1. Astronomical Data Collection and Processing of LLPV’s in GGC’s at the BGSU Observatory J Leon Wilde TAA Seminar, UT, February 2nd, 2007

2. Intro Before observing… BGSU’s telescope CCD Imaging Typical observing night Image processing My Thesis Work

3. Before observing… What to look at Where to look from What instruments? –0.5 m Reflecting telescope –CCD imager

4. The telescope Incoming starlight Secondary Mirror Primary Mirror Focus on optics

5. The CCD Imager “Charge Coupled Device” Si diodes KAF-1000E –Specs.pdf for KAF-1001E

6. Why use CCDs? High QE High Linearity Large dynamic range Uniform response Low Noise Digital

7. Our CCD’s QE Blue – KAF-1001E Black – KAF-1401E

8. CCD Basic Design Our CCD –24x24 micron pixels –1024x1024 array

9. Gate Structure/Function Voltage push Sends data to onboard amplifier and A/D converter Our CCD –Two phase push –Charge transfer efficiency = 0.99997

10. CCD illumination Frontside –Photons pass through phasing gates –QE lower than Bs Backside –Etched back –High QE –Hard to make, thus... –More expensive Our CCD –Frontside

11. CCD Drawbacks Noise! –Dark current –A/D conversion –CCD flaws –Worked out during processing Expensive! –Delicate manufacturing process –Better science means higher standards

12. Dark Current Thermal activity on CCD chip

15. CCD Linearity Pixel value (ADU’s) Integration time (seconds) SBIG ST8 Linearity Test

16. CCD Coatings CCDs naturally insensitive to blue Coatings used –Coronene & Lumogen phosphors –Lumogen better of the two –Lumogen commercially used in highlighters Our CCD –“Blue Plus Transparent Gate”

17. Blooming Our CCD –No anti-blooming gates –We’re careful!

18. Typical Night Arrive an hour before sunset Get equipment ready Take bias frames / flat field frames Observe! Take more bias / flat fields Send images to Dr. Layden’s computer Shut equipment down Go home!

19. Image Processing Correct the images –Optics aren’t perfect (dust donuts, vignetting) –CCDs aren’t perfect –Electronics aren’t perfect –Observers aren’t perfect “The problem exists between the chair and the computer.” “Garbage in, garbage out.” Get science from the data –Convert ‘relative’ values into ‘real’ values Programs: –IDL and IRAF

20. Processing… Zero (Bias) frame –Remove floor value –Subtract combined image from data Dark frame –Remove dark current –Subtract combined image from data Flat field –Remove non-uniformities arising from: CCD flaws Optics flaws –Divide combined image from data

21. Processing… Photometry –RR Lyrae Program, getting star magnitudes versus time Pretty pictures –Combine images from different color filters

22. Pretty pictures Ring Galaxy AM 0644-741 from Hubble

23. My Thesis Work: Why Study LPV’s? Variability provides distance calibrations LPV’s are understudied For SIM (Space Interferometry Mission)

24. Background What are they?

25. Why look in GGC’s? Stars are of the same age Stars are at the same distance Stars are similar in composition

26. Detection Acquire data over long enough time Process images Image subtraction –DAOPHOT, ISIS

27. Getting the Data

28. NGC 6539 5 years of data [Fe/H] = -0.66

29. New GGC’s “New” to us! Selected from Harris Catalogue –min Dec –max V_hb –Small: Core concentration E(B-V) - Foreground reddening –Span of [Fe/H]

30. PROMPT Images!

31. PROMPT Back to Harris Catalogue Tracked down known LPV’s Corrected coordinates

32. PROMPT NGC 288

33. PROMPT NGC 1261

34. PROMPT NGC 1851

35. Next steps… Our data: –Finish processing / Photometery –Learn DAOPHOT –Perform DAOPHOT on recent data / NGC 6539 PROMPT data: –Determine best collection method

36. References People –Dr Andy Layden for his time, Dr John Laird for his books –Mike Smitka –Brian Pohl & Dr. Bruce Carney, UNC Chapel Hill Book –Steve B. Howell, 2000, Handbook of CCD Astronomy, Cambridge University Press Websites –http://physics.bgsu.edu/~layden/observatory.htmhttp://physics.bgsu.edu/~layden/observatory.htm –http://zebu.uoregon.edu/ccd.htmlhttp://zebu.uoregon.edu/ccd.html –http://www.ccd.com/ccdu.htmlhttp://www.ccd.com/ccdu.html –http://www.astro.virginia.edu/class/oconnell/astr511/lec11-f03.htmlhttp://www.astro.virginia.edu/class/oconnell/astr511/lec11-f03.html –http://www.wildealien.com/ccd/http://www.wildealien.com/ccd/ PowerPoint file available online –http://physics.bgsu.edu/~jlwilde/taatalk-feb07.ppthttp://physics.bgsu.edu/~jlwilde/taatalk-feb07.ppt Contacting me: –jlwilde@bgsu.edu

37. Thanks for your attention!