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Hilmi
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Is this performance typical of G11?
      #5628487 - 01/17/13 05:11 PM

Is guided performance of 1.6 arcseconds RMS typical of a G11 or am I just expecting too much out of my mount? I'm getting to the stage where a Mach1GTO is starting to sound cheap if it is going to resolve all my headaches. My stars at 1260 mm focal length are ovals and that is after guiding. I've put so much effort into this mount and I can honestly say I am not satisfied with the performance. Am I imaging at too long a focal length for this mount?

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Footbag
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5628497 - 01/17/13 05:18 PM

I don't know exactly what problems you are having with the G11, but it is more then capable of imaging at 1260mm assuming you are within the weight limit.

What type of optics? Reflector? Maybe it's mirror flop or flexure? Is it slow steady drift? Or is it back and forth?

The Mach 1 is a great mount, but if you have a problem with your image train or mounting, the mount won't fix it.


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Hilmi
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Re: Is this performance typical of G11? new [Re: Footbag]
      #5628503 - 01/17/13 05:21 PM

I'm using approximately 2/3 the mounts rated instrument load. I'm using an SCT with an off-axis guider with the mirror locked down and an external focuser.

I'm willing to give this mount one more chance in the form of a replacement worm gear. If that doesn't fix it then that's about all I am willing to take from equipment that doesn't perform.

That's not counting all the little bugs like the occasional runaway declination guiding.


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orlyandico
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5628568 - 01/17/13 06:01 PM

1.6" RMS sounds sub-standard.

My CGEM with 40" periodic error and 20" of 8/3 harmonic (which, I am assured by Celestron, is not typical - most CGEM's are around 20" and 7" of 8/3 harmonic) can do 1.8" RMS all day.

Is that 1.6" RMS with long-ish guide exposures? (at least 4 seconds?)

But........

Maybe the roundness of your stars doesn't have much to do with that 1.6" of RMS guiding error. I just started using my C9.25 (2350mm focal length) un-reduced with my Mach1. Due to a variety of issues (cheap $75 tripod, unbalanced load due to not having enough weights) with the C9.25 loaded my RMS guiding error has degraded to about 0.9" - but I still get round stars at native FL (image scale of 0.68"/pixel).

So if I can get round stars at 0.9" at double your FL (10-minute exposures) then I suspect at the much more friendly 1260mm, 1.6" RMS should be just fine.

A lot of folks use G11s for much longer focal lengths than 1.2m so I know the mounts are capable.

Can you post a PHD guiding graph?

I suspect you have some declination guiding issue..


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Peter in Reno
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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5628604 - 01/17/13 06:17 PM

It can depend on a lot of things. Bad seeing can make guiding RMS bigger. Or the quality of guide star in OAG can affect it. Or poor autoguider settings in autoguiding software can play a role. What are you using to measure guiding RMS? What autoguider software are you using?

It took me a while to tweak PHD settings to get highest guiding quality. It varies from mount to mount, scope to scope and location to location. Which looks worse: RA or Dec axis? Do you have graphs for both axis? If Dec looks worse, then maybe backlash? If the stars are ovals, what direction: Dec or RA?

If you are using OAG, what autoguider are you using? Poor quality guide star (too dim or crescent shape) can affect guiding and if your camera is insensitive, then autoguiding software can have issues. I have read that Maxim autoguider is pretty sensitive to strange shaped stars especially off axis from OAG. I use PHD and it does not mind the crescent shape stars.

You may need to do process of elimination outside of the mount before blaming the mount.

This is my typical PHD settings for C-8 EdgeHD at F/10 or 2000mm focal length using A-P Mach1 mount:

RA Aggressiveness: 60
RA Hysteresis: 10
Max Dec Duration: 75
Min Motion: 0.70
Calibration Steps: 125msec
Auto/Resist Switching
Extreme dithering and Settled at < 0.5
3 - 4 sec guiding exposure.

Peter


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orlyandico
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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5628606 - 01/17/13 06:18 PM

.. although that said.. I don't possess tons of cash, so buying the Mach1 only happened after many months of analysis paralysis.

But it has met and exceeded all my expectations. I have spent literally years tweaking and working on my CGEM and AP600. The Mach1 is the first mount I've experienced that simply works out of the box, and keeps on working even when abused (badly unbalanced load).

The first night I got it, I was so delighted with the guiding, I failed to notice that the CP3 controller had gotten so hot I scalded my hand touching it. Turns out the RA worm block was very tight against the worm wheel (must have gotten knocked that way during transportation). But it still kept on chugging and putting up its 3.5" p-p periodic error..

Sure it has its shortcomings. The worst is the 1-star alignment. No pointing model. But.. in my opinion it's better to spend $6.6K for one, than $3.6K for a G11 Gemini 2. Doesn't really help you, I know..


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Hilmi
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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5629324 - 01/18/13 03:51 AM

OK, it's not about tons of cash, it's about the frustration getting to the stage where you don't enjoy the hobby any more. On any typical night you spend 1 to 2 hours trying to get it to work.

Now with regards to some of the questions. It's not declination guiding, for Declination I get an RMS of around 0.5 +/- 0.1

I use MaximDL to guide, I can't use a separate program because my camera is integrated into the filter wheel and you can not address the camera from two different programs at the same time. This puts PHD out of the question.

I am getting slightly distorted stars on my cam (the OAG that's built into the STT-8300) But the reason I don't think that's the reason is that the problem is consistently with the RA axis.

If somebody can teach me how to pull the logs out of MaximDL I'll gladly post them here.


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orlyandico
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5629440 - 01/18/13 07:47 AM

well Hilmi.. I know that feeling of tweaking it for an hour, then having to watch the guiding graph all the time while its exposing because you don't know if it's going to go crazy..

I am surprised that a G11 would behave that way, so many people have success with the G11. But I have never had one.

When I got my AP600, I thought my mount woes were over. But it is a 20-year old design, and it has its limitations. Needless to say, it wasn't "perfect."

The Mach1 is perfect. So far. Have only had a few hours' worth of use on it.


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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5629625 - 01/18/13 10:23 AM

I'm going to just come out and say it. Get the Mach 1.

Is your experience with the g11 typical? No, but hardly unprecedented. Have others had problems getting the tracking accuracy out of the G11 that they really want? Absolutely. Needing to spend time tweaking, adjusting, replacing worms, issues with Oldham couplers and poor quality bearings... That is very common. Based on my own experiences with the Mach 1, all these problems just go away. I have used a Mach1 very successfully for years now coupled to an Eagle portable pier. It has handled a 48 pound imaging load at 2,100mm focal length with no problems. On one memorable night I even managed an image with 3.5" FWHM stars with 20 - 30 knot wind gusts! Why bother on that night? I had driven 400 miles for dark skies, and there was no way I was going to let the transparency go to waste!


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Hilmi
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Re: Is this performance typical of G11? new [Re: Jared]
      #5629648 - 01/18/13 10:36 AM

Only if I find a buyer with only reasonable loss of money on my current mount. But I am really thinking about it. Even got the shipping quote

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Mert
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5629691 - 01/18/13 10:59 AM

Can't help you much Hilmi with the G11, but 1 guy on our
astronomical asociation has 1.
Had a lot of problems with it where the RA-motor was bad.
Also the controller burned out.
I dismantled the whole thing, cleaned, relubed and mounted
everything again.Mecanically I have to say that is is a
VERY decently built mount.
The worst part IMHO are the worm-blocks, independant
square blocks where the worm rides in.
This is a very bad solution, where the Ovision worm
solution is much better, there are a lot of test reports
out there on the web.

What guiding aplication are you using?? PHD, Metaguide,
Maxim, whatever....????
I never had any sucess at all with PHD, then switched over
to Metaguide and bingo, all gooder, better and wonderfuller.

Just my 2


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Startraffic
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5629965 - 01/18/13 01:41 PM

Hilmi,
I believe you have the new one piece worm with the brass high precision worm on your RA, Correct? If you do then I would suspect that the mesh isn't dialed in. It is easier with the OPW than the old worm block system, but it isn't a cake walk DAMHKIT. My G11 would do round stars using a Meade 10"f4 SNT with a 4x Powermate to a Meade DSI & a 90mmf4 Ioptron as a OAG & MaxinDL. It wasn't easy to get it to work, I had a LOT of flexture problems, balance problems, firmware problems, etc. I had been evolving my G11 from DCS's & was also in a observatory as you are. There were times I wanted to take mine to the dump as well. You're setup should work.
I was about to post this & remembered something else. Are you balancing slight heavy to the east? You don't need much, 500g is fine, but it needs to be there to keep the RA mesh snug. I think there is a mod in the Losmandy forum that helps address this, but I couldn't find it. It basically had a string wrapped around the RA & a weight on the end to keep the mount biased to the east. You would lift the weight, get the mount in perfect balance, then let the weight hang free, effectively biasing the mount to the east. I can't remember where I saw it or how it was done, but I do remember the hanging weight.

Jared,
I believe Hilmi's mount has G2, & the OPW, they don't use Oldham couplers, they have a different type, no more Oldham coupler stickage issues. The OPW also becomes a module when assembled, you adjust the entire module for the gear mesh & clearance.

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Hilmi
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Re: Is this performance typical of G11? new [Re: Startraffic]
      #5629997 - 01/18/13 01:58 PM

I have the OPWB and I have tried all the adjustment mojo I could find online. Even that guy who suggested I spill some chicken blood on the worm block while dressed in a loin cloth. Everybody says it works once you get the hang of it but no concise instructions.

My theory is that if this was a seeing induced problem it would hqve impacted both axis. Not just RA. Maybe as a last ditch effort I should go for the ovision worm. At least that comes with consice directions on how adjust and install


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Footbag
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5630015 - 01/18/13 02:10 PM

Quote:

Even that guy who suggested I spill some chicken blood on the worm block while dressed in a loin cloth. Everybody says it works once you get the hang of it but no concise instructions.





