Brooke's Sundial page

In the past the USNO observed stars with the Photographic Zewnith Tube to determine what time it was. This system had an absolute accuracy in the millisecond range. Now they use Very Long Baseline Interferometry (VLBI) to set the time. This is done on a world wide basis. Use the link to the IERS on my Time & Frequency page for more information

Land surveyors have used the Sun to determine a North - South bearing with great accuracy. To do this they need to know their location and very accurate time. This requires special adapters on the surveyor's transit. This process could be used in reverse to determine time.

Pinhole Astrophotography - For the best resolution a pinhole of diameter d (mm) should be 745*(d^2) mm away from the image.

Satellite Sun Blockage

I use Starband for my internet connection. It's a two way satellite based system. At my house there's an orange peel type offset fed dish that has both a receiver and a transmitter. It's very similar to the Ku band receive only satellite TV receiver dish and this idea would work for them also.

Using a 3'x5" card with an elicipse about the same size as the sun's image with a hole in the center to mark the sun's position on the ceiling. And the Starband signal strength window displayed on my computer screen. When the signal gets down to 6.0 (it's normally between 7 and 8.5) one mark is made. Then another at 5.0. A yellow highlighter is used to emphasize the range between 6.0 and 5.0. When the signal gets down to 4.8 my system shuts down totally.

I don't yet understand why the 4 Oct 2004 marks don't line up with the March 2005 marks.
(it very well have been that the mirror got moved!)

All the sun blockage marks are around 12:45 PST in the spring and 1:40 PDT in the fall (and to the left of them is a mark made at 1:00:00. I have added dates to the left of the 1:00:00 line to make them easier to read. For a reason that I don't understand my camera does not want to focus on the ceiling.

On 4 March 2005 I drew the sun's outline to give the diagram some scale. Note that the sun moves it's own diameter in about 2 minutes.

Dipleidoscope

Organizations

Calculations

For Sale

Construction

Photographs

Descriptions

Home Pages

Books

Heliograph

Combines a mirror with Morse code to send messages. Started about 1865. There are two types, one is a hand held instrument like used in the survival kit on a life boat. The other is a typically military communication device used to send Morse messages between stations that are miles apart. The key elements are a mirror or mirrors that can be positioned so as to aim the reflected sun light where you want it and a way to tilt the mirror for sending Morse code.

The signaling mirror that's part of the equipment on a life boat has the front surface all mirror and on the back there's a small centered mirror surrounded with printed instructions. In the center there's a "+" shaped hole in the mirror's silvering. When the mirror is held in front of the face you can see distant objects through the "+" hole and also you can see a "+" shaped image of the sun on your face. When you align the sun's image as seen in the back side mirror with the "+" shaped hole the front of the mirror is reflecting the sun at the center of the "+" opening. This mirror can be tipped to send morse messages, although not as convenient as a normal Morse type key.

It may be possible to modernize the heliograph by using electronics to read the light flashes, and to control the sending mirror.

The Heliotrope is very similar except it has no provision for sending Morse code. Used in surveying to mark a distant point

Patents

Gnomonics

This is the 11383 hits since May 04 2007 time this page has been accessed since 30 Jan. 2000.

Sundials