PHD and PHD2 Erratic Star Movement on DEC

[CarlightExpress]

Hi All

I seem to be having major problems with guiding and I cannot figure it out, I have tried PHD, PHD2, I have tried the In built QHY5LII Driver in PHD2 and the ASCOM driver in PHD and PHD2 but both give me similar results, but I am seeing a very erratic DEC line on the graph, even with DEC guiding switched off.

My mount is perfectly polar aligned as I used the routine in PHD2 to polar align the mount (which is an EQ8 Pro), and both West and South register a mis-alignment of 0.01" (1px)

I have tried guiding on both scopes, AT8RC and C80ED and both scopes produce the same Erratic DEC graph line, again even with DEC guiding switched off, my gut feeling here is that this is a camera issue, since it reports the same when DEC guiding is disabled, sometimes the erratic graph goes as high as +2" or -2" on the graph.

• Mount perfectly polar aligned
• Tried exposure settings up to 3 seconds
• Tried on AT8RC using an OAG, and also without an OAG on the C80ED (Much shorter focal length)
• Different targets in Dec and RA produce similar results
• Tried slightly defocusing the Guide Camera

My guide settings are, 70% Aggression, 15% Hystersis, Mn Mo 0.42, Max Pulse 500ms

The mount itself is scope side heavier on RA, but this should not affect DEC anyway, and it is slightly camera side heavy on DEC

Even when I was performing the polar alignment, the graph was erratic but the trendline reported pretty stable

Has anyone got any ideas?

Simon

[libraryman]

Not sure if my settings will help but for info mine are: aggressive 85...hys....0...min motion 0.12.......Max move 2000.

I run my scope quite nose heavy..with pa within 1 arc min! Typically my Dec guiding is better than RA but only slightly. I.E...0.12 RA & 0.07 dec.

RMS last night was 0.5 to 0.65 avr.

I use the guiding assistant to help!

Tracking rate 0.5x 3sec exposure....fsq106 ....qhy5Lii mono through a finder guider on an eq8.

I was imaging at 40deg Dec...it may depend on your target position!

Ray

[CarlightExpress]

Thanks Ray

I've tried different DEC targets, my Guide rate is 0.3 so I might look into that one, why do you have your Mn Mo set so low?

Simon

[libraryman]

Hi Simon, simply because that was the recommendation with the guiding assistant..... It seemed to work o.k but I guess its also because of the guider ratio which is around 3.9..

Ray

[libraryman]

Just thinking about the guide rate, I used to use 0.3x and I also used a higher minimum motion, my guiding was not as good!

Ray