Telescope back focus calculator online. Aug 18, 2023 · This adds up to the standard 55mm.

Telescope back focus calculator online astrophoto. Image Circle will vary with scope design. in pro observatories). In the beginning of my astrophotography journey, i just went with the standard 55mm which seems to be a standard measurement for more or less every OEM corrector/reducer. Oh, I did some years back, upgrade the manual focuser with the Peterson EZ Focus product. Then, add up the spacing distances of all of your pieces in your optical train to your sensor. 3mm (black), 0. Set that, then decide on a sensible focus position. Specifically i am planning to use the SkyWatcher EVOSTAR 72ED DS PRO Jul 6, 2017 · What is Backfocus? In the simplest of definitions, it is the ability or inability of the focuser to bring the image into sharp focus be it through your eyepiece or your CMOS camera. Telescope Calculator Required Numbers SC 3. Getting the proper back-focus for your imaging camera is a vital step in getting the best data possible out of your telescope imaging/research rig. 67” and 2”. Cassegra in Equations for description of terms in drawing: primary focus intercept point (p), secondary to Cassegrain focus (p ·), primary focal length (F), secondary magnification (X ), back focus (b), mirror separation (B), secondary clear aperture (c), final image size (I), primary diameter (D). 2) A lens or telescope has Backfocus requirements in millimeters. Oct 7, 2021 · 11 Ways to Fix Telescope Focus Problems Start with a low magnification. Here back on Earth we are seldom diffraction limited. Essentially my understand is that the back focus is the distance from the last optic element to the sensor. Oct 30, 2005 · The two equations agree for focal lengths down to around 50mm, then they start to diverge. e. So, now we know what 17. Digital Landscape Photography: In the Footsteps of Ansel Adams and the Masters, Michael Frye, 2010. You need to place your camera (or eyepiece) at this point to see an in-focus image. Focal Length Calculator. Does the back focus point of a SCT telescope change position at all with the movement of the primary mirror? Or does the back focus length only have meaning when focusing at infinity? Thanks jk Jan 7, 2021 · If the eyepiece connects in the middle or in the upper half of the body of the telescope (like most reflectors/Newtonians), your telescope has a low back focus and you might not benefit much from a binoviewer. On Amazon you can also search the Customer questions & answers, since other customers may have asked about the focal length. Formulae used for these calculators Apr 28, 2020 · Getting the proper back-focus for your imaging camera is a vital step in getting the best data possible out of your telescope imaging/research rig. Your camera and t-ring will likely use 2". 4 mm of aperture and 2,794 mm focal length at f/10. • Prime focus magnification: 29x • Re-focus distance: 1. Its purpose is helping beginners to get an idea of what they can see in an amateur Sep 9, 2014 · Page 1 of 2 - Considering filter thickness when calculating backfocus - posted in Experienced Deep Sky Imaging: Im confusing myself here and could use some clarification. With a standard Canon DSLR, the sensor is recessed much further back to make room for the flip mirror, this is why a Canon T-adaptor is so much thinner, but the optical length is the same 55mm. Calculator Instructions. Some telescopes use extra lenses and/or mirrors to create a long effective focal length in a short tube. Oct 12, 2022 · Page 1 of 2 - Correct Backfocus for Celestron C8 and ZWO ASI585MC Camera - posted in Major & Minor Planetary Imaging: I have looked around but couldnt find specifically what I was looking for. It is primarily oriented to the Newtonian reflecting telescope, which is what most first time telescope makers build, although many sections of it are applicable to other types of telescopes. The diameter is the same as their regular Astronomical telescope, but the tube is extended so near focus is a matter of feet instead of Yards or meters. You can achieve this distance by combining filter holders, extension rings, adapters, filter wheels, OAGs, etc. So if I calculate the camera Back focus plus the 10mm from the T-Ring plus the FF I get 114mm. The CFZ is related to the telescope angular separation under diffraction limited conditions. Some are examples from my telescope, a C11 SCT with 279. 3 mm farther back than would be required to focus on a celestial object at practical infinity. However, if only 1. Apr 9, 2017 · As I am currently translating my Stelvision personnal website, I am glad to present you the English version of an online tool which is beginning to be well known in France: a telescope simulator & eyepiece set calculator. 3 SCT focal reducer/corrector. We can use a RASA scope for example or an SCT as an example, where you have a primary mirror re-pointing light to a front window or secondary mirror, then to an astro camera. Jun 20, 2018 · Telescope eyepieces focus over a range of about 2" (2" size) or 1. 