A Primer on Image Acquisition and Data Reduction Using TheSky6, CCDSoft V5 and Microsoft Excel Thomas C. Smith Dark Ridge Observatory (DRO)

Topics of Conversation Overview Overview Tools for the job Tools for the job Taking images Taking images Reducing the image data Reducing the image data Processing and analyzing image data Processing and analyzing image data Producing a light curve Producing a light curve Summary Summary Q&A Q&A DRO

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

Tools for the job In this brief tutorial I will be using software created by Software Bisque as well as numerous algorithms that I have created in macro form in Microsoft Excel. In this brief tutorial I will be using software created by Software Bisque as well as numerous algorithms that I have created in macro form in Microsoft Excel. TheSky6 Pro and CCDSoft V5 are the tools that I commonly use for both image acquisition and data reduction. TheSky6 Pro and CCDSoft V5 are the tools that I commonly use for both image acquisition and data reduction. Lets look at each commercial software program. Lets look at each commercial software program. DRO

Tools for the job TheSky6 planetarium software DRO

Tools for the job CCDSoft V5 DRO

Tools for the job MS Excel Microsoft Excel and the “smiley face” light curve generation algorithms Microsoft Excel and the “smiley face” light curve generation algorithms DRO From data to curve

Taking Images Camera startup and cooling Camera startup and cooling Composing the field of view Composing the field of view Starting auto guiding Starting auto guiding Setting the integration time Setting the integration time Choosing the filter(s) Choosing the filter(s) Selecting the series count Selecting the series count Setting image storage location Setting image storage location Imaging and monitoring Imaging and monitoring DRO

Taking images Camera startup and cooling DRO 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 images Composing the field of view DRO

Taking Images Starting auto guiding DRO Linking TheSky6 to the telescope

Taking Images Starting auto guiding (Cont) DRO

Taking Images Starting auto guiding (Cont) DRO

Taking Images Setting the integration time Some things to consider Some things to consider Target ADU value Target ADU value Sky background (Moon or dark) Sky background (Moon or dark) Set this using the filter of choice Set this using the filter of choice Image type Image type Make tests Make tests DRO

Taking Images Choosing the filters If you are going to image in several filters it is important to set the integration times for each filter appropriately If you are going to image in several filters it is important to set the integration times for each filter appropriately CCDSoft V5 shows only 4 filters but there is good control over the individual filters and camera binning (all facets of the filters and imaging can be scripted however to overcome this shortfall) CCDSoft V5 shows only 4 filters but there is good control over the individual filters and camera binning (all facets of the filters and imaging can be scripted however to overcome this shortfall) Single filter setup is simple Single filter setup is simple DRO

Taking Images Selecting the series count Series counts are set in either the “Take Image” tab or in the “Color” tab. Series counts are set in either the “Take Image” tab or in the “Color” tab. DRO

Taking Images Setting image storage location DRO

Taking Images Imaging and monitoring DRO

Reducing the image data Once the image series has been collected it is time to “reduce” the image files through a series of pixel math Once the image series has been collected it is time to “reduce” the image files through a series of pixel math Bias frames Bias frames Dark frames Dark frames Flat field frames w/flat dark frames Flat field frames w/flat dark frames What are these frames? What are these frames? DRO

Reducing the image data Frames explained Bias frame Bias frame This is effectively a zero second light exposure at the same temperature as the science frames This is effectively a zero second light exposure at the same temperature as the science frames Dark frame Dark frame This is an exposure that is the same time and temperature as the science frames but with the shutter closed (or light path covered) This is an exposure that is the same time and temperature as the science frames but with the shutter closed (or light path covered) Flat field frame Flat field frame These are frames that eliminate the pixel-to-pixel variations and any optical path aberrations such as dust and vignetting These are frames that eliminate the pixel-to-pixel variations and any optical path aberrations such as dust and vignetting DRO

