Telescope at Smithsonian
Clock at Smithsonian
drum at Smithsonian
Level for Vertical axis
Clock at Smithsonian
|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.
Viewed from Observatory Ave.
Viewed from Observatory Ave.
|Out buildings, Roll Off
Roof Observatory, house.
Viewed from Luce Ave.
Orange netting at target building location.
|Roll Off Roof Observatory,
Viewed from Luce Ave.
1930? photo of first astronomer's house &
It looks to be much closer to the hills than the current location?
first house is now on an adjacent property.
Latitude Observatory Looking South
Popular Science Monthly Nov 1909
Note that the telescope is sitting on a pedestal that's waist high. The reason for
the North facing door is so that when the telescope is horizontal it can see a North
alignment mark at the top of a waist high concrete pier in the meridian alignment building.
Popular Science Monthly Nov 1909
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.
Within a year or two of moving to Ukiah (early 1990s) I saw a street sign "Observatory Ave." and turned onto it searching for an observatory and found a roll off roof observatory. The local historical building had a little information about it. This web page is about the Ukiah latitude observatory (Wiki) part of a half dozen identical observatories all located at the same latitude all around the world.
Official Ukiah Latitude Observatory facebook web page.
This means that the location observatories in relation to the spin axis of the Earth are also changing. The next year a handful of observatories measured their latitude for a year and found a variation. As would be expected observatories close in longitude would have the same latitude variation (top 3 plots) and an observatory on the opposite side of the Earth would be out of phase (bottom plot).
Ref: On the contribution of the Geodetic Institute Potsdam to the International Latitude Service, Joachim Höpfner, Paper presented on the occasion of the centennial of the first observations of the International Latitude Service in 1999
Note that one division on the vertical axis is 0.1 arc seconds and the total variation over a year is about 0.5 arc seconds.
Even today it's far from a trivial exercise to measure angles this small. The GPS in a cell phone can not do this yet (2015).
The book Longitude by Dava Sobel describes the 40 year effort (1730 - 1770) that John Harrison (wiki) went through to develop the marine chronometer (Wiki). 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 (Wiki). For example he was the inventor of the temperature compensated pendulum (Wiki). But once accurate balance wheel clocks or better quartz clocks or GPS navigation receivers are available the problem of finding the longitude goes away.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.
Alfred L. Loomis (wiki) got half a dozen of the Shortt precision pendulum clocks (Wiki) 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.
I've tried to compile some information on who the astronomers have been here in Ukiah.
||1899 to 1903||Frank Schlesinger (Wiki)
||1903 to 907||Sidney D. Townley (Wiki)
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
||James D. Maddrill
Astronomy: Community, Careers, and Power,
1859-1940 By John Lankford, Ricky L.
"James D. Maddrill (1880 - ?) illustrates a unique form of failure. I know of no other case in which the doctorate (1907) was conferred before the dissertation had been completed. Just how Maddrill convinced William Wallace Campbell and the graduate dean at Berkeley to enter into such an arrangement is unclear. In any case, Maddrill assumed the post of director of the Ukiah International Latitude Observatory with a Ph.D. but still had to complete the dissertation in astronomical spectroscopy. Campbell continually put pressure on Maddrill, who responded with excuses that included physical and mental illness as well as the distraction of a failed love affair. Maddrill apparently made little progress and in 1912 left Ukiah for Berkeley where he hoped to complete his theses. It is not clear whether this was ever done. At all events, Maddrill's astromonical career came to an end and he disappeared from view."
|4||1912 to 1922
||U. F. Meyer
||1922 to 1946
||Leonard F. Caouette
star pairs observed (1611 in Gaithersburg)
|N 39:08:12.51||W 77:11:55.85||Gaithersburg, Maryland||USA|
|N 39:08.3||W 84:25.4||Cincinnati, Ohio||USA||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||Uzbekistan|
|N 39:08:13.76||E 8:18:41.90||Carloforte||Italy|
The wobble is on the order of 30 feet. A rule of thumb is that one arc second of angle change along a line of constant longitude (i.e. changes in latitude) is about 100 feet, then the total magnitude of the wobble is about 0.3 arc seconds. It would be good to measure at least to 10% of the thing being measured or better 1% so the accuracy of the final measurement should be on the order of 0.03 or better 0.003 arc seconds. If many measurements are made and then averaged the improvement goes as the square root of the number of readings. Until I learn more about how the measurements were post processed it's hard to say how good an individual measurement needs to be.
To check plate tectonics in say 1965 there would be 66 years of data. If observatories were moving 2 inches per year then in 66 years there would be a change of about 132 inches or 11 feet. Since 11 feet is in the same order of magnitude as 30 feet plate motion should be detected and it's direction determined. This would require that the observed transit times be converted into Lat and Lon.
Unpacking (UP Fig) figures in order taken. Photos by
|UP Fig 1 as installed by the movers the
mount is not positioned with the axis of the ways left
right in this photo
The microscope to read the vernier scale (Wiki) is missing.
