Calibration message about too few steps

[Paul Patterson]

I am new to guiding, auto guiders and PHD2.   I'm using a Loadstar X2 connected to an IOptron 60EC. I've noticed the last couple of times I been out, I get a message after calibration is completed and I get the green crosshairs.  I meant to do a print screen but forgot before shutting down.  Basically it says something to the effect " Too few steps, questionable accuracy". I know the mount is moving and can see the progression of it moving the star in each direction during the calibration.

I've been proceeding but last time out I click on it and behold it now asks if I want to accept the calibration data or load a previous one.   

So my questions are what setting(s) in PHD2 is causing this message that I should adjust?  I'm thinking  the message is indicating that the stepped moves it makes along a direction is reaching > 25 pixels more quickly than expected. I'm using a 71mm William Optics doublet for the guide scope (430mm fl). Second question is what is PHD2 using for calibration if I have never selected to use current calibration or previous calibration from this message? 

I took recommendations from several people who use the same mount and PHD2. I have in the ADVANCE SETUP > MOUNT, the calibration steps (ms) set at 3500. 

RA agr 25, Hys 20, RA min mo .15

DEC min mo .15, scope mx ra 250, mx dec 150

Thanks

Paul

[bw_msgboard]

Please read the online help/documentation – it’s pretty well spelled out in there.  It’s in the ‘Trouble-shooting and Analysis’ section or just look in the index for ‘Calibration sanity check.’  If that doesn’t answer your questions, we’ll be happy to fill in the blanks.

 

Bruce

 

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[Paul Patterson]

Bruce,

   Thanks for section to look at. So it seems (as I thought) that the calibration steps are too high.  I'll experiment with that, thanks

Paul

[bw_msgboard]

Glad it made sense to you.  If you use the “new profile” wizard to set up your gear choices, it will automatically set a calibration step-size that is likely to work well, in addition to setting some default guiding parameters for you.  If you haven’t done that, you might want to back up and try it that way.  Recommendations for settings from other users are likely to be useless unless their image scale is close to yours.  So you might also want to get on the latest release and read the section on using the Guiding Assistant.

 

Good luck.

Bruce

 

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[Paul Patterson]

Thanks Bruce.  I did download the 2.5 version and installed it.  Went out the other night and went through the profile wizard and yep made all that head scratching go away.  It calculated 2000 for the calibration steps and sure enough PHD2 was much happier with the results. After a bit of guiding I ran the "guiding assistant" and took it's recommendations.

Most of the images looked pretty good... had some that seemed like PHD was erratic.  Did some reading through the documentation.  The wizard had selected 1 sec exposure time for the guide camera.  It was a 60+ full moon and suspect from the documentation that I may want to bump that up to about 2 seconds.

I know too that a lot of the corrections would level out if I had done a drift alignment rather than using the polar scope in the CEM 60EC mount.

Paul


On Monday, April 27, 2015 at 1:36:12 PM UTC-4, Paul Patterson wrote:

[bw_msgboard]

I’m glad you’re making some headway now, Paul.  Ironically, the wizard doesn’t currently choose an exposure time setting, so the 1-sec value is just the default setting for PHD2, same as PHD1.  I agree, you should experiment with longer exposure times, mostly to help avoid chasing the seeing.  As you start looking at your guiding performance, you’ll probably want to focus on the graphical tools in the app, paying particular attention to the RMS values for the star movement.  You’ll also benefit from using Andy’s PHDLogView app which lets you analyze the data after the fact.  Guiding performance is strongly affected by seeing conditions at your location, so don’t get fooled by randomness. <g>  That generally means looking at performance over extended periods of time and being careful about analyzing the results.  Here’s a common pitfall, something I’ve done many times over the years:

1)       Watching the guiding graph with one eye, I notice things are going badly

2)       I make a change to a guiding parameter and things quickly get better.  Aha!

3)       Some time later, I notice things are going poorly again, so I make another change

4)       It gets better!  Aha!

 

What’s going on?  Nothing useful – I just happen to be noticing intervals of bad seeing which then revert to normal.  All my parameter twiddling isn’t accomplishing anything other than to confuse myself.   It’s a tough hobby. <g>

 

Bruce

 

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From: open-phd...@googlegroups.com [mailto:open-phd...@googlegroups.com] On Behalf Of Paul Patterson
Sent: Wednesday, April 29, 2015 6:09 AM
To: open-phd...@googlegroups.com
Subject: Re: Calibration message about too few steps

 

Thanks Bruce.  I did download the 2.5 version and installed it.  Went out the other night and went through the profile wizard and yep made all that head scratching go away.  It calculated 2000 for the calibration steps and sure enough PHD2 was much happier with the results. After a bit of guiding I ran the "guiding assistant" and took it's recommendations.

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