93" • Limiting magnitude: 13. In a nut shell it is the smallest angle for which two star diffraction patterns (Airy disks) can Telescope used like telephoto lens; Field Angle = (Image Diameter ÷ Telescope Focal Length) x 57. (SVBONY Fixed Diameter 65-100mm)If you are not interested in buying a Bahtinov mask, there are several free tools available online to help you make your own Bahtinov mask, including tutorial videos that help you build the correct size for your telescope or lens. Jun 26, 2022 · A refractor has a fixed focal length, the distance from objective to the focal planed, and no back focus requirement. Calculators already have sample data in them. Oct 27, 2022 · Refracting telescopes are the easiest and quickest telescopes to focus. Proper back focus depends on your telescope, camera, and any additional optics. Since many telescope makers want to compare two designs in order to decide on the right telescope for them, this calculator computes parameters for two Field of View Calculator Test different telescope, camera & eyepiece combinations. But what if your telescope has s different back focus length? Can you come within a millimeter or two and still get an acceptable Sep 23, 2023 · However, finding an online calculator to do the calculations quickly is easier. I get a lot of questions about this. 25" but doesn't cover the full 2"). 5" of back focus—sufficient for catadioptric telescopes (Schmidt-Cassegrain and Maksutov-Cassegrain), as well as a good number of refractor telescopes. Your eyepieces are the first accessories you should learn to use with your telescope. As with all flatteners, these produce optimal results when the imaging plane is a specific distance from the flattener. In this article, we’ll discuss why back focus distance is so important, all the factors you need to consider for back focus distance, and how to use adapters and spacers to get the perfect back focus distance. 56mm • Light area: 122. 57142857142 So, if this is correct, the image circle at About this calculator. The distance between the rear of your telescope and the point where light is focussed is known as back-focus measurements. There is also many times a debate of what the proper back focus distance actually should May 14, 2021 · a couple things that might also help. 3” adapter for ESATTO 2" allows you to connect the ESATTO 2" to Celestron SCT (11" and 14") and EdgeHD (925, 1100, and 1400) models. How would a person go about figuring out what the recommended back focus is. May 31, 2024 · As you can see, the magnification of the telescope gets greater when the focal length of the objective increases or when the eyepiece's focal length decreases. Then turn knob counter-clockwise to push the primary mirror forward and push the focal point further out the back . I hope my questions make sense)? Ive got a micro four thirds camera and a 130mm f/5 newt. 4km All values are approximate and purely theoretical under ideal observation conditions. Is the correct backfocus for the ASI585MC Camera using the Celestron C8 scope 55mm. 0 • Moon features: >5. Our calculator, at typical seeing of 2-4”, uses the Nyquist formula of 1/2 and the 1/3 to stop stars becoming square so the optimal range is between 0. Hence the possible need for an extension tube. Focal reducers also reduce back focus and, when used for prime-focus photography with Nov 4, 2012 · Take control of your telescope! Download the Celestron PWI Telescope Control Software. In the later years, I have been more and Focal Length Calculator. CCD Resolution Calculator. Jul 16, 2021 · The back focus length has been extended to 80-mm to allow for additional accessories to be placed in the optical path. That's the reason why the highest-powered telescopes are such monsters with huge mirrors. In a typical Cassegrain or Schmidt-Cassegrain telescope, focus is achieved by moving the primary mirror back and forth (typical amateur telescopes), or the secondary mirror back and forth (larger telescopes, e. This makes it more difficult to get the telescope’s focus dialed incorrectly, so always start with low power (low magnification) and work your way up slowly. Attaching the Askar field-flattener/reducer will turn this telescope into a wider and much faster instrument, more info on Oct 1, 2023 · Telescope focal lengths vary widely, depending on the type and design. My Aug 23, 2016 · Backfocus, putting it together, how? - posted in Beginning Deep Sky Imaging: Hi all, I ordered an APM 107/700mm refractor and TS 2. In this article, we will explain what how to focus a telescope actually means, how focusers work, and why it’s important. So I use the Explore Scientific 80ED telescope which has a back focus of 165mm. It's important to Feb 16, 2019 · If you’re shopping for a telescope online, the focal length should be listed somewhere in the specs (if not the description). This is probably t Apr 4, 2022 · When used to connect to M48 tubes, this adapter consumes an additional 4 mm of back focus. In this episode of back-focus 101, I show how to obtain proper back-focus on the Petzval, using the William Optics RedCat51 as an example. 5mm of that. 5" (1. 