But what do different eyepieces and accessories actually do for your telescope's performance? Dobsonian telescope advantages and disadvantages – Quick View . It is our mission. When John Dobson invented the Dobsonian he wanted the general public to have access to an inexpensive, lightweight, and yet at the same time a large aperture scope. A spin-off of the 1100 mm Cruxis Telescope, cable on a third of the mirror circonference, cable on a quarter of the mirror circonference, 4 support points at 22.5° and 67.5° from vertical, 4 support points at 30° and 60° from vertical, 4 support points at 15° and 45° from vertical, 4 support points at 14° and 45° with unequal load (Alois Ortner). This model is an innovator in the field, using simple materials in its construction, that when combined creates an expert telescope, for a fraction of the price! How do I know if I need to collimate my telescope? Focal Length / Ratio; Magnification; Field of View; Telescope Capabilities; Binocular Calculators; CCD Calculators; CCD Suitability; CCD Filter Size; Guidescope Suitability ; Unit Conversion Calculators; Star Chart; Cloud Forecast; Lookup Coordinates; FAQ; Links; Get In Touch; Field of View Calculator Test different telescope, camera & eyepiece combinations. Most of these numbers can be found on your eyepiece barrel, on your telescope's tube or mount, or in the equipment's instruction manual. Sky & Telescope, Night Sky, and skyandtelescope.org are registered trademarks of AAS Sky Publishing LLC. 3 Best Laser Collimator Choices for Newtonians 2021; 5 Best Barlow Lens You Can Get in 2021; 5 Best Telescope Eyepieces for you in 2021; Categories Astronomy Tags dob, dobsonian Post navigation. mirror when it's pointing to the horizon. 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 telescopes at once and also calculates the differences between them. Version 1.1 (20071128) Glued mirror case and Strehl reduction calculation added, Version 1.2 (20071201) 1/20th mirror thickness offset cases added, Version 1.3 (20080109) Useful links to construction examples, Version 1.4 (20080307) Show sagitta and estimated mirror weight, Version 1.5 (20080707) Aberrator simulations of surface errors + 120° edge bearings configuration added. Calculate the exit pupil of the telescope-eyepiece by dividing the eyepiece's focal length in mm by the scope's focal ratio, e.g., a 20mm eyepiece used with a F5 telescope gives an exit pupil of 20/5 = 4mm. The 5 nm RMS level is indistinguishable from perfection. December 2, 2016, Citizen Science: Projects & Collaboration, By: Kelly Beatty Affiliate Program; TEL: 604-998-7071 Hello Guest, Login / My Account. January 1, 2021, By: Les Dalrymple question is asked to help in my choice of telescope thanks Related Posts. Calculators . Shipping calculated at checkout. Browse an extensive selection of astronomy equipment at Telescopes.net. February 24, 2011. Leave a Comment Cancel reply. Dobsonian telescopes are known for their large aperture and low magnification, which makes them ideal for observing faint objects in a very wide field of view. Read further below for a discussion of the best support configurations and the acceptable level of error. Creating goodies for the observing enthusiast has been founder Al Nagler's continuing pursuit. Use this Mirror Edge Support Calculator to analyze the edge support for the mirror pointing to the horizon. It's in the materials we choose, the designs we create, the craftsmanship we demonstrate...the images we deliver. The design incorporated narrow-pass filters and better eye-pieces, alongside low mass proportions of the telescope itself. If we wanted more magnification, we could use an eyepiece with a shorter focal length, such as 10mm: 1200mm/10mm = 120x magnification We could also use these eyepieces with a … How to collimate a reflector telescope is much the same as collimating a Dob. These telescopes are affectionately known among astronomers as "light buckets" thanks to their bucket-shaped design and their superb ability to concentrate light and deliver it to the eyepiece. The eyepiece’s focal length (for example, 25mm) To find the magnification, we’ll simply divide the numbers: 1200mm / 25mm = 48x magnification That’s it! Use this Mirror Edge Support Calculator to analyze the edge support for the mirror pointing to the horizon. September 4, 2014, By: Alan MacRobert Tele Vue Optics, founded in 1977, has been thrilling amateur astronomers since 1979. A Dobsonian telescope is an altazimuth-mounted Newtonian telescope design popularized by John Dobson in 1965 and credited with vastly increasing the size of telescopes available to amateur astronomers.Dobson's telescopes featured a simplified mechanical design that was easy to manufacture from readily available components to create a large, portable, low-cost telescope. With the mount level, you can swivel the telescope around on a plane parallel to your horizon and then tilt it up and down from there (Fig.f). Barlow A Barlow Lens increases the magnification of an eyepiece by adding additional lenses into the lightpath. Here is an analysis of your telescope's performance using the parameters selected above: This Week's Sky at a Glance, January 1 – 9, This Week's Sky at a Glance, December 2 – 10. Pointing an altitude-azimuth (alt-az) mounted telescope, such as a Dobsonian, is relatively easy. To use this calculator properly, you'll need to know a few basic details about your telescope and eyepieces. Quantity ... more impressive in supporting you on that journey than the Explore Scientific Generation II 12 inch Truss Tube Dobsonian Telescope. However, Dobsonian telescopes are distinguished by a rocker box with an alt-azimuth mount and a lazy-susan-style base. If you see any problems with this telescope calculator tool, or any of our interactive tools, please send an email to help@skyandtelescope.com. as the title suggests what