Orion XT12 Intelliscope
Submitted: Thursday, 4th May 2006 Rick Nelson
Unpacking and Assembly
Orion obviously made a mistake in shipment. I thought I had ordered a Dob... instead they sent me a water heater with some optics!
The scope and everything else arrived unscathed in four boxes - the mirror, the tube, the base, and the everything else. Very well designed die-cut packing; no plastic peanuts; double heavy-duty cardboard boxes - a box inside a box.
Assembly was reasonably simple and straightforward. Sorting out the "Bag O' Washers" was the only challenge. Since I ordered the Computerized Object Locator, extra care was taken with the encoders -especially the AZ encoder which is sandwiched between the Dob base and the mount platform - adjusting the tightness the center bolt is a tricky step and I had to do it a couple of times before I got it just right. Even with nylon-coated locking nuts it needs to be adjusted periodically so the encoder reads correctly.
The mirror, packed separately, is enclosed in its aluminum cell but must be mounted in the tube - the instructions make it appear more intimidating than it is - actually no big deal. But man... this guy is huge. Weight of the assembled tube is 50lbs. but surprisingly easy to handle... just a bit bulky. I can easily grab the primacy mirror end with one hand (since it's very rigid) and cradle the opposite end with my other arm and place it gently in the mount.
The Correct Tension adjustment bolts consist of a "retaining knob" and a "tensioning knob" that fit into the altitude bearings on each side of the optical tube. The "retaining knob" is on the same side of the base as the altitude encoder and is screwed in finger-tight. The "tensioning knob" threads against nylon pads on the mount base - the tighter the tension, the less movement. This system works well and, unlike some spring-tensioning systems, the scope stays put without counterweights or drifting problems.
Adventures in Collimation
Yeah, yeah... I read everything I could get my hands on... but I'd never done it myself. The bad news is that it took me longer than it should have. But the good news is that I finally figured out what the heck I was looking at through both the collimating cap and the Cheshire eyepiece and presto... collimation suddenly was simple! I'm sure that over time, I'll get a truer feel for it and know just what adjusting bolt to tweak and exactly how much to tweak it.
Actually, the process is not unlike aligning a finderscope.
Reasonably cloud free, average transparency, sub-par seeing - that's what the Clear Sky Clock said. Oh, what the heck... I couldn't wait anymore. So I took the Water Heater out to the backyard.
No polar alignment (hey, it's a Dob) just set down the base, load the tube (sort of like placing a torpedo in the launch cradle) put on the finderscope, put in a 25mm eyepiece and point at something (in this instance, Sirius). Aligned the 8X50 finderscope, racked out, racked in, and focused. 3 minutes!
Holy Cow! Where did all those stars come from? Needless to say, I was a bit overwhelmed with the view - never before had I seen such a bright starfield from my suburban location, even on the best of nights. I had to try it... just to see... I slewed west and north to M42. I'm used to the view of the Orion Nebula though my Mak 127mm and I wasn't sure what to expect from the Water Heater - but I never expected it to be so huge and bright! I saw details from my own backyard that I had only seen in photo and CCD images. Simply amazing!
I am absolutely thrilled with this scope. On the next night out, I setup and tested the Computerized Object Locator - it works surprisingly well. Everything that I entered on the keypad was within the field of my finderscope. I'm sure with more practice; I'll get better at using this tool. With it, I viewed several objects that I had previously struggled to locate by star hopping alone. Now that I had some better visual reference points set in my mind, getting there again (without using the object locator) was a piece of cake.
The specs: 1500mm at f4.9. With a 25mm EP that's about 60X magnification; 150X with a 10mm EP; I put a 2X Barlow on the 10mm (just to see) and the Water Heater handled 300X easily - even on a lousy night. Now I'm no optics physicist, and I'm not experienced enough to debate the ins-and-outs of this-or-that brand of mirror. But I can tell you that the images appeared crisp and tight (after I field-tweaked the collimation a bit). Saturn was reasonably detailed even with such mediocre transparency and contrast was pretty darn fair - but the DSOs were simply breathtaking!
Alt/Az motion is fairly tight but not jerky at all. The scope sits high enough off the ground that an additional platform is not necessary for comfortable viewing (although I must admit that I like to sit while observing and I may need to see about either making or purchasing a real observing chair now).
Although the rack-and-pinion focuser is smooth enough, it can hang a bit when you pump up the magnification; the addition of a helical focuser solves that issue. I wish the machining tolerances on the 1.25" eyepiece insert were a little tighter - and a compression ring type retainer would have been a major plus.
Extra care must be taken when setting the scope in the Dob base: the altitude encoder must have a bit of travel to function properly and you don't want to set the bearings down on top of the encoder - this can be a little tricky in the dark with a heavier tube like this.
I also thing the platform base should have heavier duty rubber feet - I know these can be replaced, but it's a minor gripe, nonetheless.
But would I buy it again?
.. in a heartbeat!