A logbook that stays yours
Keeping a log is how observers improve. You learn what your telescope can show, which nights are worth it, and how many Messier objects you have ticked off. Most logging apps want an account and keep your notes on their servers. This one keeps your log in a plain CSV file on your own device: one row per observation, with clear column names. It opens in Excel, Google Sheets, LibreOffice, Python or any database, and nothing is ever uploaded.
How to use it
- Set your place at the top. It is written into each observation along with the latitude and longitude. Your location stays on your device.
- Type the object. Catalogue names (M13, NGC 7000) fill in the type, constellation and position for you, and planets and the Moon are recognised too. Anything else is kept as you type it.
- Add your telescope, eyepiece or camera, magnification and filter. These stay filled in for the next object, so a night’s log is quick.
- Rate the seeing (how steady the air is), transparency (how clear), the sky’s Bortle darkness, and how good the view was. Write your notes. On a phone, the microphone on your keyboard lets you dictate them.
- Press Save observation. Every time, you are asked where it should go:
- Save as a new log file: starts a new CSV file, for example one per night, per season or per project.
- Add to an existing log file: pick your log, and the observation is added as a new row. In Chrome and Edge on a computer the file is updated in place, and later saves offer Add to (your file) again in one tap. In other browsers, the updated file downloads with the same name, ready to replace the old copy.
- Keep in this tab for now: holds it until you next save to a file. That’s handy when you are logging quickly at the telescope.
- Your log shows what you saved in this tab. Press Open a log file to see a whole log, with totals for observations, nights, different objects and Messier objects seen out of 110.
- Download a log as an image, PDF or Word file to print, share with your club, or keep as a tidy record.
Red light
Press Red light at the top of the page to turn the whole screen red and black. Red light keeps your eyes adapted to the dark, which takes 20 to 30 minutes to build and seconds to lose. Turn your screen brightness down too.
What’s in the file
Columns: id, utc_time, local_date, local_time, object, type, constellation, ra_j2000, dec_j2000, place, latitude, longitude, telescope, eyepiece_or_camera, magnification, filter, seeing_1_to_5, transparency_1_to_5, bortle, rating_1_to_5, notes. You can add your own columns in a spreadsheet. The log reads columns by name, so your extra columns are kept when you add new rows.
Worked example
On a Saturday you observe M13, M57 and Saturn with an 8-inch Dobsonian. Save the first as a new file, observing-log-2026-11-07.csv, and add the next two with Add to … again. A month later, open that file to add the Orion Nebula. The summary shows 4 observations over 2 nights, with 3 Messier objects seen.
Questions
Where is my log stored? Only in the files you save. Observations kept in the tab are removed when you close it, so save to a file before you go.
Can I edit old entries? Yes. Open the CSV in a spreadsheet, edit it and save it as CSV. The log reads it back.
Where the numbers come from
- Sun, Moon and planet positions: astronomy-engine by Don Cross (MIT licence), accurate to about an arcminute.
- Deep-sky objects: the OpenNGC catalogue by Mattia Verga (CC BY-SA 4.0).
- City coordinates and time zones: public geographic facts, typed by fibub.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-07.