Installing the ICX618ALA-E CCD on the DMK21
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Introduction
The ICX618ALA-E ccd is of a new generation of ccd's that uses the EX-View technique to increase its sensitivity. The first to use this ccd to modify a webcam was Torsten Edelmann, and he described his findings here and here. There are different variants of the ICX618 CCD's available, but probably the most interesting one is the black and white version, the ICX618ALA. The two other versions are the ICX618AKA, that makes use of a [CYGM filter], and the ICX618AQA, that makes use of a [bayer filter). An advantage of the ICX618ALA over these color variants is that you can be more flexible with the filters that you use, and the potential resolution is also a bit higher (the depends on the debayering algorithm used to create the final color image).
Current Issues
The modification doesn't work perfectly; Edit regarding the first issue: Moon imaging works just fine without the use of dark-frames ( Copernicus, Aristarchus and Mare Orientale). The mentioned issues below are minor in effect, and don't seem to affect the image quality in lunar and planetary imaging.
- Some black dead pixels can be seen as small vertical lines of 1-4 pixels in the left-most and right-most columns of the image (within a 30 pixels wide region). This might make the camera less suitable for imaging the moon, but to be honest, I don't think it should be a big problem; dark-frames can probably be used to correct the dead-pixels images. This has to be tested further. The cause is still unknown.
- Increasing amounts of what appears to be fixed noise is visible in 15, 7.5 and 3.75fps, making these framerates useless. Again the cause is unknown, but intensive testing is ongoing. Always use the 30fps capturing mode on this camera. This is no limitation however, you can still select any (faster or slower) shutter time that you want.
Here are some further links to some test images showing some of the black dead stripes at the edges of the frames. If you have any ideas why these errors are there - and perhaps how it could be fixed - let us know. The bleeding also seem to affect raw images at the center of the CCD, so everything is not working 100%. I do like to point out that I believe they have little effect on planetary images (especially when the planet moves about in the field of view!). For deepsky images I would not recommend the modification at the moment (test-images will follow in a couple of days), and for lunar images I'm still unsure because I haven't tested that yet.
Issues that are not related to the modification, and were also visible in the original DMK21 (also in the DMK31 and DMK41) camera's at the highest framerate. This artefact might have something to do with the readout timings of the camera. As far as we understand this problem, it doesn't seem te be noise-related.
- The 60 fps ghost edge artefacts still remains after the modification. More examples with the Basler scout scA640-120 camera can be found here (German). The Basler Scout has the same icx618ala ccd, so I probably could have known that it was not just running the icx098bl out of specifications, because the icx618ala in the Scout also shows it.
Is it worth it? Will it work on my camera?
For me, even with the issues mentioned above, it is definately worth it. Of course it would be great if the issues could be resolved, but the camera is operating very good at 30fps (at fast shutter times on planetary and lunar targets, and even short exposures of deepsky targets are possible).
But I really don't know if it will work on your DMK camera (or some other kind of webcam). If you perform this modification, YOU and ONLY YOU are responsible of the outcome. You will definitely void the warranty of your camera, and no-one knows what will happen to your camera in a couple of weeks or months from now. I doubt it, but it could stop working are show image artefacts. So think twice before performing a modification like this! Anyways, don't come crying to me if you destroyed your camera by performing the modification :)
Here is an image of Saturn I shot on the first night that I used my modified DMK21 camera. This is not a proper test image of course, but I believe this does show that the camera has certainly not become useless. Conditions were pretty good for the low altitude (just below 37 degrees above the horizon).
And another recording made on March 9
Settings used to record these images: 30fps, 1/30s shutter time, 63 brightness, 1023 gain (=max). For a better view of the sensitivity of this camera, please look here
Are there other camera's on the market that already use the ICX618 ccd?
Yes! As far as I know there are three companies out there that incorporated the ICX618 CCD in their products; Basler, Prosilica, and Point Grey. The Prosilica camera's don't appear to be very good for astronomy, but the Flea3 is definately very good, and seems to become the leading planetary astronomy program. These Flea3 has some interesting features like 120fps and 12 bit output. The Basler Ace might also be a good camera, but it does need some proper testing. The Scout should be able to produce output at 100fps in 12-bit. the Basler Scout camera suffers from rather severe Ghost edge artefacts, and does not seem to be very interesting.
Would you actually need 120fps? It depends on the target your are imaging, the imaging conditions, and your setup. If you like to make images of the ISS, then you definately want the highest attainable framerate (shutter speeds that you would use are MUCH shorter than 1/120s), but for dim planets like Saturn (and beyond) 30fps would probably be more than enough. Mars and Venus? I definitely think 120fps could be useful. Jupiter would probably also work with 120fps. If you know your equipment well, then you can probably figure out by yourself if the higher framerates are wanted.
And what about 10 or 12-bit output? I'm not too sure about this, but my general idea is that this is an overrated feature for imaging the planets in our solar system. Most of the time you will probably already loose A LOT of bits due to noise in the system, and then 12-bits would just give you 4 more bits of noise. With a mean stacking algorithm you can actually increase the effective number of bits per pixels even if you have an 8-bit camera to start with. But for bright enough planets or the moon - so you can get a high enough signal to noise ratio to start with - you might really benefit from the extra output bits. But then you might also ask yourself the question if it wouldn't be better to use a smaller shutter time to begin with, so you can try to freeze the seeing a bit more (it's no good having a huge dynamic range, but fuzzy pictures...). Either way, it will not hurt to have 10 or 12-bit output, so if your camera can shoot those images, you might benefit from it one time or another.
Where can I get the CCD ?
FRAMOS or EURECA are the only suppliers that I know of that have the CCD.
At the time of writing, the price was about 45 euro's for the ICX618ALA ccd (excluding shipping and taxes).
Pictures of the modification process, and some tests
DMK21 Mod - Results and Comparison
How about other modifications to the DMK21 camera's?
We are working on that... Well, thinking about that is a better description, because we don't have a lot of leads to follow at the moment. But if you have any technical ideas, just let us know.
List of todos (some more ambitious than others):
- Fix the 60-fps ghost edge issue.
- Reduce noise caused by EM-fields. EM-fields can be produced by the electronics inside the camera, and anywhere else in the measurement setup
- Use passive/active cooling to reduce thermal issues of the camera (the camera gets quite hot)
- Hack the firmware to retrieve 10 or even 12-bits output
- improve DC power supply (external power supply may be used)
- add an adaptor pcb to the ICX618ALA-E, to improve CCD exchangebility and to reduce possible noise pick-up of the (currently used) wires
