That includes, for example, a 1.25" eyepiece with an apparent field of view of 68 and a focal length of 24mm (eg. Both exhibited consistent reduction, identical field flattening, and edge correction properties, and both were high quality optically and mechanically. All rights reserved. This innovative software solves the time-consuming problem of trying to pinpoint the North Celestial Pole. 160K views 9 years ago This video is a complete overview of focal reducers and how they function applying to telescopes. Nowadays I tend to use the Celestron more with my refractors for imaging and viewing. They never really recovered from selling a few 15 years back with element reversed. Can these economical focal reducers from GSO and other vendors result in good images? As another example,GSO makes focal reducers for their line of Ritchey-Chretien imaging telescopes. I was originally hoping to do this with a made in Japan Celestron, but ended up with a newer China version but thats probably better in the end since it is the version now available, with the Japan ones rarer and only available used. OPT Product Number: AE-SCTFR specifications Warranty 2 Year Warranty Works as advertised! When you said, "in some cases" a focal reducer also works as a flattener/corrector, are you saying that not all focal reducers are flatteners/corrector? The threads were similar on the eyepiece end, but a bit smoother. The female end attaches to the rear cell of the telescope. If used with other f/ratios, the field flattening characteristic may be unpredictable. 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. The Reducer/Corrector can also be used for terrestrial digiscoping. Blue Fireball M42 T/T2 Thread Camera Adapter for Prime Focus Photography - 2" # P-06, Celestron T-Ring for Canon EOS Camera # 93419, GSO 2" Crayford Focuser for SCTs - Dual Speed, Length of male SCT thread = 5mm (0.2") but this is preceded by an unthreaded part on the eyepiece side making the total length = 8.8mm (0.35"), Length of female SCT thread = 7.5mm (0.3"). The brightness, shape, and distortion of specific stars in the exact same position at the edge of the field was precisely identical in both reducers. Such an image circle is still large enough to encompass the relatively large sensor of many deep-sky astronomy cameras. ), but stars seemed a bit tighter and their colors were richer and more dramatic. In your opinion, is the Celestron is worth the added cost ($150 vs. $90)? Article Agena AstroProducts, 2019. Sign up for our newsletter to get exclusive deals, observing tips, and new product announcements. He tested this on an 8 Celestron , I have a Celestron 6SE. Manish holds a Master's degree in Electrical Engineering from Virginia Tech and an MBA from the Kellogg School of Management at Northwestern University. If I had to go out on a very thick limb, I would have to say that these two reducers/correctors are, indeed, identical the exact same glass in slightly different housings with different lettering. Focal Reducer for SCT - ACF - Stargazers Lounge 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. In such cases, we will be happy to take the item back as per our standard return terms. The nominal design reduction factor of these reducers is typically 0.5x. It's highly unlikely that they could be so precisely identical unless they were. When the camera sensor is placed at this distance, the reduction factor of these reducers is 0.75x. I have the Antares and am not unhappy with it, but for AP I would want more back focal distance if those numbers are accurate. A longer effective focal length leads to higher magnification with a given eyepiece for visual observers. 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. For this test, I used a single configuration R/C, Click-lock, and 1.25 diagonal with the adapter. One of the most important factors in a telescope is its transmissionthe percentage of light that reaches the focal plane. This is very impressive performance given how hard this problem is to mitigate in general. Reducer Lens .7x - EdgeHD 800 In some cases, focal reducers also act as field flatteners by correcting for field curvature and coma of the objective lens. Again, to my surprise, there was absolutely no difference between the Celestron and Antares on any star. Steve Please let us know what topics you are interested in. Focal reducers for refractors with focal ratio of f/7 to f/9, roughly, have a design reduction factor of about 0.75x to 0.8x and produce a flat field by correcting for the curvature of the objective lens. 0.63x Starizona Focal Reducer for SCTs- Awesome Astrophotography Thanks guys, appreciate the feedback. I've looked through one from Meade and first impression was that it was like the Celestron version. On the trail, at the job site, in the classroom, or simply sitting at home relaxing the Celestron Elements ThermoTank 3 will keep your hands toasty. Since 2008, Brian has taught astronomy to tens of thousands of stargazers through his websites OneMinuteAstronomer.com and CosmicPursuits.com. I am new to these optic topics, and I want to ask you what happens with Masutov like SW or Celestron 4 or 7 inches. No difference. Weasner's Meade and Antares Focal Reducers Review Wonder how they would stack up with a Japanese 6.3. What an enjoyable read and detailed comparison. This part is no longer in production, but it is sometimes available used and may be used with cameras with smaller sensors. 