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Orion SkyQuest XT6 (Intelliscope) Dobsonian

Out of the box, with just a simple, quick collimation, optics provide good resolution. The XT6 does a good job on double stars, but getting any significant detail out of the larger globular clusters with the XT6 is a bit dicey under "typical" city observing conditions. In a semi-dark location, clusters such as M13 and M22 yield a decent number of resolved stars with typical conditions. Smaller clusters such as M92, M15, and M2 are not so generous and require excellent conditions to show any detail. The XT6 splits the double-double with Orion's 15mm Ultrscopic combined with their Ultrascopic barlow. And in the moments of clear viewing, it can be seen that the split is quite clean. A star test looks good. I think the optics on this scope will make it a good planetary and double star scope, but I can't verify its planetary abilities at this time since the only view I've had of Saturn has been low in the sky on a so-so night.

After owning it for about three weeks, I decided to give it the full-blown optical alignment and collimation. In order to square the focuser with the secondary, I had to remove two of factory screws and use #8 half-inch screws so there would be sufficient length to permit shimming one side of the focuser with two #8 washers on each screw (i.e. four washers total). After the deluxe alignment and collimation, the detail visible through the scope was excellent. Even on nights of mediocre viewing, powers of 200X - 250X are supported with no problems, and close doubles are easily split. It seems like these f/8 six-inchers, when they have been carefully aligned and collimated, are tough to beat when it comes to splitting close doubles and showing detail.

I do have some complaints about the mechanical qualities of the scope.

The mount is rather stiff, probably because the spring tension supplies a little too much tension. When adjusting altitude, there is a tendency of the bearings to initially resist movement then suddenly break loose causing you to go past your target (I think this is called "stiction".). I haven't gotten around to it yet, but I intend to move the teflon base pads a bit closer in to the center to make azimuth movements a little easier; either that or do the milk carton thing.

The focuser is terrible: Being plagued by a ridiculous amount of slop, it's easily the worst I have ever used on a scope (worse than those plastic Meade jobs). There is so much slop in the fit that objects shift considerably when adjusting the focuser in and out. Tightening the tensioner just makes things worse because this presses a plastic bar against the eyepiece tube, and the plastic grabs the drawtube and makes it rock back and forth even more as you turn the adjuster knob back and forth. This also effects one's ability to collimate. With a laser collimator, the red dot will move at least an inch on the main mirror when the focuser knob is turned back and forth. And, as already mentioned, it required a hefty amount of shimming to square the focuser with the secondary. I found that collimating with a Cheshire eyepiece gave the best results. The primary mirror comes with the center already marked -- a nice feature.

I was able to solve the slop by shimming the focuser drawtube with the "vel" part of velcro strip with adhesive backing. I cut two narrow strips from a larger strip and stuck these narrow strips inside the focuser body. After I did that, it occurred to me that sticking a single strip to the tensioner bar might work too. I also cleaned out some chrome chips that had flaked off in the gear mechanism. The shimming and the clean out (mostly the shimming) made a world of difference. I'm wondering if there should have been some additional teflon shims that the manufacturer "forgot" to insert. It's possible that all shimming I had to do to the drawtube is partially responsible for extra shimming of the focuser body in order to get it squared with the telescope.

The instructions mention a 2mm hex key for the smaller adjusting screws on the secondary mirror. On the scope I received, the fit of a 2mm hex key (not supplied with the scope) was so loose as to make me doubtful that these were hex screws. After some experimentation, I found the fit of a 5/64 inch hex key to be correct.

The dinky finder scope is essentially worthless (why do they make these things?). If you don't have one of those red dot finders, get one (and figure the cost of one into your total investment in scope). I'll never understand why dealers don't sell the telescope at a reduced price without options and offer some option packages, at special pricing, for eyepieces and finder scopes so you can decide on the quality and price of the accessories you want instead requiring you to pay for lame accessories and eyepieces you don't want. If they only knew how many scopes I have NOT purchased because I didn't want to pay for the junk accessories. (end of editorial)

Stray light seems to be more of problem with the XT6 than with my 10-inch Dob. My house is located close to an expressway where overhead viewing runs about mag 2.5 give or take a bit. My viewing location is only slightly worse than a Wal-Mart parking lot; so I have LOTS of stray light! I've always read that the smaller Dob should be less affected by city light than the larger Dob; but my experience has been just the opposite. When trying to resolve globular clusters, the stray light does pose a real problem.

For those debating if a 6-inch scope is big enough, some thoughts:

My 10-inch Dob is an excellent Synta-made unit from Oceanside (www.optcorp.com) (essentially, the same thing as the XT10). I have looked through a fair number of 8-inch Dobs and SCT's; and, for deep space observing, the larger scopes do pull in more stuff and resolve more deep space detail. In a crapola viewing location (such as my house), all the extra light negates much of the advantage of the larger scope. But when I go to darker locations, I find that I spend A LOT more time with the 10 than with the 6. So part of your decision should be based on the conditions under which you will use the scope.

