开云体育

  1. Losmandy_users
  2. Topics

G11G Gemini2 PHD2 autoguiding calibration jumps by more than 20px during east calibration

Nikul Suthar
 

Hello All,
?
I've older version of G11G with OPWB (Prior to Spring loaded worm gear). I'm getting a sudden jump in PHD2 autoguiding calibration process when after moving by 25px in the west and as soon as it tries to move back towards east direction. This can be seen in my below uploaded video sharp at 31 seconds:
?
?
This calibration is closer to Meridian and East pointing West. But same observation is during calibration closer to Meridian and West pointing to East. I just re-greased the spur gears and the worm-wormwheel assembly with Liqui Moly in both RA & Dec axes. I then adjusted backlash to be minimum both in RA & Dec axes. Regardless of minimal backlash adjustment or not this behavior keeps repeating. I fairly balanced my Celestron C9.25 OTA with 1384 focal length after 0.63 reducer. I'm doing off axis guiding with this same focal length and have configured PHD2 as well with it. I made sure that the Dec motors are tightly screwed in.
?
Anybody has any ideas on why this is happening then that would be really helpful. I can provide more details if anybody asks and can try suggestions the next night I get to imaging.
?
Thanks,
Nikul
?
 

Hi Nikul,
?
Are you sure the jump is in RA and not in DEC? Backlash in RA isn't normally an issue, since during tracking/guiding the mount doesn't reverses direction in RA. The opposite of backlash is stiction, something that is caused by worm/gear being too tight. This allows for energy to be built up during normal movement and to be released suddenly at certain times. Leaving a little backlash in the worm/gear is important to avoid this. Other places to look:
?
  • The oldham coupler may be loose (set screw needs to be tightened)
  • The worm isn't tight enough between the two bearings that hold it, allowing the worm to move between them (not sure how the OPWB handled it)
Regards,
?
?-Paul
?
On Tue, Aug 13, 2024 at 02:28 AM, Nikul Suthar wrote:

Hello All,
?
I've older version of G11G with OPWB (Prior to Spring loaded worm gear). I'm getting a sudden jump in PHD2 autoguiding calibration process when after moving by 25px in the west and as soon as it tries to move back towards east direction. This can be seen in my below uploaded video sharp at 31 seconds:
?
?
This calibration is closer to Meridian and East pointing West. But same observation is during calibration closer to Meridian and West pointing to East. I just re-greased the spur gears and the worm-wormwheel assembly with Liqui Moly in both RA & Dec axes. I then adjusted backlash to be minimum both in RA & Dec axes. Regardless of minimal backlash adjustment or not this behavior keeps repeating. I fairly balanced my Celestron C9.25 OTA with 1384 focal length after 0.63 reducer. I'm doing off axis guiding with this same focal length and have configured PHD2 as well with it. I made sure that the Dec motors are tightly screwed in.
?
Anybody has any ideas on why this is happening then that would be really helpful. I can provide more details if anybody asks and can try suggestions the next night I get to imaging.
?
Thanks,
Nikul
?
Nikul Suthar
 

Hi Paul,
?
I'll try after keeping a little more backlash in RA & in DEC. I'll make sure that the clutches are not too tight. As such the autoguiding for East pointing West is fairly good with sub arc second total at 1384 mm focal length. Let me try these out and get back.
?
Thanks,
Nikul
?
 

On Tue, Aug 13, 2024 at 02:28 AM, Nikul Suthar wrote:
any ideas
In the video, the mount moves as directed during recalibration, although there is a delay in image capture. The question is whether the mount can move 25 pixels in the roughly one second of exposure and processing time. The software appears to reposition to the guide star with high precision. From this, I deduce that the mount does move the specified distance within that timeframe upon command, and it does so with considerable accuracy.
 

