Why a checklist changes how you observe
The Messier catalog — 110 objects cataloged by Charles Messier in the 18th century, numbered M1 through M110 — is one of the most commonly pursued milestones in amateur astronomy. Some observers attempt a “Messier Marathon,” hunting as many objects as possible in a single overnight window when the whole catalog is theoretically visible; others work through the list gradually over months or years as objects come into season.
Either way, a checklist changes the character of the hobby. Instead of pointing a telescope at whatever looks interesting on a given night, you’re working toward a defined, finite goal, and that goal benefits from the same structure as any other checklist-based project: knowing at a glance what’s done, what’s left, and when the remaining items are actually visible.
Running a checklist-based observing project, in any format
None of this requires special software — it requires treating the catalog as a tracked list rather than something you remember.
- Track observed vs. not-yet-observed explicitly. A simple table with all 110 Messier numbers and a column to mark each as observed (with the date) is enough, whether that’s a printed checklist, a spreadsheet, or a notebook page. The point is having a single place that reflects your actual progress, rather than relying on memory or scrolling back through a chronological log to reconstruct it.
- Match your naming to the log. If your checklist says “M31” but your observation notes say “Andromeda Galaxy,” you’ll eventually lose track of which entries correspond to which checklist item. Using the same identifier in both places (see our article on cross-referencing repeat observations) keeps the two in sync.
- Plan around seasonal visibility. Not all 110 objects are up at once — many Messier objects cluster in spring (galaxies) and summer (globular clusters and nebulae near the galactic center), with a leaner northern-hemisphere window in late autumn. Noting which objects are seasonally available helps you avoid saving the same handful of “hard” objects for a time of year when they’re not actually visible.
- Update the checklist right after the session, not later. The main way a checklist project stalls is a backlog of unrecorded sessions. Marking an object off immediately — in a notebook or a spreadsheet — keeps the list trustworthy.
Kept this way, whether on paper, in a spreadsheet, or in an app, a Messier checklist turns a 110-object list from an abstract “someday” goal into a project with visible, incremental progress.
How Astral Book handles this
We built Astral Book‘s Messier tracker to automate the bookkeeping described above rather than replace it. The catalog is implemented as a static, built-in list of all 110 objects, stored locally so it’s available even at remote, offline dark-sky sites.
An object in the catalog is automatically marked “observed” whenever a saved observation’s target name matches a Messier designation (e.g., “M1” or “M42”) — the same target-name matching used for reviewing repeat observations of a single object. This means the checklist stays in sync with your log automatically instead of requiring you to update two places by hand. Tapping into a specific object in the catalog view also surfaces your past observations of it, or lets you start a new observation directly, so the checklist doubles as a navigation shortcut into your history.
This can also be a genuine convenience if you’d otherwise keep a checklist in a notebook or spreadsheet alongside your log: rather than remembering to update both, checking off happens passively the moment you save an observation.
The Messier catalog tracker is a free-tier feature. Key aspects of the Astral Book implementation:
- Offline-First Reliability: All Messier data and matching logic are stored locally on the device, so you can review progress and log new targets from remote sites without cellular reception.
- Data Portability: The app supports free CSV, ZIP, and PDF exports (including photos), so your Messier progress leaves the app in a portable form whenever you want it.
- Workflow Integration: The Messier catalog works alongside the Wishlist and Location Master as part of the app’s broader observation-management tools.
- Privacy-First: Astral Book requires no account creation and does not sync your private logs to a cloud service.
For users who want to remove the 20-log limit and access advanced features — such as the Equipment Master for tracking specific telescope and eyepiece combinations, or detailed Observation Statistics — a Pro upgrade is available as a one-time purchase.
Download Astral Book on the App Store: https://apps.apple.com/us/app/astral-book/id6764449141
Summary
Working through the Messier catalog is fundamentally a checklist project, and it benefits from the same discipline as any checklist: explicit observed/not-observed tracking, consistent naming, and awareness of seasonal visibility. That checklist can live on paper or in a spreadsheet just as validly as in an app — a dedicated tool’s main advantage is keeping the checklist automatically in sync with your observation log so you don’t have to update both by hand.
For a broader look at how different tools compare for managing your observation history, see our hub article: Astronomy Observation Logs: A System, Not Just a Notebook
To learn more about tracking your own personal targets, read: From Wishlist to Logged: Tracking What You Still Want to Observe
This article organizes information from a recording and organizing perspective. If you notice an error or outdated information, please contact us. Last verified: August 2026
