A Primer on Image Acquisition A Primer on Image Acquisition and Data Reduction Using and Data Reduction Using TheSky6, CCDSoft V5 and TheSky6, CCDSoft V5 and

Microsoft ExcelMicrosoft Excel

Thomas C. SmithThomas C. Smith

Dark Ridge Observatory Dark Ridge Observatory ((DRODRO))

http://www.darkridgeobservatory.orghttp://www.darkridgeobservatory.org

Topics of ConversationTopics of Conversation

OverviewOverview Tools for the jobTools for the job Taking imagesTaking images Reducing the image dataReducing the image data Processing and analyzing image dataProcessing and analyzing image data Producing a light curveProducing a light curve SummarySummary Q&AQ&A

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OverviewOverview

Image acquisition and data processing Image acquisition and data processing have a completely different meaning have a completely different meaning when one is attempting to collect and when one is attempting to collect and analyze scientific data as opposed to analyze scientific data as opposed to creating wonderfully colorful and creating wonderfully colorful and enjoyable “pretty pictures”.enjoyable “pretty pictures”.

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Tools for the jobTools for the job

In this brief tutorial I will be using In this brief tutorial I will be using software created by Software Bisque software created by Software Bisque as well as numerous algorithms that I as well as numerous algorithms that I have created in macro form in have created in macro form in Microsoft Excel.Microsoft Excel.

TheSky6 Pro and CCDSoft V5 are the TheSky6 Pro and CCDSoft V5 are the tools that I commonly use for both tools that I commonly use for both image acquisition and data reduction.image acquisition and data reduction.

Lets look at each commercial software Lets look at each commercial software program.program.

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Tools for the jobTools for the jobTheSky6 planetarium softwareTheSky6 planetarium software

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Tools for the jobTools for the jobCCDSoft V5CCDSoft V5

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Tools for the jobTools for the jobMS ExcelMS Excel

Microsoft Excel and the “smiley face” Microsoft Excel and the “smiley face” light curve generation algorithmslight curve generation algorithms

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From data to curve

Taking ImagesTaking Images

Camera startup and cooling Camera startup and cooling Composing the field of viewComposing the field of view Starting auto guidingStarting auto guiding Setting the integration timeSetting the integration time Choosing the filter(s)Choosing the filter(s) Selecting the series countSelecting the series count Setting image storage locationSetting image storage location Imaging and monitoringImaging and monitoring

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Taking imagesTaking imagesCamera startup and coolingCamera startup and cooling

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• Choose the correct CCD camera

• Select the filter wheel (if applicable)

• Select the focuser (if applicable)

• Verify parameters

• Connect to the camera

• Initiate temperature regulation

Taking imagesTaking imagesComposing the field of viewComposing the field of view

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Taking ImagesTaking ImagesStarting auto guidingStarting auto guiding

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Linking TheSky6 to the telescope

Taking ImagesTaking ImagesStarting auto guiding (Cont)Starting auto guiding (Cont)

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Taking ImagesTaking ImagesStarting auto guiding (Cont)Starting auto guiding (Cont)

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Taking ImagesTaking ImagesSetting the integration timeSetting the integration time

Some things to considerSome things to consider Target ADU valueTarget ADU value Sky background (Moon or dark)Sky background (Moon or dark) Set this using the filter of choiceSet this using the filter of choice Image typeImage type Make testsMake tests

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Taking ImagesTaking ImagesChoosing the filtersChoosing the filters

If you are going to image in several filters it is important to If you are going to image in several filters it is important to set the integration times for each filter appropriatelyset the integration times for each filter appropriately

CCDSoft V5 shows only 4 filters but there is good control CCDSoft V5 shows only 4 filters but there is good control over the individual filters and camera binning (all facets of over the individual filters and camera binning (all facets of the filters and imaging can be scripted however to the filters and imaging can be scripted however to overcome this shortfall)overcome this shortfall)

Single filter setup is simpleSingle filter setup is simple

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Taking ImagesTaking ImagesSelecting the series countSelecting the series count

Series counts are set in either the Series counts are set in either the “Take Image” tab or in the “Color” “Take Image” tab or in the “Color” tab.tab.

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Taking ImagesTaking ImagesSetting image storage locationSetting image storage location

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Taking ImagesTaking ImagesImaging and monitoringImaging and monitoring

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Reducing the image dataReducing the image data

Once the image series has been Once the image series has been collected it is time to “reduce” the collected it is time to “reduce” the image files through a series of pixel image files through a series of pixel mathmath Bias framesBias frames Dark framesDark frames Flat field frames w/flat dark framesFlat field frames w/flat dark frames

What are these frames?What are these frames?

