The Astronomical Log Book by Martin McKenna


So how long have you been into astronomy? Take a quiet minute and reflect back over your observing career. Do you remember the excitement of getting your first telescope? The first time you saw the rings of Saturn? What about those spectacular Auroras, Meteor showers, Fireballs, that great Comet or that naked eye Sunspot you seen as the Sun set into a murky western sky on a gorgeous Summer evening? Better yet, did you keep a written record of these observations? Astronomy is not just about observing, it’s an experience, a life style but more than that it is a collection of priceless memories.

I have only been observing the sky for a decade now however since 1997 I decided that I would start recording my observations in an astronomical log book, in hindsight this was one of the best decisions I ever made. Today I am nearing the end of log book number 5 and just before Christmas I decided that I would read through each and every one of them.

To say that I was shocked would be an understatement. I felt very confident regarding my recollection of all the things that I experienced in the night sky however that list in my head turned out be but a leafless branch on a fully blossomed towering Oak tree of observations and memories that I did not even know existed but which lurked deep in my subconscious unbeknown to me. Reading through my early pencilled and penned words opened a gateway of astronomical observations and delights that not only include my own catalogue of Celestial objects but which documented my own thoughts and feelings through time. I was surprised by just how much my observing programme has grown and evolved but even more than that I was shocked by how much I had grown and evolved as a person through that decade. My own personal philosophy to observing and to life as well as the people around me through that 10 year period staggers me and if it were not for my records all these ups and downs would have been lost for ever. Since humans first looked at the stars they have kept records of the various transient phenomena that they have gazed upon with both astonishment and even fear, first on stone then on paper through the ages. Things have not changed since then, we still observe the sky, we still are at awe with what it can reveal to us at anytime without warning and so we must continue to document what we observe as it is our duty as self appointed watch men and watch women of the night sky.

I have been in conversation with various amateur astronomers about this subject and many wished they could start an observing log but never quite got around to it, so it is with this in mind that I decided to write this short article in the hope that I could encourage others to do the same. I hope some of you will begin to do so and I hope it will be a treasure trove of information for you as it has been for me. You won’t regret it…lets go!




You can use what ever you like to record your observations…

* Note books

* Individual A4 pages in a binder

* If you are active with a computer you can store your records on your hard drive or onto disk but always make sure you back up your data on a regular basis.

I am sure you will come up with your own medium that suits your needs. I prefer to the use the large annual day to a page diaries as they can hold an incredible amount of information. I personally prefer the written word compared to the computer as I can access its contents quickly plus I find that staring at a computer monitors glare can be damaging to my eyes and hampers my dark adaptation. I always carry a small pocket sized note book in my observing jacket were I can rapidly record information and sketches while at the eyepiece in the field. Later that night or the next day I would then transfer the information in a more neat and detailed manner in my log in the comfort of indoors. This is why many observers are put off as it can be very time consuming to do however it need not be. If you make it a part of your daily routine then it will become second nature with practice. Its up to you how detailed you want your records to be, an entry can be only one or two lines long or it can fill two pages… it is really up to you. Keep in mind that recording your observations has two purposes


1) The first is for your own use so that one day you can look back on your observing achievements.

2) The second is for scientific reasons. You may never know when your observations will be needed by a professional. Your detailed description of a fireball, you magnitude estimate of a variable star, Comet or Nova could be very useful if there has been a gap in the data plus observations of the Aurora Borealis can be important to an individual who is researching there frequency in a given latitude and time frame so please keep this mind. Try to update your latest session as soon as possible to maintain accuracy plus the longer you leave it then the less chance there is of you doing it at all…remember observations locked away in your mind are not observations at all and are of no use to anyone including yourself!




You will need to record some if not all of the following information…

* Time of the beginning and end of session or midpoint of an astronomical sketch. All times should be in UT or at least local time.

* The double date, Month and year e.g.: 17/18th. Jan. 2006

* Telescope type, focal ratio or length, eyepiece used, magnification, apparent FOV plus you might also want to mention if you used a diagonal and comment on polar alignment and on the accuracy of your motor drive or GO-TO encoders/drives. Keeping notes on your telescope’s performance, modifications and upgrades can be great to look back on.

* Your Target: give a detailed physical description of your target; this may also include a sketch or image you took.

* Make a note of the local weather conditions. Include a transparency and seeing scale, % of cloud cover, the presence of Moonlight and any mist, fog, snow, high level clouds and so forth.

* I try to always include my own thoughts and feelings during a session regarding my equipment, the sky and how I am feeling which adds that personal touch.

* I always record my location whether it be the front or back garden, the country or a specialised area like when a group of observers meet together for an all night session. I also include the names of anyone who is with me, their scopes and their observing agenda so I end up recording not just my own work but the work of others as well.

* Miscellaneous: it’s the little things that make records of high sentimental value like keeping notes of the environment around you. You may want to include…nocturnal formations of Geese, any visits in the night from Foxes and other wildlife, any human visitors, heavy frosts, heavy snow falls, gale force winds, lightning, light pollution, chimney smoke, areas of the sky blocked  by trees and houses , power failures, collimation trouble, car headlights, human noise, any personal things happening in you own life, the effects of work or other people on your observing time, future plans and purchases  etc.

