Mesu + PHD2: ST4 vs ASCOM calibration

[NigeB]

Hello All,

Having used the ST4 cable and "on camera" mount connection in PHD2 from day 1, I thought I would try switching over to ASCOM guiding - as much as anything else, I'd like to get rid of a cable. Now I'm seeing something odd during the PHD2 calibration process.

If I use the ST4 cable and PHD2's "on-camera" mount setting, then my East-West and North-South calibration proceeds as expected, with about 12 steps needed in each axis to reach a guide star displacement of ~26 pixels. 

However, with guiding via ASCOM (I switch over to mount setting "SiTechDll Telescope (ASCOM)" in PHD2, and physically remove the ST4 cable just to be sure), the calibration behaviour is different - the E-W phase is still takes ~12 steps to displace the star through ~26 pixels, but in the N-S phase, the guide star rate of movement is at least double that - completing calibration in around 6 steps. Guiding looks OK, but I really want to understand where this factor of ~2 in step size is occurring.

I'm using PHD2 v2.6.4 (but the behaviour was the same with v2.6.2). SiTech.exe version 0.92G, ASCOM 6.2.0.2774 on Windows 7 (32 bit).  PHD2 reports the SiTech.Dll is version 1.5c. I notice that in the ASCOM platform diagnostics (and also when I click on "About" in the ASCOM telescope interface via Cartes du Ciel) the file ASCOM.SiTechDll is listed as version 1.0.0.0.

I've spotted that while my RA encoder is set to "Polite Mode" in SiTech.exe, the Dec was set to "Ignore", so I'll try changing that to Polite. Also in SiTech.exe the "ASCOM AxisRates to R/A and Dec" box is not checked. Finally, I checked PHD2's settings under "Algorithms", and the mount guide algorithms under "Hysteresis", "Lowpass", "Lowpass2" and "Resist Switch" are very similar- the only difference being "Minimum Move (Pixels) is set to 0.25 in RA and 0.20 in Dec for "Hysteresis", and 0.20 for RA , 0.25 for Dec under "Resist Switch". For all other settings, the minimum move is 0.20 pixels for both RA and Dec. 

Am I missing something? Given how few clear nights we have at the moment I'd like to identify anything else to try when the next opportunity arises.

Thanks,

 

Nigel

[RayD]

8 minutes ago, NigeB said:

Hello All,

Having used the ST4 cable and "on camera" mount connection in PHD2 from day 1, I thought I would try switching over to ASCOM guiding - as much as anything else, I'd like to get rid of a cable. Now I'm seeing something odd during the PHD2 calibration process.

If I use the ST4 cable and PHD2's "on-camera" mount setting, then my East-West and North-South calibration proceeds as expected, with about 12 steps needed in each axis to reach a guide star displacement of ~26 pixels. 

However, with guiding via ASCOM (I switch over to mount setting "SiTechDll Telescope (ASCOM)" in PHD2, and physically remove the ST4 cable just to be sure), the calibration behaviour is different - the E-W phase is still takes ~12 steps to displace the star through ~26 pixels, but in the N-S phase, the guide star rate of movement is at least double that - completing calibration in around 6 steps. Guiding looks OK, but I really want to understand where this factor of ~2 in step size is occurring.

I'm using PHD2 v2.6.4 (but the behaviour was the same with v2.6.2). SiTech.exe version 0.92G, ASCOM 6.2.0.2774 on Windows 7 (32 bit).  PHD2 reports the SiTech.Dll is version 1.5c. I notice that in the ASCOM platform diagnostics (and also when I click on "About" in the ASCOM telescope interface via Cartes du Ciel) the file ASCOM.SiTechDll is listed as version 1.0.0.0.

I've spotted that while my RA encoder is set to "Polite Mode" in SiTech.exe, the Dec was set to "Ignore", so I'll try changing that to Polite. Also in SiTech.exe the "ASCOM AxisRates to R/A and Dec" box is not checked. Finally, I checked PHD2's settings under "Algorithms", and the mount guide algorithms under "Hysteresis", "Lowpass", "Lowpass2" and "Resist Switch" are very similar- the only difference being "Minimum Move (Pixels) is set to 0.25 in RA and 0.20 in Dec for "Hysteresis", and 0.20 for RA , 0.25 for Dec under "Resist Switch". For all other settings, the minimum move is 0.20 pixels for both RA and Dec. 

Am I missing something? Given how few clear nights we have at the moment I'd like to identify anything else to try when the next opportunity arises.

