Telescope Reviews: Binocular Icon 27 : IC 4756 meets NGC 6633.

A low power binocular can sometimes frame two or more objects in one field of view. These wide fields can provide very rewarding observations. Such is the case with IC 4756 in Serpens Cauda and NGC 6633 in Ophiuchus. According to my sky charts they have an angular distance of only 3°. Starting point for this query is Theta Serpentis. Point your binoculars halfway between Zeta and Lambda Aquilae. There you’ll find the 4th magnitude Zeta Serpentis. Now move the binoculars 4° to the west and a little to the north until the soft glow of IC 4756 shows up. IC 4756 can be tricky to see at first. Just move the binoculars another 3° along the same direction until NGC 6633 comes into view. NGC 6633 is the most conspicuous but also the smallest of the duo. Four brighter stars are embedded in an elongated haze of fainter cluster members. Now that you have identified NGC 6633, look for the large pale glow of IC 4756. This cluster measures almost a full degree across. My 8x56 binoculars show many 9th and 10th magnitudes pinpricks framed by a few brighter stars. The cluster comes best into its own with averted vision. Then IC 4756 looks like a faint cloud of diamond dust. With both clusters in the same field of view, it is interesting to compare them. NGC 6633 is the more condensed cluster of the two. IC 4756 is believed to measure 20 light years across at a distance of 1300 light years. NGC 6633 is 1000 light years away from us.

Site : Bütgenbach, Belgium
Date : June 29, 2008
Time : around 00.30UT
Binoculars : Bresser 8x56
FOV: 5.9°
Filter : none
Mount : Trico Machine Sky Window
Seeing : 2,5/5
Transp. : 4/5
Nelm : around 5.9
Sketch Orientation : N up, W right.
Digital sketch made with Photo Paint, based on a raw pencil sketch.

(Note: if the sketch does look too dark on your monitor, try to darken the room.)

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Rony

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