is the normal method for finding stars/nebulae etc.does it involve angles etc or is it a case of know roughly where to look then search using the finder scope? Too few and the image will be 'under-sampled’, the stars will appear blocky and angular'. What’s good about a Dobsonian… With a Dobsonian, you get to learn about planets, stars, star clusters, nebulae, deep sky objects (e.g. July 28, 2006, By: Alan MacRobert Dobsonian telescopes are popular instruments. Sky & Telescope maintains a strict policy of editorial independence from the AAS and its research publications in reporting developments in astronomy to readers. To confirm know whether or not your telescope needs collimating, there is a simple test using out-of-focus star images, which is also referred to as the star test for telescopes. Scope Focal Ratio (f/number): A lens or mirror’s focal length divided by its aperture. Canada, Meade, Celestron, Sky-Watcher, Vixen, Takhashi, Explorer scientific Dobsonian Telescopes. It consists of a Newtonian tube assembly riding on a simple, wooden altazimuth base. After all, a Dob is a reflector. The telescope’s focal length (for example, 1200mm) 2. All rights reserved. Just plug in the dimensions of your telescope mirror, select a support configuration, and compute the mirror surface deformation. Dobsonian Telescopes have large apertures, allowing observers to set up at dark sky locations and observe star clusters with ease. Obtaining an outstanding mirror cell design has never been this easy! A Dobsonian telescope, simply put, is a Newtonian OTA (optical tube assembly) mounted on an alt/az mount. We are your source for astronomy telescopes, eyepieces, astroimaging cameras, and more! For a 20 nm RMS surface error (corresponding to 3/8 wave of astigmatism in Aberrator) the star image is clearly astigmatic: Welcome to the Mirror Edge Support Calculator. You don't need to use the calculation feature - just scroll down the output table to find the formula you need. When you're out observing, you might reach out for that high-power lens to clarify features inaccessible from low-power eyepieces. By: Adrian R. Ashford and David Tytell It is calculated by dividing the focal length of the telescope (usually marked on the optical tube) by the focal length of the eyepiece (both in millimeters). For a smoother more natural look more pixels are required, but not too many because if you use more pixels than are necessary to achieve round stars the image is 'over-sampled’. For a star to retain it's round shape when viewed on your screen or photograph it’s diameter must cover a sufficient number of pixels. This tool can help you to choose or validate the lateral support of your telescope mirror - the part of the mirror cell that supports the Defocus slightly to see if you can see the primary mirror's edge (hint: look for the edge clips). Find out using this telescope calculator. Telescope Calculator Inputs: Scope Aperture: The diameter of a telescope’s main lens or mirror — and the scope’s most important attribute. The design of such platforms was first described by Adrien Poncet and later further pushed by Alan Gee and Georges d'Autume (see below). Calculates the friction of movement for a Dobsonian telescope. Please select one of 458 telescopes from the drop-down box, or use Manual mode to enter the aperture and focal length by hand. (You can unsubscribe anytime). An essential feature of John Dobson's telescope design is that the telescope moves smoothly and precisely about the sky, staying put once the operator let's go. the diffraction pattern is egg-shaped and oriented differently in and out of focus. Over-sampled images look rather nice because the stars are round with smooth edges but if you have more pixels tha… There is no clamping or locking down. To get started, we just need two numbers: 1. By: Alan MacRobert August 31, 2017 Failing that, you can always visit the website of your telescope or eyepiece manufacturer. There are two common types of reflector telescope — the Newtonian and the Dobsonian. Dobs since then have morphed quite a bit; truss tubes, outstanding optics, GoTo and tracking capabilities, etc. Dobsonian telescopes are classic Newtonian telescopes in terms of the tube and optics. More About Dobsonian Telescopes The Dobsonian is a simple, low-cost telescope design popularized by San Francisco amateur astronomer John Dobson in the 1970s. 0, Yes, I would like to receive emails from Sky & Telescope. I hope you enjoyed my article on the best Dobsonian telescopes. 5 Best Astrophotography Books for 2021. Fields initially containing "calc'd" and/or are bordered in RED are always calculated and cannot be manually entered ... true field of view (TFOV), effective field of view (EFOV), apparent field of view (AFOV), telescope focal length (TFL) and eyepiece focal length (EPFL) are related by the following equations: TFOV=FSD*57.3/TFL; EFOV=FSD*57.3/EPFL; EFOV=TFOV*(TFL/EPFL). Sky & Telescope is part of AAS Sky Publishing, LLC, a wholly owned subsidiary of the American Astronomical Society. Copyright ©2021 AAS Sky Publishing LLC. They provide large apertures for a reasonable price and as such are suited to observing faint, deep-sky objects. Factor: x : Please use the multiselector to choose your eyepieces from a selection of 1559. 0 Item(s) We're always open, and delivering. The answer is the equatorial platform or equatorial table, which serves as a tracking platform for the Dobsonian telescope. An EQ platform serves as an equatorially mounted table for the telescope, which is used instead of the ground board. At the 10 nm RMS level an experienced observer would just be able to spot the astigmatism. For instance, a telescope with an 80-mm-wide lens and a 400-mm focal length has a focal ratio of f/5. December 20, 2013, By: Kelly Beatty If so then your eye covers that exit pupil. 5 Best Telescope Eyepieces for you in 2021 .