[APML] OT: First light of CM2-1 camera

it is only a megapixel camera but it is a very sensitive megapixel: roughly 90% Quantum Efficiency across the visible spectrum from a thinned, back-illuminated E2V (Marconi) thinned back illuminated sensor that features 13.5 x 13.5 micron pixels.

http://www.fli-cam.com/downloads/4710aibc.pdf

I did the initial testing using a 200mm f/4 Pentax medium format camera lens and my 3nm Custom Scientific Halpha filter.

Exposures were 20 minutes each and five in number. I didn't have a dark library and only had time to shoot three darks so that's all there is for the calibration.

The sensor has a really weird looking "fingerprint": a wide stripe across the top and the bottom but they completely calibrate out with darks. In the three back illuminated sensors I have used over the years they all have these oddities about them, so it wasn't any real concern.

I want to try this out on the 18" f/12.6 Cassegrain. The extra QE and larger pixels should be nice on that scope. But I may use it on the AP180EDT at f/9 before the 18". I just need to decide on which targets I want to pursue.

I used it on the camera lens system because it was easy to exchange cameras on the system which is currently set up and aligned. It worked well on that system even at 13.92 arc-sec/pixel, but it should really sing on the longer focal length of the '180 and or 18" f/12.6 Cassegrain.

http://www.narrowbandimaging.com/ngc7000_cm2_200mm_ha_5x20min_page.htm

Overall impressions are favorable.

One thing of note is that the uncalibrated frames definitely have a sensor "fingerprint" and must be
both dark-subtracted and flat fielded. By comparison the Kodak KAF sensors are so uniform that a
median filter will often suffice in lieu of a dark for a "quickie
processing" and many times flats aren't absolutely necessary to get
something that sort of looks OK. But with this sensor, which happens to be
an engineering grade sensor so that may explain part of the anomalies, real
calibration frames are necessary.

The camera is very sensitive. I didn't do a quantitative comparison yet. I
don't think using it on the 200mm camera lens and 3nm filter is the best
configuration for making comparisons so I am eager to try it on either the
AP180 or the 18" cassegrain. Then I can do a reasonable comparison with
prior results with the KAF3200 sensor and the KAF6303 sensor.

I have uploaded a flat field, a dark that is a median combine of only three
darks of 20 minutes each, and a single raw 20 minute image used for this
NGC7K/Pelican shot to:

www.narrowbandimaging.com/images/cm2_first_light.zip

additionally I have uploaded a characterization file set useful for
measuring gain and read noise to:

www.narrowbandimaging.com/images/cm2_char.zip

I measured 1.40 electrons/adu for the gain and 7.84 electrons read noise
at -17C (running in my house last week).

The only negative thing to report so far is that I could not reach quite as
cold of an operating temperature as I could with the CM10. I suspect the
Marconi chip dissipates more power but that is only a guess: I've not dug
into the specs yet. Last night with a 17C ambient I could not get it colder
than -24.5C so I backed off and ran it at -20C.

I think that by 10pm it easily would have reached -25C but I had already
taken a few images at -20C so I just stuck with that temp. Even with only
three darks used for my master dark, the images were amazingly quiet after
calibration. This is a really nice little camera, albeit of modest
resolution at 1megapixel. From what I have seen so far this is a real
winner.

I think the E2V42-40 would be simply dynamite in the IMG body. That is a 2K
x 2K back illuminated sensor using the same 13.5 x 13.5 micron pixel
technology with the roughly 92% QE across the visible spectrum. Now *that*
is a sensor that would be a lot of fun to use on the big cassegrain: big FOV
and very sensitive and with a decent image scale: 0.48 arc-sec/pixel
unbinned (2K x 2K) or when binned 2x2 , 0.96 arc-sec/pixel (1K x 1K)

Richard