This night (a true story!), by using my eShel spectrograph, I noticed a
loss of signal by a factor of 4 compared to my last observation. Dramatic!
I noticed this problem immediately by measuring the intensity of the ThAr lines and quickly confirmed by stars observations
The explanation is simple and classic: the presence of dust at the entrance of the 50 microns core fiber. I disassembled
the fiber all night (which is not great ) and despite careful handling, clean is a potential probem.
I quickly identified the problem by carefully cleaning the input of
the fiber entrance with a very soft lens paper. Must rub very gently,
in the direction of the paper fiber.
The resulting was spectacular. I found my original signal (and even better!).
As you can be seen, the cleanliness of the fiber can be a source (sometimes) of efficiency lost.
Christian B
About eShel efficiency
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Re: About eShel efficiency
Maintenant, c'est une situation rare, il faut l'admettre. La probabilité qu'une poussière ce place au mauvais endroit est plutot bien rare. Mais il faut ce méfier. Ca peut aussi concerner la fibre de calibration, même si elle est plus grosse et que c'est moins critique.
Christian
Christian