Ukiah, California Latitude Observatory

© Brooke Clarke 2007

	Straddle Level for Vertical axis

	Roll Off Roof Observatory Building protected from sun. Two out buildings to the right. Viewed from Observatory Ave.
	Roll Off Roof Observatory Building protected from sun. Astronomer's house to the left. Viewed from Observatory Ave.
	Astronomer's house. Viewed from Observatory Ave.
	Out buildings. Viewed from Observatory Ave.
	Out buildings, Roll Off Roof Observatory, house. Viewed from Luce Ave.
	Roll Off Roof Observatory, house. Viewed from  Luce Ave.
NOAA 1930? photo of first astronomer's house & observatory. It looks to be much closer to the hills than the current location?	The first house is now on an adjacent property.
Ukiah Latitude Observatory Looking South Popular Science Monthly Nov 1909	Zenith Telescope Popular Science Monthly Nov 1909 Figure 4 When scope is rotated so that horizontal axis is East-West the scope moves in the meridian plane. There are stops on the lower azimuth circle that can be set to 180 deg. If the scope is pointing 10 deg East of meridian and the scope rotated about the vertical axis to the other stop 180 degrees away then it will be pointing 10 degrees West of the meridian allowing the difference between the zenith angles to be measured using the eyepiece micrometer.

Starting in 1899 observations were made to determine the location of the Earth's rotational axis, i.e. finding the latitude.  To do this a handful of observatories were spread pretty much equally around the globe at 39 degrees 08 minutes North Latitude.  They sequentially observed the same set of about 60 star pairs each night measuring the zenith distance and time of meridian crossing using a Vertical Zenith Telescope (VZT).

In the 1977 NOAA report (See References below) they say "Probably no other project in modern science has continued for so long unchanged in purpose, equipment, or technique and has managed to produce such a large volume of high-quality data."

The book Latitude by Carter & Carter ( ISBN 1557500169) has a good description of the problem of finding the Latitude and the brilliant work of Chandler and Newcomb.  Ukiah was the location of one of the small number of Latitude Observatories  (Wiki) which measured their latitude nightly in order to help define the wobble of the Earth's poles.  The observatories were started in 1899 and decommissioned in 1982.

The book Longitude by Dava Sobel describes the 40 year effort (1730 - 1770) that John Harrison (wiki) went through to develop the marine chronometer.  There's also a movie based on  the book called Longitude.  What Harrison accomplished is fantastic both in terms of a marine chronometer but also in terms of horology.  For example he was the inventor of the temperature compensated pendulum.  But once accurate balance wheel clocks or better quartz clocks or GPS navigation receivers are available the problem of finding the longitude goes away.

Alfred L. Loomis (wiki) got half a dozen of the Shortt precision pendulum clocks and discovered that they were effected by the Moon's gravity and was the first to publish this limitation of pendulum clocks (Wiki) in 1931.  The book Tuxedo Park by Jennet Conant has details of that.  Some details of the Moon and Sun gravity tides is on TVB's web page Lunar/Solar Tides and Pendulum Clocks.

The movement of the North pole caused by the wobble of the Earth was a much larger problem that took longer to solve than the longitude problem.  Many astronomical observations can not be made without a knowledge where the North pole is located (i.e. where the spin axis of the Earth is pointing in space).  The Latitude Observatories operated for almost a century.  It's only been very recently that a connection with El Nino and the wobble has been found.  The problem with the wobble is that it's not predictable as of 2007. 

There are a number of modern ways that the orientation of the Earth is currently being measured.  This is coordinated by the International Earth Rotation  & Reference Systems Service in France.  They make use of such methods as laser range finding to Earth satellites and the Moon and Very Long Base Line Interferometry.

To see the Ukiah sky check out my Sky-Weather-Astronomy web cam.  If it's not cloudy at night you can see dozens of stars on line, millions if you are here.  The zenith is close to the top center of the image and Polaris is above the tree on the right.

There are forces acting on the Earth that cause it to orbit the Sun and translate in space that are not related to to the latitude problem.  They result in the precession and nutation of the poles.

The unbalanced forces that can effect the latitude come about because the distance between the North and South poles is shorter than the diameter at the Equator.  This gives rise to a Euler period of about 300 days if the Earth is assumed to be rigid or the period Chandler predicted of about 305 days.  Wobble is added on top of the Euler spiral and is caused by the circulation of air and water, earthquakes, continental drift and changes in the Earth's interior.

On some of my other web pages there's information about the PZT but in reference to it's use to determine the time based on the Earth's rotation.  But in the D.O.C. U.S. Coast and Geodetic Survey Special Publication No. 27, 1915 "Latitude Observations with Photographic Zenith Tube at Gaithersburg, MD."  is a report on the use of the PZT. (atitudeo00uscouoft.pdf)
In this paper problems with earlier observation methods are described.

"The secular variation of longitudes and plate tectonic motion" describes how the data from the Latitude Observatories were used to test the plate theory.  This implies that the time of star meridian crossing was measured along with the zenith angle.

