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Help! MI-250 non GOTO vs AP900 QMD

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#1 Steve Fisher

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Posted 17 August 2009 - 11:57 PM

Is anyone familiar with these two mounts? I would appreciate any direct comparison you could give. I am fairly familiar with the AP900 GTO but not so much the QMD. I have never laid eyes on a Mountain Instruments 250. It is hard to judge it's mass by pictures alone.

One mount in the $2,000.00 to $2,500.00 price range and one in the $4,000.00 to $4,500.00 range.

I have a new 8" f/12 D&G on it's way and while I have a few temporary mounts I want something that is easily transportable so I can take it on the road with me.

Your thoughts will be appreciated.

#2 Bowmoreman

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Posted 18 August 2009 - 05:06 AM

I can't comment per-se on the 900 QMD, but...

An MI-250 in the price range you mention would be a HUGE steal! Especially if it is Gemini GoTo...

The Byers gears in the MI-250 are wonderful; I'm getting 0.2" average error during guiding (5 second exposures), and have no problems guiding 5 minute subs at 2800mm focal length using a 100mm focal length STV eFinder (f4, 25mm aperure!)...

The MI-250 will easily carry 60-70#, is highly accurate, and breaks down pretty easily into ~35# pieces...

Also, you can always send it back to Larry at MI for a complete upgrade service to bring to latest specifications...

I've heard good things about the QMD's, but the non-goto was always a show stopper for me...

HTH

clear enough skies

#3 LLEEGE

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Posted 18 August 2009 - 06:39 AM

I'd get the MI and send it in for an upgrade. Something you can't do with the QMD.

#4 Steve Fisher

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Posted 18 August 2009 - 10:06 AM

Thanks for the information so far.

No, the 250 is not goto. At that price it would be stealing as you say.

Goto is not an issue for this scope. I have herd that the older MI-250's cannot be upgraded to Goto by MI. I'm sure there is something out there that would work but again. No Goto, "good to go".

I want a good stable mount on a 7' high transportable pier. The new 8" scope will only be taken away from home on special occasions but that's what I am after.

#5 Bowmoreman

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Posted 18 August 2009 - 12:46 PM

Well, it's still a very good price at that level, if you can function without the Goto...

I'm confident, based on the effortlessness that I'm having with my approx 40# load (for imaging) that it should be able to handle that scope for you... You will likely want careful balancing (duh), given it's sheer length...

but, with a good Casady or ADM type Losmandy plate, and solid rings, you should be all set.

I'd still give Larry a quick call to find out what can be done to such older MI-250's (if anything), just in case you find it to require servicing in any particular way... (and you might find out if it is feasible or not to upgrade to Gemini/GoTo - even if you don't wish to do so... that knowledge would be a valuable part of ascertaining value - for your purchase).

Clear enough skies

#6 HunterofPhotons

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Posted 18 August 2009 - 01:11 PM

.....I'd still give Larry a quick call to find out what can be done to such older MI-250's (if anything)....

Have the serial number for the mount when you call Larry. He'll have all of the information on the mount on file.
Find out if the mount will work at your latitude. You may need a different mount base.
Larry's newer mounts have lapped worms. It makes for smoother movement and the older mounts can be upgraded by Larry. It made a noticeable difference in my older mount.

dan

#7 George N

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Posted 18 August 2009 - 01:45 PM

........ I have herd that the older MI-250's cannot be upgraded to Goto by MI......


There have been plenty of posts on the MI Yahoo Group from Larry saying that the non-GoTo is not upgradeable to GoTo. The entire Dec section would have to be changed ‘cuz it has no worm gear and much of the RA section would need to swapped out. It would cost more than a new GoTo.

I’ve found no problem using my old MI-250 in ‘push-to’ mode for both visual and CCD imaging. The NGC-MAX-like unit is accurate enough to put any object onto the chip of my ST-9 and STL-1301 CCDs. I then use the slew to center the target.

I purchased the last non-GoTo made, with great difficulty. I found it at a store across the country. Because I do most imaging with this mount in remote locations with no AC power, I do not want a power hungry GoTo mount to add to the power budget of CCD and laptop.

I asked Larry why he no longer makes the non-GoTo and he said “because no one wants one!” For the same reason used non-GoTo MI-250’s sell for a lot less than used GoTo’s.

#8 DeanS

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Posted 18 August 2009 - 03:03 PM

I asked Larry about them a long time ago, electronics are no longer available, the boards are no longer made or serviced byt he original mfg.

