Now and then you come to an astronomy event and see something that
blows your socks off.
Barry Clark gave a presentation and demonstration at Coonabarabran over the
weekend of a scope he has christened Louis XIV.
Louis XIV is a scope on steroids.
When a rare Celestron 14" Schmidt Camera became available on ebay,
Barry suggested to 3RF that they buy it. Probably only about ten of these
were ever built. Designed to be super fast with a very wide field of
view, they accommodate a film plate holder at the focus.
Normally, for visual use, they were not of much use. Unless you had the
exit pupil the size of a Blue Whale, they provided nothing for the visual
observer.
Until Barry came along that is.
Barry had long experience with image intensifiers and with the assistance
of Peter Read they equipped the Schmidt Camera with a purpose built
image intensifier camera rig. The imaging side of the intensifier has the
wide FOV to match the exit pupil diameter the optical system delivers.
Then through the magic of electronics, the image is displayed on a miniature
display and one can view it through an eyepiece in much the same way one
looks through the viewfinder of a video camera.
The image intensifier is exactly the same technology as used in military night
vision googles. Unless you have the right clearances, forget about trying to
import this stuff yourself any time soon.
But how does Louis XIV now perform as a visual telescope in practice?
In a word, stunning. The image intensifier multiplies the received photons
by thousands of times and the sky becomes ablaze with stars. The Tarantula
Nebula looks magnificent and the Horsehead is instantly apparent to
even a first time observer. None of this "What am I suppose to be looking for again?"
stuff that is so common when showing the Horsehead to someone.
Barry also had some hand-held image intensifiers in his kit including one
with an f/0.9 lens.
He lent me a couple to play with. Lounging back on the fold-up chair, the
views of the night sky through them were incredible. The LMC suddenly looked
like "just another galaxy" and you could see it for what it really is. When viewing
terrestrial objects in the dark, the technology was jaw-dropping. I looked
several hundred meters away down the field where a couple of astrophotographers
were set up. Their vehicle was barely visible naked eye but through the
night vision scope, I could clearly make out the scopes, the observers,
the make and model of car, their tables with laptops, etc. With his hand partially
obscuring the end so as to make a tiny aperture, Barry then pointed a standard
red LED torch in the direction I was looking. The entire field became ablaze with
light and I was staggered to then appreciate that the light of the LED would
illuminate several acres of observing field. I borrowed one of the scopes and with it
up to my eye, walked back to my room in the dark. I didn't bother with a torch,
there was enough light from the Milky Way to make the intensifier do its magic.
Every time I walked back before, I had to be careful not to run into the
bench, the BBQ, the tree or the sand pit - even when I used a red LED torch.
But with the image intensifier, everything about me was like daylight and I navigated
back with confidence.
At one point, I was staggered to see my own shadow being cast for
hundreds of meters across the observing field, the only back illumination coming
from a wall mounted bar radiator that was pointed 90 degrees with respect the
direction I was looking and some 20 meters behind me.
Thank you to Barry for his talk and for showcasing Louis XiV and for allowing
us to play with these amazing devices.
Louis XIV and night vision image intensifiers