Ukiah Years	Astronomer	References
1899 to 1903	Frank Schlesinger	Cal Micrometer
1903 to sep 1907	Sidney D. Townley April 10, 1867 - March 18, 1946	San Francisco Earthquake damage in Ukiah:  5:12 AM - April 18, 1906 Assistant Professor of Applied Mathematics at Stanford in 1907 - 1946 charter member & Editor of  Seismological Society of America  1911 to 1929
1907 to 1911	James D. Maddrill
?
1918 to 1922	Ferdinand Neubauer
		Frank Schlesinger testing of automatic Zenith Camera at Allegheny Observatory
1 Jly 1948 - 30 Jun 1949	Leonard F. Caouette	1988 star pairs observed (1611 in Gaithersburg)
?	William F. Meyer

The observatories built specifically for the International Latitude Service were all located very near 39 degrees 8 minutes North Latitude.  The observation method was as developed by Talcott in 1834 which requires observing pairs of stars where the distance is balanced on the North and South sides of the zenith and the time of culmination is reasonably close.  This allows making better measurements than prior methods.  It requires that the observatories be located all around the Earth and very close to the same latitude so that they are looking at the same star pairs thus allowing for error corrections.

In Longitude order:

N 39:08:12.51 W 77:11:55.85 Gaithersburg, Maryland, USA
N 39:08.3 W 84:25.4 Cincinnati, Ohio, USA - built for political reasons, too close to Gaithersburg to be of much value., closed early in the program
N 39:08:14.26 W 123:12:42.54 Ukiah, California, USA
N 39:08.1 E 141:07.9 Mizusawa, Japan National Institutes of Natural Sciences National Astronomical Observatory of Japan Mizusawa VERA Observatory -
N 39:08.0 E 66:52.9 Kitab in Uzbekistan
N 39:08:13.76   E 8:18:41.90 Carloforte, Italy

The telescope is made specifically for measuring the angle between straight up and a star near the zenith. 

American History - Zenith Telescopes - Julius Wanschaff made the Ukiah scope. 108 mm ( 4 1/4") aperture and 1300 (51.8") mm focal length (f12).    This is a much higher quality instrument than the earlier Troughton & Simms zenith scopes.  I've heard that the angular accuracy was good to 0.1 arc seconds.

The astronomer would press a button when the star crossed the horizontal line to mark the chronograph.  But the key operation would be to adjust the pointing of the scope to measure the zenith angle of the star as it rises to maximum height and then recedes.

This is the concrete base for the vertical zenith Telescope.  It's a waist high concrete pier with surrounded with wood that matches the interior walls.  You can see three light colored circles where the feet of the telescope sat.  The observer sat in a chair and looked into an eyepiece that was maybe half a foot above the concrete.  In front of the observer was an electrical switch that when activated would make a mark on the chronometer.

Clock

Strasser & Rohde 599 most likely an Invar rod pendulum with temperature compensation with lens shaped bob.
The small top hand is seconds, the sweep hand is minutes and the bottom hand is a 24 hand.  Set to run at sidereal time not standard time.  The purpose of the clock is to know which star will be visible next.   The clock would have an electrical switch that would close for a short time once each second used to make seconds ticks on the chronograph.

I think that later the Heathkit Most Accurate digital clock was used.  Note that the clock is to tell the astronomer when a star needs to be observed and maybe the exact moment to observe it.

Chronograph

Building

Seismometers

The plot plan made in 1991 shows the boundaries, North-South direction and a number of survey markers.

	Magnetic Station Azimuth Mark	RM 3	Meridian House (being restored) Marker
	Magnetic Station	RM4C	RM5
RM1	Magnetic Station Azimuth Mark

The Northern most marker is a concrete post with an angle iron bracket at the top and labeled "Magnetic Station Azimuth Mark".
It's not clear to me what this is about.  Maybe there was a magnetic filed station here?
Note that along a North-South line through this marker is the "Ukiah Magnetic 1925" marker and a notation showing a fifteen foot nominal radius.  There are 5 other survey markers all radiating out from the Ukiah Magnetic 1925 marker labeled: RM1, RM2, RM3, RM4 and RM5.  Maybe for Relative Magnetic n?
Marker photos by PaulK.

Thermometers

The bracket probably held a thermometer and to it's left is a conversion chart between F and C.  The chart was not typed with the minus signs, but they have been added by hand.  It also is missing the decimal point for the tenths of a degree C making it awkward to read.  There were also thermometers outside on either side of the building that were recorded at about the center of the observation run each night.

Photo by PaulK 30 May 2009

Explained in Topographic, Trigonometric and Geodetic Surveying: Including Geographic, Exploratory, and By Herbert Michael
Wilson, 1912 J. Wiley & Sons 932 pgs.

Talcott's method took into account that the star catalogs then available (myabe a hand full) had errors for some stars.  By observing a group of stars (maybe a couple dozen) in a night and by pairing the stars so that one was North of the zenith and the other was South of the zenith not only instrument errors but also star catalog errors could be detected and corrected.

The same star list was used by all the observatories.  This allows for further error detection and reduction and is why all the lattitude observatories are very close to 39:08 N.

The stars are in pairs where each star in a pair is very close to the same zenith angle.  The scope is set for the average zenith angle of the pair using the vertical circle and vernier and the scope is set East or West depending on which star culminates first.  When that star crosses the meridian the micrometer eyepiece is set to measure how far from the central angle the star is.  Then the scope is revolved 180 degrees about the vertical axis and when the second star crosses the meridian the micrometer eyepiece is again used to read how far it is from the central angle of that pair.  The micrometer readings are much more accurate than an angle read from the vettical circle and is the key benefit of the Talcott method.

The current data is at Earth Orientation Center - Polar motion for the last 365 days -

"Ah see by de papers dat de urf's axis am a wobbling an' dey dunno wat fo'.  But ah know wat makes de urf's axis wobble.  Do you see all dis oil dese men am a takin' out of de urf?  Well wat do you spose de good Lord put dat oil in dere fo'?  Wy to grease de axis wif, of course, an' when dey take it all out, wat else can de axis do but to wobble." Attributed to a Preacher in the oil region of Texas, but probably theTownley's humor.