Brooklyn
scholastic sledgehammer
Reged: 07/24/08
Posts: 870
Loc: Central New Jersey
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So there are many SCT collimation guides out there, some are very general some are more specific. I searched this entire forum for all of the collimation sites and have used them well.
However i have stumbled upon another page that i thought would be particularly useful to people here.
There are so many good websites to use for collimation of SCTs...
i just recently found:
http://www.asterism.org/tutorials/tut14-1.htm
Notice the printable guide at the top, this little picture guide is exactly what ALL collimation guides were missing. Who could have thought it was so simple in picture form.
Also this guide here...
http://sweiller.free.fr/collimation.html
Actually has pictures!!! the first collimation SCT guide i have ever SEEN with real pictures!
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Meade 8.25"(209.55mm) LX-90 EMC (SCT)
Albert Einstein =>
“Intellectual growth should commence at birth and cease only at death.”
“If you can't explain it simply, you don't understand it well enough.”
Edited by Brooklyn (08/12/08 11:25 PM)
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HendyPhoto
Sith Lord
Reged: 08/09/06
Posts: 1485
Loc: Bountiful, Utah
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Excellent find! This will make a very nice, new addition to my collimation page collection!  I already printed out the guide!
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~jon
SparkCast Ustream
CGE1400XLT w/HyperStar
90FD 66SD C6-R SN-8
CPC1100XLT Hutech 20D
Manny-Mod Vixen Porta
Mallincam MCHP
SPC900NC
CG-5 GT
"Two things are infinite: the universe and human stupidity;
and I'm not sure about the universe." --Albert Einstein
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chboss
member
Reged: 03/24/08
Posts: 35
Loc: Switzerland
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Excellent information, thank you for posting!
CS Chris
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David Knisely
Postmaster
Reged: 04/19/04
Posts: 6760
Loc: Beatrice, Nebraska
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Here is something I put up a while back right here on Cloudynights:
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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info
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Luigi
Carpal Tunnel
Reged: 07/03/07
Posts: 1960
Loc: Massachusetts
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David's illustrations get it right, you need to be at high power. Lots of times you may not see the Airy pattern but a wiggly blob due to seeing. It works the same with the wiggly blob.
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17.5" f/5 Discovery Truss
IM715 7" f/15 MCT, Eon-120ED
Lunt 60mm single etalon HA
CG5A coffee grinder, Orion Skyview Alt-AZ
35,19,15 Pans.9 Nag. Meade 24.5 4kSWA, 4.7 5kUWA.
BO-TMB 7mm planetary.
Zeiss Diascope 85
Zeiss, Leica, Canon IS, Fujinon, Nikon binos
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rmollise
Carpal Tunnel
Reged: 07/06/07
Posts: 1564
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Quote:
David's illustrations get it right, you need to be at high power. Lots of times you may not see the Airy pattern but a wiggly blob due to seeing. It works the same with the wiggly blob.
I don't think he's trying to portray the Airy disk and diffraction rings. What I think this is meant to be is the diffraction disk and rings of a slightly out of focus star, which is what you will normally use for collimation, and which should be visible under all but the worst conditions.
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Uncle Rod
Watch for Rod's New Book:
Choosing and Using the New CATs--coming soon!
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coutleef
scholastic sledgehammer
Reged: 02/21/08
Posts: 806
Loc: Montreal and St-Donat, Québec,...
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Great drawings that are very useful combined with the drawings provided in the first internet link above.
Very useful thanks
Francois
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François
Nexstar 8 SE
50mm StellarVue finderscope, Astronomik UHC-E and Orion OIII filters
WO Swan 40mm; TV Pan 22mm; TV Nagler 9T6, 12T4, 17T4; TV Plossl 11mm and 15mm.
WO 2" dielectric diagonal retrofitted with Denk Power Switch (and now reach the zenith with the shorty adapter).
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hudson_yak
sage
Reged: 11/15/07
Posts: 446
Loc: Hyde Park, NY, USA
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One thing that isn't always emphasized is to pick a star overhead, or close to overhead. If I adjust for one of those it'll look slightly off on a star lower down, even Polaris, for example. For awhile I was wondering why my collimation seemed to be getting out of whack frequently and it turned out it really wasn't, it instead had to do with the altitude of the star I was looking at.
