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REALLY cold (<10°F) astroimaging questions

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#1 Phillip Creed

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Posted 23 January 2019 - 12:00 PM

If you're into astrophotography, do NOT ever, EVER move to NE Ohio.  Besides the semi-permanent lake-effect clouds in wintertime, there's also this issue--when you DO get a clear winter night here in NE Ohio, it's typically very, very cold.  It requires a strong arctic high pressure system to typically scour and dry out all layers of the atmosphere.  Our nighttime lows in winter are typically 15 - 20°F, but the typical CLEAR winter's night is often colder than that.

That being said...suppose it's clear and cold.  Let's say 10°F (-12°C) or colder.

First issue is the battery on the camera dying quickly.  Do you (a) bring along a spare battery, (b) failing that, keep the battery in your pocket until the very last minute when it's time to image?  Also, © if you elect to go with (b), will the relative warmth of the battery skew the temperature matching for the dark frames?

...which brings about the second question...

...do you need dark frames at these temperatures for a Canon T6?

Clear Skies,

Phil



#2 HMS_Endeavour

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Posted 23 January 2019 - 12:12 PM

dslr batteries do not like the cold.

yes to keeping then your pocket but you're going to struggle to keep your camera powered for long periods in such cold conditions (and faffing about with changing batteries over is going to make for a miserable experience)

 

do you have a battery grip on your camera? that may help a little by doubling your battery capacity



#3 StarBurger

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Posted 23 January 2019 - 12:41 PM

I avoid camera battery problems at any temp. by using a converter gadget that plugs into where the battery sits. Supply it from a 12 vdc battery.

As HMS says, no faffing around changing batteries and loosing tracking or guiding. Goes all night.

As for temperature skewing, my mentioned solution avoids this also.

It is a waste of time shooting darks IMO out on the scope.

I take darks either outside (if the daytime temp. is close to the temp when imaged) or in the fridge.

Just be aware that (I'm sorry if you already know this..) that the camera will easily run internal temps. of about 10 C higher than ambient, and it may take 3-5 frames before the temp. stabilizes. 

Either way, outside or the fridge I am happy to run MANY exposures and select and group for batches at approx the same temps to match the lights.

Again sorry if you know already but there is the free program IrFanview which among other things lets you see the EXIF data for Canons, particularly the shot temperature.

Heck knows why Canon cannot have that available in image info!

As for whether darks are needed for a T6 I would not know.

I guess probably it's a good thing if just to deal with hot pixels.


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#4 JukkaP

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Posted 23 January 2019 - 12:44 PM

We just had -27 celcius in Finland and I was imaging. But I have observatory and ac powered system.

In the field whit over -10 celcius I would invest on some sort of external power source for equipment.

You dslr temperature will still be relatively high. I had temperature probe behind my cold finger cooled sensor and it was over +0 celsius eaven when we had over -10 celsius ambient.

#5 gordtulloch

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Posted 23 January 2019 - 12:51 PM

Absolutely an AC adapter for your camera is a must - long exposure astroimaging is hard on the battery in any case never mind in extreme cold (it was -33C here on Sunday for the eclipse with a -45C windchill) - and yes you need darks no matter what, temperature isn't the only variable you're zeroing out when you apply darks (and flats!) to your images  



#6 PAdennis812

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Posted 23 January 2019 - 01:37 PM

Phil,

Hello.  Cold here as well.  I guess I'm old school in that I still use 2 batteries.  Generally I image from the backyard and so leave one battery plugged into its charger and swap out when I'm changing targets.  I would definitely keep a battery in a pocket rather than expose it to the cold.

 

During the Lunar Eclipse, Backyard EOS recorded my T6 at 12 degrees when the ambient temp was around 11 degrees.  My Canon battery lasted about 5 hours while a 3rd party one made it only 2 hours.  As everyone has suggested there are alternatives:

 

1.  If you have access to power or a laptop:

https://www.amazon.c... 77D 200D 8000D

 

2.  If not, you can extend usage with a battery grip:

https://www.amazon.c...ip for canon T6

 

I'm sure there's other ways as well.  I agree that Darks are necessary and building a library is the best approach.



#7 Kendahl

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Posted 23 January 2019 - 02:26 PM

I avoid camera battery problems at any temp. by using a converter gadget that plugs into where the battery sits. Supply it from a 12 vdc battery.

Where did you get a battery substitute that runs off 12 VDC? I haven't been able to find one. Neither could tech support at B&H Photo. I have one that runs off 120 VAC that I produce with an inverter. I would like to get rid of the inverter. For my computer, I have a 12 to 19 VDC converter from Targus.

 

At freezing point or below, a dark will consist almost entirely of bias with a negligible contribution from dark current. Just use a master bias frame instead of a dark.



#8 StarBurger

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Posted 23 January 2019 - 04:36 PM

OK Kendahl. I got the substitutes I think from Amazon but my two were for a T3i and an XS Canon. Different converter for each because of different voltages, amps and and battery formats. I had to be careful on selection because I found one that had a too long cable that caused enough cable loss that it did not like the switch-on power surge. 

So what you may need is a 12 vdc converter to something like (guessing! depending on camera) 7-8 vdc to supply the camera battery emulator.

If you let me know which camera you have I would be happy to research for you.

Expense? Nothing frightening- the primary 12 v converter was like $10 and the secondary about $15.

Let's just hope your camera has a battery substitute available.



#9 starblue

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Posted 24 January 2019 - 03:16 AM

Look into "TetherTools Case Relay Camera Power System Kit" at B&H. It lets you run a camera from a USB power pack, and also lets you hot-swap power packs during sequential shooting without interruption. The difference between the different kits is the dummy battery needed to match your brand's camera, so check that bit carefully. If you have several cameras that each take a different battery size, it's possible to buy the dummy batteries apart from the full kit, which includes the power pack.

 

My camera's brand (Panasonic) does make a dummy battery system that runs off AC power--doesn't Canon do the same? But a note of warning: at least in my case the dummy battery is *different* between Panasonic's vs. TetherTools'--the dummy battery itself is the same size (of course--it has to be to fit the camera) but the *plug connector* from the battery to the rest of the kit is a different size, so the AC vs. USB backends are not interchangeable. Maybe a Canon version doesn't do that.



#10 ChrisWhite

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Posted 24 January 2019 - 06:52 AM

It's not my equipment that keeps me from imaging at below 10....

I work outside all winter so get my fill of cold fingers. 10 is about my cutoff...

#11 lakeorion

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Posted 24 January 2019 - 08:39 PM

Other problems I have run into imaging in the cold:

 

Cables get stiff - this, without decent cable management can effect guiding as those normally flexible things turn into stiff pushers and pullers on mount.  In extreme situations they can get stiff enough to break the insulation - been there done that.

 

Grease gets stiff - below 0°F my mount will not slew at max speeds.

 

Focuser gets stiff - similar temps increase the resistance of the focuser beyond the ability of the motor clutch.  Motor moves, reports it moved but focuser doesn't and any form of autofocus routine freaks out because the stars never change.

 

And last but not least - frostbite.  Last time I was out (eclipse at -8°F) I spent too much time fiddling around with little metal knobs and DSLR buttons.  Thumb and forefinger suffered a little.

 

My goal is to not go out at less than 10°F, but I'm not far from you (SE Michigan) and know full well your situation about clear and cold.



#12 calypsob

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Posted 24 January 2019 - 09:05 PM

I would buy a 4 pack of batteries on amazon, keep them in your chest pocket. Or get a dc adapter and use a deepcycle battery


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