Cooled Nikon D5500a Chills the Sensor for Clearer Star Photos
petapixel.com
petapixel.com
What this means is: almost every electronic sensor is affected by it's temperature- from expensive image sensors to cheap MEMS accelerometers and gyroscopes.
That is why many of digital sensors also report their temperature, although that is not their primary purpose- so that current temperature effects on the measured result can be calibrated out either in sensor's logic, or by host software.
I've never heard that before, but its awesome.
Though, it could probably be generalised to "every component is also a temperature sensor."
If you find yourself asking "I already know about this, why is this on the front page?" Take a moment, you've just answered your own question.
It's a little bit like an article saying "computer engineers use special software that could take human readable source code and convert it into executable binaries for faster execution". A layperson would have their minds blown, but it's a super-yawner for those in the industry.
While there's some truth to that, it's not about how cold you get it, it's about how consistent the temperature is, as for a given CCD noise will usually be the same at the same temperature. I take darks only about once a month or if I notice a new hot pixel on an output - I take them at a range of temperatures, so that depending on what the weather is like I can choose a temperature for light frames, and then just use my pre-cooked darks.
Out of interest, unless you live in a desert, how are you setting to -40 delta without the thing freezing?
As to "why is this here?" - Astrophotography is a great hobby that'd likely appeal to the HN crowd. Sitting out under the stars spending hours doing very fine polar alignment, only to get a few dozen exposures, while worrying about everything from dew to wind to beetles climbing your tripod legs, and then days in startools, DSS, and all the rest, seeing just how much information you can squeeze out of your often slightly blurry light frames.
I actually almost enjoy the DSP end of things more - there's something ineffably cool about starting with the same set of input images and getting radically different results depending on how you treat them. I mean - stick a drizzle filter on your image, do a wavelet sharpen, lift your jaw from the floor, as it seems like you've just done some CSI style "ENHANCE" shit. Here's an example of what you can start with, and end up with - I'm really not too good at this and only have limited kit, but it's still exciting. This is the dumbbell nebula, shot on a windy night with a full moon - I shouldn't have bothered almost, but the final is still decent considering the garbage input. http://imgur.com/a/tyZ4j
Anyway, ramble aside, the more folks who are aware of astrophotography the merrier. It's just too much fun.
Also great shot! I feel your pain with the wind, dew and bugs... but it's still an awesome hobby.
On a more related note, I find it interesting that the product page says there's a 4 year warranty on the camera body. I didn't see anything about the warranty on the mod itself.
I should have linked to the original Petapixel post on the bottom of that Gizmodo page. My bad.
I'd like to hear more about this.
My QHY8 (a dedicated astro CCD) for example has a poor/old design, where the CCD compartment is not air-tight. This allows humid air to get inside, which can then fog up the optical glass due to the peltier cooling the sensor down.
The fix is a small ring that screws into the port, and raises the temperature just enough to combat dew. You could also wrap a dew heater strap around the part of the optical train at that point for a similar effect.
Dew (and frost) are the astrophotographer's great, persistent enemy and not just on the CCD. You'll also have dew problems on the telescope itself. For example, my newtonian sometimes has dew problems on the secondary mirror, occasionally on the main mirror, and always on my guide scope.
Most people just create some DIY dew heater straps with nichrome wire... it's super simple and effective.
OTOH, I've never considered somewhat more performant (not to say extreme) cooling of CMOS in order to eliminate noise. I'm surrounded by CMOS and CCDs every day, in film cameras and telecines (both array and linear chips). I knew, and saw, that temperature can influence noise, but apart from staying within 'normal' operating range, I never considered it would eliminate more noise if significantly cooled down. Probably because I knew noise was inherent to the way those things work and not much could be done to eliminate it altogether. Interesting. I'll try to experiment with a bit more extreme cooling on my equipment to see what yield would come out of it. I'm not that concerned about dew, because equipment is in controlled environment (dry and +-2C deg. stable environment), but nice to know.
