Star Party Preparation

The Hodges Garden Star Party is the week after next and I thought it would be appropriate to discuss just how I prepare for a star party. I have found over the years that in order to maximize your experience at a star party, you need to be very well prepared. Preparation not only takes the form of the equipment that you will take, but also what you want to observe while at the party.

 Hodges Garden is a little unique as this will be the first time I that I have attended this event. So I started my preparation by a careful review of the website. This particular star party is hosted by the Baton Rouge Astronomical Society. It is held at Hodges Garden State Park in west central Louisiana. The party is held from March 30th through April 3rd. There are limited facilities and as stated on the website, "camping is at its most basic."

A quick look at Clear Sky Clock for a nearby site shows that the site has reasonably dark skies with a Bortle rating of 3. The clear sky clock also shows that humidity is a potential issue after midnight on most nights. This is important, as the observing site does not have electricity on the observing field. This means no hair driers to fight the dew. Luckily for dob owners, dew is not much of a problem except for the finder scopes and eyepieces.

The absence of electricity is important as I normally rely on my lap top for star charts and observing lists. So, it looks like I will need to plan on printing out my observation lists and bringing my Sky Atlas 2000. I will also bring both volumes of The Night Sky Observer's Guide. This is a really good reference for those faint fuzzies that I am hoping to see.

So, that brings us to figuring out what to observe. I am always torn between quantity and quality of the observations. Do I try and log as many objects as I can, or do I stop and spend quality time with each object, perhaps even sketching them. I do not have a great answer for this, and this is probably why I still struggle. I will say, that the answer depends on the weather forecast. If the weather looks good and I will get multiple nights to observe,then I am more likely to take my time with each object. If the forecast shows that there will be a limited window for observing, then I will typically go for quantity.

There was not a mention of an observation list on the website, so I guess I need to develop my own. As I have been working on the H400 list, it makes sense to see what damage I can do on that list. Utilizing my charting software, Cartes du Ciel, I look to see what is going to be visible from 8PM to 1AM. I utilize a 5 hour window as I usually fade pretty fast after midnight unless the viewing is truly spectacular.

The other criteria that I use when deciding what to view is the altitude of the object. I want to observe objects when they are at least 30 degrees above the horizon as this reduces the air mass that I am looking through. Now some of the southern objects will not meet this criteria, but I will just plan on observing them when ever they reach the zenith.

So as I look at the possibilities there are two groups that become evident. The first group is the H400 objects in   Mon, Pup, CMa, and Gem. There are 33 objects still on my list. These objects are primarily open clusters embedded within the Milky Way. I think that this list will be achievable if I get 2 good nights to observe.

The second group consists of mostly galaxies in constellations that will be rising through the evening, Leo, UMa, Hya, Sex, Crv, Crt, Vir. There are a lot, 112 to be exact, of objects that are still on my list in these constellations. I think observing some of these should be on the list as they should really shine at this dark site.  Now, I can't get everything, so I need to pare the list down to just a couple of constellations. Hya, Crv and Crt just have 1 object a piece left on the list, so I should go and get these out of the way. Leo has 18 left on the list and it will be pretty high in the sky most of the night and so I will include it.

So, now I have my completed list. 54 objects in total. If I get 4 nights of good weather, then it should be doable. If I get less than four nights, then my strategy will be from the top down as there will be other nights in April and May that I could use to get the objects at the bottom of the list.


