Archive for August, 2013

200mm Canon EF lens with Canon 5D MkII on a Paramount – no overkill there then 🙂

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Here are the ones you missed from earlier on – the First and Second Light images from the amazing Canon EF 200mm prime lens.

Initially I went for the Double Cluster and Stock 2 region:

And then I spent a bit more time on a very wide field of the M31 region.  I composited the 200mm data with some earlier Sky 90/M25C data for this image to give more colour in M31.

 

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I have not been able to post images to this site for a while as an “upgrade” completely screwed things up for me.  Fortunately Dave Parker was able to unravel the damage caused by me upgrading one of the plug-ins and we should now be back in business.

Half a full Moon up last night and cloud rolled in fairly early on – but I managed to get some work done with the incredible Canon EF 200mm prime lens.  I focused up on the Ruchbah region and then moved on to image Kemble’s Cascade.  Not much colour in the stars as there was always the thin high cloud and the Moon to contend with.  What did amaze me with this shot was the galaxy towards the top of the frame.  That is IC342, an object I meant to image years ago, and I never realised that this is where it sat in the sky.  These massive wide-field shots are also educational in seeing where things lie in the sky 🙂

 

Before taking the Kemble’s Cascade image, which was only 9 x 3-minute subs at ISO 500 under very non-ideal conditions, I set up focus on the Ruchbah region.  This image is just a single 3-minute sub at ISO 500 – I am amazed at the low noise quality of the image from an uncooled camera!!

 

 

The Kemble’s Cascade image is not quite what I was looking for 🙁  The image I want for this region is a mini-WASP 4-framer, so I will just have to bite the bullet and get on with it at some point.  The Ruchbah image on the other hand is quite amazing for such a short exposure time.  The 200mm lens will allow me to capture the WHOLE of Cassiopeia in just 3 frames!!  With such short exposures giving pretty reasonable results, this is a project that I should be able to complete in a single evening.  Be sure to watch this space.

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I recently bought a Canon 200mm prime lens to go onto the 5D MkII for some very wide field work.  Last night was completely clear so that was first light, and second light, for the lens.

Firstly I went for the Double Cluster and Stock 2 region.  ISO 800, 3-minute subs (6 off) f#4 and an IDAS filter.  This is the result of that exercise.  I then moved on to M31 and used 5-minute subs (10 off) at ISO 400, again f#4 and an IDAS filter.  I managed to get this shot.  Finally I composited some old M31 data with this data to add a bit of colour to M31 and got this.

I am totally gobsmacked at getting perfectly round stars corner to corner across such a huge field of view.  My colour isn’t too good at the moment as I need to work out a new processing schedule with the DSLR, but the results are amazing.  I have plenty of new targets lined up for this little beauty 🙂

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Still no Moon and still plenty of cloud – you just can’t win.  Got a nice shot of the 4-minute ISS pass around 11:06 p.m. which you can see here.  Also managed to get 4 meteors, but the images are not very good for reasons I’m about to give.

This Perseid session has shown me how to take meteor images with a DSLR.  I have read bits and pieces on the web, but they weren’t really all that helpful, and some were downright contradictory.  So here’s my take on it.

Although meteors look pretty impressive to the naked eye, they simply don’t kick out all that much light, and the ones that look faint to the eye are REALLY faint to the camera.  The first and most important thing you need to do is go to your nearest dark site to minimise the skyglow.  As it was cloudy this year I didn’t bother to take the kit over the forest but just worked from the light polluted back garden – this is the main reason my results were rubbish.  You MUST have a good dark sky background.  Why?  Because you are going to use an exposure time of a few seconds at high ISO and all through this exposure time you will be integrating up the skyglow.  If you capture a meteor right at the beginning of opening up the shutter the skyglow will build up as the exposure progresses and the meteor will appear to get dimmer and dimmer, faint ones simply won’t show up at all.  So we already have a conflict problem here.  You would like to have a longish exposure time of say 30-seconds or so in order that you’re not firing the camera off like a machine gun, but long exposures will build up the background skyglow.  A short exposure stands a good chance of missing a meteor event as the meteor will always come along in the interval between shots.  I recommend using an exposure time of about 10-seconds with an interval between shots of one second – my intervalometer doesn’t work with an interval of zero seconds, if yours does, great.  Now you come to what lens?  I use a 15mm Canon fish-eye lens wide open at f#2.8.  Whatever lens you use you need it wide open to grab as much light as you can.  Short focal length means bigger field of view, so you grab more of the sky per shot.  The reason I really like the Canon 15mm fish-eye is because when I have the focus ring fully anticlockwise it is automatically focused at infinity and I can start shooting.  None of my other lenses are this considerate and I have to waste time using the Live View facility to focus up on a star before taking pictures.  What ISO?  Probably best for a bit of experimentation here – try starting off with ISO 1600 and go from there.  With a short focal length lens and a short exposure time there’s no need for fancy AstroTracs or other mounts to track the stars, a plain tripod will do fine.  Also, you can stack all your images together for a nice time-lapse video of the night sky which might be a worthwhile exercise if you don’t manage to get any meteors.  Happy Hunting!!

