*** UNDER CONSTRUCTION ***
When the 'NoIR' Pi camera (camera without the IR filter) was released it became possible to use the Pi as a 5m pixel 'astro-camera' for a fraction of the 'astronomical' prices charged for 'real' astro-cameras. However it was only with the release of the Pi Zero v2 (with camera socket) that it become possible to build all the hardware (including camera module) into a single box !
The Pi camera
The Pi camera has one of the smallest pixel sizes of any camera you can find, which is a real advantage when it comes to autoguiding and planetary imaging
The Pi camera pixel size is 1.4um, with all 5 million pixels packed into a sensor that's only 3.67 by 2.75mm. This compares to a 'typical' DSLR, such as the Canon 350D which has pixels that are 41.09 sq. µm with 8 million spread over an area 22.2 x 14.8mm The density of pixels on the Pi sensor is some 10x higher than the Canon - which means the Pi has a '10x magnification' advantage over the Canon - but it also means the Pi camera receives about 20x less light per pixel than the 350D. Further, the Pi camera pixels are not very sensitive and although it does support 'binning' (adding a 2x2 matrix of pixels together to quadruple the sensitivity) this 'cuts in' automatically on specific combinations of camera exposure settings. The Pi camera is also rather 'noisy' = it's because of the rate at which the camera accumulates 'thermal noise') that the Pi camera maximum exposure time is limited to 6 seconds (10s for the Pi camera Mk 2). Finally, the 'amplification' is limited to ISO 800
So, 'all things being equal', the Pi camera is not going to be your 'first choice' for faint nebula etc. astrophotography - instead the Pi camera's small sensor and tightly packed pixels means it can be used to great advantage as an 'autoguider' camera on a nice bright 'guide star' or for Planetary imaging
Using the 'stock' lens, the Pi camera can even be used for 'meteor watching' !
My goal was to build a more-or-less 'stand-alone' unit with all the components built into a single small box. The only decision I needed to make was how images would be 'saved' (which would then determine how the unit was powered)
My options were :- 1) A totally stand-alone self-contained unit with local (SDHC card or USB memory stick) storage and internal (or at least local) battery power 2) As per (1) but with the addition of WiFi (for both control and image 'extraction') 3) An Ethernet cable connected unit (with PoE)
I quickly decided to avoid adding batteries 'in the box' - after all, the telescope would have it's own nice big 12v lead-acid battery - so all I would need to power the Pi Astro-cam was small socket 'on the box' (and add a 12v to 5v voltage regulator 'in the box')
Adding batteries would also mean a bigger box - and adding weight would restrict 'usage' to 'proper' telescopes (a very light unit can be 'gaffer taped' to any eyepiece :-) )
The Pi zero has only a single USB socket, so I had a choice between Ethernet or WiFi. To configure the software for a totally a WiFi connected (or totally stand-alone) unit is a rather daunting task - where-as Jessie would auto-connect via Ethernet cable 'out of the box'
I thus needed to build the following into the box :-
The Pi Zero itself A USB Ethernet 'dongle' (removed from it's case) A PoE voltage regulator The Pi zero camera module (I used a 5Mpixel NoIR unit)
For hardware construction details, see the Next page
The pages in this topic are :-
+ Telescope position - (sensing) == Latest changes (modified 29th May 2018 14:35.)
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