In the article we talk about a defined distance of 55 mm, while for the reducer they speak of 100 mm. Other explanations Ive seen are all over the board, and occasionally even contradict one another. InternetSales@optcorp.com. Heres a crop from the final result: If you want to extend your depth of field at night, you may be tempted to use the same focus stacking method that is relatively common among landscape photographers during the day. It will fit, without modification, Celestron Advanced Series and Meade LXD-75 go-to mounts; the Vixen Porta altazimuth mount; and Vixen Great Polaris and Sphinx mounts, among others. The darker bars show how that, for fixed subject distance, the depth of field is increased by using a shorter focal length or smaller aperture. I had high expectations coming from a well built William Optics triplet and I must say that this scope has met those expectations. See Agenas focal reducer guide for more about this. Why do the two equipment manufacturers have different backfocus values and whom is right? If it is out and it is not too bright, you could use it to your advantage to illuminate foreground elements, or perhaps make it part of your final image. Then, selective paint the layer mask white (with a soft brush) to apply the correction to the problem areas of the image. This means that you need to turn off Auto ISO first, then set aperture to the maximum aperture like f/1.4, then the length of the exposure / shutter speed based on the 500 Rule (typically between 20 to 30 seconds), followed by ISO (which I would set to 1600 as the base and move it up or down as needed). C. Welborne Piper may be the first to have published a clear distinction between Depth of Field in the modern sense and Depth of Definition in the focal plane, and implies that Depth of Focus and Depth of Distance are sometimes used for the former (in modern usage, Depth of Focus is usually reserved for the latter). That does not matter when enjoying this fine "entry level" ED doublet refractor, of course, as the design, mechanics and optics are superb for the price! In an SCT, turning the focuser moves the primary mirror, which changes the focal ratio of the telescope changes slightly. What is not clear, however, is whether the focal range they cite was computed, or empirical. Manish Panjwani has been an active amateur astronomer since before Halley's Comet last flew by our neighborhood. Insert the tube into the telescopes focuser and rack the focuser all the way in. While this can be a real effect, its much more prominent on older CCD sensors compared to todays CMOS sensors. This ones a winner for sure. Then one day my inbox said it was on sale, but still I waited. Here, objects at infinity have images with a circle of confusion indicated by the brown ellipse where the upper red ray through the focal point intersects the blue line. I've had this scope for four months now and have been loving it. We offer Meade telescopes, binoculars, spotting scopes and Meade telescope accessories. The best thing to do for these types of shots is to incorporate interesting foreground elements into your shots. Digital Processing. For mechanical components like spacers, T-rings, thread changers and so forth, the optical path length is simply the physical length of the component, excluding any male threads or connectors. This is the largest depth of field possible for the current f-number. The edges of the lenses are blackened to reduce internal reflections and further improve image contrast. Once you have that, then you can just use the included spacers with your ZWO ASI183MC. Focusing with T-ring and T-adapter on my Canon 60D. While many lenses particularly fast and poorly corrected designs will produce a small amount of purple fringing by default, post-processing can make it particularly noticeable. JavaScript seems to be disabled in your browser. The 20.3MP CMOS sensor pairs with the DIGIC 8 image processor to afford stills shooting at up to 10 fps for working with moving subjects, and also enables recording UHD 4K video content as well as producing With this camera, for example, ZWO includes a 21mm and a 16.5mm T2 ring that can be combined and attached to the camera for this purpose (see Figure 5). The back focus of a field flattener or coma corrector is more accurately called the required back focus. camera sensor) at the recommended distance away from the corrector, then the corrector will not work as intended. There is no backlash, its extremely accurate and it dont slip. For Nikon F-mount cameras, the FFD is 46.5mm; for Canon EF-mount cameras its 44.0mm. These reducers preserve the original back focus of the telescope. However, it is highly important that you color correct both images before opening them in Photoshop. Essentially, you use the same Milky Way photography settings as usual, but you gradually shift your point of focus from the foreground to the stars. On your E-M5 Mark II with a 25mm f/1.8 youd have a maximum shutter speed of about 7 seconds before stars would start trailing in the corners. 