Although John Spencer sent this only to people who had contacted him
previously, there is undoubtedly more interest in these filters.
				MA, 93/12/22

Greetings:

I'm sending this to everyone who has so far expressed interest to me
about buying filters for the comet crash, and to various observatories
with infrared cameras.  After I get feedback, I will distribute it more
widely in the hopes of getting more people interested.

Below is a list of possibly useful filters, most of which have been
specifically requested by at least one person.  I've also had 5 or 6
inquiries that didn't specify wavelengths, 3 inquiries for unspecified
CCD wavelengths, and 2 inquiries for unspecified NICMOS wavelengths.
I've had very few inquiries for filters beyond 2.5 microns, though
good things can be done there: the H3+ aurorae are easy to image near
3.4 microns, and the satellite flash reflections may be much brighter
in the 3 - 5 micron region than at shorter wavelengths.  So it's not
to late to ask for these longer wavelength filters.  Glenn Orton
will handle filters in the 10 and 20 micron windows, though-
contact him if you are interested in these.

Most interest has been in methane band filters.  These have two
purposes: 

(i) Supressing Jupiter light to look at satellite flashes, or to look
at the comet or other phenomena near Jupiter.  Filters for this purpose
might need to be fairly wide, while remaining in the methane band, for
maximising throughput for detection of faint phenomena.  WARNING:  use
of methane filters to look for flash reflections on satellites may also
supress the flash itself, which must pass through methane in Jupiter's
atmosphere before reaching the satellite.  Use continuum filters if you 
can, though for flashes of faint satellites this probably isn't an
option.

(ii) Probing the highest levels in Jupiter's atmosphere, in order to
look for high-altitude phenomena.  For this, narrow filters centered
on the peak absorption are probably best.

I have therefore sometimes specified both broad and narrow filters
for the same CH4 band in the list below.

Sometimes appropriate filters are already available commercially, at great
savings over custom-made ones.  I've checked the Optical Coating Lab.
(OCLI) catalog for suitable infrared filters: these are only $260
each, but they are rarely ideal.  I'm interested in other sources of
pre-made filters, especially in the optical.

I hope we can submit orders not long after the New Year.  Typical
lead time for custom filters is a month or two.

WHAT I'D LIKE YOU TO DO:
-------------------------

* Look at the list of filters, and tell me how many of each item you are
  interested in, also what size you need.  This isn't a commitment yet,
  just to give me a better idea.  To be as unambiguous as possible, 
  I've given each filter a letter designation which you can refer to.

* If you want a filter that's not on the list, tell me that also, and
 be as specific as you can about specifications and purpose.  Maybe
 other people out there would also want that filter.

* Question marks in the list, and the list of questions at the end,
 indicate where I'm not sure what a filter is for or have some other
 uncertainty: if you can help me out, please do so.

* If you know of other sources of pre-made "stock" filters, especially
  in the CCD range, let me know!

-----------------------------------------------------------------------------
Desig-  Wave-                      Number   Equivalent OCLI standard filter?
nation  length   Purpose          Requested  (1" circular unless specified)
-----------------------------------------------------------------------------

CCD ( < 1 micron) :

 CA Standard B                         1
 CB 6563 +/- 15  H-alpha               2
 CC 6199 +/- 20  H2O+                  2
 CD Standard R                         1
 CE 7270 +/- 10  CH4  (IJW)            2
 CF 7500 +/- 25  Continuum (IJW)       4
 CG 8290 +/- 25  Continuum?? (IJW)     1
 CH 8930 +/- 25  CH4 (IJW)             5
 CI 8900 +/- 150 CH4, wide           < 8
             (for near-Jupiter)

NICMOS (1 - 2.5 microns) :

 NA 1.15 +/- ??    CH4  ??             1
 NB 1.50 +/- 0.025  NH3                1  N01480-6, 1.480 +/- 0.035  
                                          Probably won't work.  1 available.
 NC 1.58 +/- 0.005  Continuum          6  NO1555-7, 1.555 +/- 0.005 
                                          (needs blocking beyond 1.8 microns!)
 ND 1.70 +/- 0.025  CH4                3  
 NE 2.11 +/- 0.025  H2                 3  NO2151-6, 2.151 +/- 0.095   
                                          Maybe too wide??
                                          N02153-8A, 2.153 +/- 0.05 
                                         (0.15" square, only 3 available).
 NF 2.30 +/- 0.100  CH4,               1  W02288-7, 2.288 +/- 0.18 
              (for near-Jupiter)          (works well in OSIRIS camera!)  
 NG 2.35 +/- 0.03   CH4, (minimum      1  N2355-6X, 2.355 +/- 0.04
              reflectance)                (1.07" diameter, only 1 available).

INSB ONLY (2.5-5 microns):

 IA 3.4  +/- ??    H3+ Aurora?         0  Many OCLI filters available here
    Others ?                           0

LONGER WAVELENGTHS: (GLENN ORTON WILL PROBABLY COORDINATE THESE)

10 micron region   Goddard?
17.2 +/- ??    Temperature sounding, ortho/para 1
24.5 +/- ??                                     1
--------------------------------------------------------------------------

Questions:  

What's the use of multiple CH4 bands?  (good for near-Jupiter,
maybe, but for Jupiter itself??)

Are filters in the wings of CH4 bands useful for imaging intermediate 
atmospheric levels?

Is there interest in or possbility of imaging H3+ aurorae in the c. 2.1 
micron region ??

What are good sources of "standard B, R, filters?  
Only one person has expressed interest in these...