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Money Shot: Saturn

Saturn is definitely one of my favorite telescopic targets.  It is a tough one to image in detail, though.  It is currently 8.825 AU away (or 1.31 billion kilometers, for those who prefer metric) and that means that the planet itself (not the rings) subtends an angle of only 19 arcminutes (0.32 degrees).  Even at 308X magnification (which is what my telescope (1540mm focal length) plus my Neximage webcam (5mm focal length) give, that's still an awfully small image.  Also consider that 300X magnification is getting quite close to both the theoretical limits of my 127mm telescope, and to the best that can be expected from the Earth's turbulent atmosphere.

 

That's why the nice image isn't a thumbnail -- that's "actual size" in terms of pixels on my webcam.

This image is the best I was able to tease out of 30 minutes of imaging.  I learned a valuable lesson: a webcam's "automatic" imaging settings are very poorly suited to small, dim objects on a very black background.

You can clearly see the shadow of the rings on the planet, and the shadow of the planet on the rings.  You can also pick out a hint of a cloud band in the lower hemisphere.  The Encke gap between the rings is not visible.  It is small enough that it exceeds the resolution of my telescope.  Larger amateur instruments (twice the diameter) can resolve it.

Image taken on April 9, 2006 between 10:00pm and 10:30pm EDT.  127mm f/12.1 telescope with a 5mm focal length Neximage webcam.  Processing in Registax.

The Moon, Overexposed

It was a clear night tonight, and the Moon was well positioned for photography.  Have a look at what I accomplished.  Click the images to make them big.

	This is  Mare Crisium, which is approximately 640km on each side.  Above, and to the right, is Mare Tranquilitatis, which is much larger.  The Apollo 11 landing site is not visible in this image.  The overexposed area is the crater Fredholm and its surroundings.  This image is not oriented.
	The right side of this image is not the edge of the moon, but the terminator.  It separates lunar night from lunar day.  The prominent crater with the central mountain is Gassendi, which is about 114 km across.  Gassendi A and Gassendi B are the two craters that are immediately north of it.  Mare Humorum is to the south, and Oceanus Procellarum to the north.  The heavily eroded crater Letronne is also visible.  The northern wall of this crater was destroyed when the lava flow that created Oceanus Procellarum overran it.  This image is oriented with south to the top (a common convention, as most telescopes invert the image).
	This image shows a substantial part of Mare Imbrium.  The "bay" toward the bottom is Sinus Iridum, which is approximately 411 km across.  The crater on its rim is Bianchini.  The three prominent craters near the bay are, from top to bottom, Mairan, Sharp, and Harpalus.  The two larger craters on the Mare in the upper half of the image are, from top to bottom, Diophantus and Delisle.  The crater at the extreme right is Aristarchus.  In between Aristarchus and Diophantus, you can see the eroded crater Prinz.  It also had one wall covered with lava when this Mare formed.  This image is oriented with south roughly to the top.

All identification of features was done using Virtual Moon Atlas 3.0 Expert by Legrand and Chevalley.  It's a cool piece of software that's worth checking out.

All images were taken on the night of April 9, 2006 between 9:00pm and 10:00pm EDT using a Celestron Neximage webcam.  Processing was done using Registax.

My First Real Astrophoto

I have been studying detectors and image processing in my course lately, and it inspired me to try out an interesting area of amateur astronomy: webcam imaging.  The basic idea is to use an inexpensive webcam to take a video of an object, and to then process only the "good" frames from the cheap camera into a quality image.  I picked up a Celestron NexImage camera to try this out.

Today was the first day I could see the moon at all since I purchased it.  I got in a solid three minutes of observing before the clouds rolled completely over it and began to threaten rain.  This meant that I didn't spend any time playing with the settings of the camera.  In particular, I ended up shooting at low resolution instead of high res.  Just imagine that the image is four times the size...  Please remember that these are "first light" results!

As you can see, there is plenty of work to do!  Out of the 700 frames I took, only 20 ended up being good enough for Registax processing (typically, one would want several hundred).  I dutifully stacked them anyway, and then applied the wavelets and balanced contrast for good measure.  It's a poor quality image, but it's a nice taste of what will be coming in the future!

The two craters near the top are (from left to right) Atlas and Hercules.  Near the middle of the image, you can see Cepheus above the slightly-larger Franklin.

The most obvious paths to improvement: Turn up the resolution, and Don't try to shoot through clouds!

Shot at f/12.1 on 2006-04-02 9:00pm EDT.  Moon at 4.6 days old.  Horrible seeing.