Which Version of PHD2 should Use With SGP V


The more I download updates to PHD the more trouble I am having. So in short…Which Version of PHD2 should I use With SGP V I was running PHD2.2.1 dev 8 last night and I got nothing but calibration errors and pulse guiding failures. Everything used to run like a train. Only have a very few nights out of the month to image and I sure don’t feel like messing around all night and getting nowhere.


Upgrading and downgrading PHD2 is unlikely to fix or worsen calibration errors and pulse guiding failures so in that regard it really makes no difference what version you use. Upgrading or downgrading PHD2 will almost certainly not solve whatever problem you are experiencing.

I recommend the latest dev build, available here: http://openphdguiding.org/development-builds/ since the dev builds have the latest bug fixes, feature updates and diagnostic logging. However there are no bug fixes or updates that I am aware of related to calibration errors or pulse guide failures.

My recommendation would be:

  • install the latest dev build of phd2 (not because it is expected to fix anything, but because it has the latest diagnostic logging and phd2 developers will be reluctant to look at logs from old versions of phd2 like 2.2.1 which was released in Feb 2014)
  • when you see a problem, post a message describing the issue in the phd2 forum, and be sure to include a link to your PHD2 debug log as described in Getting Help

With that information we should have a very good chance of being able to identify the root cause of your problem and get things running like a train again.



I agree with whatever @Andy says, but, in general, as indicated in the release notes, PHD2 2.6 is the minimum version.

I also need to take a look at the PHD2 version checker. SGPro 2.5 should have thrown a fit if it detected a version of PHD2 that old…


Andy (& Ken)

As, usual, thanks for your quick responses.

I think the problem I am having is that my mount is SYNTA MOUNT, albeit any
other name like Orion Sirius or SkyWatcher HEQ5 Pro. For the past 8 years I
have been using Chris Rowland’s Celestron Unified Driver 5.1 (no longer on
the ASCOM site). and with

the latest development version of PHD2 (which I am using) - PHD2 2.6.1dev8.
I got 2 warnings the other night from PHD2 using the Celestron Unified ASCOM
5.1 Driver:

  1. "Pulse guiding movement has failed - guiding likely to be ineffective.

  2. “Calibration is based on very few steps so accuracy is questionable.”

So…that was using the Celestron Unified Driver 5.1 which, by the way,
specifically includes the SkyWatcher Mount on the drop-down list of
Celestron Scopes.

This morning I downloaded Chris’s update of the Celestron Unified driver
6.05. After selecting the “Advanced Setup” in PHD2, I tried to connect to my
HEQ5 and

received a warning…“Mount does not support the required PulseGuide
interface” - I was unable to connect to my mount.

I do not get this warning using the Celstron Unified 5.1 ASCOM driver and
can connect to my HEQ5-Pro.

  1. Does this mean that my SYNTA mount cannot be pulse guided any longer?

  2. Can I still use the Celestron version 5 ASCOM driver but get this pulse
    guide error.

I thought in using previous version of PHD2 that I was in fact pulse
guiding…I could see the guide star move N, S, E, & W at about 20
iterations in each direction…

now I get these errors using the exact same equipment. Maybe because I’m 68
years old, but I just don’t understand!

Thanks Andy



There’s a SkyWatcher ASCOM driver recently released on the ASCOM forum which should implement PulseGuide.

Guiding will need the latest SkyWatcher HC firmware. This is available for the V4 HCs but not as yet for the V3 HCs. SkyWatcher say that it will be released soon.

My intent was that the new Celestron driver would continue to support the SkyWatcher mounts but I couldn’t get any information about what was wrong. In the end all I could do was to say they weren’t supported.



Hi Chris,

I have a V3 Hand Controller…am I up the creek with no guiding for now?




It sounds like since the latest ASCOM driver does not work at all (the required PulseGuide interface is unavailable), you’ll have to go back to the earlier ASCOM driver.

If this only happens infrequently, it may not be a problem for guiding. If you post a PHD2 debug log, we can look at it to see how frequently it is happening. Also, the ASCOM driver log file may have some information about why the pulse guide command failed. You’d need to get help from the ASCOM driver provider for help locating and analyzing the ASCOM log, but let’s start with the PHD2 debug log first.

This should be easy to fix by increasing the calibration step size in PHD2. You can use the calibration step size calculator to have phd2 set an appropriate calibration step size for you.

At this point we’re no longer discussing SGP, so it may be better to move this conversation over to the PHD2 forum.



I don’t think the SkyWatcher driver will implement PulseGuide with the current V3 HC firmwre, but no reason not to try.



Hi Chris,

I have just discovered that my V3 SynScan Hand Controller for my HEQ5-Pro
(aka Orion Sirius), starting to fail. It keeps loosing it’s firmware
updates. I was using 3.36 as it was very stable. Now it reverts

back and displays Version 0.00 ! Yet it seems all the functions are working
should anything fail out in the dark…guiding etc…that would be my first

So I am in the middle of deciding on getting a replacement from SkyWatcher.
Their Canadian outlet is just across the water from me in Richmond, B.C.

I believe the Version 4 handset is compatible with my HEQ5-Pro.

As this is going to set me back about $300.00, I would like to know if you
and SkyWatcher will be having another driver update for sure that addresses
the pulse guiding for PHD2 ?

If so I will order a new V3 Hand Controller.


Should I switch to the Version 4 controller in which you already have the
new driver for, or stick with the Version 3 and await the pending driver for

Sorry to bother you on this, but I in a difficult position as it involves
quite a few things that few people can resolve. Many, many thanks in
advance Chris.



