For The Record

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At the end of my last post I mentioned a few things you should list in your logbook when observing open clusters so you could reference the information later and compare it to a more recent observation of the same object. That sparked an idea for this post and, as I thought more about it, I realized that it would be a good idea to start talking about keeping a logbook in general. I have kept observation logs since the early 1980’s and I’ll look back through them from time to time and recall some interesting things that happened while observing on a particular night or compare how improved my observing skills have become or even how improved telescopes have become since those early days as an backyard astronomer.

So, let me ask you this question; do you keep an observation logbook? I hope you answered yes to this question because it really does help you to become a better observer. Taking notes on what you see makes you really take a good look at the object in the eyepiece. Looking back on those early observing notes I noticed that I always described objects with the same few words like, “striking”, “great”, “bright” or “faint”. Okay for a first impression but not very descriptive about what I really saw. So, I decided I would start taking notes based on a few parameters. Over the coming weeks I’ll get into more detail about observing and logging double stars, star clusters (open and globular), nebulae and galaxies. But for now, I’ll start with what I call “Session Notes”. These are notes about the circumstances surrounding the night’s observations such as location, sky conditions, who, if anyone, is present with me and any personal notes I care to make about the night.

Session Notes

There are many ways to keep a logbook. I keep it relatively simple, my logbook is a wire bound book of sketch paper where I’m free to write anything I want and make a sketch if I feel so inclined.

At the top of the page I list the start time in local time and the date in double date format and I’ll convert to UTE at a later time. It typically looks like this:
Date: March 16/17 2014
Start Time: 9:35 PM EDT – End Time: (fill this in at the end of the night).

Next is the location where I’m observing from. Most of the time its right here at the 90 Millimeter Observatory but from time to time I’ll drive out to a dark sky location so I’ll make note of it here. You can use a physical description or latitude-longitude description. Use whatever works for you.

Telescope: If you have more than one telescope, it becomes important to make note of which one you’re using on this particular night. Looking back at a few older observations when I didn’t note the scope I was using I thought to myself, was that with the 90mm f/10 or the 120mm f/8.5? I could guess based on the magnification a particular eyepiece gave me but its just easier to make note of which telescope was being used.

Next is the NELM (Naked Eye Limiting Magnitude). This is the faintest magnitude star you can see without optical aid. Its best to wait until your eyes reach dark adaption to record this. If you need a chart to help you with the limiting magnitude, AstronomyLogs.com has a couple of downloadable charts that I have found to be very handy.

Now on to seeing, which is a scale noting how much the Earth’s atmosphere perturbs the images of stars. The scale is a five-point system with 1 being the best seeing and 5 being the worst seeing conditions. It’s easy and it goes like this:
(I.) Perfect seeing, without a quiver.
(II.) Slight quivering of the image with moments of calm lasting several seconds.
(III.) Moderate seeing with larger air tremors that blur the image.
(IV.) Poor seeing, constant troublesome undulations of the image.
(V.) Very bad seeing, hardly stable enough to allow a rough sketch to be made.

The last entry here is transparency. This is a measure of particles in the atmosphere affecting viewing conditions. I use the Saguaro Astronomy Club (SAC) scale. It’s a scale from 1 to 10 and goes like this:

0   completely cloudy, no stars seen (why are you out?)

1   more than 50% of the sky is cloudy

2   more than 25% of the sky is cloudy, less than 50%

3   more than 10% of the sky is cloudy, less than 25%

4   no clouds but hazy, only brightest stars seen down to 4th magnitude

5   somewhat hazy, some fainter stars seen, to mag 5;
Milky Way visible only in brighter regions

6   not visibly hazy but Milky Way visible only in brighter regions
(Sagittarius, Cygnus, Norma + Crux); stars seen to mag 5.8

7   fainter stars, equal to mag 6.0 are seen and the fainter parts of the
Milky Way seen with averted vision, Zodiacal light seen with averted vision

8   stars fainter than mag 6.0 are just seen and fainter parts of the Milky Way
are more obvious, Zodiacal light is seen with direct vision

9   stars fainter than mag 6.0 are seen with direct vision and so are faint portions of the Milky Way (Lyra, Libra), gegenschein seen with averted vision

10   overwhelming profusion of stars, Zodiacal light and the gegenschein form
Continuous band across the sky, the Milky Way is very wide and bright throughout

Finally I’ll add a few personal notes about the night in general like, how I feel, who, if anyone is there, any issues I’m having with equipment, etc. It may seem like a lot at first but by doing this initial step you give yourself time to dark adapt, time for the telescope to cool down and just relax for a few minutes be for settling down for a good night’s observing.

Next week I’ll talk about recording deep sky objects and what to look for in each type.

Clear Skies!

