Debayering a DSLR's Bayer matrix.

[russellhq]

Yeah, you need to look up your psychrometric charts or get a calculator.

I was thinking that the air in your freezer should have a lower water content to start with. Maybe worth filling your box with air from there

[Gina]

Yeah, you need to look up your psychrometric charts or get a calculator.

I was thinking that the air in your freezer should have a lower water content to start with. Maybe worth filling your box with air from there

OK I'll try that

[Gina]

Not true actually - RH = 74% for air from freezer   Living room RH = 43% according to my wal thermometer and humidity meter.

Edited April 23, 2014 by Gina

[russellhq]

RH is higher because it's colder. But you should find that the absolute humidity is lower.

[Gina]

You may be right but I opened the lid in the living room and changed the air and immediately got RH or 47% at about the same temperature when the lid was back on.  I think the silica gel held the temperature.

[Gina]

A bit later and the humidity is getting back to where it was but with a lower temperature.

[Gina]

It seems that after an hour the RH has stabilised at around 15% at 20C giving a dewpoint of -7C.  I think the limit may be due to the fact that there is currently a gap where the wires to the DHT22 go past the box top seal.  I shall have to seal the box before any futher testing to be meaningful.

[StuartJPP]

This thread is the best weather indicator out there...the worse the weather the longer it gets...

I have got an old Canon 1100D and am reading and waiting for you guys to get something reliable before I take a stab at it

[Gina]

This thread is the best weather indicator out there...the worse the weather the longer it gets...

I have got an old Canon 1100D and am reading and waiting for you guys to get something reliable before I take a stab at it

There may be a slim chance of imaging tonight - keeping fingers crossed

I shall do my best to try and provide as reliable a method as possible - I realise that others may follow my example and the responsibility this entails

Edited April 23, 2014 by Gina

[Gina]

A small advance on the cover glass replacement mechanism design.  A soft sponge pad connects the cover glass to a flat piece of plastic or metal which in turn is attached to the shaft.  If I don't have the 3D printer I plan to use a sleeve on the shaft with the flat plate glued to it.  If printed in plastic this can be all one piece - a tight fit on the shaft.

The pad, placed in the centre of the glass will provide equal pressure all round the edge to ensure it sticks well, allowing for a slight misalignment.

[Gina]

With the box sealed and 8 bags of silica gel in it the dewpoint has now reached  -10C after 30m.  It is still slowly going down so I'm hopeful of reaching -15C in time   I think this will be quite sufficient.  In my tests a year or two ago I went down to -20C but the noise reduction between -10C and -20C was small.  I am now content that I can achieve low enough humidity - next I need to perfect the machanism for replacing the cover glass within the dry box.

It may not be necessary to use that many bags - the main point will be to reduce the amount of free air.  In that way the amount of moisture in the box after closing the lid will also be reduced.

Edited April 23, 2014 by Gina

[russellhq]

With the box sealed and 8 bags of silica gel in it the dewpoint has now reached  -10C after 30m.  It is still slowly going down so I'm hopeful of reaching -15C in time   I think this will be quite sufficient.  In my tests a year or two ago I went down to -20C but the noise reduction between -10C and -20C was small.

The tests from elenhinan also suggest there is little to be gained from going below 0°C.

https://ragnablade.myon.no/?page_id=11&page=3

[Gina]

Yes, I remember reading that.  I don't think there's any doubt that I can get the humidity low enough.

Next thing I'm working on is the cooling.  Now where's that 1100D with the cold finger hiding???

[Gina]

Found the other 1100D body with the cold finger coming out the back   So one option is to use that and perform all the removal of unwanted parts anew.  However, I should have all the bits that went into the last cooled 1100D system and that would save work and laeve some complete parts (as it were) for selling off (if I can be bothered ).  I've also found another complete untouched 1100D body that appears to be in full working order.

BTW - I am imaging tonight - adding Ha to the M51 data   Still upping the exposure time to get more data ah the signal is much lower with Ha even binned 2x2.