I’d go for the V4 HC. I don’t have any inside information but I think
it’s likely that the current V4 HC will get more updates and get them

AFAIK the V3 and V4 HCs are compatible as far as the hardware is concerned.

No personal guarantees of course.



Thank you so much Chris…

Would you believe the Canadian Price is $540.95 (Incl Taxes) !!!

Guess I’ll hit the Buy Now Button but it will really my fingers!!



Wow, even as a fellow Canadian that seems hi. I also have an HEQ5 and have never used tha HC. I started with EQMOD controlled by my laptop. Have you considered this?


Hi Tim,

Well, I like to use the HC sometimes stand alone. How are you guiding. I’m
using PHD2 and it “passes through” my hand controller for connection.

Are you using ST-4 with EQMOD?



Are you sure that isn’t an upgrade kit? Including the motor control board and a couple of stepper motors.

I’ve looked locally and the V3 HC is £159 while the upgrade kit is £350. That’s all V3 HCs. The V4 HC is £149, that’s 277 Canadian.



Thanks for the heads up Chris.

Yea…they screwed up and the Canadian Price of the Version 4 is 246.00

I talked to SynScan Skywatcher Canada with is located near Vancouver B.C.
about 40 miles

across the water from me here in Nanaimo. The Version 3 is no longer
available so it has to

be Version4.

Thank you very much for your help.

Clear Skies Chirs



Hi Randy - I started using ST4 with EQMOD but I switched to Pulse Guiding with EQMOD. One less wire and I find it much more stable. I’m also guiding with PHD2.

Basically, I just set up my Sequence in SGP earlier in the day. In the evening I start EQMOD, SGP and PHD2 and hook up the relavent equipment. I set a start time and go back in the house. I can monitor things using teamviewer or splashtop.

I’ve setup SGP to platesolve so finding my targets is automated.

When I started I was advised to forget the handset and use EQMOD. I do admit that I usually image at home which makes things easier.


Hi Tim,

You are doing the same thing as me. I still like my hand controller should I
just want to poke around visually. You must do your 3 star alignment in
EQMOD as well, correct?

I presume you are using and EQDIR adapter cable as well?

So I did install EQMOD and the ASCOM Celestron EQMOD driver will work with
my V3 SynScan hand controller. The H/C is loosing its firmware revision so I
think it

is “going south”. I have ordered (with much difficulty), a new Version 4
SynScan hand controller. Chris Rowland has, in co-operation with SkyWatcher,
written a new

Firmware revision for the Version 4 H/C that will allow me to use the newly
written ASCOM Celestron Unified Driver Version 6 now on the ASCOM website.
This will allow me

to pulse guide again.

I do not at the moment have an EQDIR adapter cable for my HEQ5-Pro. I tested
EQMOD just in the basement using “PC Direct” on my SynScan hand controller
and it is working.

There seem to be some early posts going back to 2013 or so, concerning using
this method as it has no “self correcting” within the data stream. I
basically recommended that the

mount shouldn’t be left unattended. But like you, I’m using Team Viewer and
when things get going, I come inside and power nap and intermittently go out
and check things.

So I have EQMOD now to play with, but I will probably go with the SYNSCAN
Firmware and new Ceslestron Unified Driver Version 6, along with my new
Version 4 Hand Controller.

Thanks ever so much Tim for pointing out your system and I wish you the
clearest of all skies…



Randy, there are some serious misunderstands here.

I have developed an ASCOM driver for the SkyWatcher mounts. This needs a new version of the SkyWatcher HC firmware to get full functionality. I did NOT develop any of the HC firmware, that’s done by SkyWatcher.

This has nothing to do with the Celestron ASCOM driver. The Celestron ASCOM driver has not changed.

You need to use the SkyWatcher ASCOM driver NOT the Celestron ASCOM driver. The Celestron driver is for Celestron mounts and as the SkyWatcher protocol has evolved it has drifted increasingly far away from the Celestron protocol.

This also has nothing to do with EQMOD. There is no such thing as an EQMOD Celestron driver.



Hi Chris,

I have ordered the Version 4 Handset from SkyWatcher for my HEQ5-Pro Mount.
It should be here by the weekend.

So I should install the following?

  1. SynScan V4 Hand Controller Firmware V4.38.09?

  2. Where do I get your ASCOM driver for the Sky Watcher mount?

  3. I am on Platform 6.2 ASCOM.

Sorry about the confusion…even the distributors in Vancouver are confused.



Hi Chris,

I subsequently searched for the driver you developed and it came up with
SynScan V4 Hand Controller Firmware V4.38.09.

With my Version 3 hand controller I use FIRMWARE V 3.37

I have ASCOM platform 6.2 installed

For a DRIVER, I was using the ASCOM Celestron Driver 5.1 and it offered me a
"drop down box" to select the SkyWatcher Mount.

So I was using 1) FIRMWARE for the Hand Controller and 2) A DRIVER for the

What I don’t understand is that we are now, with the new Version 4 Hand
Controller, going to be using SynScan V4 Hand Controller Firmware V4.38.09.

But what about the ASCOM driver for the mount? Doesn’t the FIRMWARE
install to the Hand Controller and the DRIVER to the Computer?

Are we talking here that the DRIVER and FIRMWARE are now one of the same? If
not, where is the ASCOM SkyWatcher Driver you developed?

Sorry, Feel like I’m going back 10 steps here