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Debris finder, PolCor-2
An instrument to detect debris around young stars


  1. Introduction
  2. Exoplanets
  3. Stars dust disc
  4. Albanova, research center in Stockholm
  5. The instrument, PolCor-2
  6. The mechanical box's surfaces
  7. Coronagraph
  8. Mirror set one
  9. Filters
  10. Lyot Stop
  11. Servo motors
  12. Polarizer
  13. Parabolic and flat mirror set two
  14. Lucky Imaging
  15. The camera
  16. The computer
  17. Test of the instrument that has been done
  18. Conclusion
  19. End of demonstration
  20. Follow up with links of information about coronagraphs

17: Test of the instrument that has been done

Göran tells:
"We typically get a resolution of 0.7" and with Lucky Imaging 0.4" (camera mounted on NOT, 2.5 meters mirror). You can also push the system up to 0.2" with image selection and deconvolution but it increases the noise and the dynamics are reduced. With this camera has basically the internal noise been reduced to zero."

"One thing that must be handled is the background light (light pollution and the noise from this). One method that is common in the IR wavelength is to move the image field (chopping and / or node) to the side where no object are and take a new image. This image is then subtracted from the object image. Proven technology, but more than half of the exposure time is lost in the overhead. The optical chopper carrying out this is not on the pictures we've seen here. Tests show that the instrument PSF (Point Spread Function) behaves well and the instrument is well suited for high contrast imaging."

The test that has been performed including the red halo surrounding a compact blue galaxy and verified, object Mrk900. Simply put, the focused image is well composed. In this test the camera's gain is set to 100, and 12,000 images were collected respectively. Of these 85% were used in the final image. The frame rate was set to 10 Hz. To read the full report there is a link at the end where it can be downloaded as a PDF file, written in English.

Debris finder or planet hunter

Mrk900 in Visual filter (left) and Infrared filter (right).

The instrument has also been used successfully to detect AGB envelops (stars to become planetary nebulas), and more normal high-resolution images without the pole filter and the coronagraph mask that normally sits in the path. The instrument, however, is in an early phase and still has no measurements made on young stars and the dust ring that was written about in the beginning of this article. Watch NOT's website if something comes up there in future.

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