 

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Well this year was unusual in that we are not annoyed by a blazing Moon upsetting our view of the Perseids – so what else can be thrown at us?  Clouds of course.  Pretty heavy cloud for most of last night into this morning 🙁  However, when the cloud decided to shift itself there were plenty of faint meteor trails to be seen, and I managed to catch one blazer around midnight.  It is right at the bottom of the frame in this image – only just managed to catch it.  Reason the path is so curved is because this was caught using a 15mm fish-eye lens and we are right on the edge of the frame.  Actually heard the “whoosh” as this one went over.

About half an hour earlier there was an ISS pass that I had forgotten was going to happen, around 11:44 p.m.  Luckily the camera was pointing in the right place to catch this very short 2-minute pass – unfortunately a plane on its way to Bournemouth decided to photo-bomb me.  The reason for the little gap in the ISS path is due to the 2-second delay I had set between frames on the Canon 5D MkII that was taking the images.  A good evening’s worth of viewing and imaging despite the cloud – hoping the weather Gods will be a bit kinder tonight.

I just managed to stitch together 3 consecutive frames of the plane/ISS pass which you can see here.

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Flitting through a planetarium program I stumbled upon a nice bright Carbon star in Corona Borealis.  Designated SAO 84015 at magnitude 6 this should look really great!  So a couple of nights ago I fired up the mini-WASP to grab this one, 5-minute subs, all 3 cameras.  First sub came down and – nothing.  No bright star near the centre of the field of view at all.  Strange.  Never mind, I just left the mini-WASP running as I have done this sort of thing before where I’ve been a little off in pointing the scope.  Next day I process the data – and – still nothing.  Open up the planetarium program and compare with my image – I find SAO 84015 on my image and it is sitting there at about magnitude 14??  So now we start to go deeper.

A bit more investigating shows that SAO 84015 is much more well known as R Coronae Borealis (even I have heard of that before) which shows odd “inverse nova” behaviour.  I knew that it often dimmed from mag 6 to mag 14 but after a few weeks or at most months at minimum it would slowly climb back up to mag 6 again.  Could I have been plain unlucky and caught it at its minimum?  Start digging again.

Looks like R Coronae Borealis took a dive around 2006 – surely it hasn’t been at minimum all this time has it?  It has never shown that behaviour before.  Contacted a few star experts and – yes – that’s exactly what’s happened.  R Coronae Borealis took a dive all those years ago and is still languishing down at mag 12 – 14 with no immediate signs of recovery, how weird.

So now I’m playing a waiting game, waiting to see if and when R Coronae Borealis once again blazes away at mag 6.  If I can get another image with the star at maximum this will make a really interesting image pair – what a huge contrast in star brightness!!

 

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A recent update seems to have screwed up my ability to post any new images to the New Forest Observatory – which to put it mildly is a pain.  Dave Parker is working to sort this totally unnecessary hassle out.

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My 50th Earth Science Picture of the Day (EPOD) was posted today 🙂 🙂

Many thanks Jim for sticking with me and my various oddball pictures.

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For this DSS2 image of the Tulip nebula region in Cygnus I just kept adding frames until the computer gave up 🙂

 

 

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