The data discrepancy between PHD and PEMPro really confused me, so i just went to the raw log data for DerPits first run, where there was a large excursion when he wasnt guiding ( at about 1000 seconds in )
and processed it from first principles
From the raw log i see
Pixel scale = 1.28 arc-sec/px
xAngle = -6.4 deg
Dec = 72.1 deg
X Y RA DEC
968, 1012.496, "Mount", 4.447, 0.137, 4.404, 0.698, 0.000,0.007,0,,1,S,,,715221,496.34,0
sqrt( 4.447^2 + 0.137^2) = 4.45 = X/Y vector (in pixels) from lock
sqrt( 4.404^2 + 0.698^2) = 4.459 = RA/DEC vector (in ???) from lock
Note both are very similar, hence i assume the RA/DEC vector is also in sensor pixels????
If you compare this data to the log viewer ( I am using 0.6.2 ),
in RA/DEC mode, the spike max offset is shown as being about 5.7arcsecs in RA
Using RAerr = 4.404 pixels and 1.28arcsec/pix we get 5.64 arcsec, sooo close
I suspect what PHD is displaying is the error on the sensor converted to RA/DEC "axes", with no cos(DEC) correction, and as such, the RA error isnt the axle error
At DEC = 72deg we get cos(72) = 0.31
sooo my guess is the Y scale for DerPits RA data ( via PHD viewer ) is out by a factor of 3.33 ?????
and that would line up with what the PEMPro conversion showed.
No idea any more
Maybe someone who posts on the PHD site can get confirmation, as thats not something i had ever hit before.
Andrew Johansen Melbourne Australia
Edited by OzAndrewJ, 25 June 2019 - 02:30 AM.