Thursday, 3 July 2014

Draco Lyra and Ursa, Constellations at Nahargarh-Ampitheater, Jaipur.

Composite photo of 54 Frames stacked (Virtual Tracking)

This (Fin@l) image is a composite of over 50 photographs out of some 140 photos of 30seconds exposure each, taken continuously for over an hour.

The rotation of the earth makes the stars look like they are moving around the North South Axis of earth's rotation.
As a result the stars make small trails in each successive photograph (which if stacked will look like the last image Star Trails), to account for earth's rotation, each successive photo has to be moved a fixed amount Up-Down(Y) and Left-Right(X) and Also Rotate (R). This is what you do when you use a motor-clock driven Tracker Mount for telescopes. Hence 

For Virtual Tracking in  Post-Processing, the RAW(CR2) files were "Registered and Stacked" i.e. each and every star is located (X,Y co-ordinates) with precise brightness and size(in pixels) and the best 80% photos were used make the Semi-Final Image as a 32Bit (High Dynamic Range HDR)Tiff file, note the 32bits part, so the image will look too darkly n flatish on regular LCD/CRT monitors, I used Photoshop to develope the 32bit HDR image as a high Contrast image, which I then "Level" and adjust the colour-Contrast (Curves)

This photograph is a stack of all the photographs about 140, as they came from the camera, or this is how the photograph will look if you take one photograph over 60mins facing the Northern Sky.
The camera is stationary (with respect to earth), as the earth rotates so does the camera, and all the stars look like they are moving, like a person on a ship seeing another ship in high seas.

A map of the Constellation Lines and boundaries with a 120* Field of View. The North Celestial Pole aka, Polaris.

Names of Constellations and Stars(few bright ones!)

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