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  • Author Author: doorknob
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Getting started with Gertduino - A Faire trial...

doorknob

Things have been pretty quiet for me on the blogging front for the last week, but I have a good excuse.

 

I have been getting ready to show off my work-in-progress all-sky camera (two of them, actually) at the Westport (CT) Mini Maker Faire, scheduled for Saturday, April 26. The Faire was sponsored by the Westport Library, the same organization that had sponsored my month-long stint as "Maker in Residence", and so I was sure to find plenty of interest in seeing my progress in building the cameras.

 

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There's nothing quite like a deadline to focus your thoughts and energy. I put in a marathon session at the Makerspace to rebuild a version of my "Camera #1" design with an improved layout and dimensions, and finally managed to pull things together by about 11:00 PM on Friday evening.

 

It rained (and rained, and rained) all Friday night and early Saturday morning, and for a time it looked like the day might be a washout, but the rain finally subsided about an hour ahead of the opening of the Faire.

 

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Estimated attendance was several thousand people and countless robots.

 

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I set up a table with my prototypes for Camera #1 and Camera #2 in the "Maker in Residence" section of the Library's Great Hall, just outside the Library's Makerspace, sharing the area with other 'maker' projects such as a fold-up mobile office, a collaborative, accordian-style book, and an Arduino-powered collaborative quilt.

 

Camera #1 is the one that has the Gertduino mounted front-and-center. I do not yet have the Gertduino doing productive work within the camera housing (such as coordinating sensor readings) - that will come along over the next week or so - but I explained its key role in the camera design as I described the purpose and goals of the all-sky camera to visitors who stopped by to chat.

 

The concept behind Camera #1 is to take photos of the full sky by mounting a super-wide-angle fisheye lens adapter in front of an upward-pointing Raspberry Pi camera module's lens. You can see Camera #1 propped up on its custom PVC tubing stand at the left of the photo below - the Gertduino is clearly visible:

 

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Camera #2 is visible at the right of the photo. Its design relies on an upward-pointing hemispherical mirror reflecting the sky for a downward-pointing Raspberry Pi camera module to capture. I haven't taken any photos with Camera #1 yet, but here's a sample photo from Camera #2:

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Today is a day of rest. I'll get back to working with the Gertduino tomorrow.

  • in reply to doorknob

    Yea, fisheye lenses are very tough to get with no distortion.

    I have heard that aspheric lenses are better, but I have not tried any of them.

    I suspect that you can get by with just 160 degree field of view, given the normal ground clutter.  It would also give you a better f-number ratio.

     

    It looks like Camera 2 would reduce blockage if you went to thinner metal rods instead of the PVC, but you might run into wind vibration issues.

     

    I look forward to seeing your cameras in action.

     

    DAB

  • in reply to DAB

    DAB,

     

    Yes, Camera #1 should give an obstruction-free view, but the low-cost fisheye adapter lens suffers from focus problems and optical aberrations. So Camera #2 may turn out to have the upper hand as far as image quality is concerned.

     

    I have seen articles suggesting that a parabolic mirror may be better adapted to the sky photography application than a hemispherical mirror, but parabolic mirrors do not appear to be available off-the-shelf (at least, not at as low a price as the hemisphere). My goal for these camera designs is for them to be easily replicable with common materials, and so a custom parabolic mirror is pretty much out of the question (I have looked into possibly machining a mirror out of aluminum, or using vapor deposition of aluminum onto a plastic base, but both would be cost-prohibitive).

     

    I'd love to take some lightning photos, although the combination of tall trees in my yard and years of experience indicating that thunderstorms seem to mostly miss my neighborhood (due, I suspect, to local topography) may make it difficult to get a really satisfactory photo or video. The Pi camera module has some delay (that I have not found out how to eliminate) when taking still photos, but the latest firmware update to the camera appears to have added some interesting high-definition video modes which may turn out to be suitable for grabbing lightning videos. I have seen some great lightning photos taken with Canon point-and-shoot cameras using the CHDK firmware with automatically-triggered exposures, and would like to be able to do the same with the Pi, but it's not yet clear to me that it can be accomplished. I need to do a lot more work than I have done so far with the Pi's camera capture software, but I have some additional work to do on the electronics, network support, and camera user interface software before I get to do that.

     

    As for Camera #2, I hope to refine the camera support so that only a single arm is required, rather than a tripod. Camera #2 has always been intended as a proof-of-concept rig, rather than a weather-hardened camera, but the goal for Camera #1 is for it to be able to sit out in the weather 24/7/365.

  • Hi Ed,

     

    I like your approach.  Camera one gives you less obstructions and might end up being more sensitive to light.

    I have seen a lot of designs like camera two and they are very good, but you have to work out the spherical distortion to do a lot of good measurement of location of objects.

     

    I look forward to seeing your cameras in action.  Are you thinking of using the rig for lightning photographs?

    Could be interesting.

     

    DAB