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CPC on a Wedge - Hand Controller Guide Rate?

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#1 katie

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Posted 20 June 2013 - 09:51 AM

For those of you with a CPC on a wedge, what % of sidereal do you use for RA and Dec (set in the Autoguide Rate menu)?

I know during calibration the software will compute the number of pixels moved by a fixed duration correction pulse. So, after calibration, for an equal move/correction requirement the software will send a longer correction pulse to move the mount if a lower % guide rate were in use than if a higher guide rate % were in use.

So....

By my simple mind, I would think that if you had 50% set as guide rate vs 100% guide rate the guiding software would simply compute/calibrate it needed to send a correction pulse twice as long to make the same correction than if 100% were in use. Yes/No?

Assuming all things being equal (polar alignment accuracy, guiding software, scope, etc), are there any advantages/disadvantages of 25 vs 75 vs 99 vs or any other percent set in the hand controller?

Is poor/unstable) seeing (vs good/stable) a contributing factor in determining the Guide Rate set in the hand controller?

Thanks.

#2 astrovienna

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Posted 21 June 2013 - 12:10 AM

I use 50% for both RA and Dec. I think I read somewhere that guiding software (or maybe this is an ASCOM issue) can only run at 50 or 100%, though you can set any value in the HC. I wouldn't use 100%. Although that would mean faster corrections (the answer to your second question is yes), it also means the drive would literally stop sometimes, which doesn't sound good when you factor in backlash. I don't think seeing should be an issue at all.

Kevin

#3 cn register 5

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Posted 21 June 2013 - 04:31 AM

Yes, the ASCOM driver only uses 50% and 100% of sidereal. This is because I use the same motor control commands as the HC uses for button moves at rate 1 or 2 and that's what they are. I use these commands because the PEC recorder can also see them. The ASCOM driver reads the guide rate at start up and if it's less than 75% uses 50% and if over uses 100%.

To add to the fun the CGEM, CGE Pro and AVX have a guide command built in and this will accept any rate so uses the same rate as that set for the hardware guide port.

Backlash should not be an issue unless the motor needs to run backwards in Ra which it doesn't. It will affect Dec movement, regardless of the guide speed.

You can try all this by setting the HC to rate 2 and seeing how the mount responds to HC button presses.

Chris

#4 katie

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Posted 21 June 2013 - 05:49 PM

Thank you both.
However, I connect to the autoguide port via a cable from the autoguider cam - I do not use an ASCOM guider driver.






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