Are you sure your chicken was a virgin?

Sorry, I couldn't help myself.


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Hilmi
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Re: Is this performance typical of G11? new [Re: Footbag]
      #5630032 - 01/18/13 02:35 PM

So thats why it didnt work

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Startraffic
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5630081 - 01/18/13 03:04 PM

Adam,
The chicken doesn't matter, Hilmi has to be the virgin, Uh Oh

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Footbag
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Re: Is this performance typical of G11? new [Re: Startraffic]
      #5630107 - 01/18/13 03:22 PM

Ok. Now we're just making the astrologers look sane.

Edit: O-vision worm for sale on A-mart. Located on Hilmi's side of the Earth.


Edited by Footbag (01/18/13 03:36 PM)


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Hilmi
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Re: Is this performance typical of G11? new [Re: Footbag]
      #5630672 - 01/18/13 10:14 PM

Thanks, I took a look at the Ad this morning. Because he is including those McLennan gearboxes, he is selling that stuff very close to the price it comes from the manufacturer. Installation instructions for those gear boxes look terrifying. So I'm not so sure I want them.

Looking at buying direct from the manufacturer.

Edited by Hilmi (01/18/13 11:40 PM)


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contraf15
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5634444 - 01/21/13 07:54 AM

Hilmi I have a G11 G2 that I bought new this month with the one piece worm. I am having exactly the same issue guiding with MaximDL, SBIG STi and OAG. Polar alignment is spot on, declination guiding is nearly a flat line, but I get spikes in RA every several seconds that stretch stars accross the RA axis of the imaging camera chip. The mount is perfectly balanced, and I have a 22 oz weight hanging on the east side of the declination shaft to keep the gears meshed east-heavy. The problem occurs with or without the weight. I have tweaked every possible guide setting in Maxim, guide speed on the mount, etc. and it does not improve. It must be something mechanical. I am going to try swapping the RA and DEC gearboxes and see if that makes a difference, but short of that I'm not sure what else to try. Please post if you figure it out on your mount...

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Hilmi
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5634516 - 01/21/13 08:56 AM

I read somewhere that the gear boxes only contribute 0.16 arc seconds of error. I think its the worm or worm block.

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Startraffic
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5634759 - 01/21/13 11:30 AM

Contraf15,
What is the time period of the RA jump? That should give you a clue as to where it's coming from.

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contraf15
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Re: Is this performance typical of G11? new [Re: Startraffic]
      #5635934 - 01/21/13 11:15 PM Attachment (80 downloads)

That's one of the problems...it isn't periodic. I'm attaching a 15-minute log file from this evening. I was guiding with an ST-i, SBIG OAG through a Stellarvue SV80ST with a TeleVue 0.8x reducer. With the reducer the scope has a 384mm focal length, so the pixel scale for the STF-8300 is 2.9 arcsec/pixel. Even at that scale the RA deviations are obvious in the main camera images. The SBIG OAG provides a further reduction of 0.7x, so the guiding focal length is approximately 269mm. That gives a guiding pixel scale of ~5.7 arcsec/pixel. You can see in the log file sudden deviations of up to 4.2 pixels (I've seen as high as 9 on occasion). That's from 24 to 50 arcsec of sudden movement! Of course this makes exposures of any length worthless because it happens so frequently and is totally unpredictable. I must be missing something...any ideas??

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Hilmi
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5636064 - 01/22/13 12:59 AM

I'm seeing similar issues, the guide plot looks so erratic! Bounces all over the place. Tried fiddling with guiding aggressiveness etc... no effect. Guide through pulse guide and through ST4 connection, no joy. Try using PEMPro, and PE is so low and the curve is very smooth. Can't recall the figures I am abroad now and I am far from my imaging laptop, but PEMPro is showing me a smooth curve and PE in line with the results reported for Ovision worms.

Can you try the same thing on your side Contraf15? Measure PE without guiding.


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orlyandico
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5636081 - 01/22/13 01:13 AM

if there are sudden jumps that seems like slack in the RA gearing... or on the other hand maybe the worm is too tight and the jumping is due to stiction..

maybe try loosening the RA worm engagement. i have no G11 but on my CGEM, when the RA slack is very small (tight worm-to-gear mesh) there are a lot of problems. These go away when the worm is looser.


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contraf15
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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5636271 - 01/22/13 06:14 AM

I suspected the gear mesh might be the culprit, so last night I adjusted it across the full range allowed by the thumb screw on the one piece worm block. There was no change.

Hilmi I will try to get a PE measurement within the next couple of days.

Jeremy


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orlyandico
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5636291 - 01/22/13 06:32 AM

this is not an option for Hilmi, but i bet if you send it to Ed Thomas at deepspaceproducts he would be able to resolve this.

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contraf15
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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5636295 - 01/22/13 06:37 AM

I'm sure he could, but for the ~$4000 I have invested in this brand new mount I shouldn't have to send it to someone to get it tracking correctly

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orlyandico
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5636346 - 01/22/13 07:42 AM

Good point. But I do know folks with G11s and they don't have these problems.. I bet its something really simple.

Have you tried calling Losmandy? (as opposed to emailing or going to their forum)


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Startraffic
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5636614 - 01/22/13 10:40 AM

Contra15,
I pulled your tracking into a spreadsheet & looked at it. I found some inconsistencies, The number of intervals per hour is erratic anywhere from 12 to 17 intervals per hour and the time between those intervals is anywhere between 3" to 7". So the tracking itself isn't consistent nor is there a pattern that I can see (i.e. the dreaded 44" error), There also seems to be a connection between the brightness of the guidestar and the time between the tracking intervals. It seems that if there is a change in brightness up or down of greater than 2000 the time between the corrections is longer. This would cause the amount of correction to be greater.
Is your guidestar bright enough?
Are you having trouble "seeing" the star with the guidescope?
It seems like the guidescope may be chasing seeing. I could be wrong but it feels that way. It might be worth trying unguided vs guided to see if the problem still can be isolated that way.


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contraf15
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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5636720 - 01/22/13 11:46 AM

I think it must be something simple as well. It is a big enough deviation that I must be missing something. I hope so, anyway.

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contraf15
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Re: Is this performance typical of G11? new [Re: Startraffic]
      #5636747 - 01/22/13 12:01 PM

Startraffic,

Thanks for taking a look at the data. Maxim was set up for 3 second guide exposures when I took this data. It looks like it actually updated somewhere between 3-4 seconds depending on the cycle.

I noticed the same thing you pointed out with the brightness fluctuations. The star looked as good as I have been able to get with the OAG at this f-ratio (4.8) and the seeing was pretty good. The guide stars are definitely not pinpoints, but they are fairly bright and seem consistent. This data is typical of what I have seen on other nights with other guide stars.

I think my next course of action will be as follows:
1) Test the PE with no guiding as Hilmi suggested
2) Try unguided exposures and see if the stars look any better
3) Try guiding through a separate scope (maybe the field curvature is playing havoc with the OAG?)
4) Try the OAG with another, slower scope with a flatter field (I have a 127mm f7.5 that has a very flat field, haven't tried it yet with the new equipment).

I'll post my results.

Jeremy


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JoseBorrero
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5637256 - 01/22/13 04:17 PM

well, I have some mixed experience in the past with my G11, I replaced the worm to the losmandy one with same worm, but at same time, I bought the miniguider scope from zhumell same as Orion brand together with the Starshoot autoguider and I always use PHD, unluckly maxim doesnt work much for me on guiding. Now I'm getting the lowest RMS ever on PHD, I did test it with my AT6RC at f/9 and got best rounds stars ever. Which so small and widefield miniguide scope guiding on bright stars almost always my PHD exposure time is best a t 0.2 sec that is pretty much live. I can't really tell if the block was the problem or the miniguide scope focal lenght helped.

My second setup that work pretty similar was using an Orion ST80 with SSAG in Tandem with an Orion ED80. I have so many mixed results. Some night I took long times just recording PHD settings. From 3 setup optics I have two different PHD settings written in a book so I can forget and use over and over, those that have produce very good results.

It is very possible that just trying PHD and trying different settings may help. also a miniguide isnt expensive at all to try. I got the TS9 OAG and now is just set there with no job as the miniguider is the winner.


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NJScope
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5637953 - 01/22/13 11:00 PM

Hilmi

If you physically disconnect the guide scope cable from the Losmandy mount do you still see the erratic jumps in RA? About a year ago I purchased an SBIG ST8X camera with auto guide to replace an ST402ME and external guider. I immediately had problems with erratic guiding in RA which after months of investigation was solved by the purchase of SBIGs optocoupler. According to the manual my particular Losmandy G11 should not have required one, however, it clearly fixed the problem.


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Hilmi
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Re: Is this performance typical of G11? new [Re: NJScope]
      #5638057 - 01/22/13 11:54 PM

Thanks for the suggestion Kevin, but I have tried guiding through ASCOM driver without the ST4 cable with the same results. So I don't think that's it.

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wolfman_4_ever
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5638160 - 01/23/13 01:25 AM

wow.. 12 to 17 sounds like its sticking.. especially when you say it jumps...

if it is sticking, you can watch an inline amp meter to watch the amps jump up when it hits that point.. Motor will get hot too..

A TDM would solve your issue. i'd still worry about the motors getting too hot..


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Hilmi
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Re: Is this performance typical of G11? new [Re: wolfman_4_ever]
      #5638170 - 01/23/13 01:33 AM

And here comes the TDM marketing plug :P

Just pulling your leg


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orlyandico
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5638174 - 01/23/13 01:41 AM

G11 G2 + TDM is very close to the price of a Mach1... and to those who say a TDM will outperform a Mach1, well maybe it will and maybe it won't. But mine does 0.42" peak to peak after PEM. A PE that low is in the same range as a TDM.

