Skip to main content
SpringerLink
Log in

The 64 Mpixel wide field imager for the Wendelstein 2m telescope: design and calibration

  • Original Article
  • Published:
Experimental Astronomy Aims and scope Submit manuscript

Abstract

The Wendelstein Observatory of Ludwig Maximilians University of Munich has recently been upgraded with a modern 2m robotic telescope. One Nasmyth port of the telescope has been equipped with a wide-field corrector which preserves the excellent image quality (<0.8” median seeing) of the site (Hopp et al. 2008) over a field of view of 0.7 degrees diameter. The available field is imaged by an optical imager (WWFI, the Wendelstein Wide Field Imager) built around a customized 2×2 mosaic of 4k×4k 15 μm e2v CCDs from Spectral Instruments. This paper provides an overview of the design and the WWFI’s performance. We summarize the system mechanics (including a structural analysis), the electronics (and its electromagnetic interference (EMI) protection) and the control software. We discuss in detail detector system parameters, i.e. gain and readout noise, quantum efficiency as well as charge transfer efficiency (CTE) and persistent charges. First on sky tests yield overall good predictability of system throughput based on lab measurements.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11
Fig. 12
Fig. 13
Fig. 14
Fig. 15
Fig. 16
Fig. 17

Similar content being viewed by others

Notes

  1. Fraunhofer Telescope was built by Kayser-Threde GmbH, Munich and Astelco Systems GmbH, Martinsried

  2. SI900 is a trademark by Spectral Instruments Inc., Tucson, USA

  3. The field flattener was produced by POG Präzisionsoptik Gera GmbH, Germany

  4. The CCDs are a trademark of e2v Inc, Chelmsford, Essex, England

  5. Polycold PCC Compact Cooler is a trademark of Brooks Automation Inc, Chelmsford, USA

  6. I.e. AMiGo, a two channel CCD-camera for the former 80 cm telescope of the Wendelstein Observatory [11].

  7. Bonn Shutters [34] are widely used for large format astronomical CCD cameras, e.g. ESO OmegaCAM [18], Pan-STARRS-1 Gigapixel Camera [38]. Their simple and compact twin blade design yields uniform, “photometric” exposures even for short exposures (1 ms).

  8. FLI Microline 3041 is a trademark of Finger Lakes Instrumentation, New York, USA

  9. The linear stages were produced by Franke GmbH, Aalen, Germany

  10. The precision switches were produced by MYCOM AG, Berlin, Germany

  11. See next Section for details on drive logics.

  12. I.e. power supplies, RS232 to Ethernet converters, thermostats, switches, motor controllers, compressor relays, and embedded control PCs.

  13. Armaflex is a trademark of Armacell GmbH, Münster, Germany

  14. LabView is a trademark of National Instruments Corporation, Austin, USA

  15. Pollux Controller and Venus-2 command language are trademarks of PI miCos GmbH, Eschbach, Germany

  16. Moxa NPort is a trademark of Moxa Inc., Brea, USA

  17. Because of this the initialization run has to move “backwards”.

  18. Python Programming Language is a trademark of Python Software Foundation, Beaverton, USA

  19. We used the third row/column next to the border.

  20. We read three overscan regions from each port: Serial pre- and overscan, as well as parallel overscan. The serial overscan displays the smallest and most stable offset to the image region in bias and dark frames.