5 Field Flattener claiming this: Focal lenghts / back focus: < 500 mm: 106 mm 510-600 mm: 101 mm 610-700 mm: 96 mm 710-800 mm: 91 mm 810-950 mm: 88 mm > 1000 mm: 87 mm I need to attach my nikon camera to it, can someone explain What is telescope back focuswhy is it importantand how do you set it correctly?Having the proper back focus between your telescope and camera is critic Flange back focus distance = 44 mm T-ring adapter for EF/EF-S mount back focus = 8 mm. SkyPortal App. . This is known as the Rayleigh’s limit. From the drop-down menu, select the appropriate measurement units. Visual Mode Imaging Mode Binocular Mode Choose Object Understanding back focus is essential for capturing sharp and stunning astrophotography images. If the threads of your telescope is M42 or M48, then we recommend you DIY the relative adapters or choose the 2” EFW. In summary, we are using Nyquist as a starting point, with a slight tweak, because we are typically sampling very small, circular, stars. If a telescope gives you 100mm of "backfocus" distance (again the distance from the shoulder of the focuser at the lowest point, back to the focal plane), and the total light path distance to the sensor from the beginning of the optical train is 120mm, you won't be able to reach focus. 5 mm of back focus with the ASI533MC Pro camera. Im not entirely sure that I got an answer, but still r. An example is Questars 90mm Close up lens. Enter your GoldFocus mask, telescope, camera, and imaging data in the boxes below. That's why our experts have created this solar calculator to help make things easier. This is because when people talk about back focus, they often mean different things: the back focus on a telescope, the required back focus for accessories such as field flatteners, or the flange focal distance of DSLRs and astro cameras. Back-focus in astrophotography. Dec 26, 2021 · I do not like using my fingers to achieve fine focus on the manual focus knob, so that is why I use the Meade’s micro focuser, using the hand controller, that came with the LX200GPS. This calculator follows the standard sign convention for the optical radius of curvature where if the vertex of a surface lies to the left of the center of curvature the radius of curvature is positive, and if the vertex lies to the right of the center of curvature the radius of curvature is negative. Nov 20, 2021 · Understanding back focus - posted in Beginning Deep Sky Imaging: Im upgrading to a ZWO 1600MM and Im trying to understand what Id need to achieve the correct back focus for my setup - but Im struggling to fully understand what it is - or more specifically why its so important. Read our guide! Aug 31, 2017 · In most telescopes the focal length is roughly equal to the length of the tube. Formula: ( Pixel Size / Telescope Focal Length ) X 206. [PDF] Exposure time calculator for IFOSC and sky background estimation. Using Telescope Eyepieces. Mar 10, 2021 · Help me understand Backfocus in plain English - posted in Experienced Deep Sky Imaging: These are the two facets to Backfocus as I understand (or misunderstand) them today. pdf) which I think is a very good work. The telescope can be used with full-frame cameras, and the built-in reducer/flattener means you do not need to calculate the back focus. There are five connection solutions for ASI6200MM Pro. Combining accessories can also cause back focus problems. The camera kit takes up 63. Calculate, plan, and optimize your imaging sessions with ease. Aperture: Calculate the focal ratio of your telescope. Additionally, the beam quality parameter can be specified if the beam deviates from an ideal Gaussian. Most telescopes have an external focusing device that physically shifts the eyepiece or camera back and forth along the optical axis CCD Calculators Useful calculators and formulae. Apr 29, 2023 · Collimation is nothing more than getting all the optics, mirrors, and other mechanical features in your telescope aligned so you get the optimal focus of an image. I wanted to take a look at back focus to make sure I have things setup correctly for optimal imaging, and because some of the Shop Telescopes, Accessories & Mounts at High Point Scientific. I believe the correct back focus for this unit is Celestron RASA Back Focus - How to Calculate Back Focus - What are my Options. 5mm extender and the M54-M48 21mm extender. based on time/where you are. g. 67 = 2 / 3, 2 = 4 / 2). I have seen some pictures of ZWO cameras on a C8 but they are all of the place with some that look very long, maybe Apr 24, 2024 · Just how precise does back focus have to be? - posted in Beginning Deep Sky Imaging: I understand the concept of back focus, and see that most refractors require 55mm of it for proper focus, and ZWO sets you up with proper spacing on its cameras for that distance. Just about all scopes will cover the field of a 1. TripleSpec Slit Viewer Focus Calculator TripleSpec is a fixed configuration Near Infrared Spectrograph. I have recently acquired a few bits of kit that will be used with my 85 C8, and I want to make sure that I am following the correct procedure with them. Calculate the focal length of your telescope. :-) The telescope acts as camera lens at a fixed focal-length. 4mm which you can set with the built in scale, or more accurately with callipers. Mar 25, 2015 · Back focus on Explore Scientific 127 APO - posted in Refractors : I just got a new ES 127 APO. It seems it lacks about an extra inch of back focus to bring most of my eyepieces to focus. Back Focus of Telescopes and Guide Scopes 2. 