Thursday, May 18, 2017

Messier 61 /NGC 4303

Messier 61 is a barred galaxy , part of the Virgo  Cluster.
To find M 61 we may start at Porrima /Gamma Virginis , itself a beautiful double star worth of close examination.
From Porrima we should navigate toward West to the next naked eyes bright star Zaniah or Eta Vir.
From Zaniah we should change course toward North to 16 Virginis a fifth magnitude star.
Once we get there ,we are close to Messier 61.

Insert a low power ocular , let say of  25mm focal length and look for the star asterism adnotated below as ''a-b1-b2-c-d1-d2''.
Choose the star raw at East , namely b1-c-d1.
Follow the direction from ''a'' to ''d1''.
Go twice this distance further North and you will find a pair of stars.
The brighter is bearing the code HIP 60224 and it have a dimmer star to the North-East.
Imagine a right angle triangle having the right angle corner in the dimmer star.
At about twice the distance between HIP 60224 and the ''corner star'' , toward East-South East it lie Messier 61.

The above screen-print from Aladin Lite is not rendering well  the brightness difference between HIP 60224 of  8.15 mv  and the ''corner star'' which at 10.35 mv  is much dimmer ,with more than two magnitudes.
The magnitudes quoted above are from Stellarium.

Stellarium is rendering better this brightness difference between the two ''guide stars''.
But of course ,the galaxy looked much , much fainter in the Revelation 9 mm Plossl ocular ,at 96x in my 125mm F/7 Dobsonian.
My first observation of M61 happened on May 14 and the second last night ,on May 17.
I saw just a dim ,hazy ,round patch of light , a very ,very dim one.
No structure , no shape , no central condensation.
For all this I will have to come back latter ,with a bigger telescope.
But I'm happy and grateful I was blessed with the view of this galaxy considered as big as our Milky Way and located at 53 million light-years.

Note :
The screen-prints are made from Aladin Lite and Stellarium and the notes were added with Paint.

No comments:

Post a Comment