Blue shrink wrapped package in background is the sidereal pendulum clock. Not unwrapped yet, will be in interpretive building.
|UP Fig 2 marked: J. Wanschaff, Berlin
||UP Fig 3 The target building as seen from
|UP Fig 4 top of the mount with the "Y"
supports typical of a transit instrument (Wiki).
Note a surveyor's Wye level (description
on external page) has a provision to remove the
telescope tube from it's mount and reinstall it
reversed. This allows canceling some errors thus
making a more accurate measurement. I'm sure this
was done here too, probably at initial alignment and maybe
once every so many years for alignment checks.
||UP Fig 5 telescope tube
||UP Fig 6 telescope tube
|UP Fig 7 Light house. attaches to
||UP Fig 8 Light house. opening for
lamp. Thumb nut at top holds parabolic reflector.
I've heard that this electric lamp housing replaced a similar one that used Calcium Carbide in Observatories where there was no electricity. But Ukiah had electricity from the beginning so didn't use that one.
|UP Fig 9 Hole in shaft for light from
lamp house. Threads for counter weight.
|UP Fig 10 "Y" support on left has
slot allowing up/down adj.
"Y" support on right is solid metal.
|UP Fig 11 Arm on right has adjustment screw
for zenith angle adjustment. One vernier microscope
holder is installed, but the opposite holder is missing,
but it's 2 mounting screws are there.
||UP Fig 12 Counter weight
|UP Fig 13 counter weight. Don't know
what the two thumb screws are for.
||UP Fig 14 terminals on counter weight for
lamp house wiring
||UP Fig 15 striding level. The 4 rods
that trap the striding level are missing.
|UP Fig 16 striding
||UP Fig 17 striding level shown on telescope
||UP Fig 18 target building
|UP Fig 19 Behind door of target building,
hinged sheet metal panel at top closed.
||UP Fig 20 Sheet metal panel opened showing
place holder wooden targer bar.
||UP Fig 21 Roll-Off roof observatory
|UP Fig 22 heating/cooling unit in
||UP Fig 23 Target bar in interpretive
building after unpacking
Both targets can be independently adjusted to precisely match the telescope offset.
|UP Fig 24 right target
It's not clear why the left positioning bolt is retracted.
Maybe after the target bar was removed someone was making measurements or ???
|UP Fig 25 left target
||UP Fig 26 Target bar sitting in target
Mystery vertical slit in the sheep metal. It was copied from the original vertical slit see UP Fig 35 below
|UP Fig 27 close up of target building.
Since there's no hole in the top of the sheet metal the roof vent probably was to cool the building rather than vent fumes from an open flame.
|UP Fig 28 eyepiece end of telescope tube,
missing filar micrometer. (Wiki)
||UP Fig 29 Vertical circle. vernier
microscope holder present, but the reading microscope is
||UP Fig 30 Rotating the mount to align
the "Y" axis.
|UP Fig 31
Rotating the mount to align the "Y" axis.
||UP Fig 32 Donated Equatorial mount (Wiki)
for another scope.
||UP Fig 33 Target (Meridian) building seen
from properly rotated mount.
|UP Fig 34 Target building seen from
properly rotated mount.
Note telescope can be aimed horizontally at target then rotated 180 degrees in azimuth and 180 degrees in elevation and look at the other target.
|UP Fig 35 The origional target house sheet
||UP Fig 36 Pétanque
court between the observatory and Observatory Ave.
Redwood Empire Boules Club (UDJ article)
|UP Fig 37
The wheels are spring loaded, tension adjusted by swrews below.
Note screw in slot showing limit of motion.
|UP Fig 38
View from above. Vernier microscope holder as about 7:00.
Two screw holes for another vernier microscope holder at about 2:00.
|UP Fig 39
The pully in center locks (CW) or unlocks (CCW) azimuth movement.
|UP Fig 40 3 of 7 package stickers
||UP Fig 41 4 of 7 package stickers
||UP Fig 42 azimuth locked CW
|UP Fig 43 azimuth locked CCW
Knob at bottom center drives radial rod and clamps circle.
Works like clamp knob on vertical circle.
Knob above clamp knob is select/release (about 90 deg motion) for latches at 0 and 180 degrees.
|UP Fig 44 Close up of striding level scales
Hard to photograph, see UP Fig 49
|UP Fig 45 Wiring for meridian (target)
(Wiki: Knob-and-tube wiring) 1880 to 1930.
|UP Fig 46 vertical circle missing two
levels. The central knob/pulley does not want to
Maybe because scope is resting on circle. Try again when on mount.
|UP Fig 47 Counterweight
It was thought that it was a box and that the two thumb screws allowed opening the box to change the internal weights. But that's not the case, the weight is a single part.
The cover seems to only be a holder for the electrical terminals and maybe the removable plate was made in
different weights as a fine adjustment for balance?
|UP Fig 48 counter weight
|UP Fig 49 striding
one division is 2.2 arc seconds.
