PHD2 Error "Suspicious RA and Dec rates"
Uppie
During calibration I am getting an error “Suspicious RA and Dec Rates”(~9.234 RA and 3.954 Dec). I have a CGE Pro mount and adjusted the Autoguide rate in the hand control for Dec to a higher setting but it had no impact. I recently switched from MaxImDL to SGP and PHD2 for guiding. I have never had a problem guiding with MaxImDL. In fact, I went back to MaxIm to test the guiding and was able to get 30 minutes subs without issue. I have accepted the calibration with the error and it worked but not well.
Does anyone know what can cause this issue when using PHD2? I checked the backlash on the Dec worm gear and it appears to be good and not binding. The Dec motor and everything appears to be tight within the housing. I have a permanent setup and my polar alignment is rather good. Additionally, I played with the balance and nothing made a difference. Step size was adjusted down until no movement was noticed in either direction then up until too much movement in both directions and still had the disparity between RA and Dec.
Any suggestions?
bw_msgboard
Well, there’s not a whole lot to work with here, so try the following:
- Be sure you’re running the latest PHD2 release.
- Use the new-profile wizard to set up your configuration, being sure the pixel size and focal length parameters are correct.
- Use an ASCOM connection to your mount for guiding.
- Set the guide speeds on your mount to be either 0.5x or 1.0x sidereal with rates on both axes being the same.
- Choose a star near the celestial equator with an SNR > 10 (displayed in the status bar of the main window).
- Run the calibration.
- If you see an alert, look closely at the details being shown.
- Use the ‘Review Calibration’ tool and look closely at the graph. Do you see a “clumping” of points in Dec near the origin of the graph? Or do you see a similar “clumping” at the far end of the Dec line? These indicate backlash in Dec.
- If you see evidence of these, try the following.
- Use the handbox to move the mount north at guide speed for 5-10 seconds.
- Re-run the calibration
If you are still perplexed by the results, please send us both the debug and guide logs for the session and we’ll try to help out.
Good luck.
Bruce
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Uppie
bw_msgboard
Ok, Scott, I’ll take a look. In the meantime, if you have the opportunity, try the experiment I suggested – move the scope north at guide speed for 5-10 seconds before you start the calibration run.
More later.
Bruce
From: Uppie
[mailto:updi...@verizon.net]
Sent: Monday, April 13, 2015 5:44
PM
To:
open-phd...@googlegroups.com
Cc: updi...@verizon.net;
bw_m...@earthlink.net
Subject: Re: PHD2 Error
"Suspicious RA and Dec rates"
Bruce,
Answers to below:
1. Using v2.5.0
2. Profile set correctly per my system
3. Using ASCOM connection
4. Guides speeds set at 0.5x
5. Guide star at equator and near meridian
6.
7. The alert I receive is Suspicious RA and DEC rates (RA rate is ~9.356 and DEC Rate is ~3.952)
8. No clumping noted
I have attached my guide log and debug log from yesterday.
Thanks for your help,
Scott
On Sunday, April 12, 2015 at 8:47:27 PM UTC-7, Bruce Waddington wrote:
Well, there’s not a whole lot to work with here, so try the following:
1. Be sure you’re running the latest PHD2 release.
2. Use the new-profile wizard to set up your configuration, being sure the pixel size and focal length parameters are correct.
3. Use an ASCOM connection to your mount for guiding.
4. Set the guide speeds on your mount to be either 0.5x or 1.0x sidereal with rates on both axes being the same.
5. Choose a star near the celestial equator with an SNR > 10 (displayed in the status bar of the main window).
6. Run the calibration.
7. If you see an alert, look closely at the details being shown.
8. Use the ‘Review Calibration’ tool and look closely at the graph. Do you see a “clumping” of points in Dec near the origin of the graph? Or do you see a similar “clumping” at the far end of the Dec line? These indicate backlash in Dec.
9. If you see evidence of these, try the following.
a. Use the handbox to move the mount north at guide speed for 5-10 seconds.
b. Re-run the calibration
bw_msgboard
This is pretty interesting, Scott, not something I’ve seen before. Let me start by reviewing why PHD2 is squawking at you. It looks like you have set the guide rates on both axes to be 0.5x sidereal, which is fine. With that guide speed setting, calibration on a perfect mount would produce a dec guide rate of 7.5 arc-sec/second. That’s independent of pixel size, focal length, all of that stuff. If the perfect mount was also positioned precisely at the celestial equator during calibration, the RA guide rate would also be 7.5 arc-sec/sec, again assuming your setting of 0.5x sidereal. As you move away from the equator, we expect the RA rate to drop – so our calibration sanity-check machinery expects the RA rate to always be equal to or lower than the Dec rate based on the pointing position. That’s for a perfect mount, of course, and the real world is never that simple. But the basic principles apply.