Something to think about. AP can be sent back and worked on, electronics and all. The QMD can not be upgraded to goto either.

Oh, and the price of $4k sounds very high. I just had a friend buy a 1200QMD with pier and wieghts for $1700. Ask around they are out there and hard to sell so you should be able to get a better deal than that.

#9 Steve Fisher

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Posted 18 August 2009 - 03:05 PM

Thanks again you guys. This has been just about the kind of information I was looking for. I still wish someone would chime in who has used both but........

A couple more days before I have all the funds to get the new mount but I'm within a few days of having to make up my mind.

#10 gnowellsct

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Posted 21 August 2009 - 09:34 AM

The 900QMD *does* have some upgrades available. These include the dec worm assembly (making it stronger and more accurate), the azimuth adjustment knobs, and a new fork to get better clearance for your hands under the mount. The altitude adjustment was also improved.

I hesitated for a long time between the MI-250 and a 900QMD. I also wanted NO go-to. What we're talking about here is two options that both place, in terms of capacity, over the Losmandy G11. Of the two, the AP900QMD will give you more load bearing and stability and the two mounts are probably appropriately priced. A used MI-250 without go-to SHOULD go for about the new value of a Losmandy G11 without go-to, and a 900QMD SHOULD go for a couple grand more than an MI-250. When I cruised a number of different mount groups for opinions about which was better for my designated load (c14 and refractor) the large majority suggested the 900QMD. Incidentally I posted the question not just on AP and MI-250 but several other upper-end mount goups because a lot of those people have experience with several mount types.

On the 900QMD the encoders can be upgraded to 10,000 tics. If you are using a narrow field telescope and need a lot of pointing accuracy you will want to review the modifications of the RA encoder shaft posted in the Argo Navis files section.

The AP900QMD is probably the "best direct competitor" against the current AP900GTO. A G11 well mounted on a permanent pier with the Ovision modification actually can carry a similar load at similar or better PE. The 900QMD breaks into two pieces and is a very light weight piece of equipment, save for the cw shaft and the counterweights. I don't usually break mine apart these days.

Probably the main hassle of a 900QMD is that the encoder cup has to be removed and the polar scope screwed in for polar alignment, and then you take the polar scope out and re-attach the encoder cup. This is inconvenient and leads to metal fatigue on the aluminum interface between the mount and the encoder cup, for which I posted a cure on the aforementioned argo navis group.

One does not hear a lot from 900QMD owners. The MI-250 community is more active. But if you hang out on equipment groups you just don't see a lot about 900QMDs. Like most of the stepper-era mounts, there isn't much that goes wrong with them.

Here's mine:

AP900QMD with C14 and refractor

I should mention that AP hemmed and hawed about whether an AP900QMD "could carry" a C14 and refractor. In their view an AP1200 is indicated. But the fact is that the C14/AP900 is one of the most stable on the field in terms of damping time, stability in wind, etc. I haven't tried photography with it but I think it would certainly work well in fastar configuration and would probably get me off to a good start on long fl imaging. Anyhow for long fl imaging it would be cheaper to get a 9.25 (sizing the scope to the mount) than to get a new mount! Nonetheless the 900QMD with a c14/refractor is an outstanding visual configuration, very portable, and MUCH easier to lug around than a Losmandy Titan.

You have to be careful about the upgrades in the QMD. My QMD had had zero upgrades and by the time I got everything done and bought the extra length counterweight shaft and the saddle plate and the ATS pier, my "$3.5k 900QMD" had cost me close to $7k. But if you price the contemporary AP mounts it is the same thing, they don't come wtih tripod, saddle plate, and you have to pay for counterweights, etc.

Nonetheless I'm very glad I have this piece of equipment. It meets/exceeds all my operational requirements.

Greg N
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#11 DeanS

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Posted 21 August 2009 - 09:53 AM

Here is a pic of a 900QMD with an extremly long reflector on it. Way too much moment arm for this mount but Rick imaged with it for several years before upgrading to the 1200QMD I mentioned in a previous post.

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#12 Bowmoreman

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Posted 21 August 2009 - 10:20 AM

I was with you on everything except for:

A used MI-250 without go-to SHOULD go for about the new value of a Losmandy G11 without go-to,...


I see no way in which the value of a non-goto MI-250 is not significantly higher than any G11, let alone a non-goto G11.

Those two mounts are in FAR different classes, load, and accuracy wise...

