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Observing Sun Spots
(Team A: Amrit Putcha, Anubhav Prakash, Amna Rayan)
We are a group of students currently engaged in observation and analysis of solar surface phenomena in the visible spectrum.
By means of a DSLR (or/and Dobsonian telescope, 9” aperture) with a 300 mm lens along with ND5 Solar filter, we capture raw images (approx. 1000) of Sun during daytime, mostly around noon, and then process the images to produce a final single “.tiff” image. The final processed image allows us to see the darker and brighter regions (in visible spectrum) of the sun, especially the darker ones, called sunspots.
Sunspots are regions with a high magnetic field on the surface which reduces the amount of light coming from those regions. Thus, when seen through a solar filter, these regions appear as black spots on the solar surface.
Sunspots usually appear in active regions of the sun. The active regions of the suns are labelled by a name in the format, “AR XXXX”, where the X’s are 4 digit number which indicate the order in which the active regions appeared. So, an active region named “AR3490”, was observed before “AR3489”. This naming convention is used worldwide; hence we too have adapted this naming convention. A single active region can have multiple sunspots, and sunspots, being a dynamical feature of the solar surface, can merge or split into two or more. Hence, the number of sunspots in a single active region varies with time. But all the sunspots in the single active region are referred to by the name of the active region.
Sunspots may be considered as markers on the solar surface, which is otherwise almost the same all across its surface as observed with commercial telescopes in the visible region. Their coordinates on the solar sphere doesn’t change appreciably with time, hence as the sun rotates (the fact that sun rotates can be proved by observing the motion of sun spots across the visible side of the sun), the sun spot moves, and this allows us to know the rotation rate of the sun, and also know that the sun undergoes differential rotations (as it isn’t a solid sphere), i.e., different latitude of sun rotates at a different rate.
We intend to create a database on daily solar images (final processed and raw images) and make it open access for anyone and everyone to analyse based on their own interest. We have a team who does the processing and analysis of the images. As of now, we have collected around 2 months of data and created a daily sun image repository which has daily images of the sun of around the past 2 months. Based on our observations till now, we confirmed the statistical fact that sunspots usually form in latitudes between 30 deg - 45 deg north and south of the equator.
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Example of a stacked Image of Sun
An example of a stacked image taken by the Telescope is shown here. It is an outcome of processing (stacking and improving aesthetics in photoshop) 379 raw images. The raw images contain noise because of external (atmospheric), and internal (dust specks on the mirror, thermal noise of sensor) factors which are removed to a certain extent in the stacking process resulting in an improved image with higher Signal to Noise ratio.
We plan to monitor Sunspots continuously over long time-scales. As part of this activity, another team (Team B) has started monitoring the Sunspots. Team B is made up of Amna Rayan, Snega, Jehu, Aadyot, Aquil and Nidhi.
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