Andrew’s Astronomy Blog

Reviewing one of the folders of images that I took in La Palma I came across this one that I’d stacked, mis-labelled and forgotton about. Once I started to look at it a little closer I realised that the stars were very misshapen with ones at the bottom of the frame appearing as small eclipsed disks. Vignettting was also very pronounced and uneven. Checking the focal length revealed it was taken with the Canon 18-55mm kit lens. I really must replace this lens at the first opportunity!

This is a severely cropped version of the image, showing the area from the clusters M6 & M7 at the right to M20 & M21 at the left.

10 90 second frames at ISO 800 with the Canon 350D.

Last night yielded a couple of clear spells without a moon in the sky, (the first for a while) and with the nights drawing in rather earlier as we approach autumn I made the most of the opportunity for a final run through of equipment and techniques before the Kelling Heath star party.

It was just as well that I did because I discovered that my T adapter for the Canon had worked loose and needed a tweak with a screwdriver. The weather has been so bad this summer that I’ve barely had the telescope out since the La Palma trip.

M52 is an easy target to find and with the Zenithstar, if you’ve got it in the middle of the frame then you’ll also capture the Bubble nebula as well. After a short interlude waiting for cloud to clear, I took 5 3 minute exposures at ISO 800 with the unmodified Canon 350D.

The Rosette nebula is a large cloud of ionised hydrogen gas in the direction of the constellation Monoceros. Distance estimates vary but it’s probably 5000 light years distant with an overall diameter of 130 light years. The nebula has the Caldwell number 49 and the cluster of stars at the centre is separately listed as Caldwell 50 (also NGC 2044).

While the central cluster is visible under dark skies with binoculars the nebula is very difficult to see visually as it’s about 1 degree in diameter with a very low surface brightness. The red colour is also not visible. Relatively short CCD images however, show what a spectacular object this is.

Telescope: GRAS-14 - Takahashi FSQ-106ED

Camera: SBIG STL-11000M-ABG

You know autumn has arrived when the 7 stars of the Pleiades cluster are rising during the evening. On a recent trip out into the countryside researching a dark sky site I took this picture with the Canon 350D on the Astrotrac. Exposures are 120 seconds at ISO 800 and there are 12 individual frames.

This group of young stars was born out of a cloud of hydrogen only about 100 millions years ago.  The blue glow around the brightest stars is a reflection from the dust cloud that they’re currently travelling through. The cloud has been sculpted by the inter-stellar magnetic fields around the stars. At a distance of around 425 light years, they’re the closest of the Messier objects.

Fellow club member Malcolm has also just posted an image of M45 as well: M45 Revisited

I’ve just got back from a week’s holiday in the North Yorkshire Moors. We were staying at a cottage at Low Garth in Fryup Dale. 3 nights were clear up until about midnight on each night and I took a fair few photographs and as I process them I’ll post them here.

The night sky quality in the Moors is very good as there are no major towns nearby and Teeside was conveniently hidden by the side of the valley we were located in. The only time you were really aware of it was passing clouds reflecting an orange glow.

Equipment was the Astrotrac  with Canon 350D and either the ZenithStar 70 or Canon kit 18-55 zoom. I did have a repeat of the issues with the Manfrotto 410 head working loose, I think it’s the other axis this time, so it’ll be back for repair and I need to think about an alternative. While expensive, the Astrotrac TW3100 wedge looks very nice!

While I’m processing some of the images here’s some fun I had with an asterism between Sagitta and Cygnus. CR399, otherwise known as ‘The Coathanger’ is an easy binocular object in Vulpecula. 5x 30 second exposures at ISO 1600 through the ZenithStar 70mm refractor. As usual, click on the image for a larger view.

Discovered by Mechain on the 27th March 1781, M103 became the last entry in Messier’s original catalog. Interstellar extinction of about 1.5 magnitudes makes determining the precise distance difficult but it probably lies about 7200 light years away. The cluster diameter is 17 light years and the bright star in the field is Delta Cassiopeia.

This was the first time that I’d tried out a new piece of software, DSLR_Logger from the AstroTrac Yahoo group. It’s main purpose is for determining precise polar alignment of the mount. I will write more about this program when I’ve had a chance to explore it rather more fully.

This was also the first outing for my new Williams Optics Field Flattener 3 on the 70mm.

Searching through some old folders on my PC I came across 5 images of the Pleiades that I hadn’t previously processed. Taken on the Astrotrac with a 75-300mm Canon zoom lens set at 200mm, each is 3 minutes long for a total of 15 minutes exposure.

The resulting stack had masses of red sky noise but removing this and applying a non-linear stretch starts to show the dust cloud around the brightest stars of the cluster.

Got back from my first Spring star party on Sunday afternoon having arrived Friday evening. The event was wonderfully cloud free with a lack of aircraft contrails as well; something to do with a volcano in Iceland!

While the skies were clear there was more sky glow than I remember from the autumn event. On the first night there was a lot of moisture in the air with dew dripping off every surface pretty much from nightfall but on the second  this didn’t start being a problem until after 2am, by which time I was thinking about bed.

On Friday I had problems getting the AstroTrac to track at all well but this had resolved itself by Saturday and I concentrated on Mars in M44 and M13 in Hercules. 24x 2 minute exposures at ISO400 through the ZenithStar 70.

M13 to follow.

This being a Bank holiday weekend, and the skies being cloudy I’ve had some time to review the DVD presentations from the 2009 Mid West Astro Imaging Conference that I bought from Astro Photo Insight some time ago. Two were of particular interest; “The Hows and Why of Image Calibration” by Kevin Nelson of QSI and “Choosing a camera for astrophotography” by Craig Stark. After watching these I decided to evaluate some flats produced by pointing the telescope with Canon 350D at a blank illuminated laptop screen (I used an empty Notepad window). Analysing these images in Maxim, the results were nothing like I expected; less an even grey frame, more a technicolour nightmare!

After that shock I went back to look at my images of the Double cluster and reprocessed them with the new flat frames. Compared to my original efforts there’s much more colour evident in the stars and the overall blueish tint is much reduced. How much of the improvement is down to the flat frames and how much to improved technique is up for debate.  That’s all part of the fun; there’s always something new to learn!

Having bought the book ‘The Caldwell Objects - and how to observe them’ it’s only fitting that I identify this object with it’s Caldwell number rather than the rather nondescript NGC 4755. Located in Crux, The Southern Cross, at a declination of -60 degrees this is a Southern Skies cluster only.

Also known as The Jewel Box this compact cluster is just 10′ in size and could be mistaken for a 4th magnitude star with the naked eye. 5,000 light years away , the stars in it are about 15 million years old.

This image is comprised of 28 3 minute LRGB exposures (12,6,6,4).