If you are involved in a specialised field or do observing in a serious way then you NEED to record everything you do. Anyone who observes Variable stars, hunts for Novae or Comets or specialises in astrophotography of any description needs to document the precise details of their work and equipment settings. When I search for comets I always mention the constellation sections I sweep through, the names of the Messier, NGC and IC objects swept up, any suspects that need to be checked out, sketch and describe any new objects I have never encountered before, comment on how systematic I am, if I am sweeping to fast or slow, how far I am from the sun, if I am near the Ecliptic, the compass point in the sky, Moon phase and position, limiting NE magnitude, any internal reflections or ghost images in the FOV, light tresspass, any planes, helicopters, birds or insects that pass through the field, my mind set, mood and health. I also record any telescopic meteors and satellites, fireballs, Auroras, Gegenschein, Zodiacal light and other atmospheric phenomenae I have noticed while comet hunting. Never forget to include any naked eye observations you make such as the brightness and structure of the Milky Way, and any Messier objects seen without optical aid. Each of these different objects gets its own title and entry in my log book even when they are part of same session.




In order to save time you may want to code your notes. I code everything I do for this very reason. Use personal jargon, ½ words, numbers and letters to aid this process, naming telescopes also helps but be sure and write a translation of your code system within your log book so others can understand it. Here’s an example from my own log book…

S/1768 E-M CHP 27/28.12.2005 23.30 – 00.56LT (1hr 26mins) T7 57X SWA32mm B/Country CS/631.

Translation: Tonight I began recorded observing session 1768 which began in the evening and ended in the morning from 11.30 to 00.56 local time on Dec 27th/28th. I spent 1 hour 26mins searching for comets (CHP stands for my comet hunting project) with my 16” F/4.5 dobsonian Reflector using a Super Wide Angle 32mm 2” eyepiece at a magnification of 57X which I know has a FOV of over one degree. The session took place in my back garden then after wards in the country. It was comet sweep number 631. I then go on to give a detailed written description of the session as outlined above.


Example 2.


S/1548E-M NLC 2/3.7.2005 23.24 – 02.30LT B8, NE, Camera, H/B/P/S 4th Display

Translation: Recorded observing session 1548 Evening – Morning which took place from 23.24 to 02.30 local time on the 2nd/3rd of July 2005. I observed a Noctilucent Cloud Display that was present during this time period using 8X22mm binoculars, Naked eye and Camera. I observed it from my bedroom window, back garden, a nearby football pitch followed by a building site that allowed for a panoramic elevated view of the display. You can see that coding does help a lot!




 If you have been flirting with the idea of beginning an astronomical log book then I hope that this short article has rekindled your enthusiasm for the project. As you can see it is a very worthwhile investment in your time and can only fuel and compliment your observing. In fact, there have been times when I made myself do more observing just so I would have something else to include in my log so it actually made me observe more! On a personal level my own log books have been of incalculable value to me. Many times I have found a distant galaxy in the sky but I may have been uncertain if I had encountered it before however because I numbered the pages and indexed my log books I was able to ascertain within minutes if I had found that object before saving me valuable time. My log has also enabled me to gather my own observing statistics such as the number of comets, auroras, Noctilucent Cloud displays I have seen as well as the number of observing sessions I have completed and an accurate compilation of the hours I have spent searching for comets, these also can tell me how much I have done every year, month, including the least and most done on a single night. Through my 5 log books I have been able to see a story emerge that not only documents my observing, my own growth but also variations in weather patterns from year to year as well as the slow but constant growth of light pollution in Maghera which I fear will end all observing from here in the not to distant future if the expansion rate keeps increasing. I have learned that we get a significantly larger number of clear nights here than is forecast by the weather, on a typical good night the trans is 8 or more out of 10 with mag 6.5 stars visible on a nightly basis . I have also learned that we have the luxury of a significant number of Aurora displays that often do not coincide with the charts!

I have experienced so many thrills and disappointments in astronomy over the years that I could not do them justice here but if it were not for my record keeping I would have lost most of my most cherished memories in astronomy. Here are a few examples…

Feb 2005. One of the clearest nights I have ever seen. Vivid dust lanes visible in the Milky Way and mag 7.0 stars easy with naked eye. That evening while comet hunting I found for the first time the Veil nebula in Cygnus followed mins later by Comet Encke. I said in my log book that evening that the sky was similar to what one must get in Arizona!

Dec 2002 During the Geminid meteor shower on a very cold frosty night I saw countless spectacular fireballs before dawn. Two of them made me instinctively duck while another left a glowing smoke trail in the sky 15* long that stayed in the atmosphere for 15mins!

Aug 2000 After spending 8 hours searching for comets one night (only had started 3 months earlier) I accidentally ‘discovered’ Comet Encke very close to the sun showing stunning pink, red and green colours! This comet was picked up in the only clear strip of sky at the horizon as the rest of the sky was covered with dense fog. This remains the most exciting thrill for me in astronomy!

Dec 1998 I got a 4.5” Tosco reflector for Christmas. I loved it!! Must have spent a week indoors just looking at it when I should have been outside observing through it. My first sight of M81 and M82 was incredible!

Aug 1997 I woke up late on this summer night and decided to watch the stars from my bedroom window. Shortly bright unearthly blue search beams lit up the northern sky blocking out the stars. I was blown away by the sight. I honestly thought it was the end of the world. After a little research the next day I realised I had just seen my very first Aurora Borealis display!!


I can live through these experiences and hundreds like them from a quick scan through these logs. These memories are more than priceless and every night a new memory is captured. When I am of elderly age I will be able to look back on these books and the future books still to be written and feel pride. Astronomy is an amazing passion which can be very intimate; it forges your mind and opens doors to bigger and better places of the mind… And remember it’s not just an observation you are recording….it is also part of yourself!


Clear Skies!

Martin McKenna
EAAS Member