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The Orion ST120 -A lot of 'scope, no mucho dinero

Posted by norman sullivan   03/25/2009 12:00AM

Starting a hobby later in life is sort of a mixed blessing.

You have a sense of realistic expectations that comes from maturity. You have more time available to devote to it, due to being retired, or only working part time.

Unfortunately, you also have less money to put into it - due to living on a retirement pension, or only working part time.

So it seemed to me that spending more than, say, $200 on one hobby item seemed somehow disloyal to my family and our budget. After all, one still needed to purchase a few good eyepieces, books, and perhaps a decent pair of binoculars as well as the usual food, clothing, and shelter. Thus it was that I purchased an 80mm long tube refractor OTA and, separately, a sturdy altazimuth mount for it. Plus a few good (used) Plossl eyepieces.

At first all was well in Astro land - the moon and planets were a grand sight, and double stars were a visual treat. I could even make out the famous Trapezium quartet in Orion, and the nebula around it. But after awhile, I found myself very limited for Deep-sky work due to the limited aperture. Something else was needed - but what?

Like countless legions of others, I acqired a 6" Dobsonian mounted reflector telescope. This gave me a window on the deep sky, to be sure, but the planets no longer looked as crisp, and, worse, I could no longer separate many double stars due to the inherent coma. So I resigned myself to lugging two telescopes around every time I wanted to observe. There had to be a better way. Orion to the rescue.

Orion had been sending me catalogues for years, even though my purchases had been minor ones. They made interesting reading. For instance, there was a large aperture (for a refractor) telescope of 120mm that was an f5 (600mm) focal length and available as an OTA for a very attractive price. This was tempting, but could an f5 achromat really deliver pinpoint, crisp, contrasty images for which refactors are prized? In a word - Yes.

The first night out - a partly cloudy, windy February night - I was amazed. The stars had their textbook Airy discs with diffraction rings, and the scope would take "high power" of 200X or more on double stars. Polaris was very cleanly separated, plus the more difficult Rigel.

Venus showed a clean crescent, and Saturn a very pronounced "spindle". There was some chromatic abberation, to be sure, but it was not a problem. Craters on the moon looked as sharp and contrasty as with my 80mm f11. Better yet, I could now see some structure in the brighter galaxies, especially M81 & 82, and the pairs of galaxies in Leo. The Orion nebula was now spectacular, and I could make out M1 as well, only slightly less well than with the 6" Dob. That's the weird thing; the 4.7" short-tube refractor is only slightly less of a light gatherer than the 6" Dob, but gives sharper views with more contrast.

I might add that some eyepieces work better than others; the Orion "Epic" ED-glass plossls work very well. I also added their "anti-fringing" filter. A good 3-element Barlow lens completed my optic package, and I now had something that more than compared with the various catadioptric models that are ubiquitous at star parties. And I had done so at a price that was below their most basic model. I only wish I had known all this when I had started out, but I guess there is no substitite for first hand experience.

Due to the plethora of pictures and specs available at the Orion website, I have not included any here, but if anyone wants to query me further in regard to this amazing little scope, I will be happy to reply.