Thanks,

 

Nigel

Have a look on the Sitech website Nigel.  Dan has very recently released an updated firmware which fixes this.  I had the same and it is fine after installing the new version.

[NigeB]

Excellent, Thank You Ray! I looked at the firmware change log but didn't see anything that seemed to be related to the problem - so I stayed put. Clearly that's not the case. Great to hear that I'm not alone, and it's solved. Right then - just a few more weeks until the next clear night to try it out...

Thanks Again

Nigel

 

[ollypenrice]

If it ain't broke...

Olly

[RayD]

3 minutes ago, ollypenrice said:

If it ain't broke...

Olly

That's the trouble Olly, it was with the Sitec controller!

Nigel the link to the updated version is below

http://siderealtechnology.com/SiTechSetup092ge.exe

[NigeB]

Fantastic, thanks Ray - have just updated to 0.92ge. And the hole in the cloud has closed up.

Question - how did you find out about that version? The version which is linked on the SiTech front page is 0.92g.

Thanks again

Nigel

[RayD]

35 minutes ago, NigeB said:

Fantastic, thanks Ray - have just updated to 0.92ge. And the hole in the cloud has closed up.

Question - how did you find out about that version? The version which is linked on the SiTech front page is 0.92g.

Thanks again

Nigel

No problem at all Nigel.  I joined the Sitec and Mesu Yahoo groups when I got mine, which has been really helpful.  For this particular issue I posted on the group and also emailed Sitec and Taj got back to me really quickly.

Worth joining if you haven't already.

[swag72]

Here's something I don't understand - How can different people use different Sitech versions? Mine does what was said in the OP - Half the number of guide steps in N/S than E/W....... so? Does it guide? Yes it seems to.... so why does this need to be fixed and if Ray has a problem with the Sitech controller that NEEDS an update then we all should............

This sort of thing is getting far too complicated for me...... I just want stuff to work and not have to keep updating firmware  

[RayD]

1 hour ago, swag72 said:

Here's something I don't understand - How can different people use different Sitech versions? Mine does what was said in the OP - Half the number of guide steps in N/S than E/W....... so? Does it guide? Yes it seems to.... so why does this need to be fixed and if Ray has a problem with the Sitech controller that NEEDS an update then we all should............

This sort of thing is getting far too complicated for me...... I just want stuff to work and not have to keep updating firmware  

I don't think it's about NEED Sara.  Currently, with the version you are using, there is an issue during calibration.  However, Sitech is very cleverly picking this up and compensating for it very well.  This is masking the issue and making it work just fine, but it is not not fixing it, hence the error thrown saying your guiding may not be as good as expected, I guess meaning it will try to compensate but may not do it perfectly.

Dan noticed in his code where things were going wrong and released .92ge to fix the problem.

I think if you are happy with the former and the compensation is working fine for you then there would be no need for you to update.  For me things were the same, and guiding etc. was excellent, but I personally just prefer to see a fix than a fudge, and it took no more than 2 minutes to do.

Ultimately I believe the fact that there can be this error in calibration but Sitech can still compensate and guide well is a testimony to the fact that it is actually pretty good.

[swag72]

Mmmmm..... I don't know whether to update it or not......I'm feeling a bit disillusioned with it if I'm honest 

[RayD]

37 minutes ago, swag72 said:

Mmmmm..... I don't know whether to update it or not......I'm feeling a bit disillusioned with it if I'm honest 

I would say if the calibration alert doesn't bother you, Sara, and your guiding is obviously spot on as we all know, then there isn't really a need.  I think .92g fixed a number of issues, but .92ge update was literally just this fix, so would offer no other benefits at all.

Sitech does seem to do a very good job of noticing the problem and correcting accordingly.

[swag72]

Ah yes, but now there's a little devil on my shoulder saying that it *could* (perhaps) be better...... I say that as there are some things that I don't like and I'm not happy with.

[RayD]

7 hours ago, swag72 said:

Ah yes, but now there's a little devil on my shoulder saying that it *could* (perhaps) be better...... I say that as there are some things that I don't like and I'm not happy with.

DO IT, DO IT.....You know you want to 

I have to say I saw a definite improvement in my guiding.  That may have been seeing or otherwise, but it sure was coincidental if so.

[kirkster501]

Do not mess with anything that has software if it is working OK.  Newer does NOT equal better and more often than not introduces new problems.  As Olly says, if it ain't broke don't fix it....