Specify the geopotential location for the position against which to estimate the analemma. In this example, this location is the latitude, longitude, and altitude for the Royal Observatory at Greenwich (51.48 degrees North, 0.0015 degrees West, 0 meters altitude).
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Do you know that over 4400 people have scaled Mount Everest? Compare this number with the barely thirty people who have ever successfully captured an analemma of the sun. Do you want to join this elite club? Read on......
Proper planning, technical skill, methodical execution and patience are the keys to a successful analemma attempt. Remember, the endeavor takes a full year to complete and each and every exposure with the camera requires a series of very precise steps to get it just right.
First decide how many exposures you would like to capture over the whole year. I have seen analemmas with upto 52 exposures (one per week) on the internet. Remember however, that you will have to manually set up your camera/ filters/ tripod/ timing etc. for every one of these shots, so my advice is not to be over ambitious. I went with a more conservative 26 exposures (one per fortnight) but as you can see from my image, there are significant gaps in the figure-of-eight. This was because of the Indian monsoon clouds obscuring the sun for weeks at a time.
You could use just about any camera for your analemma adventure. Ideally it would be better to use a camera with manual exposure settings like a DSLR. According to this compilation of analemma captures, in all of human history, only 6 successful attempts have been made using a SLR camera on a single frame of film.
Use a program like Stellarium to note down the extremities of the altitude and azimuth of the sun (at your chosen time of exposure) on Jun 21/22 and Dec 21. Now use a compass to estimate the central azimuth line on your foreground of choice. Basically make sure you choose your transit points and foreground so that the COMPLETEanalemma will appear well within the field of view of your camera. Use the diagram and formula above to estimate your camera's Field of View (FOV). Make sure that once your camera is aligned perfectly to your transit points, it will be able to "see" the sun throughout the whole year.
I cannot stress this enough -> Proper alignment is the MOST important factor to get right while photographing an analemma. Half a degree of alignment error (just a nudge of the tripod) would be equivalent to a timing error of no less than 30 seconds. This is why I recommend the alignment be carried out using two permanent foreground structures in line (also called a transit) with each other.
The transit points are critical to an accurate imaging sequence. Select your transit points carefully within whatever foreground image you want to overlay over the analemma. I made the mistake of choosing points near some mango trees and you can see from the picture above that the mango tree actually grew tall enough over the year to obscure my transit. Not good. Select you foreground composition and transit points carefully.
The only thing to remember is that you should select and photograph the foreground in such a way so that no part of the foreground image obscures the images of the sun that comprise the analemma sequence.
Because the images were taken on a rover, the direction the camera was pointing (North, South, East, etc.) changed frequently. The images have been processed (perspective transform + rotation) such that this change in direction has been largely eliminated. However, the fact that the rover is still moving (and tilting) from image to image and that the image isn't taken exactly at 12:00:00 each sol, leads to a slightly 'noisy' analemma.
The position of the sun is an afterthought for most, unless it is blinding you on your commute home. However, the position of the sun remains incredibly important, even in the modern age. While solar navigation through sextants was common until GPS came along, architects/engineers still track the sun for building shading and solar panel optimization. This script dives into the "analemma" which is an interesting phenomenon associated with solar observations. Try testing different latitudes to see how the sun's trajectory changes and what the analemma looks like!
Grandjean de Fouchy had the idea to incorporate the equation of time in the calculation of an analemma in a sundial, giving it a figure of eight. This essential invention made it possible since 1730 to read directly on such sundials mean solar time, and later by extension Universal Time. 2ff7e9595c
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