NGC 4725, 4747, and 4712

NGC 4725 is another galaxy discovered by William Herschel, in 1785. It is an intermediate barred spiral galaxy approximately 40 million light years from earth. Interestingly it appears to have only a single spiral arm that wraps around the galaxy. It is interacting with NGC 4747, which is a highly disturbed spiral galaxy near NGC 4725. It was also discovered by William Herschel around the same time as NGC 4725.

The interacting pair have been the subject of radio telescope studies, detailed here and here. These studies have concluded that these galaxies are indeed a tidally interacting pair, with a stream of neutral hydrogen connecting the two galaxies. It is further theorized that NGC 4725 is more disturbed than appears visually from our perspective, with significant asymmetries appearing in velocity and likely in the angular orientation of the spiral arms.

Also in the image is NGC 4712. NGC 4712 is approximately 224 million light years from earth based on redshift measurements, and therefore is much too distant to be an interacting galaxy with the previously mention 4725/4747 pair.

NGC 4712

For processing this image was drizzled at 2x, and then I used a workflow consisting of Graxpert, Blur-X, Noise-X, and Star-X. On the starless image I stuck almost exclusively with the multi-scale tools, adaptive stretch and median transformation. A touch of curves, and then I added the stars back in. This is a relatively recent change to my workflow, but overall it’s quicker and I think ultimately yields better results.

Technical Card

Mount: Celestron AVX

Camera(s): ZWO ASI 2600mc pro, ZWO ASI 220 mini guide camera on an OAG

OTA: Celestron C8 SCT with 6.3 reducer

Filters: None

Exposure: 152 Lights @ 180 seconds

Annotated image:

There are a few smaller galaxies in the background, but for this image the three NGC objects were the main event.