Saturday, July 21, 2007

20070721 DBK M7

Transparency is quite good tonight, so why not give a try on deep sky? DBK 21AF04 has smaller chip (1/4") than DMK 31AF03 (1/3") and so the field of view is more restricted, and also due to its bigger pixel size, the image scale is also smaller. Anyway, it's in color, more convenient for lazy people like me. I don't think that I can spend much time in DSOs with my current lifestyle, so fast food type is good to me.

The first attempt is by Fujinon 75mm f/1.8 wide open, 11.55s at 350 gain. Chromatic abberation can be seen easily, all the stars have blue halo. Since DBK has no UV-IR block, maybe it's out of focus UV and IR? 32 frames are obtained.

Second attempt is to close down it, to see if the problem can be reduced or not. I close the aperture stop by 2-clicks (i.e. f/4), gain is now 605, exposure is 16.36s. Chromatic abberation persists, more or less the same as before, so it's more like IR/UV issue. 10 frames acquired only, for it's more like an experiment:-

Third attempt is a Cosmicar 150mm f/3.2 wide open, 13.75s at 655 gain. I think I need to use an UV-IR cut for deep sky imaging.

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