My goal with my “micro-observatory” project is to be able to set up a self-powered astrophotography system that can remain in place through any weather while protecting the equipment, be operational and ready to image within a couple minutes, and be moveable--if necessary. I don’t need it to be fully automated for now. This is a fairly complicated setup, and so I’m going to take this in steps. The main missing piece of automation is raising and lowering the lid. Of course, all the astro gear is automated, except for a motorized cap, which won’t be necessary without the ability to remotely open and close the lid.
I started testing this idea a couple years ago with wood frames, and even did some research on wood shipping crates. I settled on this plastic molded shipping container with 27”/68.5cm interior dimensions--it’s a cube. So far, this looks like it might work. The stock hardware is crap--I already drilled off the hinges, and I’m looking at 180 degree hinge mechanisms and other options for lifting the lid away with minimal obstruction of the sky (https://youtu.be/6bMMZq0X29E). Whatever I end up with will have to be pretty sturdy because I’ll be mounting a 50 watt solar panel on the lid to keep the batteries charged.
As far as project progress, I’m still at the beginning. I’m testing out different mount/scope configurations for fit--with the scope and counterweights horizontal. I was surprised to find the Orion Atlas EQ-G fit with a small refractor--just barely, and only with west-side travel and no meridian flips. (I had to move the mount and aluminum mounting frame all the way to one side to make this configuration fit). Today I’m trying out the iOptron CEM25P, with the hope that this will fit entirely in the box, centered, and be able to do flips and reach most of the sky.
I’m going to spend a while doing weather and motion testing, anchoring to the ground and monitoring temperature and humidity. It’s water-tight, so I’m not worried about leaks. I just don’t want internal temps or condensation to build up this time of year, or in the winter, to drop below the equipment specs. I haven’t decided what I’ll do for warmth when it’s cold outside. It’s not unusual for the temperature to remain well below freezing for extended periods of time (-6F / -20C is not unusual).
Much to do. I’ll keep you posted!
Tonight I'll be testing out the prototype for my DIY version of the Pegasus Astro Pocket Powerbox--well, a manual operation version. There's no ASCOM or INDI support, but with what I've put together here--12vdc line in, 3 x regulated 12v dc 4 amp out, 2 x PWM-controlled dew control RCA jacks (potentiometer with the silver knob controls output temp). Add an Arduino, a few relays, and a temp sensor and I can build all the powerbox features I use. One reason I'm going down this path (I have a pocket powerbox on my GT81 narrowband setup and I love it) is that the Pegasus Astro version doesn't provide 5v dc output, and I want 5v with up to 4 amps out to power the Raspberry Pi 4 + 4GB RAM I'll be building out later this year, running INDI/Ekos/Kstars or Stellarmate. There's also a big price difference. I threw this together for about 15 USD, and I think I paid $180 for the PPB. I'll let you know how it goes!
Here's my test setup for tonight--testing the DIY Pocket Powerbox. This is my ZWO ASI071MC with a Nikon 180mm f/2.8 lens, ZWO ASI120MM-S + 130mm guiding, on my trusty old iOptron CEM25P mount. That's my prototype pocket powerbox on the back, behind the main imaging camera. I'm going to be doing some long exposure color shots in Vulpecula--Sh 2-92, NGC 6820.
The problem I want to solve is supplying 12v dc power to my astro setups away from mains/grid power, for example, a 110v ac line running from the house. I want enough storage to last a full night with everything--even the big power drains like thermo-electric cooling and dew control covered by the system. Of course there are off-the-shelf solutions for this, but I wanted a little more versatility, a system that I can upgrade, add more batteries if needed, and this is much cheaper than the portable power options out there. It's also specific to my needs: a handful of 12vdc devices, with varying current requirements. (I don't need a built-in flash light or an inverter to power AC devices--things that plug into a wall socket).
Here's what I've put together and successfully tested so far:
I bought a small deep-cycle 35 amp-hour lead-acid (AGM) battery, which will get me completely through a night of astro-imaging: through evening setup, an entire night's imaging run with a cooled camera (TEC set to -20C) and dew control running the whole time. In my first tests I discovered I would not go any smaller than the 35Ah @12v dc battery, because I ended the night with it pretty close to completely discharged. Keep in mind the charging cycle with AGMs is a gradual process that uses lower power. Absorbent Glass Mat batteries are safer to use, but require a slower, steadier charging cycle.
