NGC 4236 – Barred Spiral Galaxy in the M81 Group

Image Title: NGC 4236 – Barred Spiral Galaxy in the M81 Group

Copyright: Dane Vetter

Date image was taken: May 01, 2025

Location: Jestetten - Germany

Data Acquisition Method: Personal Telescope Setup

Image Description and Details: NGC 4236 is an impressive barred spiral galaxy in the constellation Draco. It belongs to the M81 Group, one of the galaxy groups closest to our Local Group (which includes the Milky Way). NGC 4236 lies about 11 to 14 million light-years away from Earth. This galaxy is relatively large, with a diameter of around 100,000 light-years, making it comparable in size to the Milky Way. However, it is difficult to observe visually due to its low surface brightness, which means its light is spread out over a wide area, making it appear faint. NGC 4236 is seen almost edge-on from our perspective, so its spiral structure is not easily discernible with small telescopes. Nevertheless, deeper images reveal clear spiral arms and active star-forming regions, especially in the galaxy’s outer areas. This activity is visible thanks to H-alpha emissions, which highlight zones of ionized hydrogen where new stars are being born. A striking feature of NGC 4236 is its very weak central bulge. Instead, a prominent bar structure dominates the galaxy’s center—common in later-type spiral galaxies. The high amount of interstellar gas also suggests ongoing star formation. The galaxy was discovered in 1795 by William Herschel. Due to its faintness, it was long overlooked by amateur astronomers.

Image Details:
The image shown on the site is a color composite, created using:
- RGB data to capture the galaxy’s broad-spectrum appearance (429 x 300 Seconds (35hours and 45 Minutes)
- Monochrome H-alpha data to enhance the visibility of hydrogen emission regions, particularly in the star-forming outer zones (327 x 600 Seconds (54 hours 30 minuntes)

The integration of both data types allows for a detailed, color-rich representation with highlighted H-alpha regions appearing as reddish hues superimposed on the natural color structure.

Equipment Details: Mount: 2 x Skywatcher EQ8-R
Telescope: LZOS 152/1200 CNC LW II + TS CF-APO 155 mm f/8
Focal Length: 1240 mm + 1280 mm
Camera: ZWO ASI 6200 MC Pro + ZWO ASI 6200 MM Pro with Astronomik 6 nm H-alpha filter, both used in APS-C mode.

Name: Dane Vetter

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