KerryR
Carpal Tunnel
Reged: 12/05/07
Posts: 2642
Loc: SW Michigan
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It's most likely the Petzval element is not collimateable-- it's set in it's position, and all the other elements are collimated to IT. This means the scope collimates in the normal way. It MAY be more sensitive to collimation errors-- My Genesis (f5) sure seems to be, even though the front element is quite 'long'. (On TV scopes the Petzval element is not collimateable).
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Kerry
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Eddgie
Postmaster
Reged: 02/01/06
Posts: 7951
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I have owned two Vixen 140s and had no need to ever collimate them.
That being said, I was lucky becuase those scopes COULDN'T be collimated from what I could see.
The Televue Petzval scopes are not at all difficult to collimate. The rear element is fixed, and the front element is the only thing that can be moved. Is not any harder to collimate than a normal scope though.
The color correction with even normal glasses can be good, but not great.
My Vixen 140 had far less color than my 6" F/8 achromat. It was probably about like a 4" f/10 achromat when used visually. Maybe a little worse, but again, not as bad as the 6" f/8 achro.
I would expect the f/5 152mm scope would have slighly less color than a 6" f/8. The system will probably be similar to a 6" f/10.
Drawbacks are this: Heavy for aperture. Not MUCH shorter than an f/8 system. Don't cool down fast, and you will see the quality of the image improve as the scope cools. At least that was the case with my Vixen 140. It might be happening with my TV 101, but it is a much smaller telescope, so harder to see I suppose.
Regards.
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Celestron CGE 1400
Astro-Physics 6" f/8
Celestron EdgeHD C8
Antik AR1/Revenge Plates/Heartless Voodoos
The night sky is my mistress. She seduces me away from all other lovers.
Edited by Eddgie (09/02/09 12:57 PM)
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Eddgie
Postmaster
Reged: 02/01/06
Posts: 7951
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Well, that is not totally true. The Televue scopes don't use "Normal" push-pull screws. Instead, they simply have three pinch screws. It is a crude arrangement. It works though, and it is pretty simple to do. Sometimes the cell can shift a bit when you tighten the screws, so you have to fuss with it a bit maybe, but it still takes less than 5 minutes to do.
No Petzval I have seen on the market allows the rear element to be moved though. So the only collimation availble is usually the front lens. So I don't think Petzvals would be hard to collimate.
If the rear element is badly out of alignment though, it indicates some manufacturing defect.
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Celestron CGE 1400
Astro-Physics 6" f/8
Celestron EdgeHD C8
Antik AR1/Revenge Plates/Heartless Voodoos
The night sky is my mistress. She seduces me away from all other lovers.
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GShaffer
Carpal Tunnel
Reged: 02/28/09
Posts: 1560
Loc: Bogart, Ga USA
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Considering the NA120 is likely just like the NA140 in that there are no collimnation adjustments available (fixed lens cells) it is a good thing you never had to collimnate it 
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So the question at hand is, how much more difficult is collimation of a Petzval refractor over that of a normal refractor and (more importantly) do owners of lower priced Petzvals have problems with this?
I had a Vixen NA120 which is also a petzval design. While not as expensive as the Tele Vue scopes, it is slightly more costly than the Antares. I never had any issues with collimating this scope as I never had to. I traveled all over MI with it and it held up just fine. I have also not heard of anybody else having problems either. Hope this gets you headed in the right direction.
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20" MidnighTelescope f/5
8" f/15 Achro(project),AR6, C11, Parallax PI-250
ED102SS, FL102S,NA140SS,R200SS, 80mm NighthawkII w/TMB Fluorite Optics, SV70ED, AT66ED
LXD75, Mini-tower, GPDX, ASGT, LXD650, GM-8, GM-100,GM-150EX, G11, GM-200, Gemini G40
4" portable AP convertable 44" or 70" pier
MidnighTelescope 12.5" F/5 Dob
Bogart GA
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Eddgie
Postmaster
Reged: 02/01/06
Posts: 7951
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Funny thing.. I have owned several scopes with non-collimatable cells, and the ones that came that way never NEEDED collimation.
All of them were Vixen (Or Orion by Vixen), or Celestron (the older CR150).
They all came to me in perfect collimation, and I after my entire ownership, never NEEDED collimation.
Hmmmm. What that tells me is that you CAN build a telescope and not NEED to provide a provision for Collimation.
If fact, I think this is why Televue seals the collimation lock screw tips of their refractors. I believe that they are of the opinion that with normal usage and handling, they won't NEED collimation. Oops, they seem to be wrong about that.
To me, I guess the feeling is that if it CAN move, it WILL move, and that means you have to have adjustments.
If it is designed so that it CAN'T move and you ensure that it was collimated when it left the factory, it SHOULDN'T move unless you bend the tube, in which case the only REAL way to fix the problem is to straignten the tube.
At least that is the way it seems to me.
