Category: Deep Sky

The Triangulum Galaxy

Most of the GRAS telescopes have monochrome cameras so I haven’t done much with the one shot colour cameras. However, when I was looking for a telescope / camera combination for imaging M33 I realised that GRAS-003 (a Takahashi TOA-150 with an FLI 8300) fitted the bill exactly with the galaxy filling the frame.

Five 10 minute exposures later and this is the result:

M33 has a very low surface brightness due to the fact that it’s light is spread out over a large area. This makes it a difficult visual target but it responds well to long exposure photography.

While visible to the naked eye (given a low enough level of light pollution) no pre-telescope notes are made of it; you’d be unlikely to notice it unless you already knew it was there. It was catalogued by Messier in 1764 and was one of the first ‘Spiral nebulae’ observed by Lord Rosse.

At a distance of 2.8 million light years it is 50,000 light years across and contains around 30 – 40 billion stars.

Deep Sky Nebula

M27 – The Dumbell Nebula

Tuesday night was pretty clear so after taking the pictures of Albireo on the club’s 20″ reflector I switched to M27. The 20? has some problems with tracking and field rotation as it’s on a motorised Dobsonian mount so it’s best to use a high ISO setting on the camera and keep the exposures as short as possible. I took 30x 20 second exposures at ISO 1600 and 15 were usable although there’s some elongation visible in the final image.

M27 is a planetary nebula, recorded by Messier in July 1764. It lies about 1000 light years away in the constellation Vulpecula.

Deep Sky

Coloured stars

Ask any person in the street what colour stars are and you will usually get the answer; White. However, a closer study with the naked eye will reveal some differences in colour and with binoculars or a small telescope this is more apparent. Some double stars show a marked colour difference between the pair and this is apparent in this example, Albireo, the star marking the head of the swan in the constellation Cygnus.

Deep Sky Galaxy

NGC 247

Once you get past the members of the Local Group, the next nearest galaxies are in the Sculptor cluster. Back in November last year I posted an image of NGC 253 and this time it’s the turn of NGC 247 in the constellation of Cetus.

At a distance of about 12 million light years this is a rather distorted spiral galaxy, with a prominent star at one end and a sparce void at the other. Being relatively close, the galaxies in this group appear quite large, this one is about 2/3 of the diameter of the full moon in length but is too faint to be visible to the naked eye. The small galaxy in the lower right of the image is PGC002795 (ESO540-026).

This is a picture taken with GRAS-006 in Australia and consists of 3 five minute exposures. GRAS-006 is an RCOS 16? – FL 3654mm @ f/9.0 with an SBIG STL-1001E NABG camera.

Deep Sky Galaxy

The Pavo Triple

Many people are familiar with the Leo Triplet of galaxies, M65, M66 and NGC 3628. In the Southern skies there’s a similar formation in the constellation Pavo of NGCs 6769, 6970 & 6971 at a distance of 190 million light years. All three galaxies are interacting and whilst the cores consist of elderly reddish stars the spiral arms are lit up with clumps of new stars formed by the gravitation interactions.

Many other members of the Pavo galaxy group are also visible in this picture.

This image was obtained with GRAS-008 and is a composite of 10x 5 minute exposures. The image has ben scaled down by a factor of 3 for display on this blog.

Deep Sky Nebula

M57 – The Ring Nebula

I’ve imaged this object before using the Canon 350D in some very early experiments with imaging the night sky. This is the result of narrow band imaging using Ha, OIII & SII filters (3 ten minute exposures of each) with all three summed to produce a luminance frame. The telescope used was GRAS-2.

These images were taken with the moon in the sky as telescope time is much cheaper when this is the case and narrow band images are much less sensitive to the light from the moon.

This image is in false colour with Ha depicted in green, OIII in blue and SII in red. What is clear is that there is very little emission at the SII wavelength as there is very little red colour in the nebula. There is a central star in the nebula however, as it doesn’t emit light at the wavelengths used in this image it doesn’t appear in the picture.

