New toy and DIY
June 12th, 2009
The weather for June has been pretty much shocking so far, opportunity’s for any observing or imaging are few and far between and the weather is unlikely to improve for another week or so. All the more annoying as my little Philips SPC900NC webcam arrived!
Basically since our good friends Sarah and Mike headed off to New Zealand my wife has been badgering me to pick up a webcam for some audio / visual gossiping. However as I’m getting a camera I may as well get one that’s useful for astronomy purposes as well. The SPC900NC is much loved for this but unfortunately very difficult to find any more. I managed to pick up a second hand one from amazon and got a cheap adapter. The lens is simple to remove (pry off the shroud, unscrew the lens) and the adapter screws back in it’s place.
The plan for the webcam is two fold, first use is for imaging planets and the moon. The second is to try it for autoguiding for long exposure deep sky images. I’ll report more on both of these once I’ve had a chance to try it out.
I’ve been getting my tools out for some astro DIY over the last week. I ordered a slab of 10mm x 100mm x 400mm aluminium for a mounting plate. I had it all setup but right now it’s a little on the heavy side at over 1kg and my mount is already heading a little to close to it’s limit for my liking. This weekend I will shorten it, shape it and drill out some holes to lighten it which should solve that problem. the difference when it was mounted to the rigidity was very noticeable.
For auto guiding I need to piggy back mount my Vixen A70LF refractor onto the mount either attached to, or alongside the reflector. I have the piggyback scope rings and they mount fine onto the reflectors rings but unfortunately once everything is in place it pushes the centre of gravity of the scopes way to far out from the RA axis of the mount. This means that the single counter weight I like to use can no longer counter the pull of the telescopes even at maximum extension. I also don’t like the extra strain it puts on the two screws holding the scope rings to the dovetail bar.
The plan is to add some mounting holes to the reflectors tube rings further round to allow the refractor to mount inboard of the reflector, this will hopefully bring the centre of gravity of the scopes closer to the RA axis. I will also look at possibly mounting the tube rings directly to the mounting plate. Either way I need to bring the tubes closer to the pivot point in order that the mount may be balanced without adding to much counter weight.
Last night whilst working all this out I also made a few more adjustments to the mount, I think there still be a bit to much backlash in the RA axis but it at least moves well now as does the declination. The sphinx however remains a pig to balance, I’ve now taken to balancing roughly using the standard method then using the pitch of the motor when slewing to get it precise, once the sound is the same moving in both directions I know it’s happy.
I have read of people connecting multi meters to the motors to read off the power draw but I think that may be a project for another day.
