However, these will not impact optical performance. ED stands for "extra-low dispersion," which refers to the composition and optical properties of the glass used for the lenses. With the barrel 1.25 reducer won't focus, all I get is fuzzy snowballs. If you want to save a few buck watch the classifieds on CN. Years ago, I bought the Antares version, and moved over to the Celestron. looks virtually identical, except for the lettering. I have an 8SE, and am thinking about getting a focal reducer. 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. All rights reserved. Since then, Agena has become one of the leading online retailers of telescopes and astronomical accessories worldwide. 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. But I am rusty, can you condense a bit for me please? I have the Antares and have no complaints. Figure 1 shows the relationship between the focal reduction factor MR and the position of the reducer in the optical path. Reducer Lens .7x - EdgeHD 925 Learn More. Some manufacturers will specify the working distance from the middle of the rear lens surface, and this number must then be converted into a practical working distance number by subtracting the amount by which the rear lens surface is recessed in its housing. You may need spacers or a T-adapter to ensure the correcting working distance. . He received his first telescope at the age of 5 and completed his first university course in astronomy at the age of 12, eventually receiving a master's degree in the subject. Therefore, a 55mm back focus with a filter that is 3mm thick added to the imaging train would become 56mm. The price for an item/offer must be listed and valid at the time of match. The Antares is supposed to be pretty comparable. But in the end they both do pretty much the same thing and it sounds like any performance difference is subtle. An f/6.3 reducer is designed to reduce the focal ratio of an f/10 SCT to f/6.3. So, if you have a filter that is 3mm thick, you need to add 1mm of spacing to your imaging train to retain the correct back focus. I have both the Antares and the Celestron reducers. I would not use the reducer with a 2" diagonal or eyepiece in the C6. If used before or beyond the working distance, unwanted image distortion may result, especially when using cameras with larger sensors. 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. 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. JavaScript seems to be disabled in your browser. The review is a subjective visual impression, which is interesting but not best evidence. If I had to guess, the difference is maybe 10-15 grams. If the reducer is placed elsewhere, at a position called the operating distance, the focal reduction factor will not be as advertised. When the camera sensor is placed at this distance, the reduction factor of these reducers is 0.75x. 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. I focus using a moonlight electronic focuser and focusmax. Focal Reducers - Complete Overview and Function - YouTube I'd favor the Japanese Celestron version over the others that are commercially available. However, some focal reducers can be used on other models of telescopes, but this is not always possible. Upon close inspection, it was clear that the housing of Antares assembled in Canada version was a little more substantial than the Celestron. 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. In most cases, the easiest option is to choose the focal reducer made specifically for your telescope. I don't know. Once installed, you can add additional accessories like T-Adapters, 1.25 Visual Back, Star Diagonal, or Off-Axis Guider. Read our 101 article or get in touch. Unlike SCT telescopes, Ritchey-Chretien telescopes and Celestron Edge HD or Meade ACF scopes have internal optics that provide an inherently flat field, so these telescopes require a special focal reducer than does not provide additional correction for field curvature. Celestrons FREE planetarium app is an astronomy suite that redefines how you experience the night sky. The equations in the Appendix show how this all works. It threads onto the rear cell of 5" to 16" Celestron and Meade Schmidt-Cassegrain telescopes, making it possible to have a dual focal ratio instrument without sacrificing image quality. Your price: $579.00. I've seen some older threads saying that the Celestron, Meade and Antares FRs are all the same and manufactured in the same factory. For the best experience on our site, be sure to turn on Javascript in your browser. Opticstar F6.3 Focal Reducer / Corrector. It also leads to larger (although fainter) images of extended objects like the Moon or planets for astrophotographers or visual observers. 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. Your eyepieces are the first accessories you should learn to use with your telescope. 2. Product Details 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. 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. The focal length of a focal reducer is usually measured from the rear lens surface of the reducer (and not the reducer's housing). When using the diagonal, keep the field stops of the eyepieces under 20mm. Also read the reviews here, including those at 4 stars. 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. Antares or Celestron? Upgrading the Focuser of Your Schmidt-Cassegrain Telescope - Agena Astro Celestron Nexstar+ 127 SLT, several budget plossl eyepieces, Celestron 8-24mm zoom EP and a 12.5mm illuminated double reticle EP, Svbony SV205 camera w/.5 focal reducer, Celestron SkyMaster 20x80 binos on a 40 yr old QuickSet PanHead tripod, Stellarium, Sharpcap and ManyCam on my laptop, SkyView and Nightshift on my phone and a dandy little $9 . 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. This is a. 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. Equation (4) shows the relationship between the distance d2 and the reduction factor MR. No negative issues to report. As one increases, the other decreases. In some cases, focal reducers also act as field flatteners by correcting for field curvature and coma of the objective lens. I wont bother with differences in packaging, caps, etc. The naming convention of SCT focal reducers is a little confusing. He also holds a Ph.D. in engineering physics from McMaster University. First, let's have a look at some key optical parameters are needed to understand focal reducers. This article explains the basics of how focal reducers work with an astronomy telescope. I've never found my 0.63 reducer causing CA when used with my SCT. 3. Brian Ventrudo is a writer, scientist, and astronomy educator. 