Imaging Source DMK 21AF04.AS

Camera review for solar system imaging

Page 5 - Resume

The DMK 21AF04.AS is great value for money and a good performer for solar system imaging. Many top planetary imagers use the cam successfully, there's no bad surprise in the camera's behaviour.

Signal processing of the device is ok - I didn't experience any noticable systematic noise like banding patterns for high gain recordings unlike the camera I used before. Personally I consider the Sony ICX098 CCDs a good trade off between sensitivity and pixel size. Pixels are small enough to obtain small FOVs per pixel even with newtonian reflectors and 5x focal length enlargement and still offer a viable noise characteristic and good sensitivity considering pixel size.

One may ask the question if a higher analog to digital conversion depth than the camera offers can deliver better results. Basically a higher bit depth allows fewer frames to be stacked to reach the same effective bit depth as a result created with lower bit depth raw frames. Additionally a higher bit depth can lead to identical results with slightly underexposed frames compared to correct exposed frames with a lower depth - nice in low light situations and sessions where short exposure times are required to beat seeing. The number of frames required to obtain a certain signal to noise ratio enhancement is not related to the bit depth, though.
The DMK 21AF04.AS outputs 8 bits per pixel, I assume the internal A/D conversion is 10bit. Competitors cameras (e.g. Lumenera SKYnyx 2-0) offer 12bit output but usually use CCDs with larger pixels like the ICX424 instead.
To evaluate if a bit depth > 8 pixels is usefull at all with the ICX098 the full well capacity of the CCD in electrons and the read & dark noise of the system is required to determine the optimal A/D depth. Since both parameters are not available to me I can't comment on the potential usefulnes of more than 8bits with this CCD.
Last but not least one should consider that the mentioned competitors products cost more than two times the price of the DMK 21AF04.AS.

The camera comes with a good and practical software package which is not too common for other cameras of this segment. The long exposure capabilities of the cam are fine to make a start into deepsky photography but the missing active cooling and only 8 bit A/D conversion don't make it a specialist for this task. The DMK 21AF04.AS is currently quite unrivaled in the price segment, some potential rivals may show up soon. The camera is highly recommended to solar system imagers looking for a solid & well known performer who don't want to invest in the range of 1000€.

Oliver Pettenpaul - July 2007