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Object of the Week, March 29, 2020 – NGC 3738 / Arp 234
Irregular / starburst galaxy
Ursa Major
RA: 11 35 47
DEC: +54 31 32
Magnitude: 12.04 (v)
Size: 2.5’ x 1.9’
Attachment 3823
Following the dictates of staying home to help slow the spread of COVID-19, I observed from my back yard last weekend. The weather was exceptionally nice and the night skies were pretty darn good too – better than I imagined in fact. Over two nights I was able to see six Arp peculiar galaxies through my suburban/rural skies with my 28-inch f/4 scope, and one in particular grabbed me, Arp 234 - aka NGC 3738. I liked it enough that I thought it would be a good OOTW while I was observing it, so here we go.
NASA has a nice summary of 3738 at https://www.nasa.gov/mission_pages/h...e/ngc3738.html so I won’t cover the same territory - I'll concentrate on how this irregular, starburst galaxy looked in the eyepiece. Located just outside the southern border of the Big Dipper’s bowl, a few degrees west of Phekda, 3738 is an easy star hop, and at magnitude 12.04 it’s bright enough to easily see in scopes much smaller than I was using.
It’s also a fairly good size at 2.5’ x 1.9’, so even under less than ideal skies, this galaxy should be within reach of most amateur telescopes. Here’s what I saw:
“This is cool – I can see the brightest knot at the western end of this smudgy galaxy. The faint star (mag 14.5) just off the western knot is visible with determined averted vision, as is an even fainter star to its north (mag 15). All this takes magnification well and looks best at 547x. 20.30 SQM.”
Attachment 3824 Attachment 3825
The galaxy looked nice at 253x and 408x as well, with the brightest knot becoming more distinct as the power increased. If the seeing had been steadier I’ll bet it would have looked even more detailed at 700x, and under a darker sky perhaps another star forming knot or two would have become visible.
As a bonus, following a short string of 10th and 11th magnitude stars a half degree to the south will bring you the magnitude 10.9 spiral galaxy NGC 3756, so pop down for a quick peak while you’re in the neighborhood.
And as always, give it a go and let us know!
(ps - my sketches were flipped so north is to the left - the HST image is north up.)
