(IAAC) Obj: M31, Globular & Open Clusters in M31 - Inst: 15 inch Obsession f4,5

[anonymous at sedna.atmob.org]

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Observation Poster: Armin Hermann <burmeseinn at yahoo.com>

Observer: Armin Hermann
Your skills: Advanced (many years)
Date/time of observation: 16 Nov 2004
Location of site: Sangkhlaburi, Thailand (Lat 15°N, Elev 200m)
Site classification: Exurban
Sky darkness: 5,5 <Limiting magnitude>
Seeing: 10 <1-10 Seeing Scale (10 best)>
Moon presence: None - moon not in sky
Instrument: 15 inch Obsession f4,5
Magnification: 131 & 342x
Filter(s): none
Object(s): M31, Globular & Open Clusters in M31
Category: External galaxy.
Class: 
Constellation: And
Data: mag various  size various
Position: RA :  DEC :
Description:
On 16/17 11 04 I took the chance of perfect seeing and fairly good visibility 
to hunt for extragalactic globular clusters and open clusters in M31. As 
reference I did use a picture of M31 in the Night Sky Observer’s Guide. 43 
GCs, OCs and stellar Associations are plotted on that map. The visual 
brightness of the objects I took from the Internet. 

On earlier occasions I did experience that perfect seeing is much more 
important to possible resolution of faint stars and almost stellar objects than 
very clear skies with medium to bad seeing. Seeing last night was better than 
1” and naked eye limit approx 5,5mag. M31 was very high in the sky (~60+°
during my observations).

In order to describe the level of difficulty for observing single objects, I 
created a 5-level scale: (1) direct vision, easy, (2) direct vision, difficult, 
averted vision very easy, (3) averted vision only but fairly easy (4) averted 
vision only, difficult, (5) averted vision only and temporarily, extremely 
difficult.

All observations were done with my 15” f4,5 Obsession scope with 5mm 
Nagler T6 eyepiece (342x magnification). To locate the area of the objects I 
did use the Nagler 13mm (131x).

G64:  (5), 00 40,5 +41 22 02,3, V 15,1  extremely faint and stellar. Seen with 
AV (averted vision) only.

G72:  (5), 00 40 52,8 +41 18 54,2, V 15,0  just like G64, stellar and extremely 
faint. AV only.

G73:  (2), 00 40,9 +41 41 15, V 15,0  just non-stellar, very faint but directly 
seen.

G76:  (1), 00 41,1 +40 36 3,6, V 14,2  very easy, directly visible as a stellar 
object. With AV it turns into a non-stellar smudge. Bright.

G87:  (5), 00 41 14,7 +40 55 52, V 15,6  most difficult of all objects seen. I 
could glimpse it only 4,5 times in 10 minutes. I could not confirm whether G87 
was stellar or non-stellar. 

G119: (4-5), 00 41,9 +40 47 2,7, V 15,0  stellar, very difficult with averted 
vision (AV).

G156: (5), 00 42 25,3 +40 57 18, V 15,6  stellar and very faint with AV.

G213: (3), 00 43,2 +41 07 2,5, V 14,7  non stellar smudge without core, fairly 
easy with AV.

G226: (4), 00 43 30,3 +41 38 56, V 15,5  non-stellar smudge with averted 
vision, on the edge of visibility.

G244: (5), 00 43,8 +41 37 2,6, V 15,4  pops up only temporarily with averted 
vision, extremely faint, stellar.

G252: (3), (?) features a stellar core and a halo that was seen with averted 
vision. Fairly easy.

G279: (5), 00 44,5 +41 29 2,9, V 15,4  extremely faint smudge with no central 
brightening or stellar core. ~3”. AV only.

G280: (1), 00 44,5 +41 22 2,5, V 14,2  easy, stellar, could be seen directly.

C107: (3-4), 00 40,5 +40 36, 4-5” size. No distinct core. Biggest of all 
observed objects. AV only, not too difficult.

C202: (4), 00 42,1 +40 57, stellar and difficult with AV.

C410: (5), 00 44,4 +41 21, extremely faint 3-4” smudge of light. AV only. 
Barely visible.

It should be noted that the observed size of objects described as “non-stellar” 
or as “smudge” was never more than approx 2-3”. It is almost impossible to tell 
the size when an object is so extremely faint and visible only with averted 
vision. Therefore a simple description as “non-stellar” is all that can be 
determined.
I was amazed who far I could push my 15 inch scope to the limit under last 
night’s conditions.


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