Subject: New 2 Arcsec DIS Slit

From: Steve Knapp

Submitted: Thu, 18 Jul 1996 15:24:23 -0600

Message number: 20 (previous: 19, next: 21 up: Index)

There is a *newer* 2 arcsec slit for DIS.  Please handle 
with care: this is a fragile first-surface mirror, with no
overcoating.

Using properly machined occulting blocks produced by 
Doug at the NSO machine shop, I have successfully 
aluminized a pretty good 2 arcsec slit on a glass
microscope slide.  This slit will go into Turret A (A1)
today, replacing the "2 arcsec slit" which I made a
few days ago.  The old slit will no longer be available.
The substrate is a glass microscope slide (about 3 x 1 inch)
and the transmission will fall off in the violet (details 
are not known at this time).

Examination of the new 2 arcsec slit reveals the following:

The dimensions of the slit are:

Slit overall length, about 6.32 cm [6.2 arcmin].
Reflecting area, about 7.60 x 2.50 cm [7.4 x 2.5 arcmin].
The slit is not quite centered in the short dimension
of the glass slide.

Slit is nearly rectangular, width measuring
350 microns [2.06 arcsec] near one end,
385 microns [2.27 arcsec] near the center, and
381 microns [2.24 arcsec] at the other end.

Quality:
The glass slide was cleaned more thoroughly and the aluminization
appears more uniform.  There are only a few minor "holes" and other
blemishes in the aluminum; I will welcome feedback from users.  The 
new occulting blocks were very linear:  the worst case of a 
"bump" or "valley" in an edge of the slit near the center
was measured to have an overall amplitude (peak) of 14 microns. 
There are some areas where the edges have a "ripple" with peak-peak 
amplitude of about 7 microns or so.  All in all, the slit is
quite nice to look at.  Finally, the method I am using does not
apodize the edges of the slit, which may not be the 
best strategy in all cases.  I believe that I can extend the method 
to support some controlled apodizing.

As usual, feedback is welcome.

-Steve Knapp
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