Wednesday, 30 November 2016

The First Bite Of Winter

The First Bite Of Winter

In recent days, high pressure has built up over the UK, and with it, cold clear air has been dragged from continental Europe giving big swathes of the country a couple of nights at least, of clear cold weather.
What to do?  With a busy week lined up in work, Monday was the best chance for me to get out the SBT and go observing.  As not to get frustrated with the wonderful insecurity light of the neighbour, I loaded the SBT into the car, took the car to work which allowed for a clean get away at the end of the day.  I headed out to a reasonably dark sight a few miles out of town and arrived just as the last glimpses of daylight were disappearing over the horizon.
With the SBT deployed, alignment and collimation tasks completed, it was just a question of deciding what to go searching for.  It was to become a very successful night of observing.
I spent a bit of time to start off just looking around the sky, allowing my eyes to become accustom to the darkness around me.  This can take up to half an hour, so it gives you some time to decide.  On the back pages of my notebook, I keep a list of targets that I want to observe.  Kind of a miniature tick-list if you like,  It's a list I compiled a couple of years ago and has targets in different constellations visible throughout the northern hemisphere.  The idea being that there was always something to go for.  It was from this list that most of the session took its lead.

M34 - NGC 1039 - Perseus

An easy and relatively bright target to start,  At magnitude 5.2, it was beautifully bright with pin point stars set against a good dark sky.  The target is just inside the constellation boundary of Perseus, but also quite close to the popular targets in Andromeda.  Observing this open cluster showed me that the seeing conditions were very good indeed,  The image at the eyepiece was steady and clean.  Not much sign of twinkling came from any of main component stars in the cluster.  A nice object to start, an easy one to find, but it was time to move on to something that I hadn't observed before.

C47 - NGC 6934 - Delphinus

The constellation of Delphinus is usually observed toward the end of Summer.  It can be found to the side of Cygnus, almost immediately overhead during the late Summer months.  Though we are now knocking on the door of Winter, early in the evening, Delphinus is still high up in the sky and ideal for spending a bit of time on.  The main component star of Delphinus are all around magnitude 4, so reasonably bright.  However, depending on your source of information,  C47 is a magnitude 10.6 object, or 8.8 so can take a bit of finding.  Using the stars of Delphinus as a place to start, the SBT picked up this globular cluster with reasonable ease.  Using the 25mm eyepiece, the cluster was quite small, showing as little more the a pea sized smudge.  I couldn't resolve any individual stars, but I was still pleased.

C37 - NGC 6885 - Vulpecula

Time to skirt around Cygnus to the western section of the Milky Way.  Vulpecula isn't a particularly well known constellation unless you're into astronomy.  C37 is another open cluster which called for a change of eyepiece to the 32mm 2 inch optic.  This is an interesting cluster to observe because it is made up of I would say, 2 distinct magnitude groups of stars.  Around 5 of the brightest starts looked to be around magnitude 5, but the more I looked at the cluster, I could see that they were nestled in amongst a larger group of perhaps 20 to 30 magnitude 8 stars.  The whole cluster fitted into the field of view very well indeed.  It was a great new tick to add to the notebook.

C16 - NGC 7243 - Lacerta

The fourth target of the evening, the fourth constellation and the fourth cluster!  Lacerta takes its place tucked into the side of the Milky Way.  This can mean picking out targets in this region is tricky.  Not necessarily because they are small or not very bright, but because there are lots of background stars to navigate around to find it.  C16 is quite a bright target at around magnitude 6.2, but it looked to be surrounded by stars of quite similar magnitude, probably 7 to 8th mag.  This was the toughest find of the evening so far, and again, another new tick for the evening.

NGC 7160 - Cepheus

Directly across the Milky way from Lacerta, Cepheus kind of sits half in and half out of the Milky Way.  This really is a small open cluster,  I counted around 6 stars which formed the main part of the cluster.  After some searching, the only way I could verify what I had found was indeed 7160 was by checking for some images on my phone.  It's a gem of a small cluster.  Again, quite bright at around mag 6.1 in the most part.  It really did take a fair bit of searching to find this one.
With a normal push to dobsonian scope, making fine adjustments can be a bit tricky, so when looking for a target, it is quite easy to go wildly off piste as it were,  Especially if you nudge the telescope accidentally.  It was while trying to hone in on 7160 that I came across a feature that I haven't been able to identify as yet,  The feature was a well defined arch of stars, reasonably equally placed, and all of similar magnitudes.  Unfortunately, I had now way of knowing exactly what I had come across and haven't been able to see anything in the vicinity that matched what I saw.  One for the future maybe!

