Évaluations - 2, GPA: 3
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Facilité d'utilisation
Image processing software can then be used to select the best frames to combine for best results. Refocus often throughout your imaging session. This ensures at least some of your images will have an excellent focus. It is also not uncommon for telescope movements to alter the focus slightly, so be sure to refocus for any new astro-imaging targets. choosing a Site for astro-imaging Once you have a focused image, you may find your image shifting and washed out. This can be caused by many environmental factors. Poor seeing (movement of molecules in the air, such as heat rising) and poor transparency (moisture, smoke, or other sky contaminants) will all serve to reduce image quality. That is why most major astronomical telescopes are on high mountains in thin air, to get above much of the seeing and transparency problems. Also, wind will move your telescope and affect images. Your eyes viewing through an eyepiece can change slightly to compensate for disturbances like these, but the camera cannot. Keep these factors in mind when choosing an observing site for astronomical imaging. For the best astro-images, we recommend finding a location with dry air, some altitude, and away from city or streetlights. Even a nearby hilltop in the countryside can provide better viewing conditions than many convenient backyard locations. using Focal reducers and Barlow lenses Focal reducers serve to decrease the focal length of your telescope. This increases the field of view seen by the camera (decreases camera magnification). This can be useful for obtaining images of wider objects, such as the full Moon or a landscape vista. Barlow lenses, or other tele-extenders, increase the focal length of your telescope, which makes the camera field of view narrower (increases camera magnification). This is useful for high-power planetary images. Keep in mind that when the focal length is doubled, the image will become four times dimmer, so a longer exposure may be necessary. For best planetary imaging, you should shoot with an effective focal ratio (telescope focal length . telescope aperture) of f/20 or greater. This will give you a good combination of image brightness and image scale for planets. For most telescopes, a Barlow lens will be required to obtain this focal ratio. For example, Schmidt-Cassegrain telescopes usually have a focal ratio of f/10. A 2x Barlow lens doubles the effective focal length of the telescope, which makes the focal ratio f/20. Similarly, a 3x Barlow lens will yield of focal ratio of f/30. You can also try using multiple Barlows to obtain even greater effective focal ratios. There is a limit to how large a focal ratio your telescope and seeing conditions can handle, however. Experimentation will be needed to see what your telescope is capable of in the seeing conditions on a given night. If the image appears somewhat dim and fuzzy on the computer screen, you may want to consider removing the Barlow lens. (Focal Reducers and Barlow lenses available through Orion, check the catalog or OrionTelescopes.com). Filters For some types of planetary imaging, you may want to use color filters to bring out subtle details. Any standard Orion 1.25" filter will thread into the front of the SSVE’s barrel. Try using different color filters on a planet to see which filters help best show planetary details. Neutral-density Moon filters and variable-polarizer filters are useful to reduce the glare from the moon. They can also be used to reduce the glare from Venus. Solar Filters Warning: Always use a full aperture solar filter when viewing the sun. With a properly fitting full-aperture solar filter attached to your telescope, you can use the SSVE to take images of the Sun and the sunspots on its surface. (Filters available through Orion, check the catalog or OrionTelescopes.com for more information). Flip Mirror As easy as flipping a switch, the Imaging Flip Mirror enables the astrophotographer to find, center and focus a target visually with a 1.25" telescope eyepiece, then photograph it with a CCD camera. All without swapping out any equipment. It’s a real timer saver, making the normally tedious task of focusing with the CCD camera alone easier and quicker. (available through Orion, check the catalog or OrionTelescopes.com for more information). Figure 4. Use software to assemble individual frames to create a higher resolution image. Image taken using Orion Apex 90mm Mak-Cass telescope and Orion 0.5x Focal reducer. 10 Individual images assembled In Adobe Photoshop. things to Do Moon Learn your way around our closest celestial neighbor. • Image the craters, mountains and valleys. • Image the different phases from New moon to Full Moon • Image the detail at the terminator • Create a moon mosaic (Figure 4) Planets • Take a movie of the position of the great red spot of Jupiter during the Gas Giant’s <10 hour day. • Image Jupiter’s moons and their shadows as they transit across the Gas Giant • Follow in Galileo’s footsteps by Im...
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