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Author Topic: Astro-Physics 1200GTO  (Read 7800 times)

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Offline Ben Ritchie

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Astro-Physics 1200GTO
« on: 09:23:21, 11 June, 2008 »
As there's a call for mount reviews, here's the first of three on mounts i've owned recently...

Weighing in at 95lbs without counterweights, and with an instrument capacity of 140lbs, periodic error guaranteed to be under 5 arcseconds peak-to-peak before correction and a price tag that would buy a new Citroen C1, the Astro-Physics 1200GTO is rivaled only by the Paramount ME as the 'ultimate' amateur mount. I had a 'love it and hate it' experience with my Losmandy G11, and when the chance came for a mount upgrade I looked at a number of options. The Losmandy HGM Titan, Takahashi NJP and Mountain Instruments MI250 were all strong contenders, offering improvements in quality, capacity and accuracy over the G11, while the Astro-Physics 900GTO has the quality of the 1200GTO in a smaller, slightly cheaper package. The MI250 was particularly attractive; the company has a great reputation for quality and customer service, and the mount was significantly cheaper than the Astro-Physics mounts. But I'm looking long-term with this purchase - the mount should give me a decade or two of trouble-free service - and, in the end, decided to go with the best. The Paramount was just too expensive in the UK and, rarely, the 1200GTO was available without a long waiting list, so I gave Astro-Physics a call and paid my 50% deposit.

The expense doesn't end with the mount; that comes with almost nothing in the way of the accessories required to use it. I also ordered Astro-Physics' Losmandy-style dovetail for the 1200GTO, a pier adapter, smaller (14" x 1.875" diameter) Counterweight Shaft and two 18lb stainless steel counterweights for the mount. Together those added another $748 to the bill. Ouch! After that there was nothing to do but wait.

The mount arrived about six weeks later, in five large boxes weighing in at a total of 168.5 pounds. Nothing can really prepare you for the first sight of a mount like this - it is massive, making my G11 look like a toy in comparison. The quality of the contents is amazing. Everything is superbly machined and put together, and no expense has been spared on the componentry. All together it's an engineering masterpiece, with superb attention to detail. The hand controller deserves special mention; very rugged, with a big, clear four-line display and great feedback from the keys. Very different from the G11's "1980s" controller. The mount also came setup for my home location of 51N; a nice touch.

Getting the mount setup in the observatory was straightforward, and, although I followed the instructions to the letter, it was obvious how everything fitted together. None of the pieces were impossibly heavy so this could be a portable mount, although it's better suited to a permanent home. Although it's impressively large, it doesn't occupy too much space and there's plenty of room left in the observatory.

Under the stars the the performance of the mount is just wonderful. The handset is superb, and mount slews are impressive - the mount heads off at high speed, and just when it seems sure to overshoot, coasts briefly before stopping dead. The settle time after a slew seemed virtually zero. Integration with TheSky 6 worked very well, with none of the quirks that I saw with G11/Gemini - with the 1200GTO the mount ends up where you clicked, rather than 'somewhere close'. Goto performance relies on your mount being well polar aligned with no OTA non-orthogonality; after Gemini, which compensates for both, this is a little primitive. Polar alignment is simple, with the mount adjustment being very smooth and backlash-free. I haven't bothered fixing the slight non-orthogonality in my system, and although this causes long slews to leave the target slightly off-centre it's easy to just plate solve and resync in CCDSoft/TheSky. If I was using very long focal lengths or small fields of view i'd look at adding T-point to improve goto performance, but it's not necessary for my setup.

Astro-Physics test the mounts extensively and pre-program the mount with periodic error correction information derived from their testing. Downloading this into PEMPro showed that the PE was 4.05 arcseconds peak-to-peak, although I haven't measured this to confirm. With periodic error correction turned on, an hour of PEMPro data showed the remaining periodic error to be 0.4" peak-to-peak, with total errors (periodic and aperiodic) of under an arcsecond. This means the mounts tracking is limited only by its polar alignment, and I routinely image for up to five minutes unguided at 1.2"/pixel with pinpoint stars. It's an absolutely staggering level of performance. In fact the level of performance is so consistently high that it's hard to review; at every image scale i've tried the mount is flawless. Tracking is so good that it's quite easy to make it worse with careless autoguider calibration, as over-aggressive correction or rapid exposures that 'chase the seeing' can cause fatter stars than unguided exposures. Generally I use guide corrections of up to 30s, and only to control slow drift from polar misalignment etc.

My general routine with the mount is to wake it from 'park 2', slew to a bright star, take an image with the CCD, plate solve in TheSky and sync on the calculated position. Usually it's very slightly out (a few arcminutes), but synchronizing only takes a moment and after that GOTO is spot-on; the pointing accuracy and repeatability is unbelievable, which makes multi-night imaging runs very simple indeed - I typically find that sets of images from more than one night are shifted by no more than a couple of pixels (at a 1.5"/pixel image scale). Once started up, the mount effectively 'disappears' - it just works perfectly, night after night.

All in all I regard the 1200GTO as probably the best money i've ever spent in Astronomy. Ok, it's expensive - very expensive - although, to put it in perspective, the cost is equal to a couple of years depreciation on a new car, and for your money you get a mount that's built to work at a very high level for a couple of decades and can be sold for a good price if you do need the money back again. The mount is a bit large to really be considered portable, although it wouldn't be too hard to move about, but for mobile use the 900GTO or Takahashi NJP (with its superb polar alignment 'scope) would be a better choice. However for observatory use it's just superb.

