Low cost robotic DSLR-based imaging system

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Overview, Project goals

Image of the robotic camera system on Mauna Loa observatory. Mauna Kea, to the North, can be seen in the background on the left.
The cameras are mounted on an equatorial motorized mount on top of a metallic frame. The domes on the right host the VYSOS project robotic telescopes.
View pointing South. The Mauna Loa solar observatory is in the background. Openings for the two objectives can be seen on the front of the cameras enclosure. Note that the system does not have a dome, and simply points down during daytime or bad weather. The small shiny box on the right of the camera system is hosting humidity, temperature and cloud sensors.
Skycam is a small experimental low-cost robotic wide field imaging system for astronomy and atmospheric science based on a low-cost digital single lens reflex (DSLR) camera. The project is a collaboration with the NSF-funded VYSOS project. The system is located at the Mauna Loa Observatory, an excellent site for nighttime astronomy.
This project is aimed at exploring a low-cost approach to perform a scientifically useful all-sky 3-color imaging survey. The system was installed on Mauna Loa observatory in December 2010, and started fully robotic operation in early 2011 with a single camera. It was upgraded to a 2-camera system in summer 2011. The first year of observations (until summer 2012) was used to evaluate scientific performance and system reliability, as well as develop data reduction algorithms which will process the large volume of data acquired. This project focuses especially on:
  • Low surface brightness observations of the night sky, large size features (atmospheric and astronomical)
  • High precision photometry in 3 colors simultaneously (variable stars, exoplanet transits)

Open source hardware & software

This webpage contains technical details of the system and all source code developed to run the system. It is meant to help other amateur and professional astronomers duplicate and improve this approach. Feel free to use all material in this webpage, with no restriction. I of course appreciate if you let me know if you are working on similar things, or if you have comments to improve the system / report bugs.

Future plans

Following this 1-yr experimental period, I hope to partner with other amateur / professional astronomers to scale up / duplicate / improve this sytem. The low cost of the system, its ability to produce well calibrated 3-color photometry (under study) and ease of making pretty images open up exciting possibility for both astronomical research and outreach.


Technical Overview

The imaging system consists of two commercial digital cameras: models Canon 500D and 550D. The Canon 500D native IR-blocking filter in front of the sensor was replaced with a filter offering higher transmission in the red, as described in http://www.naoj.org/staff/guyon/08astrophoto.web/03canon500dmod.web/content.html . The 550D is unmodified and includes the native IR-blocking filter. The two cameras combination therefore offers six different colors. Each camera is equipped with a 85mm focal length lens at F1.2 (Canon EF 85mm f/1.2L II USM). The cameras are pointed at the same direction, and mounted on a 2-axis equatorial mount (Orion Atlas EQ-G). The system (camera + mount) is computer controlled with a laptop. The data is stored on the laptop hard drive, and copied to an external hard drive.
The main system characteristics are listed in the table below.
Camera 1 Camera 2
Camera body Canon 500D Canon 550D
Field of view 150 sq. deg (10 x 15 deg) 150 sq. deg (10 x 15 deg)
Aperture 70mm diam 70mm diam
Pixel size 10" 10"
Detector CMOS color detectors, 15 CMOS color detector, 18 Mpix
Sensitivity Photon noise limited, mV ~ 15.5 point source sensitivity in 4mn

The data volume is approximately 5 GB per night, stored locally. The data is physically retrieved every ~2 month by copying it to an external drive (2 month of data = 300 GB). The average total power consumption is about 25W (including approximately 10W for laptop) at night, and 15W during the day.

Durability, reliability, exposure to weather

The durability of the system is a big concern. To keep the system simple and low cost, it does not have a dome: the camera points down when it rains/snows or when there are clouds.

The system includes several sensors to determine if the weather is suitable for observing:

  • Three webcams acquire images every minute, and are used to automatically confirm nighttime (which is primarly derived from the Sun altitude below the horizon, according to the computer clock). Visual inspection of the webcam images can also identify snow/ice on the mount or camera.
  • Temperature probes facing the sky and the ground are used to detect clear sky at night: if the sky is clear, the upward looking temperature probe is colder than the downward looking probe (thermal radiation to the sky). If this temperature difference is larger than a preset limit, then the sky is deemed clear and observing can start.
  • A humidity sensor is used
In addition to these sensors, the weather information provided by the VYSOS observatory and the the Mauna Loa observatory are downloaded evry minute from the network. Decision to observe is made from all sensor values.

The system is designed to minimize the long-term impact of weather :

  • no exposed plastic (to avoid UV degradation of plastics)
  • mount has been sealed against water with silicone
  • camera is sealed (cover) except at the front (lens) which points down when weather is bad
  • use of weather-resistant materials when possible: Aluminum instead of steel when possible, Stainless instead of standard steel for bolts/nuts, use of Kapton tape when tape must be exposed.


Links to other sites

Jerry Lodriguss's DSLR website: Nikon vs Canon digital SRL Cameras for Astrophotography

Page content last updated: 27/06/2023 06:35:52 HST
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