PHD2 review: the free autoguiding that changed my imaging
Where does it rank on our leaderboard
| Rank | Software | Stars for Your Buck | Recorded UK price |
|---|---|---|---|
| 1 | Stellarium | 100 out of 100 | Free |
| 2 | NINA | 98 out of 100 | Free |
| 3 | SharpCap | 97 out of 100 | £14 |
| 5 | BlurXTerminator | 95 out of 100 | £75 |
| 6 | PHD2 | 94 out of 100 | Free |
| 11 | StarXTerminator | 85 out of 100 | £45 |
| 13 | RegiStax | 77 out of 100 | Free |
| 15 | DeepSkyStacker | 71 out of 100 | Free |
| 16 | Adobe Photoshop | 67 out of 100 | £22 |
Contents
- 01 Where does it rank on our leaderboard
- 02 Specifications and features
- 03 A walk through PHD2
- 04 In my words
- 05 Should you buy it?
- 06 Questions and more about this review
In 30 seconds
Stars for Your Buck 94/100
Written 2 Oct 2026 Updated 2 Oct 2026
- Rank
- #6 of 16 software
- Verdict
- Damon's pick
Written by Damon Scotting 3 min read
Buy it if
- You image deep sky on an equatorial mount and your stars trail after a minute or so.
- You want longer exposures without nudging the mount back by hand.
- You want guiding software that costs nothing.
With PHD2 guiding, five-minute exposures became easy and single subs looked almost like finished images.
Specifications and features
Against the software I have reviewed
Compare with
| PHD2 reviewed #6 of 16 | ASIAIR app #9 of 16 | NINA #2 of 16 | |
|---|---|---|---|
| Recorded UK price | Free | Free | Free |
| Stars for Your Buck | 94/100 | 89/100 | 98/100 |
| Made by | The Open PHD Guiding project | ZWO (Suzhou, China) | Stefan Berg and the N.I.N.A. contributors |
| What it is for | Autoguiding: tracking a guide star and correcting the mount | Remote control of an ASIAIR controller and the whole imaging rig, from a phone or tablet | Equipment control and automated imaging sequences |
| Licence | Free and open source (BSD 3-Clause) | Free app; needs an ASIAIR controller (ASIAIR Plus 256G $399, ASIAIR Mini $249 on ZWO's store) | Free and open source (Mozilla Public License 2.0) |
| Operating systems | Windows, macOS 10.14 or later (64 bit), Linux | iOS 13 or later (iPhone and iPad), Android, macOS 11 or later on Apple silicon | Windows 10 (64 bit) or later |
| Current version | 2.6.14 (10 Dec 2025) | 3.0 (29 Jul 2026) | 3.2 |
| Polar alignment | Drift alignment tools | Yes | Through the Three Point Polar Alignment plugin |
A walk through PHD2
The main window The guide camera's view fills the top, shown here with no camera connected; the history graph below plots the RA and Dec error in pixels, with the RMS beside it.
Camera settings The Camera tab of the advanced settings: noise reduction, time lapse, and auto exposure between a minimum and a maximum for a target signal-to-noise ratio.
Guiding settings The Guiding tab: the guide-star search region, star mass detection, multiple guide stars, and calibration from the guide scope's focal length.
In my words
“PHD2 might be the most influential astrophotography software of the 2010s. When I started, with alt-azimuth mounts and scopes like the Celestron 6SE, I didn't know it existed, and I spent whole sessions wishing for something that would pick a star and keep nudging it back to the centre, because I was doing it by hand with the controller. You cannot centre a target and image it at the same time, especially with the DSLRs we used then.”
From my dictated take
“Even after moving up to a Celestron CG5 GoTo mount, no matter how well I polar aligned, targets drifted and stars trailed after about sixty seconds. Adding PHD2 was a light-bulb moment. Suddenly five-minute exposures were easy, and single subs looked almost like finished images, with far more signal than I had ever seen. And like so much great astronomy software, it is free.”
From my dictated take
“There is a whole set of extra tools for perfecting your guiding that I have never needed to explore, but it is reassuring that they are there. These days I mostly use it to check results from my ASIAIR: its folders hold PHD2 guide logs, and opening them in PHD2 shows remarkable detail, from how well the mount was polar aligned to guiding performance for the whole night and for each target. It is about as good as a Stars for Your Buck score gets.”
From my dictated take
Should you buy it?
94/100 Stars for Your Buck
Pros
- It picks a star and keeps nudging it back to the centre, so you never guide by hand.
- Five-minute exposures become easy, where stars trailed after about sixty seconds without it.
- Single subs look almost like finished images, with far more signal.
- It is free.
- A whole set of extra tools for perfecting your guiding is there when you need it.
It is about as good as a Stars for Your Buck score gets.
Two alternatives I have reviewed
- ASIAIR app ZWO's phone app for an ASIAIR rig, with its own guiding graph 89/100 Free Read the review
- NINA Runs the whole night on Windows and drives PHD2 for guiding 98/100 Free Read the review
Questions and more about this review
Reviewed by
Damon Scotting
The Telescope Man Verified
BSc (Hons) Physics with Astrophysics and Cosmology, Loughborough University PGCE / QTS, University of Nottingham
About Damon About Damon Damon Scotting is The Telescope Man. He holds a BSc (Hons) in Physics with Astrophysics and Cosmology from Loughborough University and a PGCE with QTS from the University of Nottingham, and taught physics in secondary schools before becoming an astronomy creator. He is a contributing writer for BBC Sky at Night Magazine and the author of 42 Wonders of Our Night Sky, and his photograph of the galaxy M100 with the dwarf planet Ceres was Highly Commended in the Astronomy Photographer of the Year 2024 competition run by Royal Observatory Greenwich. He has appeared on the BBC's Blue Peter. More than 750,000 people follow his astronomy channels on YouTube, Instagram and TikTok, and he has reviewed more than 140 telescopes, mounts, cameras, filters and accessories hands-on for this site. More about Damon · How I test · Damon's book
I review all kinds of gear: most of it I buy, some is gifted and some is loaned, and all of it is reviewed the same way. How this site is funded
Six questions, answered
Questions about the PHD2
Written 2 October 2026 ·Updated 2 October 2026
I review all kinds of gear. Most of it I buy, some is gifted and some is loaned, and all of it is reviewed the same way: no company sees or approves a review before it is published. How this site is funded
- Is PHD2 free? Yes. It is free of cost and open source, under the BSD 3-Clause licence, and developed by its community. The specifications and the comparison table ↓
- What do I need to guide with it? A guide camera and a mount it can send corrections to. The project lists extensive support for commonly used equipment, and a setup wizard gets guiding started in a few clicks. The specifications and the comparison table ↓
- Does PHD2 run on a Mac? Yes: on macOS 10.14 Mojave or later in 64 bit, as well as on Windows and Linux. The specifications and the comparison table ↓
- Can it tell me how well my mount performs? Yes. Its Guiding Assistant measures mount performance, and its graphs and guide logs let you review the guiding afterwards. A walk through PHD2 ↓
- Which version is current? Version 2.6.14, released on 10 December 2025. The specifications and the comparison table ↓
- What have I not tested on the PHD2? My screenshots show PHD2 with no guide camera or mount connected, so they show its controls, not a night of guiding.