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DM-4 or DM-6?

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#1 Dragonwatcher

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Posted 02 May 2011 - 11:59 PM

I am thinking that I might one day want to buy at DM-4 or DM-6 for my Borg 125SD. The Borg weighs under 10 pounds with focuser & is a F/6. I know that the DM-4 in conservatively rated for 15 pounds.

Is the DM-6 going to be ridiculous overkill? Will it still be smooth with a lighter weight telescope (I assume so as you adjust tension...)?

Would I be pleased with the DM-4 or would I find the DM-6 to give me an extra luxury I would appreciate?

If I could be very happy with the DM-4 that would be a great advantage in both $$$ and weight. The DM-6 is definitely much heavier.

I have a Quarter Hitch now on carbon fiber Gitzo 5531S. I was disappointed recently with how badly my Borg shook in the wind. It is pretty nice in calm conditions if balanced EXACTLY but changing EPs of different weights can easily throw the balance off. I suspect the tripod (though rated for 55 pounds) and the Quarter Hitch are just at the edge of what they can comfortably handle. If I use my Earthwin binos (filters/power switch), I think I would definitely stress the outfit. I'm thinking such a setup could also stress the DM-4????

I like the idea that with Discmounts allow you to change EPs of pretty different weights & still not require re-balancing.

Thoughts?

#2 tonyt

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Posted 03 May 2011 - 02:19 AM

If you want to save some money you can be confident buying a used Discmount. There are so few moving parts and they're so solidly built that hardly anything can go wrong. My used DM6 was a little sticky when I bought it but Tom guided me through disassembly and cleaning of the discs and it's like new again.

#3 coz

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Posted 03 May 2011 - 04:58 AM

I use a dm-4 with a 15 lb refractor and it works great.

#4 mountain monk

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Posted 03 May 2011 - 09:40 AM

Talk to Tom Peters at Discmount. He's an honest, open guy who you can trust to help you make the best decision. I have the DM-6, but a DM-4 is in my future. They are both great mounts.

Dark skies.

mm

#5 Dragonwatcher

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Posted 03 May 2011 - 10:29 AM

I thought of calling Discmount, but if I buy one or the other, it would have to be used because I can't stretch the budget to new. So I don't think it would be fair to take Tom's time when he would make no money on the transaction.

#6 AhBok

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Posted 03 May 2011 - 10:51 AM

You don't know Tom. He is a delightful guy and will be glad someone is purchasing one of his mounts used.

BTW--I have a DM-4 with my SV115 triplet. Fully outfitted, it is about 15 lbs and the mount is a perfect match. When Discmounts users tell you vibrations settle in under a second, it really does mean under a second. I chose the DM-4 for greatest portability. If you don't mind the extra size a weight (still very portable), I would say get the DM-6 for your scope.

AhBok

#7 Herenomore

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Posted 03 May 2011 - 11:17 AM

Dragonwatcher:

Tom Peters recently got an AP130GT which weighs 20 or so lbs with everything up on the mount. Below is a picture of it on a DM-4 and Tom (who is very conservative about these things) told me that the DM-4 handles it very well. As to your question about the DM-6 being overkill, the DM-6 will certainly well handle what you have and give you a whole lot of headroom if/when you go bigger.

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#8 Dragonwatcher

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Posted 03 May 2011 - 11:36 AM

Thanks to all. What I am hearing is that the DM-4 should work well for my current needs - but the DM-6 has no downside other than heavier weight and higher cost. It would allow a heavier set-up if I ever went that direction (like my dream scope of a Tec140 if I ever moved into a rambler with a concrete patio & open views).

#9 Scott99

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Posted 03 May 2011 - 12:06 PM

you might consider the Tak Teegul as well. It had no problem with my 10 pound FS102 tube - 32 inches long focal length, similar to the Borg.

Besides have nice slo-motion controls, the Teegul also holds the scope fairly high off the tripod. You can often get by without using a height extension.

the 5 inch Borg looks like an interesting scope - let us know how it works for you!

#10 Wayne W.

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Posted 03 May 2011 - 12:40 PM

I have the DM-6 and find it works best with larger and heavier scopes. Smaller scopes that weigh less than say 12lbs to me just seem to be less smooth than scopes that weight more. Just my observation. I would recommend going with the DM-4 for your Borg 125SD. The DM-6 is quite heavy and needs a substantial tripod to support it. The DM-4 is alot lighter and more of a grab and go. Clear skies

#11 JMW

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Posted 03 May 2011 - 01:06 PM

I have both. I mostly use the SV-115T on them. The DM-4 on my Gitzo 5541LS is my very light grab and go mount. It takes up very little space in the car and is a wonderful setup. I have a collection of very heavy eyepieces and they push the DM-4 to its limits. The Ethos 17 and 21, Nagler 31T5 and Panoptic 41 all weigh more than the DM-4 weight change limit.

