Extensive reading for Are the dispersion directions of the prism and the grating in Hubble WFC3 UVIS G280 perpendicular? Can we call this a "grism"? With cross-disparsion? led me to Instrument Science Report WFC3 2003-02; WFC3 UVIS Filters: Measured Throughput and Comparison to Specifications.

Table 1: "UVIS Filter Performance Specifications from Version D JPL Spec or CEI" lists near the bottom

Fnumber  Fname   Lam0   FWHM  lam -50 ... lam +50 ... Description
-------  -----  ------  ----  -------     -------     -----------
UVIS 47  G200   2775.0  1850    1800  ...   3650  ...   UV prism

Question: What is Hubbles WFC3 "UVIS 47 G200" filter? Is it just a prism or is it a combination of a prism and a filter?

What is it used for?

How can I find an example of how it has been used in practice?


1 Answer 1


I believe that is a typo. In Tables 4 and 5 of the same document, "UVIS 47" is listed as "g280", which is the grism you are curious about.

A perusal of several other HST documents (e.g., various Wide Field Camera 3 Instrument Handbooks) turns up no mention of a "G200" element, and searches of the HST archive turn up nothing if "G200" is entered in the "Filter/Grating" field. (Entering "G280" turns up observations with that grism.)

  • 1
    $\begingroup$ nice detective work, thanks! $\endgroup$
    – uhoh
    Oct 15, 2021 at 14:16

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