Dithering and Slow Recovery PHD2


#1

I have my Max DEC pulse width set to 100ms. After a dither on DEC, I run into a situation where the DEC does not always recover or takes a long time to recover or a couple of times it lead to the sequence aborting. I have to manually increase the maximum pulse width to 250 or above for the DEC to recover.

There are two ways to resolve this:

1- Only Dither in RA
2- Have a configuration option in SGP where one can change the Max Pulse width after a dither and restore it once we reach desired guider accuracy. Restoring the pulse width is necessary as the value is the one was empirically derived to create the least oscillations in DEC.

Any suggestions are welcome, I am using “Very High Dither”.

Moussa

SGP 2.3.11
EQMOD
PHD2 Guiding


#2

Moussa,

What version of PHD2 are you using? In version 2.2.1 and later, the initial
pulses after a dither move the mount the precise amount to restore the
guide star back to the lock position after the dither, regardless of the
Max Dec or Max RA setting. After those initial recovery pulses, PHD2
resumes ordinary guiding (honoring max RA/dec) and may still require some
time to settle depending on backlash and other characteristics of the mount.

If you are using an up-to-date version of phd2 (the latest is 2.2.2a) and
are seeing the problem, it may be related to your Max Dec pulse setting
being so low. If that is the case, could you describe why you are setting
max Dec so low? There may be other solutions to whatever problem you are
trying to solve by doing that.

Andy


#3

Andy,

Thanks for the reply. I am running 2.2.1. Based on your explanation, it might be that my MAX DEC is too low. The problem I am trying to slow is that at higher MAX DECs, I see a lot of oscillation in DEC hence my need to decrease the length of the pulse. I am on a Orion Sirius Mount that I belt modded.

Conclusion however is that what I was proposing as a workaround is actually already the way PHD2 works…So I guess I will have to play with my parameters again…

Moussa


#4

Moussa,

There is always the possibility that your drive just takes a while to take up the backlash in the gearing. As the Dec axis is only adjusted any appreciable amount during a dither. One way round this it to make sure the dec axis is off balance a little, just as you would the RA, possibly make the camera end a little heavier.

Mike


www.mainsequencesoftware.com