Subject: 3.5m throughput

From: Chris Stubbs

Submitted: Sun, 20 Oct 96 00:23:52 -0700

Message number: 99 (previous: 98, next: 100 up: Index)

Dear colleagues,

We have made a rough measurement of the throughput of the 3.5m, using
the Seaver Prototype Imaging camera (SPIcam).  A object with
R=20 produces about 120 e/sec in the thinned SITe detector.

Using the vendor's characterization of the chip's QE, and the 
site's posted filter transmission curve, and assuming each
of the three mirrors reflects 80% of the light, we only
see about 56% of the light I compute we should see in the 
focal plane.  

One of the assumptions above must be incorrect, or I 
have made an error (or both!).  
I think it most likely that the mirror performance is 
the culprit.  Note that we are planning to realuminize the 
mirrors in december.

A more detailed writeup is available off my homepage, 
http://www.phys.washington.edu/~stubbs/

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