Author Topic: Upgrade Atlas EQ-G to Losmandy GM811G?  (Read 1219 times)

tissuppgunre

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Upgrade Atlas EQ-G to Losmandy GM811G?
« on: December 30, 2017, 07:42:21 AM »
OK, I need help trying to figure out whether the desire to upgrade my mount is for a noticeable improvement in AP tracking or if I just want a shiny new toy. Like many on these forums, I have a weakness for well crafted machines, and Losmandy is certainly a step up from Chinese cast mounts. At the moment, despite my desire, a true premium mount is not in the budget.

The question of upgrading is entirely a question of improving tracking and consistency for AP. I do almost no visual. My current Atlas guides fairly well, typically giving a total rms of 0.9 arcsec. on a night of average seeing. With very good seeing, it might get down to 0.7 rms and with poor seeing it's around 1.1 rms. These numbers are for guiding at an altitude of 50 degrees or higher. Much below that things get worse. Also, I use an Orion 80mm guide scope with a ZWO ASI120MM guide camera. I image with an ES ED127 at 952mm and Canon 5DII for a scale of about 1.4 arcsec/pixel. I may in the future change OTAs and cameras for an imaging scale of 0.7 arcsec/pixel, making things more demanding. So when everything is working correctly and skies are favorable, I get nice round stars. But... the mount is inconsistent. Occasionally, the PHD graph will spike and I'll get star trails or double stars. This may be due to backlash, stiction somewhere in the mechanical train, or susceptibility to mild wind. Not really sure the reason, but I lose some subs that way. Also, since I like to sleep and not babysit the mount all night, a few clouds drifting through can make the PHD lose its guide star and ruin the rest of the session. In all, I estimate I lose about 20%-30% of my subs due to either mount or guiding errors.

The question is simple. Would a Losmandy GM811G significantly improve tracking and consistency over my current mount to justify the upgrade. What kind of total rms are people getting with the G11 (same RA as the G811)? Can a Losmandy go unguided for several 5 minute subs so that when clouds pass, the guide star is still in the field of view? And is the machining as pretty as they say?



Clyde Duke

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #1 on: January 08, 2018, 04:39:38 PM »
No it would not.

You are not "tracking limited" at all. You're tracking is way under the ceiling. I recently went to using a scope remotely where the nights are clear and dark most of the time. It's been a revelation to me that when my guiding falls off - bad seeing, low altitude, the subs really don't suffer very much at all from tracking error. The stars are just as round, just a bit larger due to the seeing and the low altitude. I can see as the object gets higher in the sky that the stars get tighter and tighter all else being equal. So, it you can keep both axes well under 1 arc second, I'm not sure what you would gain.

My limited understanding of the math is that the guiding error adds only in quadrature so .7 means maybe .49 arc seconds of "bloat". Get that down to .5 (say) and you've gotten maybe .2 arc seconds better. If I have this wrong, someone should school me PLEASE.

Then there's the matter of the spatial resolution of your Canon. You've got 6 micron pixels so that you are way under-sampled and your spatial resolution is nowhere near optimal for your scope.

At the same time, the Losmandy mounts last forever. If your Atlas broke then it would be an interesting discussion.

Rgrds-Ross

ovisimmus

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #2 on: January 10, 2018, 10:14:09 PM »
Seeing can make you think your guiding is off, when its not. can drive a person nuts!

Eric Curry

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #3 on: January 11, 2018, 11:42:21 AM »
Quote
No it would not.

You are not "tracking limited" at all. You're tracking is way under the ceiling. I recently went to using a scope remotely where the nights are clear and dark most of the time. It's been a revelation to me that when my guiding falls off - bad seeing, low altitude, the subs really don't suffer very much at all from tracking error. The stars are just as round, just a bit larger due to the seeing and the low altitude. I can see as the object gets higher in the sky that the stars get tighter and tighter all else being equal. So, it you can keep both axes well under 1 arc second, I'm not sure what you would gain.

