From: Mark Gaffney <markgaffney@me.com>
Date: August 18, 2010 2:27:43 PM MDT
To: "Astro_IIDC@yahoogroups.com" <Astro_IIDC@yahoogroups.com>
Subject: Re: [Astro_IIDC] Re: ready for guiding with Kwiq scope..
Hi Milton, I've got a lot to learn! The mount's just a lowly CG-5 & I haven't got around to playing with the backlash settings yet. I noticed I somehow had the solar/ lunar option selected & I certainly don't remember checking that. The cables were better organised tonight than the night before- I've got such a plethora of them now! The weather was nice & dry (thankfully as my 7AH Celestron battery tank gives up quite quickly powering my dew strap..) with a slight breeze & rather bright moon as you know.
I'm glad you're so quick with your responses as our power goes off early this morning for the day whilst they work on the lines but I'll be able to study your suggestions if I print off the message now..Thanks
Mark.
Sent from my iPod
On 19/08/2010, at 6:06 AM, Milton Aupperle <milton@outcastsoft.com> wrote:
Hi Mark;
Thanks for the log.
What was the CGE mount set to for Guiding Rate (you need to set this in the Hand Controller) and what focal length were you guiding at? I normally use Guide Rate of 0.5x or 0.75x for 1100 mm focal length and then use 7.0 seconds for the starting motion time. I also have my minimum pixel distances set to 25 for RA and 20 for Dec.
The reason you want more motion is to make sure that things like slack in the gears is eliminates, which is hard to do with short times (you started with 2 seconds).
The first calibration is screwed up on the Dec axis:
mPixelPerMillSecYUp 0.010287
mPixelPerMillSecYDown 0.027665
I'm not sure why, but the Dec rates are 200% different which usually indicates that there is a problem (i.e. Dec slack / backlash on gearing, bad star, wind / turbulence).
The second Calibration:
mPixelPerMillSecYUp 0.016130
mPixelPerMillSecYDown 0.019811
looks better, but the RA Calibration is really bad.
CalibX4: R Dist 24.54 X1: 897.93 Y1: 449.84
CalibX5: L Dist 83.40 X2: 973.54 Y2: 485.04
CalibX6: R Dist 71.23 X1: 909.04 Y1: 454.81
CalibX7: L Dist 15.16 X2: 897.30 Y2: 445.22
CalibX8: R Dist 9.82 X1: 905.02 Y1 451.29
CalibX9: L Dist 18.43 X2: 923.44 Y2: 450.79
mPixelPerMillSecXRight = 0.01760
mPixelPerMillSecXLeft = 0.01300
The number to watch is the "R Dist" and "L Dist" values. They should be less than 5% different from each other and consistent between each pass. If they are not, then something is wrong, such as gearing issues or drag or something else. For example in your images you showed of your setup, you have the cables dragging across the grass. That will throw everything off for RA as the cables snags on grass blades (yes, we are talking about those sorts of tolerances), especially at longer focal lengths. All my cables are hanging in the air and are fastened via velcro straps to the tripod legs. You get weird jerky motions if they drag / snag.
As an example of what a good well tuned mount should look like, here is what I get for calibration on a star near the equator (-6° dec) using the HEQ5 mount with the GPUSB, a DMK camera (5.65 micron pixels) at 1125 mm focal lengths and 7 seconds for motion time.
CalibX4: R Dist 54.89 X1: 319.12 Y1: 233.20
CalibX5: L Dist 52.14 X2: 370.52 Y2: 241.94
CalibX6: R Dist 52.31 X1: 318.91 Y1: 233.40
CalibX7: L Dist 54.20 X2: 372.35 Y2: 242.48
CalibX8: R Dist 52.09 X1: 321.11 Y1 233.16
CalibX9: L Dist 52.88 X2: 373.24 Y2: 241.96
mPixelPerMillSecXRight = 0.00759
mPixelPerMillSecXLeft = 0.00758
CalibY0: Removing Dec Up Slack X0: 319.06 Y0: 232.71
CalibY1: Starting Dec Up Calibration X0: 321.54 Y0: 219.10
CalibY2: Up Distance 39.81 X1: 326.86 Y1: 179.65
CalibY3: Removing Dec Down Slack X0: 314.42 Y0: 228.22
CalibY4: Down Distance 41.43 X1: 306.77 Y1: 268.94
mPixelPerMillSecYUp 0.007108
mPixelPerMillSecYDown 0.007398
My Left / Right distances are with 2 pixels (2.5 arc seconds) of each other (52 to 54 pixels) motion for 7 second runs and my rates of motion are are nearly identical 0.00759 versus 0.00758. My Dec has a similar story and are about 2 pixels (2.5 arc second) difference and have rates of motion 0.007108 versus 0.007398.
That means I have no appreciable back lash or mechanical issues and most of the error is my habitual poor crappy seeing (averaging FWHM of 4 arc seconds or worse).
HTH..
Milton J. Aupperle
President
ASC - Aupperle Services and Contracting
Mac Software (Drivers, Components and Application) Specialist
#1106 - 428 Chaparral Ravine View SE.
Calgary Alberta T2X 0N2
1-(403)-453-1624
On 18-Aug-10, at 12:44 PM, Mark Gaffney wrote:
Milton,
Astro IIDC seemed to track well all night tonight but I was having troubles with my downloads from my Nikon in ImagesPlus first from my iBook running Virtual PC for Mac then when I took my PC over to the paddock.
Probably something simple..I probably wouldn`t have gotten my image anyway, as I noticed the power to the mount had stopped when I went back out some time later.
My AC power adapter is just holding together ( the end of it has been pulled out several times & the pins reinserted) but I could have sworn it was still working after I plugged the GPUSB into the Autoguide port??
Not your problems I know, just by way of explanation!
Acquiring a guidestar was easy..Here`s the log
<Guiding Log 20100818_200453.txt>
Any suggestions would be welcome..
Mark.