Batch Preprocessing script documentation?

[jmtanous]

Hi,

Is there any documentation or thread describing how the Batch Preprocessing script creates the master calibration frames?

For instance I am interested in the normalization used for flats, bias and darks before combining them. I am also interested to see if the darks and flats are bias calibrated before combining them. From the script interface is impossible figure this out.

I've tried to search this answers using google and digging the forum with no luck.

Cheers,

Jose

[Juan Conejero]

Hi Jose,

the normalization used for flats, bias and darks before combining them.

Light frames:
output normalization = additive + scaling
rejection normalization = scale + zero offset
scale estimator = iterative k-sigma / biweight midvariance (IKSS)

Flat frames:
output normalization = multiplicative
rejection normalization = equalize fluxes
scale estimator = iterative k-sigma / biweight midvariance (IKSS)

Bias and dark frames:
output normalization = none
rejection normalization = none
scale estimator = median absolute deviation from the median (MAD)

if the darks and flats are bias calibrated before combining them

The generated master dark frames include the bias signal. If you use externally generated master dark frames, they must include the bias signal.

The generated master flat frames do not include the bias signal, since each individual flat frame is calibrated independently, and hence bias-subtracted. If you use externally generated master flat frames, they must not include the bias signal.

Let me know if you need more information.

[jmtanous]

Cristal clear!

Just to double check. If I select 'Optimize dark frames', internally the script subtracts the master bias to the master dark and then uses this new master_dark_minus_bias to scale it and calibrate the lights right?

Muchas gracias Juan!

Saludos,

Jose

[Juan Conejero]

You're welcome Jose.

If I select 'Optimize dark frames', internally the script subtracts the master bias to the master dark and then uses this new master_dark_minus_bias to scale it and calibrate the lights right?

That's how it works exactly. Actually, the master bias is always subtracted (internally) from the master dark for calibration of flat and light frames, even if dark scaling is disabled. Otherwise we'd be subtracting the bias signal twice.

[jerryyyyy]

FYI, am a 6-months users and still using the same bias, flats and darks created when I started up...

[andyo]

So when using master calibration frames that have been created using the BPS previously should you still use a master bias

[jerryyyyy]

I use the Preprocessing Script with 1. Bias, 2. Darks and 3. Flats for the filters I used and the 4. Lights of the actual photos.  If you fit the pieces into this script you cannot go wrong (I think).