phd2 guiding

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About the Open PHD Guiding Project

The Open PHD Guiding project began in 2009 when Craig Stark of Stark Labs , the author of PHD Guiding and Nebulosity, released the source code of his popular PHD Guiding application. In 2012 the project was picked up by Bret McKee who did a major refactoring of the code, reworking much of the internal infrastructure and introducing the multi-threaded architecture in use by the application today.

In 2013 the project maintenance role transitioned to the current maintainers, Andy Galasso and Bruce Waddington, who have overseen the development of the application since then. The application today is the result of contributions from more than 40 developers and translators. See Help – About in the PHD2 menu for the full list of contributors.

Developers interested in working on the project are encouraged to send pull requests via the PHD2 project page on github , and to participate in the PHD2 Forum . Additional information for developers is available in the PHD2 Wiki .

We are also looking for translators to translate PHD2 and to keep the existing non-English translations up to date.

If you are an experienced PHD2 user, we would sincerely appreciate your help advising and supporting newer users in the PHD2 forum.

The developers would like to add a special acknowledgement of the contribution of the Predictive PEC guide algorithm by the team at the Max Planck Institute, Intelligent Systems.  This contribution from the academic community highlights a benefit of developing astronomy software within a collaborative, non-commercial framework.

News & Resources

December 22, 2023 - PHD2 v2.6.13 Released

December 21, 2019 - PHD2 Best Practices

December 7, 2019 - macOS Catalina

April 26, 2018 - Polar Alignment tool video tutorials

June 12, 2016 - PHD2_Broker package available

Autoguiding a Telescope for Deep-Sky Astrophotography

Below, I’ll explain how to start leveraging the power of autoguiding for deep-sky astrophotography. Many amateur astrophotographers are hesitant to add any additional complexity to an already steep learning curve. But the truth is, autoguiding your camera and telescope isn’t overly difficult to execute.

I’ve been using a small ‘guide scope’ with an autoguiding camera to take longer exposures through my telescope for several years. With the right equipment and a little trial and error, you’ll wonder how you ever lived without it.

Autoguiding improves the tracking accuracy of your telescope mount for astrophotography.

Overview and Quick Setup

To start autoguiding, all you need is a guide camera, a small guide scope, and software to run the camera and utilize the autoguiding port on your astrophotography mount . You can put together a reliable autoguiding package for about $250 USD (see the example kit below).

A simple camera and guide scope package like this will allow you to harness the power of autoguiding for primary imaging telescopes with a focal length of up to 1000mm. Image capture software tools like N.I.N.A, PHD2 Guiding, and the ASIAIR all have autoguiding modes to utilize this feature. 

• Guide Camera: ZWO ASI120MM Mini
• Guide Scope: Astromania 60mm Guide Scope
• Guiding Software: PHD2 Guiding , ASIAIR

To use autoguiding, you must use a computerized telescope mount with an autoguiding port and/or USB port to connect it to the guiding software. Modern equatorial telescope mounts like the Sky-Watcher EQ6-R Pro and strain eave drive mounts like the ZWO AM5 support autoguiding. 

You will also find autoguiding ports on portable star trackers like the Star Adventurer GTi . If you are looking to add a small guide scope package to your existing setup, you can build a system using the components of your choice or invest in a ready-to-go guide scope package. 

Keeping weight to a minimum has many advantages, and a miniature system like the one shown below is an attractive option for beginners. I started out with a small 50mm guide scope package way back in 2011, and this is still a popular starter system for many backyard imagers. 

The ZWO ASI120MM Mini guide camera is affordable and works exceptionally well. 

Basic Autoguiding for Astrophotography Made Simple

I’ll admit that autoguiding can seem a bit daunting in the early stages of building your first deep-sky astrophotography kit. The great news is that more compact and affordable solutions are available than ever.

Below, I’ll offer you some affordable autoguiding solutions that I have used to guide several telescope setups. They’re really not that hard to get up and running, and they can make a big difference to the quality of your images.

The two main software tools astrophotographers use for autoguiding are PHD2 Guiding (which integrates with several camera control software) and the ASIAIR smartphone app. Both are easy to use and allow you to dither your images between each frame. 

