(IAAC) Obj: Mel 25 (Hyades) - Inst: Vixen 9x63 binoculars

anonymous at sedna.atmob.org anonymous at sedna.atmob.org
Mon Jan 16 00:03:18 EST 2006


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Observation Poster: Stéphane Meloche <stephanemeloche at videotron.ca>

Observer: Stéphane Meloche
Your skills: Intermediate (some years)
Date/time of observation: 2006/01/04 6h18 UT
Location of site: Coaticook (Qc), Canada (Lat , Elev )
Site classification: Exurban
Sky darkness: 5,2 <Limiting magnitude>
Seeing:  <1-10 Seeing Scale (10 best)>
Moon presence: None - moon not in sky
Instrument: Vixen 9x63 binoculars
Magnification: 
Filter(s): 
Object(s): Mel 25 (Hyades)
Category: Open cluster.
Class: 
Constellation: Tau
Data: mag 0.5  size 330'
Position: RA 04:27  DEC 16:00
Description:
I devoted myself to a star counting, just to see what I could draw from the exercise.  The main problem is to determine which are the stars belonging to the cluster and which do not form part of it.  I limited myself to the shape out of V of the cluster and the brightess stars located very close to it. I have to be very methodical, considering the size of the cluster, exceeding the field of 5,4° of my instrument.  Moreover, dewed eyepieces made the work more difficult.  After counting, I counted 95 stars of any brightness, excluding Aldebaran since I knew at the beginning that it does not part of the Hyades physically.  After that, I studied more in detail the differences in color of stars forming the cluster.  Thus, I note that the very great majority of the components of the cluster are white.  I note some exceptions however:  the duet Theta1 and Theta2, Delta1 Tau and Epsilon Tau raise a more yellowish colour.  The B-V indicator of Theta1, Delta1 and Epsilon are comparable (1,013, 0,983 and 0,952 respectively).  For Theta2, I was incorrect since this star has a B-V index of 0,179.  Oddly, Gamma Tau did not appear to me also yellowish, although its B-V index is very close to the values to Theta1, Delta1 and Epsilon, 0,981.  When that I studied the color of the stars of Mel 25, I was unaware of the B-V indices of these stars.
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