by Chris Peterson » Thu Nov 06, 2008 3:59 pm
apodman wrote:I didn't know it was possible to deform mirrors quickly enough to correct for turbulence...
Indeed, adaptive optics have been around for a few decades. Most of the major professional telescopes around the world utilize adaptive optics. There was a company in Colorado Springs about ten years ago developing a system for amateur and low-budget pro use, that had a segmented primary mirror with fast actuators on each segment. There was also a company more than ten years ago making an inexpensive second-order adaptive correction device for amateurs, useful for planets (it required a bright target). Many imagers these days are using tip/tilt correctors, which are a very simple form of adaptive optics.
What all these systems have in common is that they use a single reference for feedback- either a star near the target, or an artificial star created with a laser. The problem is that the area of sky that can be corrected is very small- typically less than an arcminute. So the adaptive optics work great for getting high resolution of small targets, but not for correcting wide fields. (Ground-based telescopes like the Kecks substantially outperform the Hubble on small targets.) The system used for this Jupiter image seems to have taken things to the next level, using multiple reference stars in order to construct a model of the wide field atmospheric distortion, allowing for compensation when imaging extended sources. Very promising technology (probably limited to IR for now, as atmospheric distortions are smaller at longer wavelengths).
[quote="apodman"]I didn't know it was possible to deform mirrors quickly enough to correct for turbulence...[/quote]
Indeed, adaptive optics have been around for a few decades. Most of the major professional telescopes around the world utilize adaptive optics. There was a company in Colorado Springs about ten years ago developing a system for amateur and low-budget pro use, that had a segmented primary mirror with fast actuators on each segment. There was also a company more than ten years ago making an inexpensive second-order adaptive correction device for amateurs, useful for planets (it required a bright target). Many imagers these days are using tip/tilt correctors, which are a very simple form of adaptive optics.
What all these systems have in common is that they use a single reference for feedback- either a star near the target, or an artificial star created with a laser. The problem is that the area of sky that can be corrected is very small- typically less than an arcminute. So the adaptive optics work great for getting high resolution of small targets, but not for correcting wide fields. (Ground-based telescopes like the Kecks substantially outperform the Hubble on small targets.) The system used for this Jupiter image seems to have taken things to the next level, using multiple reference stars in order to construct a model of the wide field atmospheric distortion, allowing for compensation when imaging extended sources. Very promising technology (probably limited to IR for now, as atmospheric distortions are smaller at longer wavelengths).