Verify apcor parameters being passed to photometry calculations

[drusk]

@ijiraq I found a note to myself to check with you about the apcor parameters being passed to daophot.py. Maybe you can take a quick look, specifically at the swidth property of the ApcorData class in https://github.com/drusk/MOP/blob/master/src/ossos-pipeline/ossos/gui/image.py

I did it this way based on our e-mail conversations while you were away, in which you said apcor files have the following format:

ap_in ap_out apcor apcor_err
numbers like
4 10 0.4 0.05
are normal.

ap == ap_in
insky == ap_out+1
outsky == insky + ap_in

You then also said:

swidth = outsky - insky (if you look through the dophot.pl script there is likely a line someplace that says: outsky = ousky - insky ... poor choice of variable names).

Therefore I calculated that swidth = insky + ap_in - insky = ap_in.
But then swidth == aperature ❓ (both get passed to daophot)

Did I misinterpret something? If you can do a quick review of this it would be good.

[ijiraq]

nominally swidth = aperture , that is correct. But not required for dophot.pl to return a correct result.

swidth can be selected as a different value than aperture and a valid value will be measured. swidth=aperture is a handy rule-of-thumb for doing photometry which works for our typical fields and source type. Your code looks correct and calls to phot need to pass both values, ossos pipeline just chooses to use the same value for both.

Keeping the 'swidth' and 'aperture' as separate attributes is a good design choice as the choice of making them equal could be changed during evaluation of the pipelines performance.

JJ

On 2013-07-03, at 3:30 PM, David Rusk wrote:

@ijiraq I found a note to myself to check with you about the apcor parameters being passed to daophot.py. Maybe you can take a quick look, specifically at the swidth property of the ApcorData class in https://github.com/drusk/MOP/blob/master/src/ossos-pipeline/ossos/gui/image.py

I did it this way based on our e-mail conversations while you were away, in which you said apcor files have the following format:

ap_in ap_out apcor apcor_err
numbers like
4 10 0.4 0.05
are normal.

ap == ap_in
insky == ap_out+1
outsky == insky + ap_in

You then also said:

swidth = outsky - insky (if you look through the dophot.pl script there is likely a line someplace that says: outsky = ousky - insky ... poor choice of variable names).

Therefore I calculated that swidth = insky + ap_in - insky = ap_in.

But then swidth == aperature (both get passed to daophot)

Did I misinterpret something? If you can do a quick review of this it would be good.

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