Let us know how the 100 mm performs. With that aperture you should get some good views of the planets. This may be one of the best deals around for refractor buffs. The larger the aperture the larger the focal ratio required for good color correction. It would be interesting to compare the color correction to the 80 mm. It may or may not be better than the 80 mm since the smaller diameter will perform better at a shorter focal ratio assuming the same number of elements and similar ED glass. -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Wednesday, December 10, 2008 9:07 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Dear Santa: Here is the newly-arrived Orion 100mm f/9.0 ED refractor (Santa looks just like a FedEx guy!) stock #9975 $697, next to the 80mm f/7.5 ED stock #9895 $489, and below them all, an ancient Orion 80mm f/5 achromatic refractor with 2" focuser (Japanese manufacture, circa 1990-92) and I can't remember what I paid for that one, seems like somewhere around a hundred bucks at the time. I've used that little one for hand-guiding astrophotos with my old Pentax SLR camera and collection of antique lenses, lol. http://s260.photobucket.com/albums/ii24/JethroTull1958/?action=view¤t= Refractors002b.jpg The 100mm uses the exact same tube rings as the 80mm, though I bought 2 extra pairs because I mount reflex sights and other accessories on them, as well as attaching the scope to the mount. How many of you remember when Jim Gibson and I bought our 80mm ED refractors? I and others commented on the thick walls of the objective cell, and main tube OD, speculating that it was so a 100mm unit could use the same tubing stock and cell castings. That appears to be spot-on. I am able to use same 50mm right-angle, correct-image finder that I had for the 80mm, as well as any of my stable of reflex sights. I still like the Mars-eye best (thanks to Dave Bennett for calling my attention to that one). It looks like these particular models are being phased-out in favor of newer, pricier model ED APO's by Orion. The 127mm model is no longer listed in their on-line catalog. I lusted after that one for a long time, but 2 grand was too pricey for me to consider for a 5-inch tube assembly. Even the one-thousand-dollar price on the 100mm was too steep, but at $680, it's a good deal. I've tested the 80mm against similar-sized Tele Vue APOs and was delighted with what I found. The color correction in both scopes was identical, up to the diffraction limit. At and past the diffraction limit, the Orion scope did display the slightest hint of an unfocused haze, barely detectable, the sign of a smidgen of undercorrection. If the 100mm scope performs similarly, and it should be better due to the longer f/ratio, I'll be very happy. I wanted this scope for several purposes: Backyard observing, multiple-star observing, and planetary observing. I hope to image with it in the future. While it will fit on my "Weightless" mount, it is so heavy that the motions will probably not be as smooth as they are with smaller scopes. I will probably mount it temporarily on my old Jaegers driven GEM, on a 60" pier, for it's shakedown cruise. Besides the purchase price and shipping charges, this scope is going to cost me some jewelry and a few pair of shoes. Married buyers, beware! *;o) *
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com