jdlopez's Full Review: Orion SkyQuest XT8 Dobsonian (480 x 203mm) Telesco...
, as many have always had an interest in astronomy.† But this past year, I was talking to a co-worker and we got on the topic.† He explained how a couple of years back when Tasco's Miami facililty was leaving town how he had purchased a couple of gun sights and a Newtonian telescope that he had never used.† He offered to give it to me, since he had no desire to pursue the hobby.† I accepted.
After about a week of trying to view anything, I figured the 3-inch reflector, and its rickety mount were a waste of my time.† I began researching on the Internet.† I found some very informative websites such as Cloudy Nights, Astro-Mart, Space.Com, etc.† From there I bought Terrance Dickinson's book Night Watch, excellent book by the way.† I downloaded a freebie off the Internet, Stellarium, and began learning some of the easier constellations (Orion, Gemini).† I had an old pair of binoculars, which helped somewhat, but I wanted more.
I narrowed the choices down to two scopes. Either an Orion XT6i or a Meade ETX-90.† As a beginner I felt a little intimidated going it alone and felt either the Intelliscope object locator or the Autostar Go-To computer would help me learn the sky.† After posting a thread on a message forum, I was pretty much set on the Orion XT6i.† Unfortunately I was able to get an incredible deal on a used ETX-90 and moved on impulse.
Don't get me wrong; the ETX is a nice little scope.† It afforded me the portability I sought.† The Go-To functionality was on the money.† And the 3.5" aperture performed admirably on the planets.† But apparently that wasn't enough.† After two months of use or so, I decided to try and sell the ETX and go back to the original plan.† I sold the ETX on EBay and actually made money.† With that and little added to it, I decided to buy the Orion Skyquest XT8i with the optional computerized object locator.
Dealing with Orion was a little difficult.† I placed my order online, and there were issues concerning credit card authorizations, pre-authorizations and several attempts at charging for the same item.† After 2 days on the phone, I was able to get the financials squared away, and the items shipped. After careful consideration along with the order from Orion I placed an order for 2 additional eyepieces from DBA Astronomy Products.† I purchased a GSO 2" Superview 30mm eyepiece and a GSO 1.25" Superview 15mm WA eyepiece.
The Specs for the Orion Skyquest XT8i are as follows:
Primary mirror:† 203mm diameter, parabolic, center marked
Focal length: 1200mm
Focal Ratio: f/5.9
Focuser: Rack-and-pinion. Accepts 2" and 1.25" eyepieces with included adapter
Altitude bearing diameter: 5.75"
Optical tube material: Rolled steel
Azimuth pad material: Teflon
Altitude bearing diameter: Ultra-high molecular weight (UHMW) polyethylene
Eyepieces: 25mm & 10mm Sirius Plossl, multi-coated, 1,25" barrel diameter
Finder Scope: 9x power, 50mm aperture, achromatic, cross hair, 5 degrees field of view
Mirror Coatings: Aluminum with SiO2 overcoat
Minor axis of secondary mirror: 47.0mm
Optical tube weight: 20.3 lbs.
Base weight: 21.3 lbs.
Tube length: 46.5"
Tube outer diameter: 9.25"
Product Arrival & Assembly
My order shipped out on a Thursday and arrived the following Thursday.† Not bad, I thought, since it was shipping from California and I live in Florida.† My order arrived in 3 boxes.† The Tube was shipped in a large coffin shaped box, the base shipped disassembled in a second smaller box, and the object locator and filter kit I purchased came in a third box.
I opened the largest box and inspected the tube and everything seemed to be good.† I did notice a small nick on the 2" to 1.25" eyepiece adapter, but not really a big deal. Inside the box with the OTA there was an additional box.† The additional box contained 2 eyepieces, the Finder scope and the Azimuth encoder board.† I'd like to also mention that the packaging of the eyepieces seemed to be sort of thrown together.† The eyepieces were not wrapped in plastic just placed in a cardboard box.† It almost seemed as if it might have been opened before.† Nothing was damaged, so I really can't complain. I opened the box that contained the components of the Dobson base. The foam in this box seemed to have been exposed to heat or something, as the foam was brittle and stuck to the Formica from the Dobson base. Nothing was damaged, so that wasn't a big deal.† I got some tools together and began to assemble the base.
I will mention that the instructions are little difficult to follow.† I work for a manufacturing firm where my primary responsibilities are in the design, manufacture and assembly of production machinery and tools.† When building tools and machinery at work, I normally work off of a schematic.† The assembly instructions for this telescope were written in a ėstep-by-step" format. The instructions included all of the steps necessary but often referred to components by names such as ėazimuth axis screw" but there was no reference as to which was the azimuth axis screw.† I had to figure it out through a process of elimination.† Also, when installing the bottom base assembly to the top base it asks you to ėSeat the bushing onto the encoder disk so that the registration feature on the bushing goes into the hole in the encoder disk."† Without a proper illustration, I can see where it could have been confusing.† An additional issue was 3 missing wood screws that attach the plastic feet to the ground base plate.† I happen to have an extensive collection of screws, nuts, bolts and washers and was able to find 3 screws for this.† It would have been a bummer if I had had to wait for Orion to ship the screws to me.
