Guiding fails West of meridian

[Jeffrey Jongmans]

Hi all,

I have a problem with guiding West of the meridian. The guidestar is pushed out of the guidebox, because the guidedirection needs to be opposite. I really need some help with getting this right.

My settings are

ACP
Guide sensor configuration: Off-Axis Pickoff
Guide sensor rotation angle: 0.0 (I determined this angle with the help file, star movement is equal to main CCD)

SiTechExe (Mount ASCOM driver)
Reverse Guide Mode when looking East (DEC) = OFF
Reverse RA Guide Mode when looking East (RA) = OFF

Maxim
Control via: ASCOM Direct (Mounts ASCOM driver selected)
On Pier Flip: Do Not Change
Auto Pier Flip: OFF
Pier Flip: OFF
Auto Scope Dec: OFF


My routine is:
1. I slew to position East of meridian
2. I calibrate guider in Maxim (I checked for successful calibration)
3. I calibrate guider in ACP with CalibrateGuider.vbs script (I checked for successful calibration)
4. I run a plan for an object West of the meridian
5. Guiding fails: guidestar pushed out of guidingbox


What am I doing wrong here?? I followed the manual thoroughly. I also tried various combinations of the settings, including the guidescope configuration, without success.

Thanks,

JJ

[Jeffrey Jongmans]

Additional question:

What needs to be selected for the ASCOM Direct setting Maxim?
1) ACP Telescope Hub (ASCOM)
2) Mounts ASCOM Driver (SiTech DII Telescope in this case)

[Bob Denny]

Yes, I have been talking to SiTech and PlaneWave (which uses a derivative of SiTech). SiTech's pulse guide acts differently, and the author Dan Gray has a point that he is right and everyone else is wrong per the ASCOM Specification. I attended the ASCOM online meeting yesterday and brought this up. Platform 6.1 was just released yesterday so the docs won't be updated for a bit. We have to decide what the correct behavior is anyway.

By trial and error online with a PlaneWave customer I was able to get things going by setting the "Reverse Dec PulseGuide Commands Pointing West" and leaving the other reversal checkboxes off. Then I had to change AcquireSupport to reverse Y instead of X in MaxIm when looking West. There are probably other combinations of reversal switches in STI and reversal logic in ACP. I believe that you don't have all of the reversal switches that PlaneWave put in. These reversals are enough to drive me looney. Dan Gray was going looney while talking about it too.

The things to play with are the reversal switches in SiTech as well as the this line in AcquireSupport.wsc:

Camera.GuiderReverseX = Util.GEMWestOfPier

you can try

Camera.GuiderReverseY = Util.GemWestOfPier


Where is your observatory (I know you are in the Netherlands)? I could get on and try some combinations till we get it.

[Jeffrey Jongmans]

I did some trail and error (for a long time), but I think it works...

ACP
Guide sensor configuration: External Guide Scope (but we are using OAG)
Declination comp: OFF

SiTechExe (Mount ASCOM driver)
Reverse Guide Mode when looking East (DEC) = ON
Reverse RA Guide Mode when looking East (RA) = OFF

Maxim
Control via: ASCOM Direct (Mounts ASCOM driver selected)
On Pier Flip: Do Not Change
Auto Pier Flip: OFF
Pier Flip: OFF
Auto Scope Dec: OFF

So we need to select a guidescope instead of OAG in ACP. Also we needed to disable declination compensation in ACP.
And we needed te enable reverse Y (DEC) in Sitech

I did an image in East with success
I did an image in West with success
Scheduler did an image in East with succes

Now I have to wait untill scheduler will start an exposure in West, let's hope it'll work...

[Bob Denny]

Ha ha "for a long time" ... yes. Do you have a rotator on that system? If not, then yes you need to select Guidescope. Thanks for the info on the rest of it. I am tracking this for some additional reversal controls in ACP in the next release. That should REALLY confuse people!!!

