Outreach
On a personal level, viewing night sky objects directly through a telescope's eyepiece can be a deeply satisfying experience. But there is no doubt that using electronically assisted viewing with a video camera instead of an eyepiece has many practical benefits for outreach work. Simultaneous group viewing where the displayed object is in focus for all viewers and signal boost that gives much brighter views of dim objects are a direct result of using a video camera to show objects on-screen.
Taking this approach generally means having readily transportable equipment that is easily manhandled and does not take forever to set up on site. Because visitors like novelty it is usually advisable to view a number of different objects in a single night's session. For that reason auto-guiding is not realistic since it would necessitate recallibrating the auto-guiding software after each move and that would be quite time consuming. But, provided that the telescope mount is quite precisely polar aligned, on-screen images of up to quite a few minutes are possible by simply relying on the mount's clock drive to follow targets across the sky. When conducting a solo session (i.e. not in company with other telescopes) it is preferable to stick to bright, easily imaged objects (typically open and globular star clusters and very bright emmision nebulae) that require only short exposures so that visitors do not have to wait too long between the display of each object. Only when in company with other telescopes is it realistic to show fainter objects that require longer exposures. Visitors can then attend those other 'scopes while waiting for the fainter objects to display properly on screen.
Taking this approach generally means having readily transportable equipment that is easily manhandled and does not take forever to set up on site. Because visitors like novelty it is usually advisable to view a number of different objects in a single night's session. For that reason auto-guiding is not realistic since it would necessitate recallibrating the auto-guiding software after each move and that would be quite time consuming. But, provided that the telescope mount is quite precisely polar aligned, on-screen images of up to quite a few minutes are possible by simply relying on the mount's clock drive to follow targets across the sky. When conducting a solo session (i.e. not in company with other telescopes) it is preferable to stick to bright, easily imaged objects (typically open and globular star clusters and very bright emmision nebulae) that require only short exposures so that visitors do not have to wait too long between the display of each object. Only when in company with other telescopes is it realistic to show fainter objects that require longer exposures. Visitors can then attend those other 'scopes while waiting for the fainter objects to display properly on screen.
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So far, three "video" cameras have been used. The first was the GStar-Ex mono video camera. Then came the LP-Guide CMOS colour camera and lately the GStar-Ex3 CMOS colour camera has been added. The two CMOS cameras have a video imaging mode in which they can record video files for frame exposures ranging from micro-seconds up to 5 seconds long. But they also have a "still" imaging mode in which the exposure setting can be extended out to many minutes in duration.
As to telescopes : initially, the Meade ETX 90EC was used with the GStar-Ex mono camera but it was superceded by the Vixen R130sf and the cameras progressed to the LP-Guide colour camera and then to the GStar-Ex3 colour CMOS camera . As from May 2018 the Sky-Watcher PDS 150mm has taken over duty for outreach purposes. |