Barton Lake Instruments · Software

Seeing Monitor

Windows software that measures your sky's seeing all night, every night, with a small camera pointed at Polaris.

Download 3.0.11 Free · Windows 10 and 11 · QHY, ZWO, SBIG and Player One cameras
Seeing Monitor's main window during monitoring: the current seeing value in arcseconds, a live view of the star, a list of recent one-minute cycles, and a graph of the night so far.
Seeing measured every minute, all night: the seeing value, a live view of the star, recent cycles and the night's graph in one window. Shown with example data.

How it measures seeing

Single Image Motion Monitor · SIMM

Seeing Monitor is a Single Image Motion Monitor (SIMM). A fixed camera watches Polaris and takes 256 very short exposures each minute. It measures how much the star dances, then turns that motion into seeing in arcseconds, corrected to the zenith, using the standard Kolmogorov turbulence model.

Unlike a DIMM, it needs no aperture mask and no tracking mount, just a steady mounting.

Further reading

An example setup

The seeing monitor at Barton Lake Observatory: a small camera and lens in a weatherproof housing, fixed on a pole and aimed at Polaris. No tracking mount is needed.

A weatherproof camera housing on a metal pole beside an observatory dome, tilted up towards the north.
A weatherproof camera housing on a fixed pole, tilted up at Polaris.
The camera housing opened, showing a small astronomy camera on a ZWO 30F4 mini scope, with a gold heating rod alongside.
Inside: the camera on a small guide scope, with a heating rod alongside.
Camera
QHY5L-II
Lens
ZWO 30F4 mini scope (30 mm, f/4)
Housing
Weatherproof security-camera enclosure
Heating
Heating rod on a timer, switched on overnight to keep dew and frost off the window
Mount
Fixed pole, no tracking

This is one example, not a requirement. Seeing Monitor supports QHY, ZWO, SBIG and Player One cameras and works from whatever pixel size, focal length and aperture you enter.

Planning your own? Feel free to get in touch at info@bartonlakeinstruments.com to talk through hardware designs.

What Seeing Monitor does

Measuring

A seeing value every minute

A new seeing value in arcseconds every minute, corrected to the zenith for your latitude. A live close-up of the star and a chart of the whole night show it happening.

Scheduling

Runs the night on its own

Enter your site once. Seeing Monitor works out twilight for every night, connects the camera, and starts and stops by itself. It can also start with Windows, so an observatory computer recovers from a restart.

History

Every night on record

Seeing History shows every night you've logged as a table, a trend or a calendar, by day, week, month, season or year. Click any night to see each reading. It brings in your existing seeing logs and never changes them.

Focus

Focus and align with confidence

Focus/Alignment mode gives a live view with a reading of how tightly the star's light is concentrated, so you can tell when focus is right. With ASTAP installed, one click plate-solves the field and marks the pole and Polaris.

Publishing

Publish tonight's seeing

Save tonight's chart through the night in one of four styles, and upload it, or the night's log, to your website by FTP, FTPS, SFTP or Amazon S3.

ASCOM

Seeing for N.I.N.A., PHD2 and other ASCOM programs

An optional ASCOM ObservingConditions driver reports the current seeing through the standard StarFWHM property, so your imaging and guiding software can read it. Readings are also written to plain text logs, and Seeing Monitor works with QHY, ZWO, SBIG and Player One cameras.

A look inside

Seeing History calendar view for a month, each night shaded by how good the seeing was, with its seeing value in arcseconds.
Every night at a glance, coloured by how good the seeing was. Example data.
Seeing History trend view showing each night's median seeing with its best and worst readings.
Two months of nights: the median, with the best and worst of each. Example data.
Seeing Detail window showing one night's seeing readings as a chart, with the median, the lowest value and the details of a selected reading.
Any night in detail, down to a single reading. Example night.
An example night's seeing chart in the Refined Line style. An example night's seeing chart in the Instrument Panel style. An example night's seeing chart in the Stacked Tile style. An example night's seeing chart in the Seeing and Transparency style.
Four chart styles for your website, shown with an example night.
Focus/Alignment window with exposure and gain controls and a live view marked with the predicted positions of Polaris and the north celestial pole.
Focus, and find the pole: a live view with the predicted positions of Polaris and the pole.
Configure Night Schedule dialog with the site's latitude and longitude, astronomical twilight, and the start and stop times.
Runs from twilight to twilight, worked out for your site every day.

Download

Free · Version 3.0.11 · 21 September 2026

Seeing Monitor 3.0.11

57.1 MB · Windows 10 and 11, 64-bit. The installer includes everything Seeing Monitor itself needs; installing it needs administrator rights. Install your camera's own USB driver first.

Download the installer What's new in 3.0.11 Read the user guide

Using N.I.N.A., PHD2 or another ASCOM program? Download the ASCOM driver 1.0.2 (install the ASCOM Platform first).

Windows may show “Windows protected your PC” the first time you run the installer. Click More info, then Run anyway.

SHA-256 1040B29C79F1EB6AC0EB3AEE8BFA6B7F800F1938763ECC34F92DF91FE6951936

Good to know
  • Runs on 64-bit Windows 10 and 11.
  • Install your camera's own USB driver first: QHY, ZWO, Player One, or SBIG's 64-bit driver. The installer lists where to get each one.
  • ASTAP is optional and only needed for plate-solving in Focus/Alignment mode.
  • Your readings stay on your computer unless you choose to upload them.
  • Seeing History only reads your existing log files. It never changes them.
  • The ASCOM driver is a separate, optional download. Seeing Monitor never installs it for you.
  • Free to download and use, with free updates: Help ▸ Check for Updates tells you when a new version is out.

Questions, bug reports and feature suggestions are all welcome by email: support@bartonlakeinstruments.com