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Polar mount stabilisation
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<blockquote data-quote="archive10" data-source="post: 935953"><p>Yes, I know.</p><p></p><p></p><p></p><p>Yes you are right I didn't Count this in - I expected you to put the L-brackets aligned with the polar axis. I didn't read from your post#5 that you intended to put the L-brackets directly behind dish. You wrote that you'd be using a prime focus dish - these normally have the mounting ring attached to the reflector in such a way that it is very difficult to move the dish anywhere in the plane described by the ring. I therefore took it that you would add the L-brackets in the mount on "the other side of the declination adjustment mechanism". </p><p></p><p>With the mount shown in the pictures (Prodelin/Echostar mount), you are right that you will be able to move the dish backwards slightly by moving is down. In fact you will achieve more than the 8 degrees - you will also add the around 23 degress of offset to the figure, so your angle would about 31 degrees.</p><p></p><p>But still the solution is a little impractical...</p><p></p><p>Even with 8 degrees (x), just sliding the dish would be a little impractical, as the distance (A) required to move the dish (and it's CG), say, 50 cms (O) backwards would require</p><p></p><p>A = O / tan(x) = 50 cm / 0,14054 = 356 cm</p><p></p><p>Firstly, this would require your dish being mounted very high.</p><p>Secondly the strain this would put on the hinged point (where the rotation around the polar axis is on the mount) would be quite substantial due to the levering effect of the is displaced dish. This would be most marked when in stormy conditions - your mount must be designed to be very strong.</p><p></p><p>With the offset dishes, however, this becomes more manageable, as the 31 degress would mean moving the dish 83 cms downwards to move the point 50 cms backwards. But still a bit impractical. I will still argue that a counterweight it probably a better mechanical design option that displacing the dish from the mount.</p><p></p><p></p><p></p><p>No, but it's a very widely used one <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite6" alt=":cool:" title="Cool :cool:" loading="lazy" data-shortname=":cool:" /> - and keeps the mount mechanics simple.</p><p></p><p>I will still argue that a counterweight it probably a better mechanical design option that displacing the dish from the mount.</p></blockquote><p></p>
[QUOTE="archive10, post: 935953"] Yes, I know. Yes you are right I didn't Count this in - I expected you to put the L-brackets aligned with the polar axis. I didn't read from your post#5 that you intended to put the L-brackets directly behind dish. You wrote that you'd be using a prime focus dish - these normally have the mounting ring attached to the reflector in such a way that it is very difficult to move the dish anywhere in the plane described by the ring. I therefore took it that you would add the L-brackets in the mount on "the other side of the declination adjustment mechanism". With the mount shown in the pictures (Prodelin/Echostar mount), you are right that you will be able to move the dish backwards slightly by moving is down. In fact you will achieve more than the 8 degrees - you will also add the around 23 degress of offset to the figure, so your angle would about 31 degrees. But still the solution is a little impractical... Even with 8 degrees (x), just sliding the dish would be a little impractical, as the distance (A) required to move the dish (and it's CG), say, 50 cms (O) backwards would require A = O / tan(x) = 50 cm / 0,14054 = 356 cm Firstly, this would require your dish being mounted very high. Secondly the strain this would put on the hinged point (where the rotation around the polar axis is on the mount) would be quite substantial due to the levering effect of the is displaced dish. This would be most marked when in stormy conditions - your mount must be designed to be very strong. With the offset dishes, however, this becomes more manageable, as the 31 degress would mean moving the dish 83 cms downwards to move the point 50 cms backwards. But still a bit impractical. I will still argue that a counterweight it probably a better mechanical design option that displacing the dish from the mount. No, but it's a very widely used one 8-) - and keeps the mount mechanics simple. I will still argue that a counterweight it probably a better mechanical design option that displacing the dish from the mount. [/QUOTE]
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