Still no temp probe arrival so I contacted them at Deal Extreme. The website says up to 20 days to arrive, the agent on Live Chat says 2 - 6 weeks !!! Please wait 2 more weeks ....
Extremely frustrating.
In the meantime the weather has turned to complete custard anyway, wind, rain, minor flooding. Glad we stayed home and had a quiet Xmas.
OK, so bored but thought I'd do some improvements to the 450D.
First, the massive heat sink is overkill, I'm only cooling a very small part so save some weight and go back to my earlier design with some modifications.
Second, get rid of some weight and improve access to the USB port. Hacked off some of the alum base unit, another 10 gms gone, 10% improvement.
In anticipation of the temp probe arrival one day added a 6 block terminal across the back for fan, TEC, and probe.
See pix below, ignore the long screw, no wiring and taped back, that's temporary till the temp probe and TEC addition sets final measurements for everything.
THEN ...... !!!
The Mum in law walks up the driveway and hands me a package, came in the mail she says. With feverish excitement I rip it open and lo and behold there it is. With 4 probes in total on one meter leads. I can just include a probe in any future build and bingo. Tested ok in the fridge
Got some urgent shopping to do first and fishing tomorrow so not quite sure when I'll get to it but I'll find time as soon as possible.
Probe was placed against what appears to be a metal frame integral to the sensor. I assume it goes all the way round as it is evident on the other side so best easily accessible point to monitor the sensor. Re-assembled, tidiest build I've done in a long time. Normally I've got wires and things hanging off in all directions
Ambient start temp 25*C and once I turned the TEC around the right way (Doh!) it went to work.
Started at 5 volts to TEC and fan and got to 6.3 below ambient in 5 mins. No problems so went to 12 volts both. Heat sink definitely got quite a bit hotter and got down to 12.3*C after another 15 mins.
Thermal output from the heat sink eased as it approached 15*C so appears to be about right sized for the task.
Few minor tidying up tasks to do then I'll start my 'Clewd go away' dance and see how it all goes.
Theoretically if the maxim is true and the noise drops by 50% for every 5* drop then my noise should be only about 12% of what it was previously.
Ha I like that light Brent. If your running a 12706 TEC you should be able to go closer to zero from that ambient, depending on which version your using; there seem to be different load rates on various 12706 TECs depending on suppliers. I noticed some way below in this thread that you said it is a 50W version (I think). How many amps were you applying and how?
If it is running optimally and well matched to the heat sink and fan you should not notice much heat at all on the base of the heat sink as it would be being extracted as fast as it arrived and not allowed to build up.
I recall that Rowland had developed a fan/heatsink sizing theory to match TEC capability to optimal heat extraction equipment; I believe it was along the lines of needing to double the watts of the heatsink fan combo from the TEC wattage. In other words, a 50W TEC would need a 100W heatsink/fan combo.
I believe your fan is too small, you could try putting your fan on top of the heatsink and use it to pull air through and out.
Following the Tellurex guidelines it turns out that the heatsink fan combo needs to be roughly twice the rating of the supplied power. Basically, any heatsink that is cable of 100 to 120watt dissipation is more than adequate for a typical 40 x 40 12v 6A setup, which typically runs somewhere between 3 - 5 amps, with cold finger temperature measured near the entry point of the finger to the back of the sensor. Design seems to be the key. That heatsink looks OK but probably needs a bigger fan if it is getting hot.
The heatsink on my setup is anodised extruded aluminium ~110 x 65 x 30mm with fins of 2mm spaced at slightly less than 2mm with a 70mm fan, if that is helpful. Temperature drop of 28 - 25C.
Argghh!!! Now everything is working except the camera ... error 99 !!
Yeah, you're probably right about the heatsink and fan, a bit more oomph could be useful. I have bigger units and bigger fans too, might go back to my finned tower configuration as it was so light. Just got to fix the camera first !!
I'm pushing 12 volts at about 3.5 amps so nominally 42 watts which is about right. 14.5 volts is supposed to be the 50 watt mark.
I've just stripped the camera down and rechecked all the connectors, reseated most and secured all earthing points. No luck, time to sleep on it. Maybe it will fix itself overnight, ... yeah right.
Error 99 can be many things. Check the mirror and shutter flaps to make sure they are not jammed. Removed the memory card and battery and wait 30 minutes for internal capacitors to drain. Make sure it is in manual model. If that does not resolve it then go back and check the ribbon cables again and the mainboard side connector (the white one). Good luck.
And success !!!
Did a careful reseat of all connectors and she came back to life, beginning to love this little camera
Upgraded to my tower radiator system and reconstructed the back. Then out to the Ob and the 12v5v supply.
Ambient 22.2, went straight to 12 volt mode.
At 8 mins 30 secs I had 1.8*C ... and stable.
Ran 20 darks, 30 secs. ISO 1600
BYE reported the temp as going from 21* internally to 25*
Temp probe on sensor climbed to 2.4*
Normally 20 darks would push the temp about 5* above ambient so the cooling has some effect elsewhere in the camera but more importantly it is managing the sensor extremely well. I'll get sub zero temps at night so the next project is to make an adjustable power supply. Might trundle round to Jaycar later and have a look at some stuff.