So let’s look at your results. The Dec rate came out as 5.5 arc-sec/sec, 73% of expected. And the RA rate came out as 10.1 arc-sec/sec, 35% above the expected value. So you can see why we flagged it as “suspicious.” <g> I agree with you, there’s no obvious clumping at the ends of the calibration legs, so this doesn’t look like the usual backlash problem. The graph below shows the behavior of the mount during the calibration, and you can see the Dec run (red) is moving the star at a much slower rate than what we see in the RA run. I notice you are using a 650ms step-size, which is large for your image scale. The new-profile wizard or calibration step-size calculator recommends a step-size of 400ms. Is that because you can’t get the star to move with the lower step-size? I wonder if you have some kind of stiction problem on the dec axis – I’m not an engineer, so that’s just a thought. Also, I guess we have to assume the guide rate is really correct on both axes, the 0.5x rate the ASCOM driver reports. I’d also suggest trying a guide speed of 1x sidereal – that might help with stiction as well.
With all of that said, the actual guiding results you have don’t look bad to me. The runs were only 11 and 10 minutes, too short to say a whole lot – but the total RMS star displacement is around 0.8 arc-sec, with similar values in both RA and Dec. I would expect you to get round stars with these results. I can tell you there are lots of people who don’t do this well. J At that level, you may actually be guiding at the level of your seeing. So if you ignore the calibration alert, are you actually unhappy with the guiding results? Do you have evidence that your seeing should allow substantially better results than this? If you are getting good images, you may want to disable the calibration alert warning and just forge ahead.
Let me know if you have other questions…
Good luck.
Bruce
From: open-phd...@googlegroups.com [mailto:open-phd...@googlegroups.com] On Behalf Of Uppie
Sent: Monday, April 13, 2015 5:44
PM
To:
open-phd...@googlegroups.com
Cc: updi...@verizon.net;
bw_m...@earthlink.net
Subject: Re: PHD2 Error "Suspicious RA and Dec rates"
Bruce,
Answers to below:
1. Using v2.5.0
2. Profile set correctly per my system
3. Using ASCOM connection
4. Guides speeds set at 0.5x
5. Guide star at equator and near meridian
6.
7. The alert I receive is Suspicious RA and DEC rates (RA rate is ~9.356 and DEC Rate is ~3.952)
8. No clumping noted
I have attached my guide log and debug log from yesterday.
Thanks for your help,
Scott
On Sunday, April 12, 2015 at 8:47:27 PM UTC-7, Bruce Waddington wrote:
Well, there’s not a whole lot to work with here, so try the following:
1. Be sure you’re running the latest PHD2 release.
2. Use the new-profile wizard to set up your configuration, being sure the pixel size and focal length parameters are correct.
3. Use an ASCOM connection to your mount for guiding.
4. Set the guide speeds on your mount to be either 0.5x or 1.0x sidereal with rates on both axes being the same.
5. Choose a star near the celestial equator with an SNR > 10 (displayed in the status bar of the main window).
6. Run the calibration.
7. If you see an alert, look closely at the details being shown.
8. Use the ‘Review Calibration’ tool and look closely at the graph. Do you see a “clumping” of points in Dec near the origin of the graph? Or do you see a similar “clumping” at the far end of the Dec line? These indicate backlash in Dec.
9. If you see evidence of these, try the following.
a. Use the handbox to move the mount north at guide speed for 5-10 seconds.
b. Re-run the calibration
If you are still perplexed by the results, please send us both the debug and guide logs for the session and we’ll try to help out.
Good luck.
Bruce
From: open-phd...@googlegroups.com
[mailto:open-phd...@googlegroups.com]
On Behalf Of Uppie
Sent: Sunday, April 12, 2015 6:10
PM
To: open-phd...@googlegroups.com
Subject: PHD2 Error
"Suspicious RA and Dec rates"
During calibration I am getting an error “Suspicious RA and Dec Rates”(~9.234 RA and 3.954 Dec). I have a CGE Pro mount and adjusted the Autoguide rate in the hand control for Dec to a higher setting but it had no impact. I recently switched from MaxImDL to SGP and PHD2 for guiding. I have never had a problem guiding with MaxImDL. In fact, I went back to MaxIm to test the guiding and was able to get 30 minutes subs without issue. I have accepted the calibration with the error and it worked but not well.
Does anyone know what can cause this issue when using PHD2? I checked the backlash on the Dec worm gear and it appears to be good and not binding. The Dec motor and everything appears to be tight within the housing. I have a permanent setup and my polar alignment is rather good. Additionally, I played with the balance and nothing made a difference. Step size was adjusted down until no movement was noticed in either direction then up until too much movement in both directions and still had the disparity between RA and Dec.
Any suggestions?
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