Features in the Gallery: Who’s the culprit?

This image below (from 2014-01-19) isn’t a mystery. We’re seeing a bright star through some secondary optical path. The star is out of focus — as secondary images normally are — and we see shadows from the optical and support structures.

Recent Gallery Image

Can we tell what star it is? The nearest really bright star is Spica, which has coordinates (in decimal degrees) of about (RA,Dec)=(201.298,-11.161). This image is centered at (200.01,-9.356). That’s 2 degrees, a pretty long way away–maybe 4000 pixels in the image. But the DSS plates from which these data are taken are a full 6 degrees on a side, so Spica could be in the field of view.

In fact if we look at the plate that seems to enclose this location (labeled s719), it has a center at (200.658,-10.261). That’s just about the center of the two locations. It’s pretty common that there will be an artifact at a location like this with some kind of symmetry with the real location. So Spica it is. Sometimes the obvious answer is the right one.

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One Response to Features in the Gallery: Who’s the culprit?

  1. Hamal says:

    I had always thought that this particular kind of images was not any other thing than that which has been explained here by this photo. It’s not just this group or kind of images which is really interestying at all, just a reflection which is not the virtual image of a star. But never mind what this is in the end, ’cause this object is really unworthy.
    Even though, this explantion keeps on being much appreciated.
    Thank you.

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