It's not yet clear how the controls are used on the vertical
|UP Fig 50 The 2 sensitive levels are
level mounts are way off level.
|UP Fig 51
||UP Fig 52
|UP Fig 53 There is
a Vernier scale for focus or to set scale scale factor for
the filar micrometer?
45 degree angle for pirsm (or mirror).
|UP Fig 54 The Vernier scale on both the
vertical circles is very faint.
Holder for scale viewing microscope is empty.
Magnifying glass and 45 deg reflector to light scale.
|UP Fig 55 Large handle loosens cap, you can
see the gap.
This allows moving the levels but not the telescope.
Notice holes in outer telescope tube for cooling.
Level mounts rotated to closer to level.
|UP Fig 56 This is a
fine control of the vertical angle of the telescope.
||UP Fig 57 Are the grooves the support
wheels run in
because of wear or were they put in from the beginning.
The roller on the right is jammed in the up position and is
tipping the horizontal axis to the left. That's why the adjusting
arm on the right has it's lower end to the right of where it shold be.
|UP Fig 65 Eyepiece hole (no eyepiece) but
with close focus
lens engaged as used to look at meridian targets.
|UP Fig 66 Eyepiece
hole (no eyepiece) but with close focus
lens disengaged as used to look at stars. This way no change is needed to any of the star viewing settings.
|UP Fig 61 Main clamp. Knob on back side
moves the central
rod to clamp telescope to horizontal axis. Once clamped screw allows adjusting angle.
There's a similar rod and clamp knob for the horizontal circle.
|Fig 73 Adjustment bolts at right top and
against each other to control height of Wyes on one side
to match height of Yye on other side.
|Fig 70 Left side support wheels
The marker screw is at bottom of slot, but wheel is holding
axle up off of Wye. Needs adjustment.
|Fig 71 Right side support wheels
Bottom screw not run in to take up more weight, yet.
The Striding Level is used to adjust the three feet of the
mount to plumb the mount. Done by rotating the telescope.
The horizontal circle zero is set by sighting the North star
(Wiki) at a time when it's true north. This happens at two
times each day that are 12 sidereal hours apart.
There's a good chance that it can be done in the daytime.
The horizontal motion stops need to be set so that the scope is
in the North - South meridian when at either stop by sighting
the North Star at the correct time.
Then the meridian house targets need to be adjusted so that they are each on the meridian. Once this is done the horizontal circle is typically not read, the scope is used either to the West or to the East of the pier at a stop.
To make a horizontal move the clamp screw is loosened.
See UP Fig 16 for the knob at the top
center of the mount. The scope rotated 180 degrees.
So the procedure to move to a new star would be to:
Stars are measured in pairs where one star will be on the North
side of the zenith and the other will be on the South side of
There is two ways to do it, for example the star that's North of the zenith could be measured with the telescope on the East or the West of the pier and the other star in the pair measured by rotating the scope 180 degrees about the vertical axis.
Is it always done the same way or done differently on different
These photos were taken at the time the telescope was being
packed in order to ship it to the Smithsonian for storage.
From the Estate of David Pettey, Ukiah Latitude Observer 1972 to 1982
|1982 Fig 1 "Zenith telescope in use at
Ukiah, Calif. Pier is protected from accidental
disturbance by a wooden casing."
SPDT knife switch near electrical box.
What does it do?
In later photos appears to be an on/off switch,
which would be for lamp house.
|1982 Fig 2
||1982 Fig 3 Note plumbers tape holding
near eyepiece. What is it?
|1982 Fig 4
||1982 Fig 5 Wiring for lamp house
Recording thermometer (barometer?) at left on wall.
|1982 Fig 6 List of star pairs
|1982 Fig 7
||1982 Fig 8
||1982 Fig 9
|1982 Fig 10 Note vernier reading
||1982 Fig 11 Rods form cage around striding
||1982 Fig 12 Mount, after scope removed.
|1982 Fig 13 Note: (metal?) disks where
Bakelite on/off switch for lamp house.
Mount on floor at right.
Fig 49 Striding Level
one division is 2.2 arc seconds.
Fig 64 Striding level numbers every 10 divisions.
bubble is 33 divisions long
This is the most sensitive level and sits at right angles to the vertical axis of the mount. It is used to plumb the vertical axis of the mount by adjusting the three leveling feet and rotating the mount about it's vertical axis.
Note that part of the calibration process is centering the bubble in the striding level relative to it's feet. This can be checked by turning the level 180 degrees and seeing if the bubble remains centered.
One division corresponds to about 2.2 arc seconds of angle.
Ref: Science, Vol XXIII, No. 593, 1913 pg 756 "The California Earthquake at Ukiah", by Sidney D. Townley. The last paragraph of this article mentions that the latitude levels have a sensitivity of 1.0 (with no units specified, but I'd assume that to mean 1 arc second per division, but that's strange since this pair of levels are smaller than the striding level.
This eyepiece coupled with the the pair of levels on the vertical circle are the key elements in making the star zenith angle measurement.
