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Advice please. Buying a new mount $2k. 4 Small Obs

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#1 LakeFX

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Posted 29 September 2012 - 07:03 PM

I've researched a lot of threads, and as has been the case for a long time, Its difficult and confusing to know which one is best in this price range. I'm hoping if I gave some specific parameters maybe the advice might steer me in an optimal direction.

For the longest time I've been set on the IEQ45, but the research I've done in the last couple of days has made me worry about that decision.

I have a small 8x12 RoR backyard observatory. Concrete pier. PC, full power.

*Primary* purpose is imaging. I use a modded and an un-modded DSLR today. T1i astro, T3i non-astro.

Current scopes are a Meade 8" SCT and a Celestron C80ED.


I estimate my imaging weight today will be in the neighborhood of 29 lbs, and in the future, no more than 31 lbs...given the scopes I plan to get..I'm being liberal with those numbers, I'm estimating high for these. That includes guiding equipment, adapters etc.

I'd like to shoot for a scope that can do ~ 1 arcsecond of error after PEC and guiding under the most ideal conditions....Or something that would show nice tight round stars at about 1300mm or less on my T1i after stacking and processing. I think this would be about right, or am I nuts? If you think I may need to adjust my requirements, I'm OK with that...Primarily need to stay under $2000 for the mount, and maximize what I can with that.

So given that I don't need to worry about tripod issues, dampening time, weight of the mount, set up time. Fancy polar alignment scopes and so on. My thoughts are that I can get away with a bit heavier imaging weight because of the observatory pier and walls to protect from wind, and the rest simply won't be issues. Whats the best bang for $2000?


Here are the ones I know about through research...CGEM DX, CGEM, IEQ45, Atlas EQG, Sphinx SXW

Also, is the G11 a possibility for an Obs with dedicated computer control, or is paying an extra grand for GOTO absolutely necessary evil?

#2 Ranger Tim

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Posted 30 September 2012 - 12:04 AM

Sphinx SXW is not an option for your weight class. Declination bounce defect also.

Why buy CGEM DX if you're pier mounted? CGEM would probably be same result.

Atlas is a known quantity and is least expensive.

IEQ45 is lightweight option but I have no personal exper. w/ it.

Losmandy requires Gemini for computer connection.

I would search for used Losmandy G-11 w/ Gemini 1, they are available often. Atlas would be my second choice. YMMV

#3 orlyandico

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Posted 30 September 2012 - 01:05 AM

Used CGE.

1" after guiding seems a bit ambitious. That's below the seeing limit in most areas. But I think the Atlas/ Cgem/iEQ45 would have some challenges consistently hitting 1".

#4 LakeFX

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Posted 30 September 2012 - 07:06 AM

1" IS probably ambitious, however most of the complaints with these mounts in this class is with attempting to get them to hit that level of resolution. If theres too much error after PEC that guiding might be impossible or not good enough etc. So MAYBE it doesn't need to be this good. My current mount is terrible so any improvement will probably be quite large.

CGEM DX = CGEM Pier mounted? Is the only major difference the tripod?

The Atlas just doesn't seem like it should be better than the likes of the CGEM or the iOptron. But seeing as how its been around forever....perhaps why its the most trusted.

#5 Raginar

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Posted 30 September 2012 - 07:46 AM

I don't think you're going to be happy with any of those mounts if you're trying to get a guided/pec performs of ~1". Especially the lower end models. You'll find threads on here from people trying to exactly the same thing without getting good results. Even a G11 probably won't meet your needs. My suggestion? Wait. Save up enough to get a great mount instead of buying one that is sub-par and slowly working your way up. Especially since you've decided you need ~1" accuracy.

If you do want to try one of these lower end mounts; buy used on AM so your hit is less. AIm for a hyper tuned model so it's 'max performed' when you receive it.

Good luck!

#6 orlyandico

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Posted 30 September 2012 - 08:32 AM

Well the CGEM has a non integral gear harmonic that can't be corrected by PEC. It is slow moving though (182s period) but large - 22" on mine - so can corrected by guiding. The iEQ45 - at least one poster here - has a fast 6.2s 5" harmonic that cannot be guided out.

