PHD2 quirks

[Davey-T]

Just been playing around with PHD2 while waiting for it to get dark and a couple of things.

First it claims that my RA and Dec axis aren't at right angles to each other, doesn't say by how much ? should I be worried ?

If I let it choose a guide star it picks one that's practically invisible when there are others available and when calibrating complains that it's lost it ?

Have always used PHD1 and thought I ought to try PHD2.

Dave

[kenny k]

Cant comment on phd1 but phd2 has worked fine,not played with settings too much and i have been told to pick a star near the edge of screen.Seems to calibrate ok and had decent graphs.

Hope you can get yours sorted.

Kenny

[Horwig]

Mine was complaining that axis were not orthogonal too. I think it's something to do with guide camera not being orthogonal to ra/dec.

There was a posting about it on the yahoo group, I ignore it, there's a button in brain to switch off the warning.

Can't comment about auto selecting stars, I always select my own, then when it goes wrong there's no one to blame but me.

Huw

[ChrisLX200]

I thought the orthoganality error was due to the OTA being tipped up/down (not parallel to the RA axis), so when it calibrates both axies they aren't at exactly 90 degrees. It is something you can correct with shims under the front or rear rings. My mount tells me the extent of this error when it runs an all-sky model.

I believe by default PHD2 will not select a star which is saturated (flat top to the star profile) so it will tend to choose dimmer ones. When calculating the centroid there will be an area of uncertainty if the star is saturated. You can de-focus (slightly!) to spread the light out a bit more, or you can use PHD2's noise reduction (e.g., 2x2 or 3x3 matrix) to do the same. With my Lodestar PHD2 would often report low SNR on alternate frames (the camera being interlaced) resulting in the star being 'lost', which was *** annoying.

ChrisH

[libraryman]

If PhD is saying axis are not at right angles the the tools calibration review should indicate how much!

I assume it might be a poor calibration perhaps due to backlash or guide rates

I usually select my own star but last night PhD did select a really good star with good snr!

Ray

[Horwig]

Here's the discussion of the orthogonaity error:

http://stargazerslounge.com/topic/238953-phd-non-orthogonal-error/

Huw