  21. The filters were manufactured by Omega Optical Inc, Brattleboro, USA

  22. Following the definition by [33].

  23. Exposure times M13: u: 60 s, g: 20 s, r: 10 s, i: 20 s, z: 40 s

  24. Exposure times SA95: u: 60 s, g: 10 s, r: 10 s, i: 10 s, z: 20 s

  25. Exposure times SA97: u: 30 s, g: 10 s, r: 10 s, i: 10 s, z: 10 s

  26. Exposure times PG0918: u: 60 s, g: 30 s, r: 30 s, i: 30 s, z: 30 s

  27. Since we have only a single observation in each filter per airmass, we were not able to calculate the extinction.

  28. From the [36] recalibration of the [37] dustmap.

  29. g filter: λ=4770 Å,Δλ=1300 Å, i filter: λ=7590 Å,Δλ=1400 Å

References

  1. An, D., Johnson, J.A., Clem, J.L., et al.: ApJS 179, 326 (2008)

    Article  ADS  Google Scholar 

  2. Baade, D., Meisenheimer, K., Iwert, O., et al.: Messenger 95, 15 (1999)

    ADS  Google Scholar 

  3. Barrick, G.A., Ward, J., Cuillandre, J.-C.: Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, vol. 8453 (2012)

  4. Bertin, E., Arnouts, S.: A&AS 117, 393 (1996)

    Article  ADS  Google Scholar 

  5. Bindel, A.: Master’s thesis, Ludwig-Maximilians-Universität München (2011)

  6. Buckley, D.R.V., Longmore, A.J.: MNRAS 257, 731 (1992)

    Article  ADS  Google Scholar 

  7. Castelli, F., Gratton, R.G., Kurucz, R.L.: A&A 318, 841 (1997)

    ADS  Google Scholar 

  8. Cousins, A.W.J.: MmRAS 81, 25 (1976)

    ADS  Google Scholar 

  9. Fukugita, M., Ichikawa, T., Gunn, J.E., et al.: AJ 111, 1748 (1996)

    Article  ADS  Google Scholar 

  10. Girardi, L., Grebel, E.K., Odenkirchen, M., Chiosi, C.: A&A 422, 205 (2004)

    Article  ADS  Google Scholar 

  11. Gössl, C.: PhD thesis, Ludwig-Maximilians-Universität München (2007)

  12. Gössl, C., Bender, R., Fabricius, M., et al.: Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, vol. 8446 (2012)

  13. Gössl, C., Bender, R., Grupp, F., et al.: in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, vol. 7735 (2010)

  14. Gruen, D., Seitz, S., Kosyra, R., et al.: ArXiv e-prints (2013)

  15. Hayes, D.S., Latham, D.W.: ApJ 197, 593 (1975)

    Article  ADS  Google Scholar 

  16. Hopp, U., Bender, R., Goessl, C., et al.: Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, vol. 7016 (2008)

  17. Hopp, U., Bender, R., Grupp, F., et al.: Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, vol. 7733 (2010)

  18. Iwert, O, Baade, D, Balestra, A., et al.: Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, vol. 6276 (2006)

  19. Janesick, J.: Scientific Charge-Coupled Devices, Spie Press Monograph, Pm83 (Society of Photo Optical) (2001)

  20. Janesick, J., Elliott, T.: Astronomical Society of the Pacific Conference Series, vol. 23, Astronomical CCD Observing and Reduction Techniques, ed. S. B. Howell, 1 (1992)

  21. Johnson, H.L., Morgan, W.W.: ApJ 117, 313 (1953)

    Article  ADS  Google Scholar 

  22. Kodric, M., Riffeser, A., Hopp, U., et al.: AJ 145, 106 (2013)

    Article  ADS  Google Scholar 

  23. Koppenhoefer, J., Saglia, R.P., Fossati, L., et al.: MNRAS 435, 3133 (2013)

    Article  ADS  Google Scholar 

  24. Kormendy, J., Bender, R.: ApJS 198, 2 (2012)

    Article  ADS  Google Scholar 

  25. Kurucz, R.: ATLAS9 Stellar Atmosphere Programs and 2 km/s grid. Kurucz CD-ROM No. 13. Cambridge, Mass.: Smithsonian Astrophysical Observatory, 1993., 13 (1993)

  26. Kurucz, R.L.: ApJS 40, 1 (1979)

    Article  ADS  Google Scholar 

  27. Landolt, A.U.: AJ 78, 959 (1973)

    Article  ADS  Google Scholar 

  28. Landolt, A.U.: AJ 88, 439 (1983)

    Article  ADS  Google Scholar 

  29. Landolt, A.U.: AJ 104, 340 (1992)

    Article  ADS  Google Scholar 

  30. Landolt, A.U.: AJ 137, 4186 (2009)

    Article  ADS  Google Scholar 

  31. Lee, C.-H., Riffeser, A., Koppenhoefer, J., et al.: AJ 143, 89 (2012)

    Article  ADS  Google Scholar 

  32. McLean, I.: Electronic Imaging in Astronomy: Detectors and Instrumentation, Springer Praxis Books / Astronomy and Planetary Sciences (Springer) (2008)

