Astro-Tech Newtonian reflector collimating tool


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The Astro-Tech ATCOLL 1.25" dual-purpose Newtonian reflector collimating tool combines a sight tube and a Cheshire eyepiece. Unlike more expensive competitive Cheshire eyepieces, it has a soft fold-down rubber eyecup to improve contrast during use and protect eyeglasses from getting scratched.

Our Product #: ATCOLL
Astro-Tech Product #: ATCOLL

Product Description

The Astro-Tech ATCOLL Newtonian reflector collimating tool is a combination 1.25" sight tube and Cheshire eyepiece. It is precisely machined of aluminum and black anodized. A soft fold-down rubber eyecup (rarely found in more expensive competitive Cheshires) shields your eye from ambient light for better contrast and protects eyeglasses from being scratched during use. It's 6" length provides higher collimating accuracy than shirter competitive Cheshires.

The Astro-Tech ATCOLL has the precisely centered sighting hole and crosshairs of a sight tube, plus the cutout in the side of the tube with the precise 45° angle matte silver reflecting surface of a Cheshire eyepiece. As it is a combination tool, it is less expensive than buying a separate sight tube and Cheshire.
For the sharpest images with a Newtonian reflector, the optics must be carefully collimated (aligned). First, the diagonal mirror must be properly centered under the focuser and aimed at the primary mirror. You cannot assume that the diagonal mirror has been properly set up at the factory, or that it did not accidentally get knocked out of alignment during transport. If the diagonal is indeed out of alignment, collimating the primary mirror becomes difficult. This is particularly true with fast focal ratio (f/4 to f/5) reflectors, as even slight collimation errors in these systems can significantly degrade the image.
Use the sight tube crosshairs of the Astro-Tech ATCOLL to confirm that your diagonal mirror is properly centered under the focuser and adjust it if needed. It then lets you adjust the tilt of the diagonal to aim it accurately at the center of the primary. Once you've set the position and orientation of the diagonal mirror with the sight tube function, use the Cheshire eyepiece function to properly align the primary mirror.
The sight tube/Cheshire tool combination generally provides accurate enough collimation for visual use and most photography. The Astro-Tech ATCOLL collimating tool is primarily designed to be used in daylight or early twilight, but the Cheshire function can also be used in complete darkness (for those times when you can't set up until late) by shining a red flashlight into the 45° reflecting cutout in the side of the tube. Instructions on how to use the Astro-Tech ATCOLL collimating tool are included.

Tech Details

Weight 6.4 oz.
Warranty 1 year


Review by:
Great for accurately collimating longer newts and makes all the adjustments unambiguous. Prefer old-school techniques like this to lasers because I've had really bad luck with misaligned laser collimators. Don't have those problems with this and it's far cheaper. Makes all the needed adjustments nice and unambiguous. Build quality also very good, and at the price any complaints would feel like nitpicking. (Posted on 7/24/2019)
Review by:
Recently purchased the collimator for use with my 6" Newtonian F/4 imaging scope. The collimator is well built. It would have been nice to receive instructions for using it but there is a lot on the internet so that was not too disappointing. Once a good set of instructions were found collimation went well although it is a time consuming process. One drawback with this kind of collimator is that for trifocal eyeglass users the crosshairs are out of focus when the rest of the reflections are in focus. In reverse when the crosshairs are in focus (glasses off) the rest is out of focus. The downside of getting old. Hopefully will be able to try the collimation soon. (Posted on 1/2/2019)
Review by:
I use this to collimate a 10" f/4.7 Newtonian. While it has the potential to get very accurate collimation, I found the combined sight tube / Cheshire design to be frustrating to use. The crosshairs are thick, and make it difficult to accurately see the Cheshire shadow on the primary mirror.

Frankly I would recommend sticking to a standalone sight tube and a standalone Cheshire in two separate devices, or investigating Barlowed laser collimation for primary collimation and getting a standalone sight tube for secondary collimation.

Three stars since it *can* still get accurate collimation, I just think there are much easier ways to go about it even if you want to avoid lasers and all their headaches and inaccuracies. (Posted on 12/28/2018)
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