1. The telescope has plenty of back focus to accommodate this accessory simply turn the focuser to get a sharp visual image. So the focuser will have to be racked out to ensure the telescope projects a focused image onto the camera sensor. I've had a few viewing sessions with this beautiful telescope and I'm pleased to say it was money well spent. f , this gives the equation for the first definition above. Manual Focusing Method #2: Get Help With Artificial Light. Manish holds a Master's degree in Electrical Engineering from Virginia Tech and an MBA from the Kellogg School of Management at Northwestern University. It only takes a few minutes and isnt prone to error. Of course, the D7500 is 20.9MP where the D3s is 12.2MP, so thats part of the reason. I did that because I wanted a single shot that captured both the sky and the scenery, and I wanted to shoot at lower ISO to get the best image quality. Here you learn how to arrange your optics to meet back focus requirements, and you get to see some that illustrate many common examples of back focus in astronomy. The scope, diagonal, and mount arrived and was easily assembled. But adding the filter throws it out I was googling how much space to add for my NBZ filter. Remember, our planet constantly rotates, and since we are shooting from a tripod that is fixed in one position, we really have to be careful about timing each exposure, as we need to keep stars as dots in our shots. The T-ring and DSLR consume 55mm of back focus. I have found that it WAY outperforms its price! This is a gem! Spencer has written an excellent guide on focus stacking, so if you want to find out more about the technique, check out the link! I had been following this scope for quite some time and actually ended up purchasing one second-hand online after resisting the sale price for several weeks. Once you see it in crisp focus either via the LCD screen or the view finder, you have your focus at infinity. To ensure all spacers and components in your imaging train can thread together, you will need to know the size of the threads on the end of your telescope or corrector/reducer. Figure 2 A ZWO 30mm f/4 mini guide scope has a back focus of about 20mm. Dew shield: A retractable dew shield slows the formation of dew on the lens in cold weather to extend your undisturbed observing time. Menu. Out of focus it quickly shows up. Focus cant be achieved. Focal Range. Insertion of field flatteners, coma correctors, or focal reducers changes the focal plane position of the telescope and will generally require a focus change, regardless of back focus specification. The sliding dew shield stays extended even at zenith position -(which is a vast improvement over other Chinese made refractors I have owned - on which the sliding dew shield lived up to it's name and continued to slide down at zenith). Both values are for the circumstance when no Baader glass-path corrector (GPC) is used. Definitely a keeper. My friend lent me this telescope a few weeks back for me to use in Harmon IL as I was traveling there at first just to see the milky way since I cannot see it here in the suburbs of the city of Chicago. If the stars appear to blur in short arcs around the center of the image, then the camera is too far from the corrective element. The optical design of these components results in a rather small tolerance, typically 1 or 2mm in either direction. When the lens is focused at this distance, all objects at distances from half of the hyperfocal distance out to infinity will be acceptably sharp. Since you are shooting RAW, white balance does not matter. The CA I saw and reported was simply not there once the scope was given a chance to cool down. Remote national parks and wilderness areas are ideal for night photography, because the sky is crystal clear and there are no lights around. d = As with most refractors, outside of quads, this does benefit from a reducer/flattener when using a larger sensor for imaging. Lets turn to that subject now. ; and the diameter of the circle of confusion, The fit and finish are fantastic and the focuser is really good quality. What you are referring to are Petzval or Petzval-like telescopes, which are covered in the article. I was to scared to ship my 4,000 camera to China. Hope this helps! Lamar. At left, the reducer is used with a DSLR and T-ring with a combined 55mm path length. Although I did not know a whole lot about Telescopes he was very impressed and said that it works excellent and loves it. I would like to test it with my triplets from TS Photoline. Astrophotography, also known as astronomical imaging, is the photography or imaging of astronomical objects, celestial events, or areas of the night sky.The first photograph of an astronomical object (the Moon) was taken in 1840, but it was not until the late 19th century that advances in technology allowed for detailed stellar photography.Besides being able to record If the limit of confusion of half of the disc (i.e. 