Reversing DEC output after meridian flip using GSS

[djgo...@gmail.com]

Hello everyone,

Probably this has been discussed/answered in previous threads; however, I couldn't find the answers that helps me to clarify the following concern:

A few days ago, I watched a YouTube tutorial related to Green Swamp Software (GSS) and PHD2 interaction and setting. The author of the video recommended selecting the option "Reverse DEC output after meridian flip" when using SW EQ6R-Pro mounts. This is because apparently GSS doesn't provide the input required by PHD2 to know in which side of the pier the mount is after completing the flip. My concern is that there is a note in the box related to this option indicating that this action will clear the existing calibration data.

If I understand this correctly, it seems that I will have to perform a new calibration after completing a meridian flip, correct?

Thanks and clear skies,

Diego.

[Bruce Waddington]

Hi Diego.  To cut to the chase, this is what you want to do:

1.  Set 'Reverse Dec output after meridian flip'

2.   Use the new Calibration Assistant (Tools menu) to get a calibration that is at least acceptable

3.   Start imaging and don't worry about this anymore.  The calibration will be adjusted automatically whenever there is a meridian flip

To give you some more information and to clear away some of the YouTube smoke and dust,  the GSServer does report side-of-pier correctly.  The only reason for any of this "reverse Dec output' stuff is that there is no standard for whether a mount manufacturer/driver author is going to react to changes in side-of-pier as it relates to the direction the Dec axis is going to turn.  Traditionally, a move of either 'north' or 'south' on the Dec axis would always cause the axis to spin in the same direction - either clockwise or counter-clockwise as viewed from above the mount.  This means that a 'north' or 'south' move isn't necessarily the same as 'sky-north' or 'sky-south' - it would depend on which side of pier was being used.  None of this matters for imaging and program-control of the mount but some visual users might not have liked it.  Probably for that reason, some newer mounts and drivers force 'north' and 'south' to mean 'sky-north' and 'sky-south', which means that the direction the Dec motor runs is reversed after a meridian flip.  This affects the PHD2 calibration for obvious reasons.  It is easy to automatically make the adjustment as long as PHD2 knows which way the Dec axis is being controlled.  The GSServer changes the direction of the Dec motor depending on side-of-pier, so the checkbox needs to be checked in PHD2.  In contrast, the EQMod driver doesn't do this and the box is left un-checked.

Hope this helps,

Bruce