Proper Setup SGP and PHD with CEM60

A Little Background
I have been following the discussions on the CEM60 Meridian flip issues over the past few months. After iOptron released version 4 of their ASCOM driver and seeing others have had success with the new iOptron firmware and ASCOM driver, I decided to upgrade my CEM60 firmware to the latest versions and install the ASCOM 4.0 driver. At the same time I installed PHD2 version 2.5.

I am new to SGP so I am still working on getting everything setup correctly. I did an initial run about a week ago. My plate solving worked, along with guiding and imaging; although I had balance and cable hanging issues that ruined the images. However, I considered the evening a success because my primary objective was to get working and run a simple imaging sequence. I did not attempt anything that required a meridian flip.

Now for my Question
I have been looking through the PHD2 options (Brain) and see that under the Mount tab one of the options is: Reverse Dec Output after meridian flip. Should I check this option when allowing SGP to perform a meridian flip? I am assuming the answer is Yes, but I am not sure because I really don’t fully understand what things SGP tells PHD after the meridian flip. Also, is there a way to force PHD to re-calibrate after a meridian flip?

I’m hoping for some clear skies in the next day or two so I should have a chance to try out my latest balance and cable routing setup along with any changes I need to make to my PHD setup.

Thanks in advance,


1 Like

Probably not. I would leave it as is and if you find that your Dec correction is wrong after the flip then you may need to enable it. However most drivers tend to take this into account when the flip happens.

No, and you really shouldn’t need to recalibrate after a flip. If you’re connected to the mount in PHD through ASCOM it will automatically scale your Dec calibration for you. But the dec scaling really applies more to slews than flips.



Jared is right, you won’t know until you give it a try. However, you can test it standalone in PHD2 outside of SGP. Here’s what you would do:

  • Open PHD2, connect equipment.
  • Loop exposures, select a guide star.
  • Start guiding, confirm guiding looks ok.
  • Press Loop in phd2 to stop guiding.
  • Slew your mount to the other side of the meridian, doing a pier flip.
  • Find a guide star
  • Click PHD to start guiding.

If guiding is ok, you are done, the setting is correct. If guiding runs away in dec, you need to invert the setting.


Jared and Andy,

Thank you for your quick replies. I will use the method suggested to verify the operation of PHD. Hopefully, the weather will clear and I can get enough of a clear spot to give it a try tomorrow night. It has been a very cloudy and wet spring in Indiana! At least I have had plenty of time to read the SGP manual!

I have my first motorized focuser on the way from Moonlite. Once I get it installed, I’m sure I will be back with more questions.

Clear skies please,