Review of the Airy Disk 85/510 triplet ED FCD-100 APO Refractor

I’ve been in the hobby of amateur astronomy since the early 80’s when I got my first telescope. Buying a telescope back then was a straightforward process as there weren’t nearly the number of options that are available today and while recently the community witnessed the downfall of Orion/Meade, overall, it feels like the hobby in general has never been stronger. One of the “downsides” of this is the amount of choice we now have… it can sometimes feel overwhelming. Which scopes are a great value? Which are not?

One of the newer names on the block is Airy Disk, and while they’ve been an OEM manufacturer for other companies since 2007, they only recently decided to make their own scopes. They specialize in refractors, and nearly everything is made in-house… from blank preparation to the final step of lens mounting and everything in-between, even designing their own focusers. This gives them the luxury of full control over the quality of the telescope, and from the scope that I tested it shows.

Airy Disk has several refactors available, from a giant 204mm down a much more manageable 60mm, with a couple of bino scopes thrown into the mix, but it’s the 85mm F/6 triplet that I had the pleasure of reviewing.

Upon opening the box there’s a printout of the tests that were run on the scope: 

With the scope out of the box I could see and feel it had a very good build quality. Though I did notice that there was no way to rotate the focuser. Visually, this isn’t a big deal but moving to astrophotography using the .92x reducer/flattener everything is threaded together and the only way to rotate the camera is to rotate the entire scope.

**Note: Airy Disk now has a CAA that you can thread into the imaging train. You can find the CAA HERE.

The focuser, rack and pinion with an additional guide rail on the top, feels very robust with no backlash or tilt. Overall it was smooth, though the one I had was a little rough in a couple of spots. You can also attach an auto-focuser quite easily.

The rings include two vixen style dovetails, with the top being raised up and can act as a handle. I did run into the case with the bottom dovetail being too close to the OTA when it came to adding my camera so I needed to raise it, either with a set of risers or by flipping the rings upside down.

Visually the scope performed fantastic, both widefield and high-power views gave pinpoint stars with nice color and contrast. There was very little to no chromatic aberration even on bright stars or objects such as the moon or daytime/terrestrial viewing. One of my favorite visual tests for a telescope is the Perseus double cluster, and the Airy Disk did not disappoint… with a 15mm eyepiece it was spectacular! As a visual instrument I highly recommend this scope.

*If visual is your goal for this telescope keep in mind that while a synta bracket is included, a finder scope and diagonal are not.

While it was a pleasure using the telescope visually, I really wanted to see how it performed photographically. The telescope comes with an adjustable (5mm) .92x flattener/reducer. After attaching my asi294mm camera and getting the correct back focus, which worked out to an almost perfect 55mm, I started taking some images.

The first test image was of a brighter star out of focus about 4mm from center of the sensor (the asi294mm sensor is 13mm wide). I was very impressed with the airy disk that was produced.

The next step was to test field flatness with the reducer/flattener. From the images I took I ran a star aberration test to determine if there was any field curvature… this is done by comparing the corners, middle and edges of the image as the camera sensor falls into the field of view of the scope. While at the time I didn’t have a larger sensor than my ASI294MM, I was very pleased with what I was getting. If the stars weren’t perfect, they were very close and the field of view was nice and flat with the stars well corrected. 

Finally color and contrast… this can be a little harder to test photographically as there are many other factors that come into play such as filters, camera, atmospheric conditions, etc. I found that, following in the steps of my visual tests, the color seemed vibrant and didn’t require much finessing in post processing to really bring it out.

Overall, I was very pleased with the Airy Disk 85/510 APO triplet and highly recommend it for both visual and astrophotography (with the included reducer/flattener). While you can find similar sized APO’s for less than the Airy Disk, it’d be hard to find similar optical quality for the same price.