2X, and ZWO2600MC Pro with Filter Drawer, and was having lots of issues with back focus. Oct 4, 2020 · Celestron's EdgeHD product line features an integrated field flattener. does anyone have this same problem and does anyone know what distance there should be between my dslr and telescope? it surely must be more than 55mm since that is already the size of the field Sep 17, 2016 · Male thread - M42X0. 5 mm Aug 27, 2021 · How do you measure your back focus? - posted in Equipment (No astrophotography): I have always wondered how you guys calculate or work out the right back focus distance in your setups. 5mm and when off it is 12. Feb 2, 2021 · Back focus calculation - posted in Beginning Deep Sky Imaging: Hello everyone, So i think decided on what telescope and camera i should get for AP but i dont know if theyre compatible right out of the box. Confusion about back focus often arises because it refers to two different ideas: the available back focus of a telescope, and the required or recommended back focus of corrective optical accessories like focal reducers, field flatteners, and coma correctors. If you like, we can do all the work for you for free. Field of View Calculator Test different telescope, camera & eyepiece combinations. The specific focal length of a telescope can significantly impact its magnification and field of view for astronomical observations. 5mm — the difference being the 5mm thickness of the tilt adjustment ring. 142857142857×158=22. Jul 20, 2021 · 2. My field flattener is the 2“ from Skywatcher and has a back focus of 55mm and my T-Ring is 15mm. µm. pdf Apr 9, 2017 · Page 1 of 3 - Telescope Simulator & Eyepiece Set Calculator - posted in Eyepieces: Hi all ! As I am currently translating my Stelvision personnal website, I am glad to present you the English version of an online tool which is beginning to be well known in France: a telescope simulator & eyepiece set calculator. The back focus for your telescope imaging train is the measured distance from the last optical component at the back of the telescope, whether it’s a coma corrector or field flattner / focal reducer and the focal plane of the telescope where the camera detector is. In this video, I’ll break down what back focus is, why it mat Jan 24, 2022 · Achieving Optimum Back Focus Distance - posted in Beginning Deep Sky Imaging: Im working to better understand back focus and how to achieve the optimum back focus distance of a particular imaging train. Does this happen with yours? What do you do about it? If I dont fully seat my 2 diagonal and eyepiece I can get to focus, but that doesnt make me very happy. Written by Dylan O'Donnell. 1) The camera has a Backfocus measurement. Celestron’s FREE planetarium app is an astronomy suite that redefines how you experience the night sky. there's also a bahtinov mask tool that you can move a box over to your star (might need to zoom out to see the box in the corner then drag it to your star and zoom in) and it will show you how close you are. The shoulder of the ff needs to be 130mm from the camera sensor. Miss the old Bintel Astronomy Setup Calculator? Here's a new and improved version where you can test your telescope and camera for ideal sampling and field of view. Beginning from the camera end, we do this: Consume 6. Attach the field flattener to the telescope, then use the adapters that came with the 533 to measure with a caliper back 55mm to the flat front part of the 533 (which should line up with the edge of the CCD. Note: Since this is the Basics section, the following discussion keeps focusing simple and describes the easiest and best ways to focus Failure to do so can result in serious damage to your eyes and the optics of your telescope. 25" eyepieces will be used, set the focuser in maximum out travel to result in the focal plane of the scope to be level with the top of the focuser. | Cookie Policy | Privacy Policy | Terms and Conditions | Acknowledgements | Bug Reports | Get In Touch | First Light Optics Ltd All rights reserved © 2025 Simply put, depth-of-field is how much of a photograph is in sharp focus from front to back. This measurement in millimeters, is the distance the sensor is set back from the face plate of the camera. Your Flat73 requires an additional 11. Adding extensions tubes before the diagonal can correct situations where you need more backward focus, but for Aug 27, 2021 · Procedurally, if the back focus distance isn't known but the reduction factor is, am I safe to test at two or more different distances, platesolve to establish the achieved focal length at each distance, and calculate the back focus distance that gives the required reduced focal length? (in my case, 2032mm x 0. Calculated data cannot be entered. Aug 21, 2020 · Page 1 of 2 - Back focus of SCT - posted in Cats & Casses: Hi, this is a newbie basic question. Jan 11, 2018 · Backfocus measurements specify the distance between the back of your telescope and the point at which light is focused. So, for example, if your telescope has a backfocus of 100mm, the plane of the sensor should be 100mm from the end of the telescope. Using adapters only *This solution needs the M48-M48 16. However, there are still some tricks to getting a precise focus. I have the Skywatcher Esprit ED80/ASI533 combo as well and this is how I've been doing it. Feb 29, 2020 · Accurate focus is critical to obtaining high-quality CCD images. By folding the light path and slowing down the convergence of the light cone, we shorten the tube to about the focal length of the primary mirror, while the telescope has a focal length of somewhere between 3 and 15 times the focal length of the primary! According to Celestron, their 8" scopes have a 5" back focus from the baffle tube lock ring. Apr 10, 2021 · Correct procedure for setting focus and back focus with an SCT reducer - posted in Equipment (No astrophotography): Hello all. My original question was to ask what the expected focal length of an Edge HD 8 was, so that I could plate solve back to the right length in alternate image trains. In other words, you rack the focuser all the in or all the way back but can not acquire sharp focus. 