Dedicated focal reducers for refractors are intended primarily for imaging, not visual observation. The design reduction factor of a focal reducer is the relative amount by which the effective focal length of the telescope is reduced when the focal reducer is used at its specified working distance or back focus. Unlike . Just one question. 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. 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). They provide 0.75x focal reducers for these telescopes that takes an f/8 instrument down to f/6. Fumbling around in the dark, fine threads might be a problem. A reducer is a set of converging (or positive) lenses that cause the light from a telescope objective to converge at a steeper angle to the focal plane as if it were coming from an objective with a faster (lower) focal ratio and a shorter focal length. Most Feather Touch focusers cost between $300-$350. 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. As a result, the smaller tube may cut into the light cone and effectively reduce the working aperture of the telescope. Most amateur astronomers are familiar with a Barlow lens (or a focal extender), a negative or diverging lens that effectively increases the focal length and the focal ratio of a telescope's objective lens. Given past experience with them, I decided not to include the Meade version in my little experiment, as I have never met one I liked from getting one of the too-short focal length models, to one with some overflow cement in the doublet, to focus difficulties with some eyepieces. For this shoot-out, I used a standard Celestron C8 with Starbright coatings. That was fun. Once installed, you can add additional accessories like T-Adapters, 1.25 Visual Back, Star Diagonal, or Off-Axis Guider. What an enjoyable read and detailed comparison. For me the Antares was a little brighter and had the least scatter by a bit so the better coatings won. The designed reduction factor (0.5x in the case of the GSO reducer example above) should be considered a rule of thumb or approximate value in most cases, rather than a very precise number. Several functions may not work. Reducer - Corrector Learn More. 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. When using the diagonal, keep the field stops of the eyepieces under 20mm. 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. I use it on my C8 SCT with a 1000d, and it seems to do everything written on the tin. Reducer Lens .7x - EdgeHD 1100 Learn More. Sign up to get exclusive deals, observing tips, and new product announcements. Try & buy if you like - usual mates rates. 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. Not one detectable iota of discernable difference. Article Agena AstroProducts, 2019. It's highly unlikely that they could be so precisely identical unless they were. JavaScript seems to be disabled in your browser. A few people have reported issues with the male SCT thread diameter on this item being a bit larger than necessary. Well done. Is that distance D= Fo-d1=Fo-(d2/MR)? The focal length and design working distance for this focal reducer were not available from the manufacturer. No experience with the Antares reducers, but I haven't personally seen a difference between Celestron and my current pair of made in Japan Meade reducers. Reproduction without permission prohibited. Since the focal length of the reducer, FR, is fixed, as d2 increases then MR decreases. And when d1 = FR, that is, when the focal reducer is placed at a distance from the focal plane of the objective that's equal to the reducer's focal length, the focal length of the combined optical system is Fo, so it acts as a 0.5x reducer. Our proprietary StarBright XLT optical coatings dramatically increase transmission, up to 97.4% on our Schmidt corrector lenses. 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. Reducer Lens .7x - EdgeHD 800 ), but stars seemed a bit tighter and their colors were richer and more dramatic. Thanks for pointing this out. OPT Product Number: AE-SCTFR specifications Warranty 2 Year Warranty Works as advertised! This should not be the case if they have their purportedly different focal lengths. 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. Looking forward to the day when I can do a shoot-out between a Japan and China Celestron, just for kicks. Sharpness is essentially the same. 800-483-6287 They usually have a 2" barrel that slides into the telescope focuser. However, doesn't fit in the telescope and even if it did wouldn't work. These scopes are compatibles with focal reducers. Newtonian reflectors will seldom be able to accommodate the in-focus travel demanded by focal reducers. Best evidence would by obtained by using a camera and evaluating the image both by eye and with a computer analysis. Edited by Tony Bonanno, 16 April 2021 - 06:44 PM. Fortunately, my neighbors are not out in their backyards at 11 pm, or they may have thought I was torturing a small mammal. A longer effective focal length leads to higher magnification with a given eyepiece for visual observers. Melotte 15 - First Process in PixInsight (easy! Depending on the design of the telescope, they may require separate focal reducers if they require focal reducers at all. I wont bother with differences in packaging, caps, etc. 