Quote:
Originally Posted by ving
OIC!
so you were just cutting back light so you could capture the moon... god i am slow.  |
Yep, thats it.
Quote:
Originally Posted by rat156
Hi Fred,
The other narrowband filters will do the same as the Ha filter, i.e. just cut the light down.
The sun emits a pretty much continuous spectrum of light over this range and the moon simply acts as a mirror (though some bits will be absorbed, our instruments aren't sensitive enough to detect this) so you'll just get darker frames.
If you recombine in the time honoured Hubble pallete, you'll get an idea of the spectral output of the sun, though the light and dark regions should be slightly different colours as the scattering off the moons surface will effect some wavelengths more than others depending on the surface. This is the only reason we see different shades of grey in the first place.
Cheers
Stuart
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Ive since seen some full NB moon images, not that attractive, what you say makes sense, thanks.
Quote:
Originally Posted by Ian Robinson
One word .... WOW !!!!
Not much interested in the moon .... the other photos I am wowwed by.
How's the camera cooling arrangement coming along. I would have thought that thermoelectric cooling would be more efficient and easier to impliment. I know TE is used in industrial thermography cameras and it is very efficient , I've used them in very hot environments ring next to steel furnaces and steel rolling mills (ambient temps over 50oC where we were where making observations and producing thermographic images).
TE cold sides maximum current ranges from 0.3 to 10 Amp, single stage DT - 74oC to 150oC in multi-stage configurations. See http://www.rmtltd.ru/tec_modules.htm...FRpciAodBi_W4g
In summer that would give you a chip temp about -40oC and a dark current <0.05 electrons / pixcel / sec !!!.
(http://www.sbig.com/sbwgifs/4020_dar...temp_graph.gif ) |
Thanks Ian. The project came to a screaming stop for a variety of reasons, but it was fun trying, and I learnt a lot. They can be efficient, but designing all the mechanics to make the overall result efficient (cold chip) was hard. Stacking was tricky, a triple stack was very unstable and ranaway thermally in seconds, even double stck in the end wasnt worth it and I ended up with 1 on each side of the cooling finger. The stacking is more complicated than simply stacking, the heat generated from a lower unit was way more than the cooling effect of the one above it, so there must be carefull power managment involved in commercial designs to keep it stable (I didnt want to spend that much).
The finger was inefficient, thermal fllow was restricted by a narrow neck. Other designs such as the cam Houhgy has, come out the side of the camera without this restriction.
I used cooled water instead of air cooling, which worked very well, but it got difficult to manage tubes and wiring on the scope, more work would have fixed that. I was determined to get a very large delta or not bother at all, so another problem was constant addition of ice.
Frosting killed it in the end, a sealed bag and lots of dessicant just didnt work.
I could have done lots more work to fix all of this, but then the 40D came along, so that was it, why bother
. I find the noise of the 40D, at ambient winter night temps anyway, and lots of stacking, is fine. And going lower than -10 deg, as the graph you posted shows, is fairly marginal unless your really fussy.