My limited understanding of the math is that the guiding error adds only in quadrature so .7 means maybe .49 arc seconds of "bloat". Get that down to .5 (say) and you've gotten maybe .2 arc seconds better. If I have this wrong, someone should school me PLEASE.

Then there's the matter of the spatial resolution of your Canon. You've got 6 micron pixels so that you are way under-sampled and your spatial resolution is nowhere near optimal for your scope.

At the same time, the Losmandy mounts last forever. If your Atlas broke then it would be an interesting discussion.

Rgrds-Ross

I'm a +1 with Ross, totally agree there isn't a current need to upgrade. If your current mount is on it's last legs then it's time to look at the Losmandy or if you are looking for a "forever" mount then it's an excellent option.

birchzufhyro

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #4 on: January 12, 2018, 12:13:04 AM »
Don't fall into the trap of chasing RMS error levels just to be chasing them. If you have round stars, you are good. I replaced my EQ-6 with a GM811, but not because I expected better guiding, but because the mount is light and easier to handle and has a MUCH better HC and goto system/accuracy.

turtnaneade

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #5 on: January 12, 2018, 10:44:36 AM »
Klaus,

See also my recent topic regarding exactly the same subject here.

My situation is a little bit different as I'm imaging at the 0.78"/px image scale. On that other thread the consensus mostly was that upgrading to GM811G or G11 will not significantly improve your guiding, which was very disappointing to me as I considered buying one of those mounts to upgrade my NEQ6.

Uncle Rod,
Our goal as imagers is not only nice round stars - I can get them almost all the time, our ultimate goal is to get small FWHMs in addition, to improve resolution in our images. This is much harder to obtain.

labulichar

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #6 on: January 13, 2018, 09:21:26 AM »
Quote
Klaus,

See also my recent topic regarding exactly the same subject here.

My situation is a little bit different as I'm imaging at the 0.78"/px image scale. On that other thread the consensus mostly was that upgrading to GM811G or G11 will not significantly improve your guiding, which was very disappointing to me as I considered buying one of those mounts to upgrade my NEQ6.

Uncle Rod,
Our goal as imagers is not only nice round stars - I can get them almost all the time, our ultimate goal is to get small FWHMs in addition, to improve resolution in our images. This is much harder to obtain.

So is there a mount that comes with excellent Seeing?;-) Just.... kidding.

I upgraded to the G11GT. Just the increased stability in focusing my F8 5 inch triplet was enough to make me feel justified in the purchase(granted the bar there is pretty low and I did not need much convinving  ). Still, if you have the EQ6 tuned so you are getting results described by the OP, then I can understand how the incentive upgrade would be reduced. I agree with Uncle Rod that the hand controller is a big step up from synta, and the Alt and Az adjustments are just like butter!! Anyone with an older EQ6 will appreciate it. I was dialing in my Alt using polemaster and turning the big adjustment knob with thumb and forefinger like I was focusing. Try that with an Atlas! However, these are all amenities, not necessities and I can certainly understand why one might consider the price tag too steep just for them alone.

JMD

Davione Boone

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #7 on: January 14, 2018, 07:10:53 AM »
Quote
Klaus,

See also my recent topic regarding exactly the same subject here.

My situation is a little bit different as I'm imaging at the 0.78"/px image scale. On that other thread the consensus mostly was that upgrading to GM811G or G11 will not significantly improve your guiding, which was very disappointing to me as I considered buying one of those mounts to upgrade my NEQ6.

Uncle Rod,
Our goal as imagers is not only nice round stars - I can get them almost all the time, our ultimate goal is to get small FWHMs in addition, to improve resolution in our images. This is much harder to obtain.


I know what the goal of astrophotographers is.

acoplochop

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #8 on: January 18, 2018, 11:26:52 AM »
Quote
Quote

Klaus,

See also my recent topic regarding exactly the same subject here.

My situation is a little bit different as I'm imaging at the 0.78"/px image scale. On that other thread the consensus mostly was that upgrading to GM811G or G11 will not significantly improve your guiding, which was very disappointing to me as I considered buying one of those mounts to upgrade my NEQ6.

