Orion Nebula tagged posts

The Orion Nebula (M42) Redux

Since my first session imaging the Orion Nebula back on January 28th was out of focus, I decided to learn more about how to focus my CCD camera.  I wrote about my experience learning how to focus in an article entitled, The Importance of Focusing When Imaging Deep Sky Objects.

As I read up on the topic and got more helpful hints from my mentor, Michael Caligiuri, I gave imaging M42 another shot tonight.  Again, I set out to capture 24, 5 minute exposures of the magnificent Orion Nebula but my guidescope came out of alignment and I ended up with 8 salvageable images, which I then processed into the image you see below.  I am much happier with this latest image of M42 as it seems to be in focus, which reveals much more detail than the image I took a couple days ago.

Orion Nebula (M42)

Orion Nebula (M42)

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The Importance of Focusing When Imaging Deep Sky Objects

Focusing a telescope is not a trivial task to be overlooked when imaging deep sky objects (DSO).  There are many factors that go into focusing, especially when you do not have an eyepiece and you have to rely on a computer screen to determine if what you are trying to image is in focus or not.  Most photos of DSO’s take a couple hours to image and it is pretty disappointing to process out of focus images after you have spent a lot of time capturing them.  Relying on your own eyes would seem to be a good solution but your sense of sight can fool you into thinking that an object is in focus when it is completely out of focus.  This is where looking at Histograms and Full-Width Half Maximum (FWHM) comes in.  In the Astrophotography program, MaxIm DL 5, there is a focusing tool that gives you a readout of of the object’s brightness and plots the brightness on a histogram, like the one in the image below.

Ideally, if image is in focus, the histogram should have a sharp peak and the FWHM should be less than 2.  Not knowing this handy piece of information when I first imaged the Orion Nebula on January 29, 2013, I was left with exposures that were out of focus.  Thanks to clear skies tonight, I was able to re-image the Orion Nebula to see if I could get a better focus, which you can see the comparison photos below.

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Imaging the Orion Nebula (M42)

The Orion is a constellation that can be seen between November and February and is one of the most recognizable groups of stars that can be viewed in the Winter sky.  Since the beginning of Winter, I have watched the constellation rise as the sun sets and last night, I finally got to take my first image of the Great Orion Nebula.  Known as M42, the Orion Nebula is the closest region of massive star formation to Earth and is about 24 light years across and is a stellar nursery, where new stars are being born.

Takahashi Sky90 II, Orion 80mm Guide Scope, Celestron CG-5 Mount and MaximDL 5 (on the computer)

Takahashi Sky90 II, Orion 80mm Guide Scope, Celestron CG-5 Mount and MaximDL 5 (on the computer)

I went out in my backyard around 6:30pm, which is earlier than I usually go out.  The night was clear so I calibrated my mount and set everything up for a 2 hour imaging session.  One of the first things I did before setting the image sequence was to set my mount guiding so the telescope and camera move with the rotation of the stars.  After that was set, I focused the camera.  Since the CCD camera is attached to the telescope, I need to take a series of continuous images in order to verify that the nebula was in focus.  Here is an example of what that image looks like:

Orion Nebula Focus output from Maxim DL

Orion Nebula Focus output from Maxim DL

Once I was happy with the focus, I then set the MaximDL program to take a series of 24, 5 minute exposures using the Hydrogen Alpha (Ha) filter.  I took this image with the Ha filter due to the presence of mostly hydrogen gas...

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