As of Feb 2015 we have not received this as well as a number of other items this size and smaller.
A method was developed to check the repeatability of the filar mechanism by taking readings on each division of the targets in the meridian house.
Photos of another filar micrometer courtesy of the City of Ukiah taken on the East Coast.
A Method for Determining the value of an average space of a latitude-level in terms of a micrometer-turn by Frank Schlessinger, 1901 shows that one micrometer turn is 40 arc seconds on angle. Based on meridian star observations and the telescope levels.
Fig EP 1 this one has a magnifying glass built in.
Photos of the Ukiah observatory show a hand held
Most clocks tell time based on the Sun, where at true Noon the
clock shows 12:00. A sundial would show some time within
plus or minus 15 minutes of the actual time because of the
Equation of Time (Wiki)
and because the sundial may not be located on the centerline of
the time zone.
Sidereal time is based on when a star (other than the Sun)
crossed the local meridian (Wiki)
at midnight. The rate of a clock telling sidereal time is
slightly faster than a clock telling civilian time. In the
case of a pendulum clock the rate can easily be set to sidereal
by moving the pendulum up from it's normal position. The
rate can be checked by noting that when a given star crosses the
local meridian should be the same sidereal time every
night. The location of a star (Wiki)
is specified by it's Right ascension (Wiki: RA)
and Declination (Wiki).
The RA can be specified as an angle between 0 and 360 degrees,
or as hours: minutes: seconds of sidereal time.
So the astronomers can regulate the rate of their clock by
checking what time each known star crossed the local meridian,
but also can set their clock because the right ascension of all
the stars they are looking at is known and tabulated. The
|Clk Fig 1 Face
Time shown: 19 hours (bottom hand), 12 minutes (long hand
off right side), 36 seconds (top hand).
|Clk Fig 3 Clock was shipped with pendulum
Might have been better to remove it for shipping.
an example of damage done by pendulum.
Two holes at left and right just above top of dial used to
anchor clock to wall.
|Clk Fig 5 The arm that couples the pendulum
to the escapment
appears to be bent.
|Clk Fig 6 Key still in shipping wrap.
||Fig 7 Clock on Wall
Pendulum has: main adjustable bob,
smaller adjustable lower bob,
Weight shelf near top with up/down adjustment.
Cage at bottom locks pendulum at center.
Exactly North of the zenith telescope are a pair of targets. They are sitting on a masonry pier that's about three feet on a side and four feet tall. The masonry is surrounded with a sheet metal box with a hole for each of the targets, a vertical slit between the targets (reason unknown) and a vent hole at the top which would be necessary for the carbide lantern which was the first light source, but not needed when they switched to an electric lamp.
The purpose of the targets is to zero the azimuth (North) direction. By using two targets the telescope can be set to North when it's on either side of the mount.
As seen from zenith telescope
Target bar sitting on bench.
There are two translucent scales with ruler marks.
Behind each scale is a light reflector at about 45 degrees to
back light the scales using either the early calcium carbide
lantern (Wiki) or the soon to be installed electric light in the center.
The sheet metal may be been there to prevent fires?
Original sheet metal box
Target bar sitting in house.
STA LAT LON ELEVATION STANAME
UKI 39.1372 -123.2106 0.199 Ukiah, NEIC
Is this the Latitude Observatory? The Lat is the same (39.1372 vs. 39.137294) so yes.
The USGS shows UKI as an open seismic station, probably a typo.
Station Azimuth Mark
|Meridian House (being restored)
Brick masonary pier under blue plastic.
PID - KT2010
Station Azimuth Mark
PID Reference Object Distance Geod. Az dddmmss.s KT2010 UKIAH MAGNETIC AZ MK 99.828 METERS 00000
NAD 83(1986)- 39 08 18.30181(N) 123 12 43.35939(W) AD(1984.00) 2 KT2024 UKIAH MAGNETIC RM 3 42.632 METERS 01959
KT2023 UKIAH MAGNETIC RM 4 31.887 METERS 02829
KT2025 UKIAH MAGNETIC A POINT 29.822 METERS 10237
KT2011 UKIAH LATITUDE 1925 41.413 METERS 13547
KT2001 UKIAH MUNICIPAL AIRPORT BEACON ON H APPROX. 3.0 KM 2223614.1
DB6008 UKIAH MAGNETIC RM 1 15.193 METERS 22349
DB6009 UKIAH MAGNETIC RM 2 15.925 METERS 30730
Some years ago the grounds were developed with a walking path
and native plant maze. On Saturday 31 Jan 2015 when there
to take photos of the unpacking of the telescope there were
maybe a dozen groups of from 1 to 4 people walking, walking
their dogs, exercising or playing Pétanque
(similar to Bocce ball Wiki)on the
|Palying Pétanque (Wiki)
every Saturday afternoon.
