Archive for September, 2007

 I’ve been a little quiet on the astro-imaging front this last week as I have had an unexpected electronics repair job to carry out!Another hobby area of mine involves photography, but at the other extreme end of the spectrum to astrophotography.  Whereas many of my deep-sky images take in excess of 12 hours exposure time, this other hobby involves exposure times of around 25 microseconds or 1/40,000 second. 

It is high-speed flash photography.

Some 25 years ago I built the first highly portable high-power high-speed flashguns for my brother who is into nature photography, mostly birds and insects in flight.  I developed these units for the following 20 years and they are the only ones of their type on the planet – no commercial manufacturers make anything like them.

Recently my brother (who lives in Surfers Paradise, Australia) sold his set of guns to a U.K. professional photographer (who shall remain nameless) and he promptly managed to turn the 3 units into completely non-functioning boxes.  He did quite a number on them as it took me around 2 days to fix each unit, but now they’re all up and running again.

You can see some images taken with these units on my High Speed Flash pages over at AOL.   As you will see, I am currently talking to a manufacturer who would like to build market and sell these flashguns.   I shall be talking to these guys again next week and hope we can come to some arrangement.

It’s very strange, but for over 20 years no commercial manufacturer has been interested in making these units for the public, but recently the enquiries have been coming in thick and fast from people wanting to buy high-speed flash [HSF].  I think it’s the coming of the digital camera age that has swung things around.

So, if you are interested in this other branch of photography, keep an eye on my HSF site to remain up to date with the latest developments.

On the astro-imaging front I am writing some posts about the equipment I currently use and Noel and I are still preparing images – I hope to have something for you soon 🙂

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It’s been a bit quiet lately but, at last, a new image 🙂

You’ve heard of 4 weddings and a funeral – well this is 5 clusters and a nebula! 

This is the M103 region in Cassiopeia, and it is very rich in open star clusters as you can see. 

The bright star at bottom right is Ruchbah, one of the main stars that form the “W” of Cassiopeia.  The open cluster immediately to the left is M103, in the 11 O’Clock direction from M103 is little Trumpler 1.  In the 10 O’Clock direction from Trumpler 1 we have NGC654.  Drop down below NGC654 to find NGC663. 

Finally, in the 5 O’Clock direction from NGC663 we find NGC659.   But that’s not the lot in this very active frame.  Look towards the top right hand corner and you will see the red glow of a faint emission nebula – this is SH2-187.

All this in a single Sky 90/SXVF-M25C frame of 3.33 by 2.22 degrees.   This image was taken on the night of Tuesday 11th September 2007, and is composed of 43 sub-exposures at 4 minutes per sub, giving a total exposure time of 172 minutes or 8 minutes short of 3 hours.

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In a few of my posts about imaging you will see me mention “narrowband data” and words like “OIII” and “H-alpha”.  Well, this is to do with narrowband light filters and line emission sources of light [as opposed to broadband emitters].  For example from the Veil Nebula Project:

The last RGB image of the Veil nebula has been significantly improved by adding some H-alpha and some OIII narrowband data as can be seen in the accompanying image.

And from the IOM September 2007 post on M31:

Deep exposures of M31 will show up lots of very nice little HII regions in the arms.  You can “boost” the appearance of these regions by adding some H-alpha data to your RGB data.  Take around 4 hours or so of deep [20 minute sub-exposures] H-alpha and incorporate into your RGB data using the techniques discussed by either Steve Cannistra or Rob Gendler [see the blogroll links]

So what types of narrowband filters are there?  The main [line emission] filters used in narrowband imaging are:

  • OIII – Doubly ionised Oxygen
  • H-alpha (or HII) – Singly ionised Hydrogen
  • H-beta – Another Hydrogen line
  • SII – Singly ionised Sulphur

These filters differ from each other by the wavelength of light that the particular filter will let through.

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Have you ever had the problem where the time indicated on one of your clocks (including your computer’s clock) is different to another one?  Well, I have and it can certainly cause headaches when trying to analyse the large amounts of data that we generate from our images. 

I now have one of those “radio-controlled” clocks that gives me the precise time via an atomic clock in the UK.  The clock broadcast signal is controlled and monitored by the National Physics Laboratory in Teddington and the transmitter was moved to Anthorn in 2003 – although everyone still refers to the atomic clock as “The Rugby Transmitter”.

