[mmaimcal]Primary Beam Accuracy

[Mark Holdaway]

> Hi Mark,
>   a couple quick questions on things that weren't clear to me.  Since 
> I follow this e-mail group only sporadically, I thought I'd just ask you,
> hoping you wouldn't mind too much...
> 
>   From my reading, you're assuming an error in the PB model which is
> identical for all antennas.  I would think that mis-measurements (and
> inaccuracies in the dish surfaces) would quite likely be in error by
> different amounts for the different dishes, apart from systematic 
> "droops" at low elevations etc.  Am I right in thinking your limits apply
> to systematic average errors, and the restrictions on uncorrelated 
> problems are much less severe?

Yes, this analysis applies to systematic errors.

>   The other question is one of consistency.  One can presumably think of
> pointing errors as particularly severe & systematic errors in the assumed
> primary beam; presumably the error at a given radius is something like
> the gradient of the PB at that point, and the opposite on the other side.
> You've done a lot of work on the influence of pointing errors -- do the
> ballpark figures derived here agree roughly with those results?  If so 
> that might give you a bit more confidence in the ballpark estimates 
> derived here.

Good point, I'll look into this as a check.

>   Feel free to pass this along to the mmaimcal group if you think it's
> worthwhile.

Done, thanks for the comments; this is exactly the sort of thing I
was looking for, a reality check on my idea and work.

>   Cheerio,
>           Michael

Fruit Loops,
	-Mark