Redwood Empire Boules Club (UDJ article)
|Maze using native plants
Also see Google satellite view at top of page.
see Google satellite view at top of page.
|Office (Interpretative center) building
The so-called Horrebow-Talcott method fixed latitude "by observing differences of zenith distances of stars culminating within a short time of each other, and at nearly the same altitude, on opposite sides of the zenith.". Ref 5: Captain Albert E. Theberge, Albert. (2001) The Coast Survey 1807-1867 National Oceanic and Atmospheric Administration Library.Explained in Topographic, Trigonometric and Geodetic Surveying: Including Geographic, Exploratory, and By Herbert Michael Wilson, 1912 J. Wiley & Sons 932 pgs.
By this method the latitude is determined by observing with a micrometer the difference between the nearly equal zenith distances of two stars which pass the meridian within a few minutes of each other, one north and the other south of the zenith. The Zenith telescope is set to the proper zenith distance for the first star with the bubbles of the delicate level, which is attached to the telescope, adjusted and read. After the star has been observed, the telescope is reversed on its vertical axis without altering the position of the level. The telescope can now be adjusted to point to the same zenith distance as used for the first star. Since the stations have nearly the same latitude, the same stars can be used at each, thus assuring homogeneous results.
From Popular Science Monthly, Vol LXXV, No. 5, Nov 1909.
Φ = ½(δn + δs) + ½(mn - ms)*R + ½(ln + ls) +½(rn - rs)
subscript s means to the south, and n to the north
Φ = latitude
δ = measured star declination from vertical circle
m = micrometer measurement
R = micrometer to angle conversion factor
l = reading of vertical circle levels
r = refraction correction as a function of telescope zenith distance
If the two stars are at exactly the same declination δ and the instrument is reversed without disturbing the pointing, then the m, l and r terms become zero and the latitude becomes δ star zenith angle.
Note the declination (Wiki) of a star is measured the same way a latitude. So for an observer on the equator looking at a star with zero degrees declination would look straight up, zenith angle of zero.
For an observer at 39 degrees North a star with a declination of 39 N would be straight up.
Need to determine how the vertical circle is calibrated. Is straight up zero or can it be set to 39:08?
In the same Popular Science article referenced above on the equation there is a discussion about the impact of weather and incomplete measurements.
Historically, averaged over all the observatories, on 46.5% of the nights there is good weather. The odds of all six observatories to have good weather on the same night is about one in a hundred.
When making a measurement on a given star if a mistake is made you can not turn back the sky and make the measurement again, it's a missed measurement.
Although Ukiah averaged about 60% of all possible measurements the other observatories were not that good and they averaged about 50%.
So the odds of measuring all the stars at all stations on the same might are about 1/4096. Estimated once every 20 years.
Twelve groups of stars (I to XII), each containing eight pairs total. Six latitude pairs not more than 24 degrees from the zenith and two refraction pairs about sixty degrees from the zenith were selected for observation. Eight pairs per group total. Each star in a latitude pair is within 16 minutes of arc and the refraction pairs are within 5 minutes of arc [Ref ASoP1899]. So the filar micrometer may have a range of plus and minus 20 minutes of arc?
The brightness (astronomical magnitude (Wiki, my magnitude web page) ranges from 4.0 to 7.4. Note the common navigation stars are much brighter (Wiki). The time interval between culminations vary between 4 and 16 minutes.
Ref: letter of 11 April 1947 from DOC to Miss Marian R. Marvin, Librarian, Ukiah Public Library.
fact check: 24 hours (1440 minutes) divided by [ (12 groups * (6 pair + 2 pair) *2= ] 192 stars = 7.5 minutes between stars on average.
As of Feb 2015 I'm still looking for the list, but did find out a little more about it from the article:
[Ref ASoP1899] Program for the International Geodetic Association for Observing Variations in Latitude by Frank Schlesinger, Publications of the Astronomical Society of the Pacific, Nov 20, 1899.
The refraction (Wiki) pairs allow determining if a anomaly is caused by refraction (the effect gets larger as a star gets closer to the horizon) and a parallax error which would be the same for observatories on opposite sides of the Earth.
0h - 2h
2h - 4h Nov 2
4h - 6h Dec 7
6h - 8h Jan 5
8h - 10h Jan 31
10h - 12h Feb 25
12h - 14h Mar 22
14h - 16h Apr 16
16h - 18h May 12
18h - 20h Jun 9
20h - 22h Jly 10
XII 22h - 24h Aug 14
The quality of dividing engines may have been a factor in choosing who made the telescope since the quality of the vertical circle is the prime specification for this telescope.
Both the horizontal and vertical circles can be read directly to 10 arc seconds. The filar micrometer increases the angular resolution maybe 100 times to 0.1 arc seconds.
In order to mark a ruler to protractor with divisions that are accurate some type of mechanism is needed to eliminate errors caused by variations caused by human variations. Jesse Ramsden (Wiki) developed a dividing engine 45" in diameter with 2,160 teeth (6* 360) on it's circumference. In order to do that he also invented a screw cutting lathe using change gears custom made to the pitch needed. Note: A screw with notches filed into it was used to cut the big wheel. Then the big wheel was measured and corrected and then tested. Over a number of cycles of cutting and measuring the quality of the dividing engine was improved.
