Increase that distance, and greater reduction results and visa versa. Better images are also obtained when using these focal reducers at a reduction factor of 0.5x 0.8x, approximately. One focal reducer will not achieve optimum results with all types of telescopes, so there is no universal' focal reducer. First, let's have a look at some key optical parameters are needed to understand focal reducers. This fully multi-coated lens provides maximum light transmission with near full-field illumination. Many reducers, such as the Celestron HD focal reducer mentioned above, and many focal reducers for apochromatic refractors, are meant to be used within a few millimeters (or less) of the specified working distance to achieve the best possible image results. Increasing the operating distance, that is, moving a focal reducer away from the eyepiece or camera reduces its reduction factor, or conversely increases the amount of reduction. It is not a corrector or flattener. A couple of tiny dust particles between lens elements, uneven lens edge blackening, very minor coating blemishes, or even a very small fine lens scratch or two are very common in this Antares product and must be accepted as normal for this item. Sign up for OPT news, exclusive offers, and updates on the latest gear! The problem with those SCT reducers is that they cause chromatic aberration and require refocusing when using parfocal RGB/other filters. You can probably eke out 1.2 without noticing serious vignetting, which is a field stop of 31.5mm. Once installed, you can add additional accessories like T-Adapters, 1.25 Visual Back, Star Diagonal, or Off-Axis Guider. Just one question. They provide 0.75x focal reducers for these telescopes that takes an f/8 instrument down to f/6. When placed in the focal plane in front of a camera or eyepiece, a focal reducer leads to a wider field of view and a brighter image of extended objects, which is important for reducing the exposure times when imaging faint extended objects like nebulae or galaxies. The Celestron f/6.3 is ~150 compared to the Antares at ~70. For example, an 8" SCT without a focal reducer has an illuminated field of 38mm at 50% fall-off. It's usually specified in millimeters. I have the Japanese version and although I haven't used it in quite awhile, the views through it were superb with no internal reflections at all. I've seen some older threads saying that the Celestron, Meade and Antares FRs are all the same and manufactured in the same factory. This is one of our best-selling items, and customers have reported that this product is at least as good as, and probably better than, other leading f/6.3 focal reducers sold on the market for a lot more. Orders placed after 12:00 PM Pacific Time will be shipped the next business day. Meade once made an f/3.3 focal reducer for SCT scopes. For the best experience on our site, be sure to turn on Javascript in your browser. We will match any online price that we confirm as valid. Imaging - Focal Reducers and Flatteners - Page 1 - KW Telescope Looking forward to the day when I can do a shoot-out between a Japan and China Celestron, just for kicks. But the diameter of the image circle decreases by a factor of 0.63 to about 24mm. I really don't see any difference in the current crop except the "Meade" is usually the cheapest. However, in principle, the reduction factor of a focal reducer can be varied by changing the distance from the back of the focal reducer to the camera or eyepiece. As a real-world example plot showing the above relationships, let's look at the 1.25" GSO focal reducer that provides a design reduction factor of 0.5x. Some coma is visible in the corners, but the image is quite good for EAA applications. One of the most important factors in a telescope is its transmissionthe percentage of light that reaches the focal plane. Meade once made an f/3.3 focal reducer for SCT scopes. Now It only focuses near things, like some kind of macro zoom. Focal reducers (and focal reducer/field flatteners combos) are usually used with two types of telescopes, refractors and compound telescopes such as Schmidt-Cassegrain or Ritchey-Chretien. Here, there was a subtle difference . Unique focal reducer and field corrector lens accessory, Reduces the focal length and f/ ratio of your Schmidt-Cassegrain telescope by 37%, Provides a dual focal ratio instrument, without sacrificing image quality, Compatible with all Schmidt-Cassegrain telescopes (see compatible list in description). The reduction factor MR can also be written in terms of d2 as: When the focal reducer is placed at the working distance, D, that is when d2=D, then the reduction factor MR is equal to the design reduction factor MRD: Equations (6) and (7) imply these important considerations: Most manufacturers do not publish the focal length of their focal reducers, so it is not usually possible to calculate the working distance and design reduction factor. Reproduction without permission prohibited. In terms of reduction and correction - which are what reducer/correctors are supposed to do - both are superb. Some are available in 1.25" barrel format but with C threads. Celestrons award-winning Nature DX binocular gets a major upgrade with the addition of ED objective lenses. Despite never removing it no matter what I was looking at. Dedicated focal reducers for refractors are intended primarily for imaging, not visual observation. For example, many focal reducers designed for f/7 or f/8 ED refractors such as those from Tele Vue, William Optics, Sky-Watcher, and Meade are designed to have a working distance (or back focus) of 55mm. Antares f/6.3 SCT Focal Reducer - Rother Valley Optics Ltd A wider field of view and a