If I am going to a public star party or not concerned about the size of the setup, I take the DM-6. I use it with Losmandy pier extension on top of a Berlebach planet. This setup doesn't require that I hold the scope when doing heavy eyepiece changes and is impossible for the public to knock over.

Both mounts are great and pan smoothly across the sky with my eye looking through the eyepiece.Except for imaging or high powered planetary viewing, I think these mounts are the best.

#12 Dragonwatcher

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Posted 03 May 2011 - 01:47 PM

Update: I am going to talk to Charles at Half Hitch about the possibility my wind movement was due to my tripod and the fact I may not be balancing my telescope correctly on two axes. So perhaps I am just not utilizing the QH to its full potential due to user error. It has worked great in typical weather with very smooth movements. At the star party I pushed it by changing from a 3.7mm Ethos to a 5mm Pentax XO with frequent strongish wind gusts.

But I definitely will be upgrading some time in the near term future, no matter what, as I need encoders and push-to capacity. So I guess I need to weigh the pros & cons of a Discmount versus a Half Hitch.

#13 Renae Gage

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Posted 03 May 2011 - 01:50 PM

When considering at Discmount, the tripod matters at least as much if not more than the head. The DM-4 would be plenty for your scope, but don't skimp on the tripod.

#14 Doug D.

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Posted 03 May 2011 - 02:36 PM

Update: I am going to talk to Charles at Half Hitch about the possibility my wind movement was due to my tripod and the fact I may not be balancing my telescope correctly on two axes. So perhaps I am just not utilizing the QH to its full potential due to user error. It has worked great in typical weather with very smooth movements. At the star party I pushed it by changing from a 3.7mm Ethos to a 5mm Pentax XO with frequent strongish wind gusts.


I bet Charles is right about the balancing but I don't think your tripod is likely the limitation given the modest payload of the Borg. I have the same tripod that you do and use it with a Half Hitch II. I use it with a 105 Traveler but it is a fairly heavy scope with binoviewers and the new balancing aid that Charles came up with - although not sure how close in weight to your Borg (of course length and moment arm matter as well).

In any event, before giving up on the mount and tripod I would make sure it is balanced as Charles suggests but I would also make one more suggestion. Hang something heavy off the underside center of the tripod (is there a hook on yours?) like a weighted backpack. The Gitzo CFs are indeed very light weight and your back thanks you for that, but the physics is such that a little extra mass will have a stabilizing effect. I find it makes a big difference in damping in wind to have some weight bearing down between those legs and indeed, Gitzo designed these tripods with the "on site addition" of some ballast in mind.

The 5531s is a pretty substantial tripod. The DM-6 is like a bowling ball weight-wise and you will need either one of Tom's tripods or a G11 or similar tripod (e.g., one of the larger Berlebachs) to take full advantage of it. I think about a DM-4 myself now and then and if I were to get one I wouldn't hesitate to try it with my G5530S. But I've been happy with the HH and after owning a DM-6, I'm happy happy to stay with the HH. I'm not knocking DM mounts at all - they are great but the smooth movements, "slow-mo" controls and weight of the HH edge out the DM for me, at least for my particular scope and viewing needs. It is a bit fussier than a DM perhaps but worth it to me.

#15 skybsd

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Posted 03 May 2011 - 02:42 PM

Update: I am going to talk to Charles at Half Hitch about the possibility my wind movement was due to my tripod and the fact I may not be balancing my telescope correctly on two axes. So perhaps I am just not utilizing the QH to its full potential due to user error. It has worked great in typical weather with very smooth movements. At the star party I pushed it by changing from a 3.7mm Ethos to a 5mm Pentax XO with frequent strongish wind gusts.

But I definitely will be upgrading some time in the near term future, no matter what, as I need encoders and push-to capacity. So I guess I need to weigh the pros & cons of a Discmount versus a Half Hitch.


You definitely need to speak to Charles.., Your issue isn't the mount, its the tripod.

Basically you need a heavier set tripod.

I use Berlebach UNI tripods for my Alt-Az mounts and can highly recommend them..,

Regards,

skybsd

#16 Dragonwatcher

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Posted 03 May 2011 - 05:41 PM

Well, I did speak to Charles and I am convinced some tweaking of tripod & balancing should do the trick. Still leaves me wanting encoders & Sky Commander, so QH with, HH with, or DM-4 with Sky Commander?

#17 mistyridge

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Posted 03 May 2011 - 07:02 PM

I use my DM-6 with a my SV115T and SV70ED plus 50mm finder and Telrad. total wt about 26lb all with no problems. I know I know it could carry my C11. The DM-6 and tripod only weight about 30lb.