OIII is an oxygen molecule in an ionised state that can only exist in very rarified gas clouds. It was first noticed during spectroscopic analysis of emission nebulae in the mid 19th century and mis-identified as a new element called Nebulium. It wasn’t until the 1920s that physicists correctly deduced it’s true form.

Deep Sky Nebula

Gyulbubaghian’s Nebula

Gyulbubaghian’s Nebula (pronounced gyool-boo-DAH-ghee-an) is a Herbig-Haro object (HH215) – a variable bipolar nebula generated by the shock waves from the variable star PV Cephei. As a reflection nebula it does not emit light of it’s own but is illuminated by the nearby star. It has also been observed to fluctuate rapidly in brightness.

A request from the Deep Sky section of the BAA alerted me to the possibility that this object was currently very faint and I decided to image it using the GRAS-1 telescope to confirm this.

The result is shown here, the nebula is marked by the intersection of the two lines. The image is in negative form as this makes the nebula easier to see. Five 180 second exposures with a photometric V filter reveals that it is very faint at the moment but large, rapid fluctuations in brightness have been reported before so I shall return to this in the near future.

For my next attempt I will try and use more exposures to reduce the noise level in the picture. As usual, clicking on the image will show the full size version.

Deep Sky Globular Cluster

M13 – The Great Globular

M13 is found in the constellation Hercules. Consisting of probably a million stars at a distance of 21,000 light years it is easily discernable in binoculars. First noted by Halley in 1714: “This is but a little Patch, but it shews it self to the naked Eye, when the Sky is serene and the Moon absent”.

Messier added it to his catalog in 1764. Messier noted: “In the night of June 1 to 2, 1764, I have discovered a nebula in the girdle of Hercules, of which I am sure it doesn’t contain any star; having examined it with a Newtonian telescope of four feet and a half [FL], which magnified 60 times, it is round, beautiful & brilliant, the center brighter than the borders”.

Determination of it’s true nature had to wait until the Herschels examined it with their improved telescopes of the 1780s. May 16, 1787. 20 feet telescope. “The 13th of the Connoiss. [M 13 = NGC 6205] is a most beautiful cluster of stars. It is exceedingly compressed in the middle and very rich. The most compressed part of it is round and is about 2 or 2 1/2? in diameter, the scattered stars which belong to it extend to 8 or 9? in diameter, but are irregular.”

The image is a stack of eight 2 minute exposures at ISO 1600 with a Canon 350D and 0.63 FL reducer on the club Celestron 9.25″.

Deep Sky Galaxy

The Draco Triplet

The constellation Draco is well placed, high in the sky at this time of year and contains some little known objects including this group of galaxies, NGC 5985, NGC 5982 & NGC 5981 (from left to right in the image).

NGC 5985 is classified as a barred spiral, 5982 an elliptical and 5981 is an edge on barred spiral. All three are about 100 million light years away and the field of view in this image is 23.6 arc minutes square.

I’ve had these images on my PC since the beginning of April while I tried to resolve an issue with calibrating them. Thanks to Arnie at GRAS, this is now solved and was due to a buggy camera driver not subtracting the camera pedestal value from each pixel.

Telescope is GRAS-1 with an FLI 1024 DM camera and this image is composed of eight 3 minute exposures.

Deep Sky Solar System

The Moon, Mercury and the Pleiades

Post author By admin
Post date April 29, 2009
No Comments on The Moon, Mercury and the Pleiades

Sunday evening was bright and clear just after sunset so I went out to take some pictures of a rather pretty crescent moon. Unexpectedly, the picture also showed up the planet Mercury between the moon and the horizon and closer inspection revealed the star cluster M45 nearby as well.

The picture was taken on a Canon 350D and is a 2.5 second exposure at f/5 and ISO 1600. Focal length is 205mm. Long exposure noise reduction was done on the camera.