Everything I purchased for my power box was perfect except I went underpowered on the charger. The NOCO chargers are awesome (https://no.co). I bought the NOCO Genius G1100 (1.1 amp) and I should have gone with with the G3500 (3.5 amp)--for $20 USD more. The G1100 will charge my NPP NP12-35Ah AGM battery from dead to full in 18 hours. Yeah, see the problem? That's not going to work with more than one clear night in a row. The G3500 will charge the battery in less than 6 hours.
I have everything housed in an old milk crate--an original from the early '80s. But you can buy similar containers today--at Amazon, the Container Store. I attached two pieces of scrap acrylic to two sides. I have my Fanless Windows 10 box secured to one, and I drilled out the other side for my battery power cut-out. I added this so there was no draw on the battery--even minimal. The three switches on the rocker panel are lit when they have power, even when they're off. They have a small LED bar that shows that the switches are functioning, and a brighter red LED when they are powered on. The cut-out also allows me to completely separate the lines running to my gear from the NOCO charging line, if I want to.
Tools: wire cutters, wire stripper, soldering iron + solder, and the crimping tool for the connectors (link below)
NOCO chargers https://no.co
NPP NP12-35Ah Rechargeable AGM Deep Cycle 12V 35Ah Battery with Button Style Terminals
Rocker Switch Panel
NOCO GC018 12V Adapter Plug Socket with Eyelet Terminal
NOCO Genius G3500 6V/12V 3.5 Amp Battery Charger and Maintainer
Car Battery Switche MAX 50V DC 50A
Insulated Wire Electrical Connectors Assortment
Ratcheting Crimper Tool - for the connectors above
Primary Wire, 14-Gauge Bulk Spool, 100-Feet, Red & Black
3 x 6ft 2.1mm x 5.5mm Extension Cable, 18AWG for 12V
Power Pigtail Cables, 12V 5A Male and Female Connectors
AstroTrackerHD Prototype 4 in testing, with pics. (HD = harmonic drive, which is a high-precision, high-torque, zero backlash gear set. See: https://youtu.be/3mWemlMEzFk). I did some code cleanup and refactoring for version 4.0.7, and added the ability to adjust the speed in small increments and save the speed values to eeprom. I have a couple posts on this earlier in the year, but if you haven't seen them: AstroTrackerHD is my project to build a very accurate star tracker using a NEMA 17 stepper, 139:1 ratio planetary gear feeding a 100:1 ratio harmonic drive. I'm running updated software in this one, and I'm in the process of 3D printing some brackets for the stepper.
Star Tracker Build: the 100:1 reduction Harmonic Drive gearhead arrived today, and I'm planning out the mechanics for the direct drive train and structure for a case (3D printing a prototype case that will hold everything together tonight). Harmonic drives are the way to go if you're looking for extreme precision, zero backlash, and just plain cool technology: https://www.youtube.com/watch?v=3mWemlMEzFk I will be using the original iOptron CEM25P saddle for testing, and the threaded holes in the harmonic drive line up neatly. Gearhead specs here: http://www.harmonicdrive.net/products/servo-mount-gearheads/harmonic-drive/csf-gh/14/csf-14-100-gh
My purpose was to avoid running another USB cable from the iOptron hand controller to the Raspberry Pi3B+, using iOptron's Wifi-to-serial adapter, "StarFi". Here's the basic setup: you plug in the hand controller normally. The adapter comes with two short cables with RJ jacks. The four lead RJ11 cable goes from the RS232 port on the StarFi to the serial port on the hand controller, and the 6 lead RJ-12 runs from the StarFi "Port" to the "iOptron Port" on the CEM25P mount. The instructions guide your through adding the device to your network and using it with ASCOM. I had no problem setting it up with Ekos/INDI, using an IP address instead of a serial port.
