SGP 4 64bit + PHD2 4.6.10 issues

after upgrading from older version of PHD2 to 2.6.10 under SGP 4 (64bit) I suddenly start encountering issues I never had ever with PHD2 or SGP

  1. failure to start guiding - both forced by sequence and by manual start

    • by sequence SGP slews platesolves and trys to restart guiding - the camera loops and there is a trace of RA and DEC lines created in the graph - the guide numbers remain at 0.00 for all and SGP remains waiting for the sequence to start … until it times out

    • by manual start - same as above - start looping hit MS guiding star select and guide - the graphs populate but numbers remain at 0.00

Both can be fixed by manually hitting loop again and forcing a guide start

  1. random stops of guiding - i came back after making coffee to find egg shaped stars - I checked guiding and realised it had stopped and actually there was an error message on the ASi174MM saying camera could not be found

Never encountered any issues with PHD2 until this version

Logs available if needed



any known issues with ASCOM and 64 bit SGP 4??

now my moonlite nitecrawler stopped responding to SGP4 mid sequence

this is infuriating!

Hey Simon,

If you just run PHD2 independently of SGP do you see the same issues?

And when you start guiding is is selecting / highlighting guide stars? The only time I’ve ever seen the guide lines remain at 0,0 is if PHD2 has locked onto a hot pixel (which obviously never moves and so requires 0 guide corrections).

Also did you happen to update the ZWO drivers at the same time? Whenever I do that it switches which camera is associated with which ASCOM device, and so confuses PHD2 and SGP (i.e. they often both try open/use the same camera which causes PHD2 to do nothing when asked to guide).


Hi Simon

i’m running both of these versions without issue. You might doublecheck you have the latest drivers and ascom for ZWO cameras. I think 2.6.10 PHD2 did incorporate ZWO’s latest SDK


Hi Simon. There have been issues reported with this, not sure if anything has been done, but check out this thread -

I’m running 64-bit and latest 6.5 SP1 without issue. You have made several changes, including switching to 64-bit SGP, which forces it to use the 64-bit drivers for your devices. I have seen issues similar to yourself… when it was a camera download hang - but the diagnostics in PHD2 are poor and in one case, it was because the cable had pulled out, but it usually was due to some driver issue. I am using QHY, whose ASCOM driver is not the best, so I have started to use PHD’s own QHY driver, with better success. (SGP has to use an ASCOM driver). As said elsewhere, try a middle setting for the USB speed settings, so they all play happily together

Hi Brian - yep all latest SDK

its liable related to PHD2 as that was what I updated - def not hot pixel - darks used for camera and I can see it chooses stars - the graphs populate with the RA/DEC lines but the numbers remain at 0.0 - and SGP looks like its waiting for PHD2 to indicate it restarted guiding

of course now its cloudy till early next week so I cant test by rolling back to 32bit :slight_smile:

wow yup this sounds familiar :frowning:

I’ll need to have a thorough read of that … damm!

confirmed - the solution is in the older ZWO drivers
SGP works fine with older zwo drivers as in the link posted (

as I am a member of the test team for ZWO I am currently discussing the content of these threads with them now as a defect



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I seem to be a member of the test team for QHY, 10Micron, Paramount, Rainbow, ZWO, StarlightXpress and Optolong :slight_smile: