Meridian flip, calibration flip

[Lord Beowulf]

Hi All:

My understanding of one of the reasons for using the mount interface (secondary interface) even if you're using on-camera pulse guiding was so that it would detect a meridian flip and flip the calibration.  However, when I do a flip I have to manually tell PHD2 to invert the calibration.  That's somewhat problematic if I don't recall whether I was imaging pre- or post-meridian last.  Is there a setting I'm missing somewhere?  I'm using a Celestron mount if that has any effect on the ASCOM driver.  I'd have to double-check which version of the Celestron driver is assigned to my imaging system, since I use both to control two scopes from one PC.

Thanks,

Beo

[Andy Galasso]

Beo,

Could you please post your log files from a session where you did a meridian flip.  (Instructions)

Andy

[Lord Beowulf]

Hi Andy,

More often than not the flip is for different targets on different nights, but I'm assuming that PHD should still be able to account for that.  I was just reading back through the documentation and saw the statement that "flip calibration will have no effect" if an aux mount is being used.  Does that mean that the dialog won't show up when you try flipping or that it will, but it's ignored.  I know when I was setting up I HAD to use the calibration flip, but it's possible my aux mount wasn't active then.  Depending on how it works, it could be that I'm just doing something I don't need to do and it's being ignored.  The problem is that it's possible to have it wrong and the system will appear to guide fine for a while and then eventually DEC will just take off as it drifts out far enough and starts correcting in the wrong direction.  I guess I could manually toggle and see if it drifts away eventually.  No point in you wasting your time looking at a log file if the problem is the user!  =)

Thanks,

Beo

[Andy Galasso]

Hi Beo,

I'll try to give some detail on how it works. Feel free to ignore the details below :). The take-home message is: calibrate and guide with a mount or aux mount that provides Side of Pier status and everything will just work automatically with no need to manually flip calibration ever.

Now the details:

Side of pier can be queried from the mount or aux mount. It will be reported as East or West.  Side of pier can also be Unknown if the mount or Aux mount cannot report side of pier. For example with an On-camera mount connection (and no Aux mount) side of pier is always Unknown.

When calibration is done the calibration is tagged with the side of pier on which it was done:  East, West, or Unknown.

When guiding is started we look at the current side of pier.   If the current side of pier is opposite the calibration data side of pier, PHD2 flips the calibration.   If the current side of pier or the calibration side of pier is Unknown, then phd2 does not flip the calibration.

If you calibrate with a mount or aux mount that provides side of pier, then meridian flips work seamlessly and automatically.  If you calibrate or guide with side of pier Unknown, then meridian flips require manual flipping of the calibration.

If you have side of pier info in your calibration and you manually flip calibration, then when guiding starts phd2 sees the calibration side mismatch and flips it right back (and guiding resumes properly.)

Andy

[Lord Beowulf]

Thanks Andy,

That probably explains it as I may very well have done the calibration without the aux mount active.  I was going to re-calibrate last night but got into headaches with SGP not plate solving and never made it that far!  I'll give it a shot next time I get some good skies.  Thanks for the detailed explanation though.

Beo

[Rick Kuntz]

I must be doing something wrong.  I see in the guiding graph that the scope is on the East side of the pier pointing West.  When I do a slew to an object on the East side of the meridian (scope now on West side of pier);  the dec takes off unless I do a recalibration on that side.  I tried with the checkbox on and off (reverse Dec output after meridian flip).  I'll have to keep at this and figure it out.

[bw_msgboard]

Hi Rick.  Whenever you change the setting of that checkbox, you *must* then do a fresh calibration – on either side of the pier. Once you’ve got it set correctly, then you can forget about it. In other words, reverse-dec-output is a property of the calibration and it essentially takes effect only when you do a calibration.   If you can’t get it working, post both your guide and debug log files so we can take a look at what’s going on. 

 

Good luck,

Bruce

 

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[Andy Galasso]

On Mon, May 14, 2018 at 10:25 AM, Rick Kuntz <cardi...@gmail.com> wrote:

I see in the guiding graph that the scope is on the East side of the pier pointing West.  When I do a slew to an object on the East side of the meridian (scope now on West side of pier);  the dec takes off unless I do a recalibration on that side.  I tried with the checkbox on and off (reverse Dec output after meridian flip).

If you go through the procedure in the help file under the description of the "Reverse Dec output after meridian flip" setting, you should be able to get it working.  Here's what the help file says:

With the checkbox disabled, calibrate on one side of the pier, then move the mount to the other side.  If you are guiding via ASCOM or Indi or are using an 'aux mount' connection, just start guiding.  If you're guiding only via ST-4 and PHD2 has no scope pointing information, first select  'Flip Calibration' under the 'Tools' menu, and then start guiding.  In either case, if the guiding works normally, leave the box un-checked; but if you see run-away in declination, check the box and repeat the entire procedure, including calibration.

As Bruce says, you need to repeat the procedure including running a new calibration after you find you need to toggle the setting.

You can use the Ra/Dec overlay (View menu) to see which way is RA and which is Dec.

If you have only an ST4 connection (on-camera) and no Aux mount connection then phd2 does not know which side of pier you are on and you'll need to flip the calibration manually each time you do a pier flip (and also have the correct setting for "Reverse dec output after meridian flip")

Andy

[Rick Kuntz]

Thank you for the information.  I surely thought I had done a recalibration after changing the switch but sometime in the observatory in the middle of the night you think you're doing one thing and you remember it wrong.  I'll re-do this procedure again next clear night.  I am using TSX on a MX+ mount, usually with SGP so I wouldn't think the checkbox should be on to reverse the Dec but this is how I first noticed the problem.  I'll give it another try and look closer at the steps; otherwise I'll grab the debug log files.  

Much appreciated.