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Reducing the image dataReducing the image dataFrames explainedFrames explained

Bias frameBias frame This is effectively a zero second light exposure This is effectively a zero second light exposure

at the same temperature as the science framesat the same temperature as the science frames Dark frameDark frame

This is an exposure that is the same time and This is an exposure that is the same time and temperature as the science frames but with temperature as the science frames but with the shutter closed (or light path covered)the shutter closed (or light path covered)

Flat field frameFlat field frame These are frames that eliminate the pixel-to-These are frames that eliminate the pixel-to-

pixel variations and any optical path pixel variations and any optical path aberrations such as dust and vignettingaberrations such as dust and vignetting

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Processing and analyzing image dataProcessing and analyzing image data

Once the images have been reduced it Once the images have been reduced it is then a matter of finding objects of is then a matter of finding objects of interest in theminterest in them

For this an implementation of For this an implementation of Sextractor is used within the CCDSoft Sextractor is used within the CCDSoft applicationapplication Sextractor is written by Emmanuel Bertin, Sextractor is written by Emmanuel Bertin,

visit visit http://terapix.iap.fr/http://terapix.iap.fr/ for details for details There are many things to learn about There are many things to learn about

Sextractor but I will only be discussing a Sextractor but I will only be discussing a few things of interest few things of interest

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Processing and analyzing image dataProcessing and analyzing image dataSource extraction with CCDSoftSource extraction with CCDSoft

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Processing and analyzing image dataProcessing and analyzing image data Source extraction with CCDSoft (Cont)Source extraction with CCDSoft (Cont)

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Processing and analyzing image dataProcessing and analyzing image dataAstrometry with CCDSoftAstrometry with CCDSoft

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Producing a light curveProducing a light curveSource extraction rollup with CCDSoft (Cont)Source extraction rollup with CCDSoft (Cont)

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Producing a light Producing a light curvecurveStar identificationStar identification

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Producing a light Producing a light curvecurveCCDSoft light curve toolCCDSoft light curve tool

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Microsoft Excel is a powerful tool for Microsoft Excel is a powerful tool for performing various numerical and performing various numerical and data function includingdata function including Statistical analysisStatistical analysis Standard spreadsheet data entryStandard spreadsheet data entry Chart generationChart generation Producing what-if scenariosProducing what-if scenarios And much, much moreAnd much, much more

Producing a light Producing a light curvecurveExcel light curve plottingExcel light curve plotting

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I use the Visual Basic for Applications function and I use the Visual Basic for Applications function and macro tools to process the raw text data files that macro tools to process the raw text data files that are obtained from CCDSoft and to plot the resulting are obtained from CCDSoft and to plot the resulting light curve as I feel appropriatelight curve as I feel appropriate

Full control of the charting environment through VBA Full control of the charting environment through VBA makes reproducing chart characteristics simple and makes reproducing chart characteristics simple and fastfast

I use the power of Excel to identify outlying data I use the power of Excel to identify outlying data through a 3-sigma routinethrough a 3-sigma routine

I can optionally bin the data and create an additional I can optionally bin the data and create an additional curve for contrast with the raw data curve.curve for contrast with the raw data curve.

The entire plotting routine can go from raw data to The entire plotting routine can go from raw data to light curves with significant statistical information light curves with significant statistical information available in just a few momentsavailable in just a few moments

Always being modified and added to for enhanced Always being modified and added to for enhanced performanceperformance

Producing a light curveProducing a light curveExcel light curve plotting (cont)Excel light curve plotting (cont)

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I have created many utility functions that perform I have created many utility functions that perform things such asthings such as Julian Date to Heliocentric Julian date conversionJulian Date to Heliocentric Julian date conversion Filtered image file move routines “triage” to aid in Filtered image file move routines “triage” to aid in

placing the files in the correct folder locations for placing the files in the correct folder locations for analysisanalysis

6 degree to 30 degree air mass calculations as well as 6 degree to 30 degree air mass calculations as well as the common >= 30 degree air mass routinethe common >= 30 degree air mass routine

Routines to bulk update FIT header data from a specified Routines to bulk update FIT header data from a specified folder of image (used when the RA/DEC data is incorrect folder of image (used when the RA/DEC data is incorrect to assist in the astrometric solution)to assist in the astrometric solution)

Many other support utilities that are used both internal Many other support utilities that are used both internal to the light curve plotting routines and callable to the light curve plotting routines and callable externally from most any COM-compliant applicationexternally from most any COM-compliant application

Producing a light curveProducing a light curveExcel light curve plotting (cont)Excel light curve plotting (cont)

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Producing a light curveProducing a light curveExcel light curve plotting (cont)Excel light curve plotting (cont)

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Producing a light curveProducing a light curveExcel light curve plotting (cont)Excel light curve plotting (cont)

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Seeing my “Smiley Face” in action!

SummarySummary Image reduction for science images is very Image reduction for science images is very

different from that used to create “pretty different from that used to create “pretty pictures”pictures”

Many tools can be used and it is normally Many tools can be used and it is normally a matter of familiarity and preferencea matter of familiarity and preference

If things don’t look right then think about If things don’t look right then think about what might be causing the issues and what might be causing the issues and reanalyze the datareanalyze the data

Common desktop tools like Microsoft Excel Common desktop tools like Microsoft Excel make powerful partners in the world of make powerful partners in the world of astronomical photometryastronomical photometry

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Q & AQ & A

Any questions about this process or Any questions about this process or anything in general that you would anything in general that you would

like to ask?like to ask?

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