Drizzling: An Image Processer’s Dream Come True

There are plenty of nearby astronomical objects to investigate with a small telescope, but one of the most insidious problems which gets in our way is the issue of “seeing conditions”. When objects on the ground are heated by sunlight during the day, they then radiate throughout the night causing what astronomers call poor seeing conditions.  One can look at the moon or Saturn and see a wavy image one second, only to be followed immediately by a mighty fine and perfectly sharp image of the object. What to do?  Enter modern technology!  A method that was originally developed for the Hubble Space Telescope and then further adapted for amateur use, the drizzling method has caught on by storm. One can even download freeware to try it out:  Registax, which actually does a lot more than simple drizzling.  In the Observational Astronomy class, we actually try this out using the humble webcam as an imager. Taking thousands of video frames, the Registax software takes the best of the images then aligns and averages them together to make one much much better image. This last week we did just that, and here are just a couple of results. All images were taken with a C11 SCT and a ToUCam-II Philips webcam.


Now, you might be thinking, yes, ok, those are fine images, but WAIT, there’s more!  These were taken in the early evening in the spring here in Exeter, NH. The diurnal variation can be as much as 40 or 50 degrees F!  There is a lot of post-sunset heat coming up off those rivers, buildings and parking lots!  This is the video of Saturn from which we captured the frames to make that one sharp image. This is what you would have seen if you were looking through the telescope in real time.



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