Solar and Lunar autoguiding with PHD2.

[Steve Ward]

I've just seen over on FB a new extension to PHD2 that facilitates both Solar and Lunar autoguiding.

I know some folk are scared of FB but it's the only place I've seen mention of it thus far , and it's a Private group so it's not full of the usual FB types.

 

https://www.facebook.com/groups/1320781201963513.

Edited March 3 by Cornelius Varley
text colour corrected

[Starflyer]

I've been following this too and intend to try it when the sun gets higher and clears the house.  I tried a few time lapse captures last summer and despite having decent PA (fixed pier) I was getting some drift over a couple of hours.

I tried Sharpcap's solar guiding several times and gave up, I couldn't even get a consistent calibration. I considered a dedicated solar guider but they cost a ridiculous amount of money for what they are.

I'm excited to see the results people are getting with this and I'm looking forward to getting some multi-hour captures with no drift.

[Leo Shatz]

Thanks to @Starflyer for bringing this new thread to my attention. For beginners, I highly recommend familiarizing yourselves with the basics and accumulating experience using the standard and well-regarded PHD2. I have developed an extension for the open-source PHD2 project to enable Solar and Lunar guiding, which I've named the Planetary Tracking tool. The aim of this new tool is to enhance PHD2's capabilities, allowing it to lock onto larger celestial objects with circular edges by identifying their center and using it as a "virtual star." This enables PHD2 to maintain its position locked on not only full round disks but also any crescent shape, such as the Moon in its various phases or the Sun during an eclipse.

The tool is in the advanced stages of development and has so far received positive feedback from a few beta testers (including my own limited testing). I have created some initial documentation; however, due to numerous developments and changes to the UI, I've fallen behind in updating the user manual. Instead, I've been issuing periodic updates on the FB forum with instructions for the proper workflow and tuning some of the detection parameters. Currently, the tool is maintained in a separate branch within the forked GitHub repository, and, as of now, binaries are available only for the Windows platform. I'll share more useful information later, but for now, here is the download link for the latest beta 

 https://github.com/Eyeke2/phd2.planetary/releases/tag/v2.6.13-planet.dev6.rc3

[Leo Shatz]

For the folks who don't have access or don't want to use FB, I'm reposting the text of my recent report about my own hands-on experience with the tool to create a timelapse of the solar surface:

I hope the following post will be beneficial to this community and clarify the recommended workflow. Yesterday, I managed to test the PHD2 planetary module for solar imaging with my rig, which includes an APM107/700 APO, Rainbow RST135-E mount, DayStar Quark Chromosphere, and a Player One Apollo-M Max camera for imaging. I also used a 162mm guide scope with a Player One Mars II Mono camera for guiding. The main imaging scope is equipped with a Baader ERF rejection filter, and in front of the guiding camera, I have a stack of Player One 1.25" ERF with a couple of ND1000 filters mounted.

Without the ability to perform precise polar alignment during the daytime, I made a rough alignment using a compass and manually adjusting the mount's altitude. Setting the proper guiding camera gain and exposure times was crucial before starting PHD2 calibration with the planetary guiding module; for me, this was 5 msec and a gain of 35. Finding focus in bright light is challenging—it requires being able to see the computer display and reach the focusing knob. Initially, the Sun's images in PHD2 were blurry with a bright spot in the center and a diffuse glow around it. By adjusting the camera's position inside the focuser, I found the approximate position where sunspots became visible. It's important that your camera settings are not overexposed to assist in achieving optimal focus, which is crucial for the performance of the planetary detection algorithm.

After roughly focusing, I tuned the planetary detection parameters by setting the min/max radii to closely match the solar disk's size, setting the min radius about 10 pixels less and the max radius about 10 pixels more than the actual solar radius. I used the Eclipse mode for detection, which will soon be the sole option in my software for full planetary disk detection (surface feature detection will remain unaffected). Tuning the Edge Detection Threshold is a two-step process: I start with a value that allows the disk to be detected and show the green circle - a good starting point is a middle value. When PHD2 finds the solar disk, it displays its radius, and with the correct guide scope focal length setting, the radius in arcsec should be around 900-1000 (shown next to the radius in the star profile window).

To fine-tune focusing, I toggle from radius display to 'SHARPNESS' in the star profile window by clicking the 'RADIUS' label. I adjusted the focuser knob in small increments and observed the sharpness value peak in the Star Profile window. At this point, the sunspots were distinctly visible. Once the focus was set, I went back to fine-tuning the 'Edge Detection Threshold' by enabling the 'Display internal edges/features' checkbox, which shows the internal contour edges used by the detection algorithm. When set correctly, the red contour should closely follow the solar limb and remain stable without showing random artifacts or jumping 'hairs.' It's best to set this value close to its maximum and ensure that detection remains stable. Lower values may be necessary when the signal is weakened by clouds or when the object becomes thin due to an eclipse or crescent phases.

After achieving focus and stable detection, I ran a PHD2 calibration using the same workflow as for nighttime astrophotography. The choice of guiding algorithms is up to personal preference and experience; some may prove more suitable for solar photography, which will be determined experimentally. My rudimentary polar alignment resulted in a 10.7-degree orthogonality error in PHD2 calibration results. Nonetheless, I started guiding and ran a 1-hour and 40-minute capture session using SharpCap. PHD2 maintained the Sun's center with a total RMS of 0.7 pixels or 2.6". Despite poor seeing and potential tuning needs for my Quark, the session served as proof of concept. I'm sharing the resulting video, which has been stabilized and processed for contrast.

