Monday, May 17, 2010

Cooling fan now operational

 In preparation for the arrival of the primary mirror, I made a bracket for a sealed 12-volt lead-acid battery I bought to power the cooling fan. I located one small enough to fit in a corner of the rocker box without interfering with the mirror box, tail gate or the primary mirror itself. I MIG welded four pieces of 3/4-inch wide steel strap to make a bracket to hold the battery in place during transportation, yet allow easy removal for recharging. I made a cable from some leftover 16-gauge wire and crimped on connectors for the battery on one send, while I soldered the other end to the leads then covered the connection with shrink wrap tubing. Tie wraps anchor the leads to the tail gate and I left enough slack so I can raise and lower the telescope without pulling on the wiring. The fan's power source will be independent from the power source for the dew heaters and digital setting circles, which will draw much more current. I am considering the use of two 12-volt 18 amp-hour batteries wired in parallel to power them since the dew is extremely heavy here and the secondary mirror and finder scope dew heaters will require a lot of current. At the very least, one 18 amp-hour battery will be used which will be enough for several hours of observing, but to go all night will require a lot more power here if I have to keep dew off the finder scope, secondary mirror and coma corrector all at once. I've also replaced the nuts on the mirror clips with all metal, stainless steel lock nuts to ensure the clips will never loosen during transport.

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