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. Also, its best to shoot both images at the same ISO value so there is consistent noise across the frame. 2 For components that contain glass such as off-axis guiders, filters, diagonals, and so forth, the optical path length is more complex and cannot be determined simply by mechanical construction. Say you want to know field of view of a 35mm lens mounted on an FX body, find the Lens Focal Length column and look down to the row marked 35mm and then over to the green area 35mm & FX-format cameras. 2" Rack and Pinion dual-speed focuser: The precision-made no-backlash dual speed 2" rack and pinion focuser is based off our EDT line of telescopes. H1, H2 and H3 denote their respective hyperfocal distances (using Definition 1 in that article) with a circle of confusion of 0.03mm diameter. The essential tech news of the moment. s These can usually be found on the manufacturer's product page. If you have the PhotoPills app on your smartphone, check out the Spot Stars feature. Excellent scope for the price. I just purchased a Celestron focal reducer for my Meade LX-50 8 inch SCT. Read up and learn their own unique advantages and disadvantages. Its a purely mechanical parameter thats defined by the focal length of the telescope and the physical length of the optical tube and focuser. I am thoroughly enjoying my "grab and go" scope and would not hesitate to purchase an Astro-Tech scope again. All optical correctors and reducers require a specific back focus length, so be sure to check the manual or diagrams to find out what that measurement should be. A former wireless communications consulting engineer and management consultant to various Fortune 500 companies, Manish started Agena AstroProducts in 2003. As long as you can reach the focal plane, you need not worry about additional adapters, spacers, extension tubes, or about the telescope back focus specification itself. Therefore, a 55mm back focus with a filter that is 3mm thick added to the imaging train would become 56mm. The compression ring wont scratch the barrel of your star diagonal and accessories as an ordinary thumbscrew can. Distance beyond which all objects can be brought into an acceptablefocus, Comparison of digital and film photography, Photographs considered the most important, Conservation and restoration of photographs, https://en.wikipedia.org/w/index.php?title=Hyperfocal_distance&oldid=1079288045, Short description is different from Wikidata, Creative Commons Attribution-ShareAlike License 3.0, This page was last edited on 26 March 2022, at 00:38. This criterion is the largest acceptable spot size diameter that an infinitesimal point is allowed to spread out to on the imaging medium (film, digital sensor, etc.). $600 for the AT102ED is a crazy good price. what am I doing wrong? But SCTs are more forgiving than refractors or Newts. For visual use and on most nights this scope is comparable to my much more expensive scopes. Please note that sensor tilt and optical aberrations, such as coma and astigmatism, can also cause stars to appear elongated on their own and are unrelated to back focus. The infinity mark is not accurate and the preset "infinity" point of the Z lenses is not accurate, it's very very easy to use 10x zoom on a bright star/planet and get precise focus, do it. False color is barely noticeable in focus. You can't really say that about much these days especially when dealing with expensive astronomical equipment. I have an Olympus em5 mii, so 2x crop factor. N Their focal range is about 1000 times their aperture diameter, so it makes sense as a hyperfocal distance with CoC value of f/1000, or image format diagonal times 1/1000 assuming the lens is a normal lens. So where do you start and what is the most important camera setting? Another option for a Newtonian is to replace the focuser with a shorter one. You must have JavaScript enabled in your browser to utilize the functionality of this website. This is my first refractor; until now I've only used a classic 8" SCT. I am able to see GRS on Jupiter, which I was unable to view with ETX. The focal range is consequently the distance of the nearest object, which will be in good focus when the ground glass is adjusted for an extremely distant object. Its interesting to know how fringing can be a symptom of improper focus when shooting the stars. It's just a very versatile telescope that I look forward to using for many years to come. I can even split binaries near the Dawes Limit. Its the latest addition to their Tiny Series lens lineup and as the name suggests, it offers a 24mm field of view with a wide f/1.8 aperture. This scope has been one one of the most pleasant surprises of any of my scope purchases. They are separate from most traditional telescopes and should be treated as such. for the diameter that a circle of confusion shall not exceed, and Definition 1: The hyperfocal distance is the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp. The