The Starry Night, 41

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01/19/2011. This works because in some ways a telescope is very like a log:




Custom LeatherCraft C390 Canvas  Log  OTA Carrier

by Custom Leathercraft

List Price: $17.99
Price: $16.05
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In Stock. Ships from and sold by Deerso. [Found on Amazon]

There are a couple of ways to arrange the sling, and both get you a soft and convenient handle for the telescope. It avoids the awkward balance, the sharp edges, and all those tempting but delicate grapples that make carrying 35 lbs of tricked out optics uncomfortable. And you only have to heist it inches off the ground to get it form here to there. I haven't found a downside to this yet.


01/20/2011. Out of practice & out of spec. I put connectors on each end of a 500 foot spool of CAT5e cable. It took me half an hour. Then I plugged one end into a Linksys wireless bridge. I turned the netbook's wifi receiver off and plugged the cable into its network jack.

I haz ethernet!





Next, I'll run (more likely stumble) the cable up through the woods to the cul de sac, complete the 12v DC version of the power box, and then we'll give it a try.


1/22/2011. Or not. The prospect of laying and maintaining that long wire in the woods was getting on my nerves. Friends raise a lot of good points that will demand some attention. Late last night, I realized that if I'm not having to cut the distance to the bare minimum out of consideration for the ethernet standard, then I might as well lay the cable up the driveway when needed and roll it up when not. Forget all that work that would come from trenching and maybe having to use PVC conduit to protect a permanent wire from deer and squirrels and beavers and minks and badgers and lions and mice and assorted other denizens of the woods. Just spool it out and wind it up as needed. That would minimize danger from lightning surges, too, since nothing would be routinely hooked up to either end of a 500 foot lightning antenna. Setting out the wire only as needed would solve a lot of problems. I found some excellent tools for doing just that (check out the Quickwinder 225, for example).

And yet, getting rid of the long run of wire would be even better. This morning I finally saw an easy way to do that. It's not the most elegant solution that comes to mind, but it uses only parts that are on hand and it's reasonably frugal with power.


I put the 12vDC kit in order. It doesn't sound like these small projects should have taken all afternoon, but I find electricity tedious and confusing, especially when playing with expensive gear that will give me longterm grief if I set it up wrong or marginally. I opted for a relatively wire-free solution:

  • Linksys Wifi bridge, powered by a dedicated AGM battery: I measured the polarity of the plug for the Linksys wireless bridge (tip +5v) and clipped the wire from the AC power wart. The black wire is - and the white stripe +. I hardwired the plug to a 12v motorcycle battery (bought a few years back to try to rejuvenate the BMW) after finding documentation that the bridge would be happy with anything from 5v to 18v. I taped the bridge to the side of the battery. It works fine. It's now a single, portable use-it-anywhere sort of device. I can pick up a wifi signal and put it on a cable wherever that signal happens to be. At a guess, the battery should be good for 40 hours or more. Set this at the top of the driveway.

  • Aspire One Computer charger / adapter, powered by a 70AH deep-cycle lead acid battery: I dug out a universal DC adapter, set it for 19v and plugged it into the battery I intend to use in the cul de sac to power most of the gear. I verified voltage and polarity and plugged it into the Aspire One. Bingo: the netbook has its power source. It shouldn't draw much; just enough to keep its humongous internal battery charged. 2A when running with no internal battery at all, less any other time, right? I could leave this plug unused until the computer's battery monitor indicates that internal power is low and only then trudge up to the observing site to plug in the computer. But would that maximize run time or only serve to demand more juice late? Anyway, put the computer within USB range of cameras and mount and get data to and from it via an ethernet wire.

  • A-P Mount, powered by the deep-cycle lead acid battery: The Mach1 will draw up to 3A when slewing, maybe more in cold weather, but typical guiding loads are on order of 0.5A. I didn't test this today because I've run the mount from 12v sources before. Eventually, you can command motions and slews, but for now we're just guiding and the netbook takes care of all of that.