Processing and analyzing image data Once the images have been reduced it is then a matter of finding objects of interest in them Once the images have been reduced it is then a matter of finding objects of interest in them For this an implementation of Sextractor is used within the CCDSoft application For this an implementation of Sextractor is used within the CCDSoft application Sextractor is written by Emmanuel Bertin, visit for details Sextractor is written by Emmanuel Bertin, visit for details There are many things to learn about Sextractor but I will only be discussing a few things of interest There are many things to learn about Sextractor but I will only be discussing a few things of interest DRO

Processing and analyzing image data Source extraction with CCDSoft DRO

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

Processing and analyzing image data Astrometry with CCDSoft DRO

Producing a light curve Source extraction rollup with CCDSoft (Cont) DRO

Producing a light curve Star identification DRO

Producing a light curve CCDSoft light curve tool DRO

Microsoft Excel is a powerful tool for performing various numerical and data function including Microsoft Excel is a powerful tool for performing various numerical and data function including Statistical analysis Statistical analysis Standard spreadsheet data entry Standard spreadsheet data entry Chart generation Chart generation Producing what-if scenarios Producing what-if scenarios And much, much more And much, much more Producing a light curve Excel light curve plotting DRO

I use the Visual Basic for Applications function and macro tools to process the raw text data files that are obtained from CCDSoft and to plot the resulting light curve as I feel appropriate I use the Visual Basic for Applications function and macro tools to process the raw text data files that are obtained from CCDSoft and to plot the resulting light curve as I feel appropriate Full control of the charting environment through VBA makes reproducing chart characteristics simple and fast Full control of the charting environment through VBA makes reproducing chart characteristics simple and fast I use the power of Excel to identify outlying data through a 3-sigma routine I use the power of Excel to identify outlying data through a 3-sigma routine I can optionally bin the data and create an additional curve for contrast with the raw data curve. I can optionally bin the data and create an additional curve for contrast with the raw data curve. The entire plotting routine can go from raw data to light curves with significant statistical information available in just a few moments The entire plotting routine can go from raw data to light curves with significant statistical information available in just a few moments Always being modified and added to for enhanced performance Always being modified and added to for enhanced performance Producing a light curve Excel light curve plotting (cont) DRO

I have created many utility functions that perform things such as I have created many utility functions that perform things such as Julian Date to Heliocentric Julian date conversion Julian Date to Heliocentric Julian date conversion Filtered image file move routines “triage” to aid in placing the files in the correct folder locations for analysis Filtered image file move routines “triage” to aid in placing the files in the correct folder locations for analysis 6 degree to 30 degree air mass calculations as well as the common >= 30 degree air mass routine 6 degree to 30 degree air mass calculations as well as the common >= 30 degree air mass routine Routines to bulk update FIT header data from a specified folder of image (used when the RA/DEC data is incorrect to assist in the astrometric solution) Routines to bulk update FIT header data from a specified folder of image (used when the RA/DEC data is incorrect to assist in the astrometric solution) Many other support utilities that are used both internal to the light curve plotting routines and callable externally from most any COM-compliant application Many other support utilities that are used both internal to the light curve plotting routines and callable externally from most any COM-compliant application Producing a light curve Excel light curve plotting (cont) DRO

Producing a light curve Excel light curve plotting (cont) DRO

Producing a light curve Excel light curve plotting (cont) DRO Seeing my “Smiley Face” in action!

Summary Image reduction for science images is very different from that used to create “pretty pictures” Image reduction for science images is very different from that used to create “pretty pictures” Many tools can be used and it is normally a matter of familiarity and preference Many tools can be used and it is normally a matter of familiarity and preference If things don’t look right then think about what might be causing the issues and reanalyze the data If things don’t look right then think about what might be causing the issues and reanalyze the data Common desktop tools like Microsoft Excel make powerful partners in the world of astronomical photometry Common desktop tools like Microsoft Excel make powerful partners in the world of astronomical photometry DRO

Q & A Any questions about this process or anything in general that you would like to ask? DRO