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Celestron CGE 1400
Astro-Physics 6" f/8
Celestron EdgeHD C8
Antik AR1/Revenge Plates/Heartless Voodoos
The night sky is my mistress. She seduces me away from all other lovers.
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GShaffer
Carpal Tunnel
Reged: 02/28/09
Posts: 1560
Loc: Bogart, Ga USA
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I dont disagree with that.....Once my 140 cools down I would say its perfect, pinpoint to the edges, flat, very little color etc. and it has been hauled around a LOT.
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20" MidnighTelescope f/5
8" f/15 Achro(project),AR6, C11, Parallax PI-250
ED102SS, FL102S,NA140SS,R200SS, 80mm NighthawkII w/TMB Fluorite Optics, SV70ED, AT66ED
LXD75, Mini-tower, GPDX, ASGT, LXD650, GM-8, GM-100,GM-150EX, G11, GM-200, Gemini G40
4" portable AP convertable 44" or 70" pier
MidnighTelescope 12.5" F/5 Dob
Bogart GA
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hfjacinto
I think he's got it!
Reged: 01/12/09
Posts: 9847
Loc: Land of clouds and LP
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Has anyone compared the Petzval version of the astro zap refractors? Or they worth going to the Petzval version or stick with the F9 scope?
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Scopes: Celestron 9.25, Orion 80MM and 120MM EON Apo
Solar: Lunt LS60THa/PT/B1200/50DS
Binos: Canon 15X50 IS
Mounts: CGEM and LXD75
Eyepieces: Explore Scientific,Meade, Axiom and TeleVue
Camera: Orion Deep Sky StarShoot V2, DMK 41
Messier Certificate # 2508
My Images: http://www.astrophotogallery.org/u342-hfjacinto.html
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Mike Holland
Pooh-Bah
Reged: 12/22/06
Posts: 1264
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Quote:
Drawbacks are this: Heavy for aperture. Not MUCH shorter than an f/8 system. Don't cool down fast, and you will see the quality of the image improve as the scope cools. At least that was the case with my Vixen 140. It might be happening with my TV 101, but it is a much smaller telescope, so harder to see I suppose.
Regards.
That has been my experience with my Petzval scope. If I go out on a winter morning with my 4" ED doublet and 4" NP-101, they both improve as they cool. The doublet is sharper than the NP-101 for a little while (depending on the temperature differential between the garage and outside). After they are both fully cooled, the tables are turned. It's not a long wait.
Mike
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SV80ED Raptor/NP-101/SV 110ED/Gibraltar/Vixen GP Mount/Losmandy GM-8/Astro-Physics Tripod/Naglers, Panoptics, and Radians
_______________________________________________
Optiphile [OP-teh-FILE] -noun, one who appreciates or obsesses over fine optical equipment, generally telescopes, binoculars, binoviewers, or photographic lenses.
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la200o
Pooh-Bah
Reged: 09/09/08
Posts: 1332
Loc: SE Michigan, USA
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Quote:
Quote:
Drawbacks are this: Heavy for aperture. Not MUCH shorter than an f/8 system. Don't cool down fast, and you will see the quality of the image improve as the scope cools. At least that was the case with my Vixen 140. It might be happening with my TV 101, but it is a much smaller telescope, so harder to see I suppose.
Regards.
That has been my experience with my Petzval scope. If I go out on a winter morning with my 4" ED doublet and 4" NP-101, they both improve as they cool. The doublet is sharper than the NP-101 for a little while (depending on the temperature differential between the garage and outside). After they are both fully cooled, the tables are turned. It's not a long wait.
Mike
Mike, where do you live? How much cool-down time we talkin' about? I live in Michigan and observe in some purty cold temps. Now and then I think about upgrading my TV 102 doublet to an NP 101, but then I start to worry about the cooling time.
Bill
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CPC 9.25
TV 76, 102, NP 101
Unitron 114
Gibraltar mount
Half Hitch Mk III
SolarMax 90 .7A/B15
Coronado PST
Eyepieces from the sublime to the ridiculous
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KerryR
Carpal Tunnel
Reged: 12/05/07
Posts: 2642
Loc: SW Michigan
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I live in SW Michigan, and have a Genesis (TV Petzval predecessor to the NP line). I observe with it year round.
I don't think you'll find cool down time to be prohibitive. The lack of tube baffles actually helps with this-- thermal currents are not repeatedly 'forced' into the optical path, making them less visible the instant they're out of the light cone (I hypothesize). I find my Orion ED100 cools a little faster, but not THAT much faster, mostly, I think, because the ED 100's baffles force thermals into the light path all along the 'cone'.
If you alread have a TV 102, and don't image, I don't think you really NEED to worry about getting the Petzval. I obverve with botht the Genesis and the ED100, and rarely find that I absolutely 'need' the 500mm focal length. In fact, for most targets, I prefer the ED100's longer fl-- I can use longer fl ep's to get decent mags.