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contraf15
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Re: Is this performance typical of G11? new [Re: wolfman_4_ever]
      #5638313 - 01/23/13 06:57 AM Attachment (32 downloads)

The motors do not get hot. At all. And while I appreciate that Ed Thomas or the TDM or a variety of other things would solve the problem (including a Mach 1), so would buying the McDonald Obsevatory. This is a brand-new mount that is capable of much better guided performance than it is giving, and I'd like to figure out what is getting in the way.

Given that my guiding logs show a dramatic change in guide star intensity every time one of these deviations occur, I decided to take the STi out of the OAG and mount it in a 50mm guidescope to see if that would make a difference. I'm still not sure if the change in brightness is a cause or an effect of the RA guiding deviations. Well, just my luck the tube was too short to bring the STi to focus. So I replaced it in the OAG but cut an aluminum shim to keep it orthogonal in its socket (who at SBIG came up with the design of that thing? There is a huge gap in the socket and just two nylon thumbscrews to hold the camera! You can tighten it down through a wide range of lens-to-chip of angles). I digress...

With the camera better positioned in the OAG, I was actually able to get round guide stars for the first time. I let the mount guide all night long while the imaging camera took 300 second exposures. Lo and behold, the frequency and severity of RA deviations decreased (but they did not go away). The screen shot attached tells the story...fairly stable guiding graph in DEC and RA, with occasional RA deviations of up to 2.5 pixels (~14 arcsec). You can see from the background image what this is still doing to the stars.

So what does all this mean? The deviations still happen, so I'm not sure (and the log still shows a decrease in guide star brightness at those times). I don't think this is about chasing guide stars. The DEC plot never changes and it is guiding off of the same star. I think movement is occurring in RA, which causes the change in brightness by moving the star in the highly curved guider FOV. But that doesn't explain why repositioning the STi improved the tracking (some of the 300sec subs actually had no deviations, maybe 10% of them).

So I am confused. And frustrated. And tired...


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Startraffic
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5638344 - 01/23/13 07:45 AM

Contra15,
Hmmmm, it looks like there IS a pattern at about 70". I'm now beginning to think grit or possibly a gall on the worm or on of the gears in the gearbox. The worm is an "easy" thing to find, the GB is, of course, a sealed unit. I'd look into swapping the GB & seeing if the problem goes away. (no $$$, just time). If it goes away the I'd contact Losmandy about a warranty replacement GB, (You'll have the proof in your tracking graphs), if not then look to the worm. If the worm is bad then again warranty replacement, if it's dirt that is also easy. I know that's not much help or consolation but there is a solution. We just haven't found it yet, it's also easy for me to say, it's not my mount, but I do understand. BTDT & hated it.
I hate those GB because you can't do any servicing on them. I guess it's time to get back to making mine.

Clear Dark Skies
Startraffic
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Raginar
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Re: Is this performance typical of G11? new [Re: Startraffic]
      #5638465 - 01/23/13 09:10 AM

Reminds me of guiding my CGEM in MaximDL. No matter what setting I changed, it wouldn't guide. Swapped over to PHD and immediately had improvement.

I wish Maxim was easier to use


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Hilmi
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Re: Is this performance typical of G11? new [Re: Raginar]
      #5638917 - 01/23/13 01:11 PM

Thats not an option for me. The guide camera acts as one camera with the main and thus needs to be accessed from the same software used for imaging.

I am now back in Oman and cand do a test with PHD to validate


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wolfman_4_ever
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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5638946 - 01/23/13 01:30 PM

Quote:

G11 G2 + TDM is very close to the price of a Mach1... and to those who say a TDM will outperform a Mach1, well maybe it will and maybe it won't. But mine does 0.42" peak to peak after PEM. A PE that low is in the same range as a TDM.




Maybe it will, maybe it won't huh? Mine does .11" peak to peak with the TDM... I love it when people say, maybe it will maybe it won't when I have provided logs. What happens when I provide the logs? The thread dies. People have their foot in their mouth and hands in air unable to believe the performance..

I've said it before and I'll say it again. My CGE-Pro and TDM will smoke.. SMOKE!!!! any AP, SB, highend consumer mount.

Put that in your Mach1 and smoke it..

Stock PE, 15+ range..
DSP/Aeroquest love. = 7.8
DSP/AeroQuest Love + PEC = 1.7
No PEC TDM Only = .11


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orlyandico
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Re: Is this performance typical of G11? new [Re: wolfman_4_ever]
      #5639008 - 01/23/13 02:28 PM

hi Dave, 0.11" is indeed a very good figure that I wasn't aware of. Other folks are using SiTech tick management (not quite the same as TDM, I know, but same principle) and are getting sub-1" but not 0.1" range, hence my statement that 0.42" is same range.

But I was talking about the G11 + TDM which would be around $5400.

This post indicates 2" p-p with a G11 and TDM..
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/4596205/page...

while this
http://www.explorescientific.com/jerry_hubbell/

(EQ6) indicated 1.4" p-p with an EQ6. Both figures are not quite at the 0.11" p-p that you mention. I think the TDM does better if the native PE is smaller to begin with. But this is all hair-splitting, anything <1" is I would think practically comparable.

CGE Pro's particularly the newer ones seem to have better performance than G11's given that Celestron is also now guaranteeing +/- 3" raw PE. I don't think Losmandy gives such a guarantee.

That said.. I have a Baumer encoder lying around (similar to the 250 Euro Heidenhain encoder in the TDM) and one of these days I'll bolt it to my CGEM and see where that goes.

I am not saying the TDM is not a good idea, it is. I think it is way too expensive though given that the encoder - the most expensive part - is $400. I also stand by my original assertion that a G11 G2 + TDM is not a good buy compared to a Mach1 since the prices are very similar and the performance is comparable in terms of PE. And imaging performance isn't all about PE, declination guiding has been my biggest headache and that issue is non-existent with the Mach1, at least for my payloads.


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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5639054 - 01/23/13 02:57 PM

The reduction in guide star brightness whenever you have one of the RA "excursion" is likely because the star itself is being blurred by the movement. That would cause the peak pixel to dim significantly--just like with an out-of-focus star.

It may well be as simple as some grime in the worm or somewhere in the gear box. I'd be happier suggesting that if there were a more clearly defined periodicity. It does hint at a 70s or so cycle, but I'm not really sure.

If you've already tried adjusting the mesh and have ensured that the scope is slightly East heavy, the next thing to try might be to clean and re-lubricate the worm.

Oh, one thing I found very helpful when I had a GM-8 with the older style worm and blocks was to disconnect the motor and gearbox and try turning the worm by hand. You'll be able to feel if there is any grit or roughness at any point in the cycle. Don't know if you can do that with the newer mounts, but I would assume so. This also helped me feel the difference between East and West heavy on my mount--it was quite dramatic in "smoothness".


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wolfman_4_ever
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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5639059 - 01/23/13 03:03 PM

A lot of equipment is way more expensive just because it's description of use changes from the norm to "Astronomy" My wife likes to call us "SNN" Successful Nerd Network. Not being racist but most are 30+, white, with, (I hate this term) disposable income. Vendors know this and market it that way. Certain "Astronomy" gear is used in other fields. If you do your research, you can find the same item, marketed to a different population, at more than half the cost. Item's imported from other countries also fall into this category. This discussion most recently went on in the Video Camera forum. A certain pier/moving column vendor comes to mind as well. This is America after all. We profit off death and old people..

This topic is best left for another forum. Let's get back to the OP original question..


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orlyandico
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Re: Is this performance typical of G11? new [Re: wolfman_4_ever]
      #5639068 - 01/23/13 03:10 PM

Dave, you're right. Though the TDM is a valid approach at fixing G11 issues (and so is the Mach1) so I would think still pertinent to OP.

That said I really can't wrap my head around the G11. There are many users some of whom I know personally who love the thing. Then you have this group which has inexplicable problems with it.. makes me glad I didn't go this route.


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wolfman_4_ever
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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5639089 - 01/23/13 03:19 PM

If this is such an issue.. why doesn't anybody talk to Scott? It's Losmandy's issue. Has there been an official or even off the record response to these issues? Is it really even an issue or a few issolated issues? I understand a user wanting to get the quickest answer they can by posting on a public forum (you have to figure someone else in the world had to have the same issue once before) from an issue but shouldn't they be attacking on 2 fronts by also contacting the manufacture?



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contraf15
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Re: Is this performance typical of G11? new [Re: wolfman_4_ever]
      #5639106 - 01/23/13 03:28 PM

I will absolutely contact Losmandy and OPT if I determine there is something wrong with the mount. At this point I haven't made that determination. With so many variables, it is far more likely that I am missing something. The list of possible culprits is getting smaller, but sending the mount back or having it replaced is not a trivial matter (especially if a replacement will behave the same way). The machining and pointing accuracy of this mount are far superior to anything I have previously owned, so I want it to work and will spend some time to get it working correctly. If the problems remain after I have exhausted the list of things I may be doing wrong, then I will conclude it is faulty and go from there.

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Hilmi
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5639128 - 01/23/13 03:47 PM Attachment (29 downloads)

OK, here is my run of PE analysis from PEMPro

First of all lets clarify a few things
-I did run the calibration wizard first
-I ran the data gathering for a full half hour using 4 second exposures


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Hilmi
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5639131 - 01/23/13 03:47 PM Attachment (25 downloads)

The frequency analysis screen

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Hilmi
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5639134 - 01/23/13 03:49 PM Attachment (22 downloads)

And the exported log file.

Now either I am doing something very stupid, or these results don't correlate with what I am seeing when using the mount.

