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First light with ZWO ASI294MC: Navi and the Ghost of Cassiopeia (IC 63)

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#1 lucam

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Posted 11 September 2019 - 08:56 AM

Gamma Cassiopeiae or Navi is a blue-white, sub-giant, eruptive variable star with a magnitude that changes between +1.6 and +3.0 erratically. Both Navi and the reflection-emission nebula IC 63 are located at a distance of roughly 550 light years from us. The Ghost of Cassiopeia (IC 63) and its neighbor IC 59 are rich in hydrogen and glow red due to the intense ultraviolet radiation from Gamma Cass. The blue signal from the nebula is indicative of presence of cold interstellar dust, which reflects the strong light from Navi.

 

This image is a first light with the ZWO ASI294MC Pro for me. I have only used mono cameras so far and was curious to try an OSC camera. An opportunity arose to trade my KAF8300 camera and decided to give it a shot. The camera has impressive dynamic range and was able to tame Gamma Cass with no ugly sensor pattern and very little in terms of reflections. After sorting out incorrect dark masters, the data calibrated easily and was extremely clean. Only minimal noise reduction was applied, which surprised me given the relatively short integration time.  

 

Processing notes:

- Linear processing in PI: Data calibration and integration, Bayer drizzle integration, MLT denoise with internal mask, RepairedHSV separation, stretch with ArcSinhStretch followed by MaskedStretch

- Starnet++ to remove stars, minimal touch-up of starless image in Photoshop, create difference image (stars)

- Assemble starless and star image in Photoshop CC and adjust contrast/saturation for the the background nebula and Navi separately from the stars. 

 

Takahashi FSQ106EDX4

ZWO ASI294MC Pro (Temperature: -15C, Gain: 120, Offset: Default)

Skywatcher EQ6R Pro

IDAS LPS-P2 filter

 

566 60-second subs kept for 9.4 hours of total integration time. 

 

Comments and criticism are welcome. 

 

get.jpg?insecure

 

IC63_CN_v2.jpg


Edited by lucam, 11 September 2019 - 09:49 AM.

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#2 PeteM

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Posted 11 September 2019 - 09:11 AM

Holy smokes! You really did great with this tough area. That really does highlight the dynamic range of the camera. Processing 566 subs in PI must of taken a while, that is a ton of data. Congrats again.



#3 james7ca

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Posted 11 September 2019 - 09:18 AM

Yeah, that's a tough field and a subject that you don't see that often. I do wonder about the darkness of your skies. Upper state New York could be poor or moderately okay.



#4 lucam

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Posted 11 September 2019 - 09:23 AM

Holy smokes! You really did great with this tough area. That really does highlight the dynamic range of the camera. Processing 566 subs in PI must of taken a while, that is a ton of data. Congrats again.

Thanks, Pete. I feel a bit silly having wasted all this time trying to calibrate the data with dark frames shot with the wrong gain and offset. Live and learn. 

 

I wanted to keep the number of clipped pixels around Navi to a minimum and 1 minute subs swamped read noise abundantly even with the light pollution filter. The combination of low-noise and high-dynamic range of the camera provides a number of options for data collection optimization based on the target.

 

Bayer drizzle integration with 566 subs took a good part of a work day. I need to update my computer for post-processing to help with these datasets. It's definitely a big difference between CMOS and CCD data processing. 



#5 lucam

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Posted 11 September 2019 - 09:27 AM

Yeah, that's a tough field and a subject that you don't see that often. I do wonder about the darkness of your skies. Upper state New York could be poor or moderately okay.

I live in the Capital District, so my skies could be a lot better. Typically, on moonless nights I'll measure around 19.6 mag/arc-sec^2 at zenith (Bortle 5). North of my house, I look at less populated areas and the sky is decent. Targets in the sky to the South tend to fare much worse. Less then an hour away from my house I can find Bortle 3 skies easily, possibly Bortle 2 but I always image from my backyard because I have young kids and leaving the house at night gets too complicated. 



#6 lucam

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Posted 18 September 2019 - 12:31 AM

I was not totally happy with the amount of signal in the nebulosity and decided to try to add some Ha data to the original image. Using the ASI1600MM Pro and Astrodon 5nm Ha filter, I collected 5 hours of data, which I then used both to enhance the red channel of the RGB image and create of more detailed and  structured luminance. The final result is more vibrant, captures quite a bit more detail in the Ghost proper, and brings out the red nebulosity without losing the reflection component of the nebula.

 

get.jpg?insecure

 

IC63_CN_v3.jpg


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