I really only 'miss' the Genesis when observing the Veil, N.A. Nebula, and M31, which do indeed fit in the FOV of the Genesis, while not the ED100. Everything else comes out in the wash.
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Kerry
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Eddgie
Postmaster
Reged: 02/01/06
Posts: 7951
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Well, in support of the bigger scope, I have a Televue 101, and frankly, I do miss the extra aperture that the Vixen 140 provided.
I have thought many times about trading the Televue 101 for another Vixen 140.
The 140 though was only a couple of inches longer than a Vixen 102 Achromat. Will still work well on a CG5.
At the end of the day though, I keep the TV 101 becuase while I don't use it very much, I would probably not use the 140 any more, and when I get to dark skies, the HUGE freaking field of view of the TV really justifies keeping it. If I take my C14 to dark skies, the TV 101 provides the perfect counterpoint. The C14 shows thing IN space, while the TV 101 show SPACE! LOL.
But I get the appeal of a bigger achromat with less than horrible color as compared to a smaller APO. I really get it. Difficult decision.
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Celestron CGE 1400
Astro-Physics 6" f/8
Celestron EdgeHD C8
Antik AR1/Revenge Plates/Heartless Voodoos
The night sky is my mistress. She seduces me away from all other lovers.
Edited by Eddgie (09/03/09 01:56 PM)
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Mike Holland
Pooh-Bah
Reged: 12/22/06
Posts: 1264
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I live in Jacksonville, FL. It gets colder here than people realize, sometimes as low as the 40s, and on a few occasions, the 30s. My garage is always much warmer, particularly since there is a room over it trapping heat. In the summer it gets REALLY hot in there! I don't have a thermometer in the garage, so I can't give you numbers.
In the first 15-20 minutes is when you see most of the scopes adjustment to the cold, but I really do see some improvement with both scopes more than 30 minutes later. This is a really small sharpening, and only noticeable at high power with an object like Saturn where I can pick out a feature (say, the shadow of the planet on the rings) and see it better as time goes on.
At low to medium powers it's not really an issue. I might not notice it at all if not for the fact that I like to view planets mainly in the morning. If you're looking at an open cluster such as M41 at 60x you won't see these kinds of things very well (if at all).
Mike
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SV80ED Raptor/NP-101/SV 110ED/Gibraltar/Vixen GP Mount/Losmandy GM-8/Astro-Physics Tripod/Naglers, Panoptics, and Radians
_______________________________________________
Optiphile [OP-teh-FILE] -noun, one who appreciates or obsesses over fine optical equipment, generally telescopes, binoculars, binoviewers, or photographic lenses.
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Jim Curry
Pooh-Bah
Reged: 10/29/07
Posts: 1116
Loc: STL
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I too waited a half hour or so for my Vixen to cool when bringing from a warm house, especially in subfreezing temps. Now I just keep the scope stored in my unheated garage or shop and it's ready to go.
Jim
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Refractors to 6".
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MacRoberts
sage
Reged: 08/25/05
Posts: 443
Loc: Redlands, CA
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The general rule of thumb I've found with my NP-127 is about a minute per degree (F) for 20°? delta ? 50°. Very general but seems to work well enough.
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Jim
"When I consider thy heavens, the work of thy fingers, the moon and the stars, which thou hast ordained; what is man, that thou art mindful of him?" Psalms 8:3-4
TV Refractors
Fuji Binoculars
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Mike Holland
Pooh-Bah
Reged: 12/22/06
Posts: 1264
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I like that. It's simple, and though I would really have to test it to say I know it's correct, it does seem in line with what I recall. Hmm ... it might be time to invest in some thermometers!
Mike
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SV80ED Raptor/NP-101/SV 110ED/Gibraltar/Vixen GP Mount/Losmandy GM-8/Astro-Physics Tripod/Naglers, Panoptics, and Radians
_______________________________________________
Optiphile [OP-teh-FILE] -noun, one who appreciates or obsesses over fine optical equipment, generally telescopes, binoculars, binoviewers, or photographic lenses.
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stevew
Now I've done it
Reged: 03/03/06
Posts: 3487
Loc: British Columbia Canada
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Please note that the original post of this thread was posted in 2005.
The Antares Petzval is not currently available.
In fact [I am told by a friend that works at the plant that produces the Antares products] the Antares petzval designs were problematic, and were never made for mass production, although there may be a few prototype samples out there.
Steve
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Starlighter
Post Laureate
Reged: 08/03/07
Posts: 4820
Loc: Sunny California
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Also, WO made a Petzval available in 66mm, but dropped it. I wonder if it was for the same reason.
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Celestron C4-R 102mm achromat
Celeston Nexstar 6SE SCT
Meade 80mm APO Triplet
Televue NP-101
Televue TV-85
Vixen A70Lf
Vixen A80Mf
William Optics 66mm Zenithstar Patriot
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