Thursday, October 17, 2013

Snapshots and Mosaic of a Neighbor!

We were out recently taking a few pictures with my "little" 11cm William Optics refractor.  I've posted about it before, and this summer found a field-flattening corrector for it, so have been anxious to try it on the sky.  I underestimated the setup needed for the longer f-ratio of the F/7 refractor, and didn't have the guide scope needed to perfectly track such a long focal length.  So a critical test will have to wait.

Before it sank too low in the sky, I was hoping to catch the hydrogen cloud and star formation area Messier 8.  Since the predominant color is the h-alpha red, shown here is a single-exposure (!) with the venerable Canon 20Da, which has a little extended red sensitivity.  With the trailed images, it didn't seem worth a longer sequence to beat down the noise any more.  Shown is a 3 minute exposure at the highest ISO of the 20Da (1600).  With the F/7 lens, 4 minutes would have been better, but not until I've got a real guidescope.

Since the part of the Milky Way where M20 was located was setting fast, I moved over to something rising, and higher in the sky - our neighbor galaxy Messier 31 - the Andromeda Galaxy!  For some reason, the tracking seemed better in that part of the sky, so the exposures are less embarrassing.  Unfortunately, at 770mm focal length the entire galaxy is to big to fit in the field, so I ended up taking 3 frames to push the extent of the coverage.  Each frame consisted of three 3-minute exposures, so the total investment was less than 30 minutes with my other camera, the Canon XSi.  The 3 frames were then assembled into the shown mosaic with Microsoft ICE (Image Composite Editor - FREE - see this post!), which did a great job of combining them.  The result then had levels adjusted a bit (perhaps too much!) in Photoshop.  It could certainly take more exposure, but is not bad for a half-hour's investment!  Of course, the majority of the stars shown are in our own galaxy, a few hundred to a few thousand light years away, then there is a big jump of 2.5 million light years to the Andromeda Galaxy (Messier 31) and its two companions, the smaller M32 above and larger (but fainter) M110 below.  I tell people at my night programs at Kitt Peak that we'll have a much better view of it when it collides with our galaxy in about 10 billion years!

So the jury is still out on if this new corrector was worth the hassle of getting it (the only one I could find was in Europe and was an adventure in ordering it!).  But the William Optics scope is a nice one to use for daytime use and it is nice to have it available as a tool for night time use as well!

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