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. However, the China 6.3 R/C has noticeable internal reflections that I haven't figured out yet. Nebula Filters. Again, to my surprise, there was absolutely no difference between the Celestron and Antares on any star. An eyepiece with a 27mm field stop yields a true field of 1.03 in the C6 at f/10. Advanced designs for Schmidt-Cassegrain scopes such as the Meade ACF or Celestron Edge HD have optical elements in the tube to correct for coma and field flatness. Community Forum Software by IP.BoardLicensed to: Cloudy Nights, E of San Francisco Bay and W of the Awahnee, This is not recommended for shared computers, reviews here that suggest a coating problem, Back to Celestron Computerized Telescopes, Looking for advice on first refractor and camera. 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. Explicitly designed for Celestron Schmidt-Cassegrain telescopes, this unique lens reduces your telescopes focal length and f/ ratio by 37%, turning your long focal length telescope into a fast, short focal length instrument. Much to my surprise, swapping back and forth between the two correctors using all three diagonal configurations, I also could detect absolutely no change in reduction between the two reducers. The key points are as follows: So just remember that a smaller distance (from the camera or eyepiece) means a lower amount of reduction (and vice versa). CEL-94245. Years ago, I bought the Antares version, and moved over to the Celestron. The Antares focal reducer comes in small box. For imagers using longer focal-length refractors and SCTs, especially when using smaller sensors that place less demand on the focal reducer, there are economical alternatives for focal reducers from manufacturers such as GSO, Agena, and Antares. This filter threads on to the rear cell of your Celestron or Meade SCT telescope. I've seen some older threads saying that the Celestron, Meade and Antares FRs are all the same and manufactured in the same factory. Reducer Lens .7x - EdgeHD 1400 Learn More. 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. 2023 Celestron, LLC. Focal reducers are essential optical accessories for astrophotography, electronically-assisted astronomy (EAA), and in some cases, for visual observation with long focal ratio telescopes. This also resulted in the clear aperture of the Antares being about 39-39.5mm, versus the Celestrons 41mm. That means the base of the mounting threads of the focal reducer needs to be 55mm from the camera sensor to achieve the design reduction factor, which is usually 0.8x or 0.85x. In such cases, we will be happy to take the item back as per our standard return terms. Stars in the corner of the image frame are indistinguishable between the Antares and the Celestron. Sign up to receive sale alerts, news about upcoming celestial events, and telescope tips from our experts! They both are great and I doubt my eyes could detect a difference in any one of them including the Japan version. But the smaller image circle means there is a limit to the field stop of an eyepiece that can achieve an unvignetted image. I had a Celestron, Antares and Hirsch for awhile and compared them over about a year. Many Ritchey-Chretien telescopes available today are made by GSO. If you want to save a few buck watch the classifieds on CN. But is there a difference in quality between the Antares and the Celestron or Meade focal reducers? Most focal reducers are designed to operate optimally at the working distance in the optical path to achieve their specified reduction factor, which is usually between 0.5x and 0.8x. Your mileage may vary. The easiest way to use a focal reducer is to make sure you place it at the specified working distance in front of your camera or eyepiece. They are commonly available in 1.25" and 2" threaded cells that conveniently thread into the nosepiece of a compatible camera or the barrel of an eyepiece. A focal reducer does just the opposite of a Barlow lens or focal extender. Optically, it consists of a four-element lens that is fully multi-coated for high contrast and resolution. They are designed (assuming you are referring to the f/6.3 version) for the f/10 light cone. Focal reducers for refractors are easy to use. 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. 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. It might work but it does not tell us anything about how well or to what extent the product works to correct the field of an SCT. The focal length of a focal reducer is usually measured from the rear lens surface of the reducer (and not the reducer's housing). But in the end they both do pretty much the same thing and it sounds like any performance difference is subtle. The visual back must be removed first. Perhaps not exactly- there will be some uncertainty because of manufacturing tolerances and so forth, but it will be close. Still not sure what is the right gear for you? Your eyepieces are the first accessories you should learn to use with your telescope. I'd favor the Japanese Celestron version over the others that are commercially available. These reducers can also be used for visual observing with SCT scopes with eyepieces with a field stop as large as 24-27mm. ), ASI Air Plus - Connected items are 'greyed out', Cost of ordering used equipment U.S. - Can can more than double figure, Tuthill Isostatic Mount and Star Trap Power Module. I have the Antares and have no complaints. Upon close inspection, it was clear that the housing of Antares assembled in Canada version was a little more substantial than the Celestron. If used before or beyond