Megrez 90 apochromatic doublet refractor telescope from William Optics described with specifications for astro-imaging astrophotography use mounted on Paramount ME
William Optics is a supplier of refractor telescopes and accessories located in Taiwan, and distributing worldwide. It was founded in 1996 by William and David Yang to produce premium scopes, as well as subcontracting their designs to other manufacturers (such as APM). The WO products are very high quality, with a great "fit-and'finish", but are relatively affordable for the amateur market. The Megrez series of refractors consists of doublet apochromatic (APO) refractors utilizing FPL-53 fluorite glass elements to minimize chromatic abberations. While it is only a doublet - and therefore not capable (theoretically) of eliminating all chromatic abberation, it does a good job - especially for the price (the WO Megrez 90 sells used for around $800). The focuser is a 10:1 FeatherTouch which includes a camera rotator with lock (as well as focuser lock). |
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The Megrez 90 is a 90mm diameter, f/6.9 scope, yielding a focal length of about 620mm. I was going to use this scope both as a guide scope and as an imaging scope for widefield shots. However, I ended-up not really needing a guidescope, as I have a dual-chip SBIG camera (which can both image and guide with the internal guide chip). I did try imaging with the Megrez 90, but was disappointed in the amount of coma and other distortions, especially in the corners of my 15x15 mm CCD chip (KAI-4020). I bought the WO field flattener / reducer (v.III), but never got the spacing correct, so had terrible results with the reducer. I have since sold this scope and bought an FSQ-106EDX for imaging. |
The Megrez 90 in its fitted ScopeGuard case, and the case itself, are shown in the photos below: |
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Below, you can see some views of the Megrez 90 riding piggyback on the 12" LX200R, and also mounted on the Paramount ME: |
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Below, you can see the Megrez 90 on the LX200, with the ST-4000XCM one-shot color camera on the Megrez, and the SBIG Remote Guide Head on the LX200: |
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Below, you can see the Megrez 90 mounted on the Paramount ME - a bit overkill, using a 150-lb payload capacity mount for a 15-lb scope! |
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Overall, the Megrez 90 is a well-constructed medium-grade apochromatic refractor that does a fine job visually, and has potential for astro-imaging. If the field flattener were used properly (correctly spaced from the CCD chip), this scope could be used with at least APS-size (i.e., about 15x15mm) CCD chips. I was actually pretty happy with the images initially, and I didn't find a great deal of chromatic abberation ... but the coma in the corners of the field were too great to produce high-end astro-images. I sold the Megrez 90 shortly after taking delivery of the FSQ-106ED. |
Megrez 90 apochromatic doublet refractor telescope from William Optics described with specifications for astro-imaging astrophotography use mounted on Paramount ME |