Edited by Hilmi (01/23/13 03:50 PM)


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wolfman_4_ever
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5639206 - 01/23/13 04:32 PM

Quote:

I will absolutely contact Losmandy and OPT if I determine there is something wrong with the mount. At this point I haven't made that determination. With so many variables, it is far more likely that I am missing something. The list of possible culprits is getting smaller, but sending the mount back or having it replaced is not a trivial matter (especially if a replacement will behave the same way). The machining and pointing accuracy of this mount are far superior to anything I have previously owned, so I want it to work and will spend some time to get it working correctly. If the problems remain after I have exhausted the list of things I may be doing wrong, then I will conclude it is faulty and go from there.






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orlyandico
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Re: Is this performance typical of G11? new [Re: wolfman_4_ever]
      #5639453 - 01/23/13 07:25 PM

Can you show the raw data? Pempro final PE curve that you show is already smoothed and the large single excursions and non integer periodic stuff like the celestron 8/3 are no longer shown.

Your result does show that there isn't anything inherently wrong with your G11...


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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5639679 - 01/23/13 10:32 PM

Hilmi:

Let me expand my comments a little further so that I can better understand your problem with the G-11. Does your G11 jump in RA unpredictably (non-periodic) with all cameras cables disconnected from the Gemini front plate (not just turned off but physically disconnected)? If the answer is yes then there is a serious problem with the mount which can not be corrected with guiding. However, if all equipment is disconnected from the Gemini cable interface plate and you only see drift expected from imperfect polar alignment and worm gear periodic error then I think it is worth revisiting my suggestion about the guide camera interface cables. I came very close to returning my ST8XME to SBIG because of a similar experience while trying to use the internal guide camera. Even if it was turned off but the cable connected, RA would jump indiscriminately in the middle of imaging. Only after completely disconnecting all camera interface cables from the Gemini faceplate, did the Losmandy G11 behave normally, albeit with the uncorrected drift and worm gear PE. Once I installed the relay-adapter box from SBIG between the camera and autoguider input on the Gemini faceplate, all problems with random RA jumps disappeared even though the Gemini 1 Level 4 manual says that the SBIG relay box can be used but is unnecessary. BTW, the Losmandy optocoupler is not compatible with the newer Geminis so that my initial reference to the optocoupler rather than the SBIG relay box is incorrect (failing memory with age!).


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wolfman_4_ever
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Re: Is this performance typical of G11? new [Re: NJScope]
      #5639883 - 01/24/13 12:57 AM

cable sag strikes again! I've been bit by that monster before.

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Re: Is this performance typical of G11? new [Re: wolfman_4_ever]
      #5639931 - 01/24/13 01:52 AM

let me just say that i have the same setup as Hilmi (almost - i actually don't have the one-piece worm block) and i am almost as frustrated. i have been able to get round stars on some very long Ha exposures, but only near the pole. at the equator the RA errors are happening too fast for the OAG to compensate. without PEC the mount has 30 arcseconds pk-pk error. with PEC its on the order of 7-10 but the mount keeps forgetting that it has a PEC curve available. very frustrating.

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contraf15
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Re: Is this performance typical of G11? new [Re: pfile]
      #5649543 - 01/29/13 12:10 AM Attachment (31 downloads)

Well the weather has been terrible in South Central Texas so I haven't been able to test guiding for a while. But I have been able to do a few things.

Hilmi, I went back and read some of your posts from shortly after you bought your G11. I also bought mine from OPT with the one-piece worm block installed, and I initially had exactly the same issue you did. Namely, the Ruland coupler was not tightened down on the RA worm and the mount would slip when slewed in RA. I took apart the worm block and tightened it up the day after I put the mount together.

Over this last weekend I took it apart again to investigate further. It turns out that the coupler itself was not assembled correctly. Each disc in the coupler is secured by four tiny hex bolts, two of which are accessed through holes in the ends of the device and two of which can only be accessed after removing one of the end pieces. Two of these internal bolts on mine were so loose that they were close to falling out. This resulted in the coupling itself being flimsy in both torsion and lateral offset. If I understand the purpose of the thing correctly, it is to allow some motion laterally (in case the gearbox and worm are not perfectly aligned), but transmit all rotational motion (should be rotationally rigid). Mine wasn't even close until I disassembled it and tightened it up. You can see the hex bolts that were loose in this picture. This is just the beginning of my adventure, though...


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contraf15
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5649554 - 01/29/13 12:17 AM Attachment (48 downloads)

While I had the worm block disassembled, I decided to inspect the worm itself. I found an area on it where it looks like the threads are actually damaged. You can see it on the attached pictures, though it doesn't show as well in the pictures as it does looking at the worm. I don't know if this is significant enough to affect tracking, and the sides of the threads (the part that contacts the teeth on the RA gear) look fine. But just to be sure, I decided to check out the DEC worm. It was perfect. No visible flaws. I swapped the worms and the gearboxes on the two axes. Still not the end of the story...

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contraf15
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5649570 - 01/29/13 12:35 AM Attachment (30 downloads)

Now things really started to get interesting. When I went to reassemble the one-piece worm block, I must have over-torqued the hex bolt that clamps to the gearbox shaft. I think I stripped the threads because I could not get it to tighten down. As a last resort I decided to re-tap them using a slightly larger diameter. What I didn't do was drill a larger pilot hole first, and just my luck the blasted tap snapped in half so that I couldn't retrieve the part that was now embedded in the coupler. A quick search online showed that Losmandy doesn't even sell the Ruland couplers by themselves (just Oldham couplers). The manufacturer wants $107 for one and they don't ship for 10 days. I did find a distributor who sells them for $70, but again the wait is a couple of weeks.

So...I drilled and tapped a hole in the gearbox side of the Ruland coupler for a set screw and used a small 3/32 hex grub screw to connect the gearbox. It turns quite freely and there is no binding or pulsing. In fact, since the grub screw holds the flat side of the gearbox shaft, I think it is more secure than the old way. You can see it at the top of the coupler in the picture.

Now that everything is back together, RA slews sound much better than before. I think the loose coupler may have been the source of my random RA movements. Unfortunately I can't test it out until the weather is better. And of course when I do test it, I won't know if changes are from swapping the worms, the gearboxes, fixing the coupler, or breaking the tap and jerry-rigging the coupler. So much for controlling my variables!


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Hilmi
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5649581 - 01/29/13 12:47 AM

That's very interesting, I will go look at my coupler and see if there are any loose parts. It never occurred to me to check if it was assembled correctly. I had just contacted Ed about hyper-tuning and he was great, he was concerned about the several hundred dollars of shipping cost and offered to guide me through the process. I'm still trying to convince him to take a consulting fee. A very generous man.

I plan to take the mount apart, strip it and rebuild it this coming Thursday. I'll watch out for that potential problem you highlighted.


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orlyandico
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5649635 - 01/29/13 02:06 AM

Hilmi, buy the kit and DVD from Ed in lieu of a consulting fee.

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Hilmi
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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5649646 - 01/29/13 02:25 AM

Unfortunately there is no Kit for the G11. He sells lots of other bits and pieces that will be of use to me Next time I need something, I'll first check if he sells it before looking anywhere else.

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orlyandico
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5649652 - 01/29/13 02:37 AM

i ended up buying the DVD for the CGEM. i suppose the tips will prove handy for my AP600. had the same problem as you - shipping the AP600 to Ed would cost me $450 each way.

speaking of which.... there's some terrible DEC stiction on my AP600. i spent over a year fighting it and in the end gave up and got a Mach1.

now the AP600 sits there accusing me i'm hoping with Ed's DVD and some bearing scraping i can fix the declination. the RA is fantastic on the thing.. if i can fix the DEC i'm sure it will perform very well...


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Re: Is this performance typical of G11? new [Re: contraf15]
      #5650006 - 01/29/13 10:30 AM

Quote:

While I had the worm block disassembled, I decided to inspect the worm itself. I found an area on it where it looks like the threads are actually damaged. You can see it on the attached pictures, though it doesn't show as well in the pictures as it does looking at the worm. I don't know if this is significant enough to affect tracking, and the sides of the threads (the part that contacts the teeth on the RA gear) look fine. But just to be sure, I decided to check out the DEC worm. It was perfect. No visible flaws. I swapped the worms and the gearboxes on the two axes. Still not the end of the story...




It actually shows quite well in the picture. That worm is trashed. The damage is right in the area that the worm rides on the wheel and it is significant. It would be a periodic error, but it would be huge. In addition, if there is that damage, then there is likely additional damage like the worm not being straight. It takes a lot less damage than that to make a worm useless.

I would definitely replace that worm and if it still under warranty I would show them the picture and ask for a replacement.


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Startraffic
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5650185 - 01/29/13 12:17 PM

Contraf15,
Oh yeah that worm is bad & needs to go back. I can possibly even tell you how it got that way. Look at the RA gear very carefully. I'll bet the axis "jumped across the worm at some point from not having the clutch tightened up during balancing, & the Worm not having enough "bite" to hold it in place. DAMHIKT IIRC the anodized aluminum is harder than the brass worm & chewed it like a file. Check the RA gear for damage as well, I "should" be ok but....

Clear Dark Skies
John
39.138274 -77.168898


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contraf15
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Re: Is this performance typical of G11? new [Re: Startraffic]
      #5650250 - 01/29/13 12:50 PM

Thanks Ed and John for the replies. I'm going to send a picture of the worm to OPT and see what they say. I have been very careful with the mount (with the exception of the coupler buffoonery) and I know that the damage didn't happen here. I suspect it happened at the time of the sloppy one-piece worm installation.

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Re: Is this performance typical of G11? new [Re: contraf15]
      #5650308 - 01/29/13 01:19 PM

Contraf15, I tried tightening the coupler I also have a bearing that felt a little rough so I moved it to the dec axis. Cant test anything, its cloudy.

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contraf15
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5651785 - 01/30/13 08:34 AM Attachment (27 downloads)

OK, finally had some clear skies last night to test things out.

The short version: I am ready to throw this thing in a lake. My CGEM tracked better than this.

