The architecture
A 300W array charges a 100Ah LFP battery in a ventilated/weatherproof observatory power box. A fused 12V distribution panel feeds mount and dew controllers; regulated buck/boost converters provide 5V USB-C and clean 12–19V rails for camera/mini-PC gear. Avoid an inverter unless a device truly requires AC.
Load and sizing math
Dew heaters are the wild card. A humid night can double energy use compared with a dry one.
| Load | Watts | Hours/day | Daily Wh | Notes |
|---|---|---|---|---|
| Mount | 12 | 8 | 96 | Tracking average |
| Cooled camera | 25 | 8 | 200 | Cooling + electronics |
| Mini PC / router | 20 | 8 | 160 | Control stack |
| Dew heaters | 35 | 5 | 175 | Average PWM duty |
| Focuser / accessories | 8 | 3 | 24 | Intermittent |
| Illustrative total | 655 Wh/day | Before system margin | ||
The sample night is about 655Wh. A 100Ah LFP bank provides ~1.28kWh nominal, leaving margin. A 300W array can recover the used energy in a few good sun hours, though winter imaging seasons may justify 400W.
Full parts list
This is a shopping architecture, not a demand that you buy one exact brand. Match voltage, current and connectors before ordering. Budget ranges reflect the class of hardware rather than a live quote.
300W solar array
Target spec: 3×100W or similar, MPPT-friendly string
Daytime recharge sized for real overnight imaging.
Budget: $160–$400 each
100Ah LiFePO4 battery
Target spec: 12.8V, low-temp protection
Enough energy for a long imaging night with dew reserve.
Budget: $150–$300 each
30A MPPT controller
Target spec: LFP profile, Bluetooth optional
Tracks array efficiently and logs recovery.
Budget: $80–$180 each
12V fused distribution + regulated outputs
Target spec: Individual branches, USB-C PD and 12/19V regulators
Prevents one accessory fault from killing the whole night.
Budget: $35–$100 each
Dew controller
Target spec: PWM, 2–4 channels
Controls the biggest variable load rather than running straps full power.
Budget: $35–$120 each
Weatherproof battery enclosure
Target spec: Ventilated, insulated as climate requires
Keeps electronics dry and cables organized.
Budget: $40–$120 each
Wiring map
Give noisy computing gear and dew heaters separate fused branches from sensitive mount/camera power.
[300W PV]-->[30A MPPT]-->[100Ah LFP]
|
[FUSED BUS]
_____________|_____________
| | |
Mount Camera rail Dew PWM
| Mini PC/USB |
12V clean regulators Dew straps
Step-by-step build
Measure the night's real loads
If you already image, use a DC wattmeter during a session. Dew power and cooled-camera draw vary too much to guess perfectly.
Choose battery location
Keep the bank out of direct dew and within safe temperature limits. Short battery-to-bus wiring matters.
Install the array
Place panels where they will not cast new afternoon shadows onto the telescope area or interfere with the roof/roll-off path.
Mount the MPPT and bus
Use a backboard with labeled fuses for mount, camera/computer, dew, network and accessories.
Build regulated outputs
Set every buck/boost converter with a meter before connecting expensive astronomy gear.
Route observatory cabling
Separate data/USB from high-current heater wiring where practical. Use strain relief at moving axes.
Run a daytime dummy load
Power a resistive/test load for several hours to confirm battery capacity and controller charging.
Run a full imaging night
Log start/end SOC, dew duty cycle and voltage. Adjust panel/battery sizing based on the worst clear night, not the easiest one.
Commission it before you trust it
The project is not finished when the LED comes on. Run it through a controlled test so the first real failure is not in the field.
- Battery temp within range
- All DC outputs verified by meter
- Mount polarity confirmed
- Camera rail voltage confirmed
- Dew channels individually fused
- Roof/roll-off path cable-free
- No cable snag during full slew
- Night SOC logged
- Next-day recharge verified
Mistakes to avoid
Undersizing the battery because the panel is large
Panels make energy only when conditions cooperate. The battery has to carry the load through night, cloud and short high-demand events. Size energy storage from watt-hours, not panel watts.
Ignoring standby loads
Controllers, routers, cameras, inverters and cellular hardware can consume power 24/7. On small projects, a 5W always-on device is 120Wh per day—sometimes more than the 'main' load.
Using one fuse for the entire project
Fuse each branch according to its conductor and load. The fuse protects wire, not the gadget. A downstream short should not require an oversized main fuse to clear.
Mounting the panel where the project is instead of where the sun is
The load can sit in shade. The panel cannot. Use a cable run, pole or remote mount to put the collector in the best solar window.
Skipping a low-voltage disconnect
Deep-discharge protection is cheap insurance. Many charge controllers or smart battery systems can disconnect noncritical loads before the battery is abused.
Upgrade path
Add a weather safety relay
A rain/cloud sensor can park the mount or close a roof automatically.
Add 400W of PV for winter
Long winter nights and low sun make more panel disproportionately useful.
Add remote monitoring
A shunt and networked controller let you confirm SOC before deciding to start an unattended imaging run.
Frequently asked questions
Can I just use a portable power station?
Yes for a portable rig, but a fixed DC system avoids conversion loss and scales more cleanly for dew heaters and observatory automation.
How much battery do dew heaters use?
It varies with humidity, aperture and controller duty cycle; measure your actual straps.
Do I need 120V AC?
Usually not. Most astronomy gear is natively DC or USB powered.
Affiliate disclosure: SolarBuild.co participates in Amazon Associates, eBay Partner Network, BLUETTI via CJ Affiliate and Renogy via Impact. We may earn a commission from qualifying purchases at no extra cost to you.