This page offers links to John's scientific interests and various files you can view or download.  Click on a category below to see a list of what's available.  Hint:  we add the newest files to the bottom of each list.

Astronomy Images
Light curve measurements - asteroids and variable stars
Occultations
Spectra
Astronomy equipment and software -- evaluations and design
Papers on topics other than astronomy

Astronomy Images

Below are some images from the many thousands that I've done over recent years.  Because I work mostly on asteriod light curves, much of my imaging is "boring", i.e., I take hundreds of images a night of the same stars to look for variations in their brightness.  Those images may not be pretty, but the curve that results is! 

On the other hand, as a change of pace, I often image planets, the moon, or interesting galaxies and nebulae -- I've included a selection to share here.  I should note that they do not represent "state of the art" for amateur work: many amateurs specialize in imaging, and with better equipment, locations, and skill, their work aproaches professional levels.  My goal is not perfection but rather the joy of seeing what's there and gradual improvement in my technique.

	M82 taken 1/21/2000.  f12 4600 seconds, MaxEnt and DDP processed.  Shows apparent star/supernova?.
	M82 taken 1/7/2001 f12 13x10min, MaxEnt and DDP processed.  Star/supernova missing.
	Mare Nectaris area.  This shows the many small craters in the area.  See if you can spot the DHCs mentioned below.
	Dark Haloed Lunar Craters (DHC).  The moon has several dozen small craters that are surrounded by darker material.  Not much is known about the cause of the dark material; however, volcanic emission seems to be one of the leading theories.  After stumbling onto a pair of these in Mare Nectaris, I have been studying the contrast under different lighting conditions to gain some additional insight.  The relatively poor seeing in our mid-Atlantic area, and the small refractor, make this study at the edge of feasibility.  Here is a  picture of the area, somewhat enhanced. Theopholis (75 km dia) is the large crater at the bottom of the picture.  The upper DHC is about 3 miles in diameter, the lower one is about half that, and not easy to see under this lighting.
	M57. Stimulated by the excellent picture on the right by a well known astrophotographer,  I took the picture on the left with my 6 inch.  Clearly the right hand picture is better, but the left hand shows that with effort you can still do good work with a small scope.  Exposure was about 2 hours.
	M31, The Great Galaxy in Andromeda.  This is a group of three exposures  with 20 min. exposures at f4.  The mosaic was put together using MaximDL (first attempt).  With heavier processing, one can bring out more of the central region, if desired.
Click for image of comet	Comet 2002 (Ikeya-Zha). UL Comet on June 9, 2000 shows some faint anti-tail to the right.  To show the tails more clearly, I averaged 16 comet images each rotated 22.5 deg, then subtracted from the original giving UR image.  On Jun 21, in strong moonlight, I took 30x1 min exp, median combined.  The comet has about half its former brightness.   Background moonlight is about 9x the background of the June 9 image.  Even so, with no processing, one sees a much sharper and relatively brighter anti-tail to the west (right, sunward) as we pass through the plane of the sun-comet-earth.  In the one minute exposures, the anti-tail is about 10 counts out of about 2000 background, the comet nucleus is about 500 counts above background.
	Mars, taken August 24, 2003.  Black and white image compared to a drawing done a few days earlier.  (Please read the text below images for more details.)
	Images of Mars on August 25, 2003.  Color vs. back and white. (See text below images for further description.)

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Light Curve Measurements - asteroids and variable stars

Most asteroids are not perfect spheres, so as they rotate, their oblong shapes reflect different amounts of sunlight back to us.  Thus, even though we cannot actually see an asteroid, we can measure its reflected light, and this allows us to infer its rotation time.  Amateurs take the lead in this work, and many of us measure scores of asteroid light curves each year.  Not only are asteroid rotation rates interesting in themselves (why not faster?  why not slower?), after several years of measurements, it is often possible to use the data to infer the actual shape of the asteroid. 

I show below a small sample of the asteroids I have measured.  The results have been published in Minor Planet Bulletin.  I have also written papers on some of the techniques used in this work. 

My work on light curves of variable stars follows the asteroid list.

Below are measurements of selected variable stars.  Some variables produce light curves that look similar to asteroid light curves, but of course, there is considerably more to variables than that. The best source of information about variable stars is AAVSO, the American Association of Variable Star Observers, based in Cambridge, MA.  Despite its name, AAVSO is a worldwide organization.  It maintains a significant archive of observation data and collects new observations that it makes accessible through the AAVSO International Database.  The first paper listed below describes a highly unusual variable that AAVSO began targeting for more data in March 2009.

Asteroid Occultations

Asteroids, of course, move through space in their orbits.  As they travel, they sometimes pass in front of stars we can see, thus eclipsing the star and casting a shadow onto the earth.  These events can be predicted, with the paths and timing of the shadow path on the earth accurate to a few tens of miles and tens of seconds.  If one or several people set up observing stations across the path of the shadow, and if they measure the duration of the eclipse, then it's possible to calcualte the size and shape of the asteroid.  This work can be done either from a fixed observatory, or from portable equipment.  This is a very active field of study, with excellent resources on the web. 

As of early 2009, I have attempted about thirty occultation events: weather wiped out about twenty of them.  Half the remainder failed due to equipment problems or my human error.  The other half were successful, but in most cases, the shadow did not pass over the telescope, so the result was a "miss" (this is often a very important observation).  In one case, I had a "hit".  This record of results sounds worse than it is: as my skills improve, I will see more "hits".  Here are two files that explain occultation observing in more detail.

Spectra

I have completed a few spectral studies of comets.  More to come.  I've included a paper on the techniques and the set-up I use when doing spectra.

Astronomy Equipment and Software

One of my great loves is working in the shop, taking an idea for a new elelctronic device or observing tool or software program from concept to reality.  I also enjoy solving problems with equipment I'm using, or analyzing why some products work the way I expect them to, but some don't. 

Here is a selection of papers on equipment related subjects.  These include descriptions of equipment, evaluation of various designs or products, better methods of making particular measurements, how I built the 18-inch telescope, etc. Enjoy!

Papers on topics other than astronomy

The world has other challenges besides understanding the universe.  I've given much thought recently to Global Warming and related non-astronomy issues.