After changing the RA worm, gearbox, and bearings, I continue to get trash results with RA tracking. Deviations were on the order of 10-15 arcsecs, and they were quick (unable to guide them out). I tried guide exposures anywhere from 0.5 secs to 4 seconds in an effort to get in front of whatever is causing the problem, but no luck.

The deviations appear to be periodic, on the order of every 120 seconds or so which corresponds to half the worm cycle. But this is with a completely different worm than before! I honestly don't know what could even cause such behavior. I am out of ideas, other than return the silly thing. But I don't know what part of it is defective.

Any suggestions?

Jeremy


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contraf15
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5651792 - 01/30/13 08:38 AM

Same results with PHD by the way, tried that too.

Jeremy


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Re: Is this performance typical of G11? new [Re: contraf15]
      #5651868 - 01/30/13 09:23 AM

I don't know what the problem is - it could be inside the gearbox - I don't know, but something that fast would be best studied with video. If you have a web-cam or video camera you can connect to the telescope, you could use MetaGuide (free, my software) to study the behavior of the star in detail onscreen, and even record its position at video rate. It may give insight into the cause, but either way would be interesting to see.

I don't know if you are showing a passive log or a guiding log - but the star appears to stop and "catch" - then suddenly snap forward. I may be misinterpreting it though.

Anyway - something this fast would be helped by video, and there is free software for the purpose.

Frank


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Re: Is this performance typical of G11? new [Re: freestar8n]
      #5651948 - 01/30/13 10:05 AM

Jeremy,
PM sent.

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Re: Is this performance typical of G11? new [Re: Startraffic]
      #5652271 - 01/30/13 12:57 PM

Hi Startraffic,

For some reason I didn't receive the PM. Can you resend?

Thanks,

Jeremy


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Re: Is this performance typical of G11? new [Re: contraf15]
      #5652283 - 01/30/13 01:04 PM

Jeremy,
On its' way
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5653097 - 01/30/13 07:45 PM

Quote:

OK, finally had some clear skies last night to test things out.

The short version: I am ready to throw this thing in a lake. My CGEM tracked better than this.

After changing the RA worm, gearbox, and bearings, I continue to get trash results with RA tracking. Deviations were on the order of 10-15 arcsecs, and they were quick (unable to guide them out). I tried guide exposures anywhere from 0.5 secs to 4 seconds in an effort to get in front of whatever is causing the problem, but no luck.

The deviations appear to be periodic, on the order of every 120 seconds or so which corresponds to half the worm cycle. But this is with a completely different worm than before! I honestly don't know what could even cause such behavior. I am out of ideas, other than return the silly thing. But I don't know what part of it is defective.

Any suggestions?

Jeremy




I could be that you have the worm spacing too tight. That can cause the worm to catch and spring free and will accentuate imperfections in the worm. I would back off the spacing a little bit and see what happens.

However, if it is not the worm spacing, and assuming that you did not change the motor or the worm wheel, they are about all that is left. A motor problem doesn't seem likely but I suppose it is not impossible. A defectively cut worm wheel is a possibility. Overall, it sounds like it is time for a return. With the damage to the worm, it's hard to say what other damage the mount may have sustained, but when unexplainable things are happening with a mount that is usually better behaved, that tends to suggest that something bad happened to it.


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Re: Is this performance typical of G11? new [Re: EFT]
      #5653121 - 01/30/13 07:55 PM

Thanks for the comments Ed. I did change the DEC and RA motors when I changed the worms. Is there a way to check the worm wheel? Tonight I am going to try guiding with a different camera through the ASCOM driver instead of the ST-4 port like I've been doing. I don't anticipate any change, but I have to try everything. I'll also isolate each cable just in case there is some crazy RF interference or something.

This is really frustrating after dropping almost 12 grand on new gear last month. Maybe I need to take up needlepoint instead.


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Re: Is this performance typical of G11? new [Re: contraf15]
      #5653138 - 01/30/13 08:16 PM

Probably the only good way to check the worm wheel is to remove it, clean it, and then look at it under magnification. That is obviously a lot of trouble, but the wheels are interchangeable and not terribly difficult to get at, so you could try trading them out as well.

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Re: Is this performance typical of G11? new [Re: contraf15]
      #5653174 - 01/30/13 08:42 PM

Quote:

The deviations appear to be periodic, on the order of every 120 seconds or so which corresponds to half the worm cycle. But this is with a completely different worm than before! I honestly don't know what could even cause such behavior. I am out of ideas, other than return the silly thing. But I don't know what part of it is defective.

Any suggestions?

Jeremy




It could also be due to the worm bearing runout. That can cause periodic glitch in tracking as the worm wobbles about the bearing.


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Re: Is this performance typical of G11? new [Re: contraf15]
      #5653266 - 01/30/13 09:46 PM

I don't know at which focal lenght are you guiding, but It became easy to me to autoguide with the miniguide scope even than OAG.


Quote:

OK, finally had some clear skies last night to test things out.

The short version: I am ready to throw this thing in a lake. My CGEM tracked better than this.

After changing the RA worm, gearbox, and bearings, I continue to get trash results with RA tracking. Deviations were on the order of 10-15 arcsecs, and they were quick (unable to guide them out). I tried guide exposures anywhere from 0.5 secs to 4 seconds in an effort to get in front of whatever is causing the problem, but no luck.

The deviations appear to be periodic, on the order of every 120 seconds or so which corresponds to half the worm cycle. But this is with a completely different worm than before! I honestly don't know what could even cause such behavior. I am out of ideas, other than return the silly thing. But I don't know what part of it is defective.

Any suggestions?

Jeremy




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Re: Is this performance typical of G11? new [Re: JoseBorrero]
      #5653422 - 01/30/13 11:31 PM

OK, I've been watching this thread. I had the same issues. Even worse!
Sent the g11 to ed Thomas got it back and it was flawless.


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Re: Is this performance typical of G11? new [Re: powerstroke01]
      #5653488 - 01/31/13 01:04 AM

i am in no way questioning Ed's service.. but i'd be pretty upset if a $3600 G11 G2 needed a hypertune right from the store...! now if it was an old $1200 non-Gemini G11, or a Synta mount, then it's expected..

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Re: Is this performance typical of G11? new [Re: powerstroke01]
      #5653942 - 01/31/13 09:48 AM

Quote:

OK, I've been watching this thread. I had the same issues. Even worse!
Sent the g11 to ed Thomas got it back and it was flawless.




Thanks Jarrod. I'm glad that it is working now.


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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5653947 - 01/31/13 09:51 AM

Quote:

i am in no way questioning Ed's service.. but i'd be pretty upset if a $3600 G11 G2 needed a hypertune right from the store...! now if it was an old $1200 non-Gemini G11, or a Synta mount, then it's expected..




I would agree with this. When a mount clearly doesn't work out of the box because of a problem with the mount (as opposed to user error or incorrect expectations), then it is time for a return.


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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5653952 - 01/31/13 09:53 AM

orlyandico,
I think if I had Jeremy's or Hilmi's mount, we wouldn't have to worry about seeing the sky. The glow from my head becoming a supernova would blot it out. Their frustration is understandable, & their patience is far greater than mine.

From the pic Jeremy posted of his worm, it is toast, & needs to be replaced, same for the coupler. There is no reason for it to fall apart or be mis-assembled.
My venerable G11 (ca'92?) was able to do 10-15 minute B/W SLIDE FILM exposures of M42 through an 8" F4 Vixen R200ss without smearing running on a Digital Drive System & a Sky Commander. I KNOW a G11 can perform & do it well.
Since Jeremy has found these problems I feel that he would be well within his rights to call up OPT or Losmandy & seek a replacement G11. At this point I would suspect everything with the mount.
Hilmi's mount is also a problem and there was yet another guy that got one recently, Charlie Bradshaw maybe. He lives sort of near me up in Belair Md. I was going to get together with him & see if we could sort his mount out but have lost touch with each other. That is 3 mounts that we know of that are possible from the same batch that have problems. I ownder if maybe a bad run has gotten through?
Jeremy & Hilmi what are the serial #'s of your mounts? It should be on the bottom of the head. If they're from the the same batch then that is a whole new ball of wax & Scott Needs to be brought into the loop. If it is indeed a bad run, then I'm sure that Scott will make things right.

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Re: Is this performance typical of G11? new [Re: Startraffic]
      #5654140 - 01/31/13 11:27 AM

The only hesitation I have with a return at this point is that the mount is not exactly as I received it. Since I had to modify the Ruland coupler after I broke a steel tap in it there is some "user damage." The same tracking issues existed before and after the coupler mod, but it's not as if the mount is exactly as it was when it arrived from OPT. I guess I should call and explain the situation and see what they say about it.

Another part of me still thinks there must be something I am doing wrong to make this happen. This isn't exactly a complex machine and there are a limited number of things that could cause this behavior. Here is where I am right now:

-It's not the worm (tried 2 of them)
-It's not the gearbox (tried 2)
-It's not the motor (tried 2)
-I don't think it's worm to wheel spacing, as I get the same results with it very snug and backed off as far as the OPW will allow. I haven't measured spacing though because I don't have a feeler gauge.
-I don't think it is the worm bearings, as I swapped RAand DEC bearings with no noticeable change
-It's not software (same results with Maxim and PHD)
-It's not the OAG (same results guiding straight through a scope)
-It's not the SBIG STi (same results using the STF-8300 as a guide
camera)
-It's not seeing related
-It's not RF interference (I've disconnected dew heaters, separated cables, etc. with no change)
-It's not cable drag (I can post pictures later when I get home, but it's a very clean setup)

Remaining possibilities:
-ST-4 port: I can't get Maxim or PHD to guide through the Gemini ASCOM driver. This may indicate a software or other computer problem. All tests so far have been conducted using the guider relays.
-RA needle bearings: The axis seems smooth. At first I thought it was sticking, but it is just slightly tighter than DEC.
-Worm wheel: possibly a problem, but I get similar results in all parts of the sky. Unless the wheel has a defect all the way around, I don't think this is it. I need to try swapping the wheels to eliminate the possibility.
-Ruland coupler mod: The worm and gearbox turn smoothly (to my perception) with the coupling installed as-is, but it is possible that the way I rigged it has induced some sort of deviation that happens to mimic the way it performed with loose hex screws as it came from OPT. Not likely, but possible.
-Tracking rate. It occurred to me this morning that maybe the timing of my RA tracking is very slightly off. This would cause the guider to constantly fight the rate in one direction, and occasionally it would not be able to keep up, no? Anyone know how I might be able to test that?