Several weeks ago there was a report posted in the sct-user group talking about this.
I suppose it does bring up the question, since, for example, Jupiter is quite low in the sky for many northern hemisphere viewers now would it be better to collimate on a star at a similar altitude to get the best detail of the planet. No idea.
Mike
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Meade 8" LX10
Orion ED100 + SVP
Meade 12" LightBridge
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coutleef
scholastic sledgehammer
Reged: 02/21/08
Posts: 806
Loc: Montreal and St-Donat, Québec,...
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In several of the guides on collimation they do mention that collimation should be done on a star near your target. At some point, we cannot be collimating each time we change target!
I suppose it depends on your level of desire of perfection
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François
Nexstar 8 SE
50mm StellarVue finderscope, Astronomik UHC-E and Orion OIII filters
WO Swan 40mm; TV Pan 22mm; TV Nagler 9T6, 12T4, 17T4; TV Plossl 11mm and 15mm.
WO 2" dielectric diagonal retrofitted with Denk Power Switch (and now reach the zenith with the shorty adapter).
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hudson_yak
sage
Reged: 11/15/07
Posts: 446
Loc: Hyde Park, NY, USA
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Here is the report I mentioned:
http://www.paquettefamily.ca/astro/star_study
The punchline about collimation as at the bottom.
I suppose with an alt/az SCT it could make some sense to split the difference and pick a star somewhere midway up or a bit more to have sort of an average setting, on the assumption the affects are altitude-related only and would be the same for any azimuth. For polar mounts this wouldn't make as much sense to do.
Mike
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Meade 8" LX10
Orion ED100 + SVP
Meade 12" LightBridge
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Brooklyn
scholastic sledgehammer
Reged: 07/24/08
Posts: 870
Loc: Central New Jersey
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you know...i always seem to use Altair as my collimation star. If thats not available, i use vega... but altair is definitely where i would call a "average" collimation.
In my situation i have trees all around my observing site, so i cant really see under 60 degrees to the north and east, and 30 degrees to the south and west. In my case, as im sure many suburban people have, i would collimate with a star somewhere even higher, like vega or even maybe deneb.
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Meade 8.25"(209.55mm) LX-90 EMC (SCT)
Albert Einstein =>
“Intellectual growth should commence at birth and cease only at death.”
“If you can't explain it simply, you don't understand it well enough.”
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David Knisely
Postmaster
Reged: 04/19/04
Posts: 6760
Loc: Beatrice, Nebraska
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Quote:
Quote:
David's illustrations get it right, you need to be at high power. Lots of times you may not see the Airy pattern but a wiggly blob due to seeing. It works the same with the wiggly blob.
I don't think he's trying to portray the Airy disk and diffraction rings. What I think this is meant to be is the diffraction disk and rings of a slightly out of focus star, which is what you will normally use for collimation, and which should be visible under all but the worst conditions.
Actually, the images are for a star that is in-focus or very nearly so, although actually, it can be a little easier to have it just a hair out of focus to help make the flaring a bit easier to see. Clear skies to yo.
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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info
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Stephen S
super member
Reged: 08/21/07
Posts: 132
Loc: San Diego, CA
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Thanks for the internet link. When I first got my C9.25, I had gotten it hopelessly out of whack and was frustrated beyond comprehension try to make adjustments. Somewhere along the way, I found a copy of the linked to guide. It was critical to helping me finally get things sorted out. It may not be a complete guide for collmination. However, it's great for knowing what knobs to turn when and in what direction. I think this is a great tool for those fairly new to SCTs (like me). I now keep a laminated copy of this guide in my accessory bag at all times. Sure wish I knew who the original author was so that I could thank her/him.
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C9 1/4-SGT (XLT)
AT80ED
Vixen Porta Mount
50mm Takahashi LE
24mm Meade UWA
13mm Televue Ethos
7mm Pentax XW
3mm Smart Astronomy
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Sid Gelpi
journeyman
Reged: 03/17/08
Posts: 5
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I did the attached Readers Digest procedure based on Ed Moreno's longer version that might be usefull.
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