NGC 4449 revisited

I first imaged NGC 4449 in 2010 as part of one of my first collaborations with Dr. David Martinez Delgado. You can see my image from then in a post on my old blog with information about the scientific work on the “stellar tidal stream around NGC 4449” by clicking here (I recommend taking a look to the close up view (0.202"/pixel) of image taken by 8.2 meter Subaru telescope (NAOJ) which resolves the stream into its constituent stars...).

NGC 4449 (Caldwell 21) is an irregular galaxy located in the constellation Canes Venatici, about 13 million light-years from us. This galaxy is similar in nature to the Large Magellanic Cloud (LMC) and has been studied intensively as one of the strongest galaxy-wide starbursts in the nearby Universe. It has a stellar tidal stream that can be detected in deep exposure images.

My 2010 image had very little accumulated exposure (2.8 hours) and this year I decided to re-image this galaxy to get a higher quality image.

The main differences of the image of this year 2024 with the previous one are:

- Improvement in acquisition technique (for example, at that time I did not do dithering...).

- Increased cumulative exposure (now it is 18 hours)

- Incorporation of Hydrogen alpha exposure

- And in processing... 14 years of evolution and improvement of PixInsight (as LocalNormalization, SpectrophotometricColorCalibration, GradientCorrection, MultiscaleMedianTransformation and many other processes and scripts).

The image (1.69"/pixel) is a LRHaGB composition and shows my attempt to balance galaxy detail and tidal stream visibility in one image.

The second image is an inverted version with a different processing to better show the stellar or tidal stream.

The image incorporates Hydrogen alpha data (from 6nm Astrodon filter) that was introduced in the galaxy according to the methodology described by Vicent Peris here. 

Click on the images for a full resolution version, or go to the Gallery section for complete exposure details.

Image processing: PixInsight.

Observatory automation and remote operation with Talon6.

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