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Equipment Discussions >> Mounts

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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
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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Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
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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Reged: 08/10/09

Loc: Singapore
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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Jared
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Reged: 10/11/05

Loc: Piedmont, California, U.S.
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
Pooh-Bah


Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
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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Reged: 08/10/09

Loc: Singapore
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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Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
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
member


Reged: 10/24/09

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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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
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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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Is this performance typical of G11? new [Re: Hilmi]
      #5639131 - 01/23/13 03:47 PM Attachment (24 downloads)

The frequency analysis screen

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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Is this performance typical of G11? new [Re: Hilmi]
      #5639134 - 01/23/13 03:49 PM Attachment (21 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
Pooh-Bah


Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
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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Reged: 08/10/09

Loc: Singapore
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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NJScope
sage
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Reged: 03/08/04

Loc: NJ
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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Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
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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pfile
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Reged: 06/14/09

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
member


Reged: 10/24/09

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
member


Reged: 10/24/09

Re: Is this performance typical of G11? new [Re: contraf15]
      #5649554 - 01/29/13 12:17 AM Attachment (47 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
member


Reged: 10/24/09

Re: Is this performance typical of G11? new [Re: contraf15]
      #5649570 - 01/29/13 12:35 AM Attachment (29 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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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
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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