It took about an hour and half to build the base and install the tube. I took my time, carefully reading each step before assembling each component.† My overall impression at this point was this telescope seemed pretty simple.† I guess that was the idea John Dobson had when he designed this type of base. The overall quality of the telescope seemed good to fair. I figured that's why those scopes with Mahogany or Oak bases cost much more. Movement in both Altitude and Azimuth directions were smooth.† The altitude tension knob works well to control the altitude motion.† I could see why this would be an ideal scope for a beginner and the seasoned astronomer alike.
Collimation
One of the things that were a little intimidating was the thought of having to collimate the optics.† Boy was I wrong!† Collimation was very simple using the supplied collimation cap and instructions provided within the manual.† The secondary didn't need adjustment, but the primary was a tad bit off.† A couple of turns on the collimation screws and that's all it took.† I was done in less than 5 minutes.† I would imagine if the secondary were out of alignment, it would have taken a little longer, but I think the secondary is in there pretty stable and don't know how often it will need adjustment.
Alignment of the Finder Scope
This turned out to be more difficult than it was with my ETX. I have a six-foot wooden fence that encloses my backyard and I live in a relatively new neighborhood.† I couldn't find and object far enough to focus on.† I had to lug the telescope to the front yard and was finally able to find an object far enough to align the Finder Scope.† Did I mention how big the finder scope is?† It's almost the same size as my ETX's OTA!† Wow, very nice.
First Light(s) : April 8th, 9th, 2005
Strange thing was on April 8th at approximately 6pm EDT there was supposed to be a partial eclipse. It had been raining all day and sort of cleared up a bit in the afternoon, but at 6 pm the clouds were covering the sun, and I was unable to enjoy my first eclipse of any kind.† But a short 3 hours later, the sky was completely clear and still.† A great night to break in my new telescope!
I wondered how difficult it was going to be to place a Dobson telescope on grass.† I live in South Florida and have an average sized yard.† Not only was the Telescope not stable, but my lawn in not completely level.† I'm going to have to build a pedestal or platform for this telescope.† My only alternative tonight was to place the telescope on the terrace.† My house blocks the eastern sky, not ideal but it will have to do for tonight.
†I decided in advance that I would not be using the computerized object locator tonight.† I just wanted to get a couple of hours, and didn't want to find myself fumbling around with the new computer.† I figured I'd take a look at some of the objects I had looked with my ETX so that I could make a quick comparison.
Saturn : I viewed Saturn the most in the ETX I owned prior. I figured this would be a great first target since I would be able to make a quick comparison. Facing west I looked up and found Gemini, Saturn was just below and towards the South of Pollux.† I centered it first in the finder scope. Then, using the supplied 25mm Sirius Plossl I centered and focused Saturn in the eyepiece.† The focuser provides smooth movement back and forth.† Unlike the ETX, focusing adjustments are easy, and the image did not shift when focusing. Wow, Saturn looks very bright and sharp. At 48x I couldn't make out too much detail. I did notice right away, that the field of view in the XT8 is wider than the ETX-90. A lot wider! Although the view at 48x was pleasant, I wanted to see more detail.† I dropped in the 10mm Plossl re-centered it, and re-focused. Wow, at 120x I could start to make out Casini's Division.† The image remained tack sharp at 240x when I barlowed the 10mm.† Very impressive, since I couldn't push the ETX past 130x without significant image breakdown. At 240x I could see Casini's Division clearly as a dark line separating the 2 bigger rings. I could make out some surface detail on Saturn as well. I also noticed what I think were some of Saturn's moons.† I was a little bummed that I didn't have a higher-powered eyepiece so that I could push the Skyquest a bit further.
The one thing I will give to the ETX is its ability to track.† At 240x I was forced to nudge the scope every 30 to 60 seconds and watch Saturn drift across the eyepiece.† This was kind of difficult getting used to since everything is backwards.† My brain tells me that if an object is on the right side of the eyepiece I should push the scope towards the right.† Wrong way!† I'm sure this will take a little getting used to, but it shouldn't be a big deal.
Jupiter : Jupiter was simply stunning when I viewed it through the ETX.† Jupiter's two main equatorial belts could be easily seen as well as it's 4 Galilean moons.† Since I already had the 10mm with the Barlow in the focuser, I redirected the scope towards the southeastern sky.† It just broke the edge of my roof so I could take a look.† Wow! (Recurring theme, right?)† Not only could I make out the 2 equatorial belts, but also I could make out several other cloud belts to the north and south of the 2 main belts. I also observed what I think were 5 satellites orbiting Jupiter, but I'm not sure.† Very impressive!