Note that the problem was getting a precise division of the circle that then could be used to mark other circles.
The photo at left is from the Annual Report of the Board of Regents of the Smithsonian Institution, July 1890.
It was in 1890 that the Ramsden dividing engine was donated to the Smithsonian.
The first 45" Ramsden dividing engine was made in 1775 and was capable of dividing to 1/2 minute of arc.
As part of his award from the commissioners of longitude (see above) he made public his design not only for the dividing engine but also for the screw cutting lathe that was needed to make the dividing engine.
A Ramsden engine was used to improve the 8 foot radius scale on Halley’s 8-foot (radius) Iron Mural Quadrant at Greenwich.
This web page shows a lot of similarity with the latitude observatories.
As time went on the diameter of the circle needed to get a specified accuracy (say 1 arc minute for the 45" Ramsden engine, or 1 arc second for the 5" Wild T2 theodolite) has decreased with time.
But I still need to examine the dividing on the vertical circle of the zenith telescope to see how precisely it can be read.
UP Fig 58 Vertical circle has numbers every 5 degrees.
Large divisions every 1 degree.
Small divisions every 10 minutes.
The vernier divisions are 10 arc seconds each.
Filar micrometer to read finer angles.
UP Fig 60 Horizontal circle has numbers every 5 degrees.
Large divisions every 1 degree.
Short divisions every 10 minutes.
The vernier divisions are 10 arc seconds each.
Close UP of Vertical vernier
Marked 10 8 6 4 2 0 (minutes)
Each minute is divided into 6 parts
each of which is 10 seconds
Progress of Astronomy by William C. Winlock
In another article in the same 1890 report titled: Progress of Astronomy by William C. Winlock there's information about the Earth's latitude:
"The EARTH-Variat'ion of latitude.-The subject of the change of terrestrial latitudes, to which allusion has been made in previous reports, continues to receive considerable attention from astronomers and geographers. The following results have been obtained by Dr. Kiistner, in continuation of his former researches, from 7 pairs of stars at three different times of the year:
where dA represents the correction to the assumed constant of aberration. The direct inference from these figures is that in 7 months the latitude of Berlin decreased 0".44. Polkowa showed about the same time a similar change:
Epoch. Latitude of Berlin. 1884.32
+520 30' 16". 73-0.82dA 1884.70 16.96"+0.83dA
a decrease of 0".33 from 1884.70 to 1885.31.
Latitude of Polkowa
The general agreement of these results certainly calls for further investigation; and to test the matter Mr. Preston has been sent out by the U. 8. Coast Survey, and Dr. Marcuse by the International Geodetic Commission, to Honolulu, which is at the opposite end of the earth's diameter from Berlin, and by simultaneous observations at these two stations it is hoped the question will be settled.
It is quite possible that the origin of the apparent change at Berlin in 1884-1885 is meteorological, a view to which Dr. Foerster inclined in bringing' the matter before the Association Geodesique in 1888. The whole question is, then, whether there are changes in the disposition of atmospheric strata sufficient to account for the facts observed, or the axis of rotation and the axis of inertia of the earth are not sensibly coincident.
A complete resume of the subject is given by M. Tisserand in the Bulletin Astronomique for 8eptember, 1890.
Mr. Ricco has experimented with a somewhat novel demonstration of the rotundity of the earth. At the observatory of Palermo, which is situated at a distance of 1-1/4 miles from the Mediterranean and 236 feet above sea level, a great number of photographs of the sun reflected from the surface of the water have been taken a few minutes after rising or before setting, and they show that the diameter in the plane of reflection is less in the reflected image than in the direct. This deformation is due to the fact that the surface of the water forms a cylindrical mirror, with axis horizontal and normal to the plane of reflection. The amount of the observed flattening accords well with that demanded by theory.
A back of the envelope calculation.
Vertical circle is about 9" diameter, 28-1/4" circumference.
There are small divisions every 10 minutes.
There are 21,600 (360 * 60) minutes in a circle, or
2,160 each 10' small divisions.
28-1/4" / 2,160 = 0.013" between small divisions.
Vernier scale (Wiki)
I think the length of the vernier scale is 10 degrees on the circle or 60 small (10 arc minute) divisions, or 600 arc minutes long. But a vernier scale divides the smallest division by the number of of divisions on the vernier so in this case 10 arc minutes (600 arc seconds) are divided into 60 parts or 10 arc seconds per division on the vernier.
The key idea is that a vernier divides the smallest division on the circle by the number of divisions on the vernier.
While the commonest vernier has 10 divisions, more can be used, 60 in this case. In the case of a full circle the vernier might be made to cover 1/2 or 3/4 of the circle resulting in much higher resolution, but how accurate would depend on the quality of the dividing engine. Also the more divisions in the vernier the longer it takes to read it.
This is a modern part of determining the period of the Earth's rotation as well as other astronomy. The idea is to measure the time it takes a pulse of laser light to go from the Earth based observatory to one of the retro reflectors on the Moon and come back.
