Last time I was out imaging, at the end of the night a USB port on my laptop died. Really died. This left me with a single USB 2.0 port, on an aging laptop. I'd been planning a move to a solution like a compute stick but had wanted to wait for them to mature a bit more (and get 4gb of ram). Since I didn't want to replace my laptop, I went with the compute stick now. There's been plenty said about how they work, and I have nothing much to add there. 2gb of ram is enough for the polemaster, phd2, and SGP to run. It plate solved fine and ran fine through the night, so not rehashing that. What I wanted to post about was my solution to locating, connecting, and powering my compute stick.
I've had this in mind for a long time, but had wanted to do it after I got a new mount. Since the extra money for that isn't materializing as fast as I'd hoped, I decided to just try it now anyway. I decided to make a custom mount for my compute stick, so it could be attached to the top of my scope. I have a 3d printer, and did all the design work myself in Fusion 360. I followed entilza's excellent pick of the anker USB 3.0 4 port hubs to pair with it. My design puts the hub and compute stick in one enclosure, with lots of venting (no vents on the CS are blocked) and access to all the ports. I modeled a dovetail bar to go on top of my WO Star 71, and a retaining clip to hold the CS & Hub in place. Here's the model of all 3 parts:
I went through several iterations, this is the current one. It uses a side set screw to lock in place on the dovetail.
Once I had that on my scope I considered being done, but I've always hated one thing very much: cables. I had way too many cables, and some of them (I'm looking at you, SBIG) were way short. I run on 110v power, and it was annoying seeing the power transformer box danging in the air. Not to mention the cable snags and drags that would occasionally happen. So, I decided to do something about it. I thought about buying a 12v power distribution box, but why, when you can make one? My design goals were easy: main power, switched, fused connections. 12v for my camera, 12v for my filter wheel, and 5v USB power for my compute stick & hub. Easy enough. I bought the bits, did some diagramming, more design, prototyping, and testing, and came up with this model:
It mounts on the same dovetail - the bottom prints in two pieces and is glued & screwed together. The layout is organized to keep the internal wiring as short and clean as possible. I used powerpole connectors, automotive blade fuses, and basic on/off switches. The USB step-downs were purchased off of amazon, and the case was modeled around those. I power it with a 12v bench power supply I already had. The main cables running to it are 12 gauge "Wet Noodle" cable, which is super flexible, yet can handle the current just fine. All connections from the bus bars are 16 gauge. I reversed the orientation of the powerpoles for the input power compared to my camera and filterwheel to prevent mis-connecting things (though since the FW & camera stay connected, it's basically a non-issue). They're all keyed, so connecting them backwards isn't possible.
Here's a shot of the inside of the power box all wired up:
And, finally, the fun pictures - here it is set up last night for the first time. Please excuse the picture quality, I got started later than I'd meant to and had to take these in twilight.
First pic: the scope on the mount. All the cables, etc on the scope in these first two pics now stays there, in place. I don't need to disconnect any of this post imaging session:
And, fully cabled up. There are 3 wires running from ground level up. One for a second USB hub (it's got the polemaster, mount, and a USB powered router plugged into it), +12v and -12v. That's it. The cables have a tie off point on my scope cable guide, and on the bottom end of the spot for the polar scope on my mount (also a little 3d printed guide). This gives a full range of motion, but the cable weight is barely on the scope at all. (I did forget to use the velcro tie off on the side of the power box for the 12v power lines. It's basically there just for strain relief on the connectors)
Next I plan to make a box to keep all the stuff in the duffel bag in, so it's nicely attached and organized, instead of having to be messed with and risk tangles, etc. That'll be pretty easy.
I had a lot of firsts last night with getting PHD2 & SGP going on the compute stick. I started "fresh" with both, so it took a while to get settled and imaging. Once I did, I got 4 hours of images with very few issues. I think I have a buggy USB cable on my filterwheel, it disconnected twice, and I'm unsure the driver is very happy with my QHY5L-IIM guide cam. It did eventually decide to behave and guided well once I got the balance figured out for my target. It will work much better on a beefier mount than the AVX, but it handled it OK. The scope, with all the bits attached, weighs 10.2lbs. I don't have an exact weight on the power box and compute stick, but the plastic and parts are all very light, it's a small fraction of that weight. Power and cabling was a non-issue all night, things ran smoothly, and I'd call it a very successful night.
The one issue I had that isn't really resolved (other than the possibly bad USB cable on the FW / driver issue with the guide cam) is that bahtinov grabber didn't seem to work well at all. I had to manually focus, and don't think I did all that great of a job at it.
I'd be happy to answer any questions. I'm sure one will be a parts list for the power box, it's rather simple, so I'll post it soon.
Edit to point out that I now control everything wirelessly using RDP from my laptop. I plan to work on some longer range wifi, so I can hit it from inside my friend's farm house when winter comes around!
Edited by kraegar, 23 August 2016 - 10:23 AM.