The Concept of Autoguiding

Whether you’re shooting with a DSLR or a dedicated astronomy camera, capturing longer exposures means that more light (or signal) can be recorded in a single shot.

You’ll often reveal much more signal on a deep-sky object in a 5-minute exposure than you would in 30 seconds. This makes being able to consistently capture long-exposure images with sharp, focused details a real benefit for astrophotography.

However, to do this requires extreme accuracy from your equatorial telescope mount as it slowly tracks the apparent movement of the sky. Even the slightest amount of periodic error can ruin a long exposure image of your target.

As you increase your telescope’s focal length, autoguiding becomes more important. This is because we are now “sampling” a smaller (zoomed-in) area of the night sky that can potentially highlight the smallest amount of period error in your telescope mount.

This image of the Veil Nebula was captured on an affordable equatorial mount using autoguiding.

Autoguiding is accomplished by sending small corrections to your telescope mount via an ST-4 cable that communicates with your guide camera to the mount. You can also autoguide using the pulse-guiding method that directly connects your PC to the telescope mount.

It is said that pulse guiding (with an ASCOM-compliant) equatorial mount improves guiding accuracy. This can be measured using the tools in the PHD2 guiding software, mainly in the total RMS error reading. 

Over the years, I have made it very clear on my YouTube channel that I don’t obsess about these values much. However, if you are looking for a general benchmark, Jerry Lodriguss shared a helpful reference in this Cloudy Nights thread:

• Good seeing (2″) averages around 0.3 arcseconds RMS in the guiding
• Average seeing (2-3″) averages around 0.5 arcseconds RMS in the guiding.
• Bad seeing (more than 3″) averages around 1.0 arcseconds RMS in the guiding.

My portable deep-sky astrophotography setup with a 50mm William Optics 50mm guide scope riding on top. 

Why It’s Useful for Astrophotography

Modern equatorial telescope mounts are quite capable of compensating for the Earth’s rotation —that is what they were designed for. However, deep-sky astrophotography (especially at longer focal lengths) is a very demanding application for any entry-level to intermediate equatorial mount.

Depending on which telescope mount you’re using, subtle errors in the accuracy of your polar alignment can begin to surface in images as short as 60 seconds. The slightest bit of off-balance in your imaging payload can put stress on the gears in your mount, which often leads to less-than-perfect stars in your long exposure image.

Even with your polar alignment spot-on and your payload perfectly balanced, autoguiding is often necessary to track your object smoothly enough for astrophotography. This is especially true on beginner-level GoTo mounts such as the Sky-Watcher HEQ5 Pro pictured below.

My Sky-Watcher HEQ5 Pro mount with a refractor guide scope mounted to the primary imaging telescope.

The telescope mount itself may have shortcomings due to worn-out gears or low-cost materials used in its construction. If the issues are severe enough, even autoguiding won’t help.

For this reason, it’s always best to invest in a quality telescope mount that has been proven reliable for deep-sky astrophotography. 

Thankfully, basic autoguiding is enough to correct most of the issues associated with modern equatorial mounts. 

What I’m Using

I am currently using various autoguiding systems, including my   Sky-Watcher EQ6-R Pro , CQ-350, and ZWO AM5. I have used a number of different guide scopes, from the Orion 50mm Mini Guide Scope to a William Optics 72 APO Doublet.

If you’re using a guide scope for autoguiding, a good rule of thumb is to use one with a focal length of at least a third of your primary imaging scope. 

An off-axis guider solves this problem by utilizing the native focal length of your imaging telescope, but it can add weight and complexity to your camera system. Both systems have their strengths and weaknesses, but I personally prefer the simplicity of an auxiliary guide scope over an OAG. 

In the following video, you’ll see me use autoguiding to collect 3-minute-long exposures on the Cocoon Nebula, using a DSLR camera and a 73mm telescope. When using a DSLR camera for deep sky astrophotography, autoguiding allows you to shoot longer, and dithering (which helps reduce noise in your stacked image) is now possible. 

Here is a complete list of guide scopes I have used in the past:

• Orion 50mm Mini Guide Scope
• Starfield 50mm Guide Scope
• Starfield 60mm Guide Scope
• William Optics Z72 APO Doublet

I primarily use a William Optics 50mm Guide Scope because it is lightweight and easy to mount to various telescopes. 

This little telescope features the William Optics Rotolock system, a design feature that securely holds your 1.25″ barrel guide camera. I have found it very convenient to adjust the Rotolock system to move the guide camera in-and-out of the optical tube to find focus.

The guide scope’s focal length is 200mm @ F/4. You’ll need to fit the tube into an appropriate set of tube rings or your existing finderscope rings on your telescope. 

The camera I use most often with the 50mm guide scope is the ZWO ASI 290mm mini . This is a highly sensitive monochrome guide camera and compatible with the ZWO ASIair Wi-Fi camera control device and software.

The ASIAIR Plus has its own autoguiding program in the application that communicates with the telescope mount just like PHD2 does.

What you need to start Autoguiding

The basic equipment needed to accomplish a successful night of astrophotography with autoguiding is a secondary telescope (guide scope) and a guide camera. The guide scope rides atop your primary imaging telescope and is usually much smaller. The autoguiding camera is traditionally lighter than your primary imaging camera, and will often include a small mono CCD or CMOS sensor.

Once properly connected to your computer using the appropriate cable (in my case, a USB 2.0 A-male to B-male cable), the autoguiding camera will broadcast a live-loop image through the guide scope to your computer.

How it works

The main objective of your autoguiding system is to focus and lock onto a star in the guide telescope’s field of view. The camera continuously captures short exposures through the guide scope, usually between 1 and 3 seconds in length.

The guide camera and your telescope mount communicate to maintain a lock on your target by making subtle corrections to the tracking. This is accomplished using great free software developed by Stark Labs called PHD2 Guiding. 

PHD2 Guiding

Our computer can communicate with the telescope mount using autoguiding software such as PHD2 Guiding. PHD2 Guiding is the successor to PHD Guiding, which I used for several years before upgrading to PHD2. PHD stands for “Push Here Dummy,” and it is very easy to use once everything is set up properly.

This software can also do other useful astrophotography tasks, such as drift alignment , which is helpful for those who cannot use Polaris for Polar Alignment .

I use a 1-second refresh rate on the Altair GPCAM2 to display an assortment of stars within the field of view. It is important to make sure that the guide scope is properly focused to ensure accurate star tracking. When PHD2 is running, I usually open on the “graph” window to monitor the accuracy of the tracking.

Please consider visiting the Learn Astrophotography section of this site to explore my techniques in real-life backyard situations.

What is Off-Axis Guiding?

Off-axis guiding (or OAG) involves using a device that sends starlight to your guide camera from the optical axis of your primary imaging telescope. It does not affect your primary imaging camera, as it uses the ” off-axis ” starlight and does not enter it.

I have used the Lumicon Easy Guider for off-axis autoguiding with my iOptron SkyGuider Pro . The pick-off prism sent useful guide stars to my ZWO ASI290mm min i guide camera to correct the telescope mount for long-exposure astrophotography.

Using an OAG for autoguiding on an iOptron SkyGuider Pro.

No matter which autoguiding method you use, the goal is simple: to capture long-exposure images with round, sharp stars. If you’re able to collect images over three minutes in length through your telescope, your autoguiding system has done its job. 

Final Thoughts

Autoguiding is something that you won’t even think about once you’ve got it working properly. For those having issues early on, I urge you to ensure that your telescope mount is properly polar aligned and balanced (with no cable snags) before trying to diagnose autoguiding issues. 

Also, don’t obsess about the numbers and guiding graphs within PHD2 guiding. If you are chasing numbers, chances are you’re not taking pictures. If you’re taking pin-sharp 5-minute exposures at a focal length of 1000mm or more, chances are your autoguiding system is working just fine. 

Open PHD Guiding

• Use the forum search tools - most questions have been answered many times
• Read and follow the Best Practices Guide
• Use the New-Profile-Wizard to define and manage your equipment configurations
• Avoid making changes to guiding parameters without knowing exactly what they do
• After you get a good calibration run and a Guiding Assistant Run, per the Best Practices, run the Baseline Assessment

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Solar and Lunar autoguiding with PHD2.

By Steve Ward March 3 in Discussions - Software

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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.

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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.

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

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.

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?

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.

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!

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.

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.

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 Shatz I think your github link is missing the user and repo bits

21 hours ago, yopero said: @Leo Shatz I 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

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!

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

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

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• Framing Assistant
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Telescope mounts inherently have imperfections that prevent them from perfectly tracking objects in the sky as the Earth rotates. These issues include: * Imperfect polar alignment * Mechanical errors in drive gearing * Wind and other environmental conditions

One way of countering these issues to improve long exposure quality is to use a 2nd camera, a guide scope or Off-Axis Guider, and a Guiding Application . It works by locking onto a guide star and sending small corrections (pulses) to counteract guide star movements. N.I.N.A. supports the following Guiding Applications : * PHD2 * MGEN2 * MetaGuide * Direct Guider

PHD2 is the most commonly used guiding application. It is free and open source, and can be found here .

PHD2 Settings #

In order for N.I.N.A. to communicate with PHD2 and command operations such as dithering and for receiving guiding telemetry, PHD2's internal server must be enabled. To enable PHD2's internal server, go to PHD2's Tools menu and ensure that Enable Server is selected.

There are numerous tutorials online for setting up PHD2. One nice feature N.I.N.A. provides is that it can automatically start PHD2 and connect to it after you've set it up the first time.

MetaGuide #

MetaGuide takes a different approach to guiding than PHD2 by using Lucky Imaging . It is free, and provided by Frank Freestar8n here .

MetaGuide Setup #

MetaGuide setup is more involved than PHD2, so be sure to carefully read the documentation. After you've set it up, you can do the following to connect it to N.I.N.A.

MetaGuide Extended Status #

• Intensity is a value from 0-255 that represents saturation of the selected guide star. You typically want this close to 255, and could reduce exposure duration in MetaGuide if you're fully saturated. The value can drop during guiding when clouds come in, which is where the next setting comes in.
• Minimum Intensity is the lowest value for Intensity that N.I.N.A. will allow guiding to continue. If the Intensity falls below this threshold for a few seconds, then guiding will pause until Intensity is restored
• Dither Settling Time is how long N.I.N.A. will wait after triggering a dither to resume imaging. This differs from PHD2 which tells N.I.N.A. when guiding has settled after dithering. You'll likely need to tune this based on how your mount behaves in practice.

A certain margin of error here tends to be okay. However, some items are telltale signs that something is wrong with either your equipment or a setting.

The Calibration Graph

The first thing we want to look at here is the graph on the left. This is representative of what I would consider to be a pretty good calibration.

What you are looking for is a right angle on this graph with reasonably straight lines. I have never known it to be an issue if the lines don’t match up with the X and Y axis on the graph, as long as they are straight.

On the other hand, if your calibration results look more like a scatter chart, something went wrong. In this case, you want to re-calibrate before proceeding with your guiding.

The Number of RA and Dec steps

Generally speaking, these two numbers should be between 8 and 14 steps in each direction, according to PHD2’s website.

As I mentioned, a slight margin of error is acceptable as long as it doesn’t affect your guiding. If these numbers are wildly outside of the range mentioned above, there’s a good chance your calibration will fail altogether. I will touch more on this later.

RA and Dec Rate

The numbers on your chart may not be the same as mine, as they are mainly dictated by your guide rate. My guide rate here was set to 0.50x.

If there is a major difference between the actual and expected rates, there is an issue somewhere.

Most of the time, the issue is that your guide rate in PHD2, and the guide rate in your ASCOM software don’t match. This is a problem that needs to be corrected before you proceed with your guiding.

If the difference you see is only in your Dec rate, this is likely backlash in your mount. Before you resort to opening it up and tuning it, make sure to run the Guiding Assistant.

Both of these topics are covered here in 9 tips on how to improve PHD2 guiding .

Declination

This is the declination of where my scope was pointing when I did the calibration; as you can see, mine was not within 30 degrees of the celestial equator. Whoops.