What am I missing? If it is defective, I would like to identify specifically what about it is defective. I know I've asked this before and I appreciate the responses, but this is stream-of-consciousness troubleshooting at this point. Any flaws in my reasoning or other thoughts about what on the mount or in the electronics could possibly be causing this problem?

Jeremy


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Re: Is this performance typical of G11? new [Re: contraf15]
      #5654228 - 01/31/13 12:21 PM

I did not see it listed but what is the voltage and amp supply running the mount. My G11 sometimes acts strange if I drop down to 12.3 volts.

Also, do you have access to another Gemini controller or you could find someone with a digital controller and motors to test to see if the mount works.


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Re: Is this performance typical of G11? new [Re: D_talley]
      #5654248 - 01/31/13 12:36 PM

Thanks for the suggestions Dwight. The mount showed 12.9 volts last night.

I'll have to look into trying the mount without Gemini. Maybe I can get someone in the Austin Astronomical Society to help me try it out next month if I don't get to the bottom of it before then.


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Re: Is this performance typical of G11? new [Re: contraf15]
      #5654271 - 01/31/13 12:51 PM

Jeremy,
I ran my G11 & run my HGM @ 15V through a power supply. When I ran the G11 with the Losmandy power supply (12VDC@5A) I did have some issues with Gemini shutting down during a 2 axis slew. I changed the PS & went to 15V & all is happy. I probably could've kept the original PS but I wanted to be able to feed a power distribution buss. The power supply I salvaged from a traffic signal controller, & has 1 variable 5-20VDC@20A, 1-9VDC@10A, & 1-5VDC@5A. More than sufficient for my needs & it has proven itself for at least 30Y-35rs of in the field service. It weighs 50# but it is bulletproof, stable, & rack mountable.

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Re: Is this performance typical of G11? new [Re: Startraffic]
      #5654286 - 01/31/13 01:01 PM Attachment (36 downloads)

OK, this is after my third rebuild of the mount. What did I do different? Well I swapped the RA & Dec gearboxes out, I lubricated the gearboxes with spray lubricant, I spent 10 minutes cleaning the tube where the axis shaft fits. No to see if this can be sustained.

Edit: This guided performance

Edited by Hilmi (01/31/13 01:06 PM)


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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5654299 - 01/31/13 01:11 PM

That graph is about right with maxim dl, PHD is another matter also have better settings.

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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5654322 - 01/31/13 01:25 PM

Hilmi,
Maybe a little bit of grit down in the threads or gearbox, slight mis-alignment of the bearings, better grip of the couplers, better penetration of the lube, a bad reversible hydro-dynamic-magito-blogowitz generator ()? I hated those kind of problems when I was a electronics tech, no discernible reason for the fix.

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Re: Is this performance typical of G11? new [Re: Startraffic]
      #5654332 - 01/31/13 01:31 PM Attachment (27 downloads)

I spoke too soon!

As soon as the guide star was lost the stars went all over the place. Could be a balance issue? Software bug? Looks to me like the tracking problem is solved, but another problem has been introduced


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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5654343 - 01/31/13 01:36 PM

Quote:

OK, this is after my third rebuild of the mount. What did I do different? Well I swapped the RA & Dec gearboxes out, I lubricated the gearboxes with spray lubricant, I spent 10 minutes cleaning the tube where the axis shaft fits. No to see if this can be sustained.

Edit: This guided performance




Looks good so far.


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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5654354 - 01/31/13 01:42 PM Attachment (35 downloads)

OK, here is a 10 minute exposure guided, slightly oval but good enough for me. This is unbinned on my STT-8300, 0.69 arcsecond per pixel.

Now I need to find the cause for the run away Axis. I will start by flashing the firmware on the mount to get a clean start.


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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5654510 - 01/31/13 03:18 PM

After diagnosing the problem I suspect the clutch is slipping. I must have contaminated it with grease while working on the mount

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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5655175 - 01/31/13 10:10 PM

Hilmi, that guiding graph is spectacular. Similar to my AP1200. Are the MaximDL settings correct for your scope/FL/CCD ? Your graph shows guiding at <1/3" RMS, which is pretty darn good.

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Re: Is this performance typical of G11? new [Re: korborh]
      #5655316 - 01/31/13 11:31 PM

ditto. was out with the Mach1 against last night. am usually only getting 0.6" rms with Maxim.

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Re: Is this performance typical of G11? new [Re: korborh]
      #5655423 - 02/01/13 01:10 AM

Quote:

Hilmi, that guiding graph is spectacular. Similar to my AP1200. Are the MaximDL settings correct for your scope/FL/CCD ? Your graph shows guiding at <1/3" RMS, which is pretty darn good.




Can't be sure about accuracy of numbers as my OAG has a built in reducer which basically changes the focal length compared to the numbers I entered in the settings. By the time the clouds rolled in last night and I gave up on testing I had managed to consistently take 10 minute exposures. I am getting my pier today as I have finally found some people crazy enough to lift it from my parents house and bring it to my house. Thats maybe 100 kg down 3 floors then up 3 floors again. I suspect guiding performance will improve some more with a stable platform. The pier will also allow me to better route the cables thus reducing cable drag


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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5656489 - 02/01/13 02:37 PM

Hilmi,
That looks great to me. It doesn't take much grease on the pads to make them slip. DAMHIKT
How is the STT-8300 work for you? I've been drooling for months but maybe by this summer I can afford it. I just got the HGM & depleted my Astro budget until then unless I can get my G11 sold. THAT would help a bunch.

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Re: Is this performance typical of G11? new [Re: Startraffic]
      #5657433 - 02/02/13 12:09 AM Attachment (17 downloads)

Hilmi congrats on the improvement! I tried my setup tonight with a completely different computer running all of the software. That allowed me to guide throug ASCOM instead of the ST-4 port (no idea why that won't work on my other computer). My graph is below. For reference, this is the STi guiding through SBIG OAG. Scope focal length is 952mm. With the 0.7x reduction of the OAG, the scale is 2.29"/pixel. The graph shows deviation in pixels, so I'm still seeing these crazy >10" jumps. I have now eliminated the computer, guide port, and software as possible causes.

How did you clean the RA axis? I'd appreciate any specifics you can provide.

Jeremy


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Re: Is this performance typical of G11? new [Re: contraf15]
      #5657479 - 02/02/13 01:09 AM

Startraffic,

So far the STT is working out really well for me, but I need to be careful with cable management. The camera has the following connections:
1) Power
2) USB
3) Filter wheel cable (could have been made shorter, I don't know why it's a mile long)
4) HDMI cable to control OAG camera (again, could have been shorter with low profile)
5) ST4 guide cable (optional, but unless your mount doesn't guide well through pulse guide, I don't see the point)

Now imagine how many possible points of snagging that provides you with!

Jeremy,

After stripping the whole mount. I sprayed tons CRC contact cleaner into the hole where the axis shaft fits. then I bunched up some tissue paper and shoved it in there with a rod. When it got to the bearings I would twist it around to clear the bearings. I did this around 5 times for each axis. Then I regreased all bearings with some fresh grease. Check there are no bits of tissue paper left behind when done.

I used the mount successfully to image last night but near the end of the session I started to hear some screeching sounds from RA axis. I think that the gear meshing was too tight and these new high torque motors just wont stall! So I am going to strip the RA worm gear again next weekend to check for damage and clean out any excessive muck that might have been formed from the brass getting ground due to forced rotation. I'll also check, maybe the grease I put was not enough. Either way, my mount has never worked this well since I purchased it.

I am finding the declination axis is misbehaving now, which I did not have before. It is bouncing back and forth in a sinusoidal fashion and the problem is more prominent when pointed at certain parts of the sky. I suspect this is a combination of backlash setting and a balance issue.

Edited by Hilmi (02/02/13 01:10 AM)


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Re: Is this performance typical of G11? new [Re: Startraffic]
      #5657710 - 02/02/13 08:49 AM

StarTraffic,

My G11 is working fine. My problem was that both the RA and DEC worms were too tightly adjusted at the factory, resulting in binding. I took both worms off and inspected and adjusted couplers and worms. I now get very good and smooth performance from the mount (about +- 5" unguided PE).

I took Ed Thomas' advice and adjusted the worms, on the bench, while slewing through the entire range.

Now, if I could as easily fix my poor seeing...

Best regards,

Charlie B


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Re: Is this performance typical of G11? new [Re: contraf15]
      #5658049 - 02/02/13 12:31 PM

Quote:

Hilmi congrats on the improvement! I tried my setup tonight with a completely different computer running all of the software. That allowed me to guide throug ASCOM instead of the ST-4 port (no idea why that won't work on my other computer). My graph is below. For reference, this is the STi guiding through SBIG OAG. Scope focal length is 952mm. With the 0.7x reduction of the OAG, the scale is 2.29"/pixel. The graph shows deviation in pixels, so I'm still seeing these crazy >10" jumps. I have now eliminated the computer, guide port, and software as possible causes.

How did you clean the RA axis? I'd appreciate any specifics you can provide.

Jeremy




I'm not great on these graphs, but the error looks random. That suggests that the mount is more or less "dirty" and that is causing most of the error. There can be "grit" on the worm or in the worm and/or axis bearings causing problems like this.

