The QHY8L is a low cost, entry level, scientific camera equipped with an APS-C size color chip. It has a good sensitivity also in Ha emission line. It is cooled and it has been primarily designed for astronomical use. The resulted photos go deep, e.g. 21th magnitude celestial objects can be captured in only 3 hours exposures at f/5.3 and 130mm aperture.

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Wow, this is -10 °C cooler than the specification!

As usual, every image coming down from the camera must be calibrated. I do that in MaximDL by using flat field images made with Gerd Neumann's "Aurora flatfield panel", since it is also suitable for OSC CCD sensors. Flat fields remove artifacts caused by inhomogeneities of the CCD sensor, dust particles on both the sensor and the optics, and vignetting. A master flat field should be calibrated by subtracting a master Bias frame.

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The dark frames (download link) will completely remove the so called "amplifier glow" artifact in your QHY8L light frames. The "amplifier glow" is a small bright area at top-left edge of your light/dark images. The bias frames will remove the noise of the electronics.

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Process your QHY8L images strictly in the following way in MaximDL:

1. image acquisition with this OSC camera => RGBRAW

2. image calibration RGBRAW => RGBCAL (using dark, bias, flat frames)

3. color conversion (RGBCAL => RGB)

4. color split (RGB => R,G,B)

5. remove gradient (i.e. the light pollution) in R channel => Rclean

6. remove gradient in G channel => Gclean

7. remove gradient in B channel => Bclean

8. color combine (Rclean, Gclean, Bclean => RGBclean)

9. repeat from step (2) for all your images

10. align all images

11.  stack all images

12. ...

13. further steps

The 2D Fast Fourier Transformation (FFT) of the master BIAS averaged of 30 Bias gives information about the electronics. Periodical patterns indicate badly shielded electronics. A point in the middle of the image with perfect noise around it without any pattern is a very good sign.

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There some slight differences between the BIAS of both QHY8L cameras I have used so far.

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I calculated the read noise of my QHY8L according to the instructions in users.libero.it/mnico and I found it to be 10.96e-, assuming a system gain of 0.5e- /ADU as shown in oleg.milantiev.com and tienda.lunatico.es

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These are the gain and offset settings I use for the QHY8L.

Thanks for reading
Panagiotis Xipteras


DISCLAIMER: I have no affiliation with QHY or any other manufacturer for that matter so I don’t really care if you buy this stuff over another. I take my time with each piece of equipment because I am always on the hunt for perfect solutions.

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