1 Back Focus Specification of Telescopes. I want to attach a flattener/reducer (Astro-Tech 0. Our online calculator lets you determine the best Star Analyser grating setup for your specific equipment. Adjusting back focus involves precise measurements and careful equipment setup. The resulting 37. Im curious about trying some prime focus Feb 23, 2017 · In other words, the focuser will require enough extension to place your camera 38. The other calculator is useful for determining where a dust particle is by measuring its resultant dust donut diameter in pixels. 7x reducer installed. If you have one those those latter telescopes, you can artificially extend your back focus using a lower magnification Barlow lens David Astro Tools offers a suite of free, user-friendly tools for astronomy and astrophotography enthusiasts. Apr 13, 2022 · It uses approximately 3. Let's take a look! Inputs: Add the values of “Focus distance” and “Focal distance” in the designated fields. Feb 10, 2023 · The Askar FRA500 is a compact beginner refractor telescope with an aperture of 90mm, a focal length of 500mm, and a focal ratio of f/5. there's a 'manual focus targets' tab/tool that will give you a list of bright stars and will slew to them. 4) With OAG-L and 2” filter: If you have an OAG-L, but do not have & want to use any filter wheel to reach 55mm back focal length. The focal length of the objective usually goes hand in hand with the length of the telescope itself. No zoom, no auto focus, all manual. ) Select a CCD camera and telescope (or enter an actual focal length and ratio of your telescope) from the dropdown lists below. Jun 25, 2009 · Take control of your telescope! Download the Celestron PWI Telescope Control Software. I don't know what else is behind the lock ring, but you will need to find a spacer or extension to get a combined 3" of back focus before focus can be achieved. 25") for the 8" model, a Focusing a telescope may sound intimidating, but it’s actually a remarkably easy process. So as the title implies, how do i calculate whats the back focus that i need for a specific telescope and camera. So, if you are shooting focal lengths of 50mm or shorter, the ATAN equation will give more accurate results. buyteleshibackfocus. (However, as mentioned previously, most Newtonian reflector telescopes will need a 2x Barlow or an amplifying lens for the binoviewer to reach focus. (0. Dec 2, 2024 · The back focus distance is only of relevance if using a flattener/reducer or a coma corrector in the image train, as these devices require a specific distance (back focus distance) from them to the image plane to avoid distorted stars towards the corners of the image. 5mm is the distance that you have to put between the camera and the telescope. The Critical Focus Zone (CFZ) of a telescope is the range within which the focus is acceptably sharp for astrophotography. Whether you’re curious about magnification, field of view, or need help selecting the right eyepiece, our calculator simplifies these complexities into easy-to-understand results. 63 = 1280mm) Sep 26, 2024 · How many solutions are there for ASI6200MM Pro to get 55mm back focus length? If you are still stressed with these problems, then this tutorial is exactly what you are looking for. Now, if you're lucky, all the components you're working Feb 4, 2017 · A simple Bahtinov Mask design. You first need to know the metal back distance requirement of your telescope or corrective optic piece. Feb 3, 2017 · Near focus is usually set to the Practical distance of the design of the Telescope in question. 75; Female thread - M42X0. Heres my attempt: 115÷805= . For more background on the most important specifications of telescopes, you may like to discover what the two most important telescope specifications are. With these inputs, the diameter of the focal spot is Feb 4, 2022 · Just looking at this calculator, but I assume it just is programmed with the correct back focus for a certain setup of camera, FW with a certain corrector or flattener, then adds on 1/3 thickness of the filter and then gives you the remaining spacers needed to make up that back focus, so nothing different to manually adding up all the elements and doing a bit of maths. A Barlow Lens, placed between the eyepiece and the telescope, will increase the Resulting Magnification by the power of the Barlow; i. I have read post after post here where people say they are still working on getting proper back focus. if the calculator shows that a certain eyepiece gives 100x in your telescope, and you add a 2x Barlow, the resulting magnification will be 200x (100 x 2). Is their a sticky explaining