Jason and the Argonauts

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PuppisAnother one of my all time favorite movies tells the tale of a legendary Greek hero who leads a team of intrepid adventurers in a perilous quest for the legendary Golden Fleece.  Their ship, the Argo, was once represented by a large constellation in the southern sky call Argo Navis and was only one of the 48 constellations listed by the 2nd century astronomer Ptolemy. Argo Navis or, more simply Argo, has since been divided into four constellations by the French astronomer Nicolas Louis de Lacaille who sub-divided the constellation as Carina (the keel), Puppis (the stern), Vela (the sails) and Pyxis (the compass or mast). Puppis is the largest of the four constellations and is one of the 88 modern constellations recognized by the International Astronomical Union.

Puppis constellation map

Puppis
constellation map by IAU and S&T magazine.

When Lacaille divided up Argo Navis he kept the Bayer designations so therefore Carina has the α, β and ε and Vela has γ and δ, and Puppis has ζ,  π, ρ and a few others.  This week we’ll take a look at Puppis and a few of the targets visible in small telescopes and even binoculars. Since the Milky Way flows through Puppis, there are a few interesting open clusters to explore and a planetary nebula.

Puppis may be a little tricky to locate for mid-northern latitude observers as it resides in the southern hemisphere between -10° and -50°. You’ll need a clear view of the southern horizon and a dark sky as the constellation is easily lost in light pollution. The brightest star here is ζ Puppis (zeta Puppis) with an apparent visual magnitude of 2.2. It’s interesting to note that zeta Puppis is one of the few O-class stars that can be seen with the naked eye. At a distance of around 1,090 light-years it is the 62nd brightest star in the sky. The star is also known as Naos, from the Greek vaic, meaning “ship”. It has a radius about 14 times that of our Sun and is 550,000 times more luminous. Think about that when you observe zeta Puppis.

M46/NGC 2437

After publishing his first list covering M1 through M45, Charles Messier added M46 on 19 February 1771, just three days after presenting his list to the academy along with a few additional objects. Locating M46 can present a bit of a challenge if you observe under light polluted skies. The shortest path to M46 is to locate the 3.9 magnitude star α Monocerotis (alpha Monocerotis) and move your telescope 5° south. You’ll see two objects come into the field of view, M46 and M47. In the 90mm, f/10 refractor at 48x, M46 is a faint collection of about 30 stars ranging in magnitudes 9 to 12. Larger telescopes may reveal the planetary nebula NGC 2438. This is actually a foreground object and not part of the cluster. This is a very rich open cluster of about 500 stars, most too faint to see in small telescopes. The cluster spans about 27’ (arcmin) across.

M47/NGC 2422

This cluster is located just about a degree west of M46 and as you may have noticed it passed through the field-of-view in route to M46. While not nearly as rich as it neighbor, M47 stands out well even under light polluted skies. Boasting a mere 50 stars, M47’s apparent magnitude is around 4.4 but at 25’ its surface brightness is just magnitude 11. The 90mm f/10 refractor at 33x reveals 15 stars of magnitude 5.5 and 6.0. The cluster was originally discovered by the Italian astronomer Giovanni Batista Hodierna around 1654 and rediscovered by Charles Messier on 19 February 1771. An interesting note on M47 is that Messier specified the coordinates for the M47 with respect to the star 2 Puppis, but there is no cluster in the position that he indicated. The position, however, might match that of NGC 2423. Discover more about Messier’s error at www.seds.org.

M93/NGC 2447

Our last open cluster for this post is M93 which is around 10 light-years in radius and about 100 million years old. M93 is one of the last discoverers by Charles Messier in 1782. You’ll need to consult your star atlas for a little help locating this cluster. Locate Omicron1 and Omicron2 Canis Major on your atlas about 8 deg SE of Sirius, M93 is on the same parallel (declination) as Omicron2, but 10° east, near Xi Puppis. M93 is a little difficult here at the observatory for even our 120mm refractor. In the 90mm f/10 at 33x the cluster shows a hand full of stars despite being a magnitude 6.2 cluster. There is a strong concentration toward the center, somewhat elongated SW to NE.

Remember, when you observe open clusters to note in your logs the number of stars in the cluster and the concentration of the stars. Also note any star or stars that may be a different color and its location relative to the cluster (i.e. “there is a magnitude 10 orange star on the south edge of the cluster”). Try to count the stars in the cluster and resist the temptation to guess at how many stars there are. Notes like this make it more interesting when you observe the same cluster later under different conditions or a different telescope.

Most of all get out there with your small telescope and relax and have some fun. Even if you have to contend with light pollution there are many deep sky wonders to enjoy. Invite your friends and neighbors too. Who knows, you may turn someone into a light pollution advocate.

Clear Skies!

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