From: albe albo <richter1956@yahoo.com>
Date: March 22, 2009 4:40:43 PM MDT
To: Astro_IIDC@yahoogroups.com
Subject: Re: [Astro_IIDC] Re: Enhanced Big Saturn as Milton suggested
Thx Milton,
i received the message on my mail too.
I'll check in order to find that log.
I'd like to disassemble the gpdx for a mechanical check but it is placed on a pier very well aligned to the pole so... i'm lazy.
I think to stick (with glue) a little laser pointer on the mount so that the beam will point on a wall distant 4 meters. Taking note about the red spot position on the wall i should be able to remove the mount and to reinstall it quickly with a good alignment.
Yesterday night i didn't resist to do a little guided DMK/DSO marathon taking M3, M51, NGC 3628 and NGC 4565.
I finished at 05.10 AM and now i must process the movies.
tonight i did a quick test on M42 very low on the horizon (20°) using a 80ED reduced to 480mm focal + neodymium filter because i read that it is not bad to be used like a kind of LPR filter allowing a good passage of Halpha wavelength.
I could post the results if someone could be interested.
As Milton suggested me months ago, yesterday i solved a AR guiding bouncing changing the counterweights position.
Example: M51 was guided perfectly then when i moved to M3 (axis flipping) things changed completely even doing a further re-calibration: the guide oscillated a little more than +2 -2 pixels .
At this point i moved the counterweights in order to get more weight in favor to the motor and the oscillations became very acceptable.
TTYL
Alberto
Da: Milton Aupperle <milton@outcastsoft.com>
A: Astro_IIDC@yahoogroups.com
Inviato: Domenica 22 marzo 2009, 23:09:58
Oggetto: [Astro_IIDC] Re: Enhanced Big Saturn as Milton suggested
Hi Folks;
I already asked Alberto for more details off list on his guiding issue.
One thing people can do themselves is to check the "Guiding Log" that Astro IIDC will create for you. It records everything (calibration, calculations, results and all tracking corrections) to do with guiding. If you have a problem ,I need to see the log. It has enough information that I can feed the data back into Astro IIDC and see what it generates out, so it's essential thing needed to diagnose any problem.
If you suspect there is some mechanical issue (i.e. backlash, over tightened gear tension etc.), you can check for this after you've done a calibration by looking at the log.
In the log, look for the block of text that starts with
------------ ---- Starting Calibration- ---------
and ends with
------------ ---- Calibration Completed--- -------
Inside of this block of text are usually four lines of information which will look something like this (the values may be different):
mPixelPerMillSecXRi ght = 0.00720
mPixelPerMillSecXLe ft = 0.00705
mPixelPerMillSecYUp 0.007526
mPixelPerMillSecYDo wn 0.007604
These indicate the measured move rates on each axis (assuming you calibrated on all 4 axis, which can be optional).
If you compare mPixelPerMillSecXRi ght to mPixelPerMillSecXLe ft or mPixelPerMillSecYUp to mPixelPerMillSecYDo wn, the values should be quite close, usually < 5% difference. If they are significantly different, then there is problem.
Most likely the problem is that the calibration could be bad (i.e. burst of turbulence, bumped scope, satellite, clouds) or a mount electrical / mechanical issue. If you repeat the calibration and the issue persists, it's most likely a mount issue.
Backlash should not show up in these calibration, unless it's really really excessive. And if it's that excessive, the there is no point trying to guide with that axis. If it takes 10 seconds to reverse directions (especially Dec), then your guiding basically goes uncorrected for 10+ seconds.
As far as mechanical issues go, one I am currently struggling with a tension issue on my HEQ5 mount's Dec gears, and it shows up like this.
mPixelPerMillSecYUp 0.009401
mPixelPerMillSecYDo wn 0.007903
What happens is that when the gears engage to move, the over tension causes the gears to rotate back up, which cause more motion than expected in the up direction and less motion in the down position. That's why the rates are so different. If you manually move it at a slow guide rate (using the buttons in the guide sheet or hand controller), you can see this happen if your paying attention (I wasn't) when you change direction.
Hope that helps..
Milton Aupperle