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Memories of Comet Honda-Mrkos-Pajdusakova (1974-f)

with thoughts of its splendid 2016-2017 return as Comet 45P

by P. Clay Sherrod
January 7, 2017
As Comet Honda-Mrkos-Pajdusakova (45P) streaks across our nighttime skies this winter, displaying a beautiful green coma and long linear tail several degrees to the northeast, I was inspired to go into the Arkansas Sky Observatories' Archives of bound research documents and find my records of observing this comet in 1974 and 1975.  Barely visible visually in our skies prior to the remarkable Comet West (1975n) in 1975, comet 45P.

45p Dec22s

Comet 45P photographed and provided by comet photographer Michael Jager of Austria on December 22, 2016.
Comet Honda-Mrkos-Pajdusakova was discovered long before I first observed it in 1974, and had been missed or very unfavorably placed for observation since its original discovery in 1948 by three comet hunters, M.Honda, A. Mrkos, and L. Pajdusakova, each spotting the comet independently, thus this interloper sporting the names of all three who simultaneously found this comet at magnitude 9 as a very faint "smudge" of light, quite diffuse and without a nucleus or tail.  The comet in that year rapidly faded to magnitude 13 and was not seen again until 1954 when it reached magnitude 8.4 only for a very short period of time.

With its orbital period of only 5.3 years, we would think that this comet would be easily visible at each pass, but this is certainly not the case; it was not visible in 1959 because of the geometry of the Earth-Sun-Comet orientation, but it was observed very sparingly in subsequent passages.  It was not until the winter of 1974-75 that the comet would become favorable for observations in evening skies; by that time there were many times more observers - both amateur and professional - who were taking a keen interest in the nature of comets.

In 1974-75, we had just seen the passage of "The Comet of the Century," Comet Kohoutek 1973-f, regretfully deemed to be the brightest comet perhaps ever seen in modern times.  The world awaited this comet with eager anticipation and thousands of small telescopes were sold to an unsuspecting public hoping to catch this media-frenzied celestial visitor.  When the comet was first discovered by Czech astronomer Lubos Kohoutek, it was so far away in our solar system, yet so intrinsically bright, that Dr. Brian Marsden of the Havard-Smithsonian Astrophysical Observatory properly surmised that - by the time the comet would come into the Earth' vicinity - it would be incredibly bright and thus the comet mania grew.

But soon we realized that Comet Kohoutek was going to be the fizzle of the century and many of both the general public AND the astronomical community was discouraged from the realm of comet exploration.

But the early 1970's brought an incredible influx of bright and exciting comets, most of them ignored, under-observed or missed entirely by the apathy of the Kohoutek-burned human race.  I must admit, that comet 1974-f was NOT among those exciting comets.  But at the time I was hooked on comet observing and Dr. Marsden had become my mentor to continue to monitor all that I could.  A phone call one evening at the observatory from Marsden was all that I needed to immediately turn our modest telescopes in search of Comet Honda-Mrkos-Pajdusakova.  Our first attempts to locate the comet - all done visually at that time - were unsuccessful;  the now-veteran comet observer John Bortle was the first to spot it in his 12-inch Newtonian on November 15 at a faint magnitude less than 12.5; his next effort on December 4 saw the comet had brightened to a still-dim magnitude 10.4.

By December 10, 1974, using the wide field Comet Searching six-inch f/5 wide field refractor, the comet was spotted at Arkansas Sky Observatories by myself and volunteers Jim Henry and John Evans.  It was nothing more in the low power field as a smudge of diffuse glow, but we had picked up the comet nonetheless and reported it as we did all comets to the SAO/International Astronomical Union's Central Bureau of Astronomical Telegrams (CBAT) as a very faint extended diffuse object only three arc-minutes across and magnitude 10.8 visually.

1974 CBATs

The IAU/CBAT Telegram that was distributed (mailed) Dec. 13, 1974
Although photography was available to us at the Edgehill facility (to later be designation Harvard MPC ObsCode H43), the practice at the time was to record physical parameters and morphology visually.  Following is my report to Dr. Marsden, Mr. Dennis Milan of both Sky and Telescope magazine and the Comet Recorder for the Association of Lunar and Planetary Observers, and to Daniel Green (now the director of the CBAT) who edited The Comet out of North Carolina.

"I searched on November 28, December 2,3,4,5,8,9 and tonight (Dec. 9) photographed the exact area where the comet should be reaching stellar magnitude 13 with the 6-inch at prime focus....stars of 12th and 13th magnitude were quite obvious on 10 to 15 minute exposures.

"Tonight the comet was finally spotted with some difficulty....transparency was excellent (6th mag. stars visible to the naked eye) and seeing good.  At 23.5x in the 6" the comet was at first not visible; however with 60x it was quite obvious using averted vision.  No tail was visible, nor did it show any nuclear condensation
[nucleus].  It appeared as a borderless diffuse glow approximately 3 arc minutes diameter.....the comet being only about 12 degrees above the trees in the distance....enclosed is a quick drawing....."

45P 1974

Not a work of art, but a quick sketch done 43 years ago at the telescope
And now - 43 years later as much has changed in the world of astronomy and otherwise - comet 1974-f is once again in my evening skies, but now as Comet 45P Honda-Mrkos-Pajdusakova.
Finally - after 70 years of always being noted as a "diffuse glow" with no central condensation, the remarkable Comet 45P as shown in photographer Michael Jager's outstanding photo at top has been an object well worth monitoring and watching for these old eyes after five decades.

Today, with modern CCD cameras, digital computerized processing of images, and precision telescopes only dreamed of in 1974, we are able to capture "faint diffuse objects" with the clarity and splendor that they truly possess.  Much has changed, not only in the equipment that we use, but also in our understanding of these comets, visitors from the depths of our solar system of which we are still hanging onto uncertainties and some mysteries of their nature and origins.

And - to me - this faint diffuse object now serves as a spark of memory preserved in the old yellowing archives of research from Arkansas Sky Observatories' rich 50-year history.

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