Edited April 24, 2014 by Gina

[Ptarmigan]

I've also found another complete untouched 1100D body that appears to be in full working order.

They have been breeding while your back was turned !

[Gina]

So it would seem

Tested the 1100D with cold finger in normal mode with SD card and battery, and although it apperared to work normally there was no image on the SD card.  So I'm going to bring the laptop in from the warm room and test it with APT.  Just realised that I probably turned off "Save to SD card" in the optiond   Didn't think of that when I tried it last night - doh

[Gina]

I've just checked the figures my Arduino sketch is providing with an online calculator for dewpoint and the calculator shows about -25C whereas my sketch is showing -11 for temp of 18C and RH of 13    I got the DP calculation sketch from the Arduino web site!

[libraryman]

Still looking out the bits and pieces to make up the test rig.  Can't find the Peltier TEC I was going to use - a 12v 3A one from Farnel and more efficient than the Chinese ones.  However, I do have a 3.3v 2A one (TEC1-4902) about 7W I/P power and a 50mm square CPU cooler.  I have that setup running now and the cold side has already collected a thick layer of ice

Hi Gina, are the 30x30mm tecs efficient enough for cooling the cold finger? I have 2 12703 & a 12706 both 40mm sguare, I looked on farnell's site for the 3 amp one but struggled to find it, have yo a link to it?

Ray

[Gina]

Now received the epoxy potting resin from Maplin and started transfering to containers.  These two photos show the resin pack as supplied and the resin part of the pack transferred to two plastic pots with screw lids.  Or most of it there is a little bit left in the bag but I don't think it's worth pushing it.  I may put the hardener straight into a syringe or another pot - not sure yet.

[Gina]

Hi Gina, are the 30x30mm tecs efficient enough for cooling the cold finger? I have 2 12703 & a 12706 both 40mm sguare, I looked on farnell's site for the 3 amp one but struggled to find it, have yo a link to it?

Ray

Yes, quite sufficient.  I'll look for the link to the Farnel ones.

[Gina]

I'm sorry but after an extensive search, I can't find the link to the Farnell Peltier TECs   I'll post if I come across it.

[Gina]

I have sucked up resin into a 20mL syringe and also taken a 2mL syringe with needle and poked that into the bag of hardener and sucked up 2mL of hardener.  I sealed up the bag again where the tiny hole is with Sellotape.  The resin was too viscous to suck up with a needle on the syringe even though it was quite a big needle.  I had to cut the needle off the syringe as it was stuck firmly on - that's why the tube is shorter than usual.

Two photos - 1.  syringes filled and 2. after cleaning off and piece of balse wood to seal the hardener needle and prevent a nasty accident.

Edited April 25, 2014 by Gina

[Gina]

There's a possibility that I may get the 3D printer working shortly - the replacement control board came this afternoon

[Gina]

Transferred most of the smaller pot of resin to a 60mL syringe and put the rest in the other pot.  So here is what I have now.  Hardener still in its bag to be accessed by hyperdermic needle, one plastic pot of resin, 55mL of resin in syringe, 20mL resin in syringe and 2mL of hardener in syringe with needle.  To use I plan to squirt out a 5:1 ratio by volume of resin and hardener, mix thoroughly and suck up with either a 2mL or 5mL syringe to apply to the sensor gold wires.  The latter will require a fair bit of practice I suspect

Now in view the arrival of the replacement control board I'm switching my attention to the 3D printer

Edited April 25, 2014 by Gina

[russellhq]

I'm sorry but after an extensive search, I can't find the link to the Farnell Peltier TECs   I'll post if I come across it.

This is the one I'm thinking of getting:

http://uk.farnell.com/jsp/search/productdetail.jsp?sku=1639752

It's 2A at 15.7V. dT 75C

The next one up is 3.9A at 15.7V. dT 75C: that might be too much power.