[attachment deleted by admin]
Astro-Physics 130EDT StarFire, Borg 77EDII, way modified 80ED, VLT
Astro-Physics 1200GTO, 'evolved' HEQ5/pro
Coronado SM60/BF10, 3-6 Nagler zoom, 8 & 13 Ethos
...and a box full of bits

Offline mkp

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Re: Astro-Physics 1200GTO
« Reply #1 on: 14:00:11, 11 June, 2008 »
Good review, and I second it. Also had a G11 beforehand, the ap1200 makes imaging a joy. Also, I don‘t have an observatory setup. The 1200 is big, but it easily dismantles into two component parts which I put up and take down each imaging session. A great mount.

Malcolm

Offline Solar B

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Re: Astro-Physics 1200GTO
« Reply #2 on: 22:28:56, 11 June, 2008 »
Thats an excellent review Ben  :yes: of a serious piece of kit.
One question...is it quite hard on batteries  :clown:
                                                          Brian   

Offline MartinB

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Re: Astro-Physics 1200GTO
« Reply #3 on: 07:56:11, 12 June, 2008 »
Great review Ben.  That sounds like the dogs danglies although no surprise really.  I have read people suggesting that the AP1200 is a better package than the ME for non robotic use
Martin

10"LX200R, ED120, ED80, ZS66, Tak EM200,  SXVH9 and SXV guidehead

Lots of bits

Offline Ben Ritchie

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Re: Astro-Physics 1200GTO
« Reply #4 on: 08:30:39, 12 June, 2008 »
Thanks guys.

It's hard to compare the 1200GTO and ME, because they really come from very different backgrounds - the 1200GTO is a very well made classic GEM, whereas the ME is a computer-driven technological wonder. For field use the 1200GTO is going to be much easier, quick to assemble and polar align and can be easily run from the hand controller and 12V battery with no need for a computer. OTOH, for highly automated use - e.g. automated surveys - the ME is going to beat out the 1200GTO (although some of that is down to the Bisque software suite, which can also drive the 1200GTO. If you run the 1200GTO from TheSky with a 120-point T-point model then GOTO's pretty darn good on that too). In between there's typical observatory use, where both are near as anything perfect.

When I costed it all out an imported 1200GTO was a fair bit cheaper than a UK-sourced ME (Bisque won't ship to Europe from the states, you have to go through the dealer network with associated mark-up) so as I don't need the high-automation capability of the ME it was a pretty easy choice to make in the end.
Astro-Physics 130EDT StarFire, Borg 77EDII, way modified 80ED, VLT
Astro-Physics 1200GTO, 'evolved' HEQ5/pro
Coronado SM60/BF10, 3-6 Nagler zoom, 8 & 13 Ethos
...and a box full of bits

Offline the fordster

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Re: Astro-Physics 1200GTO
« Reply #5 on: 10:54:47, 12 June, 2008 »
That's a brilliant review, Ben!

One thing I do wonder (maybe a bit naively) is how much *more* you get in terms of accuracy over something like the G-11.

I mean, if you think about our seeing as limiting the resolution you can image at, if a mount can work up to that limit, what do the extra pounds get you?

Offline Ben Ritchie

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Re: Astro-Physics 1200GTO
« Reply #6 on: 14:02:24, 12 June, 2008 »
Quote
One thing I do wonder (maybe a bit naively) is how much *more* you get in terms of accuracy over something like the G-11.

How much more's an interesting question, and not an easy one to answer. Once i'd sorted it out, my G11 tracked almost as well as an AP900 and autoguided perfectly at 1000mm focal length, so the data i'm getting with the 1200GTO is not significantly better than that. Of course, it was a huge amount of work to get there, and at 2000mm focal length that's certainly no longer true, of course. Something like a VC200L would be much easier with the 1200GTO (I could still use 10s guide exposures at that FL), but 2000mm focal length's quite seeing-limited in this country. So on one level, the answer's "not much" as I usually image at around 1000mm FL, a length that the G11 could comfortably cope with.

You also gain a lot of capacity - the G11 couldn't cope with the load that I have on the AP1200 - but that's a side issue if you're happy to swap 'scopes over. I'm observatory mounted so going three-up's a convenience, but not one that's worth the £££ on its own.

For me, the biggest benefit from moving from the G11 to the AP1200 is that the mount becomes a non-issue, it 'just works' so well that I never think about it. Tracking and pointing are near as anything perfect, so you can concentrate on other things. With the G11 that was never the case - i'd always be having to tweak the pointing by hand (GOTO from TheSky was 'close', not 'bang on', I never did understand why), PE was occasionally problematic and limited guide exposures to a couple of seconds, things like that. So it's had a huge impact on my enjoyment of the hobby, night after night was spent on the G11 trying to get it to perform well and that was bloody frustrating at times (as for my HEQ5, i'd have thrown it in the sea by now...). As time goes on i'd hope it has an impact on my results too - i'm still trying to nail down data acquisition and my processing sucks so I have a long way to go. Slowly getting better though ;)
Astro-Physics 130EDT StarFire, Borg 77EDII, way modified 80ED, VLT
Astro-Physics 1200GTO, 'evolved' HEQ5/pro
Coronado SM60/BF10, 3-6 Nagler zoom, 8 & 13 Ethos
...and a box full of bits

Offline roundycat

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Re: Astro-Physics 1200GTO
« Reply #7 on: 12:52:56, 19 June, 2008 »
Good review Ben. For what it's worth I agree with it all as I travelled the same route from G11 to AP. My 1200's PE is ridiculously small and the extra weight capacity is well worth the money. I use an old TMB 152 and 100 Tak, something the G11 could not cope with. The TMB alone at 1200mm is quite a handful but the 1200 hardly seems to notice. One night the wiring became snagged and the mount found itself lifting a 12v battery hanging on the end of the scope. I swear it didn't slow down at all!

Dennis

 

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