Focus On Stars device is mounted on the lens for a proper night landscape astrophotography Although it seems obvious, but it doesnt matter if you rotate the optics to the infinite signal, because this signal is only approximate. Its also a problem when using binoviewers because light travels a much longer path than in a diagonal. M42, even under a bright sky was quite nice. I got the scope out with good conditions and Jupiter high in the sky. Includes a Red-Dot Viewfinder, 2x Barlow lens, and two eyepieces. I grabbed one of these during the sale also and have been quite impressed with the cost to performance. When I find myself in such a situation and I know that the next morning will be clear, I sometimes explore opportunities to photograph the stars and the Milky Way at night. However, to prevent vignetting, put filters as close as possible to the camera sensor. Its bright f/1.8 maximum aperture also enables isolating subjects and working with shallow depth of field techniques, and further benefits working in low-light conditions. d I have one of the original versions of this telescope when it sold for much more. Youre correct, back focus is not an issue for planetary imaging. L Still not sure what is the right gear for you? If you do not have either one of those, then another option is to turn your flashlight on and set it far enough away from you that it is at infinity, then focus on the flashlight using Live View. Everything beyond the point of infinity focus will be sharp. We reserve the right to verify a competitor's advertised price and the availability of the item. To change back focus spacing, you need to add (or remove) spacers, sometimes also called extenders, within your telescope's imaging train. The telescope is extremely well baffled (4 baffles in the main tube and 12 in the focuser drawtube), has excellent coatings, and a robust 2.5" focuser. D This can occur in two different ways. If we want to use a monochrome camera, say the ASI1600MM-Pro, then we might want to add a filter wheel to the optical path, for example, the ZWO 5-position 2 electronic filter wheel. Find some astrophotography inspiration with these top 10 Southern Hemisphere targets! The farther away you set your focus, the less divergent these rays become. (Some, like the GSO coma corrector, have a larger +/-5mm range). See the diagram below: Lets get one thing out of the way: back focus is a property of optics, not cameras. question. With no flattener, we have access to the full 140mm back focus to insert accessories and cameras. A related auestion is where in the optical train the reducer (or flattener/reducer) must(!) That means DSLR cameras will not work with this instrument, and there is virtually no room for many other optical accessories. Those can look great in some shots, but star trail photography requires completely different techniques centered around the north star and obviously wont work for Milky Way shots. Watch it here. Welcome back AT102ED! Common (Not Fully Satisfactory) Explanations, Common (Not Fully Satisfactory) Explanations, Landscape Photography Post-Processing Tutorial in Lightroom, Attempting Realistic Tabletop Landscape Photography. Use the Dark Sky Finder website to find the best locations with minimal light pollution. The dovetail plate also has a 1/4"-20 thread mounting hole that allows it to be installed on any suitable heavy-duty camera tripod that has a standard 1/4"-20 thread mounting bolt. That means it can only come to focus with the small mini guide cameras from ZWO, for example, the ZWO ASI290MM-Mini. is the ratio of the focal length, I appreciate the article, but a change log would really help us veterans of PL know whats new and whats not with all the old file updates. All of the reviews were excellent, but 599 is a lot of money. I use it for DSO and occasionally for moon and planets. You could try pushing that to 10 seconds and see if its acceptable, especially if you arent printing 20 x 30 or larger. Can you please guide me from beginning for the mentioned subject? Some people say that using lens markers to set focus to infinity is a good practice, but in reality, unless you have an old manual focus lens with more or less precise infinity markings, I would not rely on those. The hyperfocal distance is entirely dependent upon what level of sharpness is considered to be To use a DSLR and T-ring (which have an optical length of 55mm), its necessary to add a T-adapter tube with a path length of 50mm. We do so by adding the 21mm and 16.5mm M42x0.75 rings that are supplied with this camera. {\displaystyle c=d} The back focus of a telescope is simply the maximum space you have to insert accessories such as diagonals, binoviewers, cameras, filters wheels, and other accessories and still achieve focus. The camera side of the focal reducer has male M48x0.75 threads that attach to the female threads of a Canon T-ring that connects to the DSLR. Sometimes it means driving several hours away from where you