  • SBIG ST2000XM CCD, also powered by the deep-cycle lead acid battery: I worked on the terminals of the battery box to accomodate the clamps supplied with the SBIG 12v power supply. I plugged the CCD into the battery, attached its USB cable to its accustomed computer port and launched Nebulosity. All works as expected. Tally another 2A with the Peltier cooler running near maximum power.

I believe we're looking at 12-18 hours of juice for this outfit. There may or may not be issues with the mount and CCD sharing the same DC power source.

Here's how the pieces fit together, graphically demonstrated:


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Outbound commands are shown in red, inbound data in blue.

My office computer is situated in the southwest corner of the house. It's connected to the home network run by wifi router with an omni directional antenna. A wifi repeater (powered via extension cord) sits about 40 feet from my desk outside the south windows. Its antenna stands at the focus of a parabolic reflector aimed at the cul de sac. A command is issued by the desktop, put out on the router, picked up by the repeater, and beamed toward the cul de sac at the top of the driveway about 450 feet away.

Up in the cul de sac, the signal is picked up by a wifi bridge attached to a 12v motorcycle battery and put on a CAT5e ethernet cable which carries it to the netbook computer. (Why use this step? Why not beam the signal straight to the netbook? The clear line of sight up the gently curved driveway through a slalom of pines is only a few degrees wide, so any receiver up top has to sit in a very limited area at the top of the driveway. That means that the signal has to be redistributed across the cul de sac in order to take advantage of the multiple observing sites up there. Another repeater would do, but I don't have one handy. What I have is a wireless bridge and a wire. There are pros and cons to doing it this way anyway.) The notebook computer communicates with the guide camera, the imaging camera, and the guide port on the mount by USB2.

Data from the instruments (and software conversations from the computer) are returned over the same path in reverse. The bridge takes them off the wire and sends them out as omnidirectional 803.11g wifi. The parabolic antenna at the foot of the driveway picks that up and the repeater at its focus repeats them. The router in my office "hears" the signal leaking past the parabolic reflector. The router puts it on my desktop and there you go: I sit at my usual desktop computer (in shirt sleeves, of course, with coffee in hand) and watch the netbook's screen via Remote PC. I might as well be at the keyboard up in the cul de sac. I monitor guiding, change filters, monitor imaging stats and inspect subframes via PC Remote. Windows' native networking features let me transfer files from the netbook's data-collection directories to the desktop where so I can play with images as they accumulate. (Eventually I'll add aiming and focusing abilities.)

Simple, eh? No wires running through walls or windows, and no 400 foot lightning-, mouse-, deer- and squirrel-magnet strung through or buried in the woods.


1/24/2011. I measured the cul de sac. The pavement is 75-80 feet across (hard to call the center and stretch the tape and be really sure, but it's close enough). If it's 80 feet across then it's about 260 feet around. Half that, 130 feet, would let me get from any point on the perimeter to any other. So let's make a 150 foot cable and call it enough. That should let me reach any point I need without crossing the right of way leading in and out of the cul de sac and allow me to park the telescope on the shoulder beyond the pavement if needed.

The scheme works fine: I set it all up and ran the cable around the cul de sac and on up the road to see how far it would reach. I plugged it into the netbook's ethernet port and checked news and stocks.

Lesson of the day: 500 feet of cable in a box seems very tame and easy to carry around. 150 feet in the wild is a very large and awkward wad, even in daylight, even at comfortable temperatures. A cable reel would make life much simpler, especially in the dark and in the cold (eBay to the rescue; nothing as fancy as a Quickwinder is needed for this shorter wire so I bought a much more humble reel). When it would suffice, a shorter cable would also make life easier (I made a 15 footer to mess with).

Then I looked for clear skies in the forecast, and, finding none, I turned to SkyGlobe for help deciding what to image first under this wider sky. I think I'll start with a long series of the Horsehead and then an honest beginning on the Trio in Leo. Soon, I'll do a photometric run of U Geminorum, then an exoplanet. Also soon, I'll try NGC 4565 and take a lot more data of IC 443 and the Rosette... This is great!


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                   © 2011, David Cortner