The Silent Observer's Photographic Observations

One of my strongest interests in the field of amateur astronomy is astrophotography.  Unfortunately, to "do it right" for deep sky photography requires a large aperture, fast optics, CCD camera and attached computer, high precision drive, guide scope and preferably an autoguider, and can run into ten thousand dollars or more for the setup.  With my level of disposable income, that would be about a forty year project.

What I can do, though, is use the small telescope I have, and inexpensive or improvised methods, to take photos of the largest, brightest objects in the sky.  An inexpensive Newtonian with a camera adapter can be used for afocal and eyepiece projection photographs of the Moon with exposures of under a second, and reveal detail comparable to what would be seen in an eyepiece.  Similarly, any setup that will let you safely view the Sun can probably be used to take short exposure photos of the solar disk, including showing sunspots.  Below, you'll see my first efforts in this direction.

The Moon

 
Hanging Wall phenomenonA couple days after the January 31, 1999 Blue Moon, I was observing the location where the terminator was visible at the limb of the Moon -- a combination of libration and phase let me see an extremely shallow light effect on a part of the Moon that's almost over the mean limb and onto the far side.  The effect was such that I could see, in a couple locations along the limb and terminator, crater walls that were illuminated even though the crater floor was in complete darkness.  While this effect is common, and there are certain craters that put on a monthly show of a lit rim and dark floor, in one such location, the connection between the illuminated wall and the rest of the Moon was invisible, and in the eyepiece the effect was that of a small lit portion of the lunar surface hanging in space beyond the limb.  It looked like nothing so much as the sort of mirage you can see in the desert, where the sky reflects from a thermal layer near the ground and makes distant mountains seem to float in space.

Petavius and StevinusOf course, there are no mirages on the Moon; they're an atmospheric phenomenon, and the lunar atmosphere, if you want to call it that, is so thin it'd be quite effective in filling vacuum tubes.  The effect, though, was truly startling, and startling was the last thing I expected when I pointed my telescope at the Moon.

That same observing session, I also noticed a very prominent cast shadow from the central peak(s) in crater Petavius.  The shadow was visible as a dark triangle next to the peak itself, cast onto the far wall of the crater.  It was so prominent that I completely missed the very prominent rille in the same crater -- despite the fact that the light was perfect for seeing it, and it's one of the most visible rilles on the entire face of the Moon.  If it's any compensation, I can (barely) make out the rille in the photograph I took, even though that image shows the entire face of the Moon in about a 20 mm diameter image on the film.

Almost Full -- ThumbnailBTW, both of thse images are from the same negative; taken with a Meade 4400, 114 mm aperture, f/8 Newtonian and Celestron 25 mm SMA eyepiece, using a hand held afocal setup though a 50 mm f/1.4 lens on my ancient Pentax Spotmatic -- lens wide open, and 1/30 shutter speed on unhypered generic 400 speed color print film.  Here's the full frame; this is the sharpest of three good images I got.  I also attempted four frames using a Celestron 10 mm SMA, which would have given much larger images, but all four were so underexposed as to show no discernible image on the negative.

Here are more recent images -- these were taken the evening of 17 February 2000 through my Celestron 25 mm SMA and Orion 2X Shorty Barlow with 50 mm f/1.4 lens on my Pentax, onto Price Club (probably Fuji) 400 speed color print film.

The Sinus Iridum region (28k), showing Plato and the Alpine Valley as well as some craters on the limb of the Moon.
Here's a closeup of the limb region of the previous shot, showing the Pythagoras and Babbage region (librated away, 41k), Rukl 2, including Carpenter and Anaximander.  Pythagoras is the crater with the far rim seeming to hang off the edge of the Moon.
In the original print, you can see the illuminated tip of the central peak in Pythagoras: here's a green channel only image (21k) that makes it more visible.

I've recently made a mount to put my Alaris WeeCam USB web camera on a telescope, and took a few images of the Moon with my Meade 4400 -- chosen because the equatorial mount let me keep the Moon in field long enough to shoot some short movies as well.  The movies are too large for this space -- they run around a megabyte each -- but here are the stills:

This is a single frame of the southern highlands, showing Tycho and the (rather fat) ray in Longmontanus.  Rutherford, Porter, and subcraters D and C within Clavius are visible. Image was taken at prime focus, f/8 on a 114 mm primary (f.l. 910 mm).  Processing was a simple histrogram stretch and unsharp mask.

