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Walking on the Moon

Overhauling my G11 for the new season...


AMcD
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I have owned my much loved Losmandy G11 for nearly twenty years and, beyond adjusting the original (and very annoying) two piece worm blocks, have not serviced it during that time.  In that state it regularly achieved a sub-arc second RMS in good seeing, albeit usually in the 0.60 to 0.80 range.  I have now purchased one piece work blocks for each axis, new Losmandy high torque motors, new clutch pads and a 4" pier extender to push the OTA slightly higher above the ROR observatory walls.  I have begun by stripping down the mount and am about to commence cleaning and re-greasing...

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Hopefully you did relubricate it at some point in those 20 years! I tend to relubricate my G11 every 2 or 3 years without taking the worms off by pressing a toothbrush soaked in degreaser against the worm as it is turning, and then leave it to dry, then regrease the worm and gear wheel all the way around. Mine still has the two piece worms, and I'd definitely be interested if the one piece worm makes a difference.

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19 minutes ago, iantaylor2uk said:

Hopefully you did relubricate it at some point in those 20 years! I tend to relubricate my G11 every 2 or 3 years without taking the worms off by pressing a toothbrush soaked in degreaser against the worm as it is turning, and then leave it to dry, then regrease the worm and gear wheel all the way around. Mine still has the two piece worms, and I'd definitely be interested if the one piece worm makes a difference.

To my shame, I only re-greased the worms once, when I adjusted the worm blocks three or so years ago.  I regret to say I have never re-greased the needle bearings or the thrust bearings. 

I will let you know how I get on with the one piece worm blocks.  In circumstances where I was pretty happy with my guiding overall, I debated for a long time whether to make the change.  There is danger in listening to the Siren song of a lower RMS...😂

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4 hours ago, iantaylor2uk said:

and I'd definitely be interested if the one piece worm makes a difference.

I think at the very least it must make adjusting the worm mesh a lot easier as you don’t have to worry about keeping the bearings aligned whilst also applying some preload whilst adjusting the mesh whilst tightening the fixing bolts- all at the same time! From my understanding the typical 76sec PE comes from pinching of the worm bearings, probably from misalignment during this adjustment process, so they should help a lot. I’m still using the original ss worms and individual bearing blocks but these are tempting 

Mark

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On 29/08/2022 at 17:46, markse68 said:

I think at the very least it must make adjusting the worm mesh a lot easier as you don’t have to worry about keeping the bearings aligned whilst also applying some preload whilst adjusting the mesh whilst tightening the fixing bolts- all at the same time! From my understanding the typical 76sec PE comes from pinching of the worm bearings, probably from misalignment during this adjustment process, so they should help a lot. I’m still using the original ss worms and individual bearing blocks but these are tempting 

Mark

I put the new parts on yesterday.  The cleaning and re-greasing and installation of the new parts was relatively straightforward, assisted in large measure by the YouTube videos from Losmandy.

B32A4A28-56D8-4CAB-AD1B-CBCDE13D924D.thumb.jpeg.91b4ff20e6072567a5adf0baced435be.jpeg

Serendipitously, the skies were clear and I was able to put the mount back in the observatory, polar align it and begin testing the guiding.  Even without any fine adjustment, the guiding was variable but sub-arc second for significant periods (the seeing was poor), so I am hopeful that I will see an appreciable improvement over the previous configuration as I make final fine adjustments.  The adjustment of the worms is a lot easier with the one piece blocks!

I can no longer see the 76 second PE on the PHD2 analysis graph as matters stand.  I am however, getting very high levels of declination backlash at the moment (although had failed to set TVC to 0 in the Gemini).  I have sent my guide logs to the PHD Open forum for any guidance the experts might have on how to better ‘dial in’ the new parts.

The new high torque motors are quite loud (there is a Losmandy video that suggests how that might be addressed) but they move my 35lbs of equipment around like it is not there.

Overall, my initial impression is a positive one.😀

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Sounds good - what guide camera are you using? - I previously used a ZWO 120MM mini mono camera but recently upgraded to a ZWO 290MM mini mono - with the new camera I use in bin2 mode and it is much more sensitive and there are many more stars in the FOV for the multi-star guiding. If you have high DEC backlash maybe the spacing between the worm and worm gear needs adjustment. I think there has been some discussion of this issue on the Losmandy forums. The view there, as I understand it, is that the value found by PHD2 is not that representative, and once you start guiding it becomes less of an issue. I saw values for DEC backlash as low as 0.9 seconds and as high as 3 seconds on my G11 and it never seemed to make much difference to the guiding. 

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1 hour ago, iantaylor2uk said:

Sounds good - what guide camera are you using? - I previously used a ZWO 120MM mini mono camera but recently upgraded to a ZWO 290MM mini mono - with the new camera I use in bin2 mode and it is much more sensitive and there are many more stars in the FOV for the multi-star guiding. If you have high DEC backlash maybe the spacing between the worm and worm gear needs adjustment. I think there has been some discussion of this issue on the Losmandy forums. The view there, as I understand it, is that the value found by PHD2 is not that representative, and once you start guiding it becomes less of an issue. I saw values for DEC backlash as low as 0.9 seconds and as high as 3 seconds on my G11 and it never seemed to make much difference to the guiding. 