Uncle Rod,
Our goal as imagers is not only nice round stars - I can get them almost all the time, our ultimate goal is to get small FWHMs in addition, to improve resolution in our images. This is much harder to obtain.

So is there a mount that comes with excellent Seeing?;-) Just.... kidding.

I upgraded to the G11GT. Just the increased stability in focusing my F8 5 inch triplet was enough to make me feel justified in the purchase(granted the bar there is pretty low and I did not need much convinving  ). Still, if you have the EQ6 tuned so you are getting results described by the OP, then I can understand how the incentive upgrade would be reduced. I agree with Uncle Rod that the hand controller is a big step up from synta, and the Alt and Az adjustments are just like butter!! Anyone with an older EQ6 will appreciate it. I was dialing in my Alt using polemaster and turning the big adjustment knob with thumb and forefinger like I was focusing. Try that with an Atlas! However, these are all amenities, not necessities and I can certainly understand why one might consider the price tag too steep just for them alone.

JMD
Yes, personally I was looking strictly for guiding RMS improvements as I do only imaging, and I need it given my image scale, so the mentioned amenities hardly justify for me going from $1250 mount (I've got it on sale) to ~$3000 mount. I totally agree that Alt adjustment on NEQ6 is a nightmare.
I was surprised though that nobody had a confidence in G11's ability to beat 0.6" guiding RMS on a good night. I thought with supposedly much smaller and smoother inherent PE than NEQ6 it should show better results.

Michael Presley

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #9 on: January 21, 2018, 11:12:41 AM »
The g11 probably does have a smaller native pe.  But clearly your eq6 pe is smooth enough that you can guide it out. 
Jmd

napephona

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #10 on: January 23, 2018, 03:08:38 AM »
Thank you all for your replies, though I have to confess I'm a little disappointed that the consensus seems to be "stick with your old mount." First off, I didn't realize that improvements in tracking error had so little effect on star bloat. I had assumed that improving rms error by a factor of 2 would improve star fwhm significantly, if not by a factor of 2. Certainly, shrinking the stars by some fraction of a pixel isn't worth a couple $K. While the GM811G and LW tripod is a good bit lighter and more portable than the Atlas, I again question whether the benefit to me would be worth the expense, as I do most of my imaging from my back yard. The one question that wasn't addressed is whether the Losmandy would do better left alone for hours, without babysitting, in tougher conditions like passing clouds or wind. In other words, would it do better in adverse conditions that can interrupt the Atlas? I'm a skier and know that wooden planks can make you a hero in perfect snow. It's in wind blown crud that the right equipment shines. I guess I'm wondering what people's experiences are regarding the consistency of Losmandy mounts in a wide range of conditions.

Anyway, I've been at this hobby/passion for going on three years now and I think I'm stuck with it.  So, I'd like to start the process of taking it up a notch. I've identified the weakest links in the system to be a non-cooled OSC camera and a somewhat inconsistent mount. The telescope does remarkably well, even on a 24x36 sensor. The small amount of chromatic aberration is easily processed out. A larger format, cooled monochrome camera, with filters, is currently beyond the budget. That's why I'm exploring mounts. I've read about premium mounts, such as the Mach 1, simply fading into the background and delivering consistent results. I am curious as to whether some semblance of this can be achieved with a Losmandy or if I really need to save my pennies for an AP or SB mount.

alinvibee

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #11 on: January 23, 2018, 01:49:40 PM »
Quote
Thank you all for your replies, though I have to confess I'm a little disappointed that the consensus seems to be "stick with your old mount." First off, I didn't realize that improvements in tracking error had so little effect on star bloat. I had assumed that improving rms error by a factor of 2 would improve star fwhm significantly, if not by a factor of 2. Certainly, shrinking the stars by some fraction of a pixel isn't worth a couple $K. While the GM811G and LW tripod is a good bit lighter and more portable than the Atlas, I again question whether the benefit to me would be worth the expense, as I do most of my imaging from my back yard. The one question that wasn't addressed is whether the Losmandy would do better left alone for hours, without babysitting, in tougher conditions like passing clouds or wind. In other words, would it do better in adverse conditions that can interrupt the Atlas? I'm a skier and know that wooden planks can make you a hero in perfect snow. It's in wind blown crud that the right equipment shines. I guess I'm wondering what people's experiences are regarding the consistency of Losmandy mounts in a wide range of conditions.

