Sideral Rate error

[Marty Davis]

Hello to the group. I am trying to get my guiding cleaned up. I have two major issues right now.

I do know I am at about the weight limit of my scope, so that may be an issue, but when I go to use the Calibration assistant, I get the following message:

Your mount speed is below the recommended speed of 0.5x sideral. Use the hand controller or mount driver to increase the speed to at least 0.5x sideral. Then click the "Recalc" button so PHD2 can compute a correct correction calibration step-size.

I have looked at the hand controller option on my computer that comes up when I connect and I am at 0.5x, I checked the actual hand controller on my Orion (SynScan 4.x) controller, it only shows sideral, without a speed change. 

This happens when I am my 8" reflector or my 80mm refractor.

The mount is an Orion Skyview Pro GoTo, I have a SVbony guide camera, and that info is all correct in the PHD2 setup, with an ASI120mm guide camera.

I am stumped trying to get rid of this error.

The second issue is a large amount of "walking noise" I increased my dither to 3, but that doesn't seem to help.

When I do a calibration (I have included my log file), I do get an error that my RA and DEC are significantly different, although the axis are at a right angle and not to wonky. Overall, most of my guiding is around .35 RMS error, with an occasional jump up. 

My polar alignment is within the limits (or so I believe) I use SharpCap to do my polar alignment.

This is my log file, any feedback would be appreciated

https://openphdguiding.org/logs/dl/PHD2_logs_EPZh.zip

[Brian Valente]

Hi Marty

The issue that was reported to you was the guide speed, not the sidereal rate. 

We generally recommend 0.5x - 1.0x, yours is about 0.25x

The guide speed is probably set in your EQ5 Series ASCOM driver. You will probably need to look at the software documentation or ask SkyWatcher where that is set. It can be confusing because the hand controller guide speed can often mean the speed *only for the hand controller* and not the software connection

Regarding your other issues, it looks like the root of it is your Declination axis. Compare your well-behaving RA axis (in blue, nicely spaced points) with your Dec axis (in red, notice the clumping). This may be due to backlash or other issues, but if you are maxing out your weight, it could also be very sensitive to mount balance and this could be a symptom of needing to improve your Dec balance

Brian

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[Marty Davis]

Thanks for the info Brian. I am reworking the balance to make sure it is good, but for the life of me I cannot find where to change the sideral rate. I tried with the software con troller form ASCOM, it did not change anything. i reached out to Sky Watcher and they had no idea. I am tempted to attach via an st-4 cable and the auto guide port and see if that works (possibly change it via the cable and then disconnect).

Will let you know what happens when the skies clear again!

[Brian Valente]

Marty you might try a user group dedicated to SW mounts, i'm sure there's plenty on facebook, cloudynights, etc. 

Connecting the mount and guiding with it at a reasonable guide speed is something I'm sure has been done many times

To view this discussion on the web visit https://groups.google.com/d/msgid/open-phd-guiding/ae2224fc-3bf9-4ef8-a990-7c44a43c4f41n%40googlegroups.com.

[bw_m...@earthlink.net]

I think you need to be careful with terminology here because asking people a garbled question is likely to just be confusing.  You aren’t trying to change the sidereal rate – the sidereal rate is the rate at which distant objects in the sky appear to rotate from east to west.  It is what it is.  What PHD2 is telling you is that the GUIDE SPEED of the mount is set too low.  That guide speed is commonly expressed as a fractional multiple of the sidereal rate – like 1x, 0.5x, 0.25x, etc.  Your mount’s ASCOM driver is telling PHD2 that the guide speed is set to 0.25x sidereal and PHD2’s subsequent calibration produces the same result.  So you should be looking in the reference material or on the mount support forum for how to change various operating speeds of the mount – especially the guide speed.  The default guide speed on most mounts is 0.5x sidereal.

 

Bruce

 

From: open-phd...@googlegroups.com <open-phd...@googlegroups.com> On Behalf Of Marty Davis
Sent: Thursday, November 9, 2023 7:35 PM
To: Open PHD Guiding <open-phd...@googlegroups.com>
Subject: Re: [open-phd-guiding] Sideral Rate error

 

Thanks for the info Brian. I am reworking the balance to make sure it is good, but for the life of me I cannot find where to change the sideral rate. I tried with the software con troller form ASCOM, it did not change anything. i reached out to Sky Watcher and they had no idea. I am tempted to attach via an st-4 cable and the auto guide port and see if that works (possibly change it via the cable and then disconnect).

Will let you know what happens when the skies clear again!

On Thursday, November 9, 2023 at 3:18:34 PM UTC-5 bval...@gmail.com wrote:

Hi Marty

 

The issue that was reported to you was the guide speed, not the sidereal rate. 

 

We generally recommend 0.5x - 1.0x, yours is about 0.25x

 

The guide speed is probably set in your EQ5 Series ASCOM driver. You will probably need to look at the software documentation or ask SkyWatcher where that is set. It can be confusing because the hand controller guide speed can often mean the speed *only for the hand controller* and not the software connection

 

Regarding your other issues, it looks like the root of it is your Declination axis. Compare your well-behaving RA axis (in blue, nicely spaced points) with your Dec axis (in red, notice the clumping). This may be due to backlash or other issues, but if you are maxing out your weight, it could also be very sensitive to mount balance and this could be a symptom of needing to improve your Dec balance

 

 

Brian

 

 

 

To view this discussion on the web visit https://groups.google.com/d/msgid/open-phd-guiding/ae2224fc-3bf9-4ef8-a990-7c44a43c4f41n%40googlegroups.com.

[mj.w...@gmail.com]

Hi Marty

1)  Left to itself, with no guiding, the mount will move in RA across the sky at the Sidereal Rate.

The Guide Rate briefly slows and speeds up the mount, to keep the guide star centred.

In your case, the Guide Rate is slowing and speeding up by 25% of the Sidereal Rate.

At least 50% is recommended.

2)  The lumpy Dec in the Cal can be improved by clearing Dec Backlash before Calibrating - see the PHD2 Instructions.

Michael

Wiltshire UK