My guiding was still pretty good in this case, but it’s a good idea to stay within the PHD2 guidelines now that you know what they are.

Focal Length

This is the focal length of your guide scope.

It’s not the diameter of the guide scope, and it’s definitely not related in any way to your main scope unless you are using an off-axis guider.

If this is wrong, it’s probably going to cause the following error that I will discuss.

Calibration Failed- Star did not move enough.

If you are getting this error message, it’s likely because you have your guide scope focal length or your guide camera pixel size set incorrectly.

Both of these numbers absolutely must be correct. PHD2 needs these two numbers to calculate the image scale of your guiding equipment. It uses the image scale and the calibration distance to calculate the correct value for the calibration steps.

When these settings are wrong, the calculation for the calibration steps is also going to be incorrect. As a result, the star will likely not move enough, and your calibration will fail.

To check these settings, click on the brain in the bottom left-hand corner and click on guiding.

If you realize that your focal length is incorrect and change it, make sure you still click on advanced.

If you don’t click advanced to open the calibration calculator, it will not re-calculate the correct calibration steps. If the calibration steps are left unchanged, the problem will persist.

PHD2 is a fantastic piece of guiding software and is pretty easy to use once you have it set up correctly.

Before you can start guiding, you need to make sure that your settings are correct and calibrate properly.

The vast majority of PHD2 guiding issues are caused by one of the three following things: 

• The guide rate in PHD2 doesn’t match the ASCOM software guide rate 
• The guide scope focal length is set incorrectly 
• The guide camera pixel size is set incorrectly 

Sources: https://openphdguiding.org/man-dev/Advanced_settings.htm

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PHD2 problems with guiding Open PHD Guiding project PHD2 · Luke-Official · ... · 4 · 392 · 0

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Using the SV105 and SV205 as a Guide Camera with PHD2

• Dec 28,2019
•  SV105 Guider camera,  SV105 Camera,  Guider,  SV105,  SV205

Kevin Cobble Z-Field Observatory

December 16, 2019

The Svbony SV105 and SV205 cameras, while intended for planetary astrophotography, can also be used as a guide camera.  The main limitation is that they do not have long exposure times and are not real sensitive so they can only guide on brighter stars. More about this later. Both of these cameras use the UVC (USB Video device Class) format that is recognized by both Windows and Mac OS. In windows it is also known as OpenCV.  As of this writing the SV305 camera cannot be used with guiding software as it does not use the UVC format, instead having its own driver.  It will need either a specific driver written for PHD2 or MetaGuide or have an ASCOM driver. This document assumes you have a GOTO mount with a computer connection.  The SV105 and SV205 do not have ST-4 connectors so cannot connect to the mount directly. In reality, since you need a computer to run the software it is actually better to connect to the mount through its driver rather than an ST-4 port.

Connecting to PHD2

When you start PHD2 you will see the screen above.  Press the USB setup button (arrowed) to get to the equipment setup screen.

When you do you will get the Connect Equipment Dialog Box shown above.  This allows you to connect both the camera and the mount. Press the down arrow (shown arrowed) to go to the camera connect screen.

After selecting the camera you will get a Camera mode window.  Select the top one and click OK. This should take you back to the Connect Equipment window and you can select and setup your mount connection (Celestron in my case).  After your finished press the Close button to get back to PHD2.

Now that your camera and mount are setup press the button (arrowed) to start the camera.  You should see some stars if they are bright enough for your camera/guide scope configuration. From this point onward you will need to consult the PHD2 instructions as to setting up guiding.

This is a screen grab of PHD2 working with the SV105 camera on a Celestron 70mm Travelscope.  Obviously Polaris would make a good guide star.  In this case I’ve selected HD5914, which at 6.5 magnitude is about as dim a star as PHD2 could probably guide on.  While HD1685 (8.12 mag) is visible, it is too dim to guide on.

This is my setup showing the SV105 camera attached to the Celestron 70mm Travelscope.  The camera and the Celestron CGEM mount are both attached to a laptop.

Thanks very much for Kevin Cobble write this blog for us. welcome all comments following. 

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