how you get the recommended back focus? How would you calculate in a focal reducer Jul 10, 2020 · Page 1 of 2 - William Optics Back focus - posted in Beginning Deep Sky Imaging: Since I have had endless nights of no imaging opportunities for weeks on end, as a relative newbie I figured I should spend some time dialing in some things that I can without imaging. Sep 30, 2023 · The back focus for your telescope imaging train is the measured distance from the last optical component at the back of the telescope, whether it’s a coma corrector or field flattner / focal reducer and the focal plane of the telescope where the camera detector is. Back focus is a little different on a Rowe-Ackerman Schmidt Astrograph (RASA) t Jul 27, 2021 · As you are now changing the back focal length by putting the barlow there, on an SCT you are also changing the effective focal length since they focus by changing the focal length through moving the primary mirror. 3° For Dobsonian/Newtonian, use Paracorr to correct coma. Formula: Aperture X Focal Ratio . I've read and seen videos saying that you have to get the back focus exactly right to achieve a sharp focus on the imager. draws some Welcome to our Telescope Calculator page! This tool is designed to help both amateur astronomers and seasoned stargazers calculate key aspects of their telescopes. The image is in focus when the sensor is positioned at the focal plane. but back focus is a big problem. For example, in order to achieve proper focus with a telescope that requires 55mm of backfocus, you'll need to substract 17. It’s equal to the telescope’s focal length divided by the eyepiece’s focal length. 3” adapter has only 2mm of optical thickness, this leaves 77mm of backfocus for your camera and accessories, also when used together with the Celestron EdgeHD . With over 150 years of combined experience Sep 26, 2024 · Note: This solution only applies to telescopes with M68 interface threads. 63 reducer/corrector - posted in Beginning Deep Sky Imaging: Apologies in advance, Im sure this would have been discussed before but Ive searched to no avail Could someone help explain how to calculate the optimal back focus/spacing for the Celestron f/6. 6. Guider SX lodestar (any version) optical back focus = 12. Read our guide! Feb 13, 2022 · For this post, I want to share my spacing settings/diagrams for the Edge HD 8. The back focus is 158mm. If you are shooting through a telescope or telephoto lens, either equatio will be perfectly fine. At High Point, our goal is to coach and nurture aspiring amateur astronomers and astrophotographers like yourself. For more information please visit NOIRLab Official Website for triplespec. Determining this distance can b Jul 23, 2023 · Meade LX200 EMC, 10" back focus with no reducer - posted in Meade Computerized Telescopes: I have a 10 Meade LX200 and Im trying to put a Crayford focuser and and OAG onto it but I cannot find any info regarding the back focus distance for this scope, or where exactly its measure from. Back focus is important because some accessories require a specific back focus distance to work properly and correct optical aberrations such as coma or field curvature. It now uses the more aggressive calculation based on the Goldman/Megdal article, In Perfect Focus, in Sky & Telescope, August, 2010. Considerations on EHD Back Focus Tolerance under Seeing Limited Conditions. Since the ESATTO has a depth of 67mm and the 3. Understanding back focus is crucial for sharp, focused astrophotographs. They are based on the FR being placed in its designed position at the back of the SCT: Moving mirror SCTs require special treatment because their focal length changes (lengthens) as you adjust focus to compensate for the in-focus required from inserting the focal reducer in the optical path. There will be many eyepieces that come to focus outside the range of your focuser. You're confusing the meaning of the term back focus with focal distance. That's it. 142857142857 . Telescope focal length increases 15%. Incorrect back focus can lead to blurry images or the inability to achieve focus at all. My Canon Rebel T7i camera has a back focus of 44mm. sk | Amatérska astrofotografia a astrotechnika I have a lot of trouble with the back focus of my skywatcher 72ed together with my Nikon d5600. This is a Aug 24, 2006 · If I go to a deserted island in the Pacific with zero wind (perfect seeing), 100% transparency, on a night with no moon, I can use a camera with very small pixels and net a very detailed image that I can zoom in on to represent what you can see through a giant observatory telescope's eyepiece at, I don't know, say 400X mag, even though I'm Dec 15, 2018 · The 12" SCT has a huge back-focus range ! How much back-focus do you need? Begin by turning the knob fully clockwise - that pulls the primary mirror all the way back and focal point all the way in. 8 x) with 55mm back focus, a ZWO ASI294MC pro cooled cmos imager with 6. 4″ (arc-second) Airy disc FWHM (or about 13 microns spot diameter for ~80% of encircled energy) in the visible (550nm), the inevitable atmospheric turbulence, or seeing, is usually much more than this. Determined by the telescope's focal ratio, the CFZ is narrower in faster (lower f-number) telescopes, demanding precise focusing to capture clear, detailed images of celestial objects. 