Joe Lalumia
Post Laureate
Reged: 01/24/07
Posts: 3615
Loc: Rockwall, Texas, USA
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This link may also help you:
http://home.comcast.net/~astrophoto/Articles/Collimation.htm
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LX90 8" LNT, SV Nighthawk & TelePOD, SV 80/9D & M4 mount, ETX 90, Orion XT10i, 20x80 binoculars, SV-BV3s-- www.texasastro.org
"Great minds discuss ideas;Average minds discuss events;Small minds discuss people." Unknown
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raf1
super member
Reged: 11/18/05
Posts: 146
Loc: Texas
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Quote:
Replacement for above link: http://www.astrosurf.com/legault/collim.html
This technique appears to be appropriate for collimating other optical configurations as well, such as an RC - correct?
Thanks
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-Ron
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Too much "stuff" and too little time to use it .....
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beachchairbill
professor emeritus
Reged: 11/06/08
Posts: 508
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Last night I decided to take another look at Sirius and double check my first collimation adjustments. I found them to be right on the money and in need of a finer tune up because Sirius was not sharp and with out twinkel. Just for the heck of it, I removed the 90 degree diagonal and replaced it with a 45 degree diganonal and found the view much improved and Sirius was sharper and with twinkle. Now I'm more confused then ever.
BB
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Eddgie
Carpal Tunnel
Reged: 02/01/06
Posts: 2703
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It will work when the image is reversed laft/right at the eyepiece but not inverted.
This is why the some screw have to be turned CCW, and others have to be turned CW. In an SCT with mirror diagonal, what I call the "Left and Right" stars pull the shadow closer when the screws are turned CW, but the screw that I call the 12:00 O clock screw push the shadow away. The left and right screws behave differently because the image is reversed left to right.
I think that in the RC with a diagonal, it is the same. Image is reversed but not inverted.
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Celestron C14, CGE (Big Al)
Astro-Physics 6" f/8 (Buffy)
Televue 101 (No name, but I call it my Widescreen HD Space TV)
The night sky is my mistress. She seduces me away from all other lovers.
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Eddgie
Carpal Tunnel
Reged: 02/01/06
Posts: 2703
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The defocused pattern is commonly referred to as a "Fresnel Diffraction Pattern," or Fresnel Pattern. Wheter this is an exact name, I know not. There are several differ kinds of diffraction patterns, and the pattern we see visually may actually not be a true Fresnel Diffraction Pattern, but that is what I call it.
In an unobstructed telesecop, or in an obstrcuted telescope with a lot of defocus, the pattern looks like that found on a Fresnel lens. Hence the name.
Regards.
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Celestron C14, CGE (Big Al)
Astro-Physics 6" f/8 (Buffy)
Televue 101 (No name, but I call it my Widescreen HD Space TV)
The night sky is my mistress. She seduces me away from all other lovers.
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beachchairbill
professor emeritus
Reged: 11/06/08
Posts: 508
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Hi everyone,
Using Sirius at 300mm I tried to preform a better collimation than my my first attempt and found no difference with the donut on intra focal or extra focal. I did note however that their were no circles around the donut but streight lines from top to bottom.
Any one have a clue as to what this means?
Beachchairbill
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Eddgie
Carpal Tunnel
Reged: 02/01/06
Posts: 2703
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Are you using a standard prism diagonal? If you are using a 45 degree diagonal, bright stars will show a spike in one direction and a dimmer spike in the opposite direction.
Otherwise, would need a better explination of what you are seeing.
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Celestron C14, CGE (Big Al)
Astro-Physics 6" f/8 (Buffy)
Televue 101 (No name, but I call it my Widescreen HD Space TV)
The night sky is my mistress. She seduces me away from all other lovers.
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beachchairbill
professor emeritus
Reged: 11/06/08
Posts: 508
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When I did my first collimation last week, I used the Tele Vue Everybright Dielectric with a 32mm ep. These streight lines were present during this collimation process. When I referred to several articles on the next step for additional refinement, they all showed that I should be seeing circles instead streight lines up and down. Therefore, I change the 90 degree dielectric to a 45 degree diagonal to see if their would be any change in the streight lines. Their were no changes. I will say this, I'm performing this collimation process through a glass window and wonder if this is the problem?
Beachchairbill
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Eddgie
Carpal Tunnel
Reged: 02/01/06
Posts: 2703
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Yes, I would think it is possible for the window to put these spikes in, expecially if the angle of incidence is high and/or if the window is double pane with a plastic film barrier between. Who knows WHAT kind of refraction/reflection interfaces exist in that configuration.
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Celestron C14, CGE (Big Al)
Astro-Physics 6" f/8 (Buffy)
Televue 101 (No name, but I call it my Widescreen HD Space TV)
The night sky is my mistress. She seduces me away from all other lovers.
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beachchairbill
professor emeritus
Reged: 11/06/08
Posts: 508
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Yes, they are double pane, however no plastic film barrier.
When the weather clears, I will try an outdoor check and report back.
Beachchairbill
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Wes James
Post Laureate
Reged: 04/12/06
Posts: 3459
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BB-
I don't have too much doubt the lines you're seeing are due to looking out the window... almost like interference testing!
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Wes
Atlantic Beach, FL
Some bino’s from Miyauchi 5x32 Binon's up through Garrett 20x110 Signature's,
Some telescopes from a Stellarvue 80mm NHNG up through a couple of 8” reflectors…
And a wonderful 4.25" Delmarva Shiefspiegler!
Some good friends, made here on C/N.
Oh- several cats and a wonderful wife!
Anyone want a cat???? :-O
"When your work speaks for itself- Don't Interrupt" -Gamble Rogers
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dave brock
super member
Reged: 06/06/08
Posts: 165
Loc: Hamilton, New Zealand
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Just a general thought.
When collimating, I find it easier to 1st move the star to a position in the field that improves the image, then use the collimating adjustments to bring the star back to the centre.
Dave
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beachchairbill
professor emeritus
Reged: 11/06/08
Posts: 508
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DB,
In or out of focus?
Thanks
BB
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dave brock
super member
Reged: 06/06/08
Posts: 165
Loc: Hamilton, New Zealand
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Quote:
DB,
In or out of focus?
Thanks
BB
Either. If the seeing isn't good enough to collimate in (at) focus then rack out of focus until the disc is stable enough to be useful. Not as accurate but better than nothing.
Dave
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20" homebuilt truss dob
6" watson refractor
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