#18 jason_milani

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Posted 03 May 2011 - 10:34 PM

I have had two Half Hitches (Mark II and Mark III)and a Discmount DM-4. The Discmount was the smoothest push-to mount i'd used until i used the Half Hitches. But balancing is critical with the Half Hitch and not so much with the DM-4. I do like the fact that the Half Hitch balances the scope over the center of the tripod other than on the side. When i had my Half Hitches, though, i could never get a C-8 to balance properly even with the up - down axis adjustment. With the newer balance trimmer extension that issue is hopefully worked out.

#19 Dragonwatcher

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Posted 04 May 2011 - 12:31 AM

Jason,

If you had to choose between the DM-4 and the Mark III for your 6" Skywatcher (it's listed at 11 pounds for OTA), which would you choose if cost was not factored in, only performance?

#20 skybsd

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Posted 04 May 2011 - 01:08 AM

Hello Jackie,
Good to hear from you..,

Well, I did speak to Charles and I am convinced some tweaking of tripod & balancing should do the trick. Still leaves me wanting encoders & Sky Commander, so QH with, HH with, or DM-4 with Sky Commander?


As I said, as far as your stability issues are concerned, its the tripod - not the mount.,

I know that Charles only included encoder-compatibility later on so he's best placed to say whether or not your current model can be upgraded.

If not, then its clear that you need to look either at swapping yours for one that is, or perhaps elsewhere..,

Regards,

skybsd

#21 Doug D.

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Posted 04 May 2011 - 07:02 AM

Before replacing the Gitzo try hanging some weight - there couldn't be an easier tweak to at least try.

I have owned a UNI-24 and one of Tom's tripods (used for a DM-6) and I still have an AP/Baader in addition to the Gitzo 5 series. While I can't claim to have done a careful comparison under gale force conditions, my impression with the HH and my 105 w/binoviewer was that there was little little to distinguish the UNI-24 from the G5530S with regard to damping times when used with my HH II (but a lot to distinguish in terms of portability, set-up, etc.). The situation changes with the AP/Badder as it would with a Berlebach Planet- or Sky-class tripod (or a Losmandy G11 tripod). These tripods are in a different performance class because of weight and size in addition to good design - but you pay for that, of course, in weight and size.

Assuming a well designed tripod utilizing legs with good torsional rigidity and a material with superior ability to damp vibrations (e.g., wood and CF) the key becomes the mass of the tripod. The G5531 weighs a lot less than my AP/Baader and is a heck of a lot more portable. Sure, you can put the HH on a beast like the Losmandy G11 "tripod" or even the AP/Baader if you want, but to me it kind of defeats the original intent of the HH as a high performance grab and go mount. Otherwise, I'd prefer to just get out my GEM and be done with it.

One "benefit" of the DM-6 that I never really hear touted much is the weight of the thing. It de facto accomplishes what I am suggesting you do to improve the performance of your Gitzo w/QH (add significant compact weight to center of the tripod). But I still prefer the OTA centered over the tripod as in the QH/HH design.

#22 jason_milani

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Posted 04 May 2011 - 07:03 AM

Jason,

If you had to choose between the DM-4 and the Mark III for your 6" Skywatcher (it's listed at 11 pounds for OTA), which would you choose if cost was not factored in, only performance?


Actually my Skywatcher is the f/8 version (the 11 lbs. must refer to the f/5 version) and it's over 20 lbs. with the Moonlight focuser on it so i would use neither mount for it. I was using it with a Unistar deluxe but the standard surveyors tripod i had it on was not beefy enough. Now if someone handed me the new Super Half Hitch i wouldn't turn it down. ;)

Put it this way: if you want the smoothest mount available get a Half Hitch. But you'll need to fuss with it somewhat. If you want a smooth (but not the smoothest) mount that is totally hassle free get a Discmount.

#23 Doug D.

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Posted 04 May 2011 - 07:07 AM

Put it this way: if you want the smoothest mount available get a Half Hitch. But you'll need to fuss with it somewhat. If you want a smooth (but not the smoothest) mount that is totally hassle free get a Discmount.


Exactly - in a nutshell.

#24 Dragonwatcher

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Posted 04 May 2011 - 11:15 AM

Thanks for the great responses.

Yes, I see the little hook under the tripod, so I am definitely going to hang some weight off the tripod the next windy day. I truly feel that stabilizing the tripod & balancing properly will make the QH very stable. It had to be a problem with my not handling the equipment properly. I also found that the mount attachment to the tripod wasn't as tight as it could be, so I tightened it up.

I will use my QH happily until I can get either a Mark III or DM-4 used. I really want a push-to.

#25 Doug D.

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Posted 04 May 2011 - 11:36 AM

Might also want to consider a T-REX although it is closer to the DM-6 in terms of weight and capacity.






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