[evlatests] Calibrating 3-bit data

[Claire Chandler]

I agree with Bryan.  We have to have recommendations based on documented 
results obtained using typing observing procedures before any of these 
statements should be made within earshot of a user.

Claire

On Mon, 30 Jan 2012, Bryan Butler wrote:

>
> it'd be nice to have that documented properly, to avoid 'lore' building
> up around it.  'a few %' vs. '5 %' vs. '10 %', at which bands, under
> which conditions, etc.  problem is, you start telling observers they can
> get to 'a few %' accuracy without observing a flux density scale
> calibrator, and they'll believe you, and could get bit by it.  so, i
> suggest a memo, author list dhawan and perley.  ;).
>
> 	-bryan
>
>
> Rick Perley wrote, On 1/30/12 8:37 AM:
>> Vivek's statement arises from the AIPS calibration corrections
>> ('CALIB'), on data which have been corrected by the switched power
>> tables. He and I have always noted that these correction factors are
>> within a few percent of 1.0, where 'a few' is typically 5%. (There are
>> usually a few antennas which are quite deviant -- usually due to
>> problems in the SY tables). It's certainly true that the high
>> frequencies are worse, but that's easy to explain in terms of
>> extraordinary atmospheric absorption, bad pointing, winds, etc.
>> If you have trouble accepting these statements, I have some 'flux
>> density' data you can try this out yourself ...
>>
>> Rick
>>
>> Bryan Butler wrote:
>>> i've never seen a definitive, and *repeated*, demonstration of this.
>>> i'd guess it's more like 10% at best, on average (you might get lucky
>>> and get better on occasion). at least at K-band and above. it might be
>>> slightly better at the lower bands. maybe you have data that shows it,
>>> but i'd like to see it.
>>>
>>> -bryan
>>>
>>>
>>> Vivek Dhawan wrote, On 1/29/12 17:34 PM:
>>>> The 8-bit data have been shown to calibrate to
>>>> a few %, compared to the classic method with 3C286 etc.
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