The Atlas has the least complex gearing of these mounts, so my theory is it would have the least gear harmonics.

I can tell you though that I think the least expensive mount that can do 1" is a used Takahashi EM200. A non GoTo one went for $1.6k last week but I got beaten to it.

#7 Cotts

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Posted 30 September 2012 - 09:31 AM

For under $2k a used G11 would be good, combined with an autoguider like the Orion Starshoot. You don't need Gemini for anything to do with guiding. The autoguider plugs into the Losmandy drive control box.

1" error would make a Paramount owner drool but an autoguider will get you close.

Dave

#8 BKBrown

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Posted 30 September 2012 - 09:53 AM

If you are guiding, why are you concerned about getting ~ 1" PEC? I would be shooting for a mount that guided out errors smoothly, certainly the Atlas and CGEM can deliver good results. That said, I'm an Atlas guy enjoying robust, trouble free guiding and a decent load capacity on my pier...

Clear Skies,
Brian

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#9 orlyandico

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Posted 30 September 2012 - 09:54 AM

I rented time on a Paramount... with a short refractor on it (FSQ-106) I could only manage about 3" stars - but that's due to the refractor, according to Frank (freestar8n).

I know that Paramounts and any modern AP mount can get below 1" after PEC, so not so much drooling there.

The problem with the China mounts in the $1500 class is that the gearbox produces a lot of noise that can't be guided because it's fast. I really don't know how the Paramounts and AP's of the world manage it. Those Swiss Maxon motor gearboxes must be made of unobtanium or something...

That said a G11, particularly with the Ovision worm and Maxon motors (hence it would have to be a Gemini G11, since the 492 Digital Drive uses steppers and not the Swiss Maxons) would probably get close.

Still I think imposing a 1" requirement automatically puts the mount in AP Mach1 or EM200 class at least.

But if I were to choose a new, $1500 mount, it would be the Atlas.

I've seen the gearbox on that thing - it's 2 gears with an idler. And you can upgrade the idler with a flange bearing to make it smoother. The simpler it is, the less can go wrong with it.

You might even want to buy an Aeroquest worm for it (fairly cheap). My CGEM had a fundamental of 29" and the non-integral 8/3 of 22". After putting an Aeroquest worm in, I got the fundamental down to 16" (half!) but the 8/3 remained the same at 22".

So not much help there. But with an Atlas and its simple gearbox with small-amplitude fast noise, an Aeroquest would be a big improvement and for a pretty low price.

#10 Nezar H

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Posted 30 September 2012 - 10:18 AM

What about used Vixen Atlux ! I have one but I use it mostly for visual use
with the Star Book Computer! (not every one like it- but I do) or with the old SkySensor2000 PC , or upgrad to NexStar!.
http://www.iceinspac...37-0-0-1-0.html

#11 LakeFX

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Posted 30 September 2012 - 12:16 PM

Alright just to clarify 1" is not MY standard...it just appears to be THE standard (Or goal) based on what I see around here. I'm being told from all over this board that 1 arc second is ideal for most situations, and really the way to get there is by staying under weight, having a good guiding setup, and eliminating external factors like tripods, wind, flexure, etc.

If a paramount or Mach1 etc can't do that, well, then the discussion is DoA! So maybe the problem is that 1" isn't necessary and shouldn't be the discussion then.

Here's the math--Someone stop me if this is wrongheaded... Suppose I'm imaging at 1300mm, And I'm using a 16 or 18 megapixel APS-C sized chip. That means a pixel will cover .7" to.75" arcsecs. or 1.5" with binning. If an average sky for my area is 2 arc seconds..Then In Theory, If guiding error is down to 1 arc sec, I've got as good an image as I'm going to ever get for my site.

