(IAAC) Obj: Castor, Alpha Gemini - Inst: Vixen 102M


Observer: Luis Arg|elles
Your skills: Intermediate (some years)
Date/time of observation: 05/06/98, 20:30 UT
Location of site: near Oviedo, Spain (Lat 43, Elev 250m)
Site classification: Rural
Sky darkness: 2.5 <Limiting magnitude>
Seeing: 4 <1-10 Seeing Scale (10 best)>
Moon presence: Major - gibbous or near object
Instrument: Vixen 102M
Magnification: 25x, 100x, 200x
Object(s): Castor, Alpha Gemini
Category: Multiple star.
Constellation: Gemini
Data: mag 2  size 
Position: RA :  DEC :
I start to observe Castor with the 40mm Plvssl eyepiece. Keeping in mind
that the Moon is having a phase of 0.8 and there is some fog in the sky
the sky is not black, but light-gray thorough the scope at this
magnification), is remarkable that the third component, Castor C is
perfectly visible at magnitude ~ 9.5

Putting the 10mm Eudiascopic eyepiece reveals a clean split at 100x, but
the image becomes really gorgeous when using the 5mm Eudiascopic. Due to
the small pupil-exit diameter this eyepiece gives, the background is now
black and I can observe the 3 components all in a row. Components A and
B shows beautiful Airy disks surrounded by a first diffraction ring,
with well defined black-sky between them.

What makes the image unforgettable is the strong white of the brighter
components. In fact they seem to shrink and curve the sky near them.
Component A is clearly brighter than comonent B.

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