I am using the ZWO120MM mini mono at present.  I use a 50mm guidescope at present but I guess the added sensitivity of the 290MM might also make the use of an OAG easier.   I will look at the DEC again tonight as it is due to be clear.  Now I have it polar aligned and functioning I can look to the finer adjustments.

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1 hour ago, markse68 said:

Are these the new spring loaded worms @AMcD

No, they are the standard ‘new’ OPWs.  I must confess to being a bit confused about the current position on the spring-loaded worms.  I know they come as standard on the new mounts but I cannot see a way to order them as an upgrade.  The Losmandy website says ‘pictures coming soon’ but has done so now for some time. I think the OPWs can be retrofitted with them but, as I say, at the moment they do not seem to be sold as an after market accessory.

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54 minutes ago, AMcD said:

No, they are the standard ‘new’ OPWs.  I must confess to being a bit confused about the current position on the spring-loaded worms.  I know they come as standard on the new mounts but I cannot see a way to order them as an upgrade.  The Losmandy website says ‘pictures coming soon’ but has done so now for some time. I think the OPWs can be retrofitted with them but, as I say, at the moment they do not seem to be sold as an after market accessory.

From posts on the Losmandy Hackers group they don’t seem very popular anyway so you may not have missed much. What is the thumb knob at the end of the bearing block for? Is that a way to dial in the mesh?

Mark

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3 hours ago, markse68 said:

From posts on the Losmandy Hackers group they don’t seem very popular anyway so you may not have missed much. What is the thumb knob at the end of the bearing block for? Is that a way to dial in the mesh?

Mark

Yes, the thumb knob assists in adjusting the distance from worm to the mesh when the bolts holding the OPW to the mount are loosened.  I too have read mixed reviews about the spring loaded worm and Losmandy certainly appear to have vacillated when it comes to making it available as an after market upgrade.  I will see how I get on with these new bits before going any further 😀 

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I think Losmandy were initially going to offer a spring loaded worm upgrade kit but because their solution relies on
some machining to the mount they must have went off the idea.  They said in a youtube stream (I asked a question re it)
that they will sell the bits to do the spring loaded modification but it would be up to the purchaser
to figure it out how to fit it.

Edited by SpookyKatt
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20 hours ago, iantaylor2uk said:

Sounds good - what guide camera are you using? - I previously used a ZWO 120MM mini mono camera but recently upgraded to a ZWO 290MM mini mono - with the new camera I use in bin2 mode and it is much more sensitive and there are many more stars in the FOV for the multi-star guiding. If you have high DEC backlash maybe the spacing between the worm and worm gear needs adjustment. I think there has been some discussion of this issue on the Losmandy forums. The view there, as I understand it, is that the value found by PHD2 is not that representative, and once you start guiding it becomes less of an issue. I saw values for DEC backlash as low as 0.9 seconds and as high as 3 seconds on my G11 and it never seemed to make much difference to the guiding. 

Managed to complete adjustment and testing last night using the Calibration and Guiding Assistant functions on PHD2.  I adjusted the meshing on the DEC axis, which appears to have helped considerably with the backlash (or at least with PHD2's view that there was a difficulty with DEC backlash).  I also loosened, pinched and re-tightened the worm blocks on the RA axis as I noted a small amount of side-to-side play in the RA worm.  Having completed the PHD2 process and the adjustments, I achieved pretty good guiding over the course of the test image I took, with the RMS ranging between 0.45 and 0.60 for most of the night, with peaks from 0.80 to 0.95 on occasion.   That is better than I have achieved previously.  My test image of 5 hours of 300sec integrations on NGC6888 appears to show nice round stars, which I suspect is all that matters at the end of the day 😃  Overall, I am pretty happy with the new parts...

 

NGC6888_LF_5hrs_01_09.22_ProcessedSGL2.thumb.png.c3e031abac65e83520d4248195b4d050.png

 

 

Edited by AMcD
Corrected spelling and grammar
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  • 1 month later...
On 31/08/2022 at 06:51, AMcD said:

I put the new parts on yesterday.  The cleaning and re-greasing and installation of the new parts was relatively straightforward, assisted in large measure by the YouTube videos from Losmandy.

B32A4A28-56D8-4CAB-AD1B-CBCDE13D924D.thumb.jpeg.91b4ff20e6072567a5adf0baced435be.jpeg

Serendipitously, the skies were clear and I was able to put the mount back in the observatory, polar align it and begin testing the guiding.  Even without any fine adjustment, the guiding was variable but sub-arc second for significant periods (the seeing was poor), so I am hopeful that I will see an appreciable improvement over the previous configuration as I make final fine adjustments.  The adjustment of the worms is a lot easier with the one piece blocks!

I can no longer see the 76 second PE on the PHD2 analysis graph as matters stand.  I am however, getting very high levels of declination backlash at the moment (although had failed to set TVC to 0 in the Gemini).  I have sent my guide logs to the PHD Open forum for any guidance the experts might have on how to better ‘dial in’ the new parts.

The new high torque motors are quite loud (there is a Losmandy video that suggests how that might be addressed) but they move my 35lbs of equipment around like it is not there.

Overall, my initial impression is a positive one.😀

Okay, my new motors are loud also and I did look at the video but have not addressed the issue yet. I believe some screws are a bit too tight. The upgrade was well worth it.

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