1) Diagram, Variables, and Design Formulae Cassegrain telescopes are built to reduce the physical length of the telescope tube. The Critical Focus Zone: A common and popular figure of merit for focus accuracy is the Critical Focus Zone (CFZ). One of the mistakes frequently made by beginners is starting with too high of a magnification. I found the attached matrix spreadsheet (from https://www. 5mm from 55mm. While a C11 scope at f/10 can deliver a 0. We encourage you to try out the calculator for yourself. 7 cm² • Light gathering power: 319x • Angular resolution: 0. IBF = 44 + 8 = 52 mm back focus (low profile configuration) Notice: T-ring adapters for most cameras are designed and made to lead to a 52mm back focus distance (like here for the Canon EOS). 265 . 5mm (red) and 1mm (gold). If you already have a telescope, the focal length can often be found on the telescope itself. Enter your equipment details in our Equipment form and we’ll do the rest. Sep 3, 2019 · Barlow and Back Focus - posted in Beginning Deep Sky Imaging: Hey folks, can someone help me understand how much a barlow impacts optimal backfocus in an imaging train? I assume this has been answered clearly some place that I simply cannot find My gear: OTA: Celestron EdgeHD 8 Barlow: Televue Powermate 4x + 2x Filter Wheel: Starlight Xpress USB Camera: Altair 1600M PRO My current Jun 5, 2022 · Image circle size calculation? - posted in Beginning Deep Sky Imaging: How do you calculate image circle size for a telescope? I am trying to determine the circle size on an Orion EON 115mm triplet. On this page, you will find an easy-to-use telescope calculator. Its rare that I commend Celestron, but they actually have a very clear diagram that shows the back focus with Aug 18, 2023 · This adds up to the standard 55mm. Sep 10, 2023 · The back focus for your telescope imaging train is the measured distance from the last optical component at the back of the telescope, whether it’s a coma corrector or field flattner / focal reducer and the focal plane of the telescope where the camera detector is. I use a field flattener with a t ring to connect my dslr to my telescope. That would leave an adapter Mar 22, 2018 · Page 1 of 2 - Calculating back focus for Celestron 0. We can achieve critical focus for only one plane in front of the camera, and all objects in this plane will be sharp. Optimum back focus distance (T-Ring shoulder to focal plane) is 56mm. Assuming you use the telescope as the lens for the camera at prime focus the focal distance of the camera becomes that of the telescope. Okay, I'll walk away from the chalk board now. 25" size). 35mm (5. The Edge 8 can be tricky to achieve nice, round stars to the edges, particularly with the 0. It should really just be a 2" visual back at the back of the scope, the barlow, and then the camera (and yes, that will reach focus). 5mm back focus. In the figure, R 1 is positive and R 2 is Sep 20, 2017 · recommended back focus - posted in Beginning Deep Sky Imaging: I made a post yesterday about getting a new zwo asi224mc. It may or may not help. This is May 7, 2009 · The design most heavily impacted is the Newtonian due to its short back focus; the only two possible fixes are to move the mirror and its cell up in the tube and/or get a low-profile eyepiece focuser. Afocal photography is different and varies based on each optical element in the train. /Ira Aug 14, 2024 · The object got magnified: you can learn more at our telescope magnification calculator; and; The perceived brightness increased since the light collected from the whole opening of the telescope is now concentrated in a small spot (that's why the bigger the telescopes, the better they are: as they collect more light). Apr 29, 2022 · Back focus is a term that causes much confusion among newcomers to astrophotography. This is a Apr 26, 2011 · prime focus image circle - posted in Beginning Deep Sky Imaging: Is there a formula to determine the diameter of the image circle produced by a given telescope, and/or the angular dimension (TFOV?) of that circle (Im not sure I have the correct terminology. Hopefully the included images will aid you in refining your setup, and give you an idea of what to expect in terms of field flatness with this setup. 7x focal Feb 25, 2021 · Edge HD back focus - posted in Celestron Computerized Telescopes: Hi, Heres a recent support thread from Celestron. Magnification (power): The amount that a telescope enlarges its subject. 25" eyepiece barrel, and scopes with 2" focusers will usually cover the field of a 2" barrel (There are some exceptions where the field is bigger than 1. Simply measure the diameter of the dust donut in pixels and define the binning used. Oct 29, 2016 · Takahashi Back Focus - posted in Experienced Deep Sky Imaging: Im looking for an accurate back focus of Takahashi telescopes including using with reducer/flattener. com Search the Nov 14, 2020 · Don't confuse back focus with position of focus relative to the telescope body or camera back focus. The focal length 805mm. Aug 3, 2018 · Calculating Backfocus - posted in Beginning Deep Sky Imaging: I am extremely new to imaging and could use a bit of help. The flattener needs 95mm. Step 3: Set the Telescope's Finder on the Object The primary goal is to ensure that the crosshairs are in the direction of the object you want to observe. 