24 maja 2007Joanna Falzmann Algorithm for automatic estimation of measurements quality 1 Pi of the Sky Algorithm for automatic estimation of quality of

24 maja 2007 Joanna Falzmann Algorithm for automatic estimation of measurements quality 1

Pi of the SkyPi of the Sky

AlgorithmAlgorithm for for automatic estimation of automatic estimation of quality of quality of measurementsmeasurements

Joanna Falzmann UKSW


Pi of the SkyPi of the Sky

Searching for optical flashes of astronomical origin

Every night thousands of pictures (frames) are taken

All data goes to the huge database

Part of this data has low quality. It’s caused by clouds, full moon…


Division into fieldsDivision into fields

Sky has been divided into fields

Astronomical coordinates gives name for each field (Right Ascention and Declination)

Example: 0800+20 Ra= 08h 00m Dec=20

600 fields in database

About 500 was observed at least once


Number of visible starsNumber of visible stars

Each field has characteristic number of stars on it

If we know this number we can use it for estimation of quality of fames

Plot of the number of stars on each field is automatically created every night


Clouds and High MoonClouds and High Moon

Clouds

Sun sets

Good data

Sun raises


Example of good dataExample of good data

Good data

Sun sets

Good data Sun

raises


Clouds and High MoonClouds and High Moon

System sees less stars that it is there

We need to build an automatic tool to select bad and good frames

Associate a „quality measure” to each frame


Building an algorithmBuilding an algorithm

Finding all interesting data for each field

Number of measurements greater than 10

Creating histograms for all fields fo all nights

Analizing the histograms

Inserting characteristic number of stars to database


HistogramsHistograms

Some histograms are regular – we can fit one gauss


Histograms – one gauss Histograms – one gauss


Information to the databaseInformation to the database

About 50 fields in 500 of all has this regularity

Info about mean value and sigma to the database


Histograms – two gaussesHistograms – two gausses

Some histograms show two gausses


Histograms – two gaussesHistograms – two gausses


Strange eventsStrange events


InvestigationInvestigation

Histograms of about 150 fields in 500 of all are useless

We need to collect more data

For the rest we have to investigate why they have two (or more) gausses structure


CriteriaCriteria

Changing criteria

More than 30 measurements of the field during one night

Cut observations from begin and end of the night

Cut measurements with full moon


ImplementationImplementation

Sipmle algorithm wich will give number for each frame:

Frames with number of stars equal mean value - sigma – very good

Frames with mean value – 1 to 2.5 sigma – acceptable, but suspicious

Discard the rest

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24 maja 2007Joanna Falzmann Algorithm for automatic estimation of measurements quality 1 Pi of the Sky Algorithm for automatic estimation of quality of