Due to the design, the Reducer/Corrector lens does diminish a small amount of field curvature common to all Schmidt Cassegrain telescopes but does not eliminate it. Optically, it consists of a four-element lens that is fully multi-coated for high contrast and resolution. A former wireless communications consulting engineer and management consultant to various Fortune 500 companies, Manish started Agena AstroProducts in 2003. Quite interestingly it bears the very same engravings of the Meade 4000 r/c (including "series 4000") except for "MEADE". Go behind the scenes with Celestrons product development team and learn more about our award-winning and patented innovations. Equation 6 & 7 item two & three does not make sense, both say increase its reduction (one should say reduce its reduction?). That was fun. The telescope side of the barrel is often threaded with an M48 x 0.75 thread for standard 2" astronomy filters. Here, there was a subtle difference . Stock focusers in an SCT move the mirror of the scope to change the position of the focal plane, and they have sufficient travel to accommodate a focal reducer. But the diameter of the image circle decreases by a factor of 0.63 to about 24mm. Perhaps not exactly- there will be some uncertainty because of manufacturing tolerances and so forth, but it will be close. For imaging, a T-adapter is threaded to the camera side of the focal reducer, which in turns connects to the camera with the appropriate hardware. It's easy! Most reducers have a design reduction factor, MRD, that assumes the reducer is placed at a specific working distance, D, from the back surface of the focal reducer itself. Antares or Celestron? With the Celestron Reducer/Corrector Lens, thats precisely what you get. Many focal reducers for refractors have a working distance (or back focus distance) of 55mm. It's usually specified in millimeters. When the camera sensor is placed at this distance, the reduction factor of these reducers is 0.75x. 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. Celestrons patented StarSense Technology makes it easier than ever to locate objects in the night sky, even if youve never used a telescope before. If the reducer is placed elsewhere, at a position called the operating distance, the focal reduction factor will not be as advertised. Please note, orders placed after 10am on 2/28/2023 will be delayed. This focal reducer is made to attach to the rear cell of Schmidt-Cassegrain or Maksutov-Cassegrain telescopes. I read another thread in a different forum about F6.3 reducer correctors and one amateur posted an image about glue coming out of an astromania f6.3 reducer which he planned to return. We tested GSO's 1.25" 0.5x focal reducer at a variety of operating distances and calculated the field of view through a telescope to derive the actual reduction factor that is plotted below. Clearly cost is a big factor for satisfied users. Turn it on and push Align. In about three minutes, youre ready to observe! Fortunately, my neighbors are not out in their backyards at 11 pm, or they may have thought I was torturing a small mammal. A f/10 focal ratio now achieves a f/6.3, while an f/11 focal ratio now achieves a f/7. Perfect for the serious student, professional scientist and discriminating hobbyist. . Thanks Peter! This article explains the basics of how focal reducers work with an astronomy telescope. I think that the FRs made in Japan in the day may have been better. During checkout, you may also be shown other optional faster shipping choices.US Customers in Hawaii and Alaska: Free shipping applies to almost all products. Many focal reducers are meant to be used within a few millimeters of the specified working distance to achieve the best possible image results. In the 1960s, Celestrons founder, Tom Johnson, created groundbreaking new telescopes never before seen on the consumer market. Based on Test 1 and Test 2, I think there is perhaps more validity to opposing statements here in these forums that the Antares and current China-made Celestron do, indeed, have exactly the same optics just with different housings and branding. Your price: $579.00. In these equations: The combined focal length of the objective and focal reducer is given by Equation 1: For example, when d1=0, that is, the focal reducer is at the focal plane of the objective, Fcomb=Fo, so the focal reducer has no effect. GSO, for example, has a 0.75x reducer for RC scopes with a back focus of 80mm, which is usually enough room for a wide range of astronomy cameras and accessories and spacers as needed. In both cases will end with a similar tfov. This "speeds up" the optical train by reducing the focal length and magnification of the scope, requiring less time to integrate the same signal. The Buyer's Guide To Eyepieces at the top of the Eyepieces forum has a column for this spec. Just one question. Melotte 15 - First Process in PixInsight (easy! First, I wanted to compare the actual reduction provided by these competitors, as many threads here cite different ideal spacing from the reducer to eyepiece focal plane to achieve the correct f/6.3 result. Please let us know what topics you are interested in. They only publish the value of D, the working distance (sometimes called the back focus distance) and the design reduction factor MRD. Reducer Lens .7x - EdgeHD 1400 The focus barely shifts between filters and I suspect any shifts I do get are down to the filters and changes in temp. The Reduction Factor and the Amount of Reduction are inversely related. If the focal reducer is to be used for visual observation, the visual back is threaded onto the eyepiece side of the reducer, and then a star diagonal and eyepiece are installed as usual. Most refractor manufacturers such as William Optics, Tele Vue Optics, Explore Scientific, Sky-Watcher, William Optics, and