Object of the Week, April 11, 2021 – Arp 294, NGC 3786 and 3788

Object of the Week, April 11, 2021 – Arp 294, NGC 3786 and 3788
Double Galaxies with Long Filaments in southern Ursa Major
RA: 11 39 42.4 Dec: +31 54 35
Size: 2.2 x 1.2’ and 1.7 x 0.6’ Mag: 13.2p and 13.5p

For this week, I decided to pick another Arp galaxy, actually a pair. Arp 294 is a pair of interacting spiral galaxies. I picked this object because of nice structure in both galaxies and would be nice to observe this one again under darker skies with a Zeiss eyepiece.

The pair sits about 135 million light years in Ursa Major and it appears that it is about to collide. I don’t see much perturbation in the SDSS image yet but can imagine what it will look like after the first pass.

My observing notes about 20 years ago are as follows:
A pair of nearly edge on galaxies with knots visible in both galaxies.
The bottom right galaxy, NGC 3786, is a 3:1 elongated patch with a much brighter nucleus that is slightly off center. Well defined edges. A knot is detected just SW of the core. PA = 90º and 1’ long.
NGC 3788 is a 4:1 elongated patch with a brighter 3:1 elongated core. Well defined edges. A knot is detected on the north end. PA = 0º and 1.5’ long. No filaments, which is off the north end, were detected.

Attachment 4288
DSS image

Attachment 4289
SDSS image

Attachment 4287
Eyepiece rendition with a 22” reflector at 377x

Sorry for the short OOTW as I have a lot of work (papers) going on and second year in a row falling on my birthday, so I put it off until now.

Anyhow, As always, give it a go and let us know.

Hi, here's my observation from 2/23/2017: ngc 3786 and ngc 3788 aka Arp 294 are galaxies in Ursa Major ; magnitudes : 13.2 and 13.5 ; ngc 3788 being more elongated and edge on while ngc 3786 more face on with a bright central core. The pair appear to touch . One of my favorite Arps!! A beautiful sight!! I used a 6mm Ethos at 264x with my 14.5 Starstructure Dob f/4.3Attachment 4290

Back in 2008, with a 20" at 416x: NGC-3786: "Dimmer than NGC-3788. Seen both as a hazy patch with 313x but separated with 416x." NGC-3788: "Seemed brighter than NGC-3786 and at right angles to it. Clarity varied with transparency."

Two observations in my database, most recently in 2018 from dark northern Germany. 14" SCT @ 168x / 29':

Both galaxies are visible.
The SSW galaxy (NGC3786) is slightly brighter than the NNE galaxy (NGC3788), elongated ENE to WSW and quite suddenly brighter in a core that is elongated in the same direction with a moderately bright nucleus that is just visible without AV. With AV the outer halo subtly brightens.
The NNE galaxy (NGC3788) is just a little fainter than the SSW galaxy (NGC3788), clearly elongated north to south, suddenly brighter in the middle in a core that is just south of the middle. With AV the nucleus is visible and the galaxy is more elongated.
The galaxy NGC3793 to the SW is not visible.

I rated it 7/10.

Earlier in 2011 under Dutch skies, 12" SCT @ 179x / 27':

Both galaxies are visible.
NGC3788 is elongated north to south with NGC3786 perpendicular to it on the SSW side. The galaxies are not bright but it is a nice view.
The northern galaxy (NGC3788) is elongated north to south and is brighter in the center in a core that is very elongated in the same direction.
The southern galaxy (NGC3786) is slightly shorter and also brighter in the center, using AV the nucleus is faintly visible.
Close to the SE is a mag. 10 star (HIP56900).

That time I rated it 6/10.

The northern spiral arm of NGC 3788 was obvious in my last 24" observation --

NGC 3788 contains a relatively large, bright elongated core. A small bright nucleus is embedded on the north side of the central core. A quite noticeable bright arc -- the outer curve of the northern spiral arm -- is at the northern end of the disc. The northern disc is relatively dark (due to a dust lane) just on the inside (south) of the arc, so the outer arm appears partially detached.

Quote:

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Originally Posted by Raul Leon

Hi, here's my observation from 2/23/2017: ngc 3786 and ngc 3788 aka Arp 294 are galaxies in Ursa Major ; magnitudes : 13.2 and 13.5 ; ngc 3788 being more elongated and edge on while ngc 3786 more face on with a bright central core. The pair appear to touch . One of my favorite Arps!! A beautiful sight!! I used a 6mm Ethos at 264x with my 14.5 Starstructure Dob f/4.3Attachment 4290

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Yes, they are a beautiful pair--one of my favorites like NGC4038/4039
But, you don't use a coma corrector at f/4.3? That's unusual.

Hi Don, yes I use a type 2 Parracor. Raul

You said 6mm Ethos at 264x,which would be right without the Paracorr.
That's why I made the comment. When I did the math, I was surprised.
A 6mm Ethos in your 14.5" is 304x with a Paracorr.
(14.5 x 4.3 x 25.4 x 1.15 )/6 = 304x
An acquaintance of mine had the same scope you do. It's a beautiful scope.

You’re right , I always forget to add the Parracor to the equation, I’ve always been better at Art than Math .

I found a sketch with similar details you already documented Alvin. Nice pair.

sketch: 27", 419x, NELM 6m0+, Seeing III
Attachment 4297
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