I have split the double-double with the 10 only under exceptional conditions. However I, and those who have looked through it, think it shows very good, sharp, images in general. It's relatively short focal ratio (f/5) makes it much touchier about alignment and collimation, and the aperture probably makes it more sensitive to atmospheric turbulence. The 6 is very forgiving of less-than-perfect collimation and routinely splits close doubles with no problems. But in a dark location, the 10 can reveal detail in those deep space objects that the 6 cannot. Also, the two-inch focuser on the 8- and 10-inch scopes is a BIG advantage. Looking through a big, wide-angle eyepiece like the University Optics 40mm Konig MK-70 gives a huge "portal into space" that the 6 can never do (in its stock form). So part of your decision should be based on what you want to spend most of your time looking at -- a case of "the right tool for the job."

Then there is the issue of size and portability. The 10-incher is not much smaller than a 30-gallon hot water heater (non energy efficient model). With the XT6, I can stuff a couple of eyepieces and a barlow in my pockets, grab a stool in one hand (Harbor Freight sells a good pneumatic adjusting stool for about $20), and grab the scope in the other hand. I can grab everything in one trip out of the house.

If one is going to have only one scope and is debating about the size, even though I don't have an 8-inch scoe, I think an 8-inch scope seems like a good compromise between the portability, ease of collimating at least "close enough for government work", sufficient aperture to show some deep space detail, and the ability to give big, rich-field views. For example, the Orion XT8 weighs only about four pounds more than the XT6 (if Orion's published specs are correct), so you have only a little less portability. One thing I do miss with the XT6 are those big, rich-field views that a 2-inch focuser allows when using big, wide-angle eyepieces. Besides providing lovely views of the Milky Way that the XT6 can't come close to matching, those wide views make things a lot easier to find (DEFINITELY an important consideration for somebody learning to navigate the sky). If all you ever did was planetary or double star viewing, then the lack of a 2-inch focuser would probably never be missed. But you WILL eventually want to do some deep sky viewing; and the first time you ever get an eye-full of what a big, 2-inch, wide-angle eyepiece provides, you'll wonder how you ever got along without it.

Optically, the XT6 is excellent, especially after you give it the deluxe alignment and collimation treatment. Detail is fine, but I find the aperture and overall light gathering to be just under what is required to show any significant detail in glubular clusters or for reeling in a nebula (at least to satisfy my tastes). In this aspect, the 10-inch beats the XT6; but the XT6 can split close doubles that the 10 cannot (usually). Mechanically, the XT6 has some rough spots; most notably, a sorry excuse for a focuser on the one I received. And you are paying for a rinky-dink finder scope that you will end up replacing.

Overall, this is a fine scope for when you want something portable, for splitting doubles, and (I suspect) for planetary work. On deep space stuff, the 6-inch aperture is somewhat limiting if you have easy access to a dark viewing location, but you can still see quite a bit with it. If you are forever stuck in a piss-poor viewing location, then the XT6 will probably be just about as good as the larger scopes.

Overall Rating: 7
Optics:8 Mount:6 Ease of Use:8 Value:8
Weight: 20 (Notable Vote)
Date: 10/16/2002 06:39:33 am PST
By: percy_smogg
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=129519

I must say I'm surprised at the lack of quality of your XT6's focuser (image shift).  I went through three products before purchasing my XT6, and returned them all with the focuser being extemely poor in all three.  One was a Celestron refractor, and two were from Meade, both reflecters.  All three of them had an EXTREMEM amount of image shift when I focused in or out, and the Meade focuser was obvious after thought cheap plastic junk.  The instant I first focused with my XT6 is was so overwhelmingly obvious it was better than my previous purchases I knew (or assumed) the rest of the scope would prove as nice, which it did.  Granted I'm an extreme amateur, I still can spot obvious differences in workmanship.  I'm willing to bet if you called Orion they would be happy to exchange your scope.  



>Optics provide good resolution; but my other six-incher, the Celestron CR150HD refractor, shows slightly more detail (albeit with a purple halo around bright objects).  The XT6 does a good job on double stars, but getting any significant detail out of the larger globular clusters with the XT6 is a bit dicey under "typical" city observing conditions.  In a semi-dark location, clusters such as M13 and M22 yield a few resolved stars with typical conditions.  I suspect it would take exceptional conditions to dig any stars out medium clusters such as M92 and M15.  The XT6 splits the double-double with Orion's 15mm Ultrscopic combined with their Ultrascopic barlow.  And in the moments of clear viewing, it can be seen that the split is quite clean.  A star test looks good.  I think the optics on this scope will make it a good planetary and double star scope, but I can't verify its planetary abilities at this time since the only view I've had of Saturn has been low in the sky on a so-so night.
>
>I do have some complaints about the mechanical qualities of the scope.
>
>The mount is rather stiff, probably because the spring tension supplies a little too much tension.  When adjusting altitude, there is a tendency of the bearings to initially resist movement then suddenly break loose causing you to go past your target (I think this is called "stiction".).  I haven't gotten around to it yet, but I intend to move the teflon base pads a bit closer in to the center to make azimuth movements a little easier; either that or do the milk carton thing.
>

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