What an evening!
One of my friends from the Ottawa Valley Astronomy and Observers Group (OAOG – www.oaog.ca), Ken Whitnall, organized a dinner at a local restaurant with Dr. Christian Veillet, the executive director of the Canada-France-Hawaii telescope (CFHT - www.cfht.hawaii.edu) who was visiting Ottawa. He invited a limited number of members of the group so as not to have too large a crowd. So when I was invited by Ken to attend the dinner, I eagerly accepted.
While we had dinner, a wonderful conversation ensued in which Dr. Veillet explained to us various aspects of operating a telescope on Hawaii’s highest peak, from the administration side to the operation of the telescope and imagers. I was particularily interested in the imagers and how they operated, and he graciously answered all my questions.
What surprised me the most is that the maximum exposure time that they use for their MegaCam CCD camera is 10 minutes (20 with an H-alpha filter). Normally, a 10-minute exposure yields a limiting magnitude of 21.5-22, and stacked exposures go up to magnitude 26. Dr. Veillet explained that the best way to get deep-sky pictures was to take multiple short-exposure images and stack them together. The taking of short-exposure images ensures that none of the pixels are saturated on the CCD, and the stacking of those images provides for the maximum dynamic range possible. In other words, long-exposure images tend to cause some “clipping” of information once the CCD pixels reaches saturation (i.e. the well is full and can’t take any more light, thus losing information).
I then remembered what Rock Mallin had achieved a few weeks ago with his 16” Meade LX200 and his new MallinCam Hyper (mallincam.tripod.com) at Foymount, Ontario, the highest astronomical observing site in Ontario (1 800 feet). He had seen - live on the screen with 12-second exposures - magnitude 21.5. This means that Rock was seeing just as deep with his setup than the CFHT! This also means that the MallinCam Hyper effectively gives you the same light-gathering capability (but not the resolution) than that of a telescope with 9 times the diameter. Dr. Veillet was quite impressed with this.
After dinner, I suggested that we go out to coffee behind my place, and someone mentioned to Dr. Veillet that my observatory was in the back yard. After discovering that it was only 5 minutes away, he mentioned that he would like to see it before going back to his hotel. Of course I invited him to come and have a look, and he accepted. I then rushed out to my place before everyone else to open the observatory and set up the laptop with a few recent images that I took recently.
When he arrived at Galaxy Blues Observatory, he and the rest of the gang joined me in my humble observatory and I showed how I did my astrometry. We were quite cramped, with all nine of us huddling in an 8’X8’ observatory with a telescope in the middle, but it made for a cozy atmosphere. He was quite engaged and asked a lot of questions about the setup, MallinCam Hyper, other observatories from our group, and gave a few suggestions on how to improve my methodology when doing my astrometry.
Well, all good things come to an end, and after about 30 minutes, he had to return to the hotel. So we took a picture of our group (thanks Ken for taking the picture) in front of the observatory, I thanked him profusely for coming to see my setup, and off he went. The rest of us then went for a quick coffee, then headed out our separate ways.
|Back row, left to right: Ivo Leupi, Michael F. Vasseur, Dr. Christian Veillet, Greg Baggs
Front row: Todd Weeks, Joe Silverman, Pierre Martin. Absent: Ken Whitnall