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The DM-6: Stability and Simplicity

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The Alt/Az DM-6 from Discmounts.com

DiscMount Hots
DiscMount Nots
Great stability
Easy hand tracking at high powers
DSC compatible
Switching eyepieces without going through the seesaw shuffle
High quality of construction
Uses Losmandy G11 Dovetail and Plate system
Small footprint when traveling
DiscMounts willingness meet their customers needs
Did I mention the great stability?

DiscMounts.com has come up with a better mousetrap.

I’ve long been a fan of alt-az mounts. There’s just something about a simplicity of design that encourages you to take a small scope out and star hop across the summer milky way, through the virgo cluster, or around the celestial pole (a location where traditional GEM’s have problems). Where they typically fall down is when it comes to high power viewing. Having to reacquire the object with a high power eyepiece is never fun, and many of the alt/az mounts just aren’t stable enough to handle high powers well. When I learned that Tom Peters from DiscMounts Inc had contacted CloudyNights.com about submitting the DM-6 for review, I was only too pleased to undertake the task and put it through its paces with my TV102. Ironically, I had been on the DiscMounts web page just the day before.

Just in case you aren’t familiar with the DM-6, I’ll take a moment to describe it: From the pictures, it can be a little deceptive – it’s a little bigger than it appears. The head is extremely compact and resembles a black cube with a large disc mounted on the bottom and side. The head is about 6 inches on a side – indeed, the bearings are 6 inch bearings. Hence the name DM-6 = DiscMount 6. In a slight twist from a typical mount, the telescope connects to the side of the head using the Losmandy G11 saddle plate and dove tail system. The DM-6 head itself rests on an extremely solid ash tripod. Remove the top and back covers of the DM-6 and one can see the 4000 tic encoders that are optionally available, as well as a magnetic strip that holds the wrench used to adjust the tension on the axis with the tension nuts themselves being located just under the encoders and easily accessible. Just from the pictures one can tell that it’s compact, elegant, and zen all at the same time.

The DM-6 head with Sky Commander on top - (Note: the arrangement of the wires for the computer)

Tom Peters (owner of DiscMounts Inc) makes some interesting claims about the DiscMount, but the most appealing perhaps is the basic design philosophy of the mount itself. The DiscMount design is said to allow you to eliminate rebalancing when moving between heavy and light eyepieces. Because of the friction based disc assembly used to provide the bearings, locking the axis becomes completely unnecessary when changing eyepieces and the scope will stay on target. Smooth motions at high powers are promised, with the ability to go from a Pan 35 or Nagler 31 to an ortho or Nagler zoom without having to rebalance the telescope.

I contacted DiscMounts directly and made arrangements to have a mount (and all the accessories) shipped directly to me for this CloudyNights.com evaluation.

The mount shipped in two boxes: one for the head and one for the tripod. Both survived UPS with nary a scratch on them, and as I unpacked, I could see that they were both very well designed, and held to extremely high manufacturing tolerances. The pictures on Discmounts.com – as good as they are – just don’t do the mount justice. The machining and craftsmanship of the head shout quality from the first look. The tripod is coated with a clear lacquer finish that allows the beauty of the ash to show through – no stains or heavy varnishes on this tripod. The classic look speaks to the zen approach of the simple alt/az head. As you begin to go over the mount with a fine toothed comb, you find little touches that speak to the quality of the overall design.

On the tripod, the leg braces screw into each leg, and have a provision to affix them to the legs for storage. The top of the tripod is covered with a rubber and cork mixture, to provide a suitable perch for the mount head, and the head is itself is beautifully machined and anodized. The plates that hide access to the encoders snap into place via a cunning spring arrangement, and as I previously mentioned, an adjustment wrench for the axis tension is anchored into place inside the head with a strip of magnetic tape. DiscMounts offers many other options, including a bracket to mount your finder to the DM-6, and adapter plates for the Losmandy GM8 and GM11 tripods. No matter what options you wind up with, the attention to detail is evident throughout. Everything fits. And fits well.

Surprisingly, the mount and tripod take up very little room when traveling – slightly less in fact than the Gibraltar or Telepod head with the eyepiece caddy mounted to a comparable tripod. There are no counterweights or counterweight shafts to worry about, and if you head out to star parties packed to the nines like I tend to do, this is a definite plus.

