[fitsbits] EXPOSURE or OBSTIME?

[Tom Kuiper]

> Date: Mon, 5 Jun 2000 10:36:35 -0400
> From: Eric Greisen <egreisen at nrao.edu>
> Cc: fitsbits at nrao.edu
> Subject: Re: [fitsbits] EXPOSURE or OBSTIME?
...
>    Perhaps this is a case for me to recommend the use of a 1-pixel
> axis to specify time, with the axis increment being the integration
> time. 

Dear Eric,

I was about to tell you that the advantage of this isn't obvious to me, that I
couldn't imagine ever wanting to display spectra as a function of time.  Then
I remembered that my thesis was based on dynamic spectra of Type III burst.
More recently, I made a movie of what we thought were short-time fluctuations
in the Orion water maser. (They turned out to be due to time variable
errors in pointing.)  So, I like you idea.  However, there is the issue of
compatibility with other software packages, such as CLASS and COMB.

It also raises the issue that I posed in my other query, which is the difference
between CDELTx and resolution on the x axis, so we'd still need something
like EXPOSURE/OBSTIME.

I'm leaning towards a solution similar to that used at Lick, where they have
both the keywords EXPOSURE and TTIME, which mean the same thing, the latter
being there for backward compatibility. The issue of whether time would
just be a keyword or also an axis variable would then not be contentious.
Do you see a problem with doing both?
> 
>    The VLBA uses INTTIM as a random parameter in a groups UV data set
> and would use the same as a keyword or column label in a UV data
> table.
> 
Does this refer to a case in which the UV samples have been regridded to be
uniform on a time axis?  Otherwise, CDELTx doesn't have any meaning, does it?

Cheers

Tom
--
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