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Old 28-10-2006, 05:59 PM
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davidpretorius
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Peltiers - negative boundary layer and some photos

Well, last night was a great night.

Forecast of 0 degrees, the low pressure system had gone thru by 6pm, and a lovely clear night ensued!!! The only downer was wind from the south = not great seeing.

Turned the peltiers and internal fans and also the side mounted boundary layer one and went to bed.

Got up at 3am and went outside. Mirror -3.5 degrees, ambient -2.7 degrees. AND No, i do not have that back the front.

Started some collimation and got some very nice diffraction rings but as the clouds came in the ambient rose to -1 degrees, the diffreaction rings messed up which confirmed what bird and others have said, there were negative boundary layer issues. With a 2.5 degree difference, but this time the mirror was 2.5 degrees cooler than ambient.

I had some lovely views as the clouds went away and the ambient went back to -2 and by then the mirror had warmed to -2 as well. The prevailing wind meant the seeing was not great, but I knew everything that could be under my control was!

Finished off the morning by grabbing the little binos and sitting back and just panning between m45 and eta carina. Saw 2 meteors that left trails of 1 second.

So nice and peaceful, took me back to rumples and i were at snake valley earlier this year watching the sun come up...................
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Old 28-10-2006, 06:14 PM
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ving (David)
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crikey dave! how much extra did you say that weighed?
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Old 28-10-2006, 06:25 PM
bird (Anthony Wesley)
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Lookin good DP.

Bird
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Old 28-10-2006, 06:49 PM
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asimov (John)
Planet photographer

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Hey look! theres lil' spider lovin' munchkin! Hi sweetheart!!

Good one Davo!
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Old 28-10-2006, 06:56 PM
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davidpretorius
lots of eyes on you!

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not sur on the weight ving, but the two welder magnets balance it.

I should add that I need an 8 amp battery charger to keep the 12 volt 7amp hr sealed battery fully charged. There is a fair old amp draw, so a 240 volt source converting to 12 volt would be recommended and basically essentially
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Old 28-10-2006, 08:15 PM
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Photon
Illuminating the Universe

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Hi David,
I wondered where you got to last evening, my hunch was right!! It looks like you have a good quality battery charger so you can leave it connected to the battery while the system is running. Do you do that? It will operate the peltiers somewhere around 13.5 to 14.5 volts or higher just like if your DSE fridge was plugged into the car with the engine running, and the battery won't go flat it will be like a float charge situation with power being supplied from the charger.
The setup is working really well from your last night experience. I can give you a hand with the power distribution and setup, maybe offer some advice sometime if you would like?
Regards IanG
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Old 28-10-2006, 09:04 PM
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davidpretorius
lots of eyes on you!

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would love the help Ian

dp
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Old 29-10-2006, 08:52 AM
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iceman (Mike)
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Looks great! -2 ouch!

It's a beast!
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Old 29-10-2006, 08:59 AM
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davidpretorius
lots of eyes on you!

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Quote:
Originally Posted by iceman
Looks great! -2 ouch!

It's a beast!
yup welcome to Tassie!
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Old 29-10-2006, 04:36 PM
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Hi David,
I'll give you a call tomorrow, I'll be out this evening, we'll organise a get together.
Regards IanG
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Old 29-10-2006, 06:31 PM
Dobman (Simon)
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Hi dave, nice photos. I'm curious about the peltiers. my dob has a very small fan on it (standard bintel issue) & I'm thinking of putting a bigger one on it. While I'm at it I'm thinking of changing to a peltier instead, Is it a simple case of mounting the peltier where the old fan was or do you need to do what you've done to insulate the whole thing? I'll only be doing visual observing so i guess mirror temps are'nt as critical as when you do your imaging but I'm really getting into planetary viewing & would love to get more detail out of Jupiter & the like.
Ps really good presentation at the Planetarium the other nite
simon
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