Sunday, March 9, 2014

Auriga’s Open clusters, review

Auriga or Charioteer is a northern constellation because of it’s 1st to 3rd magnitude stars it makes it easy to trace and remember in the sky. Auriga’s stars make a pentagon like shape by borrowing the star Alnath (β tau) from his neighbor Taurus.
Capella (α Aur), the brightest star in the constellation, is a multiple star system which components are two yellow giant stars of spectral type G. 

For my sketching and normal observation, I have decided to use the H. A. Rey constellation shapes, which for Auriga seems like the profile of a face with a big nose and a big triangle hat.

Under LP skies, Auriga hides 3 extraordinary jewels of majestic beauty that can be discovered through either binoculars or telescope.

In truth, they all looked very similar in the bino-view so much so, that once when I spotted M36 in the telescope I could not recognize it and I thought it was M38. On the other hand, M37 looked just slightly different than the other two, because no one star could be resolved with the binoculars and therefore it looked mostly like a nebulous object.

All three open clusters were discovered by Giovanni Batista Hodierna before 1654 and they are at a distance of about 4 thousand light years from us. M37 is the brightest of the 3 (apparent magnitude of 5.60) and it looked like that through the binoculars.

Now, let’s talk about the three sketches I made individually. From top to bottom in the Binocular sketch, they are M37, M36 and M38.

My first thought about this wonderful open cluster, was that it was M38 because I could not recognize any of them with the inverted view. Even though I could not recognize it, I sketched it and then noticed that it was M36.

The night of the observation had no moon, the sky was clear and I evaluated the seeing as 6/10 because of the light pollution.

I could resolve around 5 or 6 stars in this cluster with the binoculars, but with the 10mm eyepiece I resolved more than 25.

I also realized that the brightest stars in the cluster showed a view that made me remember the view of M45 -The Pleiades-. After some research, I found that these bright stars show the same glow effect that the bright type B members of M45. 

Most of the unresolved “blurry” stars in M36 were glowing in patches distributed throughout the cluster and they looked like a kind of nebulosity.

After I finished sketching M36, I moved the telescope a little bit to my right side and I found M37. It looked like a fuzzy nebulous patch either in the binoculars or the 20mm erecting eyepiece which provided a magnification of 32.5X.
I tested the 10mm eyepiece which provided a magnification of 60X and some stars could just be resolved with direct vision while a few others required averted vision. As with the effect seen in M36, the unresolved stars formed glowing patches inside some areas of the cluster, with the difference that in M37, that glow effect is brighter, perhaps because the stars inside the cluster are more condensed.

Information I found about this cluster said that this is the brightest cluster and the richest in stars of the three.

In previous historical observations  I found on the internet also reported a kind of nebulosity inside the cluster and even more, some of them reported just the nebulosity but no stars resolved. Personally, just based on my observation I would say that there was some nebulosity inside the cluster and that some stars were really hard to resolve as they glowed enough to be detected but perhaps they were too together to perceive them as individually stars.

Finally, here is the 3rd cluster: M38. This was the first sketch I made of the three but the last to be digitalized. The previous sketches were made digitally in Photoshop based from a raw sketch, but this one was processed from the pencil sketch. That’s why the stars here look bigger and brighter, but in truth, dim and bright stars in each cluster, showed with similar characteristics.
Despite looking the dimmest and the poorest in stars M38 was nice to contemplate with either binoculars or telescope. The same “glow” effect of M36 seemed to be inside M38. In the sketch, instead of drawing the glowing patches as nebulous clouds, I tried to reproduce that view by drawing very little faint stars inside the cluster.

Obviously, I think a dark sky would improve the view of these 3 jewels by comparing the background with the glowing areas of unresolved stars, but certainly it would be necessary to have a bigger magnification to resolve more stars and even more in M38. My last attempt to resolve the stars in M38 was kind of painful for my eyes.

Please enjoy this triplet of open clusters, marvelous creation of God.



Edited by Jennifer Steinberg  (editor in chief)


1 comment:

  1. Beautiful field captures! Thank you for sharing. :)