A major pain point of dew-heaters is if they are too strong, they induce "tube currents". E.g. the heat from the dew-heater causes the air around the heater to start convecting, which causes ripples in the final image. It's not really visible as ripples, but a general blurring of the image. It's essentially recreating astronomical seeing conditions inside the telescope itself, which is obviously not ideal :)
I think some fancier setups will be "active" and regulate themselves based on ambient temperature, but it's a lot more common for people to over-build their heaters and then use a dimmer switch. So you make your dew-heater for the worst winter night you expect, then dim it down for the rest of the year manually.
Thank god the CCD is small -- a Peltier unit, as a heat pump, is pretty inefficient, topping out a ~15%, at a low t delta. When you stack two on top of each other, the efficiency is now 2.25%, and this only gets worse as the delta increases or more units are added.
I shoot a lot of long distance photos (300mm F/2.8 and 600mm F/4 are my main lenses). Any vibration is greatly amplified when I shoot, and this is a much longer range than that.
I'd assume that the fan is simply turned off for the duration of a photo (plus the time it takes for vibrations to decay). The sensor won't heat up instantaneously.
Oh, and that's on 2032mm f/10.
For $1000+ I imagine the fans actually don't have much impact.
Edit: yes, that's how active systems work: gyro stuff and counteracting by moving the lens or the sensor¹. For astronomy rather a lens, because the sensor would have to move too far for the big shifts the tele causes².
¹ http://photo.stackexchange.com/questions/804/how-does-image-...
² https://photographylife.com/lens-stabilization-vs-in-camera-...
Such cameras (sold by Nikon [1]) are routinely used on high-end microscopes. They usually have a smaller resolution though - 1024x1024 is pretty common. There are a number of technologies used in scientific microscopy that work well for night-time photography, but most are just too expensive. Electron multiplying CCDs, chilled CMOS sensors, etc. They end up being one of the more expensive parts to a half-million dollar scope though.
[1] https://www.nikoninstruments.com/Products/Cameras/Camera-Hea...
Image stacking can reduce noise afterwards, but there's no substitute for collecting more photons to increase the signal in an image... and the only way to do that is to try and clean up the noise floor (via cooling, better sensors, etc) :)
Seems like some sort of liquid cooling system where the radiator/fan assembly was not mechanically coupled to the camera body (except by flexible plastic tubing) would be a better approach.
[1] For example, I have an antique 400mm focal-length lens that really is about 400mm long. With it attached to the tripod near the middle, and the camera at one end, there is a lot of potential for bouncing around.
Perhaps they use the fan to initially cool the sensor and then switch it off and let the Peltier cooling maintain the temperature or something?
1) If your setup is sophisticated enough that fan vibration may cause an issue, you're likely already using a german-equatorial mount and some kind of guiding correction (secondary guide scope, or off-axis guider). These adjust the scope's positioning in real-time to keep on-target. So that removes any large-scale deviation that may be caused.
2a) Small-scale deviation is generally not a problem, since most setups are likely to be limited by the resolution of your entire optical train. For example, my 800mm newtonian combined with a CCD with 7.2mm pixels means I have a resolution of ~2.01 arc-seconds. Assuming perfect guiding, my scope can tolerate any vibration as long as my target stays within ~2 arc-seconds. *
2b) In reality, most locations are limited by seeing conditions (e.g. how turbulent the air is), which averages 1-3 arc-seconds in non-mountain regions. Also the calibration of your mount (periodic errors, guiding errors, etc) are almost certainly a greater concern than the vibration added from the peltier.
That's from an amateur's perspective. Obviously high-end setups will start to worry about things like the fan's vibration, but for someone with a backyard setup (doubly so for someone using a consumer DSLR instead of dedicated CCD), there are bigger causes of inaccuracy :)
* This is a bit of a simplification, since things get a bit more complicated due to FWHM, wavelength, etc.
The main thing I contend with is backlash on my mount - imperceptible amount of play in the worms means I have to overbalance the scope significantly.
As I said elsewhere in this thread, distant quarrying (oh, and moles) cause far more shake than a good fan.
Speaking of... I need to finish that up soon before winter season starts in earnest!
They're typically fans with high quality bearings that also are spinning slowly. There's essentially zero vibrations coming out of that.
