comments on SED DM V0.93

Dear Jonathan and Doug,

I finally went through this remarkable work (SED DM v0.93) and have a couple of comments/questions on the following topics:

1. Absolute vs Relative flux
2. Slit shape and position 3a. Astrometric information 3b. Astrometric accuracy 3c. Constant Coverage per "spectrum"?
3. Bandpass
4. UCDs
5. Absolute vs Relative flux

Is there a way to specify whether the Flux is Absolutely calibrated or whether only the shape is correctly known?

I probably remember someone already asking this question, but cannot find it.
Sorry if this was already asked.

2. Slit shape and position

Do I get it right that in this version the only available aperture is circular?
I could not find the place to put the orientation of the slit. Have I missed it?

3a. Astrometric information

Which ones are the "observed" coordinates (RA_NOM,DEC_NOM) or (RA_TARG,DEC_TARG)?
According to the full example of a FITS header it seems to be the latter,
but according to the text in the document it is probably the other one. Also, (8.1 FITS Serialization):
> The Position.Type field is not explicitly serialized; the names
> of the two columns used for Position are used to infer the type
The document should list all the allowed names.

3b. Astrometric accuracy

Have I missed the place to store the errors on the spatial position? The entire "Coverage Fields" section is not listing any error.

3c. Constant Coverage per "spectrum"

The first sentence of (5.1) states:
> The coverage fields will have constant value for a given "spectrum"
It should probably be "segment" instead.

4. Bandpass

For photometric points, the bandpass name is specified in 5.1 Coverage Fields
as Coverage.Location.SpectralCoord.Value (instr.bandpass) to be consistent
with RSM. The fact is that there is no defined list of such bandpasses, hence it is not possible for the analysis software to understand what the band pass really is.

5. UCDs

Non-compliant UCDs
There are some UCDs which, according to the UCD1+ standard, are not allowed
to be Primary words:

(4.2 Spectral Coordinate) instr.pixel;... (4.3 Flux Object) arith.ratio;...

Misleading UCDs
(4.7 Accuracy Fields) The Sky.Resolution UCD is "instr.ang-res" which makes one
think it is not taking into account the seeing. In case the seeing is to be
considered, the UCD should probably be "instr.obsty.site.seeing".

Wrong UCD
(5.1 Coverage Fields) Frame.Time.SIDim UCD is "time;arith.zp" I don't know what should it be instead, maybe a arith.ratio?

THANKS! Alberto

--
Alberto Micol
ST-ECF HST Archive Scientist