#ASCOM #iexos-100 PHD2 Guiding Issues #iEXOS-100 #ASCOM



Complete beginner at the whole guided imaging and I am totally stuck. I cannot get PHD2 to calibrate. I have tried numerous suggestions from here and other forums, but it just wont calibrate. The issue seems to be that PHD2 will not control the mount. I am using ASCOM driver connected through wifi to my Windows 10 laptop.

1. ASCOM diagnostics pass without failure

2. POTH Hub connects and allows me to control the mount using the sw controls

3. both Explorer Stars app and Stellarium allow me to slew the mount to targets when connected via the POTH Hub

But when I am in PHD2, the mount connects, but I cannot slew using the manual guide controls, nor will it calibrate - it just climbs to over 50 west steps and then fails when I run calibration

What am I doing wrong here - really could use some help :(

info on setup:

Mount is IEXIOS PMC 8 -100 connected to laptop via wifi

Guide Camera is ZWI Mini 120mm connected to laptop via USB cable - I am not using a cable from the camera to the mount

Guide Scope is Orion 30

Lloyd Simons <simonsl23@...>


Guiding over WIFI is notoriously unreliable. I would connect the mount to your PC by USB and connect via serial. Also, make sure you connect to the poth hub in phd2, not the mount.

Hope this helps.
Lloyd Simons
Mattawan, MI
Telescopes: Astrotech AT72ED II, Orion 8" Dobsonian, Tectron 15" Dobsonian, Celestron Super Polaris C8
Imaging Camera: Canon T3i
Guide Camera: QHY5L-IIM with a 100mm CS Mount Lens
Mounts: iExos-100 PMC-8, Vixen Super Polaris
Mount Control: KODLIX gn41 mini PC, Explorestars on a Lenovo Tab 2 A10-70F Android 6.0
Software: N.I.N.A. for imaging, PHD2 for guiding, Sharpcap for PA, Cartes du Ciel, PixInsight

Chris Tardif

Things I learned the hard way:

1. Double check focus of guide scope...
2. Try to aim and center the guide scope and the main scope at the same target as far away as possible.  I use an antenna about 9km from my house during the day.
3.  Calibration of PHD has to be done at a low angle..I remember it complaining to me once when I tried to calibrate it while pointing straight up.

Mounts: Explore Scientific IEXOS-100 w Celestron CG5 tripod, iOptron CEM 40
Scopes: Explore Scientific FCD-100 ED-102CF, Various Canon lenses, ZWO mini-guidescope, StarField 60mm guide-scope.
CameraASI120MM Mini (mono), Altair GPCAM 130
Control PC: Intel NUC
Loc: 44 -79



I wanted to say thank you. The issue was me trying to run the calibration too close to the North Star!! As soon as I followed your advice and ran the calibration nearer the south horizon, BINGO!! First run was a bit off (RMS Total of over 2). Second run was much better (RMS of around 0.5) 

Still a huge amount to learn, but now I can get images and have a baseline, I can build on this.

Thank you to everyone for the advice ,you have no idea how much it helped!!!

Jim McKee

I'll add my two cents.  Glad to hear you had such good guiding the second time around.

1) I have focus dialed in.  But I just made sure my gain for my ZWO Guide Camera was set in PHD2 camera settings not the slider.  The slider is more like gamma.  There is a setting in the brain part of PHD2 where I set the guide camera to Unity Gain.  It took stars from 30db SNR to 70db SNR with no saturation

2) I agree, I have managed to get both pretty close to the same target centerline between OTA and guidescope.

3) I am going back to look at best PHD2 target star calibration position.  If I remember correctly, it says that calibration should be done within 20 deg of the celestial equator, but that requires more research on my part.

4) I use Sharpcap to get PA.  I like the fact that Sharpcap gives a right/left/up.down metric.

5) I marked the RA axis with reflective tape pointers to define my physical  home position (just a little off of weight down position).   It made my EXOS2 perfect for GOTO’s.  Target is always in camera frame first time.

Scope:        Orion EON 115mm APO
:      ES EXOS2-GT w/ PMC-8
Cameras:   ZWO ASI 071MC Pro, Canon 6D Mk 2, Canon 7D2,  EOS 60D Asto Modified
          Canon EF 100-400mm f/4.5-5.6L IS II
Misc:          TELRAD, ZWO ASI120MM Guide Camera, Astromania 60mm Guidescope, Senso Sesto Focus Motor
Software:   EXPLORESTARS IOS & WIN, Stellarium. NINA,  APT, DSS, PixInsight, Photoshop CC
Computer:  Dell Latitude E5450, Windows 10

Wes Mcdonald


PhD advises you to have calibration within 10 or so degrees of Dec =0.   Also you should be a few hours off of Polaris in RA.  Something like south east at 90-lat altitude is good.  

In practice things work pretty well so long as you are not near the North Pole.  

Glad you got it going


Wes, Southport NC
PMC-8, ES ED 127, 10" LX200GPS, Astro-Tech 8" Newt, ETX-90
Polemaster, Orion ST-80 and SAG
Electrical Engineer, Retired