NGC RA RA Dec Dec Tp Con Mag.
2204 6 13.5 -18 35 OC CMa 9.1
2215 6 18.4 -7 16 OC Mon  8.6
2232 6 24.1 -4 43 OC Mon  4
2244 6 29.7 4 54 OC Mon  6.2
2251 6 32 3 24 OC Mon  8.5
2264 6 38.4 9 56 EN Mon  4.7
2286 6 45.1 -3 7 OC Mon  8
2301 6 49.2 0 31 OC Mon  5.8
2304 6 52.3 18 5 OC Gem  10.1
2311 6 52.8 -4 31 OC Mon  9.6
2324 7 0.4 1 8 OC Mon  8.8
2335 7 4.2 -10 0 OC Mon  9.1
2343 7 5.9 -10 34 OC Mon  8
2353 7 12.3 -10 12 OC Mon  5.3
2354 7 12.2 -25 38 OC CMa 9
2355 7 14.2 13 52 OC Gem  9.5
2362 7 16.6 -24 52 OC CMa 10.5
2371 7 22.4 29 35 PN Gem  11
2372 7 22.4 29 35 PN Gem  11
2395 7 24.3 13 41 OC Gem  9.4
2420 7 35.4 21 41 OC Gem  10.2
2421 7 36.3 -20 37 OC Pup  9
2423 7 34.8 -13 45 OC Pup  6.9
2440 7 39.9 -18 5 PN Pup  11.5
2479 7 54.7 -17 35 OC Pup  9.5
2482 7 52.8 -24 10 OC Pup  8.7
2489 7 56.2 -29 56 OC Pup  9.4
2506 7 57.7 -10 29 OC Mon  8.5
2509 7 58.5 -18 56 OC Pup  9.3
2527 8 3.2 -28 1 OC Pup  8
2539 8 8.4 -12 41 OC Pup  8.2
2567 8 16.6 -30 29 OC Pup  8.3
2571 8 16.9 -29 35 OC Pup  7.5
2964 9 40 32 5 GX Leo  11
3190 10 15.4 22 5 GX Leo  11.3
3193 10 15.7 22 9 GX Leo  11.5
3226 10 20.7 20 9 GX Leo  11.5
3227 10 20.7 20 7 GX Leo  11.4
3395 10 47.1 33 15 GX Leo  12
3489 10 57.7 14 10 GX Leo  11.5
3521 11 3.2 0 14 GX Leo  10.5
3593 11 12 13 6 GX Leo  11.3
3607 11 14.3 18 20 GX Leo  9.6
3608 11 14.4 18 26 GX Leo  11.1
3626 11 17.5 18 38 GX Leo  10.5
3640 11 18.5 3 31 GX Leo  10.7
3686 11 25.1 17 30 GX Leo  11.4
3810 11 38.4 11 45 GX Leo  10.8
3898 11 46.7 56 22 GX Leo  11.5
3900 11 46.6 27 17 GX Leo  11.5
3912 11 47.5 26 46 GX Leo  11.5
3962 11 52.2 -13 42 GX Crt  11.3
4027 11 57 -18 59 GX Crv  11.5
5694 14 36.7 -26 19 GC Hya  11

In a future blog I will tell you how successful I was, until then,

Clear skies;
rw

Open Star Cluster Observations

One of the joys of being a visual  observer is in describing how an object appears. This description will vary according to the light (dark) conditions, the magnification, the field width and the dark adaption of the observer. It will also vary based on the amount of time an observer spends directly observing the object. It is pretty safe to say that no two observations will be exactly alike, but each are equally valuable as a description. So, this week, I want to talk a bit about open star cluster descriptions and how I go about recording the visual image

My first step in observing an open cluster is to inspect the cluster under very low magnification and a wide field of view. For me this is my 30mm wide field which yields 102 arc minutes at 40X magnification. With this eyepiece, I inspect how the cluster is situated within the star field. Is it highly concentrated with respect to the surrounding field, or is it fairly loose and almost indistinguishable against the field stars? Robert Trumpler developed a classification system for describing this. Trumpler assigned a Roman Numeral to describe the concentration and detachment of the cluster. Here is the classification that Trumpler used:

     I Detached with strong central concentration
    II Detached with little central concentration
   III Detached with no central concentration
   IV Not detached but apparently like a strong field concentration

At this point, I increase the magnification so that the cluster fills the majority of the field of view of the eyepiece. Using this higher magnification, I record the dimensions of the cluster. If the cluster is not circular then I describe the shape and which direction it is elongated in.

At this point, I estimate the number of stars that appear to be associated with the cluster. If the cluster is not detached from the background, or foreground stars then this can be difficult. Trumpler divided clusters according to the number of stars:
 
    p     less than 50 stars
    m    50 - 100 stars
    r      more than 100 stars

Trumpler used the Lick Observatory equipment for his survey, so don't expect to come up with the same number of stars that he did. Often if the cluster is very rich in faint stars, then it appears more as a mottled effect. If this is the case then I just record it as such.

The next aspect to observe is the variety of brightnesses and the colors. The higher proportion of red stars indicate that the cluster may be older than a cluster with more blue stars.  Observe the brightness ranges. Are they all the same magnitude, or is there a significant difference in magnitudes. Trumpler used a scale of 1 to 3 to classify brightness differences 1 being very little difference in brightness and 3 being a large difference of several magnitudes.

So now for some examples:
NGC 1647 is an open cluster in  Taurus. I have described this cluster as having many stars, barely concentrated with a density higher than the background field. The stars are mostly the same brightness.

Trumpler classified this cluster is II-2-r which translates to detached with little central concentration, minimal range in brightness, and more than 100  members.




NGC 2360 is an open cluster in Canis Major. I described this as " Highly concentrated open cluster, 2 dozen brighter stars, many,many fainter stars. density higher than surrounding area"

Trumpler classified this as II-2-m - Detached with little concentration, 50 - 100 stars, minimal range in brightness.






NGC 457 is a really nice OC in Cassiopia. My description goes like this: Nice irregular shaped open cluster. Elongation N-S direction with 34 Cas and its companion on South side. The double is a yellow and green pair. Many stars of different brightness, slightly concentrated with density higher than surrounding area.

Trumpler classification is I-3-r - detached with strong central concentration, large brightness differences with more than 100 stars.




The trick with the descriptions is to give as much detail as possible. You will find that the more descriptive you are, the more you will remember these little gems.

Next time I will talk about getting ready for a star party....

Clear skies,

rw