D-Files and Amateur Telescope Making
from The Denver Observer February 2006
by Ron Pearson, DAS
Being an amateur astronomer means looking with interest at the sky with telescopes or the naked-eye for the joy of it. Sometimes we get diverted into “sidelines,” like CCD imaging, mirror grinding, or woodworking so we can build our own beautiful telescopes, or metal casting and machining so we can spend thousands on machine tools so we can save money by building our own scopes. Some of us get very deep into deep-sky observing, logging the Herschel 400 objects after bagging the Messier “M” objects, Caldwell objects and other deep sky wonders cataloged by others over the past 200 years or so. Being a geologist, with a strong interest in planetary geology, my bent has always been toward the “shallow-sky” objects— planets, the moon, comets, and asteroids. But I still enjoy hunting down and viewing deep sky objects at dark sky star parties, or photographing them using my (budget) limited technology of film and push-to telescopes. Sometimes all these interests can coincide, like an interest in the history of astronomy, Chamberlin Observatory and its historic 20-inch Clark telescope.
During the August, 2005 “Weekend Under the Stars” Star party at Fox Park, Wyoming, I was looking at a star chart in the Observers Guide with Ted Cox. Ted and I were looking for dark nebula in the Milky Way mapped by the late 19th century astronomer E.E. Barnard, as I was thinking of photographing some of them with my telescope that night. In perusing the star chart I noticed a star with the name “Howe” next to it. Then I found a couple more in different parts of the sky. I asked Ted if he knew if this was “our” Dr. Howe, the first director and cofounder of Chamberlin Observatory. Ted thought it could be, and David Shouldice remembered that Howe had discovered a number of double stars while at the U. of Cincinnati before coming to Denver. This was kind of interesting, since few names are emblazoned, even if in tiny print, on star charts. I wondered if any of these discoveries could have been made with the 20-inch Clark telescope in Chamberlin. This revived some memories of discussions I had with a friend several years ago. He claimed that no astronomical discoveries of any significance had occurred using the 20-inch at Chamberlin. This was part of his rationale in arguing that the 20-inch could be replaced with a “modern” telescope as was being planned. At Fox Park, I went on to take some astrophotos of Messier objects in Sagittarius and NCG 7000 in Cygnus the next two nights.
After the star party, the question still sort of stuck in the back of my head. What, if anything, had been discovered with the 20-inch Clark by Dr. Howe? I have a copy of one Dr. Howe’s books; A Study of the Sky, first published in 1896. This is a book that is part “popular astronomy” written for the general public, while being fairly detailed about telescope and observatory design. It provides a lot of insight and details of the design of Chamberlin Observatory, the Clark telescope and its instruments. But it was published about the time Chamberlin Observatory saw first light, and Dr. Howe does not discuss his previous discoveries. The biography of Dr. Howe published in 2003, Denver’s Pioneer Astronomer (Howe and Stencel), provides a rich history of Dr. Howe’s life, the people and problems associated with building the University of Denver and Chamberlin Observatory. However the biography provides few specifics regarding any discoveries or observations made with the 20-inch by Dr. Howe, with the exception of some of the events and observations of Halley’s Comet in 1910 and the solar eclipse of 1918. In turning to the internet, to see what others may have published or written about Dr. Howe, I struck “paydirt,” as they might have put it in Denver, in the early 1890s.
During most of the 19th century the technology only allowed astronomers to look at objects visually and measure their position in the sky. The mathematics to predict when and where moving objects would appear in the sky was only refined in the 19th century. This was the main area of Dr. Howe’s expertise, measuring positions of comets and asteroids and computing their orbits. Astronomers perceived that our solar system was in the center of the Milky Way galaxy and that all those “faint fuzzies” out there were probably part of the Milky Way, although they weren’t sure. They spent most of their time identifying and measuring the positions of stars and those objects that were not like stars. The early 20th century saw the end of the mapping of objects in the sky visually by astronomers and the beginning of the investigations to understand what these objects were using spectrometers and photography.