NGC 6871 - Cygnus

Cygnus is one of my favourite constellations, sitting smack in the middle of the Milky Way with a plethora of different things to look at within its boundaries,  However, this open cluster didn't exactly live up to the reputation of other targets.  In fact, it earned just a one liner in the notebook!
Bright against the Milky Way.  Not many stars make up this average cluster.

NGC 1502 - Camelopardalis

The constellation of Camelopardalis can be found quite close to the familiar "W" shape of Cassiopeia.  It's quite a large constellation made up of only a handful of stars.  1502 is an open cluster found at the end of a string of stars called Kembel's Cascade.  This is a feature that I hope to photograph at some point.  The cluster itself is quite small, but bright at mag 6.9.  It's very well defined and I observed 2 or 3 brighter magnitude star nestled in amongst a dozen or so higher magnitude stars.  I think the cluster will set well in a photograph at the end of the cascade.  So, another tick for the book.

Also Observed During The Session

This brought at an end to the main observing session, although whilst sitting back and taking stock of what I did actually see during the session, it occurred to me that I had also re-visited many other more familiar targets whilst hopping from one observation to another,
  • M1 - The Crab Nebula
  • M45 Pleidies
  • M27 Dumbbell Nebula
  • C14/NGC 869 & NGC 884 - Double Cluster in Cassiopeia
  • M31, M32, M110 - The Andromeda triplet of galaxies.
  • M57 - The Ring Nebula
  • Venus, briefly and very low in the sky at the start of the session.
This was an excellent session, and well worth the effort of getting out of town to somewhere with few distractions.  If this is a snapshot of what this winter is going to bring, it's going to be a cracking season!  Thanks for reading.


Friday, 18 November 2016

Waiting For The Weather

M101 - Getting from RAW to the final picture.

One thing that dabbling with astrophotography gives you, is something to do if the weather for observing is rubbish.  These last few weeks, the weather has been typically autumnal with little chance for getting the scope out at all.  Then, we had the over-hyped (thanks to the wonderful UK media) 'Supermoon'.  In essence, a normal full moon at closest perigee for a while.  But, realistically, it looked just the same as any other full moon.  And, as full moons do, it was too bright to really make any effort towards getting ready for any observing.
So, I've taken the opportunity to apply a couple of new things that I learned in my recent trip to Astrofarm about image processing.  The more I study imaging, and the techniques used to enhance the data I collect with the camera, slowly but surely, I'm beginning to make small improvements.
I went back to re-look at some data I collected back at the beginning of August.  I took a series of images of M101, a spiral galaxy called the Pinwheel Galaxy in Ursa Major.  At the time, I was stacking images in Deep Sky Stacker, where I would do some basic levels adjustments before then processing the image further in GIMP2.
My first attempt at stacking produced an image was, to be frank, a disappointment.  In fact, I don't have my original attempt at stacking because it was so poor, I just deleted it.  But, somewhere over the last few years, I've heard someone say, never delete your source data.  You never know when you might want it.  Source data can take a minimum of a whole evening to collect.  Sometimes, people can spend weeks or months collecting it even, so just deleting it is a big decision.  A lot of work potentially gone with the push of a button.
This time, I used 30 x 60 second frames at ISO 800 plus 10 Dark frames, 10 BIAS frames and 10 FLATS.  In a brief session on image processing with Andrew at Astrofarm, he showed me briefly what he does to start the image processing procedure.  So, once I completed the stacking process, this time, I did not do any further processing in Deep Sky Stacker.  I just saved the image as a tiff file.  I've installed Adobe Photoshop CS2 as recommended, and have been using this to do any post stacking processing instead of GIMP2.  There are plenty of tutorials on using CS2 on the web, so I've been checking some of those out too, and adding some of those techniques to the ones that Andrew showed me.
I couldn't tell you everything I've done along the way to get the latest image.  A lot of it is trial and error.  But, I guess the main purpose of this blog post was to demonstrate the difference between a single starting frame taken outside with the camera and scope, and, with stacking and processing, what you could possibly expect to achieve with fairly limited knowledge and understanding such as mine.  
The following picture is a single frame taken on M101.  I have cropped it so it is similar in orientation to the second image.  Notice in the first image. there are few stars visible in the frame at all.  Plus, you can only make out feint detail of the galaxy itself in the centre of the picture.

  
This second image is the result of the stacking and processing steps I took.  Using some basic principles of adjusting the curves and levels in CS2, I've been able to bring more of the image out and make using of the hidden data.  The processing steps have also revealed more stars in the field of view, and has allowed the core of the galaxy to stand out just enough.  It's definitely not the brightest of images compared to some that you can find with a quick google search, but I'm pleased with it, which I guess is the most important thing.


Thanks for reading!