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(IAAC) Obj: M4 - Inst: 102 mm f/9.8 and 70mm f/6.8 Achromatic refractors. 11" SCT
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Observer: Luis Arguelles
Your skills: Intermediate (some years)
Date/time of observation: July,15,1998 - 21:55 UT
Location of site: Santander - Spain (Lat , Elev )
Site classification: Suburban
Sky darkness: 4.5 <Limiting magnitude>
Seeing: 6 <1-10 Seeing Scale (10 best)>
Moon presence: None - moon not in sky
Instrument: 102 mm f/9.8 and 70mm f/6.8 Achromatic refractors. 11" SCT
Magnification: 25x, 50x, 100x
Filter(s):
Object(s): M4
Category: Globular cluster.
Class:
Constellation: Sco
Data: mag 5.9 size 26.3'
Position: RA : DEC :
Description:
Locating M4 is really easy. You only need to locate Antares and then move a
bit towards West. At 25x the strong light background from the horizont renders
it as a weak milky object. Moving up to 50x the background appears a bit
darker but the observation of this cluster doesn't improve.
I think I observe some granulation in this object, but I can't resolve it
with so much light in the background.
Using a 70mm refractor with the same observing conditions I can observe it
using averted vision only. Using an 11" SCT telescope the image is better,
but not a lot better than the image offered by the refractor. In fact, under
this observing conditions, the SCT wastes its efforts gathering a lot of
background light.
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Optional related URLs: http://members.tripod.net/~whuyss
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