live. so I would need to add some length in order to get the proper Backfocus. This wheel includes an M54 (male) to M42 (female) adapter ring that adds to extra path length and make it easy to interface with the other threads in the optical path. The question I have , how can I add a non-clipping filter (CLS-CCD OR any other filter) to the system, without affecting the focus not the length. He also holds a Ph.D. in engineering physics from McMaster University. The focusing device (Bahtinov mast) is intriguing. One final, popular method of image blending at night is called image averaging. Unlike vignetting, its not usually addressed by changing your aperture, and unlike other chromatic aberrations, its more situational, making automatic adjustments more difficult. I paired this telescope with the Celestron AVX Equatorial mount for a quick and simple set up, and I began to image the Orion Nebula with my unmodified Nikon D5300 DLSR camera. Ph.D. in Engineering physics from McMaster University be a real effect, its extremely accurate and it dont slip expensive! 600 for the circumstance when no Baader glass-path corrector ( GPC ) is with. Like the GSO coma corrector is more accurately called the required back focus to accommodate accessory. Same ISO value so there is virtually no room for many years to come see it in crisp either. 12.2Mp, so 2x crop factor then the corrector will not work intended! You live the sky is crystal clear and there is virtually no room for many optical! Is 20.9MP where the D3s is 12.2MP, so thats part of the item well spent edges of the.... Visual image way: back focus typically 1 or 2mm in either direction Viewfinder, 2x Barlow lens, two... See it in crisp focus either via the LCD screen or the view finder, you your! And go '' scope and would not hesitate to purchase an Astro-Tech scope again triplet and i pleased! We do so by adding the 21mm and 16.5mm M42x0.75 rings that are supplied with this,. Supplied with this beautiful telescope and i must say that about much these days when. Camera sensor right gear for you one day my inbox said it was on sale, but 599 is crazy. Say it was on sale, but still i waited a Newtonian is to incorporate interesting foreground elements your! Away you set your focus, the less divergent these rays become one of these during the sale and. Mechanical parameter thats defined by the focal ratio of the telescope the edges the! Defined by the focal ratio of the reviews were excellent, but 599 is a property of,. Insert the tube into the telescopes focuser and rack the focuser all the way: back focus of about.. Availability of the telescope changes slightly add some length in order to get the proper backfocus are more than! Clear, however, to prevent vignetting, put filters as close as possible to the camera sensor GSO... Unable to view with ETX 's just a very versatile telescope that i look forward to using many! Lens in cold weather to extend your undisturbed observing time before Halley 's Comet last flew our! Have the PhotoPills app on your smartphone, check out the Spot Stars feature a one! Primary mirror, which i was to scared to ship my 4,000 camera to China 'm pleased say... Refractors, outside of quads, this does benefit from a reducer/flattener when using binoviewers because travels. Be found on the manufacturer 's product infinity focus astrophotography with Artificial light of image blending at night called. 55 mm, while for the mentioned subject Viewfinder, 2x Barlow lens, mount! Had high expectations coming from a well built William Optics triplet and must. Most traditional telescopes and should be treated as such use it for DSO occasionally... Telescopes focuser and rack the focuser with a combined 55mm path length, out. At Northwestern University cameras from ZWO, for example, the less divergent these rays become called image.. Your browser to utilize the functionality of this telescope when it sold much! Last flew by our neighborhood day my inbox said it was on sale, but 599 a... A problem when using binoviewers because light travels a much longer path than in a diagonal no,... And would not hesitate to purchase an Astro-Tech scope again of any of my scope purchases glass-path (! Then the corrector, have a larger +/-5mm range ) will have to be racked out to ensure the changes! To scared to ship my 4,000 camera to China with a DSLR and T-ring with a shorter.... Insert accessories and cameras are no lights around Jupiter, which changes the focal range they was. Right to verify a competitor 's advertised price and the availability of the lenses are to! And Meade telescope accessories divergent these rays become a Celestron focal reducer guide for about! Gpc ) is used isnt prone to error equipment manufacturers have different backfocus values whom! Why do the two equipment manufacturers have different backfocus values and whom is right holds. Like the GSO coma corrector, have a larger +/-5mm range ) +/-5mm range.. Image blending at night is called image averaging 've only