Where this mount not new, the first thing I would do is a good cleanout of the mount. The G11 does not require a lot in the way of tuning beyond the worm spacing, but it does require periodic maintenance. The axis bearings are open needle roller bearings that can get dirty over time. While they can be cleaned in place to some extent, it is best to remove them to really get them cleaned out well. There isn't anything you can do with the worm bearings except replace them.


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Re: Is this performance typical of G11? new [Re: EFT]
      #5660042 - 02/03/13 01:58 PM

Today I am doing the most brutal test I could think of for my repairs of the mount. I'm doing 20 minute exposures guided, but with wind that is occasionally gusting up to 18 Km/h. The mount is housed in a roll off roof observatory, so it's not getting much wind protection.

I'm just starting the test now, but I did a short trial of 1 minute during gusts and the stars where perfectly round. So I guess if it can keep the stars ROUGHLY round in such gusty winds at 20 minutes an exposure, I can officially declare all mechanical faults fixed.

This test is not fair considering the conditions, but honestly, I don't have to wake up early for work tomorrow and there has been rain in the morning which means transparency is great. I figured I might as well do some random experimentation to see how well my repairs have gone.


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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5660070 - 02/03/13 02:16 PM

Quote:

Today I am doing the most brutal test I could think of for my repairs of the mount. I'm doing 20 minute exposures guided, but with wind that is occasionally gusting up to 18 Km/h. The mount is housed in a roll off roof observatory, so it's not getting much wind protection.

I'm just starting the test now, but I did a short trial of 1 minute during gusts and the stars where perfectly round. So I guess if it can keep the stars ROUGHLY round in such gusty winds at 20 minutes an exposure, I can officially declare all mechanical faults fixed.

This test is not fair considering the conditions, but honestly, I don't have to wake up early for work tomorrow and there has been rain in the morning which means transparency is great. I figured I might as well do some random experimentation to see how well my repairs have gone.




Excellent! It's good to hear that it is working now.


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Hilmi
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Re: Is this performance typical of G11? new [Re: EFT]
      #5660073 - 02/03/13 02:18 PM Attachment (40 downloads)

OK, What do you all think? Should I leave it as is or should I continue messing with the mount? Up down direction in the picture is Dec axis. left right is RA Axis. This is a single 20 minute sub

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contraf15
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5660085 - 02/03/13 02:22 PM

Wow, that looks great for 20 minutes! I wish I could get mine doing that.

I'm getting ready to completely strip it down, clean it, and regrease.

Does anyone have a tip for getting the needle bearings out of the axes?

Jeremy


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Hilmi
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5660089 - 02/03/13 02:24 PM Attachment (34 downloads)

Here is a 1:1 scale capture of the worst star in the image. This is scale according to Pinpoint LE is 1.38"/pixel

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Hilmi
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5660093 - 02/03/13 02:27 PM

Jeremy, I couldnt get mine out. I just cleaned them in place. I have no experience removing bearings. I suspect my Declination axis worm wheel(not worm gear) bearing is in ill health as it was binding when I looked at it while cleaning, but for the life of me I couldn't see how it could be removed. It fits so snugly and I just cant see how one would pull it out. No more Wahiba sand dunes trips for this mount.

Edited by Hilmi (02/03/13 02:28 PM)


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pfile
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5660115 - 02/03/13 02:39 PM

is that star on the optical center? you should probably look at stars in the center just to eliminate coma or curvature as the cause for elongation.

i actually have some 20min subs with my G11/G2 that have almost perfectly round stars. but they were taken with a 5nm Ha filter, which i think helps. the best ones were taken with an AO-8 running.


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Hilmi
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Re: Is this performance typical of G11? new [Re: pfile]
      #5660128 - 02/03/13 02:45 PM

I thought the LX200R was coma free! Anyway, that star is from 1/4 of the way from the right side of the image. Some of the stars are actually perfectly round. Maybe my camera is not exactly perpendicular to the path of the light. Might be tilted to one side. The stars on the left of the image are definitely more round than the ones on the right. Regardless, I am happy considering it's windy. I guess the true test will be when the wind dies down. I'm coming back from my biweekly business trips Next Thursday, I hope by then the wind would have died down then I can have a fair test. The image was taken with the Baader Ha filter that came with my camera. Can't recall the specs. I don't want to go near the mount while its imaging to rummage through my equipment to find the cases and check the specs.

Next week I am also getting my pier adapter. And the mount should be mounted on a solid steel 6" diameter pier.

Edited by Hilmi (02/03/13 02:48 PM)


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EFT
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5660276 - 02/03/13 04:14 PM

Quote:

Wow, that looks great for 20 minutes! I wish I could get mine doing that.

I'm getting ready to completely strip it down, clean it, and regrease.

Does anyone have a tip for getting the needle bearings out of the axes?

Jeremy




Take a long metal rod or wood dowel and from the other end, tap around the circumference of the bearing. Don't hit it too hard lest you damage the bearing. They should slowly move out of the housing. To replace them tap them back in place and then use a socket from a wrench set that it just smaller than the bearing diameter to tap it all the way back down.


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orlyandico
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Re: Is this performance typical of G11? new [Re: EFT]
      #5660756 - 02/03/13 09:20 PM

Hilmi, could be mirror tilt as well. Don't know how effective the mirror locks are on the LX200R.

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contraf15
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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5667952 - 02/07/13 10:07 PM

Another update...I completely disassembled the RA axis and cleaned all of the bearings, the worm wheel, and the worm with acetone. I added a third needle bearing to the scope end of the axis as well. Regreased everything with Super Lube and put it all back together. I ordered a new Ruland coupler and gearbox (just in case) from Losmandy and they shipped out today (turns out they do sell the couplers, they just aren't listed on the website).

I saw on another thread something about a batch of bad worms from late last year, so I emailed Scott a picture of the original RA worm and asked if he could confirm whether there was a known problem with some of the worms. He responded within a couple of hours, and though he didn't confirm whether there was a bad batch of worms he did promise to ship me a new worm and bearings tomorrow.

I'll update once I get the new worm installed. Even though the mount is brand new, the cleaning & regreasing of the needle and thrust bearings made the RA axis turn noticeably smoother with the clutch loosened.

I'm keeping my fingers crossed...


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Hilmi
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5672438 - 02/10/13 02:17 PM Attachment (18 downloads)

I let CCD autopilot optimize my guiding parameters Resisting throwing your gear out the window and keeping on at it is eventually worth it if you have the patience. The numbers don't look as good as the previous post, but everything is very consistent now. No sudden odd guiding behavior. So now I am getting super round stars

Edited by Hilmi (02/10/13 02:22 PM)


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Raginar
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5672488 - 02/10/13 02:40 PM

Hilmi, what version CCDAP are you using that it automatically optimizes your guiding settings? Do you have the 'Pro' version?

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Hilmi
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Re: Is this performance typical of G11? new [Re: Raginar]
      #5672507 - 02/10/13 02:47 PM

Yep, thats the one I have. You put in your focal length. Dont trust your calculations, I found out that my F6.2 reducer was working at f8 because of the spacing etc... I used plate solve from both TheSky X and MaximDL to confirm this. After you put in the specs of your CCD (pixel size) and guide CCD and your focal length you ask it to recommend settings and then tell it to apply to MaximDL.

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Raginar
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5673054 - 02/10/13 08:57 PM

Do you have 5?

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contraf15
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5680514 - 02/15/13 12:59 AM Attachment (24 downloads)

Well I'm pleased to report that the new worm and bearings Scott sent are installed, and I completely stripped the mount and regreased it with SuperLube. While I was at it I made my own clutch knob mods because I got tired of waiting for them to be in stock somewhere. The results look good so far. This picture is a screen grab (sorry, probably hard to read) showing <1 pixel deviations now in RA. The image in the back is a single 10 minute Ha frame of the Alnitak region I took tonight as a test shot. Round stars! No halos! Would have been nice if all this equipment had worked out of the box...but I guess that's what you pay for if you get a Mach 1. My next order of business will be to see if I can get Losmandy to fix or replace my G11 hand controller, which has frozen up so much that I have abandoned it for computer control of the mount through the web interface and ASCOM.

But the biggest issue, the heinous RA tracking, appears to be getting better. Maybe now I can get some sleep.

Jeremy


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orlyandico
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5680535 - 02/15/13 01:20 AM

That level of guiding performance is very close to what I'm currently getting with my Mach1.... So a very good result.

Of course the difference is the Mach1 did that out of the box...


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neilson
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Re: Is this performance typical of G11? new [Re: orlyandico]
      #5680576 - 02/15/13 02:13 AM

Hi Jeremy,
My new mount is plagued with tracking issues. My RA is tracking slow. I am having to weight the West side heavy but that only works for a short time then it slows back down. I would be interested to know what the Periodic Error (PE) of your new worm is. I just got my replacement worm and my results are not very good but once my tracking problems are fixed I expect better results.

Thats a great looking image.

neilson


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contraf15
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Re: Is this performance typical of G11? new [Re: neilson]
      #5680753 - 02/15/13 07:04 AM

Hi Neilson,

As I mentioned on the Gemini 2 forum, I am seeing the same gremlins with slow RA tracking unguided. Last night I re-flashed the firmware and was able to get a good guiding calibration, but I'm not ready to declare the issue solved. It did this before and then started tracking at about half normal sidereal rate, that's an issue I haven't even mentioned in this thread yet. Maybe a Mach 1 would have been the better answer from the start. I know my wife hasn't appreciated all this time spent troubleshooting....

Jeremy


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neilson
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5680909 - 02/15/13 09:05 AM

Hi Jeremy,
I'm not happy about all the time I have wasted on this myself. Last night I was able to get it to track correctly for a short time unguided. Then the gremlins came back and messed it up again.
A Mach I would be nice, but I have to settle for a G-11. I never thought I would end up using the phrase "settle for" when refering to my new G-11.