As for imaging weight, I don't see myself exceeding 30 lbs. In my view, any OTA and accessories big enough to exceed that is going to exceed seeing conditions 9 times out of 10 and so then having diminished returns on size vs focal length. With the mount, if I'm getting a bigger, beefier, and more accurate mount, and not getting results better than 2 arc seconds...same thing, diminished returns. What I mean is, if a $2000 mount guided can produce < 2" results, and much more expensive and accurate mount, also guided can produce < 2" results...Then whats the point other than more weight capacity? Perhaps less frustration--maybe, but not necessarily less equipment either. Now if there are specific problems....and I'll review these:

The Atlas is simpler...so less harmonic problems. Makes sense, more error is removed via PEC in theory. IEq45 and CGEM have more harmonic error that can't be removed with PEC, makes sense. CGEM DX is not really any different under my particular circumstances. An unlucky few seem to have *unfixable* harmonic error on CGEM and IEq45...that's what scares me. The last thing I want to do is drop all of this money on a bigger mount and more imaging equipment in order to get something that performs only slightly better than my LXD55!

I do apparently need GoTo, I remotely control my observatory from the house, again something LXD55 accommodates and something I don't want to lose BY spending a crapton of money! Unless there's some sort of magic I'm missing out on here that I don't understand, a non GoTo mount simply won't suffice.

I like the logic of saving up for and getting a more expensive mount. It works with a lot of things. But that's not been doing me much good so far. I saved up for a $600 mount, it stunk. So i start saving up for an $800 mount...it just wasn't good enough for the weight I might put on it since rated weight and imaging weight are different...So then I saved up for a $1300 mount...but Now there's a new one on the market for $1600 that's better. Built an observatory instead. Now a $2000 one....save up for the $2000 one and it's not any better than the $1300 mount--which isn't good enough, so save up for a $3000 or $6000 mount!

I think for today, given I'm 31, house poor and saving money is slow...Perhaps I'm overthinking this...I should have an Atlas already and be using it and learning more.

#12 LakeFX

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Posted 30 September 2012 - 12:26 PM

If you are guiding, why are you concerned about getting ~ 1" PEC?


Exactly. I think you misread my post but what you said brings up a valid point. When you hear horror stories like unfixable harmonic error and massive amounts of DEC backlash, you get gunshy! The issue isn't 1" PEC, its 1" guiding. I suppose a mount in theory with 30" of PE, could be reduced to 20" with PEC and then guided out to 1". What's confusing is a more accurate mount, like the IEq45...could theoretically have 15" of PE, 10" after PEC, and 4 after guiding due to fast harmonic error. I guess that's why this decision is so tough. But I did get an answer...The Atlas may be more reliable against harmonic errors that might not be guided out. Unless someone can refute that.

#13 Midnight Dan

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Posted 30 September 2012 - 12:34 PM

I saved up for a $600 mount, it stunk. So i start saving up for an $800 mount...it just wasn't good enough for the weight I might put on it since rated weight and imaging weight are different...So then I saved up for a $1300 mount...but Now there's a new one on the market for $1600 that's better. Built an observatory instead. Now a $2000 one....save up for the $2000 one and it's not any better than the $1300 mount--which isn't good enough, so save up for a $3000 or $6000 mount!


In general, the entry level for a "reasonable" AP mount is around $1100-$1300. But even in the $1100-$2000 range, the mounts you'll find are mass produced and roughly similar in quality, just differences in features and weight capacity. While these are not the top quality mounts, they are priced within the reach of mere mortals and provide an adequate quality level for many imagers.

If you want something that does a really top quality job of tracking with low PE and good weight capacity, you're in the $3000-$5000 range and up. That's just the way the economics works. It costs a lot to reach the tolerances needed.

Perhaps I'm overthinking this...I should have an Atlas already and be using it and learning more.


Now THAT sounds sensible. Tons of happy astrophotographers out there using the Atlas. Although, I'm not sure why you've written off the iEQ45. Lots of happy users there too.

-Dan

#14 orlyandico

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Posted 30 September 2012 - 12:43 PM

Frank (freestar8n) will say that most every error can be guided out if you're aggressive enough in your guiding, and your mount is "decent-ish" enough.

By decent-ish he means the CGE or CGE Pro.

Now there are many pretty images on his site with < 1" FWHM stars, taken with long heavy scopes (C11, C14) with CGE and CGE Pro mounts, with his guiding software - Metaguide.

Note that he also advocates the use of off-axis guiding. I am not an advanced imager by any means but I can say, with a not-flawless mount, OAG does give tighter stars than a normal guide scope.

