Ngc 4389 / 4392

[mdstuart]

Good morning

I was out last night despite the half moon! My estimate is that I lose 0.5m with a half moon. What do you think?

I observed some galaxies in Leo and Cvn...My favourite of the night was the "pair" NGC 4389 / NGC 4392.

A lovely rich star field which I think enhances the view of galaxies as the contrast between dots and fuzz is amazing.

So NGC 4389 was the brightest, an oval shaped glow that I could almost hold with direct vision. A faint field star just to the south of the galaxy. I then hunted for NGC 4392. Much fainter but still relatively easy with averted vision. This one is near a field star with two faint companions. NGC 4392 is much further away than NGC 4389 based on its red shift of 7233km/s which I understand makes it about 300 million light years away.

NGC4389.jpg

So if that moon is up its still worth going out observing!

Mark from the UK

[Ivan Maly]

How much you lose with the moon should depend on the brightness that the sky has otherwise... 0.5 mag sounds like a pretty modest loss, but I've not attempted an estimate. I too like the contrast between stars and nebulosity. Here's what I have on this pair from last year, with a 12" SCT on a 21.68 mag/arcsec^2 night:

NGC 4389. Shares the low-power field with the small, round, and otherwise featureless NGC 4392, which is also a Herschel object. NGC 4389 has a bright, strongly elongated elliptical bar that transects the very faint and almost round halo. Next to it in the direction of NGC 4392 is a comparatively bright star. On the opposite side and closer to the galaxy, almost on the edge of the halo, are two very faint stars. On the side of the bar which is closer to the bright star, halfway out from the center, is a faint compact knot, which is slightly off the major axis of the bar in the direction of the bright star. There is almost no concentration in the central part of the bar. NGC 4392 forms a Corvus-like asterism with three equally bright stars. [41 and 327 Mly. On SDSSIII the faint compact knot corresponds to a segment of the bar that is delineated by two dust lanes which diverge toward the bright star, i.e. to the N.]

[mdstuart]

Thank you Ivan for your notes, reading them brings back memories of the view.

Love your blog. Sounds like your skies are better than mine which allow me to see mag 5.5 stars overhead but anything below an alt of 30 is tough.

Mark