So now the observatory computer is always giving me the correct time for the FITS data files and other astronomical programs that I might be running as I always “synch” it to my local atomic clock before each imaging session.

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As I am located in the New Forest, you can imagine that for some months of the year, particularly from late September until late November, condensation is a major problem in the dome. 

I have always used a product called “Water Eaters” from Lakeland Plastics [I prefer the name “Water Snake” but I guess the marketing people at Lakeland didn’t] around the gap where the dome rotates.  This product is basically a sausage-shaped piece of fabric filled with some water absorbing substance [possibly silica-gel]. 

I always place these in the gap around the dome edge [on the inside of the dome] after an imaging session and they keep the ingress of water vapour right down.  Unfortunately, on their own they are still not enough! 

I had a problem with the Hyperstar a couple of years back where halos started appearing around bright stars after about half an hour or so of imaging.  At first I thought this was atmospheric water vapour.  After quite a bit of investigation I found out it was actually water vapour in the Hyperstar itself – not good! 

I got rid of the trapped water vapour by placing the Hyperstar in an oven at 40C for about an hour, but I clearly needed to also do something about protecting the observatory. 

To this end I bought a dehumidifier which now runs full-time in the dome.  I typically need to empty the water container every three days [roughly a gallon I suspect] throughout the year. 

I also have a thermostatically controlled greenhouse heater in the dome which is used to keep the dome temperature a few degrees above freezing during the winter months.

So far, these precautions seem to be working – I’ll find out this coming winter  🙂

Have you had similar problems?  If so, how have you deal with them.  Drop me a line and let me know.

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The last RGB image of the Veil nebula has been significantly improved by adding some H-alpha and some OIII narrowband data as can be seen in the accompanying image. 

However, the project has turned into an even bigger undertaking. 

I decided that I needed to get the nebulosity south of this region, so I embarked on a full two-frame Sky 90/M25C mosaic to capture the whole of the Veil complex.  I now only need the RGB data of the southern region (H-alpha and OIII already taken) in order to have an extremely deep and detailed image of the whole of the Veil.

The statistics make frightening reading.  So far I have taken 142 sub-exposures amounting to 27 hours total imaging time and a 1.7 GB file size.  The addition of the final RGB data is likely to take this project to over 30 hours total imaging time with a file size in excess of 2 GB. 

I am not sure I will undertake such a mammoth task again without the aid of the mini-WASP array!

The original image is on the left and the improved images (with H-alpha and OIII narrowband data) is on the right:

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The Steve O'Meara's Herschel 400 Observing GuideThe Herschel 400 is a list of 400 objects catalogued by the eighteenth century astronomers Caroline and William Herschel.

I put Caroline’s name first here because apparently she made a couple of new discoveries, that were not on Messier’s list, and this prompted William to start his own in-depth search for new “nebulae”.  Working together the search produced over 2,500 objects of which the most impressive 400 were chosen to create the Herschel 400 catalogue.  If you have exhausted the Messier and Caldwell catalogues, then the Herschel 400 may well be next on your list.

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Deep-Sky Wonders (Stargazing)Deep-Sky Wonders has been created by adapting the work of Walter Scott Houston from his Sky & Telescope articles over the years.  Unfortunately for us “Scotty” [as he was affectionately known] is no longer with us, the book was edited by Stephen James O’Meara who also works at Sky & Telescope.

Each chapter of the book covers a single month and includes descriptions [in beautiful prose] of a number of objects that, during the month, will be seen particularly well.  At the end of the each chapter is a very handy summary table that makes refering to the objects simplicity.  There is also an excellent Bibliography and Index.

But of course, there is a lot more to this superb book than just the chapters for each month.  “Scotty” really knew his way around the heavens and you will find, within these pages, objects you had not heard of before – I guarantee it.  Even if you consider yourself well-versed in the Heavens, I am sure that in Deep-Sky Wonders you will find new objects to view or photograph.

I would like to relate to you the “gem” I found in this book.   I wanted to image the Deep-Sky object nearest Polaris, and I asked on several astronomy forums “what Deep-Sky object lies nearest to Polaris?”  Now, not many people image near Polaris, so I didn’t get any useful answers back beyond what I already knew.  

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The beginning of September might be considered a touch early [Walter Scott Houston in his “Deep-Sky Wonders considers it a November object] for M31, but the nights’ are now drawing in quickly, and you will be able to get a good long time on this object if you start now. Read the rest of this entry »

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