Quote:
Originally Posted by theodog
Be careful, numbers like that could find you in a Royal Commission. 
But, seriously, 10 min here and there while waiting for the real target to rise, or the sky to get perfectly settled soon adds up.  |
From the celestron white paper on the scope
16. Big! Fast! Wide! Sharp!
Celestron’s telescope testing observatory is located at their headquarters in Torrance, CA, a place not known for pristine dark skies. In fact, these semi-urban skies are typical of the skies many Celestron owners experience on a nightly basis. “If we did all of our testing under perfect skies,” says Celestron Product Manager of Astronomy, Bryan Cogdell, “we would not be serving our customers well. It’s important that we know and understand how our telescopes operate under the typical suburban and urban skies.”
“For those who are new to astronomical imaging, as well as those who have learned astroimaging the hard way, the RASA comes as a revelation,” said Cogdell. “The newcomers have heard stories about hours-long exposure times,” he said, “and the old-timers have experienced those all-night sessions imaging at f/8 and f/10. Those guys have done it all: polar alignment, lengthy exposures, autoguiding, and stacking! They have paid their dues.”
For them, the RASA comes as new experience. “With the ISO of their camera set to 6400, old-timers make a single 15-second exposure at f/2.2 and see a creditable image. They are totally amazed! If they drop the ISO to 1600 and expose for 60 seconds, they see an image that would have taken 20 minutes at f/10.” There’s no need to guide for just 60 seconds; quick polar alignment is good enough. “With minimal complexity,” notes Cogdell, “veterans can apply their hard-won skills, shoot a dozen five-minute exposures at ISO 400, stack them, and get rewarded with the finest images they’ve ever taken.”
As the party responsible for testing and evaluating the RASA from the first, Cogdell says he’s been consistently impressed. “With the RASA,” he says, “we have given observers the ability to do fast imaging, but we also need to make people aware that ‘real time astronomical imaging’ is now possible with a high-étendue telescope.” The coming generation of high-sensitivity CMOS sensors means you will capture and watch deep-sky objects on a computer screen, real-time, moving smoothly as you move the telescope. “It’s going to be great for group viewing and public star nights. You press ‘go-to M51’ and everyone sees the Whirlpool as it glides into view.”
Another new technology is image live stacking. Atik’s Infinity camera makes imaging far more intuitive. “The CCD is small, but you watch as the image grows stronger and the noise drops away. The focal length of the RASA gives you a field of view perfectly suited to viewing the Messier objects,” Cogdell explains. Software takes care of image alignment and stacking, even when the telescope is not perfectly polar aligned. “High étendue gives the RASA a big advantage. With other telescopes, you need focal reducers; with the RASA, you’re ready-set-go at f/2.2.”