Messier Objects - M25

Sagittarius is full of amazing sights with the naked eye, binoculars and a telescope.  If you live in an urban setting it is best to use optical aid.  There are plenty of star clusters located throughout the heart of our Milky Way galaxy.  One such cluster is known as Messier 25.  It has no special name associated with it but it is quite beautiful.  As with all objects within this constellation the best time to view them is during the Summer.

Messier 25 is an open cluster located in the northwestern region of Sagittarius.  It can be found a mere 6.5° away from the Sagittarius Star Cloud, M24.  It is approximately 19 light years across and it located 2000 light years from Earth.  As viewed from Earth it appears as 32' in diameter; the approximate width of the Full Moon.  It is possible to see it with the naked eye as its apparent magnitude is 4.6.  However, it would be difficult to see from an urban or suburban setting due to light pollution.  

Observation Information

I first located this Messier Object late in the evening of July 8, 2018.  After I had observed M24 I slew my telescope eastward approximately two fields of view.  I noticed three brighter stars above the cluster that seemed to encompass the deep sky object.  I found this object using my 14" reflector telescope with a 41mm (68° FOV) Televue Panoptic eyepiece.  This produced a true field of view of 1.69 degrees.  The tight part of the cluster seemed to take up 40% of the field which works out to an estimate of 41'.  There seemed to be a lot of stars outside of the main cluster.  This is likely due to the rich nature of the Sagittarian region.

The weather information at this time is listed in the table below.

Characteristic	Value
Temperature	24°C
Humidity	39%
Wind	N 6 km/h
Barometer	101.91 kPa
Sky	Passing Clouds

The observation record for M25 is found below.

M25 Observing Record

Additional Information

This cluster was discovered before the time of Messier in 1745 by the Swiss astronomer Jean-Philippe Loys de Chéseaux.  He originally commented: "Another one between the bow and the head of Sagittarius".  Nearly twenty years later Charles Messier recorded this object in his famous catalogue.  Messier noted that the stars of the cluster were seen with some difficulty with an ordinary telescope.  He also noted that it contained no nebulosity.

It is interesting to note that this cluster does not have an NGC number associated with it.  It does however have an Index Catalogue number which means it was included in the major update to the NGC.

If you are ever searching the realms of Sagittarius be sure to seek out M25.