NOTES
Scopes and Cameras
I have pursued this program with the remote photographic option using photo services from Slooh.
Slooh operates a number of telescopes around the world and I have used several of them for this project. The Slooh locations are in Santiago, Chile (Latitude: S33° 16′ 8.4″ S33.269 / Longitude: W070° 32′ 2.4″ W070.534) and the Canary Islands (Latitude: N28° 17′ 58.92″ N28.29970 / Longitude: W016° 30′ 29.736″ W016.50826). Each location has several scopes installed.
Chile 1
Scope: Celestron 14″ EdgeHD 1400 Schmidt-Cassegrain Catadioptric (SCT) at f/11
Camera: Diffraction Limited SBIG, Model STL-11000
Chile 2
Scope: PlaneWave Instruments 17″ CDK17 (Corrected Dall-Kirkham) at f/6.
Camera: Finger Lakes Instrument Proline PL16803 Monochrome CCD Camera
Canary 1
Scope: PlaneWave Instruments20″ CDK20 (Corrected Dall-Kirkham) at f/6.8
Camera: Finger Lake Instruments PL09000
Canary 2
Scope: PlaneWave Instruments 17″ CDK17 (Corrected Dall-Kirkham) at f/6.8
Camera: Finger Lake Instruments PL16803
Canary 3
Scope: Celestron 11″ Rowe-Ackermann Schmidt Astrograph (RASA) at f/2.2
Camera: Celestron Nightscape 8300 One Shot Color (OSC)
Canary 4
Scope: Celestron 14″ EdgeHD 1400 Schmidt-Cassegrain Catadioptric (SCT) at f/11
Camera: Diffraction Limited SBIG STT-8300M
Processing
Slooh telescopes and cameras operate on fixed filter / exposure formulas based on the type of target in question. Sometimes they take luminance-only shots and at other times they take separate L,R,G, and B photos. (Slooh is fairly consistent, but not always. Sometimes I have expected LRGB shots but only received L photos. At other times one of the LRGB channels is missing.) I used a variety of integration techniques for the photos in this program. In general, if the photo shows any color, it is in the RGB palette. If it is grayscale, it is a luminance shot. In some cases I found it best to turn a color photo into a mono photo in order to bring out the contrast between dark space and the objects in the field of view. In all cases, Slooh returns Luminance shots with 50 second exposures and R, G, and B shots with 20 second exposures.
My chief post processing program is Pixinsight, which I have employed for stacking, color adjustment, file conversion, and plate solving.
Photo Quality
While I am quite happy with many of the photos I have used in this program, it is perhaps worth noting that they are not Astrobin quality “pretty pictures.” The scopes and cameras used to produced the photos are of very high quality. But the chief limiting factors have to do with length of exposure (these are very short exposures as astro photos go), the inability to manipulate filters (Slooh chooses and controls all of that), and image calibration routines (again, that is controlled by Slooh).
Targeting
When you order Slooh to take a photo, you have to choose your target from a star catalog. The guiding of the Slooh scopes is generally excellent. If you direct the scope and camera to a cluster listed in the more common catalogs (e.g. NGC, IC, or Messier) the cluster will most often lie in the middle of the frame. But Slooh does not have all of the specialized catalogs featured in this program (e.g. King, Berkeley, Trumpler, etc.). The workaround I developed was to use Sky Safari to locate the cluster and try to find a star either in the cluster of just adjacent to it. In most cases the targeted star came from the SAO catalog. It worked quite well, but one downside is that the star I targeted would often wind up in the middle of the frame, but not all or part of the cluster. I will try to identify photos in which this occurred and direct the viewer to where the cluster is located in the frame.
Trump Classifications
This program requires the observer / photographer to assign Trump Classifications to the clusters. You can read about the system here. The system measures three characteristics of open clusters — the degree of concentration of stars (from I to IV), the range of brightness of the cluster (from 1 to 3), and the number of stars in the cluster (“p” for poor = clusters with fewer than 50 stars, “m” for medium = clusters with between 50 and 100 stars, and “r” for rich = clusters with great than 100 stars). I place the classification just after the time and date of the exposure, using an abbreviation like this: “TV =”
As I began researching this, I quickly realized that different sources assign different classifications to the same cluster. This stands to reason. Robert Trumpler invented his classification system in 1930. Since then, huge strides have been made in scientific astronomy, and in a number of cases subsequent astronomers were able to correct or tweak Trumpler’s classifications because they had access to far more accurate data. According to the Open Cluster Handbook for this program, the Lund Catalogue of Open Clusters, published in 1985 and updated in 1988, is the gold standard for Trumpler Classifications. (The catalog is sometimes called the “Lynga Catalog,” after its compiler, Gosta Lynga.) I looked far and wide for a copy of the Lund resource, but to no avail. I finally found an online NASA database containing the Lynga work. It can be found here. One must play with the database readout criteria, but one can squeeze out the Concentration, Richness, and the number of stars in the cluster.
Finally, Trumpler added an “n” to the end of his Classifications if the cluster showed or was in an area of nebulosity. I could not figure a way to conjure up this suffix from the NASA resource. But based on the photo, I made the determination and added the “n” when I noted nebulosity.
Notes To Each Photo
Below each photo I place the relevant data in the following format:
Object Name (in the order they appear in the program guide)
Scope Used / Date of Exposure / Time of Exposure (UTC) / Trumpler Classification
Color channels info: L, R, G, or B (number and length of exposures); a note if I converted it to Grayscale
Comments — usually about the location of the cluster, my workflow, or other cluster features
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