Look at the declination error (red line). It goes down, down, down way off scale then eventually corrects.
At some other times during the same guiding session, the declination error just stayed around the center..
PHD problem: what does this mean??
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orly_andico
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PHD problem: what does this mean??
Look at the declination error (red line). It goes down, down, down way off scale then eventually corrects.
At some other times during the same guiding session, the declination error just stayed around the center..
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timatworksg
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- Joined: Mon Feb 01, 2010 9:42 pm
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Orly, couple of possibilities.
- Any slippage in the DEC? Such as weight shift (scope and everything balanced properly?) Is side by side mounted, does the scope tend to weigh heavier when turned to another side causing weight to shift? I had this issue when I used a side by side mounting on a twin dovetail. At some angles they balance, but at certain angles it's biased one side due to a pendulum effect. IT needs to be balanced pretty much all way around.
- Autoguiding speed setting on the handset? try changing that to something like x0.75 or x1.0, etc. Something could have been changed without knowing. Had such an issue with EQMOD after I re-installed it. Also, if you are using EQMOD, turn off Pulse guide in the EQMOD settings as it tends to screw with PHD a little. It can work, just havent got time to read it up properly.
- Any cable Drag? Sometimes a hanging cable off the scope not secured to the mount, but allowed to hang down, can cause drag. Secure the cables from Cams to the rear of the mount.
- I noticed your PHD settings are set as seen in the graph! Try changing the Mx dec (Maximum Declination) to 150ms/200ms. 2000ms elapse before next check may be too long. Your Mn Mo(minimum motion) is at 0.03pixels. Your checking in very close detail. Try a setting of 0.20.
At best, did you get good guiding at the default settings? If so, revert.
If it was wind, clouds, or knocking into it, both RA and Dec would Jump like a Heart Attack! But it seems the DEC went off! As mentioned, I had this when my EQMOD pulse guide tracking was 'ticked' and the Autoguide speed was wrong. My DEC went OFF the graph and sometimes never came back! RA was no issue!
Hope this helps!
- Any slippage in the DEC? Such as weight shift (scope and everything balanced properly?) Is side by side mounted, does the scope tend to weigh heavier when turned to another side causing weight to shift? I had this issue when I used a side by side mounting on a twin dovetail. At some angles they balance, but at certain angles it's biased one side due to a pendulum effect. IT needs to be balanced pretty much all way around.
- Autoguiding speed setting on the handset? try changing that to something like x0.75 or x1.0, etc. Something could have been changed without knowing. Had such an issue with EQMOD after I re-installed it. Also, if you are using EQMOD, turn off Pulse guide in the EQMOD settings as it tends to screw with PHD a little. It can work, just havent got time to read it up properly.
- Any cable Drag? Sometimes a hanging cable off the scope not secured to the mount, but allowed to hang down, can cause drag. Secure the cables from Cams to the rear of the mount.
- I noticed your PHD settings are set as seen in the graph! Try changing the Mx dec (Maximum Declination) to 150ms/200ms. 2000ms elapse before next check may be too long. Your Mn Mo(minimum motion) is at 0.03pixels. Your checking in very close detail. Try a setting of 0.20.
At best, did you get good guiding at the default settings? If so, revert.
If it was wind, clouds, or knocking into it, both RA and Dec would Jump like a Heart Attack! But it seems the DEC went off! As mentioned, I had this when my EQMOD pulse guide tracking was 'ticked' and the Autoguide speed was wrong. My DEC went OFF the graph and sometimes never came back! RA was no issue!
Hope this helps!
My wife never complained about how much time, effort & money I spent on my Astronomy hobby!................suddenly I met her!!!
What is the trend beyond the timeline shown? Maybe u can post one with the timeline setting set to 500 instead of 100 to see the long term behavior. My mount will also tend to have an overshoot in DEC in the beginning of an object capture... But after a few seconds even minutes... It goes stable... Otherwise it would be DEC stition... If your RA behavior ok? Here it looks like it is going off gradually too....it is impt to go through the calibration when the sky is cloud free at that region and an auto guide rate of 0.5x or 0.75x is set and remains as it is throughout the entire session....
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orly_andico
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Hi Tim, Remus
1) the guiding rate on the handset was 2X. This is my rust-bucket Vixen GP with DD-1 stepper motor controller (modded). It's controlled with a GPUSB-AH. No pulse-guiding or anything fancy here.. the only other speed is 32X so can't use that..
2) the trend line after the DEC divergence was relatively flattish, it didn't excurse far from the center. I didn't run for more than 40 minutes (was just measuring the PE). My concern is that if that DEC is cyclic, I will end up throwing away 25% of my frames.
3) I set the Mx DEC to 2000 because I thought it would be more aggressive with big numbers :-) didn't know that was a time dimension.
4) the RA was ok. I posted the PE graph here earlier. 20 arc seconds peak to peak. With a huge spike once in every worm cycle.
I think it may have been cable drag (the DSI has a short cable). Anyhoo your points are very useful, thanks! I have no idea what those numbers in the Brain mean...
1) the guiding rate on the handset was 2X. This is my rust-bucket Vixen GP with DD-1 stepper motor controller (modded). It's controlled with a GPUSB-AH. No pulse-guiding or anything fancy here.. the only other speed is 32X so can't use that..
