Category: Nebula

I’m slowly working my way through the pictures I took in Yorkshire. This one is of an object I spotted as a bright hazy patch while scanning the Milky Way through binoculars. A long exposure photo confirmed it as the Swan / Omega nebula. To my eyes it looks more like a swan than the uppercase Greek letter omega (?).

M17 is an object very similar to the Orion Nebula – an active star forming region. The cluster of young stars within it have yet to reveal themselves visually as they are largely obscured by dust within the nebula.  They can however be studied in infra-red where the dust absorbtion is much less. The bright bar of the nebula is about 20 light years long and the nebula is located in the Sagittarius arm of our Galaxy, 5900 light years away.

This image is comprised of 7 three minute exposures through the ZenithStar 70 at ISO1600  with an unmodified Canon 350D.

Dark nebulae are clouds of cold gas and dust which only reveal themselves by blocking out the light of  more distant stars. Consequently, most of them are to be found in the plane of the Milky Way where stars are most densely packed. The astronomer Edward Barnard catalogued many of them from photographic plates and they are now known by their ‘B’ number.

This image shows B142 & B143, just to the west of ? Aquilae or Tarazed.

As I wasn’t too sure of the exact position of the nebulae I positioned Tarazed at the left hand side of the field and took 11 3 minute exposures which were then combined for the final image. Telescope was the ZS70.

More formally known as NGC 6818, this planetary nebula in Sagittarius was dicovered in 1787 by William Herschel. Despite it’s relatively low visual magnitude of 9.3, because it is such a small object it can be photographed with quite short exposures and this image is a stack of 52 5 second frames on the club 20″. I used a Canon 350D at ISO800.

It has two distinct components; a spherical outer shell and a brighter core. Size is a diminutive 25″.

From the northerly latitudes of the UK, Sagittarius is low down on the Southern horizon during the summer months. Looking towards the centre of our galaxy this region hosts some of the most stunning star fields of the night sky and is also home to some bright nebulae. Two of these are captured in this wide field image; M8, the Lagoon nebula and M20, the Triffid nebula. Also in the frame is the open cluster M21.

Whilst these objects appear close together in the sky, M20 is a foreground object with M8 considerably further away along with M21. The apparent size of the long axis of M8 is about 1.5 moon widths and the object is rather larger than the Orion nebula (60 x 40 light years).

Being a bright naked eye object (under a dark sky) means that reasonable results can be obtained from relatively short exposures. This image consists of 18 minutes of luminance frames and 9 minutes each of red, green and blue.

Observatory:   Moorock, Australia

Telescope:       Takahashi STL-11000M

Camera:          SBIG STL-11000M

At the beginning of the holiday in Northumberland we had an evening where the cloud passed through just as the moon was setting. Having a restricted southern horizon I looked instead to the East where Cygnus was rising and decided to image the region around the bright star Sadr. Some puzzling over the hit or miss drifting I’d been getting with the AstroTrac lead me to the conclusion that I needed the polar scope on the left side of the mount to get good results. This has subsequently been confirmed by some recent posts on the Yahoo group and the problem is due to the scopes being manufactured with the tubes slightly misaligned. There is a mod available to correct this that involves fitting a collar with three grub screws around the tube. This will be worth a closer look.

Polar alignment was pretty close on this occasion so I took 16x 3 minute exposures with the ZS70 and unmodified Canon 350D and stacked the results.

The bright star to the left of centre is Sadr. There is an open cluster (NGC 6910) to the left of Sadr. The remainder of the image consists of HII emission nebulae that are catalogued in the DWB index. One Barnard catalogue object (B344) is visible just to the right of the bright orange star top centre of the image.

I got an email to say that Gyulbudagian’s nebula was brightening again so grabbed ten 3 minute exposures just before dawn on Monday. Taking advantage of the 7 hour time difference between the UK and New Mexico made this a much more reasonable 11am.

While it’s possible to distinguish the nebula as a small fan shape this is still a very faint object. The brightest star in this image is Magnitude 10.1 and some of the faintest, 19.4

The telescope used was GRAS-1, a Takahashi Mewlon 300mm with FLI IMG1024 Dream Machine camera. I’ve written before about this camera with it’s 24 micron pixels. It’s very sensitive, but this system suffers from pronounced vignetting which isn’t entirely compensated for by the flat frames when the images are stretched as much as this one.

Taking advantage of the fact that narrow band imaging is relatively unaffected by a full moon in the sky (and the 50% discount in telescope cost) I added another two 15 minute Ha exposures to my collection of the Horsehead. Then the pain-staking process of combining the individual frames to make a single pleasing colour image could begin.

All the frames were calibrated and aligned  in Maxim DL and the red, green and blue frames combined to make a single RGB image. A Digital Development Process stretch was then applied to all images and they were saved as 8-bit tiff images for further processing in Gimp (my favourite open source image processing software).

The bright star is Alnitak, the left hand star in Orion’s belt. The radiation from this star lights up a hydrogen gas cloud making it glow red and the Horsehead itself is a dark cloud of gas and dust silhouetted against the bright background. The Flame nebula (NGC 2024) is formed in a similar manner. Just below the Horsehead is NGC 2023, a bright reflection nebula. 1500 light years away, the Horsehead is some 3.5 light years in height (or 2×10¹³ miles high).

This is one of those areas of sky that will consume as much telescope time as time/money allow. A clear, moonless Australian sky enabled me to up the luminance frames to 30 minutes and also take a single 15 minute exposure through a hydrogen alpha filter.

Combining the luminance frames using SD Mask and a simple Digital Development stretch results in much lower noise than the original image post while keeping the star brightness under control. This was then aligned with the Ha image in Maxim DL, saved as a jpeg file and combined with the Ha image in Gimp.

The next step will be to add in the 15 minute exposures for each colour.

The constellation of Orion is home to many fine deep sky objects as well as M42 which featured in my last post. This one is IC-434, the Horsehead nebula. Probably the most photographed object in the sky it lies in the vicinity of the left star (Alnitak) in Orion’s belt (for northern hemisphere observers).

On the left hand side of the picture is the Flame nebula.

This is a work in progress and is a stack of the first four 5 minute exposures taken with GRAS-010, a  TEC 140 and SBIG STL-11000M camera with a luminance filter.

Global Rent A Scope run a free trial introduction on one of their Australian telescopes. One click imaging; all you have to do is select what you want to image from the list of visible objects and the system will select an exposure, convert the camera picture to jpeg and email it to you when it’s finished. The result from a single 2 minute exposure of M42 is pretty good on it’s own, but the system also files a copy of the original FITS image on the FTP server. This extends the possibility of stacking multiple images for a lower noise picture.

So, after taking 3  images in a row I downloaded them and opened them in Maxim DL. What was immediately clear was just how good a job the system does in automating the jpeg image production. It took me several hours work to get close to the system’s image. Here’s the finished result, the telescope is a Takahashi Sky-90 with an SBIG ST-2000 XMC camera.