1. Performance of Phase Apodization Coronagraphs at the MMT
Michael Gaj
Dr. John Codona
The University of Arizona
Center for Astronomical Adaptive Optics
Arizona Space Grant Consortium Statewide Symposium
April 18th, 2008

2. Astronomical Imaging
Two main problems in extrasolar-planet are diffraction patterns and atmospheric speckles.
Although adaptive optics systems do a good job of suppressing atmospheric turbulence, they cannot correct diffraction patterns and speckles.
Some diffraction patterns can be corrected with modern coronagraphs, but they cannot eliminate the speckles.

3. What is the Phase Apodization Coronagraph?
Unlike other coronagraphs, the PAC is able to eliminate diffraction patterns while maintaining constant telescope position.
Result:
Speckles can be averaged and the background can be smoothed.
Astronomers are now able to observe nearby extrasolar planets thousands of times fainter than their parent star.

4. Image at MMT with PAC

5. PAC Efficiency
Although the PAC is a proven method of image correction, the device breaks down and looses its effectiveness at a certain wavelength.
The question then becomes: At what wavelengths can the PAC successfully operate?

6. Simulated Images at MMT
5 Microns Microns Microns
1 Micron Microns

7. Performance of PAC

8. Results
From the graph, the PAC proved to be most effective at a wavelength of 5 microns.
However, there is very little sensitivity difference for wavelengths of 5, 2.2 and 1.65 microns over an angle of .7 arc seconds.
Wavelengths lower than this value showed no significant improvement in image quality.