lower magnification is also useful, with some focal reducers and with some eyepieces, for visual observers with telescopes with long focal ratios. October 11, 2010 in Discussions - Scopes / Whole setups. Thanks for any advice or experience you could share. Assuming you use the reducer with the stock 1.25" diagonal, it will operate at f/6.3. Can these economical focal reducers from GSO and other vendors result in good images? This may be a problem if the focuser tube or the diagonal (for visual observing) is too narrow to accept light at this larger angle. The resultant reduction factor was measured to be 0.46x. For the best experience on our site, be sure to turn on Javascript in your browser. Thks for that and its not for visual it for astrophotography. However, with appropriate spacers and a camera with a known back-focus, it is easy to determine the exact amount of focal reduction for a given setup (some imaging software packages will also let you derive this from images). Once focused it's pretty good. Try & buy if you like - usual mates rates. Sign up to get exclusive deals, observing tips, and new product announcements. In this case, an additional T-adapter (with an optical length of 50mm) is needed to get the spacing correct for a DSLR or other camera with a 55mm back focus. These reducers have a back focus (or design working distance) of 80mm. What is likely is that fatigue sets in, and also that as the targets move toward or a way from the meridian there will be changes for that reason alone. Maybe I got a lemon. For Stephen Wilkerson: The ZWO ASI120MC-S does come with a wide angle lens, HOWEVER, it is NOT intended to used when you are using the ASI120 camera attached to your telescope. For both imaging and visual observing, these reducers also improve image sharpness at the edge of the field by correcting for coma and field curvature. Can you tell me about the use of reducers in Maksutov-Cassegrain telescopes? 800-483-6287 Sign up for a new account in our community. Not one detectable iota of discernable difference. Turn it on and push Align. In about three minutes, youre ready to observe! Because I have not heard any complaints about the made in China R/C. Figure 6 shows a 1.25" focal reducer from GSO configured with a ZWO ASI224MC camera. Yellow and orange members of open clusters stood out a bit more as the various stars displayed their individuality. But nearly every observer who installs one of these devices is pleased with their performance. control and Sky Viewer display makes selecting your target easy. No retailers currently carry this product. So ab6110 is asking for a FR only without coma correction, there are a couple of brands who make special reducers for the ACF. Theres a long-running debate in these forums and even statements from some reputable dealers that the Antares is just a reducer (even though it is labeled Reducer/Corrector), whereas the Celestron is a true R/C, which flattens the SCTs naturally curved field and provides some edge correction. Thanks guys, appreciate the feedback. I have had the Japan unit on the back of my C5 since 1994 or thereabouts. Please note, orders placed after 10am on 2/28/2023 will be delayed. In this configuration, the 29.5mm camera nosepiece and a 6mm extension ring positions the reducer at a working distance of 53.5mm from the camera sensor, which is located 12.5mm inside the front edge of the camera. No difference. Not noticed any optical problems. Weasner's Meade and Antares Focal Reducers Review A former wireless communications consulting engineer and management consultant to various Fortune 500 companies, Manish started Agena AstroProducts in 2003. Easy solution found a very tiny dab of super lube on the threads and all was well and quiet. My Celestron was made in China and the Antares in Canada. Wow, that is a very detailed discussion! 1.2" in that scope is a field stop of 43mm at f/10 and 27mm at f/6.3. Figure 2 shows the effective of a focal reducer on the light from a telescope objective. I use the same back spacing for both on a small 6" Celestron SCT. In most cases, the easiest option is to choose the focal reducer made specifically for your telescope. Reducer Lens .7x - EdgeHD 1400 Learn More. The equations and argument in the Appendix of this article shows the relationship between the working distance and the reduction factor. The female end attaches to the rear cell of the telescope. Since the focal plane of an eyepiece is rarely precisely known(except for some brands such as Baader Planetarium and Tele Vue), and because the nosepiece of an eyepiece is of a fixed length, the actual reduction factor will be close to, but not exactly at, its designed reduction factor. When the camera sensor is placed at this distance, the reduction factor of these reducers is 0.75x. As mentioned in Section 2.3, the reduction factor for these focal reducers can be varied by adding spacers to move the reducer further from the camera sensor or eyepiece. That's partly because focal reducers correct for field curvature, which itself depends on the focal ratio and other optical design factors of the telescope. The C8 has no noticeable vignetting with a 32mm Plssl in the f/6.3 reducer. Its a good thing I have the super lube handy or my neighbors wont be happy with me.come to think of it, Im sure the small mammals here wouldnt be thrilled either! On the camera side, the focal reducer has male M42x0.75 or M48x0.75 threads that attach directly to the T-ring (with an M42-M48 adapter if necessary). If you are using a camera that has a back focus of less than 55mm, additional spacer rings will be required between the reducer and the camera.
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