Stellarvue make their own focal reducers optimized for use with their telescopes. Never used one, but read the reviews here that suggest a coating problem. Can you help me? The distances d1 andd2 can also be expressed in terms of the focal length of the focal reducer FR with the lens equation: Using Equation 2, Equation 1 can also be expressed in terms of d2: The focal reduction factor of the focal reducer depends on its focal length and its distance from the focal plane of the objective as shown by Equation 4: Again, for example, when the focal reducer is placed at the original focal plane of the objective, d1=0 and MR=1, which means there is no focal reduction. This telescope control software replaces the hand control and allows the user to remotely control their Celestron computerized telescope from their personal PC or laptop. For example, the focal reducer for an 8-inch Celestron EdgeHD telescope has a design reduction factor of 0.7x and a specified working distance (or back focus) of 105mm. However I've also read that the back focal distance on the Celestron is 105mm while the Antares is 81mm so they couldn't be identical. If you do so, you will achieve the design reduction factor. However, I noticed immediately that the Antares had a bit more of an heft to it, giving it a solid feel the Celestron didnt possess. 160K views 9 years ago This video is a complete overview of focal reducers and how they function applying to telescopes. Focal reducers for SCT, RC, and field-flattened Edge HD or ACF telescopes thread onto the back of the telescope tube with 2"-24 or 3"-28 SCT threads. Images made with my ZWO 533 camera testing both show them to be essentially the same. Place the plastic covers on the lens when not in use to reduce the dust collection. Despite never removing it no matter what I was looking at. 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. Antares' f/6.3 focal reducer provides a faster f/6.3 system for imaging or visual use when used with an f/10 SCT or other compatible telescopes. This appendix summarizes how this works based on simple equations from the book Telescope Optics by Rutten and van Venrooij. The Best Dedicated Astronomy Cameras for Beginners, Astronomik OIII 12nm CCD Filter - T-Threads, Pegasus Astro Dual Motor Focus Controller, 10 Micron 12kg (26.45lbs) Stainless Steel Counterweight- GM 2000, I would like more information regarding stock availability dates. This is the simplest way to attach your ASI121 to your telescope. The internal surfaces are blackened and glare-threaded to provide the highest contrast. For me, I was looking for, and planning to keep, the one that yielded the greatest reduction. 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) Share Customers Also Purchased Description With this telescope and this focal reducer, it does not help to move to a 2" eyepiece and a 2" diagonal as the visual view will be akin to looking through a porthole within the larger apparent field of view of the eyepiece. Optically, it consists of a four-element lens that is fully multi-coated for high contrast and resolution. If yes, what kind of focal reducers can I use? They both are great and I doubt my eyes could detect a difference in any one of them including the Japan version. Celestron Focus Motor for SCT, EdgeHD & 8" RASA, Celestron C6 0.63 reducer/flattener back focus. You currently have javascript disabled. For the best experience on our site, be sure to turn on Javascript in your browser. To further factor out my natural astigmatism (I normally wear glasses while observing), I did the tests with my regular progressive lenses, single vision glasses I use when observing, and naked eye. Is that distance D= Fo-d1=Fo-(d2/MR)? To calculate how much back focus spacing you need to add, take the thickness of the filter and divide it by 3. These scopes are compatibles with focal reducers. CEL-94245. Since 2008, Brian has taught astronomy to tens of thousands of stargazers through his websites OneMinuteAstronomer.com and CosmicPursuits.com. Scope size might influence choice as well, as a C6 might benefit from the Antares' transparency, while larger scopes might benefit from the Celestron's higher contrast. A focal reducer does just the opposite of a Barlow lens or focal extender. By using this site, you agree to our Terms of Use. However, it will not thread into William Optics accessories, and with GSO it is a hit or miss. He tested this on an 8 Celestron , I have a Celestron 6SE. Sky recognition technology that has revolutionized the manual telescope by eliminating the confusion common among beginners and enhancing the user experience for even seasoned telescope users. Focal reducers for these relatively fast ED refractors are generally for imaging only, not for visual observation. Since then, Agena has become one of the leading online retailers of telescopes and astronomical accessories worldwide. Or, when the distance of the focal reducer to the focal plane of the objective d1 equals the focal length of the focal reducer FR, the reduction factor MR = 0.5x. SKU: CEL-94245. It must be in stock at the time of Price Match for us to make a guarantee. Orders placed over the weekend will be shipped on the following Monday. As I understand it, compared to the old Meade SCT's, the ACF is already "coma corrected", so the standard Meade, Celestron etc F6.3 focal reducers are not suitable and will only worsen the images. Years ago, I bought the Antares version, and moved over to the Celestron. However, even though the imprint on the item states "Reducer / Corrector" please note that his is a reducer only. Torazz 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! The price for an item/offer must be listed and valid at the time of match. I'm going with the Celestron. None of this was offensive, nor did it interfere with views in any significant way.