SUN _ Astrosolar Foto Film O.D.3.8 (Didier FOURNIL)

SUN _ Astrosolar Foto Film O.D.3.8

Technicals Informations: ------------------------------------------------------------------------------------------

Capture Area: 3520x3520

Gain/82

Exposure: 3.8E-05

300 frames kept on a video of 2500

The Problem raised of this attempt: ---------------------------------------------------------------------------

Commonly, the sun is photographed in Ha using instruments with diameters ranging from 40 (Coronado ST40) to 80mm (Lunt ST80)
It appears on the photographs obtained a kind of texture, which was quickly identified as the granulation of the sun. But is that really possible?

Because if we take a closer look, the famous formula for calculating the resolution of an instrument R=0.252 X λ/ Ø , tells us that the maximum resolution of these instruments does not exceed 3.46' for a diameter of 40mm (Coronado) or 1.73' for a diameter of 80 (Lunt ST80)
However, the angular average of the granules is around 1 second of arc...
In theory (Always according to our formula of calculation of resolution) it would be necessary a diameter of the order of 120 mm in order to be able to begin to see the granules, and this, to speak only of the problem of resolution of the instrument! (The SEEING, altitude and collimation of the instrument are also to be taken into account).

So, the purpose of this test is to try to reveal this solar granulation by benefiting from the resolution of an instrument of 200mm diaphragm to 170mm by a filter Astrosolar Foto Film O.D.3,8

The fact remains that this first test is carried out in plain, where SEEING still limits enormously the power of resolution of the instruments.

Also, other tests are planned very soon in altitude (2000m)

For more explanations on the resolution of solar granules, see my article on:

http://astrocoach60.blogspot.com/

In French, sorry...

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