Anyway, I've been at this hobby/passion for going on three years now and I think I'm stuck with it.  So, I'd like to start the process of taking it up a notch. I've identified the weakest links in the system to be a non-cooled OSC camera and a somewhat inconsistent mount. The telescope does remarkably well, even on a 24x36 sensor. The small amount of chromatic aberration is easily processed out. A larger format, cooled monochrome camera, with filters, is currently beyond the budget. That's why I'm exploring mounts. I've read about premium mounts, such as the Mach 1, simply fading into the background and delivering consistent results. I am curious as to whether some semblance of this can be achieved with a Losmandy or if I really need to save my pennies for an AP or SB mount.

If your sole measure is your guided rms pe, then the answer is the same even for the premium mounts. Some advantages of the losmandy or more expensive mounts are that 1. They have lower native pe so your guiding does not have to work as hard, 2. Other factors, such as dec backlash and gear eccentricity are reduced and 3. The mounts are better built, more rigid, and can handle scopes of similar weights better, will tolerate wind better, and they can be more forgiving of balancing, etc.. 

It would be interesting to see what your pe curve looks like. Rms values can hide a lot of stuff. A new mount might not give you a "better" guided pe, but it might reduce the number of shots you throw away due to things other than guiding.
You are shooting at a relative low focal length, so small error contributions may be less apparent. If you move to a larger scope your results might be different.

That all said, it sounds like you got a pretty good sample of the eq6. The improvements you get with more expensive mounts are incremental and do not track linearly with cost, much the same as with optics. If you are dedicated to the hobby, and you can afford the upgrade, then treat yourself, I doubt you will regret it. If the cost is a limitation, the keep on taking great pictures with your current gear and don't look back!

Good luck!

Jmd

subliliva

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #12 on: January 31, 2018, 06:43:00 AM »
Klaus,

Another possibility to consider, if you are not against fiddling with your mount, is Rowan belt mod and hypertuning your EQ-6. Belt mod can give you improvements in guiding, at least it should reduce dec backlash - on my NEQ-6 dec backlash definitely gives me headaches sometimes when I'm not lucky with the balance. As I remember Jon Rista reported guiding with RMS around 0.3" on some exceptional night after installing the belt mod.
There is a lot of info on both topics on this forum.

caenalfosen

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #13 on: February 02, 2018, 08:37:36 PM »
Nice summary, Jmd. Once it was clear that improvements in rms values translate to very minor improvements in image quality, the only questions are really about consistency and imaging window. For instance, what kind of weight the mount can handle, how much wind, tracking at lower altitudes, lost subs, etc.. I guess that is part of the question I have about Losmandy mounts. Are they sturdy and precise enough that they can be left alone over night with reasonable assurance that most, if not all, subs will be usable in the morning?
As it is, the EQ does really well within narrow parameters. I've learned to work within those parameters and avoid situations that would expose its flaws. But a typical imaging session involves a lot of time babysitting the mount and keeping it within those confines. I'm curious if a Losmandy mount would be more of a set it and forget it experience, or do you have to go to the $7K mounts for that result?
I really appreciate everyone's insights.

Sam Noble

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Re: Upgrade Atlas EQ-G to Losmandy GM811G?
« Reply #14 on: February 03, 2018, 07:26:46 AM »
Astroby2,
I have considered modifying the EQ6. While I'm not opposed to tinkering, it really becomes a question of time. The mods take time and they're also not free. But I'll look into the belt mod you mention. Thanks.