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G11 Guding PHD2 rms number High G1

 

Recently Purchased a used G11 with G1 controller


I gave up on using the RS232 interface....it will connect at times others it will not,.

Tried 2 different Apdapters USB to 9 pin, Cable is sound, At the point were I probably

will trade in for a G2. Cmos battery replaced. Was reading 2.75vdc now 3.25vdc

Cleaned all connections with contact cleaner. Windows 7


I have owned many mounts and have stripped down and tuned many, sucessfully


I have been working with the G11 for 1 weeks trying to match RMS phd2 spec of <.9 rms Total

of my former Sirius mount with belt drive with the same payload of 15lbs


Payload 15lbs

guide scope 50mm SSAG Camera PHD2

Polar Alignment within 2 arc min of pole set by drift PHD2

Using ST-4 port for guiding since rs232 flakey,,,


What have I done.,


Put bolts on gear box cases since 2 of the plastic rivets were broken and causing flexure

with the motor to gearbox . Did both RA and Dec Gears look fine visually


Adjusted worms on both RA and Dec so virtually no backlash or end play exist ( a small bit of endplay ovison)

Ovision OPW gear BTW on RA. both work freely by hand but no binding. I used a feeler guage to

set worm spacings on RA and Dec. .030 ra .012 dec


Checked large RA ring gear for any damage....looks great,.


A bit east heavy RA ....


Other than thrust bearings not sure what is left to do to improve guiding performance.

I ran 3 worm cycles guiding output disabled and get about 8 to 10 PTPeak PE on the RA


Number I get PHD2


1.35 RMS RA

.87? ?RMS Dec


Ill post files in my folder soon?


Thanks for any help


Greg
 

Forgot to mention G11 is pier mounted
 

Hi Greg,

A couple of thoughts on your process. You are not likely to get very low tracking error numbers with the stainless steel worms, you must have brass worms for the best precision and tracking. You must have some worm gear backlash between the worm gear and the worm wheel on RA, DEC is often times better with a bit less but in any case you cannot just set the backlash in the heat of the day and expect the backlash to remain the same. As the air temps drop so will the worm gear clearance, set your worm gear backlash in the COLD.?

Also none of the felt backlash can come from movement of the worm gear on the worm gear axis, it MUST have s slight preload, there can be no freedom between the gearbox output and worm gear input shaft, the coupler must be tight and free of any play. Check your worm gears for end play, it should be zero or darned near it, if not adjust it by compressing the worm gear bearing mounts inward while setting worm gear mesh. This is very difficult and the reason the Losmandy OPWs were designed.?

You may just have a less than ideal worm on the RA, swap it with the DEC worm and retest. It may be that your DEC worm is better. Nobody cares how well your DEC error is, if you have a good polar alignment the DEC axis should not move at all. Swap the worm gears and retest, this may solve the basic issue, the rest is just adjustment.?

I hope this helps! Happy Thanksgiving!

Chip
?
 

Hi Greg,

Some actions to try:

I think you said your RA has the high precision Ovision worm system.? So Chip's comment about the brass Losmandy worm does not apply to that.? I don't have an Ovision worm but I understand that has a Belleville spring washer at the far end... likely there is an adjustment there to compress the spring ...it may need adjustment.? The worm must show no side to side play along the worm axis, as you wiggle the scope about the RA axis.

The second issue to evaluate is that the worm axis must also be in the same plane as the ring gear.? Some people had to shim the worm mounting to get that exactly level with, and the correct height, as the center of the ring gear.? See if you can assess that.??

The other thing to examine is to get the gearbox shaft to be exactly on axis with the worm axis...that makes the Oldham coupler essentially not move... and you want that to not move except to rotate.??

At that point the remaining PE is the quality of the worm, and the worm bearings.? There are terrific high quality R4 worm bearings of ABEC7 rating for about $20?or so each, at BocaBearings.com.?

To try and get the flaky Gemini1 to connect better, get the excellent USB to Serial adaptor made by ATEN, from their website ATEN.com, ~$20.? If that fails, you might have a damaged Gemini1 serial port chip...they can go bad, but are repairable.??

I suggest you completely balance your scope in both RA and DEC.?

To measure your PE accurately, put your guide scope on the main imaging scope...not the small 50mm guide scope? (the guide scope mounting could be shifting, etc).? Use PHD2 with your autoguide camera on the main scope to drift align your polar axis accurately.? Then measure your PE with autoguiding off, using about 3 x 8 minute worm periods data in a PHD2 log file.? Read the PHD2 log file into a program like? PECprep.exe. That has the settings for the G11 built in...just select that mount.? That will show the frequency components of the PE, and tell if it is the worm, the bearings, etc..

see a link to that here:



Have fun...you will get there.

Best,?

Michael?




On Nov 23, 2017 2:27 PM, "chiplouie@... [Losmandy_users]" <Losmandy_users@...> wrote:
?

Hi Greg,


A couple of thoughts on your process. You are not likely to get very low tracking error numbers with the stainless steel worms, you must have brass worms for the best precision and tracking. You must have some worm gear backlash between the worm gear and the worm wheel on RA, DEC is often times better with a bit less but in any case you cannot just set the backlash in the heat of the day and expect the backlash to remain the same. As the air temps drop so will the worm gear clearance, set your worm gear backlash in the COLD.?

Also none of the felt backlash can come from movement of the worm gear on the worm gear axis, it MUST have s slight preload, there can be no freedom between the gearbox output and worm gear input shaft, the coupler must be tight and free of any play. Check your worm gears for end play, it should be zero or darned near it, if not adjust it by compressing the worm gear bearing mounts inward while setting worm gear mesh. This is very difficult and the reason the Losmandy OPWs were designed.?

You may just have a less than ideal worm on the RA, swap it with the DEC worm and retest. It may be that your DEC worm is better. Nobody cares how well your DEC error is, if you have a good polar alignment the DEC axis should not move at all. Swap the worm gears and retest, this may solve the basic issue, the rest is just adjustment.?

I hope this helps! Happy Thanksgiving!

Chip
?
 


Swapped RA Gearbox to Dec,,,,,only change I see is the periodicity of RA looks more
like a saw tooth, Still have RA RMS at 1.6

Also removed all end play on RA and slacked up the worm to have a little
Backlash.....No Change?? RA RMS at 1.6

Today tear down of RA except where the shaft goes into the mount. Hesitant
to take those bearings out so just cleaning them and relube

All bearings look and feel good. Large thrust no play or rough? spots.

I found to other guys on CN that sent their mounts back to LM and Scott replaced the motors
and viola.....I have the older motors non high torque,,,,,not sure what the next step is., Maybe
send to LM

Greg
 

Forgot to mention I ran 3 worm cycles unguided thru Pecprep and bearings seem
ok according to the tool
 

aha!

I'd like to look at your PE for clues.

Please send me the unguided PHD2 logfile, with info on your Scope FL aperture, and Autoguide camera pixel size X and Y, and any Barlow info (same data PECPREP asks for...).? I'm at mherman346@....

Certainly if your mount is new, under warranty, and not satisfactory, get Losmandy involved.? I only have the oldest CG11 example,? and a modern but not newest GM8.??

Best,

Michael?


On Nov 25, 2017 12:27 PM, "gvblk4@... [Losmandy_users]" <Losmandy_users@...> wrote:
?

Forgot to mention I ran 3 worm cycles unguided thru Pecprep and bearings seem
ok according to the tool
 

"Recently Purchased a used G11 with G1 controller"

i'm guessing it's not under warranty


B
 

Used not sure how old......

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