Observation by David Davies: NGC 4236 (Caldwell 3)

Uploaded by

Paul Downing

Observer

David Davies

Observed

2023 Feb 26 - 00:00

Uploaded

2023 Apr 14 - 18:34

Objects

NGC4236

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Constellation

Draco

Field centre

RA: 12^h16^m
Dec: +69°28'
Position angle: +0°06'

Field size

0°40' × 0°30'

Equipment

250mm Ritchey-Chretien with 0,72 reducer at 1450mm focal length
QSI 683 camera with Astrodon filters
SW EQ8 mount

Exposure

80 x 120s Luminance, 15 x 300s RGB

Target name

NGC 4236

Title

NGC 4236 (Caldwell 3)

About this image

I last used my telescope at the end of February and this run of poor weather seems set to continue. The last object I observed was NGC 4236, Caldwell 3 in Draco. I had been reviewing which of the Caldwell objects I had observed and noticed no entry for C3. Searching through my data files I could see that I had observed it in 2014 with my 10" Newtonian but had gathered only a few 7-minute subs. Looking at these I could see that the galaxy was very faint and the images had recorded just a faint smudge. Clearly, I decided at the time to move on to a brighter target.

NGC 4236 is a famously difficult target to observe. It is a barred spiral galaxy with a large extent in the sky. Its length is more than 2/3 the Moon’s width, but it has a very low surface brightness, barely brighter than the background glow of the sky. The mean surface brightness is 24.3 mag/asec2; the outer arms are much fainter. Given that there are magnitude 9 and 10 stars nearby, which I did not want to overexpose, I elected to try and capture the galaxy with many short exposures. The image resulting from this exercise is attached. The clusters of faint background galaxies at the northern end of 4236 are worth inspecting.

Files associated with this observation

wk16_23_NGC4236_davies.jpg (3.1 MB)

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Philip Terry, Martina McGovern

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