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Old 19-07-2021, 04:13 PM
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toc (Tim)
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Can someone recommend a cheshire?

Looking for a cheshire - can someone recommend one? Is the Orion or Celestron ones good enough, or is it worth spending additional cash on something more? I already have a howie Glatter laser collimator, but I want something to double check that my focuser is correctly aligned with the secondary mirror of my MN190.
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Old 19-07-2021, 09:23 PM
croweater (Richard)
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Hi Tim, I have the orion collimating eyepiece (combination cheshire/sight tube) that Bintel sell. It's probably exactly the same as the Celestron one. I use it with my reflector and am happy with it. I don't see any need to spend more dollars than that.
Cheers, Richard
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Old 20-07-2021, 10:09 AM
Startrek (Martin)
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Tim,
I use an Orion Collimating eye piece ( Cheshire ) to align the secondary on my 6” , 8” and 12” newts
Does the job ok
A hint though , use it on your scope outdoors in good sunlight or if indoors point you’re scope to a bright light, you get a much clearer view and makes collimating easier
To fine tune Collimation I use an Orion LaserMate deluxe collimator
Cheers
Martin
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Old 21-07-2021, 11:07 PM
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toc (Tim)
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So I already have a Howie glatter laser collimator, but I need to double check that my focuser is properly aligned with the secondary.
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Old 29-07-2021, 08:41 AM
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The Orion one only inserts a short distance and is not a well-designed tool. It cannot get close enough to the secondary.
The Celestron is a far better tool.
And the Astrosystems Light Pipe is better still.
All of these tools are "Combination Tools", combining a Cheshire (pupil on one end, bright reflective ring with dark center on the other) and a Sight Tube (pupil on one end, crosshairs on the other).
A pure Cheshire has no crosshairs.

Lasers duplicate the function of a sight tube for secondary mirror alignment.
A Barlowed laser duplicates the functions of a Cheshire for primary mirror alignment.
A laser by itself should not be used for primary alignment because you won't put the primary alignment in tolerances.
Collimation tolerance for a primary mirror is 0.005 f/ratio³.
At f/5, that is 0.63mm, which is finer than the laser beam.
A Cheshire can align to a greater precision because the error is magnified 2X.
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