M51

M51 also known as the Whirlpool Galaxy comprises a large spiral and a smaller barred spiral.
The larger component also known as NGC5914 with the smaller component being known as NGC5195. The smaller component can take a red tinge in images as this is behind a dust lane from the larger component. The object was first described in detail by the Earl Rosse in 1845. The spiral arm pattern is classed as a text book orientation and points to a number of forces which are at work to stabalise the arm structure.

 

M51 is also home to a recent Supernova (SN2011dh) which erupted in May 2011. During this period M51 was not in an appropriate position in the sky for imaging from Ontario. This was the third nova to be reported in M51 the others being in 2005 and 1994.

 

Due to the supernova discoveries it is possible to accurately position M51 in the sky. Its distance is determined as 23Mly with an approximate size of 43,000 light years.

 

Locating M51 is always a challenge and something where non computerized go to telescopes which beginners generally use leads to frustration.  The map  shows the location and can act as a direction finder for M51 with it being markers in the centre of the image. The easiest method I have found to identify this is to start at Alkad at the end of Usar major. In my method i next try and find the pointer starts which are shown in the map a mag 4 and mag 6 pain which point to M51 they are seen directly below alkaid. M51 is not in the constellation Usar Major but in the constellation Canes Venatici.

 

The galaxy is visible in Binoculars under dark skies, but a telescope of about 6″ is needed to start to discern details in the galaxy. Large scopes >300mm will start to show the spiral arms and also the bridge between NGC5194 and NGC 5195. This is only something which i have seen a couple of times once in a 10″ newtonian at the Kelling Heath Star Party in the UK and once later in the year in the UK through a 10″ meade.

One issue with viewing M51 is that due to its great structure is is very commonly images and as a result our mind is simply tricked into seeing what we have seen on images before.