Monthly Archives September 2013

Looking Beyond the Gas and Dust in the Pelican Nebula

Pelican Nebula (IC 5070)

Pelican Nebula (IC 5070)

It is pretty amazing the detail you can pull out of Nebula using small focal length telescopes.  I love the small focal length for the wide, sweeping shots of the gas and dust in space but they are not great for getting in really close for those detailed close ups of the massive pillars and plumes these stellar nurseries produce.  In learning more about the Pelican Nebula, I read that it has a particularly active mix of star formation and evolving gas clouds. The light from young energetic stars is slowly transforming cold gas to hot and causing an ionization front gradually to advance outward. Particularly dense filaments of cold gas are seen to still remain, and among these are found two jets emitted from the Herbig–Haro object.

Herbig–Haro objects (HH) are small patches of nebulosity associated with newly born stars, and are formed when narrow jets of gas ejected by young stars collide with clouds of gas and dust nearby at speeds of several hundred kilometres per second. Herbig–Haro objects are ubiquitous in star-forming regions, and one is visible in the Pelican Nebula image that I captured (or is it?)  Thanks to tools like Photoshop, which can be used to bring out the full detail of these objects, I was able to capture an infant star that has not yet ignited.  You can just make out the jets of gas and dust at the top of the dark pillar in the middle of the image below, which was isolated and cropped from the larger image above...

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Using AstroTortilla to Plate Solve Objects

AstroTortilla

I recently downloaded a plate solving program called AstroTortilla, which is a program that corrects GoTo alignment and centers objects you are trying to shoot.  Before using this program, my GoTo alignment would vary from night to night and if I am shooting the same object, I would have to crop out a portion of the object since the mount did not slew exactly to the position I had the night before.  After I successfully installed and set up the program, thanks to this amazing tutorial, I tried it out on the Pelican Nebula (IC 5070).  After plate solving the nebula, it was a clear night so I decided to image for a couple hours until the clouds rolled in.  Under the full moon, I can only image through the Hydrogen Alpha (Ha) filter so I went out the next night and collected more data on the Pelican Nebula.  The AstroTortilla program performed flawlessly each night.  As you can see in the image below, the only cropping will have to do to this image is due to drift, which is an insignificant amount of image loss.

The black border around the image represents the amount of cropping that is needed due to drift

The black border on the right of the image represents the amount of cropping needed due to drift

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Narrowband Imaging, Processing Tools and Techniques

ElephantTRunkNebulaSliderSince getting an SBIG ST-10XME and a CFW10 with Narrowband (Ha, SII, and OIII) filters, I could not wait to image an emission nebula.  I received the new goodies on August 9th, and of course, the conditions were not right to image until August 20th.  I had first light with the ST-10XME under a bright full moon so I could only shoot through Hydrogen Alpha filter.  Ten days later on August 30th, I was able to shoot with all 3 filters so I chose the Elephant’s Trunk Nebula (IC 1396) as my target.

Narrowband Imaging

Learning how to image through Narrowband filters was not as difficult as I imagined.  Here are some things I learned along the way:

  • Since these types of filters only let in certain wavelengths of light, one of the main differences was the exposure time.  I typically take 5 minute subs but I had to increase the time to 10 minutes to get a decent looking sub with lots of detail.  Your experience may vary and will depend on the focal length of your telescope and imaging equipment
  • I still focus my telescope manually so focusing follows the same routine of looking at the stars Full Half Width Maximum (FHWM) to see if you are in focus.  I focus with the Ha filter in a 3×3 bin, with a 1 second continuous exposure
  • I have collected data a couple of different ways.  When the moon is in the sky, I will collect Ha data.  If the Moon is not present, I will collect all 3 types of data (Ha, SII, and OIII)
  • With Narrowband imaging, it is all about data data data...
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