It's very hard to get decent results out of any optical stack, especially for photography, without having any sort of fans, heaters, coolers, and other air flow and temperature management devices in various places.
It's a high quality fan, and it's hard for a 5g fan to introduce vibrations in a 100kg+ mount+telescope setup.
(I just did that)
* first ever commercial
The technique isn't at all new, even in DSLR space.
Edit: Found one of them [3]
[1] https://get.google.com/u/0/albumarchive/11010321236096143315...
[2]https://plus.google.com/110103212360961433158
[3]https://plus.google.com/110103212360961433158/posts/58k5AgTx...
After a few hours of getting weird inconsistent results, I finally figured out to my shock and horror that the image was drifting and warping by upwards of 20 pixels after the camera had been one for a while (I think it was 640x480 resolution). My friend and I thought this was due to the CCD heating up and warping.
It looks like they're using the cooling for noise suppression but I bet the CCD also has the same effect I noticed of 'pixel drift/warp'.
This filter is removed in astrophotography cameras (you want all the light you can get) giving aprox. 50% more light gathering, but mostly in red/IR colors.
Maybe you are thinking about CMOS sensors, much more efficient, but even cmos sensors overheat in many cameras.
One of Ben Krasnow's videos comes to mind: https://www.youtube.com/watch?v=7PWESWqhD8s
http://www.suptech.com/pdf_publications/2004_superconducting...
Highlights:
"An advantage of superconductors is that their low-loss properties enable the fabrication of a variety of microwave components in a far more compact geometry than is practical using conventional materials. ... bulky cavity resonators and dielectric resonator structures can be replaced with compact microstrip designs fabricated on wafer substrates."
"The difficult requirements for successful growth of epitaxial YBCO films are the need for high substrate temperature (typically 700–800 C) and high oxygen ambient pressure. To simultaneously achieve these conditions during a thermal evaporation process, a unique heater concept was developed ... a rotating substrate platter that serves as a partial vacuum seal for a heated chamber held at elevated oxygen pressure. The platter fills the open end of the chamber, leaving only a very narrow (less than 0.5 mm) slit. This arrangement results in a pressure drop of three orders of magnitude between the oxygen-rich chamber and the rest of the vacuum system. Substrates spend the bulk of their time in the chamber, where they are heated and exposed to oxygen. As the platter rotates, the substrates exit the chamber and are exposed to the flux from evaporation sources for the three metallic constituents of YBCO. As long as oxygen is supplied to the deposited metal atoms within a few tenths of a second, they can form the correct phase of the material. Rotating the platter at a few hundred revolutions per minute accomplishes this in the system."
"...wireless customers expect (and require) long, maintenance-free lifetimes. Thus, one does not have the luxury of routine maintenance such as periodically evacuating dewars or recharging helium in coolers that might be acceptable in other application areas. The cryocooler and dewar, as well as all mechanical parts, must be designed to last for more than 40 000 h of operation, or approximately five years. ... Reducing the possibility of leakage requires that the dewar be permanently welded shut .. all feedthroughs must have leak rates of less than 1^10 cm /s He. This far exceeds the levels of hermeticity typically defined for the electronics industry and, thus, often requires custom solutions."
Page 8: photo of a 2002 high-temperature-semiconductor filter, including cryocooler and coolant dewar, showing that it's not that much bigger than a regular rackmount server!
"The practical benefits of HTS filter systems are regularly seen in field trials. Trials usually involve two weeks of network statistics, before and after installing a SuperFilter... Typically the base station receiver noise figure is lowered by 3 dB by the installation of the HTS filter system. ... Dropped calls were reduced from an average of 3.0% to 1.7% overall. The range observed was 18.7% to 63.6% reduction over all channels and sectors. The adjacent sectors, without SuperFilters, went from an average of 2.0% to 1.7% dropped call rate. Ineffective attempts went from 3.3% to 2.5%, a 26% average reduction."
Does this mean I'd get much better photos in winter than summer?
You could always crop down a full frame photo to get the same effect, but then you're just wasting pixels.