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| ZWO ASI1600mm Pro Camera with EFW 8-position Filter Wheel |
It's been about 2 years since I purchased my QHY10 OSC (One Shot Color) camera and I've taken a number of nice astrophotos with it, both at the prime focus of my EdgeHD as well as on the Hyperstar wide field lens. But the "real-deal" in astrophotography is though the use of mono (black and white) cameras. In the OSC case, the image is taken in color, much like a normal digital camera. In this scenario, the light must pass a filter in the camera known as a Bayer Matrix, which consists of alternating red, green (2x as many as red and blue) and blue filter elements. A given sensor therefore contains 25% red sensitive pixels, 50% green pixels and 25% blue. So the light from a object in space is split into these groupings. What this means is that a predominately red object is only captured by 25% of the pixels on the sensor (and lots of deep space objects tend to be in the red end of the spectrum). Much of the sensor is wasted and the sensitivity is greatly reduced.
A mono camera captures all the light all the time. That means it is much more sensitive and captures a lot more data in any given exposure. But if its mono, how do you get a color photo?
Astrophotographers use a set of colored filters to achieve a final image. Four separate exposures are necessary to create a single color photo - one through a red filter, one through a green, one through a blue and finally one through a clear, or luminance, filter. These are then combined later in software post processing to produce a color image. So the time on the telescope is quadrupled when imaging with a mono camera, but the results are of greater quality and capture much more detail in the dim regions of an object.
So I've been spending some time testing and getting the software set up to handle the new camera while the skies are cloudy. The photo shows the ASI1600mm Pro being tested with it's filter wheel attached. Much to do as I hope to test it out on real space objects in the coming days.
Star tracking will be a challenge.
ReplyDeleteYes and no. The ASI1600 has a CMOS sensor vs a CCD sensor. It is more sensitive and has user adjustable gain. Imaging thru the luminance and RGB filters should only take 30sec to 3 minutes; the Narrow Band filters up to 4-5 minutes, but if I adjust the gain a bit I can get them down under 3 minutes in some cases. So yes, at the longer focal length of the EdgeHD 3+ minutes is a problem with my current mount - wide field (and the GT102 refractor not a problem).
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