Category Archives: Technical Notes

PHD: How to Establish a new Equipment Profile

Start PHD software

Click on the connect to equipment icon in the row with looping and auto star select at the bottom left of the screen

When the window opens, instead of connecting to equipment, click the manage profiles drop down, and click Delete. This action applies to the profile name shown in the equipment profile text window. You may need to do multiple deletes if you want to delete multiple profiles.

Click Manage profiles one last time, and click New using wizard.

Follow the wizard prompts, and create a dark library at the end

PHD2: New Equpment Profile when using ASI Main and ASI Guiding Cameras

I could not use the PHD new equpment profile wizard to establish a profile for the guide camera with both a ZWO ASI main camera (ASI6200MM in my case) and an ASI guiding camera (ASI290Mini), connected to the laptop. The main imaging camera pixel size was populated into the wizard until I disconnected the main camera.

Online forum literature says that this is an ASI driver problem, not a PHD problem.

This procedure that I used to make the new equipment profile was:

  • Connect the 290mini to laptop.
  • Do not connect the 6200 to the laptop.
  • Connect the Gemini II control panel to the laptop.
  • Open PHD, click the Connect icon in the lower left corner
  • Manage Profiles: Delete any old equipment profiles
  • Manage Profiles: New using wizard
  • Guide camera: In dropdown, select ZWO ASI Cameras.
  • Is camera already connected to PC? Yes
  • Observe that the un-binned pixel size is 2.9
  • Binning level: 1
  • Enter guide scope focal length: 540
  • Next
  • Mount: In dropdown, select Gemini (ASCOM)
  • Mount already connected: Yes
  • Mount guide speed: 0.50
  • Next
  • AO: None
  • Next
  • Profile name: TV-290mini (or some descriptive)
  • Build Dark Library: Yes
  • Auto restore calibration: Yes
  • Build Dark Library
  • Min exposure time 1.0s
  • Max exposure time 4.0s
  • Frames each exposure time: 10
  • Create entirely new library: Yes
  • Start
  • Follow prompts

Reconnect ASI6200 and resume session.

PHD2: Polar Alignment and Calibration

There are two related questions regarding PA and calibration that have entered my mind over the past year, and I finally have the answer. The longer standing and more perplexing question is how can calibration yield a result that says that my mount’s Ra and Dec axes are not orthogonal? The other is a chicken or egg question regarding polar alignment and calibration – which comes first?

The answers are related, because polar alignment and calibration are interdependent.

The reason that a non-orthogonal calibration result perplexes me, especially a large descrepancy, is I can look at my mount and readily see that the two axes are orthogonal. Scott Losmandy, a highly skilled machinst with decades of experience, doesn’t know how to make a mount any other way. If the axes are mechanically orthogonal, then how can calibration yield a non-orthogonal result?

I found the answer to this question, surprisingly, while trying to answer the polar alignment vs calibration question, so lets answer that question first.

Polar alignment comes first, then it might come last. The reason for this answer is that a good polar alignment is a fundemental component of a good calibration result. Without a good polar alignment, drift will be present during the calibration procedure, and the drift will cause a non-orthogonal calibration result.

If polar alignment comes first, then why might it also come last? A resonably precise polar alignment is essential to a good calibration result.

I approach polar alignment in two stages: initial and precision.

Initial polar alignment starts when I put the tripod on the ground facing north. There are many non-precision tools (e.g., compass, smartphone app, polar alignment scope) that can be used at this stage to refine the polar alignment. When more precision in polar alignment is needed, other tools like drift alignment (whether using PHD2’s tool, or not), apps resident in capture software, or hardware/software similar to PoleMaster.

It is when PHD2 DA tool is the precision polar alignment tool, then polar alignment also comes last. In this case, start by using the best on-precision polar alignment tools available. Now do a calibration run, which will likely yield a non-orthogonal result, and then use the DA tool to attempt a precision polar alignment.

If the DA polar alignment was based on a non-orthogonal calibration result, then the polar alignment precision may be compromised. I this case, iterate through calibration and DA polar alignment another time or two to tighten up both results.

PHD2 AutoGuiding Resources

There is a lot of PHD2 information and a lot of tutorials out there on the web. Some are good and others are junk, but how to tell the difference?

I choose to rely on the recognized community experts. Below are links to the only PHD2 resources that I use. Period.

Video Tutorials:

Optimizing Guiding with PHD2, Bruce Waddington

Demystifying the PHD2 Guiding Assistant, Bruce Waddington

Or anything by the primary PHD2 developers, Bruce Waddington or Andy Galasso. Other video tutorials by them may be added later.


PHD2 Best Practices

How to Create a Baseline for PHD2 Guiding Results

Analyzing PHD2 Guiding Logs, A Basic Tutorial

PHD2 Troubleshooting and Analysis, PHD2 Manual


PHD2 Latest Download

PHD2 Log Viewer

DSO Capture: High-level Workflow

The day before

Charge batteries

Check equipment

Select target prepare capture plan

Prepare and save NINA sequence

By sunset

Mount rough polar aligned

Telescope and accessories installed

Data and power cables connected

Sensor rotation set

By sunset +40m

Devices powered up

Software opened

Software and all devices connected

Capture sky or panel Flats and Dark Flats (Alternative 1)

At sunset +40m

Start precision polar alignment

By end of astronomical twilight

Precision polar alignment completed

Initial main and guide camera focused

PHD Calibration and Guiding Assistant Run completed

Target acquisition completed

At end of astronomical twilight

Image capture run(s)

At beginning of astronomical twilight

Stop imaging run

Start capture of sky or panel Flats and Dark Flats (Alternative 2)

By beginning of astronomical twilight +50m

Finish Flat and Dark Flat capture

Continue Dark Flat capture until complete

Close down the session