Don's Discoveries

Read first-hand accounts of some of Don's cometary discoveries:

To date, I have discovered ten comets.  I also independently discovered Periodic Comet de Vico on Sept. 18, 1995.  For most of my comet hunting years I subscribed to a telex or mailgram/telegram service for new comet finds.  In 1994 I began using an old IBM 286 computer with modem to communicate with the SAO.  I updated this in late 1995 to a Windows-based computer.

I also found a comet long after it was discovered.  In November 1991 I picked up Comet Shoemaker-Levy 1991d in the morning sky and reported it to the SAO.  They phoned back in a couple of hours saying it had been discovered earlier in the year, raced into the morning sky, brightened a bit, and had been generally neglected over the past few months.

I have swept over nearly a dozen comets later found by others.  I missed them because they were too faint for me to see (this happened mostly from Loma Prieta), or they later brightened shortly before discovery by others.  The most recent case was with C/2006 T1 (Levy), discovered by David Levy shortly after it outburst in early October 2006.  I had swept over its location at least twice in the previous month, missing it because it was still faint (dormant) and had not yet outburst.

Two of my first four comets apparently disintegrated after rounding the sun.  My first had a hyperbola orbit so it will never return.  Periodic Comet Machholz 1 (P/96), on the other hand, returns every 5.24 years and comes closer to the sun than any known periodic comet.

Confirmation photo Three of my comets, 1985e, 1988j and 1992k, have short observational arcs and are still assumed to be in parabolic orbits.  If anything remains of the first two, could any of these return sometime in the future?

I'll always remember discovering Comet 1985a from Big Bear.  My wife, Laura, and I had a very difficult time reaching the SAO.  It was a holiday, phones didn't work, Western Union was nonoperational.  We finally got through.

Comet Tanaka-Machholz (1992d) was found on Mar. 31, 1992, the day before we were to drive to the Los Angeles Airport to pick up our newly-adopted son from Korea.  The following morning, the time when the comet is normally confirmed, found us on the road in Southern California.  I stopped along the freeway to try to confirm it, but was clouded out.  I then called Dr. Marsden from a fast food restaurant to learn that it had been confirmed and named.

Periodic Comet Machholz 2 seemed to be full of surprises.  First, it turned out to be periodic, returning every 5.23 years.  Then it outburst.  Finally, little comets were found nearby, indicating recent splits.