5mm back focus refers to the camera with the tilt plate and the 12. If you enter an actual focal length and ratio then any selected telescope will be ignored and the extender/reducer factor will be applied to this entered value. From what I understand, yep. I recently picked up an ASI1600 MM cooled camera, the ZWO Filter Wheel, and have the following scopes: ES 80mm f/6 refractor Meade ACF LX600 12 (305mm aperture, f/8) Do I need to add spacers if I have the 1600 at prime focus? I know that if I were to get a field flattener Mar 3, 2017 · How do you calculate the true focal length of an SCT with a focal reducer in two different positions. To this point, we have used 48. The main lens is 115mm. Sep 21, 2022 · With tilt adjuster attached, the diagrams show the back focus distance is 17. Simply input the model of the telescope you plan on using to find out which solar filters will fit properly. In the EdgeHD whitepaper Celestron describe the optimal backfocus of 133. One of the many advantages of CCD imaging over film astrophotography is that achieving focus is much easier with a CCD camera. For example, when I try to find the back focus of TOA-130S with 0. Useful for getting that precise backfocus distance from a reducer or flattener when imaging and prevents binding between two M48 threaded parts. 3 focal reducer/corrector on a 6SE OTA? Ive seen the number 105mm in a few places Jun 13, 2019 · 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. This is the distance from the camera's internal optical sensor to the face of the camera. We strive to offer you high-quality telescopes and telescope accessories at low prices without skimping on customer service. 75; eliminates a range of focusing problems ; The extension tube has a T2 interior thread and a T2 exterior thread for elegantly solving spacing problems in astrophotography The Cassegrain telescope optical equations. Feb 1, 2022 · New fine-adjustment spacer rings from Baader in three sizes 0. Back focus is a flattener or reducer issue. Highlight the numbers already entered in the boxes and delete them and enter your own. Hello :-) They then use the zoom on the camera No, they do not. First is a Meade Series 4000 f/6. (Note: Using the simple equations above, the focal length of this reducer can be estimated to be about 350mm). 5mm back focus is without the tilt plate. This calculator computes the spot diameter of a collimated Gaussian beam whose wavelength is and diameter at lens when it is focused with a lens having a focal length . Common focal lengths for amateur telescopes range from 400mm to 3000mm, with larger telescopes often having longer focal lengths. Presumably, if I place a 20mm spacer between the rear cell and the focal reducer the focal length of the telescope will be different than if I place the focal reducer between the rear cell of the telescope and the 20mm spacer. CCD Pixel Size. gooday@btinternet. 1. For large numbers, do not use commas. An infinity focus on a camera lens means that light rays flowing into the camera sensor are parallel and arrive as points. Or setup with eyepiece at same Select a CCD camera and telescope (or enter an actual focal length and ratio of your telescope) from the dropdown lists below. 5mm back focus, and eventually a filter drawer with 21. Feb 25, 2021 · I've been playing around with Meade ACF with a Lepus Reducer 6. Enter any ONE of the following four parameters and click the corresponding "Calculate" button to calculate the other three parameters. Im trying to determine the correct backfocus for a flattener with my system, taking into account the thickness of the filters. Jan 8, 2024 · Determining the correct back focus for your telescope can be a daunting task for both beginners and experienced astrophotographers. But Im not sure whether its 100% accurate. Contacted Meade, OPT, Lepus, and was informed by all that back focus should be between 105mm and 110mm with 110mm supposed to be optimum. Determining this distance can b Dec 28, 2023 · Back focus is the distance from the last optical element of your telescope or accessory (such as a field flattener or a focal reducer) to the focal plane. 3″ BIG Paracorr Type-2 The first and most important thing to know is that that the 3” BIG Paracorr (VIP-3010) is only really necessary for fast scopes when you’re imaging with chip/sensor sizes beyond 30mm diagonal. That being said, this configuration may make it impossible for the 8SE to swing high enough to image the planets since the fork arm doesn't give a lot of space between the back of the scope and the base. This makes calculating the back focus distance more complicated since they influence each other. Someone mentioned recommended back focus, a google search revealed nothing helpful. The first light back-end instrument for this telescope will be a faint The optical ray drawing shows the telescope focus, the pupil plane and the 3305513-535. 5 mm of back focus. Its purpose is helping beginners to get an idea of what they can see in an amateur telescope, according to its diameter Working of an Online Magnification Calculator: Our online calculator requires you to provide a couple of inputs to get accurate results instantly. gvje koqyeqke vptyp zkcuz yudiapr imljj iontk jyf bxu zdot