In this section we will show you how to build a complete Dobsonian Telescope. The dual-axis, aluminum Johnsonian Type V platform sells for $900 and supports Dobs up to 16” or 140 pounds. The scope sits on top of the top board, which is usually another sheet of stiff plywood. Most platforms, commercial or home-built, are set for one specific latitude, although you can adjust them to ±5° or so by shimming up the north or south end. Because an EQ platform tracks equatorially rather than alt-azimuthly (as, for example, a standard fork mount without an EQ wedge or a Dob Driver does), there is no field rotation during tracking. Many amateurs choose to build their own EQ platforms to save money, as well as to customize the platform to their own preferences. The Johnsonian Type VI platform is an entry-level model that sup-ports Dobs up to 10” or 60 pounds. 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. Most EQ platforms tilt from about -7.5° through vertical to +7.5°. 0000006011 00000 n The Box: ½ inch N-N birch plywood. DOBSONIAN TELESCOPE PLANS PDF - Since you are reading this, you are probably considering to build your own Dobsonian telescope. Or at least it doesn’t unless you put it on an equatorial platform. PM builds one and speaks to John Dobson, the man behind the plans… The first step to building a Dobsonian telescope is to choose the aperture size and the focal length. And the particularly nice thing is: it works equally well even for larger Dobsonians. It just doesn’t look like a standard GEM or fork equatorial mount. (Well, all but one; the Dob is still an altazimuth scope in terms of motions, which means you can’t use the old EQ guys’ trick of locating a bright object and then using the RA or declination slow motion controls to repoint the scope to a dim object on the same RA or declination line.) For this telescope, you need a PVC drain tube. When you use an EQ platform, you continue to point the Dob normally, moving it in altitude and azimuth to locate objects. 0000001231 00000 n 0000050350 00000 n The only downside is that a Dob doesn’t track the motion of the stars. 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. =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�� Polar alignment within a couple degrees is sufficient for visual use. BUILDING a DOBSONIAN TELESCOPE MOUNT Step 1: BUILDING THE ADJUSTABLE CRADLE. Figure 4-37. Dob Mount Plans - posted in ATM, Optics and DIY Forum: Hi, everyone ! Get Astronomy Hacks now with O’Reilly online learning. The Dobsonian mount was a wonderful innovation.It’s simple, inexpensive, smooth, extremely stable, and intuitive to use. http://www.johnsonian.com) and Tom Osypowski(http://astronomy-mall.com/regular/products/eq_platforms/). Our Dobsonian Mount. Roger had built the ‘scope to provide a home for a beautiful 12.5″ f/5 mirror he had made. The Bearings: ¾ inch N-N birch plywood. Printer friendly version of these plans (*.pdf) What is an Dobsonian? The only downside is that a Dob doesn’t track the motion of the stars. Many thousands of astronomers have constructed their own Dobsonians, but the satisfaction of building your own mount is immense. The bearing dimensions are calculated for the specific latitude at which the platform is to be used. An equatorial platform,or EQ platform for short, is a squat, flat, motor-driven table that sits underneath the Dob base and gradually pivots the scope at the exact rate needed to counteract the apparent motion of the stars.