Unless you are suggesting that GoTo on MI-250 is alone worth $2500 - $3000 over non-goto? Can this be true? If so, then a non-goto MI-250 is the bargain of the century ($2400???).

You may be right, but I do wonder that so much incremental value is placed on GoTo to so "devalue" the MI-250s without that single feature.

The going rate for used MI-250's with GoTo is demonstrably between $5500 and $6500+ (depending on age, condition, ancillaries, etc.). I personally have fairly recent experience with that particular used market, and, have monitored others both before and since.

And the MI-250 will easily outperform ANY G11, with any load imaginable...

Now, as to AP900QMD, I offer NO perspectives whatsoever. ;)

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#13 DeanS

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Posted 21 August 2009 - 11:35 AM

If you look at the DEC head on the non-goto vs the goto, you will see a significant difference in them.

Goto has gear and worm in a housing, plus the motor.

Non goto has no gear or worm, and only a small cam that turns for guiding.

I do know some with the older non goto that do get good results. But like I said before, electronic parts are no longer available off the shelf.

Just my opinion of course :)

#14 gnowellsct

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Posted 21 August 2009 - 01:58 PM

I was with you on everything except for:

A used MI-250 without go-to SHOULD go for about the new value of a Losmandy G11 without go-to,...


I see no way in which the value of a non-goto MI-250 is not significantly higher than any G11, let alone a non-goto G11.

Those two mounts are in FAR different classes, load, and accuracy wise...

Unless you are suggesting that GoTo on MI-250 is alone worth $2500 - $3000 over non-goto? Can this be true? If so, then a non-goto MI-250 is the bargain of the century ($2400???).

You may be right, but I do wonder that so much incremental value is placed on GoTo to so "devalue" the MI-250s without that single feature.

The going rate for used MI-250's with GoTo is demonstrably between $5500 and $6500+ (depending on age, condition, ancillaries, etc.). I personally have fairly recent experience with that particular used market, and, have monitored others both before and since.

And the MI-250 will easily outperform ANY G11, with any load imaginable...

Now, as to AP900QMD, I offer NO perspectives whatsoever. ;)

clear enough skies



I'm not sure what the fuss is about. The I just said that a USED non-go-to MI-250 SHOULD be about the price of a NEW G11 which implies that the MI-250 is intrinsically better. I'm not sure I'd want it now that I know it doesn't have a dec worm, however. There are really two ways to consider G11 accuracy these days, with Ovision, and without. I usually factor Ovision in as an option in my considerations.


G11 with Ovision


With regard to load capacity all bets are off on a permanent pier. Rainer is running his at something like 80 lbs for astrophotography.

ANYHOW, I agree that the MI-250 is generally speaking a higher capacity mount. I looked at it very carefully and came close to getting one, but again, I didn't know about the Dec arrangement. But I'm glad I bought the 900QMD which seems to carry the C14+refractor about as well as the Losmandy Titan.

It's nice that the MI-250 has been so carefully re-engineered. I think Scott should do the same thing for the G11s--Ovision design should be incorporated.

I think that the old style push-to MI-250s are price depressed for a variety of reasons. For one, if you consider the full range of telescopes out there, a large number fall within the range of easily being carried by the G11 (and with high accuracy at $500 more--but the low MI-250 price predates Ovision). This usually comes with a tripod. I think the $2500 price for MI-250s is usually without a pier. For some reason most MI-250s seem to be used permanently mounted (just an impression, unclear as to why). In any case if you consider that a G11 with an excellent tripod new (no go to) is around $2300 and then say well a used MI-250 is $2500 but I have to put in another $800 to $1500 on a pier now we're looking at $3500 to $4k for a deployable MI-250 (less with a pier like AP's) versus $2300 for a deployable G11 NEW (no go to) vs $1800 for the same G11 used (typically).

So all that seems about right to me. And the MI-250 prices can't go too much higher because then they're competing against used AP900QMDs, which also price out around $3500 to $4500 depending on bells and whistels and also require some kind of tripod or pier as a general rule.

regards
Greg N


#15 gnowellsct

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Posted 21 August 2009 - 02:12 PM

How did you level the mount on that rocky surface wtiht he ap pier? Or did you bother?

Greg N

#16 DeanS

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Posted 21 August 2009 - 03:30 PM

He sits it on cement paver stones, eyeball level is good enough for what he does. Quick polar scope alignment and off he went.

This is what he got that night along the road waiting for the Winter STar Party gates to open the next morning. Was his best Saturn to date, and won the image contest that year.

Attached Files








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