2) the trend line after the DEC divergence was relatively flattish, it didn't excurse far from the center. I didn't run for more than 40 minutes (was just measuring the PE). My concern is that if that DEC is cyclic, I will end up throwing away 25% of my frames.
3) I set the Mx DEC to 2000 because I thought it would be more aggressive with big numbers :-) didn't know that was a time dimension.
4) the RA was ok. I posted the PE graph here earlier. 20 arc seconds peak to peak. With a huge spike once in every worm cycle.
I think it may have been cable drag (the DSI has a short cable). Anyhoo your points are very useful, thanks! I have no idea what those numbers in the Brain mean...
Last edited by orly_andico on Wed Feb 16, 2011 11:08 pm, edited 2 times in total.
oh! it occurred before to me....thinking that short cables were better (neater, etc), in the end, settled with a much longer one...i try not to manipulate the brain settings too much, and prefer to ensure that mechanics wise, the mount gear is clean, free from sand, coarse particles, etc... somehow the autoguiding then worked better this way, which of course is my own personal experience/encounter... good luck!
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orly_andico
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the top button enables you to see a longer-term profile of the autoguiding process if you set it to a bigger number...i like to set it to the biggest value so that i know (one look) if anything goes wrong during long exposures (20 min subs) for example...the default 100 is too short for useful monitoring of long term trends...
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timatworksg
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Hi Orly,
No harm but to try everything...if all else fails revert to defaults. Besides PHD works best at default..lol!
Remus's 500 is the number of graph frames which makes his graph smaller so he see's more in that small window that at a setting of 100! Remu's goes ALL Night Long!!! HAHA!
The brain can be daunting, but if you check up Stark Labs website and the manual, it explains it in very nice detail. In a nutshell, the ones that can affect calibration and guiding, through my tinkering so far...hehe
- RA Aggressiveness.
Should be good at 100 (default) unless you find your mount correcting in RA too much and want something subtle. However settings ranging from 70-100 are common (from online reading). Mine is set at 80 from my GP to my now Sirius.
- DEC guide mode.
Keep at Auto. North and South is for when in some cases, a DEC seems to be to biased in weight oneway, one can force PHD to overcorrect.
- Calibration Steps (ms).
Increasing this is good for short FL where stars hardly move and PHD can't pick up much to calibrate drift. If you find the star hardly moves when PHD is calibrating, you will get an error report from PHD stating which point (NSEW) it couldn't calibrate correctly. So increasing the (ms) milliseconds, gives more time in each NSEW drift check, in turn allowing the star to drift more. Setting the exposure to 1.5/2secs also helps somewhat. With increased (ms) calibration may take longer than normal so wait it out.
The rest can be left at defaults. As they are more for the techies or those who wanna try everything...lol!
But like Remus, after guiding starts, it takes awhile for the DEC to come down to Earth...lol! Or level off. Then I can start exposing...urm....imaging.
And yeah...check for cable drag. Something could be Yanking it back a little. I cable tie all cables and hook them to the back of the mount's polar scope cover. That way everything has a central pivot point with no tangles. Then again check for loops after tying them up. Some cables are stiffer than others and can causepush/pull ups when looped.
Here's mine when the Vixen GP with IOptron Motors were on my Pier
No harm but to try everything...if all else fails revert to defaults. Besides PHD works best at default..lol!
Remus's 500 is the number of graph frames which makes his graph smaller so he see's more in that small window that at a setting of 100! Remu's goes ALL Night Long!!! HAHA!
The brain can be daunting, but if you check up Stark Labs website and the manual, it explains it in very nice detail. In a nutshell, the ones that can affect calibration and guiding, through my tinkering so far...hehe
- RA Aggressiveness.
Should be good at 100 (default) unless you find your mount correcting in RA too much and want something subtle. However settings ranging from 70-100 are common (from online reading). Mine is set at 80 from my GP to my now Sirius.
- DEC guide mode.
Keep at Auto. North and South is for when in some cases, a DEC seems to be to biased in weight oneway, one can force PHD to overcorrect.
- Calibration Steps (ms).
Increasing this is good for short FL where stars hardly move and PHD can't pick up much to calibrate drift. If you find the star hardly moves when PHD is calibrating, you will get an error report from PHD stating which point (NSEW) it couldn't calibrate correctly. So increasing the (ms) milliseconds, gives more time in each NSEW drift check, in turn allowing the star to drift more. Setting the exposure to 1.5/2secs also helps somewhat. With increased (ms) calibration may take longer than normal so wait it out.
The rest can be left at defaults. As they are more for the techies or those who wanna try everything...lol!
But like Remus, after guiding starts, it takes awhile for the DEC to come down to Earth...lol! Or level off. Then I can start exposing...urm....imaging.
And yeah...check for cable drag. Something could be Yanking it back a little. I cable tie all cables and hook them to the back of the mount's polar scope cover. That way everything has a central pivot point with no tangles. Then again check for loops after tying them up. Some cables are stiffer than others and can causepush/pull ups when looped.
Here's mine when the Vixen GP with IOptron Motors were on my Pier
My wife never complained about how much time, effort & money I spent on my Astronomy hobby!................suddenly I met her!!!
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orly_andico
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