A 20*C delta is brilliant. Noise should be at about 6% of ambient level theoretically.
Now I just have to get rid of the clouds that came in the probe box ....
Another test I ran later.
Camera is now on the scope and the ambient was 25.8*c
Got down to 5.5*C in 15 minutes, tested the 5v hold point at about 12-13*c. Could be useful in the winter.
The T-Adapter stays close to ambient which is good, very little parasitic heat leakage which was an issue with the cold box designs done earlier.
I've Velcroed the meter up on the side on the upper scope saddle.
Then to finish the day off I got the Ob PC onto the home network and installed Team Viewer so I can sit inside in the warm and run the imaging.
Next stage is to get PC control of the mount itself I guess.
Now about those damn clouds !
(Weather report is not good for the next 3-4 days so need to find more projects to do )
Sounds good Brent, that's a good Delta T. Re the clouds, watch out for the big mess headed your way across the Tasman. I've had six days of rain and today is the first day of semi-clear sky since last Friday. Hope it misses you.
Sounds good Brent, that's a good Delta T. Re the clouds, watch out for the big mess headed your way across the Tasman. I've had six days of rain and today is the first day of semi-clear sky since last Friday. Hope it misses you.
Yeah, no, that's what's heading our way. Most of it should hit the South Island tomorrow but Auckland is predicted to get very heavy rain and some thunder around midday. Fortunately with two harbours and lots of water courses it gets away pretty quickly and we only ever get minor flooding on rare occasions. Tops up the water reservoirs nicely anyway, we're sitting at 80% or so and it keeps the lawns green.
Just compared uncooled to cooled darks. The uncooled darks show a number of white pixels, the cooled a lot less and mainly red. The 450D was pretty damn good uncooled to begin with but this might let me do longer exposures especially as it is also Ha modded.
I'm collecting a cooled darks ref library, re-arranging my PC folder structure to better manage imaging tasks. Looking at getting a NAS cos the collection is growing.
The things you find to keep you busy on a wet day ...
OK, shooting through some sucker holes in the clouds running at 5 volts on TEC and Fan it sat at 6.7*C. Ambient was 16*C
M42 with 5 X 20 second frames at ISO 1600, 6.7 C at the probe (BYE showing 20*C.) No Ha filter so plenty of IR.
I need to clean the sensor and there is minimal processing, levels only, no darks but showing a lot more nebulosity than my previous images of the region. It's a pretty bad image really but proves operation and function.
Stripped and cleaned the sensor and the sensor side of the front window but looks like there is still some gunk on the other side I guess. It's a sod to try and get it completely clean.
I'm tossing up whether to just remove the window completely and use the Ha filter on the nose piece.
Other than that It's working well, did some solar imaging yesterday ( was intending to test last night but the clouds came in) and even through the N5 film it is seeing some IR data.
Also did bias and flats for the reference library for both the 450 and 1200, had trouble finding a 'white' T shirt ..... LOL
IR image overlaid on non IR image of M42.
Shows how the IR component becomes more extent in the nebulosity. Also tends to 'soften' the stars but I'm not sure that is IR out of focus slightly or just more dust being visible.
Bit of fiddling and rotating to get it aligned but interesting...
Brent which scope was that taken through? It shows the classic Achro colour effect I believe. I would agree it is probably slightly out of focus, the gas clouds should have much sharper definition. It might be that your getting some fogging in the camera or the IR Cut. If the sensor coverglass is fogging up it could produce that effect. My suggestion: dry the camera out completely (stick it out in the sun with everything opened up (battery compartment, memory card hatch, adaptor or filters off, take the back off if you want, etc)). Put it in a sealed container with some silicia moisture absorbing packs and leave it for a couple of days. Then seal it inside a ziplock bag with a cutout for the T-thread adaptor (see my Argon bag technique in Rowlands Cold Finger thread). Leave some moisture absorbing sachets in the ziplock bag. You don't need to use Argon to test but for long moist nights it works well. Do some test shots again and see if the fogging is still there. Just my 2 cents.
Glen, it was on the Lunt but I've been having some mount problems (erratic guiding) and it was only 5 frames shot between the clouds so don't read too much into the quality. I think I'll be removing the front glass filter anyway and relying on the Ha 2" to manage it all. I've also rebalanced the mount and ran the PHD2 alignment process. I think it was the offset balance that was causing the erratic corrections (fingers crossed). Otherwise I'll be pulling the mount apart next for clean and grease.
What do you think about removing the front glass ?
On another note slightly I've been working on the 8F8 Astrograph I built last year. Wasn't quite happy how it turned out mechanically so added some stiffening to the front struts cage and improved the UTA shielding and stiffness. Hadn't even thought about fitting the 450D to it but look at the pix. It squeaks in with a bit of room to spare.
Now watch the clouds come in with a vengeance.....
