Originally posted by johnmflores Excellent as always!
Quick question - what's the limiting factor in the altitude? Sounds like the balloon popped. Was it thermal stress or something exotic like outer space particle or radiation?
Thanks. Yes, these are Kaymont weather balloons and are designed to burst when they reach a certain diameter. The pressure difference causes them to expand. You can't get a balloon much higher than 120k ft. since the atmosphere at that level is so thin. Think about releasing a ball under water. It will keep rising until it reaches the top, and there is no more buoyancy to lift it. If our balloons were not designed to burst, they would "float" until the sun degraded the latex. We have a remote cut-down system just in case it doesn't burst.
Originally posted by jjdgti Thanks for the response. Did you use some kind of time lapse to take the pictures? Or it was controlled by a PC on the ground and one device on the camera?
Did the lens was exposed to any moisture? A WR lens would be more appropriated?
We use a Pclix lt100 to do the time lapse. The lens is exposed to the atmosphere. I don't think a WR is necessary since condensation on the descent would not be reduced. If it were sealed, the pressure difference may blow the seals out.
Originally posted by jbinpg I would love to see you launch a 21Ltd glued to f8 on the next launch!!
Are you using Totex 800 gram balloons, btw?
We are using Kaymont 3000g balloons. 21mm would be ok, but f/8 may be a problem if you want to keep ISO low. The biggest problem with exposure and maintaining sharpness is
not aperture. The biggest problem is motion. If you could see the payloads swinging and spinning around during the flight, you would see what I mean. A fast shutter is extremely important. Even 1/3000s is sometimes too slow. For this flight I set to 1/4000s which is as fast as the k10d can go. The second biggest issue with sharpness is atmospheric "seeing" conditions, similar to issues in astronomy. The conditions were quite poor yesterday with stratified haze all the way up. You can see the layers in the high altitude pictures from yesterday. The Tamron at f/2.8 is sharper than many lenses stopped down, so you would see little effect of stopping down the aperture since the other issues above dominate the sharpness.
Last edited by PentaxPoke; 03-19-2010 at 05:06 PM.