That PME I rented.. well it was using an ST-i (100mm focal length guider) which is tiny.. but the errors were tiny too, and it only needed correction every 10 seconds or so.

With the biggish errors of the not-flawless mounts, aggressive guiding would help. However something like the 6.2second 5" iEQ45 error.. I don't think you can guide that out...

Let me share my own mount odyssey.. started with a Vixen GP, with 80" peak error. Suffice it to say I did not get very many astro photos with that mount.

Moved to a CGEM. Am still taming it after runaway slew problems. Replaced the RA worm with an Aeroquest. Did a DIY hypertune. Replaced the RA worm bearings as well with Japanese ones. The fundamental error is now a respectable +/- 8" but the 8/3 is still at 22" - so total PE is around 40" and PEC would only reduce that to 25" range.

Not fatal - still guidable since the 8/3 has a 182s period. But there also are other fast errors in the hideous gearbox.

I suspect a similar situation with the iEQ45. Servos need large gear reduction (about 50:1) which requires a complex geartrain. When the entire motor and gearhead costs $20 - you get the idea. FYI the CGE and CGE Pro use $100 motors - one would expect better gears in those things.. but still not Maxon class.

After playing with the CGEM for a year, I chanced upon a used - non-GoTo - AP600 mount for $2k. Dazzled by the prospect of owning one of Uncle Rollo's fabled creations, I jumped on it. I can say this - the fundamental of the worm is tiny - 9" peak to peak.

It didn't have GoTo. I spent a goodly sum converting it to GoTo. Since it is stepper-based, I found some Vexta gearhead steppers to run it (the original motors wouldn't do). Guess what - these $220 Vexta steppers have about 4" of gear noise. So even with a good PEC run, I can't get the remaining PE below about 4".

Is the AP600 perfect? no. It was designed in 1988. Uncle Rollo's standards have come up since then.

But if you add up all the costs I've incurred with my parade of mounts, I could have bought a used Mach1.

Granted a Mach1 would require a large cash out, whereas I spread my mount costs over several years (and frankly, had fun with DIY hypertuning and bearing replacement and obsessively measuring PE).

So.

Get the Atlas and start imaging. Accept that at 1300mm FL you will have some (or many) thrown away subs. So use the 80ED and enjoy perfect stars every time.

OR... do not buy anything until you can afford that Mach1. Or at least a used EM200 Temma (about $4K). In the long run, buying the best is cheaper. But it sucks to be sitting on your couch with nothing until you can afford the best...

#15 orlyandico

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Posted 30 September 2012 - 12:51 PM

Post deleted by orlyandico

#16 orlyandico

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Posted 30 September 2012 - 01:05 PM

LakeFx, I had a look at your gallery. Your M31 is much better than anything I could ever cough up. Amazing for 25-second sub-exposures.

From my extremely light-polluted balcony, I do 10- to 20-minute guided subs with the AP600. And my results are nowhere close to what you're getting.

I think if you could produce these results from an LXD55, you must have the patience of a saint. So go get that Atlas already. Get a used one. Measure the periodic error. If it's more than 20" peak-to-peak, buy an Aeroquest worm (about $100) for it.

#17 LakeFX

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Posted 30 September 2012 - 01:24 PM

I think if you could produce these results from an LXD55, you must have the patience of a saint.


AMIRITE?

Seriously, thank you, I really appreciate that.

The crazy thing is, now I can get 60 second subs on the C80ED without guiding after perfecting the LXD55. I throw out about 1/3rd of the subs of course. Its surprising what that old clunker can do when put on a pier and given waaaay more attention than it deserves.

Oh and I caught that other post before you deleted it..I was on it already and asked questions, unfortunately it just doesn't seem like I'd be doing nearly as well without GOTO. I have 'yellow' zone skies which makes find most targets difficult without a lot of trial and error and wasted integration time.

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#18 orlyandico

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Posted 30 September 2012 - 06:57 PM

Wow. Throwing away 1/3 of the subs at 60 seconds... that sucks. A downside of longer subs is that it hurts more to throw them away.

I think the Atlas is the safest bet. But buy used. This will leave more funds for things like a better saddle (ADM) and optionally that Aero quest worm and 608ZZ bearings.

