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.

Our old friend the Bubble Nebula in Cassiopeia again, this time on the society’s 20″ with the ATIK 383L camera.

By the time I was imaging this, it was almost at the zenith with all the issues that brings when using the Alt/Az dobsonian. Can anyone say ‘field rotation’?

This image is a stack of 30 second LRGB frames. Luminance are binned 2×2 and the colours 4×4.

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.

Looking back on our time in La Palma it seems that the time passed all too quickly. Certainly, I would have liked to have spent more time doing LRGB imaging on the 40cm. However, this type of photography consumes time at an impressive rate and there were a lot of other things that we needed to do. This image of M17 is comprised of single 10 minute exposures with red, green, blue and luminance filters, the colours being binned 2×2.

With the days getting longer, and the nights corresponding shorter, opportunities for imaging get fewer. Friday night at the observatory looked promising though and once it started to get dark Dan and I had a crack at M57 using his modified Canon 1000D. More on that later. By this time, Cygnus was getting higher in the eastern sky so we moved onto NGC 6888, an emission nebula.

With viable guide stars on top of the nebula, and with it ideally placed for the Alt-Az 20″ (low in the east) we settled on 1 minute exposures at ISO 1600. A few were rejected due to bad tracking but overall the results were very good. The tracking excursions were limited to the Alt axis which we’ve seen before. The usual fix if it’s problematic is to add or remove nose weight but on this occasion it only affected a few frames.

One of the advantages of using a small telescope for photography is that you can get wide fields of view that help put objects within their true context. The two main objects in this picture are M97, the Owl nebula and M108. Originally I planned to use a cropped version of this picture but after some consideration I decided that the wider field was the better presentation.

M97 is the intra-galactic object at only 4140 light years distance. Despite it’s diminutive size  (only 170″), it is still about 3 light years across. First observed by Mechain in 1781 Messier added it to his catalogue in march of that year.

M108 is rather further away at 46 million light years and is a member of the Ursa Major group of galaxies. The bright object near the centre is not the galaxy core but a foreground star in our own galaxy. While this galaxy was observed by Messier at the same time as M97 it was not added to his catalogue at the time and is a 20th century addition.

19 3 minute sub frames, ISO 800

Canon 350D

Zenithstar 70

Skywatcher field flattener

Always a favourite target for winter imaging, it’s hard to be disappointed with the results. With the first clear night in a long time I was keen to try out my new 10-20mm Sigma zoom. The field size with this lens is immense and this is a crop of just the Orion area from a stack of 10 3 minute exposures at f/4.

The Sunday night was also clear so I setup the 70mm on the Astrotrac. I didn’t spend quite long enough on the polar alignment so some trailing was visible even with fairly short exposures. To avoid clipping the trapezium I reduced the exposures to 2 minutes and reduced the ISO to 400.

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

Staying with the Ha filter due to the full moon, I took 4 15 minute exposures of the Seagull Nebula in a 2 frame mosaic. This picture covers almost 4 degrees by 4 degrees in an area close to the borders of Canis Major,  Monoceros and Puppis.

GRAS-12 - Takahashi FSQ-106ED

SBIG STL-11000M-ABG

This is one that’s featured in previous images of mine but this time it’s in close up courtesy of GRAS-6, an RCOS 16″ Ritchey-Chrétien Cassegrain with a focal length of over 3.5 metres. With a full moon in the sky I used an Ha filter on the camera and binned the pixels 2×2 to reduce the sub-frame exposure length to a manageable 5 minutes. This image is a stack of 6 exposures.

Set against the bright emission nebula IC434, the Horsehead is a cloud of cold, dark gas in the constellation of Orion.