I was visiting this website- http://crest.iiap.res.in/iaonightcam.html, where there was a picture of the night sky coming live from a Telescope. My question is, why is there so many stars in this central circular area, while so few at the other regions? What is this circular region?

Anybody with some experience with telescopes might be able to help...

enter image description here

My explanations:

1) Since the aperture of a telescope is circular, the circular bright area is the place the telescope is really looking at. The rest region is nothing but some play of light, e.i. reflection of the original image on the interior of the telescope, etc.

2) Maybe the telescope is looking at a very small portion of the sky, so this central area is some dense cluster of stars otherwise not visible through naked eye.

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    $\begingroup$ The instrument is an all sky imager. The dense circular region with lots of stars is the sky. The rest of the frame is noise, artifact or an artistic background for the real data (if it is real) $\endgroup$ – Conrad Turner Jul 21 '15 at 21:32

The image is that of the entire sky above the telescope taken with some kind of fish-eye lens. It is quite common at observatories to use such arrangements to monitor for cloud cover.

However you seem to have found a particularly poor example - possibly using a CCD imager with very few pixels. It is also possible that there is some light cirrus over the sky, which if illuminated by the moon can look very bright. It looks to me like the moon could be present behind some cloud top left.

However, it must be quite light cirrus because you can clearly see the milky way running through the centre of the image.

The rest of the image outside the bright circular regions is not sky - it is either the ground or the camera housing.

Here is a better example to look at - the live feed from the ConCam all sky imager at the Roque de los Muchachos observatory on La Palma.

Below is a current still from the camera.

ConCam picture from Roque de los Muchachos


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