the working distance, unwanted image distortion may result. You also wont be unhappy spending the few extra bucks on the Celestron for the pretty orange lettering, particularly if you can pick one up used, as I did. This article explains the basics of how focal reducers work with an astronomy telescope. For the best experience on our site, be sure to turn on Javascript in your browser. Details: The item must be the identical item, brand name, size, weight, color, quantity and model number. I would pay slightly more for the Japan produced version, just because Hirsch was not bad either but sold it since I had 2 already. The new Lithium Phosphate (LiFePO4) battery chemistry has significant advantages over other battery chemistries, great for for those Astronomers on the go. riklaunim Members 559 3,445 Location: Poland Posted October 11, 2010 They are reported as identical. Here, there was a subtle difference . This fully multi-coated lens provides maximum light transmission with near full-field illumination. This is the distance at which the reducer must be placed in front of the eyepiece or camera focal plane in order to operate at the design reduction factor. Thank you so much for the informative article, I now understand better how to integrate my reducer into my system to get better performance. 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). The resultant reduction factor was measured to be 0.46x. Can you help me? There is a way to make subjective data more useful and that way is proper blind, or better still. There are also third-party vendors such as Hotech. Figure 2 shows the effective of a focal reducer on the light from a telescope objective. Our patented SkyAlign alignment technology makes setting up a computerized telescope simple, fast, and accurate. Check out our 2022 telescope buying guide here! At a significantly lower price point, the Antares is a steal, and theres no need to upgrade to the Celestron if you already have one. In terms of reduction and correction - which are what reducer/correctors are supposed to do - both are superb. Sign up for our newsletter to get exclusive deals, observing tips, and new product announcements. F6.3 Focal reducer for F/10 or higher telescopes, 43mm aperture, 4-Element, Fully Multicoated. Enter it during checkout! 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. Manish Panjwani has been an active amateur astronomer since before Halley's Comet last flew by our neighborhood. With the barrel 1.25 reducer won't focus, all I get is fuzzy snowballs. Take control of your telescope! A former wireless communications consulting engineer and management consultant to various Fortune 500 companies, Manish started Agena AstroProducts in 2003. All Rights Reserved. Again, swapping back and forth for a couple of hours on M44, M35, and several brighter stars, I examined the shape of specific stars near the edge of the field with both correctors. EclipSmart solar products feature Solar Safe filter technology providing the ultimate protection from harmful solar radiation, including both IR and UV light, and filters 99.999% of visible light. This award-winning optical system reduces visual defects like field curvature and coma, creating an ultra-flat field for pinpoint stars all the way to the edge of todays largest imaging sensors. The Reduction Factor and the Amount of Reduction are inversely related. And when used in some refractors, the field flattening is not as accurate as it is in the f/10 SCTs. I've seen some older threads saying that the Celestron, Meade and Antares FRs are all the same and manufactured in the same factory. Equation 6 & 7 item two & three does not make sense, both say increase its reduction (one should say reduce its reduction?). Normal shipments will resume on Monday, March 6, 2023. nleash the full pointing accuracy of your Celestron computerized telescope with a specialized telescope control software suite. The Celestron f/6.3 is ~150 compared to the Antares at ~70. He also holds a Ph.D. in engineering physics from McMaster University. Explore Scientific - Keys to the Universe Sale. Refractors, or SCTs with external focusers, may not have sufficient in-travel to reach focus in some configurations. 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. Read our 101 article or get in touch. This "speeds up" the optical train by reducing the focal length and magnification of the scope, requiring less time to integrate the same signal. Contiguous US Customers:All items we sell ship for free within the Contiguous US. 2. Using this same example of an 8" SCT and a 0.63x reducer, a visual observer can also enjoy brighter images and a wider field of view. 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. This means that there must be sufficient travel on the telescope focuser to make up for this. 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. If you want to use them for visual - try maybe long focal length eyepieces rather than the reducer. Who cares? Hmmm . If the reducer is placed elsewhere, at a position called the operating distance, the focal reduction factor will not be as advertised. 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. This article explained the basics of how focal reducers work with various kinds of telescopes and how their working distance affects their reduction factor, and it provided sufficient detail to help amateur astronomer choose and use the right focal reducer for a particular application.