11 votes

I'm having trouble achieving sharp telescope focus

Your telescope has a 2000 mm focal length, and 200 mm aperture. With the 20 mm eyepiece, you get 100x magnification. With the 10 mm lens, you get 200x. Several things could cause what you describe: ...
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8 votes
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How can I accurately find & apply the white donut to the center of my mirror?

I make my own mirrors and telescopes. The method recommended by Gary Seronik, that you linked above, is very good, and it's widely used. A few comments: Don't be afraid to touch the mirror with ...
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6 votes
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Can a Ritchey–Chrétien telescope be collimated using a standard Newtonian laser collimator?

No, the fundamental designs of the two types of telescope are in this respect quite different. The Newtonian laser collimator works by shining a laser through the eyepiece holder to the secondary ...
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  • 1,335
3 votes
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Laser Colimator vs Cheshire eyepiece

Why not both? (if you can afford them) Both will do the job, but each has its strengths. Cheshire eyepiece (or, more properly, Cheshire/sight tube combo, which is the popular combination nowadays): ...
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3 votes
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Newtonian reflector collimation question

Your scope is f/5. There will always be some coma aberration. Always, the image quality is worse as you get closer to the edge of the field of view (FOV). Personally, given that the fact that you will ...
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  • 316
3 votes
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Collimating with a home-made collimation cap

The Gary Seronik website that you cite is a good one - it's not leading you astray! There are a couple of important things to look at: Look straight down the main tube of your telescope at the ...
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  • 634
2 votes
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Laser Collimator producing oval not circle on the Primary

This is a slightly tricky one. For a conventional Newtonian reflector, shining a laser collimator back over the secondary to the primary should present a small dot on the primary - the task then is to ...
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  • 634
2 votes

Laser Collimator producing oval not circle on the Primary

First of all, what do stars look like through the scope, particular just inside and outside focus? If they are oval, then read on. I'm not familiar with this telescope, but I suspect the most likely ...
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  • 4,065
2 votes

Collimator for Dobsonian, same as Newtonian?

Yes, of course it will work. A Dobsonian is merely a Newtonian telescope on a special mount.
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  • 2,303
2 votes
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Telescope collimation issue

First off - good job for paying attention to collimation. For a newtonian telescope, it is as important as changing the oil on your car. It would help to know a little bit more about the telescope. ...
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2 votes

What are the aberrations of an SCT? And how can they be eliminated?

The primary aberration present in a Schmidt–Cassegrain telescope is spherical, due to the primary mirror being spherical in shape; that causes light at the edges to have a different path length than ...
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  • 2,527
1 vote

Is a mirror cell only necessary for collimation?

The primary mirror needs to be on a support (a mirror cell) that lets you adjust the tilt of the primary mirror. The turnbuckles you are describing change the tilt of the secondary mirror. It does not ...
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  • 7,160
1 vote
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Celestron C14 collimation and cleaning

Will this affect image quality? It depends on "where" the dust is located. If on the telescope, then not very much. If on the sensor, you'll get the shadows of the dust on your images (...
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  • 1,501
1 vote
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What are the aberrations of an SCT? And how can they be eliminated?

Astigmatism. No way to eliminate in SCT. Reduce it with proper fixing of every optical element. Astigmatism is only eliminated with 3-mirror scheme. Curvature of field. No way to eliminate in SCT. ...
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  • 341
1 vote

collimating AstroMaster 114

With a tube length of 46 cm and a focal length of 100 cm, probably the AstroMaster 114EQ is not a classical Newtonian but uses a fast (e.g. f/4) spherical primary mirror and a corrector lens built ...
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1 vote
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Laser Collimator For Dobsonian vs Newtonian

A Dob is a Newtonian, so yes it will work. Strictly speaking the Dob bit is the mount, but it's nearly always a newtonian that's mounted.
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  • 4,065
1 vote

I'm having trouble achieving sharp telescope focus

Did you try to slowly "fine tune" your focus when using the 10/6 mm eyepieces? The higher the magnification, the more sensitive focus is to adjustment.
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