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A very good extension of enhanced viewing for many people would be one of the CCD video camera systems offered today. These make it easily possible to share live viewing in our suburban surroundings with large groups of people, directly on a monitor and without the need for computers or software. I can attain a good image scale, equal to moderate (but not low!) powers, with a direct hookup to a CCD video camera. For a moderately high power, a combination with a 2x Barlow provides very good service. Everything will depend on the focal length of your telescope; my own telescope has a focal length of 81 inches and a focal ratio of F4.5. Telescopes with long focal ratios and much smaller apertures may produce a less satisfactory result. With such a camera connected to an image intensifier, the potential is far greater; now one can view or record deep space objects in true real time video. A complete system is also offered by Collins Electro Optics in conjunction with Adirondack Video Astronomy, who market a specialized video camera for the low light levels of astronomy, the Astrovid 2000. Nevertheless, despite the term CCD appearing in their names, the function of these devices should be considered in the realm of video; their simplicity of operation and moving video image keep them entirely separate from the standard astronomical CCD camera. For meteor showers, occultations, Jovian satellite transits, etc. the potential goes farther still, if this is your inclination. Video does indeed have some unique attributes.

If you are optically and mechanically handy, you may be able to adapt an intensified system other than the Collins to work with other CCD video cameras, particularly if you have already found a way to utilize an alternative image intensifier with your telescope. You will need, however, to incorporate the eye lens component into the optical path in order to produce a video image, since the intensifier alone does not have a "see-through" light path like a regular eyepiece. It will likely need to be placed further from the intensifier screen.

The real time video deep space images used in Chapters 7 were taken using the Astrovid 2000 system in combination with the Collins I3 image intensifier (Figure 2.2). The original video footage was saved directly to hard drive via Firewire. The frames were selected and are reproduced here with minimal and

Astrovid 2000 CCD video camera

Collins camera-to-intensifier adapter

TeleVue/Collins eyepiece component

Collins extension adapter

Collins I3Piece image intensifier

Figure 2.2. Image intensifier and video equipment mounted on the author's JMI NGT-18

telescope.

Astrovid 2000 CCD video camera

Collins camera-to-intensifier adapter

TeleVue/Collins eyepiece component

Collins extension adapter

Collins I3Piece image intensifier

simplest processing (reflecting my bias towards live viewing), and provide a good overall impression of real time observations. I did not wish to further enhance the images beyond the resolutions here; the primary aim is to provide a guide for visual expectations, and not necessarily to extract the maximum detail beyond the image represented in the frame. You will find that moving video on the monitor, is generally more revealing than still frames; when contrasting video frames against drawings (also included wherever possible), you may likely be best prepared for what you may actually see. You may also get some idea just how hard it is to record the subtleties which only the eye detects, but for our typical suburban locations the examples may prepare you better than have many previously available materials.

For deep space video applications, a recursive frame averager (also available from Collins), becomes a virtual necessity. You will find that the effects of electronic noise from the image intensifier become quite pronounced on the monitor without such a device, and worse, result in unusable individual frames if you wish to record still images. Without a frame averager, you will find that as you work through the recorded video, frame by frame, you will be astounded by all the varieties of the same image you will see. This may cause you to wonder how all of them could come together to form a reasonably coherent moving image, to resemble a single deep space object. Frame averagers work by capturing a set number of video frames, and removing artifacts not common to each. The more frames in the sample (up to a maximum of 16 with the Collins unit), the more effective, technically, the device is, although the "softer" the image may be. Freeze frames may be utilized as well, in which multiple frames are averaged together to produce one clean still image. These indispensable devices are not inexpensive, but with no alternatives in sight, they are a part of the equation you must consider once you delve into deep space video with image intensifiers.

Just as in live viewing through the telescope, in video applications higher powers can readily be obtained by coupling the image intensifier to a Barlow lens. Not every deep space object will provide sufficient illumination for this always to be effective, though for Solar System viewing on the monitor without the intensifier (Figure 2.3), higher powers become something of a necessity. With my own tele-

Figure 2.3.

JMI NGT-18 telescope with complete Astrovid 2000 video assembly and video control box (on the table), which provides manual gain, shutter speed settings, as well as contrast.

Figure 2.3.

JMI NGT-18 telescope with complete Astrovid 2000 video assembly and video control box (on the table), which provides manual gain, shutter speed settings, as well as contrast.

scope's focal length of around 81 inches, a 2x or 3x Barlow, working through the already enhanced image size of the video image, is generally sufficient. (For deep space, very few objects are bright enough to support the use of higher powers than a 2x Barlow produces with my telescope's focal length.) Not every telescope has such a considerable focal length, of course, but here is where the technique of eyepiece projection will provide a ready solution. Such eyepiece adapters are widely available. Be aware that as the magnification goes up, so do the difficulties of locating objects, in addition to focusing issues; none of these is insurmountable, though.

