Long wait after dithering

[STEVE333]

Hi all - I've been using BYEOS very successfully now for a few years.  However, my mount has recently developed some very bad Declination backlash that, so far, I've not been able to correct.

 

My solution has to been to guide in RA only while turning of the Dec guiding.  My polar alignment is quite good, so, the Dec drift is still acceptable even for my 5 min exposures.

 

Now the problem: 

1. In PHD2 I've checked the Dither RA only and Random options.
2. In PHD2 I've set the Dec guide mode to Off.
3. Because I'm not guiding in Dec, the Dec error slowly grows over time.
4. In BYEOS I've set the Dither Calm down period to 25 sec.
5. The problem is that it takes BYEOS about 3 minutes every time to start the next image. This is a big waste of time.  The RA guiding is ready to start guiding again in a short period of time, but, apparently because of the large Dec error, BYEOS is waiting a long period of time before finally starting the next image.

Is there some way to prevent the dither from wasting so much time?  Am I missing something?

 

NOTE:  Before my Dec backlash problems I used to guide and dither in both RA and Dec, and, the time between images was typically about one minute.

 

Steve

[STEVE333]

Instead of turning Dec Guiding OFF, I'd suggest trying "ResistSwitch" and Dec Guide Mode "North-Only" with your Scope Balanced so as to cause it to Drift South.

 

This is the usual Suggestion provided by the PHD2 Support Forum to overcome big Dec Backlash. And would keep your Dec Error to a Minimum...

Hi all - I wanted to complete this thread.

 

Last night I tried something similar to s3igell's approach mentioned above.  

1. I purposely misaligned the PA a little (a few arc minutes) to cause Dec drift.
2. I chose the RA only dither setting in PHD2 (Global tab).
3. I performed a PHD2 calibration and started guiding, but, with the Dec guiding OFF.  I checked to see which way the Dec was drifting (North or South).  
4. Since the Dec drift was to the North, I set the Dec guide mode to South.
5. I selected the Lowpass Dec algorithm.
6. I reduced the Max Dec duration to 1000 to prevent any large "over corrections".  
7. I reset the BYEOS Settle dither at parameter to the more reasonable value of 0.30.  

This combination of settings provided excellent guiding, and, the time between images was only about 30 sec.

 

Thanks all for your suggestions and help.  I now have a good means of guiding even with my horrible Dec backlash, and, the time to do the dithering is only about 30 sec.

 

Steve

[s3igell]

Instead of turning Dec Guiding OFF, I'd suggest trying "ResistSwitch" and Dec Guide Mode "North-Only" with your Scope Balanced so as to cause it to Drift South.

 

This is the usual Suggestion provided by the PHD2 Support Forum to overcome big Dec Backlash. And would keep your Dec Error to a Minimum...

[astroman133]

This is a PHD issue, not a BYE/BYN issue. BYE/BYN waits until PHD has settled at the new lock point until proceeding with the next exposure.

[admin]

As Rick said, PHD does the dithering, BYE simply waits until it is done.  This is not a BYE issue.

 

However, if you want to start imaging sooner you'll need to increase the settle dither at parameter in BYE from it's default 0.20 to say 0.50 and see if this makes a difference.  

[STEVE333]

This is a PHD issue, not a BYE/BYN issue. BYE/BYN waits until PHD has settled at the new lock point until proceeding with the next exposure.

Thanks astroman - good to know.

 

Instead of turning Dec Guiding OFF, I'd suggest trying "ResistSwitch" and Dec Guide Mode "North-Only" with your Scope Balanced so as to cause it to Drift South.

 

This is the usual Suggestion provided by the PHD2 Support Forum to overcome big Dec Backlash. And would keep your Dec Error to a Minimum...

Thank you s3igell - I will give it a try. I actually prefer to dither in both axes as it provides better noise rejection. My stars are a little "eggy" in the Dec direction, so, maybe it will kill two birds with one stone.

 

I'll try to remember to finish up this thread with the results of applying your suggestion.

 

Steve

[STEVE333]

As Rick said, PHD does the dithering, BYE simply waits until it is done.  This is not a BYE issue.

 

However, if you want to start imaging sooner you'll need to increase the settle dither at parameter in BYE from it's default 0.20 to say 0.50 and see if this makes a difference.  

Thanks Guylain - I actually increased this value to its max of 1.00, but, the problem persisted.

 

I think part of the problem is that I'm imaging targets that are very low in the South.  Last nights target started at only 10 deg above the horizon!  Atmospheric refraction may be playing some role in the apparent Dec drift.  However, I need a few targets as low as this in order to be able to capture 40 targets that are primarily Southern Hemisphere targets.

 

Steve

[admin]

At 1.00 PHD is still 40% (1.00/2.55=40%) away from the new target location... I would not even consider dithering to be complete at this value so imaging will start while PHD is not yet done dithering.

[STEVE333]

At 1.00 PHD is still 40% (1.00/2.55=40%) away from the new target location... I would not even consider dithering to be complete at this value so imaging will start while PHD is not yet done dithering.

Good point Guylain - I'll make sure to set the settle dither at parameter to a more reasonable value (0.5 or less) for my next attempts.

 

Steve

[STEVE333]

At 1.00 PHD is still 40% (1.00/2.55=40%) away from the new target location... I would not even consider dithering to be complete at the value so imaging will start while PHD is not yet done dithering.

Good point Guylain - I'll make sure to reduce the settle at parameter to a more reasonable value (maybe 0.25) when I start using the Dec guiding.