The best I had been able to get the new worm Scott sent me to track was 15 arc.sec. Then I switched out the gear box and I got a few runs of 9.5 arc sec of PE total. But these runs weren't as smooth as the 15 arc sec. runs.

I have been getting a high spike in the frequency spectrum (using PecPrep) every run at 31.9 Worm Spur Gear. I am guessing that indicates I need to try a different gearbox. Does that sound right?

neilson


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gdd
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Re: Is this performance typical of G11? new [Re: neilson]
      #5681583 - 02/15/13 01:59 PM

Hi Neilson,
Yes, the 31.9 sec spike is caused by the worm spur gear. Replacing the gearbox can fix that. Another way is to use PEC by defining a custom mount and with an 8 minute period (180 tooth worm) and doubling the number of encoder positions.

Gale


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neilson
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Re: Is this performance typical of G11? new [Re: gdd]
      #5681702 - 02/15/13 02:46 PM

Hi Gale,
Thank you for verifying the worm spike gear is the gear box on the G-11 mount.

I didnt understand exactly what you meant by defining a custom mount or the 8 minute worm. The G11 has a 4 minute worm though.

Could you explain further

Thank you
neilson


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gdd
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Re: Is this performance typical of G11? new [Re: neilson]
      #5681771 - 02/15/13 03:22 PM

The 32 second spur gear period repeats 7.5 times every 4 minute worm gear period. This is not an integral number of times so standard PEC using a 4 minute worm period cannot remove it. However, Gemini allows a custom mount to be defined for the worm/gearbox combined system which has a 8 minute period where the 32 second harmonic repeats times. Defining a custom mount with a 180 worm wheel tricks Gemini into creating a PEC curve that repeats every 8 minutes. Since the motor must turn twice as many revolutions in 8 minutes to retain the same rotational rate, the number of encoder steps entered into Gemini must be doubled. This only needs to be done for the RA.

Gale


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neilson
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Re: Is this performance typical of G11? new [Re: gdd]
      #5682126 - 02/15/13 06:37 PM

Hi Gale,
Wow, That is a really neat trick. I thank you for giving me this information. I will definately try this when I record my PEC curve. It should help me a lot.Thank you.

neilson


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contraf15
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Reged: 10/24/09

Re: Is this performance typical of G11? new [Re: neilson]
      #5686049 - 02/17/13 09:52 PM

Nothing but clouds here tonight so I spent some time on my gearboxes. I have some interesting observations.

I have three gearboxes (one spare) so I decided to disassemble the spare and replace the plastic tabs that hold it together with some precision flat head screws. I took it completely apart, which wasn't hard since there are only four pieces. I cleaned out all of the old grease (which is really new grease since the mount is brand new), then I painstakingly cleaned every tooth on each cog. I regreased everything with Super Lube (that is now the only kind of grease anywhere on the mount) and put it back together with the screws.

The gearbox seemed to turn much smoother than before, so I did the same thing to the other two. Then I installed the modified gearboxes on the mount.

When I turned on the mount to slew through the range of motion on each axis, I initially thought I had done something wrong. The slews were SIGNIFICANTLY quieter than they had been before I did this. I mean it didn't even sound like the same mount. I'll have to check the PE and tracking next time I get a clear sky, but I suspect that if the gearboxes were producing that much audible noise they were also introducing a fair amount of mechanical noise. I wish I had recorded before and after audio clips of this thing, it was that much of a change. Stunning.

Jeremy


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Hilmi
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5686327 - 02/18/13 01:12 AM

Jeremy,

Do you mind posting a picture of how you pried apart the gearbox? I tried to open mine but I felt like I was going to break something!


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contraf15
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5686629 - 02/18/13 09:06 AM

Hi Hilmi,

I followed the instructions (with pictures) here:

http://gemini-2.com/Gearbox_mod.php

The only difference is that I drilled all three holes and pulled it apart before I installed any screws. In the instructions he recommends completely installing one screw at a time, but if your objective is to clean it out that wouldn't work. It comes apart immediately after you drill the holes. The hardest part for me was finding screws small enough for this job. I had to order them.

Jeremy


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neilson
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5686831 - 02/18/13 11:32 AM

Hi Jeremy,
My new worm is giving me a spike at 31.9 in the frequency spectrum of Prcprep. Its the worm spur gear. I have a spare gear box that I grabbed the motor buy mistake and it poped the gearbox apart. So yesterday I decided to clean all the grease out and put super lube. I cleaned the gears teeth with a toothbrush and alcohol. I thought of drilling holes and putting screws but instead I took the easy way and used J-B weld epoxy. And of corse the weather went bad so I couldn't test it last night.
Before I put the motor on I had sprayed some silicone spray in the hole in gear box. I think I washed the grease off the gears. After reading your post I wish I would have used screws. I am glad you wrote that you drilled the holes with the cover on. I think I will take it apart again and regrease it. I'm going to drill holes and use screws like you did. Thats great advice. Currently I have long plastic cable ties wrapped over the motor and gear box so the gear box doesn't get popped apart by accident again. But if the gearbox is screwed together it wont pop apart. cool.

neilson


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neilson
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Re: Is this performance typical of G11? new [Re: neilson]
      #5687270 - 02/18/13 04:31 PM

Hi Jeremy,
I couldnt get my RA gear box apart I had J-B welded together. I used a bent piece of wire to put grease in the gearbox gears. Now the RA is very quiet, I like that.

I decided to try and put some grease on the DEC gearbox. When I would turn the shaft it was hard then easy alternating. I sprayed silicone but nothing worked. I decided to put the gearbox I had removed from the RA before onto the DEC.

Then I was unplugging the wire from the RA without holding the motor and the gearbox came apart. So I cleaned it up and greased the gears. I drilled 3 holes and screwed it together. Now I dont need the cable ties because the motor is solid. very solid, and very quiet.

The clouds have cleared so I plan to test it tonight.
Thanks for the advice on the gearbox Jeremy. Otherwise I would have never found the bad gearbox on my DEC drive. I am experiencing problems with my DEC and I'm hoping this resolves them.

Neilson


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neilson
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Re: Is this performance typical of G11? new [Re: neilson]
      #5688219 - 02/19/13 02:14 AM

Hi Everyone,
I was able to test my mounts gearbox overhaul for 6 hours tonight. I did many PE tests. I noticed a number of frequency spikes in Pecpreps frequency spectrum that weren't there before. The 31.9 worm spur gear spike is still there. All the new spikes are different worm harmonics (what ever that is).

But dispite those readings the PE graph is alot smoother and my PE even went down a little. All that plus its quieter and sturdier. I think your ideal is a winner Jeremy. Thanks.

I had swapped out the DEC gearbox but this one is noisy and not as smooth in my PE graph. I am going to grease it up tomorrow. At times the Dec would stop slewing and the RA is so quiet I didn't realize it was still moving.


Neilson


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contraf15
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Reged: 10/24/09

Re: Is this performance typical of G11? new [Re: neilson]
      #5709739 - 03/02/13 11:24 PM Attachment (24 downloads)

Just an update - With the new worm, the overhauled gearboxes, the addition of a 3rd needle bearing on the RA axis, a puck to extend the DEC axis an additional 2 inches for motor clearance, a 12" pier extension, and cleaning and regreasing every part of the mount I am finally getting the kind of tracking I thought I would with this mount. It wasn't easy and it took a ridiculous investment of time and frustration over the last two months, but as the picture shows I am now consistently getting sub arc-second RMS tracking with it. If I had it to do over I would get a Mach 1. I have spent almost as much money, but if you add what I have spent in time there is no comparison. The only good thing about all of this is what I have learned about mounts...it's been a good education, and I now literally know every screw, bearing, and component of this thing plus what each does to performance.

I still haven't measured PE, I'll try to get that done soon but I don't intend to take unguided shots so I'm not overly concerned.

One last story to finish out this saga. I had the entire setup assembled in the backyard earlier this week under a Tele Gizmos 365 cover (mount, OTA, camera, filters, etc). All told there was around $13,000 of equipment back there. I had no idea we were forecast to get a massive windstorm in Texas...

The scope cover acted like a giant sail as wide as the length of my 127mm OTA (about 4 feet), which just happened to be oriented perpendicular to the prevailing wind direction. 50 knots of wind took the entire setup over while I was at work and laid it flat on its side. The DEC gearbox was crushed, the posts that hold the DEC motor and gearbox asembly to the mount bent about 30 degrees, and the camera detached from the OTA by popping the threads on the field flattener. Fortunately I had a spare gearbox that I had already overhauled. I bent the posts back, put on the new gearbox, fixed the field flattener, and everything is as good as new (the picture below is from tonight). Morals of the story: 1) knowing the mount can be very useful, 2) don't leave expensive equipment set up outside (or at least check the forecast better than I did), and 3) personal property insurance is probably a good idea once you get above a certain threshold with this stuff!

Jeremy


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Hilmi
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5709785 - 03/03/13 12:15 AM

Is that RMS reading set up in pixels or arc seconds?

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contraf15
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5709960 - 03/03/13 05:20 AM

It is pixels in the picture. In arcsec, it was .28 to .45 last night.

Jeremy


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Hilmi
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Re: Is this performance typical of G11? new [Re: contraf15]
      #5709964 - 03/03/13 05:25 AM

That's around what I am getting out of mine now. If only I could get the DEC backlash resolved then it would be pretty much perfect (not taking into account the effort expended).

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contraf15
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Re: Is this performance typical of G11? new [Re: Hilmi]
      #5709967 - 03/03/13 05:33 AM

I'm sure you've already tried this, but I found that nearly all of my dec backlash was due to the spacing of the blocks holding the dec worm and not the mesh of the worm with the wheel. When I tightened the blocks, I did so while squeezing them together to eliminate any possibility of the worm moving laterally between the bearings. The dec backlash is negligible now (with the worm/wheel spacing backed off just slightly from as close as I can get it).

Jeremy


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