Inside the DM-6 - (Note: the head has been offset on purpose in order to see the rubberized cork on the top of the tripod)

The tripod legs don’t extend, but DiscMounts does offer custom lengths – something you may wish to consider depending on your use. For a person of average height who will be using the mount terrestrially and astronomically, the tripod is just about the right height. For someone who is a little taller, or whose primary use is astronomical observing you may wish to opt for the slightly taller tripod – simply to place the eyepiece at a little more convenient height when you strive for zenith. If you are looking to purchase, I’d also recommend you inquire about an eyepiece tray for the mount.

And the big question: How well does it work? Splendidly. I found Tom Peters performance claims to be completely borne out. This is simply a superb mount. It does indeed allow you to switch from extremely heavy eyepieces to extremely light ones without adjusting the tension of either axis. The mount is extremely rigid, and sharply tapping the side of the telescope / mount resulted in the scope settling down extremely quickly. Even wind tends to present little obstacle to an observer. Even focusing at high powers resulted in very little shake. Ironically, the weakest link in the system showed itself to be the clamshell ring on the TV102. The DM-6 is a rock. Peters has tested the DM-6 with OTA’s up to 25 lbs in weight, and I can tell you my little 12lb TV102 was of absolutely no consequence.

Initial use of the system involved frequent axis / friction adjustments, but since the mount has had a chance to settle in, I haven’t had to touch it. Tom Peters related that he has one that he hasn’t changed the friction on in years. Once the friction is properly adjusted, and the scope correctly balanced, (and this process is covered in detail in the DM-6 manual) tracking is extremely easy, even at powers approaching 300x. The only times I ever wound up rebalancing was when I switched from binoviewing to monocular viewing, and I suspect that even this would have been unnecessary if I wanted to tweak the mount a little more, but since I don’t usually switch between modes, I never bothered. I found the ease in which you can go from a heavy wide angle eyepiece to a lightweight ortho or nagler zoom unparalleled compared to any alt/az mounts I’d ever seen. This is a mount that lends itself to detailed investigation of planets as well as to wide field scanning from the horizon to the zenith. While switching from low to high power I rarely lost the target, and on those occasions which I did, it had far more to do with the initial placement in the field of view than any weakness in the mount.

The Sky Commander mounted on the DM-6

DiscMounts Inc offers to set the mount up with encoders, and will gladly sell you a Sky Commander if you need one or you may use any compatible DSC system (Sky Tour, JMI, Argo Navis, etc). If you use the included mounting plate, which puts the DSC right on top of the mount head, the cables are kept to a minimum and stored out of the way inside the head itself. It’s a nice feature that effectively eliminates the problem of cord wrap, and yet another example of a well thought out and implemented design.

As for the orthogonality of the mount and the accuracy of the Sky Commander, it worked beautifully. Let me give you a specific example: I was lucky enough to have the mount during the Martian opposition and had a blast using the DM-6 night after night to study mars at extremely high powers. When I got tired of Mars, I would use the Sky Commander to pan over to Uranus and Neptune while staying at those extremely high powers. So – in short, it’s orthogonal. Period.

This is a mount that just gets out of the way and lets you observe.

I took the mount to several star parties with me, and without exception, every single person who looked at the mount was intrigued by it.

The DM-6 easily carries this TV102 and binoviewer

I wouldn’t want you to think everything was all beer and skittles - there were little things here and there I thought might be improved. Not much really, certainly nothing major, but I mentioned to Tom that it might be nice to see an eyepiece tray that drops in on top of the leg supports, and differing tripod heights would be a nice thing to offer. With the standard tripod I found myself sitting a little too low for my comfort when viewing near zenith. Ergonomically, some users might prefer the Sky Commander in a slightly different location, as I found it a little high to view comfortably when seated. Tom Peters met the challenge with each suggestion, discussing solutions, additions or redesigns with aplomb, shipping me new cables when I suggested I’d like to try the Sky Commander in a different location, and agreeing that eyepiece trays and different height tripods were good ideas, and hinting that they would indeed be available in the near future. Some manufacturers seem wedded to their products and refuse to admit even the possibility that their may be something that they can do for enhancement. In my opinion, the best, like Peters, are continually striving to innovate and improve.

The DiscMount Logo

So are there any drawbacks remaining? Well, yes, but just one. As is true of anything in this life, if you want excellence you must be prepared to pay for it. At a cost of $1200 for the head alone or $1550 for the head and tripod (accessories extra), this mount is no exception. But if you can afford the price tag, this is a perfect solution for people seeking the simplicity of an alt/az mount. Balancing form and function, Tom Peters has created a thing of beauty.

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