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. For visual use, this means you get lower power with the same eyepiece and a wider field of view. We have corrected # (iii) after equations 6 & 7. This filter threads on to the rear cell of your Celestron or Meade SCT telescope. External Focusers for Schmidt-Cassegrain Telescopes 3.1 The Basics of SCT 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. Will not focus with the stuff I have. The more focal reduction, the further inward the focal plane will be. 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. This standard distance is a consequence of the design of DSLR cameras for which the distance of the sensor to the outer edge of the flanges is about 45 mm, while the T-ring that attaches to the flange for astrophotography is about 10mm thick. The working distance of the GSO 0.5x focal reducer with 1.25" barrel and the GSO 0.5x focal reducer with 2" barrel is about 51mm to 53mm, approximately, from the middle of the metal cell that holds the lens. Depending on the design of the telescope, they may require separate focal reducers if they require focal reducers at all. I've only used it a few times but it looks good to me. Focal Reducer, 2", 0.7X - Antares Even though they may have been slightly dimmer, galaxies were a bit easier to tease out of the urban light soup I deal with. CEL-94245. Not noticed any optical problems. For the best experience on our site, be sure to turn on Javascript in your browser. The Antares FR2-0.7X is the same 4-element f/6.3 lens system used for f/10 Schmidt-Cassegrain telescopes but in a 2" barrel threaded for standard filters. It's easy! Contiguous US Customers:All items we sell ship for free within the Contiguous US. Manish holds a Master's degree in Electrical Engineering from Virginia Tech and an MBA from the Kellogg School of Management at Northwestern University. These scopes are compatibles with focal reducers. Add a 0.63x reducer, and the brightness of extended objects increases by (1/0.63)2 = 2.5. They only publish the value of D, the working distance (sometimes called the back focus distance) and the design reduction factor MRD. 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. Field stop diameters are one of the specified specs of eyepieces. In your opinion, is the Celestron is worth the added cost ($150 vs. $90)? Given the results of Test #1, I wanted to see if there was any truth to this assumption. Sign up for OPT news, exclusive offers, and updates on the latest gear! What I do know is that the Antares and the Celestron samples that I have perform exactly the same from the center right out to the edges. The two samples I have PERFORM IDENTICALLY. Once focused it's pretty good. Melotte 15 - First Process in PixInsight (easy! 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. If the reducer is placed closer to the eyepiece or camera than the distance D, the reduction factor decreases. 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. 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"). I have Hirsch focal reducer, which is yet another clone of the Celestron reducer. Focal Reducer, 2", 0.7X. 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. I doubt there is any difference between the Antares and the Celestron except price. Reducer Lens .7x - EdgeHD 1100 Learn More. I have a Raspberry HQ camera, a Sony TV Zoom 12.5-75mm f1.8 and a Astromania 1,25" 0.5x focal reducer. I even lost track of which reducer I was using. Sign up to get exclusive deals, observing tips, and new product announcements. I really don't see any difference in the current crop except the "Meade" is usually the cheapest. Reducer Lens .7x - EdgeHD 1400 Learn More. It's highly unlikely that they could be so precisely identical unless they were. a Tele Vue Panoptic), or a Plossl eyepiece with an apparent field of view of 50 and a focal length of 32mm. Focal reducers for these relatively fast ED refractors are generally for imaging only, not for visual observation. They are reported as identical. The most significant mechanical variation, however, is the quality and precision of the threading. Steve Even though the manufacturer did not specify the working distance or focal length of this reducer, it is easy to see from this plot that this item provides its stated reduction of 0.5x when it is placed at a working distance of 51.5mm between the base of the threads on the mount and the focal plane of the eyepiece or camera. But the smaller image circle means there is a limit to the field stop of an eyepiece that can achieve an unvignetted image. 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. Both exhibited consistent reduction, identical field flattening, and edge correction properties, and both were high quality optically and mechanically. I've heard and read all kinds of things about the Antares being only a reducer and not a corrector, etc. How to Set the Correct Back Focus for Your Telescope (Guide) All additional accessories mount onto the exterior/male threads. A f/10 focal ratio now achieves a f/6.3, while an f/11 focal ratio now achieves a f/7. Hello! InternetSales@optcorp.com. This would tell us exactly how well aberrations are corrected. Check out our 2022 telescope buying guide here! 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. There will be no shipments on 3/1/2023, 3/2/2023, or 3/3/2023 (March 1st - March 3rd, 2023). Thanks. It was used strictly for imaging, not visual observing. This innovative software solves the time-consuming problem of trying to pinpoint the North Celestial Pole. These reducers can also be used for visual observing with SCT scopes with eyepieces with a field stop as large as 24-27mm. With both, using the same diagonal set-up, the exact same stars were visible at the very edge of the FOV. Housings, threads, reduction, correction, blah, blah, blah. For imagers, the main purpose of a focal reducer is to increase the brightness of the image at the focal plane. Reducer - Corrector Learn More. The Buyer's Guide To Eyepieces at the top of the Eyepieces forum has a column for this spec. They both are great and I doubt my eyes could detect a difference in any one of them including the Japan version. These 0.63x focal reducers were originally designed to optimize for an image circle to match 36mm x 24mm film or its digital equivalent for astrophotography. Images in the Celestron tended to appear ever-so-slightly dimmer (maybe? But is there a difference in quality between the Antares and the Celestron or Meade focal reducers? However, it will not thread into William Optics accessories, and with GSO it is a hit or miss. 