Here's a detail from the above image showing Longmontanus and the sunrise "ray" I reported several months ago.  This is similar to what I saw that first night; unfortunately, I haven't been able to catch this any earlier in the Lunar morning yet, so I don't know if the ray is narrower with lower sun angles.

This is another single frame, this time of Mare Imbrium with Plato, the Alps, and the Appennines.  Once again, prime focus, f/8 114 mm, and processed with only a histogram stretch and unsharp mask.  Both this and the above southern highlands image were captured at the hardware limit of my camera, 640x480, 24 bit color.

Here's a smaller image of the southern highlands, made with Astrostack from an AVI containing about 100 frames.  After stacking, I applied a CLAHE with strength 2, which greatly enhances the contrast in the mare region to the upper right, as well as a mild unsharp mask.  This image is the same resolution as the AVI, 320x240, but the processing was done at 2x resample, 640x480; that image is available here.

On October 5, 2000, I photographed what may be a previously unreported sunrise ray in Curtius.  Follow this link for more on that. Curtius Ray


The Sun

The Sun is more difficult to photograph than the Moon, at least if you're working with budget equipment.  Where the main problem with the Moon is gathering enough light to use an exposure shorter than a second, the problem with the Sun is to avoid burning your eyes or your camera equipment with the concentrated light and heat.  The professional method is to use a filter, either made of reflective Mylar or coated optical glass, in either case with the general idea being to reflect the vast bulk of the Sun's light and heat, while allowing only a fraction of one percent of the radiation through the telescope to your eye or film.

Unfortunately, like so much of the quality equipment available in this pursuit, even the amateur versions of these filters aren't cheap, and attempting to view or photograph the sun through a telescope (or even with the naked eye) can result in permanent damage.  Galileo Galilei, the first human ever to report sunspots (not to mention the first person to record craters on the Moon and the discoverer of Saturn's rings and the first known moons other than Luna herself), was blind for the last decade of his life from the effect of the Sun's rays through even the small, poor telescopes he was able to make in the 17th century.

SunspotsFortunately, there's a completely safe method of viewing the sun that once again makes light gathering power an advantage: projection.

Essentially, the telescope is used to produce, not an aerial real image that can be seen with the eye, but a projected real image cast onto a white surface such as a card.  Even a very modest telescope, such as my old Jason 80 mm reflector (missing 20% of the coating from the mirror, even) can project a useful solar image several inches across when the sky is clear, and if the focuser and eyepieces are quality components made of metal instead of plastic, there's little chance of damaging your telescope with the concentrated light.  It is worth checking that the eyepiece and focuser aren't getting hot, but I haven't had any problems with it.  Larger telescopes can be used with more magnification to produce images of part of the solar disk that allow seeing limb darkening, structure in sunspots, convection zones (the brighter area just around a sunspot) and even faculae (similar brighter spots not associated with spots), all in unfiltered white light.  I've been able to observe spots as small as about an arcminute in angular size -- though small is relative; a spot this size is still more than three times larger than the Earth.

Of course, any projected image bright enough to see well in daylight can be photographed as shown above -- with a very inexpensive camera, needing only adjustable focus (to get a large enough image) and internal metering (to get the exposure correct for the solar image).

I took some more photos of spots on 19 February, 2000 -- the best one, scanned and processed by stretching the histogram and retouching out some dust on the bottom of my scanner glass, is here (81k).

I've also found it easy to sketch sunspots -- one can actually trace the locations of the spots against the projected image, then fill in the details with more magnification.  I've done several sketches this way, when conditions and my schedule have permitted me to set up under clear skies and take a few mintues to sketch.  I've also experimented with using my recently purchased web camera to make digital images, a method similar to the film photography used for the above image, but with much less attractive results.
 

Here's my first sketch from March 20, 1999 (53k)
Here are later ones:
July 27, 1999 (16k)
August 19, 1999 (14k)
December 25, 1999 (13k)
January 28, 2000 (7k)
February 17, 2000 (5k)
February 19, 2000 (19k)
And here's my first digital sunspot capture: January 29, 2000 (9k)

If you have comments or suggestions, email me at silent1@ix.netcom.com