It turns out that, just like the latitude observatory, great care is needed to make precision measurements. In the case of the lunar ranging the Earth's gravity tides that cause the ocean water level to move up and down also cause the bedrock at the top of mountains to move up and down (Wiki).
There are a couple of ways to measure the movement of the telescope used to make the lunar distance measurements:
1) precision GPS - but it also measures all the changes, not just the change due to earth time
2) a gravity meter, like that GWR that's used for the APOLLO system, allows correcting the telescope position to account for the earth's tide.
3449956Apache Point Observatory Lunar Laser-ranging Operation (APOLLO)
Force measuring instrument,Goodkind John M, Prothero William A, Jun 17, 1969, 73/382.00R, 73/514.18
Superconducting bearing for borehole and survey gravimeters,Robert L. Kleinberg, Douglas D. Griffin, Richard J. Warburton, Gwr Instruments, Apr 20, 1993,
310/90.5, 33/366.11, 324/346, 73/382.00R -
The Basics of Lunar Ranging
Wiki- Lunar Laser Ranging experiment
ScienceShot: Decades-Old Soviet Reflector Spotted on the Moon
While taking photos of the unpacking of the zenith telescope I discovered a donated mount (see UnPacking Fig 32 above). Martin Bradley posted photos of these parts on the Antique Telescope Society Yahoo Group photos section about 12 Jan 2014. Photo Courtesy of City of Ukiah
I have placed thumbnail photos Fig 1 to 19 from that posting below.
Photos York 20 and up I took.
Fig York 01
Very large eyepiece hole to accept filar micrometer
Fig York 02
Mount on Peir
Fig York 03
Filters for filar illumination
Fig York 04
T. Cook & Sons 1871
Fig York 05
Clockwork for RA drive
Fig York 06
Fig York 07
71 1/4" Focus
Fig York 08
Fig York 09
Fig York 10
Lower light is from EP hole.
Upper light is from 45 deg mirror.
Fig York 20 T. Cook & Sons 1871 mount
Fig York 21 T. Cook & Sons 1871
Fig York 22 pier for T. Cook & Sons 1871 mount
Fig York 23 telescope tube
Fig York 24 light from EP hole coming out filter
Fig York 25 degree wheel hours in roman minutes in numerals.
Fig York 26 "T. Cook & Sons 1871" mount
Gailleo (Wiki) discovers the moons of Jupiter (Wiki) The idea that another planet can have moons violated Aristotle's cosmology (Wiki).1630
By measuring the Occultation (Wiki) of Jupiter's moon Io at different times of the year (different distances between the Earth and Jupiter) the speed of light (Wiki) can be calculated.
William Gascoigne (Wiki) sees a spider web inside a telescope where it's focused. He invented the telescopic sight. He also developed the filar eyepiece where a hair moved by a screw allows measuring the diameter of the image, or refining the angle the telescope was pointing. Note this filar eyepiece is different from the later and improved filar micrometer (Wiki).1666
PS In an earlier version of this web page I used the term filar eyepiece when I meant filar micrometer, now fixed.
Isaac Newton (Wiki) writes THE book on modern Optics (Wiki: History, Optics) (my web page on optics) and believes in a corpuscular theory (Wiki), i.e. light is made up of particles.1725
James Bradley (Wiki) tried to measure the distance to a star using stellar parallax (Wiki).1775
Note: At this time there was still debate about whether or not the Sun rotated about the Earth. Heliocentrism (Wiki) was still being questioned and stellar parallax was part of that debate.
But the dividing engine had not been invented and he could not make the measurement. But in the process he discovered the aberration of light (Wiki, Wiki).
To make the parallax measurement you need to observe a star at two times six months apart (with the Earth on opposite sides of the Sun) to get the longest baseline. The exact two days of the year depend on the location of the star.
The annual stellar aberration (Wiki) is given by:
k = Θ - Φ ~ v/c
k is the constant of aberration (20″.49552)
Θ is the arrival angle of the light
Φ is the declination of the telescope
v is the speed of the Earth in it's orbit around the Sun (29,780 m/s)
c is the speed of light (299,792,458 meters/second)
Jesse Ramsden (Wiki) invents the geared screw cutting lathe (Wiki) in order to make a precision screw to match a worm gear for a dividing engine. The 45" diameter engine has one tooth per minute of angle and a dial on the worm screw (Wiki) probably could be read to 10 seconds of angle.1838
By the end of the 18th century angles could be measured using Vernier scales on engine divided circles to 10 seconds of arc. Star positions could be further refined by using a filar micrometer to better than one arc second. Today we can measure fractions of a milli arc second (0."0001).