I bought Stellarmate OS in October and installed it on a Raspberry Pi3b+ (The latest Pi with a 1.4GHz 64-bit quad-core processor, dual-band wireless, and Bluetooth 4.2/BLE). This system is now running the INDI server core of my astro setup, and I replaced the second Pi in my "distributed INDI-based astro-imaging setup" post with an iOptron StarFi wireless telescope (mount) adapter. For the Orion Atlas EQ-G mount I'm using the Shoestring bluetooth-to-serial adapter (BT2EQ6 Bluetooth Module with DB-9 connector). I bought an inexpensive GPS dongle to get position and system time for Ekos and KStars. So far, Stellarmate is working out well. The only downside I have experienced is common on any remote astro system, that's the delays in the capture and focus workflows for large FITS files. My Atik 414EX had larger pixels and lower resolution, and ended up with 16-bit FITS files around 3 or 4 MB, while my higher resolution ZWOs (ASI071MC and ASI1600MM-P) are ten times that size.
There were several high-quality 60mm apochromatic refractors that entered the market last year. They were pitched as portable wide-field scopes, and also marketed here in the US for the solar eclipse last summer. Starting around $450 USD, these little refractors, like the William Optics ZenithStar 61 sold out quickly. I didn’t get a chance to purchase one until May of this year.
The ZS61 has a 360mm focal length at f/5.9, synthetic fluorite objective lens--FPL-53, which has some amazing optical properties. It’s a great scope, with a solid focuser. But there’s an easy modification that will make it even better. I found one thing when I added the imaging train--here’s my narrowband setup, with an Atik414EX monochrome CCD, a ZWO filter wheel with 5 filters, hydrogen-alpha, oxygen3, sulfur2, clear, and a near IR 685nm longpass. With the field flattener this ends up around 3.2 pounds or 1.45kg. These scopes--I keep saying these scopes because there are several varieties of the same basic components, a few of them with the same focuser, focal length, and aperture, differing--as far as I can tell--only with the hardware, knobs, lens caps.
Anyway, the first thing you probably want to do with these is strengthen the scope’s connection to the dovetail bar. The stock version comes with this clamshell ring and shoe, and if you’re going to do anything other than some light visual astronomy, you will want to backup the stock ring with another. I found that when I added the camera, filter wheel, and guider, the whole system had a slight flex to it if I lifted or pushed down with the camera. At first I thought it was the focuser and was a bit bummed about that, but then I noticed it was the whole scope moving, and it all relied on this rather slender ring and shoe. The focuser itself is very smooth and very solid. It’s a dual-speed rack-and-pinion type, and so you may want to adjust some of the tension screws depending on the load you’re planning to add--a DSLR or more, but out of the box, this focuser along with FPL-53 glass makes this scope worth considering for your wider-field work.
To remove that flexure in the system, I bought a ZWO 78mm Holder Ring for ASI Cooled Cameras to see if it would work. The tube’s diameter is around 76mm, and with a delrin shim or something similar, the 78mm inside diameter of the ZWO ring worked almost perfectly. The one gap--literally--was with the two shoes of each ring. The stock William Optics one is ¼” (6.35mm) taller than the ZWO ring. Easy solution: I went to my favorite aluminum supplier (you have one, right? See the links below) and bought a set of stock aluminum pieces, 2” x 3” x ¼”, then drilled, and stacked it with the dual ring setup. Now the whole system is perfectly rigid with two strong foundations.
The other advantage of going with the ZWO holder ring are the risers with the threaded holes on the top and bottom. I added one of these SmallRig cheese grater mounting plates on the top--you should always have one or two of these on hand for bolting things together. They’re tough, anodized aluminum, and full of threaded holes of varying sizes. I use these on the ZS61 and my William Optics GT81 to connect the control hardware and power--usually a Raspberry Pi3b and 12v battery pack. What’s nice is I can use a couple hexcap screws to quickly add or remove all devices from one scope to the other.
So, there you have it. An easy way to build more rigidity into a nearly perfect portable wide-field setup. Let me know if you have questions, or a better way to accomplish this. I added some links below for the components I used.
For aluminum: Stoners Tools and Raw Materials
Ebay listing for the 2” x 3” x ¼” aluminum bar stock: