The equations and argument in the Appendix of this article shows the relationship between the working distance and the reduction factor. For Ritchey-Chretien telescopes such as those manufactured by GSO, there are also dedicated focal reducers with a reduction factor of 0.7x to 0.8x. 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. Unlike . No rainchecks will be issued for items out of stock at OPTcorp.com to match a competitor's price. Description. Celestron or Antares? For these items, please contact us to obtain a shipping quote before you check out using the online shopping cart.International Customers:Free shipping does not apply to international orders. One focal reducer will not achieve optimum results with all types of telescopes, so there is no universal' focal reducer. looks virtually identical, except for the lettering. This should not be the case if they have their purportedly different focal lengths. Please note, orders placed after 10am on 2/28/2023 will be delayed. This is very impressive performance given how hard this problem is to mitigate in general. I've never found my 0.63 reducer causing CA when used with my SCT. Reducer - Corrector Learn More. A longer effective focal length leads to higher magnification with a given eyepiece for visual observers. None of this was offensive, nor did it interfere with views in any significant way. He tested this on an 8 Celestron , I have a Celestron 6SE. Any comments gratefully received. You need to be a member in order to leave a comment. Contiguous US Customers:All items we sell ship for free within the Contiguous US. Therefore, a 55mm back focus with a filter that is 3mm thick added to the imaging train would become 56mm. In both cases will end with a similar tfov. 160K views 9 years ago This video is a complete overview of focal reducers and how they function applying to telescopes. Generally, views through the Antares seemed a little more transparent and brighter. We only send interesting emails and will never sell your data. Fortunately, my neighbors are not out in their backyards at 11 pm, or they may have thought I was torturing a small mammal. External Focusers for Schmidt-Cassegrain Telescopes 3.1 The Basics of SCT Threads Add a 0.63x reducer, and the brightness of extended objects increases by (1/0.63)2 = 2.5. However, some focal reducers can be used over a wider range of working distances, especially those with simpler optical design, and especially when used with cameras with smaller sensors. This means that there must be sufficient travel on the telescope focuser to make up for this. You cannot, for example, use a 0.63x focal reducer intended for a standard Celestron or Meade SCT and use it on a Celestron Edge HD or a Meade ACF. It was also a little brighter in the center of the field with subtle darkening in the outer 20% or so. 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. How about for visual observers? How does it look thats what matters. Does anyone have any experience with the Celestron and Antares focal reducers? I have Hirsch focal reducer, which is yet another clone of the Celestron reducer. 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. During a twenty-year scientific career, he developed laser systems to detect molecules found in interstellar space and planetary atmospheres, and leveraged his expertise to create laser technology for optical communications networks. Better images are also obtained when using these focal reducers at a reduction factor of 0.5x 0.8x, approximately. Thanks for pointing this out. In some cases, focal reducers also act as field flatteners by correcting for field curvature and coma of the objective lens. Can these economical focal reducers from GSO and other vendors result in good images? No retailers currently carry this product. One problem with getting opinions is that most of use do not have both reducers or have never done a side by side comparison. This would tell us exactly how well aberrations are corrected. These RC reducers cannot be used with other types of telescopes. 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 for the extremely valuable article. The most commonly available focal reducers for SCTs are the f/6.3 reducers from Celestron and a similar f/6.3 focal reducer from Meade. Celestron is considered better in terms of QA, less likely to come with free dust, hair or fingerprint. Figure 7 shows an example of an image of the Dumbbell Nebula taken with a 1.25" GSO focal reducer at a reduction factor of 0.63x with an 85mm f/7 refractor and a QHY5III-290M camera with a sensor with a 6.4mm diagonal. The Buyer's Guide To Eyepieces at the top of the Eyepieces forum has a column for this spec. Oceanside Photo & Telescope wants our customers to shop with confidence knowing that you will always get the best deal available. Your eyepieces are the first accessories you should learn to use with your telescope. Wow, that is a very detailed discussion! That said any comparison reviews are helpful. 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. 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. Please re-enable javascript to access full functionality. Shipping will be via the cheapest shipping method which will vary depending on the items in your order. 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. I found both to be very good. 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. 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. We will be glad to help. To test this, I used three set-ups: 1. Also, the focusers of most Newtonians do not have enough in-travel to accommodate a focal reducer. Reducer Lens .7x - EdgeHD 925 Learn More. JavaScript seems to be disabled in your browser. It's important to match the back focus to within a millimeter or two to get an optimal image, especially with cameras with larger sensors. High power views will provide flatter fields all the way to the edge, both visually and photographically. It seems right to put some distance between the camera and the focal reducer, right? For the best experience on our site, be sure to turn on Javascript in your browser. Now It only focuses near things, like some kind of macro zoom. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. 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. The most significant mechanical variation, however, is the quality and precision of the threading. All rights reserved. However, even though the imprint on the item states "Reducer / Corrector" please note that his is a reducer only. Melotte 15 - First Process in PixInsight (easy! Meade does not make an equivalent line of focal reducers for the ACF scopes, although some models of Meade ACF are already at f/8, faster than the f/10 ratio of Celestron Edge HD scopes. The working distance (backfocus) of the Celestron f/6.3 reducer is specified to be 105mm from the base of the male SCT thread on the camera side. Enter it during checkout! The same illumination you have at the edge of a 27mm field, the C8 has at the edge of a 38mm field. I would not use the reducer with a 2" diagonal or eyepiece in the C6. The lens that the ZWO comes with give a perfect wide angle image of what is in front of it. Designed distancing using the reducer with a 1.25 visual back and 1.25 Televue mirror diagonal; Whereas the Celestron threaded smoothly onto the scope, the Antares chattered and squeaked a bit more so when being removed. In this case, d2 = FR/2, which means the back of the focal reducer is located at a distance FR/2 from the camera or eyepiece. Celestron Focus Motor for SCT, EdgeHD & 8" RASA, Celestron C6 0.63 reducer/flattener back focus. Celestron Solar Safe filter technology is GUARANTEED SAFE for direct solar observation and has been independently tested by SAI Global Assurance Services. I have the Antares and have no complaints. This filter threads on to the rear cell of your Celestron or Meade SCT telescope. Because most modern Newtonians already have relatively fast focal ratios, these telescopes do not usually use focal reducers. If a stronger level of focal reduction is used, say 0.5x, then the image circle may be too small to fill the sensor of larger cameras. Nowadays I tend to use the Celestron more with my refractors for imaging and viewing. No results, please adjust your filters. 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. In such cases, we will be happy to take the item back as per our standard return terms. For me, I was looking for, and planning to keep, the one that yielded the greatest reduction. 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! I only have the Celestron f/6.3. Easy solution found a very tiny dab of super lube on the threads and all was well and quiet. Thanks guys, I'm trying to get my ZWO ASI120MC-S to work with my 90mm Meade. 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. Bear in mind you can't squeeze blood out of a turnip, i.e. CPWI has an extensive object database, employs PointXP mount modeling, and more. 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. Perfect for the serious student, professional scientist and discriminating hobbyist. JavaScript seems to be disabled in your browser. At least these two units I tested make the answer - whatever. Again, to my surprise, there was absolutely no difference between the Celestron and Antares on any star. if the illuminated field is 27mm wide without the reducer, it will be 27 x 0.63 = 17mm with it in place. Celestron makes a series of focal reducers for the Edge HD line that are matched to the 8", 9.25", 11", and 14" apertures of these scopes. The visual back must be removed first. Sign up for our newsletter to get exclusive deals, observing tips, and new product announcements. 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. 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. Another factor to consider: focal reducers also increase the angle at which light approaches the focal plane. Reviews. Observing the microscopic world has never been easier! They never really recovered from selling a few 15 years back with element reversed. I had a Celestron, Antares and Hirsch for awhile and compared them over about a year. October 11, 2010 in Discussions - Scopes / Whole setups. However, doesn't fit in the telescope and even if it did wouldn't work. Rather than a direct side-by-side, I swapped the reducers so that I was using them on the exact same, well-collimated instrument. Optically, it consists of a four-element lens that is fully multi-coated for high contrast and resolution. 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. Optically, it consists of a four-element lens that is fully multi-coated for high contrast and resolution. Also read the reviews here, including those at 4 stars. Does anyone know if the Antares 4000 focal reducer is as good as the Celestron focal reducer. 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. I really don't see any difference in the current crop except the "Meade" is usually the cheapest. I use the Celestron version and it seems OK for both visual and imaging. Have always disliked the crude, noisy SCT threads, but I get it. The Reduction Factor and the Amount of Reduction are inversely related. 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. . The distance d2, which measures the position of the new focal plane of the objective from the back of the focal reducer is given by Equation 5: In these equations, d1, d2, and MR are all variables that depend on each other through Equations 2 and 4. Fumbling around in the dark, fine threads might be a problem. I was going to measure the difference in grams, but my lovely wife caught me trying to use her precious, high-tech kitchen scale for the cause, and put the kibosh on it. These reducers can also be used for visual observing with SCT scopes with eyepieces with a field stop as large as 24-27mm. An f/6.3 reducer is designed to reduce the focal ratio of an f/10 SCT to f/6.3. There are also third-party vendors such as Hotech. Reducer Lens .7x - EdgeHD 800 All Rights Reserved. They only publish the value of D, the working distance (sometimes called the back focus distance) and the design reduction factor MRD.
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