I don't see anything bad in your video. After the west steps (usually 12 on default settings) the east steps are quite abrupt and fast, in just three should get the star to the original position.? Then it starts clearing backlash steps at which your video ends. Can you provide the calibration plot ?? More important, after calibration is there any warnings from PHD2 ? And last but not least, how is your guiding ??
?
Regards,
Daniel
 

Nikul,
?
There is still probably some backlash somewhere, but the question is whether it is actually hurting your guiding. Your Ra gears are only turning in one direction, so a little backlash will eventually get taken up with westward motion, then PHD2 will either slow it down or speed it up to match your guide star motion. If you check your log with PHD2 Log Viewer, that should tell you if RA is doing anything unusual.?
?
As far as trying to take up the slack mechanically, you will only get the worm pressed into the ring gear so much before the mount will stall (I have the non-spring-loaded type as well). For other adjustments, there is the Belleville washer upgrade which takes up slack between the worm bearings, replacing the gearbox, or just trying to better seat the motor by loosening the screws and giving it a slight clockwise twist.?
?
Good luck.
?
John
--
_____________________________________________________________________________________________________________________________________________________________________________

Losmandy G11G2 on pier; refurbed Losmandy G11 with OnStep controller; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED with field flattener; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, NINA, Sequence Generator Pro and PixInsight user
Nikul Suthar
 

Hi All,

I re-adjusted the backlash with a quite relaxed margin in both RA & Dec axes. I double checked the balancing in RA axis and indeed I found a little too extra CW heavy which I fixed. Now that jump is not that big. The calibration happens with some issues but the guiding is good sub arc-second at 1384 mm focal OAG guiding. I've attached the calibration & guiding screenshot. I've also attached today's PHD2 logs where there are many anomalies logged for today.

Thanks,
Nikul


????, 13 ?????, 2024 ?? ??? 09:39 PM ?????? ?? ??? John Kmetz via <jjkmetz54=gmail.com@groups.io> ? ??????:

Nikul,
?
There is still probably some backlash somewhere, but the question is whether it is actually hurting your guiding. Your Ra gears are only turning in one direction, so a little backlash will eventually get taken up with westward motion, then PHD2 will either slow it down or speed it up to match your guide star motion. If you check your log with PHD2 Log Viewer, that should tell you if RA is doing anything unusual.?
?
As far as trying to take up the slack mechanically, you will only get the worm pressed into the ring gear so much before the mount will stall (I have the non-spring-loaded type as well). For other adjustments, there is the Belleville washer upgrade which takes up slack between the worm bearings, replacing the gearbox, or just trying to better seat the motor by loosening the screws and giving it a slight clockwise twist.?
?
Good luck.
?
John
--
_____________________________________________________________________________________________________________________________________________________________________________

Losmandy G11G2 on pier; refurbed Losmandy G11 with OnStep controller; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED with field flattener; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, NINA, Sequence Generator Pro and PixInsight user

PHD2_GuideLog_2024-08-13_222906.txt
PHD2_GuideLog_2024-08-13_222906.txt

 

Some of the calibration were good others interrupted for star lost.? I'v seen many backlash clearance steps in some calibration. Are you sure that the clutch pads are clean and free of oil ??? ?On the other hand, you should guide longer, the guide segments are too short to look at error spectrum.
?
Regards,
Daniel
 

On Wed, Aug 14, 2024 at 06:38 AM, Daniel wrote:
the guide segments are too short to look at error spectrum
Yes. A guide log of 30 minutes or so would be more useful.
?
John
--
_____________________________________________________________________________________________________________________________________________________________________________

Losmandy G11G2 on pier; refurbed Losmandy G11 with OnStep controller; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED with field flattener; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, NINA, Sequence Generator Pro and PixInsight user
Nikul Suthar
 

I checked Dec axis clutch pad is clean and in perfect shape. I'll try to get a 30 minute guide logs with at least 3 seconds of guide camera exposures. I replaced my Celestron C9.25 to SkyWatcher Quattro 250P 1000mm focal length with same cameras and off axis guiding. I still have to run guide calibration on both the sides of meridian for calibration graph and do guiding assistance for more details about backlash, orthogonality and polar alignment error. I'll get back with these details after a day or two...


On Wed, Aug 14, 2024, 9:16 PM John Kmetz via <jjkmetz54=gmail.com@groups.io> wrote:
On Wed, Aug 14, 2024 at 06:38 AM, Daniel wrote:
the guide segments are too short to look at error spectrum
Yes. A guide log of 30 minutes or so would be more useful.
?
John
--
_____________________________________________________________________________________________________________________________________________________________________________

Losmandy G11G2 on pier; refurbed Losmandy G11 with OnStep controller; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED with field flattener; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, NINA, Sequence Generator Pro and PixInsight user

1 - 10 of 10