M42 : Orion's Nebula -Now for the real test. M42 was one of the only DSOs that I had been able to detect on the ETX.† I wanted to see if the extra aperture was all that it was cracked up to be.† Well, let me start off by saying that prior to tonight, I felt that I lived in a lightly light polluted area.† Now, I'm under the impression that I live in a moderately light polluted area.† My house is located 30 miles south : south west of Miami, Florida.
In the ETX-90 M42 showed up as a dark-grey cloud with hints of cloud whips.† I could count 4 starts in the Trapezium.† So I decided to try the GSO 2" Superview eyepiece and see what I could make out.† This mammoth eyepiece is very impressive.† The image was sharp almost entirely up to the edge.† Just the very outer edge of the eyepiece showed a hint of distortion.† M42 resolved as a brighter object.† The clouds and whips were more prominent and detailed.† I had read that some people could see hints of green or red in M42; it showed up as a grayish cloud to me, with no hint of color whatsoever.† I decided to try the 1.25" GSO 15mm Superview eyepiece and was further impressed.† The 15mm seemed more contrasty and the extra magnification helped me resolve the trapezium's 4 stars.† I tried using an Orion Skyglow filter that I had purchased along with my telescope and noticed a small improvement.† The Skyglow allowed a little more contrast, but I wasn't blown away with its performance.† I will mention that after adding this filter I did notice some green color, but I think that color comes more from the filter than anything else.
Castor : Double Star : I'd read that the Mak design of the ETX was superior to a Newtonian on splitting doubles.† I figured I'd take a look and try to compare.† At 130x the ETX split Castor into 2 stars consistently.† The spacing between the 2 was very small, so it took some patience but you could make out the double.† The Skyquest split Castor easily at 240x.† The space between the 2 stars was more easily detected.† The 8" beat the 3.5" ETX hands down.
Computerized Object Locator : On the second night out, I placed a large stepping-stone in the middle of my lawn so that I could offer a more central yet stable place to use my new telescope.† Although the stepping-stone provided more stability, it seems not stable enough.† I tried using the intelliscope computer on my second night out with the intent to view some of the fainter DSOs that were so elusive to the Meade ETX-90.† I could not get the scope to align with an acceptable amount of accuracy.† According to the product manual after aligning the scope you get an accuracy result known as a ėWarp Factor".† A warp factor below 0.5 is acceptable.† I couldn't get a Warp Factor below 2 on my second night out.† I tend to think that this was the result of 2 things: my yard in not perfectly level it slopes a tiny bit, and the stepping stone I placed on the lawn did not offer a stable enough place.† I'm going to have to build a pedestal or stand to sit this Dobson on.
I moved the telescope back onto my terrace and tried to align it again.† I used Betelguese and Castor as my 2 alignment stars.† My first result was 41!† Hmm, I checked and noticed that the right knob on the base was loose.† That knob holds the altitude encoder in place so that would explain the crazy reading.† I tried again and got a Warp Factor of 0.6. Re-tried, WF 0.6.† Once again, WF 0.6.† Oh well, it was late, and I decided to take a quick look.† I tried M81.† Nothing. I scanned and scanned and same result, nothing. I tried different eyepieces, Skyglow filter all with the same result.† I'm not sure if I just wasn't looking in the right place, or if my skies are just too dark polluted but I could not see anything. Maybe I gave up too quickly, but I decided to give the guided tour function a try.† I tried everything, but no cigar.† Leo Triplets, nope.† Open clusters, nope.†
This is where I missed Meade's AutoStar.† Meade's GoTo computer seemed a bit more refined the Tours were based on Date and Time, while Orion's OL computer's tours were based on month.† The autostar tours had tons of objects to look at while Orion's OL Computer had only 10 or 15 objects.† Meade's Autostar had a wealth of information on just about every object.† I'm not sure if Orion's object locator has any of this info but I didn't fumble around with it long enough to figure it out.† I'm going to mess around with it prior to going outside next time so that I don't find myself trying to figure out the computer while I can be looking at the sky.
Conclusion
For the money, the Orion Skyquest XT8 is a good buy.† The 8" dobsonian telescope is just small enough that it isn't too difficult to move around.† The object locator will be a plus once I can figure out how to use it and align it properly. Meade's Autostar GoTo computer is better hands-down but the ETX's 3.5" aperture limits its ability to resolve DSOs.† The 8" of aperture make a huge difference when viewing objects at high magnifications such as planets.† I was able to make out details that were invisible to the smaller telescope.† The dobsonian base is easy enough to figure out, but its inability to track objects is a notable limitation that some beginner's may not like.† But when it comes down to it, what does every amateur astronomer get into the hobby for?† I think most of us want to see as much as possible.† I think this 8" telescope affords the ability to see objects better than a smaller telescope, which is why I'm glad I switched from ETX-90 to the Orion Skyquest XT8i.
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