Hack28.Develop an Organized Logging System

Hack 28. Develop an Organized Logging System

Apply accounting techniques to keep track of your observations. Record it once, and you can use it forever.

Accounting records are organized in two ways. A journal records transaction details chronologically as they occur, like your checkbook register. Those transactions are later transferred to a ledger, which organizes the data into categories, such as salary income, rent payments, and so on.

Well-organized astronomers use a similar method for keeping their observing records. The log sheets you fill out during observing sessions are journals because they record transactions chronologically. Periodically, you should transfer those records to a consolidated ledger. A spreadsheet is the ideal tool for creating a ledger because it allows you to sort your observations according to different criteria. For example, if you're "constellation sweeping" in Cassiopeia and want to know which objects you've already observed there, it takes only seconds to sort your ledger by constellation. Similarly, if you're pursuing globular clusters, for example, it's easy to sort your ledger by object type and then NGC number to provide a list in NGC order of globs you've already observed.

Figure 2-31 shows an excerpt from Barbara's observing ledger, sorted first on the "D" column and then on the NGC/IC column to provide a list of the objects by NGC/IC number that she's observed on the Astronomical League Deep-Sky Binocular (D) list. (This is from an old copy of her ledger; she's since completed the DSB list.)

Figure 2-31. A section of Barbara's observing ledger

Each row of the list records the following information about one observation:

Date through LM

These columns record the date and time of each observation, the location, the weather conditions, transparency, seeing, cloudiness, and limiting magnitude at zenith. Because the date and time are recorded for each object, it's easy to locate the original observing record simply by retrieving the log sheet for the observing session that took place on that date.


The common name of the object, if any. For example, M13 (Messier Object 13, at the bottom of the list) is the common name of NGC 6205. This field can also be used to record secondary designations for the object. For example, the names in the form H4-7 are the Herschel designations for these objects. These are used for the Astronomical League Herschel 400 list, which Barbara is also working on.


Thousands of galaxies, star clusters, nebulae, and other deep-space objects are assigned an NGC (New General Catalog) or IC (Index Catalog) number. Because most objects have an NGC/IC designation, it's convenient to use this designation as the key field. Many objects are known under various common names. For example, NGC 7009 in Aquarius is also known as the Saturn Nebula, Bennett 127, Caldwell Object 55, and Herschel Object IV.1 (4-1). But because all of these other lists are always cross-referenced by NGC/IC number, if you always record the NGC/IC number, you'll always be able to keep track of which objects you've logged and which belong to such lists as the Messier, Herschel 400, Caldwell, and so on. Some objects have no NGC or IC designation. In that case, simply record the designation by which the object is known most commonly, such as Kemble 1 or Stock 23.


Most experienced astronomers "constellation sweep" [Hack #26]. In other words, rather than sequentially pursuing all objects on, say, the Herschel 400 list, they focus on one or a few constellations at a time, logging all objects in that constellation regardless of which lists they may be on. If you record the constellation each time you log an object, you can later sort your ledger by constellation to determine which objects in that constellation you've already logged.


This is the type of object logged, for example, an open cluster (OC), globular cluster (GC), galaxy (SG, EG, etc.), planetary nebula (PN), supernova remnant (SNR), emission nebula (EN), multiple star (MS), variable star (VS), and so on. Capturing this information for each object allows you to go back later and sort by object type. For example, you may plan to work planetary nebulae in Sagittarius one evening and want to know which ones you've already logged.


Record the instrument and eyepiece you used for each observation.


Record supplementary information, such as whether a Barlow or filter was used.

D, H, M, BM, C, U, DS, L

Barbara is currently working on or has completed the lists for several Astronomical League observing clubs, including the Deep-Sky Binocular (D), Herschel 400 (H), Messier (M), Binocular Messier (BM), Caldwell (C), Urban Observing (U), Double Star (DS), and Lunar Club (L). Having a field for each of these lists makes it easy for her to sort her ledger by AL club to determine which objects she has already observed on the lists in question. For example, several of the objects she's logged for the Deep-Sky Binocular (D) list also appear on the Herschel 400 (H) list, so she marked those objects as observed for both clubs when she updated her ledger.


Write your detailed comments about each object. Take as much room as you need here. If you sketched or photographed the object, note the location of that image. You can also use this field for comparative comments, e.g., differences in appearance of an object from the last time you observed it, notes on how different filters affect the appearance, and so on.

Before you create your ledger, give some thought to which data you want to capture. For example

  • If you're a dedicated double star observer, you might add columns for separation and position angle, primary and companion magnitudes and colors, and so on.

  • If you observe variable stars, you might add columns for magnitude and period.

  • If you observe mostly DSOs, you might add columns for magnitude and surface brightness.

  • If you're a Lunar observer, you might add columns for the dimensions of the features you log and the feature type (rille, crater, etc.).

Nothing says you have to complete all columns for all objects. If you use all of the columns we've mentioned, many will not apply to all of the objects you observe, but that doesn't matter. What does matter is that you record all of your observations to your ledger. In years to come, your ledger will provide a history of your observing career.