Additionally, there is yet another way video imaging has great appeal; it is sometimes possible to see certain detail on the monitor other than what one is able to see through the eyepiece! On planets, the objectivity of being able to stand back and look at the image with both eyes seems to heighten the visual awareness, or at least it is a less straining experience. Astronomical video cameras often also respond favorably to the use

Power supply for Averager (Sony) Media

Converter (Collins) Recursive

Power supply for Averager (Sony) Media

Converter (Collins) Recursive

Frame Averager Computer (iMac)

Figure 2.4. Additional equipment used for recording images.

of standard color filters (although with monochrome cameras these results appear as contrast differences with a varying emphasis of planetary features), revealing details in much the same way as in normal live viewing. With the proper equipment, it is also possible to record the images directly to your video recorder as well as computer, as movie clips or still frames.

I once again must differentiate between video and CCD imaging. The latter is capable of producing some of the most stunning images imaginable, but remember they are not observable in real time. Video can indeed provide us with monitor viewing and a reliable record of something of the real time experience, often remarkably so. But there is still ample justification to draw what we see at the time, since there is still nothing yet to quite duplicate the way the eye registers detail. It also perceives momentary flashes of these details with subtleties and finesse altogether different to the finest CCD image. (Strangely, occasionally CCD, or even CCD

video images can reveal certain detail the eye can miss.) These rare moments of clarity come about only moment to moment and no camera knows when these will occur. Here it is that the video camera has a unique strength: by examining what was recorded from the moving video record, frame by frame, it is possible to catch a particularly revealing frame of the object, when detail is suddenly in abundance, just as when the eye perceives those momentary flashes of detail. This simple method allows the user to store decent still images in a simple way, without the processing of more elaborate imaging systems.

To read further than this text is able to cover on the whole concept of using video cameras to view and record moving and still astronomical images, Video Astronomy by Steve Massey, Thomas A. Dobbins and Eric J. Douglass from Sky & Telescope's Observer's Guides series, provides probably the definitive information available today.

As far as time-exposure astrophotography and true CCD imaging are concerned, I must confess that as yet I have not spent time in pursuing these for myself. This is partly because so many fine images are readily available these days, and although it is possible to produce remarkable results even in light polluted skies, there is still no ignoring the fact that the resulting images do not provide a comparable experience to actually viewing their astronomical subjects live, the ongoing focus of this book. Because of this, I am not sure that I will ever muster the enthusiasm that would be required to produce the stunning results we frequently see these days with these techniques. However, if these other applications appeal to you, then I encourage you to pursue them with the enthusiasm they rightly deserve, even though the impetus of this writing is unlikely to be on the same road that you may find yourself traveling.

I should add that the above approaches are not the only way to produce exceptional camera images. Color images of surprisingly fine quality can be obtained with monochrome CCD video cameras taken through various color filters, later processed and combined on computer to produce fine full-color images of exceptional resolution. There are also color CCD video cameras available, such as the Astrovid PlanetCam. They are able to produce remarkably good planetary and lunar images in full color, live, and without the need for combining images taken through different filters, although they are not as light sensitive as mono-

chrome versions. This disqualifies them from deep space applications, of course. Yet another way can be with a digital camera; it will also allow images to be downloaded directly to computer and enhanced in the processing. Coupled to an image intensifier and needing exposures of only a few seconds on deep space objects, digital cameras can produce remarkably well-resolved and illuminated images; examples, taken by Bill Collins on deep space subjects, may be seen later in this book.

Still another CCD video system comes yet closer to live deep space viewing, but there are major differences. Aside from live video, this deluxe system (the STV by SBIG) allows the user to build up images in single video frame exposures (up to 10 minutes) and witness them on the built-in monitor, or external monitor. It is also possible to combine multiple exposures and view them as they are accumulated. Not quite the same thing as actual real time viewing, but I think you'll agree it may be a step in the right direction, and a viable option for many. The results are apparently remarkably good. Recently, a new Astrovid video camera was introduced - the StellaCam. This, along with its more sensitive counterpart, the StellaCam EX is also capable of producing live deep space views of the brighter objects on a monitor, and the less bright ones by accumulating frames in a similar simulation of real time as the SBIG system, but at a significantly lower cost. Certainly, priced at US$695 (2002), it is the amongst the most affordable options for the suburban astronomer. It is claimed that the StellaCam can effectively increase the aperture of any given telescope by two to three times, a similar claim we already know about image intensifiers, and a key issue for us in the suburbs. (It can also be attached to the Collins I3; the results would be interesting at the very least, but as yet, I have not tried it.) The manufacturer, however, does state that its resolution is not the equal of its top-of-the-line Astrovid 2000, and one should bear in mind that with any camera one is still not looking directly through the telescope, but indirectly at a monitor. Nevertheless, if budgetary constraints make the purchase of some kind of effective image intensifier out of the question, then maybe one of these systems offers a good option, and the essence of this book will still remain largely valid for such an approach. It has to be cautioned, though, that any of these video systems may be a whole lot more trouble to set up and use for live observing sessions than you may be accustomed to.

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