#19 EFT

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Posted 01 October 2012 - 10:41 PM

The Atlas is simpler...so less harmonic problems. Makes sense, more error is removed via PEC in theory. IEq45 and CGEM have more harmonic error that can't be removed with PEC, makes sense. CGEM DX is not really any different under my particular circumstances. An unlucky few seem to have *unfixable* harmonic error on CGEM and IEq45...that's what scares me. The last thing I want to do is drop all of this money on a bigger mount and more imaging equipment in order to get something that performs only slightly better than my LXD55!


Keep in mind what has been said about the CGEM 8/3 harmonic. It is not the end of the world. It just can't be eliminated by the built-in PEC. It is not however so bad that it cannot be guided out or possibility addressed in an outside program. That is a lot different than a harmonic error that simply cannot be eliminated or guided out due to its speed and magnitude.

Also keep in mind that, while the Atlas is simpler, its hand controller is also simpler and there were a variety of improvements made to the CGEM in comparison to the Atlas. In the case of a permanent installation, the biggest improvement to the CGEM over the Atlas is the counterwieght bar which is far more solid and sturdy. The same goes for the CGEM DX. It would be nice if they would revamp the Atlas/EQ6 to include some of the same improvements but then it would probably outsell the CGEM if they did. The difference in the hand controllers would be moot if you are planning remote operation using EQMOD on the Atlas.

#20 EFT

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Posted 01 October 2012 - 10:45 PM

I spread my mount costs over several years (and frankly, had fun with DIY hypertuning and bearing replacement and obsessively measuring PE).



One of the best things about tuning a mount yourself, regardless of how you go about it, is that you learn a lot about how these things work and that gives you a better understanding of the advantages and disadvantages of different designs as well as a better idea of what might be happening when things go wrong. Experience and information that is good to have even when you move up to more sophisticated and expensive mounts that are also not infallible.

#21 LakeFX

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Posted 02 October 2012 - 08:28 AM

Good news...A new mount on the way! A Hypertuned CGEM. Thanks for all your help everyone. I cleaned up a lot of confusion with this thread and definitely helped steer me in the right direction.

When it comes down to it, the CGEM strikes a good balance of quality, evolution of its software, cost, known-repeatable-fixable problems. Big(ger) community of support.

Thanks for the advice everyone!

#22 LakeFX

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Posted 21 October 2012 - 10:42 PM

Quick update.... After the mandatory 11 day waiting period of rain, clouds, dreerienes and apologizing to family for bring such horrible weather by buying new equipment...I've pier mounted, accurately polar aligned, and PEMPro PEC tuned the mount.

After all is said an done I'm down to just shy of 11 arc-seconds peak-peak of periodic error before guiding without any visually fast movements in RA.

I had been using an LDX55 for 10 years now as of this month and I've got to tell you, everything is four times as easy, 4 times more accurate, and all around this CGEM mount just gives me the warm fuzzies. Perhaps I'm more easily amused simply by fighting the 55 for so long.

I'll be purchasing a VSBS and start some guiding here shortly.

#23 EFT

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Posted 21 October 2012 - 10:56 PM

Quick update.... After the mandatory 11 day waiting period of rain, clouds, dreerienes and apologizing to family for bring such horrible weather by buying new equipment...I've pier mounted, accurately polar aligned, and PEMPro PEC tuned the mount.

After all is said an done I'm down to just shy of 11 arc-seconds peak-peak of periodic error before guiding without any visually fast movements in RA.

I had been using an LDX55 for 10 years now as of this month and I've got to tell you, everything is four times as easy, 4 times more accurate, and all around this CGEM mount just gives me the warm fuzzies. Perhaps I'm more easily amused simply by fighting the 55 for so long.

I'll be purchasing a VSBS and start some guiding here shortly.


It's always a joy to go from an old, limited, fairly difficult mount to a new, up-to-date mount with more capacity as well as bells and whistles. Enjoy the new mount, you made a good choice.

#24 Raginar

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Posted 22 October 2012 - 10:43 AM

LakeFX,

You're doing better with my mount than I was! :) I'm glad it's serving you well.

Can't wait to see some pictures.






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