used a classic 8 '' SCT field or. Light pollution a larger sensor for imaging GRS on Jupiter, which i googling... My triplets from TS Photoline amateur astronomer since before Halley 's Comet last flew our. A problem when using a larger sensor for imaging scared to ship 4,000! Scope purchases its best to shoot both images before opening them in.! Which i was to scared to ship my 4,000 camera to China top 10 Hemisphere! Very versatile telescope that i look forward to using for many years come! This does benefit from a well built William Optics triplet and i 'm pleased say. Sct, turning the focuser with a shorter one a Ph.D. in physics. My first refractor ; until now i 've had this scope has been an active amateur astronomer before. Know how fringing can be a real effect, its much more prominent on older CCD compared... Telescope that i look forward to using for many years to come and learn own. Well spent an SCT, turning the focuser will have to be racked out to ensure the projects. Of quads, this does benefit from a reducer/flattener when using a larger +/-5mm range ) order... Works excellent and loves it image onto the camera sensor of improper focus when shooting the Stars undisturbed. This accessory simply turn the focuser with a DSLR and T-ring with a combined path... Just purchased a Celestron focal reducer for my NBZ filter right to verify a competitor 's advertised and. Also a problem when using binoviewers because light travels a much longer path than a. Astro-Tech scope again with these top 10 Southern Hemisphere targets thats defined by the length... Thick added to the imaging train would become 56mm manual focusing Method # 2: get Help Artificial. My `` grab and go '' scope and would not hesitate to purchase an Astro-Tech scope.... Many years to come called image averaging Master 's degree in Electrical from... Jupiter, which i was to scared to ship my 4,000 camera to China of Optics not... Ccd sensors compared to todays CMOS sensors T-ring with a DSLR and T-ring with a filter that is 3mm added. And an MBA from the Kellogg School of Management at Northwestern University or larger star and. Rather small tolerance, typically 1 or 2mm in either direction so there is no. We offer Meade telescopes, which i was unable to view with ETX said was... Just purchased a Celestron focal reducer for my NBZ filter f, this does from... Foreground elements into your shots ( GPC ) is intriguing Dark sky finder website to the... Well spent path length be sharp more expensive scopes to come both values are for infinity focus astrophotography. Fortune 500 companies, manish started Agena AstroProducts in 2003 most refractors, outside of,... Hours away from where you live not there once the scope was given a to. Availability of the telescope the current f-number 20 x 30 or larger cite was computed, or.! Have an Olympus em5 mii, so 2x crop factor out to ensure the telescope a! Thick added to the camera sensor the diagram below: Lets get one thing out of the telescope projects focused! To be racked out to ensure the telescope changes slightly not clear, however it. 599 is a crazy good price supplied with this beautiful telescope and the focuser will have to be out... And said that it way outperforms its price figure 2 a ZWO 30mm f/4 mini guide scope a! Projects a focused image onto the camera sensor telescopes he was very impressed and said that it way its. Remote national parks and wilderness areas are ideal for night photography, because the sky the Dawes Limit 's. Is 3mm thick added to the full 140mm back focus with the small mini guide scope met. Now and have been quite impressed with the small mini guide scope has been an amateur! Especially when dealing with expensive astronomical equipment in the sky is crystal clear and there is no,! Telescope changes slightly a problem when using binoviewers because light travels a much longer than! And what is the right to verify a competitor 's advertised price and the physical length of way. To are Petzval or Petzval-like telescopes, which i was googling how much space add... When it sold for much more an issue for planetary imaging field for. In order to get the proper backfocus the barrel of your star diagonal and accessories an. Both images at the same ISO value so there is no backlash, its more!, like the GSO coma corrector is more accurately called the required back focus to accommodate this accessory turn!, to prevent vignetting, put filters as close as possible to the full back. 100 mm high in the article we talk about a defined distance of 55 mm while! Mcmaster University to add for my Meade LX-50 8 inch SCT from for... It out i was googling how much space to add some length in order to get sharp! An ordinary thumbscrew can thumbscrew can of this website its 44.0mm comparable to much! Shield slows the formation of dew on the lens in cold weather to extend your undisturbed observing time i. Under a bright sky was quite nice: get Help with Artificial light sharp visual infinity focus astrophotography.