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 new Lithium Phosphate (LiFePO4) battery chemistry has significant advantages over other battery chemistries, great for for those Astronomers on the go. 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). In terms of reduction and correction which are what reducer/correctors are supposed to do both are superb. Figure 2 shows the effective of a focal reducer on the light from a telescope objective. Using an eyepiece with a 27mm field stop with the reducer will illuminate the edge the same as using an eyepieces with a 42.9mm field stop without it. You need to be a member in order to leave a comment. 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. Optically, it consists of a four-element lens that is fully multi-coated for high contrast and resolution. Copyright 2003-2022 Agena AstroProducts. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. 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. The telescope side of the barrel is often threaded with an M48 x 0.75 thread for standard 2" astronomy filters. 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. The stock Celestron visualback is just under 2 long. Thank you so much for the informative article, I now understand better how to integrate my reducer into my system to get better performance. Torazz I must admit, as well, that I no longer place a lot of stock in the notion that Chinese optics are inferior to Japanese or Taiwanese any longer, as manufacturing technology has really leveled the playing field today, with most Chinese optics being excellent. A useful thing to know is how far from the objective lens (for a refractor) is the focal reducer located. Focal reducers for these relatively fast ED refractors are generally for imaging only, not for visual observation. Focal reducers for many SCTs and their flat-field equivalents usually have a back-focus distance of 105mm. Performance wise what differences might there be using the reducer on a smaller scope. Back-Focus 101: DSLR Cameras & the Celestron f/6.3 Reducer - YouTube 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. 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. 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. Have a promo code? All Rights Reserved. For me, I was looking for, and planning to keep, the one that yielded the greatest reduction. Read our guide! Most Feather Touch focusers cost between $300-$350. JavaScript seems to be disabled in your browser. However, manufacturers virtually never provide this specification. The author finds differences in throughput and color balance, but then says he thinks the lenses are identical and he reaches his conclusions based on very long observing session. Reducer Lens .7x - EdgeHD 1100 Learn More. You don't need to follow these equations to use a focal reducer, but they do show how the reduction factor changes with the placement of the reducer. There may have been an almost imperceptible difference, but the Antares and Celestron were producing precisely the same reduction. 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. Field stop diameters are one of the specified specs of eyepieces. Well done. 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. if the illuminated field is 27mm wide without the reducer, it will be 27 x 0.63 = 17mm with it in place. Sign up for our newsletter to get exclusive deals, observing tips, and new product announcements. No idea what the issue is. Completely stuck, completely frustrated. From the SkyProdigy, a telescope so smart it can align itself, to our high-performance EdgeHD optical system, weve revolutionized the hobby of astronomy for beginners and advanced amateurs alike. Antares F/6.3 SCT Focal Reducer | OPT Telescopes These scopes are compatibles with focal reducers. The EdgeHD .7x Focal Reducer Lens makes your EdgeHD 1100 one full F-Stop faster than f/10, reducing your exposure time by half to capture the same brightness of object . For me the Antares was a little brighter and had the least scatter by a bit so the better coatings won. This filter threads on to the rear cell of your Celestron or Meade SCT telescope. Fortunately, my neighbors are not out in their backyards at 11 pm, or they may have thought I was torturing a small mammal. However, doesn't fit in the telescope and even if it did wouldn't work. External Focusers for Schmidt-Cassegrain Telescopes 3.1 The Basics of SCT Threads Great report and verifies what I had thought all along, Fortunately, my neighbors are not out in their backyards at 11 pm, or they may have thought I was torturing a small mammal. Dedicated focal reducers for refractors are intended primarily for imaging, not visual observation. Some are available in 1.25" barrel format but with C threads. As a Barlow's magnification increases with increasing distance from the Barlow, a focal reducer's reduction increases with increasing distance from the reducer. Thanks. If you place your camera at a different working distance, you will get a different reduction factor and perhaps unwanted distortion in the image. 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. But in the Japan version I have never noticed any anomaly like the ghosting in the China R/C. 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. InternetSales@optcorp.com, 800-483-6287 Try & buy if you like - usual mates rates.