This article is dedicated to those who like Me, know how well maybe their learn star hopping, and comfortable pointing in public star partyes is, when sometimes make use of the convenient digital circles passive pointing, or possess telescopes “Go_To”, and therefore knows that, in order to maximize the pointing accuracy, needs to put Dobson telescope in perfect horizontal "air bubble" level .
The calibration of the altazimuth telescope pointings needs to, It provides the precise vertical adjustment of the instrument, that precedes the acquisition of the two star known position, so that, those with only three data, The trip computer is able to guide our aimings on any object of known coordinates.
The perfect vertical position is achieved by setting an air bubble on the cover of mirrorbox, and next doing turn round the telescope, to stop it on each foot, that will have to be adjustable (and adjusted) individually in height , as long as the full 360 ° rotation of the base of the telescope does not have more to notice horizontal displacements of the level bubble.
The feet of the Dobsonian are usually fixed, low and inconvenient to reach for adjustement, but they must offer a generous surface ground support to cope with the consistency of any soil.
My dob was born with the three "canonics" cylindrical feet 50 mm tall made by round wood, coming from sawing a wooden bar "windows curtain holder" diameter 32mm, BUT ... the making it adjustables, or replace them with adjustables other , posed me the major problem that the height of My telescope was NOT increasable, penalty loading problems on my car Ford Fiesta, and also in the luggage van of my VAN-camping car.
Watching one day a plumber to install a fitting “T brand "Plasson"” three-way TEE for polyethylene pipes (Enter word "Plasson" in the web, to see the image), I had the idea of an entirely different application of the same object, I show you here "diverted" in spartan but functional realization of the three BIG , strong and easily "adjustable feet".
The three new adjustable feet, are in fact made by sawing a suitably hydraulic fitting TEE-type "PLASSON" for polyethylene pipes, so as to obtain the three necessary pieces.
The new foot manufactured in this way, incorporating overlap completely and exactly those original hardwood, if round and with same external diameter or compatible with the internal diameter (inner-lumen) of these fittings, and therefore maintain the same previous height.
But their plastic adjustment screw with a rectangular profile (which in practice it is a large-diameter ring), It is so robust and efficient which allows a range of adjustment of up to twice the height of the leg in the original wood.
The material needed to make all three feet consists of only ONE T piece of sturdy polypropylene, type brand "Oppo" or "Plasson" (see on the internet figures and information) for polyethylene pipes, of the cost of ~ 5 euro, (Look images 1), that will be sawn into three parts in order to obtain precisely the three feet.
The fittings of this kind possess the tube closure ring, which has a robust rectangular profile thread, of coarse step from approximately 6 millimeters per revolution, that makes it easy, comfortable, fast, safety, robust and dirty-safe, the manual adjustment "in the field" the height of the telescope.
Purchased one of these plastic tee (image 1) at department brico-center or plumbing stores, you cut it with hand and in good square the three unions as per drawing figure 2, with hacksaw (Look images 3).
- The number cutting 1 of image drawing 2 It is optional for lower legs like those of my telescope photographed. The new leg goes to externally coat the existing fixed leg in wooden round having an outer diameter identical to the nominal internal diameter of the pipe for water which was intended, and that identifies the plastic connector.
- The adjustable foot is screwed on the internal wooden foot by means of only one milled head screw , whose milling the drill is formed freehand in the thread body“inside black plastic ” plastic of the inner part of the fitting, as seen in image 4.
- The three big feet ended are as in image 5
- Image 6 shows the insignificant wear even after seven years of the Dobsonian entrainment 14″ F5 on disparate terrain.
END.
Note:
1) The nominal diameters of the most common of these plastic fittings for drinking water PIPES (diameters that identify the internal light) I'm: 20; 25; 32mm. (less used even if existing are also the diameters 40; 50; 63; 75; 90 e 110mm)
2) The photos of the telescope 360 F5 refer to the nominal diameter fitting T 32 mm, that is identical to the outer diameter of the three original feet in wooden round, on which in the new “"BIG FEETS"” have been externally superimposed and each fixed with a single screw.
3) The measurements of the diameter of the adjusting feets (that is also the diameter of the adjustable feets to the ground) and the height from the ground of the overall closed leg (minimum height adjustment) , or all unscrewed, and then "high" (maximum height adjustment) They are the following:
Nominal connection T Ø ——- Ø threaded mechanical ring (Ring is "Ghiera" in italian) ——- Height foot
20mm ————————— 42mm ——–22mm minimum and 45-50 mm maximum
25mm ————————— 52mm ——– 27mm minimum and 55-60 mm maximum
32mm ————————— 64mm ——– 45mm minimum and 75-80 mm maximum