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Orion XT12g GOTO Dobsonian

Posted by Keith Lawson   11/10/2011 08:00AM

Orion XT12g GOTO Dobsonian
After my first comments and initial excitement concerning the XT8g over a year ago I thought I would take some time before writing about the XT12g. My XT8g was a surprise. I expected average optical performance and the scope was initially purchased for the uniqueness of the mount. I had plans on replacing the existing telescope OTA with a longer focal length optical tube or refiguring the optics to turn the XT8g into a top notch visual telescope. The optics turned out to be excellent with no need for modification and gave me reason to step up to the XT12g. I purchased the XT12g scope with fingers crossed hoping that the optical quality would be equal to the XT8g.

This month is my one year anniversary of ownership of my XT12g. Optically, this is the finest large telescope (10 inch plus) I have ever owned and I have owned a few in my 30+ years of designing and building telescopes. The visual imaging is superb for both deep sky and lunar/planetary observing. The optics are so good that I can detect the companion of Eta Gemini at 114x on a night of good seeing. Most large telescopes will have a very hard time pulling off this feat unless the optics are very good.

Deep sky is as you would expect from a 12 inch telescope. The great optics in this scope combined with a relatively small secondary obstruction produces deep sky/planetary views that are of very high contrast. Nice! Having a dual speed focuser on this instrument is helpful for focusing since the telescope focuses so sharply. The globular cluster M13 is a myriad of pinpoint stars. M42 in Orion is spectacular. All six stars in the trapezium are routine in just average seeing. The beauty of Saturn is off the scale. Last year during an observing session in June, the Cassini division could be detected even though the Saturn ring tilt was only 1.7 degrees. This year was even better. Jupiter is stunning with more details than you can draw. The moons of Jupiter are disks of differing size with hints of details on nights of very good seeing. When I observe the moon I have many high resolution targets that I like to look at. One, the crater Archimedes, has three main pits on its floor that can be difficult to see. The XT12g will not only reveal the three main pits but will also resolve the many finer pits that cover its flat floor. The central rille in the Alpine Valley has been well seen.

As far as the GOTO Dobsonian mount is concerned, the performance is good if you use just two stars for alignment but improves greatly if you add more alignment during the observing session which is easy to do. The mount must be level for good GOTO performance though. I have observed many objects that I would have not spent the time to look for if I had to star hop to them. Setup and tear down is easy for such a large telescope.

My XT12g is an excellent overall telescope. If they are all this well made, this telescope, for what it can do as a visual instrument, is an excellent deal. I hope this info is beneficial to anyone contemplating purchasing one of these.