Quality Control and
Data Processing

HC PLOTS
photometric STD zeropoint
photometric STD peak counts
QC1 database (advanced users): browse | plot

NACO acquires photometric standard stars during night time as part of the calibration plan. Five frames of a single star are taken with larger offsets, that the star shows up in ech detetcor quadrant once. The observation migth be repeated for another filter or camera setup. The dedicated pipeline recipe "naco_img_zpoint" builds 8 difference frames from those 5 input frames, rejects the minimum and maximum, and takes median of the remaining 6 zero points values. The subtraction pattern is: #1-#2, #2-#1, #2-#3, #3-#2, #3-#4, #4-3, #4-#5, #5-#4. The conversion formula from ADUs to magnitudes is:

zmag = mag + 2.5 log10(flux/DIT)

where "zmag" is the computed zero point, "mag" is the known magnitude of the standard star in the observed band, "flux" is the flux measured in ADUs in the image and "DIT" is the detector integration time. Note that the zeropoints do neither include extinction nor color correction.

This is an example of a pipeline product of the "naco_img_zpoint" recipe. From the sample of five raw frames, several difference images from consecutive frames are generated.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.ZPOINT	naco_zp..zpoint	photometric zeropoint	CAL		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

Photometric standard stars are only acquired in nights with science observations.

Scoring&thresholds Photometric zeropoint

This QC parameter is not scored.

History

Date	event
2003-2015-06	HC plots for zeropoints and peak counts contain data for camera S27
since_2015-06	HC plots for zeropoints contain data for S13, since the camera wheel was stuck from 2015-06 until 2015-12.
2015	NACO is equipped with a new detector
2015	the upper right detector quadrant (only this quadrant) shows a defect: every 8th column is dead (no response).
2015-06	for the S13 camera: As a consequence, the photometric standard star raw frame, which shows the star in the upper right quadrant is excluded when calculating the photometric zeropoint. Meaning one (frame #2) of five raw frames generated by the template is ignored.
2015-12	the lower left detector quadrant (only this quadrant) shows the 8th column effect. As a consequence, the photometric standard star raw frame, which shows the star in the lower left quadrant is excluded when calculating the photometric zeropoint. Meaning one (frame #4) of five raw frames generated by the template is ignored.

Algorithm Photometric zeropoint

Build eight difference frames from (usually five) consecutive frames to subtract the sky. Find the object at the expected position and apply aperture photometry. No extinction and no color correction is applied.