[Jeffrey Jongmans]

So I had successful night with scheduler and ACP. Guiding east and west of the meridian without problems.

So tonight again clear sky, so scheduler took of with a session, auto-focus, starting autoguider... Guess what.. Guiding failed again, not the wrong direction but guidepulses aren't aggressive enough. Same settings as yesterday, now it doesn't work. I'M GOING CRAZY!!!

EDIT: I recalibrated guiding in Maxim and ACP again (East of meridian). Guiding east is working again, but I have to check if West is also going to be alright. And the next session; do I need to recalibrate again?!?

EDIT2: attached the logfile

[Bob Denny]

You should never have to recalibrate. If the effect of the guide pulses is changing it is a problem with the scope control system. Next time, after calibrating, look at the X and Y scalefactors in MaxIm and see if they are changeing "a lot". If so something is going on with your scope controller. or your mount (I hope not).

[ebenson]

Hi Jeffrey,
This may not be your problem but make sure you have "Enable simultaneous corrections" in Maxim turned OFF. My mount, a Planewave A200HR using the PW adapted Sitech controller, will ignore DEC corrections if this is on. It was really dumb luck I "discovered" this when getting the mount to work!

BTW my settings are all bog standard and it guide OK on both sides of the meridian from ACP:

ACP
Guide sensor configuration: OAG (I also have a rotator)
Declination comp: ON
Telescope needs local topocentric coords: ON
Adjust coords for atmospheric refraction: OFF


SiTech (PlaneWave STI) - Mount ASCOM server
Doesn't have these two settings - must be OFF by default.
Reverse Guide Mode when looking East (DEC)
Reverse RA Guide Mode when looking East (RA)

I think these are right although I'm not totally sure, hopefully they don't clash with the ACP settings.
Nutate Coords: OFF
Aberrate Coords: OFF
Refraction: ON

The next two are special PW settings I think.
Instant Total Pulse Guiding: OFF
IsPulseGuiding Always returns false: OFF

BTW I just noticed two other check boxes (PW special also?):
GEM Auto Flip Goto: checked
GEM Auto Flip Track: unchecked
which are relevant for another thread about SiTech meridian flipping (or lack thereof), so it can be done!


Maxim
Control via: ASCOM Direct (Mounts ASCOM driver selected)
Telescope: Sitech (so that the FITS header gets coords in it and DEC comp can work)
Declination comp: ON
Auto Scope Dec: ON
On Pier Flip: Do Not Change
Auto Pier Flip: OFF
Pier Flip: OFF


I also just now noticed that I have DEC compensation turned on in two places, I wonder if that is that bad?

Best,
EB

[Bob Denny]

Thanks very much for taking the time to post these details. It is help like this that makes the Comm Center so valuable. I really appreciate it!! These are great. I recommend passing the guiding issue on to PlaneWave. Unlike many other mount companies, they have an active and excellent software team who will be interested in this at a minimum.

One observation:

Telescope: Sitech (so that the FITS header gets coords in it and DEC comp can work)

This is unnecessary, and can result in guiding conflicts if one is not careful. I recommend that no telescope connection in MaxIm be used. ACP manages the declination in MaxIm and also puts the telescope's (indicated) coordinates into the FITS header, whether the image is plate-solved or not. With no telescope connection in MaxIm, the following are irrelevant and therefore not potential problem sources for guiding:

On Pier Flip: Do Not Change
Auto Pier Flip: OFF
Pier Flip: OFF

While this is specifically pointed out in Getting Started Step 12 Autoguiding Overview (see below), it is not in the almost identical caution section of Help/Autoouiding your Mount. I will correct that.

Thanks again for posting this excellent info!

Snap1.png

[Jeffrey Jongmans]

Scheduler started a session a few minutes ago... This time without problems. I think it's working correct now. Still don't know why I needed to recalibrate the system yesterday after a perfect session. Let's hope it stays this way