Friedrich Bessel (Wiki) measures the parallax of 61 Cygni (Wiki: RA 21h 06m 53.9434s, Dec +38° 44′ 57.898″ Note the declination) using a Heliometer (Wiki) which was designed to measure the diameter of the Sun, but also can make precise measurements of angles. Wiki says the Heliometer was better than a filar micrometer (Wiki) in handling atmospheric turbulence (Wiki), I don't understand why. Note the the "seeing" gets worse as the size of the telescope objective gets larger, so for telescopes under 6 inches seeing is not much of a factor, but for scopes over one foot diameter it's a real factor, so for Astrometry (Wiki) you don't want large diameter telescopes. Hence the 4" objective diameter of the Latitude Observatory telescopes.1845
James Clark Maxwell (Wiki) publishes his equations (Wiki) that describe electromagnetic radiation and treat light as a wave. The speed of light can be calculated from the permittivity (Wiki) and Permeability (Wiki) of the medium the light is traveling through. Since both these numbers were known for a vacuum the speed of light was calculated and checked against the then known value and it matched.1887
But there was a debate about the nature of light, was it a particle or a wave and there were experiments that gave both answers.
The Michelson–Morley experiment (Wiki) is published. They were trying to measure the speed of light in the aether (Wiki) but failed. They published their negative result (this takes a lot of guts to stand up and say you were wrong, even today).
Getting the constant of aberration to better than an arc second was critical. Also note the use of observatories at 35o 16' north and south to measure zenith distances. Note this is tied up with measuring the speed of light. It was not yet clear if light was a wave or particle. [Ref 3]
Dr. Kiistner reports a problem in that the latitude of his observatory is changing. [Ref 2]
Albert Einstein publishes the Special Theory of Relativity (Wiki: History, TOR)
1. Optics by Eugene Hect & Alfred Zajac, 1974, ISBN: 0-201-02835-2 - used for the Time Line
2. Progress of Astronomy by William C. Winlock, Annual Report of the Board of Regents of the Smithsonian Institution, July 1890
3. Annual Report of the Board of Regents of the Smithsonian Institution, July 1889
Michelson's Recent Researches on Light by Joseph Lovering pg 449 (Wiki) - Talks about various ways the speed of light had been measured. Michelson's early experiments used a revolving mirror, but had a flaw. The final experiment was done using a interferometer (Wiki).4. Annual Report of the Board of Regents of the Smithsonian Institution, July 1894 - contains a number of inetesting articles
"As late as 1872, Le Verrier thought that a new measurement of tbe velocity of light by Fizeau very important in tbe interest of astronomy; and in 1871, Cornu wrote that tbe parallllx of the sun, and hence the size of the earth's orbit, were not yet known with the desirable precision. In 1875, Villarceau made a communication to the Paris Academy on the theory of aberration. He says that the parallax of tbe sun by astronomical measurement is 8".86. Foucault's velocity of light combined with Struve's aberration makes the sun's parallax 8".86. Cornu's velocity of light gives the same result only when it is combined with Bradley's aberration, which differs from that of Struve by 0".20. Villarceau thinks that there is an uncertainty about the value of aberration on account of the motion of the solar system. 'In 1883, M. O. Struve discussed seven series of observations made by his father, Nyren, and others, with various instruments and by different methods, at the Observatory of Pulkowa. He was certain that the mean result for the value of aberration was 20".492, with a probable error of less than 1/100 of a second. This aberration, combined with the velocity of light as deduced from the experiments of Cornu aud Michelson, made the parallax of the sun 8".784; differing from the most exact results of the geometric method by only a few hundredths of a second. Villarceau proposed to get the solar motion by aberration; selecting two places on the earth in latitude 35o 16' north and south, and after the example of Struve, observing the zenith distances of stars near the zenith. The tangents of these latitudes are ± 1/SQRT(2) so tbat they contain the best stations for obtaining the constant of aberration, and the three components of the motion of translation of the solar system."
The article on pg 749 Geographical Latitude by Walter B. Scaife is about the non ideal characteristics of the Earth, not about a problem measuring precise values.
PS. There's an article about a tower by a guy named G. Eiffel and another by W.A. Eddy. 984 feet (300 meters) tall compared to the Washington monument at 555 feet.
On the Magnitude of the Solar System by William Harkness pg 93- luminiferous ether is mentioned as are the parallax of the Sun & Moon. Says 1639 was the introduction of the micrometer eyepiece. Angle measurements to better than 0".1 are needed for the parallax measurements.
Variation of Latitude by J.K. Rees, pg 271 -
"This was the state of the investigation when Dr. Kiistner, of the Berlin Observatory, published the results of his observations made in 1884-85. Dr. Kiistner undertook some observations for the trial of a new method for the determination of the constant of aberration. On reducing his observations he obtained resnlts which were not at all satisfactory. A careful examination of his work led him to make the announcement that the unsatisfactory valne for the aberration constant was due to a comparatively rapid, though very small, change in the latitude of the Berlin Observatory-" that from Augnst to November, 1884, the latitude of Berlin had been from 0.2" to 0.3" greater than from March to May in 1884 and 1885."
"The lecturer threw on the screen illustrations of several forms of zenith telescopes, and described the new form made by Wanschaft; of Berlin."
Flickr - survey
marker photos -