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Orion SkyQuest XT8



Untitled Document

Orion SkyQuest XT8

by by Peter Argenziano (pargenz@earthlink.net)

  • Price: $479 (USD)
  • Type: Newtonian Reflector
  • Mount: Dobsonian
  • Aperture: 203mm (8”), f-ratio: 5.9, focal length: 1200mm
  • Weight: 42 lbs. (Base 23 lbs. Tube 19 lbs.)
  • Included: Collimation cap, eyepiece rack, 6x30 finder scope, 10mm Plossel eyepiece, 25mm Plossel eyepiece, 'Where the Stars Are' astronomy software on CD-ROM
  • Dealer: Starizona in Tucson, AZ.

Being a relative newcomer to astronomy, I decided to begin my foray into this new hobby slowly. I started my viewing with a pair of 7x35 binoculars. I was amazed by what I was able to see with them. Of course, this instilled the desire to obtain a telescope.

Having a modest budget for this new hobby, I decided that the best course of action would be to conduct intensive research before making a purchase decision. Over the next few months, while continuing to gaze through the binoculars, I embarked on an information seeking campaign. I read such books as: 'Turn Left at Orion', 'NightWatch', 'The Practical Astronomer' and 'StarWare'. I read Sky & Telescope and Astronomy magazines. I scoured the internet. I joined a local astronomy club.

Most of what I read recommended that I define what I wanted to view prior to making any decisions on equipment. I knew I wanted to view the planets. I also knew that deep sky objects held special appeal. Astrophotography also interests me, but that will have to wait - a visual experience is the immediate desire. I knew that modest aperture would be necessary. After a long, detailed, exhaustive investigation I decided on the Orion SkyQuest XT8 Dobsonian. What follows is my review of this telescope.

While I could have purchased this telescope directly from Orion, I chose to support a local dealer. Orion is highly regarded in the industry for outstanding customer service, but I like the idea of working with a local dealer. I chose Starizona in Tucson - about 100 miles from home. While there is a closer Orion dealer, the price from Starizona was better (identical to purchasing directly from Orion)

I called Dean at Starizona to see if they had an XT8 in stock, and by the time I arrived he had it fully assembled and collimated. I also purchased a Celestron Ultima Barlow and a Telrad (which Dean also installed). Dean also helped me with a slight mechanical problem with my Jeep - but that's a story for another time! Gotta love dealer support!

My normal observing location is my backyard; a slightly light-polluted suburban place southeast of Phoenix. The skies to the south and southeast are usually dark.

The telescope is easy to operate: movements in altitude and azimuth are smooth (azimuth movements are slightly stiff near zenith). With Orion's Correct-Tension (springs) on the altitude bearings, the scope always stays where it is pointed. I have experienced no problems with unwanted movements, even with the finder scope, Telrad, and a Barlowed eyepiece in place. Moving the scope to the observing location is relatively easy, given that a large handle is mounted on the back of the rocker box. However, the placement of the handle is below the center of gravity. The tube wants to swing upwards when you try to pick it up. I solved this problem by positioning a web belt around the base and tube while it is 'in transit'. I have also installed a retrofit for smoother azimuth movements. This modification consists of the addition of six 'milk jug washers' on the central bolt between the upper and lower baseplates. This fix was outlined in Sky & Telescope magazine. The washers provide a slight amount of lift to the rocker box, alleviating some pressure on the Teflon pads. I also loosened the tension on the central nut, and keep a 9/16" wrench in my accessory case for in-field adjustments.

The tube is constructed of rolled metal with a black enamel finish. It is painted flat black on the inside. The end caps are cast aluminum, making for a very nice looking product. The tube has what Orion calls a navigation knob at the top. It is quite convenient for positioning the scope, especially when tracking a planet. The dust cap (included) fits snugly atop the tube. A shower cap keeps dust (and spiders) out as well.

The rocker box is constructed from black melamine over particle board. It is quite sturdy, even if it is hard to see in the dark. An eyepiece rack is mounted to the side of the rocker box, which will hold four eyepieces (three 1.25" and one 2").

The primary mirror is mounted on an aluminum cell that allows for some movement of air. It is usually acclimated after a hour of cool-down time. Of course, this is wintertime in the desert. The primary is factory center-spotted and has three spring-loaded thumbscrews to facilitate collimation.

The secondary mirror uses a four-vane spider assembly. The vanes are quite thin so as to introduce a minimum of obstruction while providing firm support.

The cast aluminum focuser is a rack-and-pinion design. It is 2" with an included adapter for 1.25" eyepieces. In fact, all of my eyepieces are 1.25". Someday I would like to get a low-power 2" eyepiece. The focuser movements were somewhat smooth, however the grease that Synta uses is quite sticky. I cleaned all of the grease off of the rack and pinion gear and replaced it with a silicon grease obtained from a SCUBA shop. Now racking the focuser in and out is very smooth. The focuser has two very small setscrews to adjust the position of the draw tube, relative to the assembly. Practically all play can be eliminated with minor adjustments. The focuser also has a thumbscrew to lock the position. The standard-issue focuser knobs are small, black plastic. A big improvement in focusing action and feel is achieved with the addition of aluminum knobs from focusknobs.com.

This telescope is quite easy to collimate using the tool available from Orion. While collimation hasn't yet been necessary - even after the drive back from Tucson on the back seat in my Cherokee (seat-belted, of course) - I had to try it anyway. I read the instructions that accompanied the collimation eyepiece and checked collimation. Everything looked good. So, I purposely misadjusted things and quickly brought everything back into proper alignment. The star test appears as it does in the online and magazine descriptions, concentric and identical on both sides of focus.

The views provided by this telescope have been incredible. I have looked through other scopes, and it is my opinion that the XT8 has good optics. While I don't have years of observing experience, I can honestly say that my expectations have been exceeded. My eyepiece collection includes 7mm, 10mm, 15mm, 25mm, and a 32mm (all Plossls except the 7mm orthoscopic). The details available of the moon, Saturn and Jupiter are only exceeded by the deep sky objects I have located. I am really looking forward to taking the scope to a dark sky site… which I am planning to do in a couple of weeks!

All in all I am quite pleased with this telescope. It is well designed and nicely balanced. It delivers good optical performance. It is quite easy to move, considering its size. On a scale of one to ten, I would rate this scope a ten. It represents an outstanding value and an excellent first telescope.




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