A Brief History of Deep-Sky Object
Observing List of Nebulae Discovered
by Dr. Howe at Chamberlin Observatory
The NGC was published the same year, 1888, in which Humphrey Barker Chamberlin offered to fund a new telescope for Dr. Herbert Alonzo Howe at the new University of Denver. Chamberlin Observatory’s 20-inch Clark telescope saw first light in 1894, just as the first IC list was to be published. But history had not passed them by. One of the instruments Dr. Howe acquired for the telescope was a filar micrometer through another philanthropist of astronomy, Miss Catherine W. Bruce of New York City. The micrometer was designed by Dr. Howe and Saegmuller. It became known as the “Bruce Micrometer”* and is on display today in Chamberlin Observatory. With this instrument’s spider webs Howe could measure the location and size of non-stellar objects with great precision. The Bruce Micrometer was such a significant instrument that Dr. Howe was asked to publish a special paper on its construction and operation. He later improved it further with special lights and motors. The aperture of the 20-inch refractor, under the clear, dark skies of the Colorado Front Range meant he could see fainter objects with more detail than most of the telescopes in the eastern U.S., and the 20-inch was the 3rd largest telescope west of the Mississippi River until 1917. With the Bruce Micrometer he could measure their positions more accurately and precisely. Based on the newest compilation from original sources of NGC-IC objects, NGC/ IC team member, Steinicke, credits Dr. Howe with the discovery of 60 IC objects between 1894 and 1900. Steinicke found that Dreyer had credited Dr. Howe with five NGC objects and one IC object previously found by others. Eliminating these duplicate objects, the NGC/IC project attributed 60 new discoveries to Howe from Chamberlin Observatory as listed in Steinicke’s table. Steinecke’s listing provides some useful information regarding the type of object and the constellations they are found in, as well as the date of discovery. However, if you wanted to find these objects there are no coordinates provided.
The NGC/IC Projects home page provides a link where you can download the entire catalog listing in ASCII format. This is very convenient because with that file you can create your own observing list to find these objects in order to make follow-up observations or get a better idea of what they are and how they fit into the entire catalog of objects. However, the NGC/ IC lists do not identify the discoverer. After downloading the file, I loaded it into an Excel spreadsheet. It was then simple to add a column to the spreadsheet, which I called “Howe.” Using Steinicke’s list, I went down the list by IC number and entered Howe to the row. It is then a simple matter to filter the spreadsheet of all 5,386 IC objects and bring-up only the IC objects discovered by Dr. Howe. Sorting by other parameters in the list is also possible which can provide other insights into the discoveries. The table of Dr. Howe’s IC Discoveries created by the author are provided as a PDF document HERE.
What can be said of these discoveries? Are they “significant?” Well, I would ask, how do you define significant? Do you define the negative by saying, “I’ve never heard of that object, so it’s not significant?” Is M42 more significant than some anonymous galaxy tens of thousands of light-years away that you with your 20-inch dob would have a tough time finding? Does the Hubble Deep Field and image of hundreds of “insignificant” galaxies in an arc-second of the sky make the image or the telescope insignificant?
This table only lists the “top ten” discoverers, although many more are listed by Pothier. Pothier noted this table was compiled in 1998, before the NGC/IC Project is complete, but “this attempt gives an indication of the observer’s diligence.” As of December 2005, the NGC/IC project credited Howe with 60 discoveries, increasing his “Existing” object discovery ratio to 94%!
References for Tables:
Of historic significance, these galaxies were discovered the old-fashioned way — with hard work. The astronomer, using one of the finest instruments of its day, knew what he was looking for, knew what others had found and therefore could immediately assess at the eyepiece, that out of thousands of other “faint fuzzies” already discovered, what he saw was something not seen or noticed by other observers, and he measured them micrometrically and described them. He also spent perhaps many hundreds of hours following up the discoveries of others, in order to reproduce their results and improve their descriptions or positions.
