(IAAC) Obj: M44 Beehive - Inst: 10x50 binoculars, 20x64mm refractor


Observer: Matt Leo
Your skills: Beginner (< one year)
Date/time of observation: March 29, 1998 2030 EST
Location of site: Melrose, MA (Lat 42 30', Elev )
Site classification: Suburban
Sky darkness: 4 <1-10 Scale (10 best)>
Seeing: 4 <1-10 Seeing Scale (10 best)>
Moon presence: None - moon not in sky
Instrument: 10x50 binoculars, 20x64mm refractor
Magnification: 10,20
Filter(s): None
Object(s): M44 Beehive
Category: Open cluster.
Class: open cluster
Constellation: TAU
Data: mag   size 
Position: RA 8:40  DEC 19:38
Nicely placed this evening early evening viewing, at about 60 degrees altitude,
high enough to be visible despite skyglow from Boston to the south. Very
pretty, and easily located by star hopping from castor and pollux (Start at
castor, take one step to pollux, take two more steps, then take one step upward
so the entire path looks like a check mark; this puts you pretty much dead on
the cluster).

After located this cluster with my 10x50's I tried out a 20x64 homemade
refractor which I built from a surplus gun sight objective (64mm f3) and a
10mm Celestron Plossl.  This scope is housed in a short piece of PVC tubing
and mounted on a video tripod; all very rickety.  This turned out to be a
good object lesson in the value of binoculars. Although I could locate the
cluster in about ten seconds with the 10x50s, it probably took me fifteen
minutes (and some neck ache) to find it in this relatively low power
refractor.  The backlash on the video tripod also made it difficult. It is
unlikely that without the aid of binoculars I could have found this cluster;
it isn't easily visible to the naked eye in the seeing conditions in my

Once I managed to locate the cluster, the 20x64 magnification and 2deg, 48' 
field of view turned out to be almost ideal for viewing this cluster; 
possibly  a slightly wider field of view might be nice.  I tried counting 
stars and ended up with about 45; about a quarter of this count is somewhat 
doubtful, since they weren't visible with direct vision and may have been 
double counted. I couldn't hold the binocs steady enough to get a count, 
but I'd guess that about half as many stars were visible, and certainly 
none of the averted vision stars.

This was the first satisfactory observation I've made with the 20x64; I 
purchased the uncoated objective for about $10.  However, stars, 
particularly bright ones, have a halo around them (not a diffraction 
pattern, more like a compact circle of radial rays -- kind of like a daisy).
Since daytime contrast is poor, I guessed that this was a reflected light
problem.  I blackened the rear wall of the tube (where the eyepiece is 
mounted), and roughened it up with blackened sawdust.  This seems to have 
improved the problem somewhat, so that no halo was visible on the relatively 
dim stars of the Beehive, although 2nd magnitude stars like castor still show 
this problem.
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