CFHT, Instruments, Imaging, AOB, First Images from PUEO !

First Images from PUEO !

The first engineering run took place from March 28 to April 2nd, 1996. Here are a sample of the first results.

Click on the images to get an enlarged version.

The very first corrected and uncorrected images we obtained. K band, magnitude 11.7, Seeing (0.5 microns) = 0.94 arcsec.

[very first images]

Examples of image profiles obtained on a V=9.2 star. Seeing at 0.5 microns was 0.68 arcsec (D/r0 = 24), i.e. worse than median seeing at Mauna Kea. As mentionned on the figure, Strehl ratios at J,H and K are 17.5%, 35% and 60% respectively (FWHM are 0.091, 0.105 and 0.1275). All images have been taken with integration time larger than 7 seconds.

[J cross section] [H cross section] [K cross section]

A double star of measured 0.276 arcsec separation (easy), at H band.

[double star image]

Performance of the system on faint guide star : Compared to the expected results, we found that we were off by roughtly 1 to 1.5 magnitude. The overall transmission from the top of the telescope to the APD in the WFS is 17%. This is roughtly a factor 2 smaller than what was expected. This may be attributable to the visible/infrared dichroic, or to the coupling with the APD fibers. We have been able to close the loop without any problem on V=15.2 stars, and get sensible image improvement in J,H and K (see figure below). It is expected that we should be able to get some image improvement with V=17 stars. We are currently investigating the transmission problem. Below is a uncorrected/corrected image in K band, on a V=14.5 star. Seeing at 0.5 microns was 0.51 arcsec (D/r0 = 18), which approximately the median seeing at Mauna Kea. The Strehl ratio of the corrected image (right) is 29%.

[double star image]

and this superb high resolution image of NGC6093 in K band. Note that the FWHM is 0.13 arcsec (diffraction limit at K) over almost the whole field of view. This image is a mosaic of 12 individual images of 30 seconds exposure time. Even with such a short exposure time, the magnitude range spans over 8 magnitudes. This illustrates the dramatic improvement in detection and dynamic over seeing limited images (the flux being concentrated over a much smaller sky area).

This B&W log image(117KB) / Color image(133KB)

[ngc6093 image]

Canada-France-Hawaii Telescope

Created 1 April 1996.
Page maintained by Jean-Luc Beuzit.
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