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. They never really recovered from selling a few 15 years back with element reversed. F 6.3 focal reducer/corrector. - Discussions - Stargazers Lounge Agena's Guide to Focal Reducers - Agena Astro 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. 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 Antares 1.25" 0.5x focal reducer lens (tele-compressor) is used under the Orion brand name to thread into the nosepiece of Orion StarShoot Solar System cameras and StarShoot Deep Space Color Imaging Camera. Can these economical focal reducers from GSO and other vendors result in good images? You can adjust your cookie settings, otherwise we'll assume you're okay to continue. Imagine having two telescopes in one a long focal length instrument for lunar and planetary work and a short focal length scope for deep sky observing and astrophotography. Never used one, but read the reviews here that suggest a coating problem. Images made with my ZWO 533 camera testing both show them to be essentially the same. In some cases, focal reducers also act as field flatteners by correcting for field curvature and coma of the objective lens. I am a purely visual observer, so will evaluate for visual use only. I only have the Celestron f/6.3. 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. riklaunim Members 559 3,445 Location: Poland Posted October 11, 2010 They are reported as identical. Place the plastic covers on the lens when not in use to reduce the dust collection. For the best experience on our site, be sure to turn on Javascript in your browser. Get ready for a night of astroimaging with your mount faster than previously thought possible with All-Star Polar Alignment. 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. I use it on my C8 SCT with a 1000d, and it seems to do everything written on the tin. The Reduction Factor and the Amount of Reduction are inversely related. Hence, there is a chance that you may not be able to thread your SCT diagonal or other SCT accessory on to this reducer for these or for any other brand. Some refractors such the TeleVue Nagler-Petzval (NP), the Takahashi "FSQ", and the William Optics Redcat/WhiteCat 51 have inherently flat fields because of internal optical elements. Celestron Focus Motor for SCT, EdgeHD & 8" RASA, Celestron C6 0.63 reducer/flattener back focus. They usually have a 2" barrel that slides into the telescope focuser. The same illumination you have at the edge of a 27mm field, the C8 has at the edge of a 38mm field. Weasner's Meade and Antares Focal Reducers Review 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. 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. Since the Celestron and Antares are supposed to have different focal lengths and spacing specs, I expected different results. Yet, the Antares still easily and fully threaded without any hitches. Thank you so much for the informative article, I now understand better how to integrate my reducer into my system to get better performance. 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. One of the most important factors in a telescope is its transmissionthe percentage of light that reaches the focal plane. It features a standard male SCT thread (2" OD, 24 TPI) on one side and a standard SCT female thread on the other. Does anyone have any experience with the Celestron and Antares focal reducers? The camera side of the focal reducer is threaded for a T-adapter with wide M48 threads, or in some cases, with smaller M42 threads. 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. There are many different types of focal reducers and they all effect. Keep in mind that these differences were very subtle, and could be due to normal variations in coatings among different runs, and not necessarily unique to the brands. Wonder how they would stack up with a Japanese 6.3. I have had the Japan unit on the back of my C5 since 1994 or thereabouts. For example, an 8" SCT without a focal reducer has an illuminated field of 38mm at 50% fall-off. Celestron or Antares? Maybe I got a lemon. Now It only focuses near things, like some kind of macro zoom. It's usually specified in millimeters. Refractors, or SCTs with external focusers, may not have sufficient in-travel to reach focus in some configurations. No difference. It was also a little brighter in the center of the field with subtle darkening in the outer 20% or so. The reducer fits all Meade and Celestron . The telescope side of the barrel is often threaded with an M48 x 0.75 thread for standard 2" astronomy filters. Obviously bright objects like Jupiter or The Moon show the reflections. The new Lithium Phosphate (LiFePO4) battery chemistry has significant advantages over other battery chemistries, great for for those Astronomers on the go. Increase that distance, and greater reduction results and visa versa. It covers the basic optics and design specifications of a focal reducer, and goes through some practical factors to consider when selecting and using a focal reducer. Equation 6 & 7 item two & three does not make sense, both say increase its reduction (one should say reduce its reduction?). 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. This focal reducer is made to attach to the rear cell of Schmidt-Cassegrain or Maksutov-Cassegrain telescopes. Celestrons aplanatic EdgeHD optics revolutionized astroimaging. If you place your camera at a different working distance, you will get a different reduction factor and perhaps unwanted distortion in the image. But in the Japan version I have never noticed any anomaly like the ghosting in the China R/C.
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