dobsonian mount plans

BUILDING a DOBSONIAN TELESCOPE MOUNT Step 1: BUILDING THE ADJUSTABLE CRADLE. Dobsonian telescopes get their name from their creator, John Dobson, who combined the simplicity of a Newtonian telescope with an Alt-Azimuth mount. The only downside is that a Dob doesn’t track the motion of the stars. When the EQ platform reaches the end of its travel, you simply reset it for another hour’s worth of tracking. The Dobsonian mount was a wonderful innovation.It’s simple, inexpensive, smooth, extremely stable, and intuitive to use. Step 2: BUILDING THE ALTITUDE BEARINGS. It connects via a drive shaft to the drive wheel visible at right in the aluminum bracket assembly. The white box on the left contains the electronics that control the speed of the platform’s motion. You can do an eyeball alignment on Polaris, or use a compass (adjusting for magnetic declination, of course) to align the platform accurately enough for visual use up to 300X or more. If you’re comfortable with the idea of building a platform from scratch, you can probably do so for $150 to $200 in materials and two or three weekends’ work. If you have a 150 mm F8 mirror, a 200 mm OD tube is needed. You’ll need to calculate dimensions, center of gravity, bearing curves, and so on for yourself, but there are spreadsheets and other tools available to help with all that. Figure 4-37. 0000007447 00000 n Dobson made the telescope completely from simple, ordinary household items; a process that you can replicate yourself. Between the two boards sit the north and south bearings, a small motor, and some sort of drive mechanism that tilts the top board (and scope)to track the stars. Both of these come highly recommended by their owners, but neither is inexpensive. 0000001891 00000 n Most EQ platforms tilt from about -7.5° through vertical to +7.5°. <<84C4D296C278124C9CD84E74DF99174E>]>> 0000001506 00000 n It is an Newtonian optical tube, mounted on a very simple, yet very stable and easy to use alt azimuth mount. The yellow Optical Tube Assembly is a 6-inch f/7.5 Newtonian. The Bearings: ¾ inch N-N birch plywood. 0000006011 00000 n 565 0 obj<>stream The ground board, bearings, and drive mechanism of an equatorial platform. The mirror is gorgeous, as is typical for Roger who is one of the best opticians I know. Or at least it doesn’t unless you put it on an equatorial platform. You, too, can avoid astronomical costs by watching stars through a tricked-out cardboard tube. Although these prices sound high, compared to the price of a traditional equatorial mount large enough to support scopes that size, a platform starts to sound like a bargain. Roger had built the ‘scope to provide a home for a beautiful 12.5″ f/5 mirror he had made. Large Dobs already require a stepladder to reach the eyepiece when the scope is pointed near zenith, so another 6” of height might be the last thing you want. http://www.johnsonian.com) and Tom Osypowski(http://astronomy-mall.com/regular/products/eq_platforms/). Here are several online resources to help you get started: eqplatforms group (http://groups.yahoo.com/group/eqplatforms), Chuck Shaw’s EQ platform page (http://www.atmsite.org/contrib/Shaw/platform/), Jan van Gastel’s EQ platform page (http://home.wanadoo.nl/jhm.vangastel/Astronomy/Poncet/e_index.htm), Don Odegard’s EQ platform page (http://home.att.net/~segelstein/don/platform-1.html), David Shouldice’s EQ platform page (http://members.tripod.com/denverastro/dsdfile/dspfile.htm), Tom Hole’s EQ platform page (http://www.tomhole.com/EQ%20Platform.htm). 0000062802 00000 n In this section we will show you how to build a complete Dobsonian Telescope. Length = 16". The difference is, when you stop moving the Dob, it begins tracking and the object in the eyepiece remains centered rather than drifting out of view as Earth rotates. © 2020, O’Reilly Media, Inc. All trademarks and registered trademarks appearing on oreilly.com are the property of their respective owners. =o�(��u�GIH��~"��&�*� ��w�uX�� eEf�Cz�Ӯ��vS[�l~C��;�I��@��Y��3��T�}XJ?c =(-d� N�ż=�ς8)�#8��p�Ћa�X1\jD��?^e)n�� S�w�0W�>.1��\��b�g%L��l��i�Ѧ��4�+� ¯�u� ��O��6�l�7w��ҿ`n?wj��}�ݎ��Ҽ��eb��y8�M�� An equatorial platform at one extreme of its motion, tilted about 7.5° off vertical. DOBSONIAN TELESCOPE PLANS PDF - Since you are reading this, you are probably considering to build your own Dobsonian telescope. For visual use, a rough polar alignment works fine. For small Dobs, this may actually be welcome. 0000062837 00000 n The equatorial platform pivots on the curved bearing shown in Figure 4-37, as well as a similar bearing at the far end of the platform, not visible in the figure. Homemade 12.5 Inch Dobsonian Telescope: How to build a 12.5 inch closed tube Dobsonian telescope. The bearing dimensions are calculated for the specific latitude at which the platform is to be used. You also need to … For astrophotography, the polar alignment needs to be much more precise. Figure 4-39. The sample we will build is a 6-inch f/7.5, however the plans can be scaled down to 4-inch scopes and up to 10- or 12-inch scopes of various focal ratios. The stepper motor, which actually moves the platform, is visible in the oval cutout. In practice, that means that most platforms are made for the owner’s specific latitude, but are usable anywhere within 350 miles north or south of that location. That drive wheel bears against and drives the curved bearing surface connected to the top board, upon which the scope rests. Here you will find plans to build this telescope, or a smaller one--either a 4.5", a six-inch, or an eight-inch--of identical design. %PDF-1.6 %�� Some time ago my friend Bill Lofquist bought a dobsonian telescope from Roger Ceragioli. An EQ platform is simple in concept. An EQ platform may not be the best choice for large Dobs because it raises the Dob (and the eyepiece height) by 6” or so. Many amateurs choose to build their own EQ platforms to save money, as well as to customize the platform to their own preferences. Figure4-37 shows an EQ platform built by Steve Childers, underneath the rocker box of his 10” Orion XT10 Dob. We have documented our build with downloadable photographs available from the link at the top of this article so you can replicate the parts, but because your choice of drive motor and power supply could differ according to circumstances and availability you may have to adapt the design a little to suit your … That means an EQ platform, if it is built precisely and polar aligned accurately, can be used for long-exposure astrophotography without requiring hardware or software field derotators. The Dobsonian mount was a wonderful innovation.It’s simple, inexpensive, smooth, extremely stable, and intuitive to use. You simply place the EQ platform with the north-south central axis pointing more or less north. I recently received a homemade 6 Newtonian reflector and I need to build a dobsonian mount for it. O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers. It just doesn’t look like a standard GEM or fork equatorial mount. 0000003202 00000 n 541 25 There is a relatively simple method to realize an equatorial mount for Dobsonians, particularly if you are interested in visual use only. Exercise your consumer rights by contacting us at donotsell@oreilly.com. When you use an EQ platform, you continue to point the Dob normally, moving it in altitude and azimuth to locate objects.