  33. Oke, J.B., Gunn, J.E.: ApJ 266, 713 (1983)

    Article  ADS  Google Scholar 

  34. Reif, K., Klink, G., Müller, P., Poschmann, H.: Astronomische Nachrichten 326, 666 (2005)

    ADS  Google Scholar 

  35. Rhodes, J., Leauthaud, A., Stoughton, C., et al.: PASP 122, 439 (2010)

    Article  ADS  Google Scholar 

  36. Schlafly, E.F., Finkbeiner, D.P.: ApJ 737, 103 (2011)

    Article  ADS  Google Scholar 

  37. Schlegel, D.J., Finkbeiner, D.P., Davis, M.: ApJ 500, 525 (1998)

    Article  ADS  Google Scholar 

  38. Tonry, J.L., Isani, S., Onaka, P.: Bulletin of the American Astronomical Society, vol. 39, American Astronomical Society Meeting Abstracts, 807 (2007)

Download references

Acknowledgements

The authors thank Johannes Koppenhoefer and Mihael Kodric for their support with the data reduction process with the WWFI. Furthermore we thank Daniel Gruen for helpful discussions regarding charge transfer efficiency. We also thank Michael Schmidt and Christoph Ries, the night observers at the Wendelstein Observatory for taking the necessary data for our on-sky calibration. Michael Schmidt also took the responsibility for wiring our imager, and we thank him for doing so. We thank Wolfgang Mitsch for giving invaluable advice on configuring the electronics of our camera. We acknowledge the constructive discussion with Dietrich Baade and Olaf Iwert (ESO). This research was supported by the DFG cluster of excellence Origin and Structure of the Universe (www.universe-cluster.de).

Author information

Authors and Affiliations

  1. Universitäts-Sternwarte München, Scheinerstraße 1, 81679, München, Germany

    Ralf Kosyra, Claus Gössl, Ulrich Hopp, Florian Lang-Bardl, Arno Riffeser, Ralf Bender & Stella Seitz

  2. Max Planck Institut für Extraterrestrische Physik, Giessenbachstr. 1, 85748, Garching, Germany

    Ralf Kosyra, Ulrich Hopp, Ralf Bender & Stella Seitz

Authors
  1. Ralf Kosyra
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Claus Gössl
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Ulrich Hopp
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Florian Lang-Bardl
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Arno Riffeser
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Ralf Bender
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Stella Seitz
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Ralf Kosyra.

Appendix: Charge transfer efficiency in more detail

Appendix: Charge transfer efficiency in more detail

In Section 3.10 we presented the results of the CTI measurement in our laboratory, but we only showed results for one CCD (number 0). In this Appendix we will show the complete set of measurements for all CCDs and compare them to the manufacturer’s results. Figure 18 shows the parallel CTI for all four CCDs compared to the values measured by Spectral Instruments. (USM: red crosses, green, blue and magenta; SI: cyan, yellow, black and red triangles). The plots show overall good agreement between the two measurements with few outliers in CCD1 and CCD2 (top right and bottom left) at low signal levels, where the measurement performed by SI yields higher values than our own results. Figure 19 shows the same for serial CTI. Here we can identify a few more outliers also at low signal levels, but this time SI measures lower values than ourselves. We trust our own measurements more than the SI measurements due to two reasons: First, our measurements are fitted by a power law, while the measurements showing outliers are not, and second, the port-to-port variations of our measurements (without outliers) are much smaller.

Fig. 18
figure 18

Parallel CTI for all four CCDs in the 500 kHz readout mode in dependence of illumination, compared to the values given by the manufacturer (SI)

Full size image
Fig. 19
figure 19

Serial CTI for all four CCDs in the 500 kHz readout mode in dependence of illumination, compared to the values given by the manufacturer (SI)

Full size image

The reason why port 2 of CCDs 0 and 2 (green data points in top left and top right of Fig. 19) show a lower CTI by approximately factor of 3 at low signal levels are unknown to the authors.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Kosyra, R., Gössl, C., Hopp, U. et al. The 64 Mpixel wide field imager for the Wendelstein 2m telescope: design and calibration. Exp Astron 38, 213–248 (2014). https://doi.org/10.1007/s10686-014-9414-1

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s10686-014-9414-1

Keywords

Search

Navigation