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fmaster Expert focussing and off-axis viewing system - Great astro-photography depends heavily on perfect focus. The Focus-Master is essentially a lens cap with three holes that simply fits over the end of the telescope and helps you achieve perfect focus in seconds. At first glance the Focus-Master is just a focussing aid based on the tried and tested principle of the three-hole mask. Now we have refined this idea and created a mask that not only offers the standard three-hole focussing feature, but by removing the special threaded cap you have a perfect off-axis aperture which has been matched to the useful viewing area between the secondary and the maximum diameter of the corrector lens of popular sizes of SCT. The result is a powerful and versatile accessory that has uses in focussing (photo and visual), lunar and planetary viewing, double star observation and collimation adjustment. The Focus-Master has the additional benefit that it can be used as an off-axis filter holder for white light and Ha Solar filters by BC&F Astro Engineering & Coronado. Focussing with the Focus-Master - Simply remove the three black plastic plugs (they just pop out by pressing from the rear) and attach the mask to the front of the telescope. If you observe a star of moderate brightness you will see that at an out of focus position you will be presented with an image not of one star but three. Adjust the focuser in the direction that causes the stars to move together and keep adjusting until the three stars merge into just one perfect image - and the scope is now focused. It really is that simple. This process will work just as well with lunar and planetary targets and will allow you to focus the instrument perfectly even when the seeing is poor or on a dim camera focusing screen or CCD monitor. In these situations it can be difficult to tell the difference between one focus position and another. With the Focus-Master attached there is no uncertainty: if the image is out of focus you will see not one but three images. Adjust the focus and make the three images merge into one and the instrument is focused. Simply remove the mask and you are ready to begin imaging. But the story doesn't end here. One aperture of the Focus-Master has a special threaded rim that enables our range of precision-mounted glass solar filters to be screwed into place for off-axis viewing* (see next item below for more info). If this isn't enough, the Focus-Master also provides a good method of checking and adjusting collimation. Still not convinced? The Focus-Master has three large plastic plugs for it's holes so it makes a perfect replacement dust cover as well! Please specify aperture when ordering. * Our range of adapters can also be fitted with Coronado Ha filters.
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Click on the image above
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ac637 Following the success of our original Focus-Master focussing aids, we have launched a simpler lower-cost version that has all of the quality and focusing-aid function of the originals, but with a simplified design. The Focus-Master Lite is essentially a lens cap with three holes that simply fits over the end of the telescope and helps you achieve perfect focus easily and in seconds. The result is a powerful and versatile accessory that has uses in focussing (photo and visual), lunar and planetary viewing, double star observation and collimation adjustment. The Focus-Master Lite is easy and intuitive to use. Adjust the focus and make the three images merge into one and the instrument is focused - it’s that simple! Then just remove the mask and you are ready to begin imaging. This process works just as well with lunar and planetary targets as with stars, and will allow you to focus the instrument perfectly even when the seeing is poor or on a dim camera focusing screen or CCD monitor. Product descriptions AC637, AC638 and AC639 aluminium construction with central screws that act as hand knobs to allow the mask to be attached and removed without risk of touching the telescope optics. AC640, AC641, AC642 and AC643 aluminium “cap” construction with plastic caps for each of the three holes and three retaining lock thumbscrews
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The Focus-Master Lite family Click on the image above
Three images...
... merged into one |
