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Old 22-01-2014, 03:19 PM
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White Rabbit
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Pulse Guiding vs ST4 help me understand.

Hi guys.

In my quest to automate my set up before my baby comes in May, I'm trying to get CCDAP to do an automated meridian flip. currently my autoguider does not support this.

Here is what I'm unsure of and please correct my me if I'm wrong.

Pulse guiding.

if you are guiding using Pulse guiding the software that you use monitors the guider and detects movements then issues commands the mount for corrections.

ST4 guiding.

the camera itself monitors the guider and dectects movement the relays that back to the mount driver for correction.

If my camera in ST4 mode is not capable of reversing the y axis after meridian flip them surly my guide software in pulse guide mode would be able to do this.

Am I missing something fundamental with this here?

Thanks
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  #2  
Old 22-01-2014, 03:40 PM
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Merlin66 (Ken)
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In ST-4 mode the camera communicates with a guide software (i.e. PHD) which calculates the necessary corrections and sends the signal back to the camera. It then sends the correction signals to the mount via the ST-4 cable.

(The latest PHD2 in ASCOM mount mode does allow meridian flip and continues guiding)
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Old 22-01-2014, 07:28 PM
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http://eq-mod.sourceforge.net/docs/EQASCOM_Guiding.pdf

Quote:
Some folks believe that because their guide camera has an ST-4 output this makes for more responsive
guiding. However this would only be the case if the camera itself is performing the autoguiding algorithm. If
the ST-4 port on the camera is simply controlled by the camera's driver and that the PC must first
communicate with the camera to initiate ST-4 signals then there really is no advantage other than possibly
tidier wiring.
In summary there is no reason why ST-4 guiding should offer any significant performance increase
compared to ASCOM Pulse Guiding. However the implementation of both methods is highly vendor specific.
For the Synta mounts using the EQASCOM driver and a PC based autoguiding program you are unlikely to
notice any difference in the responsiveness of ST-4 and ASCOM Pulse Guiding
Also:
After a meridian flip you need to recalibrate because
the whole mechanical system has changed especially
if you have deliberately slightly unbalanced the counterweight shaft.
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Old 22-01-2014, 10:20 PM
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DavidTrap (David)
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I have to tell CCDC in which half of the sky I have calibrated the guider - east or west. After a meridian flip it "reverses" the guiding. I think there's another button in Maxim that I have to unclick about auto pier flip??

DT
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Old 23-01-2014, 04:24 PM
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Thanks guys.

Alpal you don't have to re calibrate after the meridian flip if you have the correct set up. This is the part that I don't understand I can't understand if it's the camera that won't swap/read calibration data after the meridian flip or the software.

Mat from Software Bisque is saying that the camera I'm using does not support reversing the y axis, but surely it's the software that would do the reversing. Calibration is only camera angle and how far the star will move in arc sec for a given relay pulse.

Also I have a pendulum set up on RA axis so I am always east heavy.

David I'm pretty sure with ccdap you don't need to tell the mount what side the scope is on, but I could be wrong.
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Old 23-01-2014, 08:47 PM
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Quote:
Originally Posted by White Rabbit View Post
Thanks guys.

Alpal you don't have to re calibrate after the meridian flip if you have the correct set up. This is the part that I don't understand I can't understand if it's the camera that won't swap/read calibration data after the meridian flip or the software.
don't have to re calibrate

I've never understood that.
I am not a mechanical engineer but if you were to use a Newt. then
the focuser, OAG & camera would be on top of the OTA at say before the meridian &
underneath the OTA after the meridian.
There is apart from the RA & DEC axes a 3rd rotational axis from the
leverage of the focuser & camera.

I can't see how they mechanically can be the same in terms of
controlling what is a dual axis closed loop control system with a 3rd rotational axis.
I have noticed that some people put a weight balance on the side of the Newt.
directly opposite the focuser to counterbalance this axis.
In practice I suppose the Newt. could become too heavy to do that.
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Old 24-01-2014, 11:34 AM
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Quote:
Originally Posted by White Rabbit View Post
Thanks guys.

Alpal you don't have to re calibrate after the meridian flip if you have the correct set up. This is the part that I don't understand I can't understand if it's the camera that won't swap/read calibration data after the meridian flip or the software.

Mat from Software Bisque is saying that the camera I'm using does not support reversing the y axis, but surely it's the software that would do the reversing. Calibration is only camera angle and how far the star will move in arc sec for a given relay pulse.

Also I have a pendulum set up on RA axis so I am always east heavy.

David I'm pretty sure with ccdap you don't need to tell the mount what side the scope is on, but I could be wrong.
PhDguiding V2 automatically flips the calibration data and corrects for dec differences after a meridian flip or going to a new object. No need to recalibrate and I've found that retrieving a previous nights calibration data and setting guiding going it will find a guide star and start guiding. Also after a meridian flip it will re-acquire a guide star and initiate guiding.
Allan
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