The View Up Here

Random scribblings about kites, photography, machining, and anything else

A Second and A First

Posted by Tom Benedict on 11/02/2012

I got out again at lunch today and flew my video assisted KAP rig for the second time. But before I did that I flew my first IR-converted camera.

The camera is a full-spectrum modified Canon Rebel XT. The conversion was done by a guy at work who did the conversion for the CFHT Cloudcams. (The camera I used is actually a backup cloudcam.) The conversion involved removing the camera’s IR blocking filter from the front of its detector, and replacing it with a piece of BK7 glass. This lets infrared light reach the camera’s detector, but still maintains the same optical depth so that the autofocus hardware in the camera still works.

The flight itself went great. It flew exactly like an unconverted camera, except I couldn’t use my video down-link with it. The camera predates live view on the Canon DSLRs. So it was back to aiming by eye. I came away with some keepers, so I’m pleased.

CFHT Headquarters in the Near IR

The flight took place near the headquarters of the Canada-France-Hawaii Telescope Corporation where I work, which is the subject of the photo. No, it’s not snowing here. That’s grass on the ground.

The camera focuses like a champ, but the exposures aren’t quite on. My guess is the exposure sensors have a different response to infrared light than the focal plane detector. For this flight I metered manually, but I think a better approach in the future would be to figure out what the exposure offset is and just dial it in with exposure compensation.

Once the IR camera was safely landed and put away, I stuck my T2i on the rig and plugged in all the video hardware. The wind was stronger than during my first flight, so no surprise landings. But it was also more turbulent. So getting the compositions I was after was harder. Still, it worked out well. Here’s the visible light version of the above photograph from a slightly different vantage point:

CFHT Headquarters

I wanted to get the whole building in the frame without the foreground building intruding, but the wind wasn’t cooperating. Still, this was a nice tight composition. Except for normal RAW processing, this is straight off the camera. No cropping, no rotating, no nothing. I am super super pleased with how well this video downlink setup is working out.

Several years ago when I first flew over CFHT HQ, I did some directly-down photos of the indoor garden and the lanai area. They were completely blind-aimed. For some of them I couldn’t see the building at all, and was going entirely by feel. I got lucky and got some good images. So I tried to do the same with this setup, where I could compose them at will.

The first, the indoor garden, worked out quite well:

Complex Rooflines

Except for a little horizontal perspective control tilt to get my horizontals horizontal, I didn’t do much of anything to this photo. It really was rotated that straight from the get-go. Ok, ok, to be fair the wind was really cooperating for this one. I had plenty of time to half-press and focus, do the final composition, and trip the shutter. Not so for the lanai:

CFHT Lanai

I really wanted this one to be as well-aligned as the previous photo, but the wind was not as cooperative. By the time I’d walked in to position to make this one, the kite was bucking around and the rig was swinging. I could get the focus and composition, but not rotation. Two out of three. If I rotated, the tilting of the rig meant I wouldn’t always get the full courtyard in the shot. I did the best I could and walked away with some good photos. As with the full building photo, this one is almost straight off the camera. Just normal RAW processing. No cropping, no rotation.

Right after tripping the shutter on this one, the wind dropped. Kite and camera started coming down a little too fast for comfort. When I set up I knew that might happen, so I used too much kite for the wind. After the wind dropped I was glad I’d made that call. It was a bit of a mad dash to bring in line and land the camera safely, but everything made it down without a scratch. Camera went back in the camera bag, KAP rig and radio went back in the KAP bag, and the kite went back in the kite bag. With ten minutes left in my lunch hour, time to go back to work.

All in all I’m liking this video down-link more and more. It’s a good direction for my KAP to go. But as I hinted at in my last post, there are some changes I’d like to make to my gear. I spent the last of my earnings from my last Getty sale picking up the hardware I need to get all this done, so it’s not a question of if. It’s a question of when:

  • I’m adding a new switch to my radio. Flipping the switch will power on all the ground-side video gear (receiver and monitor), and simultaneously trip one of the servo channels on the KAP rig. On the KAP rig I’m installing a relay switch that will power on the video transmitter power when the switch on the ground radio is flipped. So flipping this single switch off will power off all the video gear on the ground and in the air. And flipping it on will power everything up.
  • I also picked up a boost power supply. It pegs at 9.5V, but I might swap it out for a 12V unit at some point. The idea is I can feed it 6V (or anything else between 1.5V and 9.5V) and it’ll output a nicely regulated 9.5Vdc. Add a line filter to get rid of the harmonics from the switching power supply on the boost board, and I can power my video gear off of the rig’s battery.
  • Finally, I ordered some reverse polarity SMA plugs with coax tails on them. I’m planning to make a 5.8GHz cloverleaf antenna for my video transmitter and a 5.8GHz skew planar wheel antenna for the video receiver. These are circularly polarized antennas, so they should reject a lot of the linearly polarized interference from other 5.8GHz devices. They also offer some modest gain, which should make for a stronger signal overall.

Yup, I’ve caught the bug. Now I just need a weekend with good weather and clean wind to fly in. Here’s hoping it’s the one that starts tomorrow!

– Tom


One Response to “A Second and A First”

  1. Way to go Tom! I went for a 2s LiFe (6.6v) on the rig and it lasts so well I don’t worry about a switch other than ‘on/off’. When you settle into working with the vid relay you can have extraordinary ‘walking on air’ experiences which are unique to KAP…wait for the wind…enjoy!

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