STARLOG

A Tale of Two Clusters

September 7, 2004

Observer: Tom Campbell
Location: Iola, Kansas (Long: 95°24'W Lat: 37°55'N)
Equipment: Discovery DHQ 8" dobsonian
Eyepieces: 1.25" Plössls - 25mm (49x), 15mm (81x), 10mm (122x), 6mm (203x)
Time: 10:00pm - 11:30pm CDT (03:00-04:30 UT)
Transparency: Clear (9/10) [No Moonlight]
Seeing: Stable (8/10)
Weather: Temperatures in the low 60s. There was no breeze.


Observing Summary:

  • DELPHINUS: γ, Σ 2718
  • OPHIUCHUS: NGC 6633
  • SERPENS: IC 4756


    • Tonight, my primary goal was to search for some easy binocular targets for my astronomy class. But the night was so clear, I decided to go ahead and set up my telescope. While its mirror was adjusting to the outside temperature, I observed and wrote down a list of several binocular objects (mostly Messiers and some wide doubles, but also a few other goodies).

    After spotting IC 4756 and NGC 6633 through binoculars, I couldn't resist the temptation to look up these old friends again with my telescope. It had been a couple of years since I wrote them up in an observing log.



    IC 4756 Serpens Open Cluster 10:40pm CDT
    Mel 210 RA: 18h 38m 54s Dec: +05° 26' Mag: 4.6

    This open cluster appeared large, and even at 26x, it more than filled the field of view. Most of the stars were about the same magnitude (moderately faint), and several dozen were visible. A few bright stars were interspersed throughout the cluster, but they appeared as foreground stars.
     
     
    NGC 6633 Ophiuchus Open Cluster 10:45pm CDT
    Mel 201 RA: 18h 27m 42s Dec: +06° 34' Mag: 4.6

    This open cluster was smaller than IC 4756, but it still looked good at 26x. A few dozen stars were visible. The cluster appeared elongated, with stars of varying brightnesses.

    Through my binoculars, both IC 4756 and NGC 6633 could be seen in the same field. This pair of clusters was a study in contrasts. Although both are listed at magnitude 4.6, IC 4756 is large and full of dim stars, whereas NGC 6633 is somewhat compact and full of brighter stars. I had to use averted vision to see the stars in IC 4756, but several of NGC 6633's stars were easily seen with direct vision.
     
     
    S 2718 Delphinus Double Star 11:30pm CDT
      RA: 20h 42m 36s Dec: +12° 44' Mag: 8.0, 8.0

    This double was fairly close. Although I could split it at 49x, the best view was at 88x. Both stars appeared very similar in magnitude and white in color. It reminded me of a pair of beady eyes staring back at me through the eyepiece.
     
     
    g Gamma Delphinus Double Star 11:35pm CDT
    S 2727 RA: 20h 46m 42s Dec: +16° 07' Mag: 4.3, 5.1

    The brighter star of this pair appeared yellow, while its companion appeared white. It could be split at 49x, but the best view was at 122x.
     

    After reviewing my records, I discovered that I had reached a milestone. Tonight's observation of S2718 marked the 450th unique object I have recorded since I began writing StarLogs in January, 2000. The very first object I logged was another double, in a sense: the shadow of Earth on the Moon during a total lunar eclipse. My pace has been somewhat leisurely, but under the humid skies of Kansas, I think an average of 100 new objects per year is pretty good.