This was discovery science at the end of the 19th century and early 20th. Perhaps the most significant statement you can make regarding these discoveries is that Dr. Howe was not “cherry-picking.” By the end of the 19th century all of the “easy” nebulae had been found and cataloged. The IC II objects were all found photographically according to Dreyer. If you look at the column of visual magnitudes of these objects, they are all very faint—their average magnitude is 14.2. The faintest object is 15.5 and the brightest is 12.9. This is testimony to the darkness of the skies over Denver at the time, the high quality of the telescope and of course the skill of the observer. Many of these objects occur near other already “found” nebula that were poorly located or not clearly described by earlier observers. To find these objects then, separating the known from the unknown and then determining their positions with a micrometer speaks volumes about the tenacity of the observer. If you look at the dates of the discoveries it is intriguing that many are made in January, probably when Dr. Howe was most likely on Christmas break from teaching duties. While the world was out celebrating the turn of the new 20th century on January 1, 1900, Dr. Howe was in a very cold observatory discovering ICs 1741, 1693, and 1745, as he had done on January 1, 1895, discovering and measuring ICs 1592 and 1598.
A ranking of the astronomers whose discoveries contributed to the Index Catalogs has been tabulated by Y. Pothier in France. A portion of his table is provided above. This ranking, based upon the number of discoveries, shows that Chamberlin Observatory is 9th. Dr. Howe is ranked just below E. E. Barnard for the number of objects discovered with a much higher percentage of confirmed objects than most others. Clearly this was an extremely productive time for Chamberlin Observatory.
The publication of the Second Index Catalog (IC II), in 1908 brought to a close 137 years of discoveries from mapping the non-stellar objects by dozens of astronomers starting with Charles Messier’s first catalog in 1771. I am reminded of the map of North America I saw this past summer at the special exhibit presented at the Denver Museum of Nature & Science’s 200th Anniversary of the Lewis and Clark Expedition of 1805. The first map shown at the beginning of the exhibit had the outline of the coast and a few interior details of North America, mostly of the eastern U.S. and southern Canada along the fur trades routes of the Great Lakes. Several years after their journey, Clark published a new edition of the map of North America. Virtually all the significant geographic features such as mountain ranges, rivers and villages had filled in the map using their discoveries and the discoveries of other mountain men, explorers and pioneers.
Dr. Howe, using the 20-inch Clark refractor, and the Bruce Micrometer of Chamberlin Observatory, filled in the last great discoveries of the visual and early photographic observatories that began with Charles Messier in France. Clearly Dr. Howe was “Denver’s Pioneer Astronomer” and he could not have done this pioneering work without the “20-inch Clark equatorial,” as he called the telescope. Mapping the objects in the sky was clearly a significant undertaking of 19th century astronomers. Mapping the sky continued throughout the 20th century and to this day with more and larger virtually automated instruments like the Sloan Digital Sky Survey. We are fortunate that his great instrument is still around and can still be used much as it was then. There really is no reason it could not continue its research role in astrometry and photometry of comets asteroids, variable stars and even the new field of extra-solar planet finding, with modern add-on tools of ccd imaging, software and filters.
After publishing these discoveries, Dr. Howe turned more of his attention and the 20-inch telescope time to “shallow-sky” objects, measuring, observing and calculating the orbits of numerous comets and asteroids, in addition to his teaching duties and becoming a dean of the university. Dr. Howe and his students made and published thousands of measurements of comets and asteroids using the Bruce Micrometer. During the same period, an assistant, Vesta Slipher at Lowell Observatory was using a 24-inch Clark refractor. After many failures he was beginning to get the hang of taking spectral photographs of these mysterious nebulae and realizing that some of these objects had significant red-shifts in their spectral lines. The next great period of discovery in astronomy was just beginning.
November 2006 will mark 80 years since Dr. Howe died. Perhaps one way to honor “our” pioneer astronomer will be for DAS and other FRASC astronomers to adopt the list of 60 IC galaxies as their next challenge in deep-sky observing. We have the Messier List, the Caldwell list, the Herschel 400 and the Herschel 2 lists. We now have 60 very faint, very challenging galaxies and nebulae to re-discover for ourselves—we can call them the “Howe Objects.” These are not “low-hanging fruit” for deep-sky objects and locating them will require a fairly large telescope and good observers, or a good CCD camera to image. Observe them and take good notes and images. The descriptions in the Dreyer catalogs still need improvement.
Readers who wish to learn more about Dr. Howe’s discoveries with the 20-inch Clark at Chamberlin Observatory, should see the biography of Dr. H. A. Howe, by Dr. R. Stencel and H. J. Howe, Denver’s Pioneer Astronomer (2003), which contains a complete bibliography of Dr. Howe’s publications and discussions of other important observations and events.—R.P.