Wednesday, 29 April 2020

M13 and M102 - A fine pair

M13 and M102 - A fine pair

Finally, I have got to the end of the glut of data I have acquired over the recent weeks.  Also, this will be the final instalment of the recent glut of astronomy blogs, for I have eventually caught up with all things Astro blogging on my list.  Yippee I hear you cry!  For this post, I look at two targets I imaged around a week ago.  In a break from galaxies, I look at M13, a globular cluster before moving onto M102.  A galaxy with a dubious past.
No matter what time of season it is (as in, right now, we call this time of year Galaxy Season because of the number of galaxies that can be observed and imaged with relative ease) I always keep an eye on what's next coming over the horizon.  It won't be long before we lose astronomical darkness overnight, which will mean imaging time of any use will be taken from us in the weeks either side of the Summer solstice.  So, over the next couple of months, while darkness is at a premium, we will say goodbye to Leo, Virgo and the likes, but hello to the Summer constellations of Lyra, Cygnus and Hercules amongst others.  In fact, these constellations are already putting in an appearance after midnight as they creep up above the Eastern horizon.  Hercules is the first of these to put in an appearance, rising high enough to observe and image slightly before midnight, and it is here that I looked for my next imaging target.

M13 - The Great Globular Cluster in Hercules

A favourite at star parties for observers new and old, M13 is a magnificent site in any telescope or suitable binoculars.  It's brightness and location make it easy to spot.  But, I have found that imaging this target raises it's own difficulties.  Being made of nothing but countless stars mean that focus is everything.  When we observe M13, rather than just being satisfied that we've seen a condensed blob of stars, we spend time at the eyepiece to try to visually resolve those stars.  Only then I find can we gain a true appreciation of this cluster.  The same goes for taking a picture of it.  Slightly out of focus, and you could tell what the image is of, but instead of being able to resolve as many stars as possible in the globular core of the cluster, you could end up with a blurred white spot with a few speckles of other stars around it.  However, accomplishing a good focus is harder that it sounds, especially when having to rely on manual focusing without the aid of an auto focuser adjusting itself throughout the imaging session, keeping everything as optimum as possible.
I first tried this target before I had a dedicated astronomy camera, instead using my DSLR and though back then I was happy just to get any result, I have since changed to a refractor telescope which makes focussing much better.
Can you spot at least one other galaxy in the image?

M13 in Hercules is a wonderous site at high magnification when observed through a telescope.

M102 in Draco

M102, or should that be NGC 5866?  If you take a look at the Wikipedia page for this galaxy, you will be referred to several other galaxies, including M101.  To get a partial understanding of why we have confusion, we need to have a very quick history lesson...
The targets we observe and image all have designations, or names given to them.  Targets starting with the letter M were first catalogued by Charles Messier as he went about searching the skies for comets in the 18th century.  When he identified a target, but determined it wasn't a comet, he described it, gave it a catalogue number and a position and then left it at that.  The point being that he knew if he came across this object again in the future, that he had already observed it, and therefor could just get on with the rest of his observations.
Then, along come another astronomer, Pierre Machain, who used to share observation information with Charles Messier, but he determined M102 to actually be a duplication of M101 and therefor, you could say not to exist.  Though limited because of the quality of the equipment of the day, the confusion for sets in because visually, they are very different targets.  Though both galaxies, M101 is a face on spiral galaxy, and the supposed M102 is an edge on galaxy.  It has also been suggested that M102 is actually a duplicate of one of several other galaxies listed in the NGC (New General Catalogue).  Over the years, other astronomers and professional bodies have had their own interpretation of what M102 actually was when it was first catalogued, but it's now come to be generally accepted that it was indeed different to M101, and is more likely to be what is now catalogued also as NGC 5866.
Whichever way you look at it, and whatever name you wish to give it, it provides a good challenge to image.  On images using a longer focal length which allow you to get much higher magnification, you can see the galaxy edge on, but also make out a thin dark line running through the edge of the galaxy.  While I could just about make out this line early on, unfortunately during the processing stages, I seem to have lost this detail while trying brighten the galaxy overall.

The wider field view of the galaxy.
The image below is an enlarged crop from the original hi-res image in which you can just about make out the notable feature of this galaxy.  It's still quite tricky to spot though...

Finally from me, thanks for sticking with me through this recent splurge of Astro posts.  I have finally come to the end of my backlog.  Hurrah!  There are a couple of opportunities to get outside observing and imaging again in the coming few days, but the weather has generally deteriorated somewhat compared to recent weeks.  It's back to snatching half chances to get out under dark skies when I can.  For the moment though, thanks for reading, and stay safe 😊.

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