31/09
Posts: 185
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"Telescope Optics" Rutten and vanVenrooij give the optical prescription for a 2 lens Ross corrector on page 147
"Reflecting Telescope Optics" Vol I Wilson gives the optical prescription for a 3 lens Ross corrector on page 343 and a 4 lens Wynne corrector on page 349. A 3 lens corrector with one aspheiric by Faude and Wilson on page 350; all for paraboloids.
Gascoigné has produced Coma correctors with "Schmidt"-like (4-th order surfaces) plates in 1 plate, 2 plate and 3 plate versions.
Paracorr has been described as a pair of doublets, and appears to be an acromatized 2 lens Ross, perhaps with some adjustment in Spherical--although this does not show up in:
http://www.televue.com/images/accessories/Paracorr%20Graphs.jpg
Which does show uncorrected spherical showing up at F/5 and faster.
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Olivier18
newbie
Reged: 09/12/09
Posts: 3
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Thanks for your answers.
I will be more precise.
I studied star distortions in coiner with and without a 2 lens ROSS corrector with a newton telescope. I have beautiful theoretical stars. I used some focal lens values for the corrector. But I don't know if these values are good.
I would like to measure real star distortions created by coma with and without a coma corrector. So i will buy a coma corrector (ROSS), probably a Televue paracorr. And i would like to know focal lens used in this corrector in order to do again my theoritical measures with these values and to compare them.
I hope, i was comprehensible
Olivier
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star drop
Guilty as Charged
Reged: 02/02/08
Posts: 16368
Loc: Snow Plop, WNY
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Hi Olivier and welcome to Cloudy Nights.
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Ted
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Olivier18
newbie
Reged: 09/12/09
Posts: 3
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Someone can help me ?
thanks
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sixela
Postmaster
Reged: 12/23/04
Posts: 10872
Loc: Boechout, Belgium
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Quote:
Which does show uncorrected spherical showing up at F/5 and faster.
Nothing like what a Ross would produce. You just have to compare an MPCC to a Paracorr at high power to see which one sticks out like a sore thumb (actually, the SA generated is often just enough to compensate some in some eyepiece designs at fast focal ratios).
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400mm f/4.46 self made Dobsonian on Tom Osypowski equatorial platform
Orion Starblast (114mm f/4 reflector, Alt/Az)
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Jim Romanski
scholastic sledgehammer
Reged: 01/02/05
Posts: 844
Loc: Guilford, Connecticut
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Olivier
I don't think you're going to find anyone but Al Nagler with the exact specs/formula for the Paracorr. I think several people have privately reverse engineered it to see for themselves how he does what he does but I'm not sure that it's appropriate for them to share that with anyone in an open forum.
There was an interesting thread about Mike Lockwoods very fast telescope discussing possible designs for a new type of coma corrector that you might find helpfull:
Mike Lockwood's 20" F/3 Telescope in S&T
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Jim
17.5" Dob "Project"
13.1" Coulter
8” Cave
NP 101 on a CG-5
25x100 binos
Naglers, Ethos, etc.
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