After capturing the movie, I attempted to improve polar alignment by using PHD2's Guiding Assistant tool and manually adjusting my mount's azimuth/altitude. In about 10-15 minutes, I significantly improved the polar alignment (see attached image in the comments). If time allows, I recommend trying to improve polar alignment before your imaging session. A few iterations with the Guiding Assistant, minimizing both RA and DEC drift rates with small mount adjustments, can make a difference.
I hope sharing my experience proves useful to you. Happy imaging and clear skies!

A sample timelapse created using PHD2 Planetary Tracking

Attached below are few screenshots showing PHD2 guiding in action, a screenshot of SharpCap and two different PHD2 calibration results - the worse one was actually used to create the timelapse, and the improved one - after using Guiding Assistant and attempt to tweak the Alt/Az of the mount.

Edited March 3 by Leo Shatz

[Starflyer]

Thanks for sharing this here Leo.

Quick questions; if I use the Guiding Assistant to improve PA do I need to recalibrate after each tweak to the Alt / Az position?

Is it possible to use PHD2's drift alignment feature to help tweak the PA?

 

Cheers 

Ian

[Leo Shatz]

Recalibration is not required during the tuning - the GA will turn off the guiding anyways. Just watch the slopes and trends to minimize the drift. Before adjusting the knobs, exit GA and stop guiding. Turning the knobs too far may push the Sun away from the frame, so be careful. This is an iterative procedure but with some patience it will be rewarding. But, at the end, when you reach low drift rates in both axes, you'll definitely need to recalibrate.

[Leo Shatz]

I wanted to share a quick heads-up about an issue I encountered during my last test session – field rotation. My initial polar alignment wasn’t as precise as it needed to be, leading to noticeable field rotation in the footage. Fortunately, since my total recording time wasn’t extensive, I managed to correct it in post-processing.
This experience was a reminder of the importance of thorough polar alignment, especially for long-duration recordings. Field rotation can subtly affect the quality of our captures, making post-processing more challenging.
I strongly advise dedicating extra time to ensure your polar alignment is as accurate as possible, as I've suggested previously (using Guiding Assistant, or GA in short). A little extra effort upfront can save a lot of time later and significantly improve the quality of our recordings.
Stay sharp, and clear skies!

[Leo Shatz]

Here, I've shared a few screenshots demonstrating the algorithm's ability to accurately locate the Sun as it approaches totality or when the sky becomes a bit hazy. However, don't just take my word for it. You might need to manually adjust the Edge Detection Threshold for increased sensitivity, fine-tune the minimum/maximum radii, or alter the camera's exposure time—all of which can be done through the Planetary Tracking tool. In challenging situations, where detection starts to behave erratically, it's best to stop the guiding (while continuing with the exposures) until the sky and scene conditions improve.
Another crucial piece of advice: practice before the eclipse. I've implemented significant updates to the Camera Simulator in this version of PHD2. These allow you to upload any image (JPG/PNG/FIT/TIF) and fine-tune or test the planetary detection parameters from the comfort of your armchair.
Images are courtesy of Bill Glynn.

[Leo Shatz]

I'm pleased to announce the release of a new custom version of PHD2 with Solar/Lunar/Planetary tracking.

https://github.com/Eyeke2/phd2.planetary/releases/tag/v2.6.13-planet.dev6

I hope this new software release will simplify the interface, making it more user-friendly.

Edited March 14 by Leo Shatz
Fixed attached URL and description text.

[yopero]

On 09/03/2024 at 10:48, Leo Shatz said:

I'm pleased to announce the release of a new custom version of PHD2 with Solar/Lunar/Planetary tracking.

https://github.com/.../releases/tag/v2.6.13-planet.dev6

I hope this new software release will simplify the interface, making it more user-friendly.

@Leo ShatzI think your github link is missing the user and repo bits

[Leo Shatz]

21 hours ago, yopero said:

@Leo ShatzI think your github link is missing the user and repo bits

Sorry, could be some technical issue in my previous post, try this link https://github.com/Eyeke2/phd2.planetary/releases/tag/v2.6.13-planet.dev6

 

[yopero]

On 14/03/2024 at 16:14, Leo Shatz said:

Sorry, could be some technical issue in my previous post, try this link https://github.com/Eyeke2/phd2.planetary/releases/tag/v2.6.13-planet.dev6

 

That link works. Thanks a lot!

[Leo Shatz]

I'm pleased to announce the new software version release v2.6.13-planet.dev7.rc1. The important changes are:

* Add pause/resume planetary detection button to enable handling brief periods of cloud cover and totality during eclipse. Still, if for any reason the object will drift away from field of view, PHD2 won't be able to locate and bring it back to center when resuming. The button is enabled only while guiding is active.
* Integrated UI controls for reviewing and setting the mount's tracking state and selecting tracking modes. Tracking rate should be select as the beginning of PHD2 session - before calibration and guiding.
* Implement logarithmic scaling for the Detection Sensitivity parameter in the Surface Features Detection algorithm. This modification provides a more intuitive and practical control over the algorithm's sensitivity.

Download it here:

https://github.com/Eyeke2/phd2.planetary/releases/tag/v2.6.13-planet.dev7.rc1

[Leo Shatz]

I've added Wiki pages for the project starting with basic information and adding Quick Start Guide for Solar Autoguiding.

PHD2 Planetary Guiding Extension Wiki