NGC 3353 Observations?

[Alex Swartzinski]

Hello everyone,

I hope that galaxy season has been treating you well. Up at my 45N dark site, the nights are getting short and haze/smoke will be a concern soon. 

I enjoyed a (relatively) transparent night on Sunday though. One of the targets on my list was NGC 3353, a spiral in Ursa Major. I don't remember why it was on my list, but I'm glad that I took a look at it.

My notes:

NGC 3353- "Very nice galaxy. A very bright (almost stellar) round core is obvious in the 35mm finder. At higher powers (250-330x), a very faint suspected arm extends just beyond the core with averted vision on the western side. Averted vision also reveals a circular halo to the SE of the core. I'm not sure if this circular halo is an HII region or an imposed star, but it looks interesting."

This NGC catalog image looks pretty similar to my view, but the "arm" was significantly fainter for me:

My observation was made with a 15" f/4.5 dob under mid-6 NELM skies. The site is usually an observed Bortle 3. 

Has anyone else seen these features? I can 100% confidently say there is a circular halo of some sort on the NE side. I want to believe in the arm, but it wasn't on Steve's notes, so I don't have as much confidence 😀

[Scott Harrington]

On Wed, May 28, 2025 at 7:47 PM Alex Swartzinski <alex...@gmail.com> wrote:

Hello everyone,

I hope that galaxy season has been treating you well. Up at my 45N dark site, the nights are getting short and haze/smoke will be a concern soon. 

I enjoyed a (relatively) transparent night on Sunday though. One of the targets on my list was NGC 3353, a spiral in Ursa Major. I don't remember why it was on my list, but I'm glad that I took a look at it.

I hope you don't take this the wrong way, but if you check the NASA/IPAC website and search for NGC 3353, it comes back as a 'Blue Compact Dwarf/Irregular H II' galaxy. Then, by clicking on the "Classifications (26)" tab, you'll find that it's not been an easy one to place. In the venerable 1991 RC3, it's listed as a possible barred spiral - peculiar (sb? pec). The NASA/IPAC is one of the best sources for galaxy classifications and allows me easy access to what it was cataloged as in the RC3.

I observed NGC 3353 for the first time last May and again this February. In between those two times, I learned that the galaxy was cataloged as Haro 3 and then Markarian 35 . . . though I believe that the Mrk 35 designation actually belongs to the intense H II knot just northwest of the core.

My notes:

NGC 3353- "Very nice galaxy. A very bright (almost stellar) round core is obvious in the 35mm finder. At higher powers (250-330x), a very faint suspected arm extends just beyond the core with averted vision on the western side. Averted vision also reveals a circular halo to the SE of the core. I'm not sure if this circular halo is an HII region or an imposed star, but it looks interesting."

This NGC catalog image looks pretty similar to my view, but the "arm" was significantly fainter for me:

My observation was made with a 15" f/4.5 dob under mid-6 NELM skies. The site is usually an observed Bortle 3. 

Has anyone else seen these features? I can 100% confidently say there is a circular halo of some sort on the NE side. I want to believe in the arm, but it wasn't on Steve's notes, so I don't have as much confidence 😀

In May 2024, I found NGC 3353 to be visible at 68x in my 16-inch as a small, diffuse glow with a stellar center and a star to its south. At 440x, the galaxy appeared as an out-of-round glow that gradually got brighter towards the middle with a core that was possibly elongated. I was after the compact H II/SFR that was northwest of the core and failed to detect it. The night was May 14, and I saw an auroral display that was phenomenal from even 36N. It was washing out the sky.

In February 2025, I observed it with my 16-inch and at 440x, I got multiple sightings of a "star" on the northwest side of the core and still inside the galaxy's glow. I made a drawing which allowed me to compare to images and prove that I did indeed spot the H II/star-forming region (Mrk 35) even though it appeared stellar.

As for the features you saw, you mention a "circular halo to the SE of the core" and a "circular halo of some sort on the NE side." I never noticed that except that the galaxy appeared out-of-round in the NE-SW direction. You certainly viewed one of those galaxy's that is a bit of a visual enigma! A good report for such a tricky object.

PanSTARRS image of NGC 3353

Legacy Sky Survey Image:

Scott H.

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[Alex Swartzinski]

Thanks for the fast and detailed reply, Scott! 

Was the NW HII "star" completely stellar? Maybe I glimpsed the increased surface brightness (from this feature) inside of the faint halo and filled in an arm? In any case, I try not to let averted imagination affect my observing notes but I think it got me here. 

As you can tell, I have not done much homework on this galaxy, but I'm happy that it turned out to be a blue dwarf. I likely included it on my list because of this classification.

The circular feature is still a mystery. Maybe it was the core region extending further than I expected? I don't think it's a real feature based on the other observations I've found.  

What a miss on my end! My observations don't line up with the evidence, and I should have done more research.

I'll add this galaxy back onto my list to try again, but I'd be happy to hear other observations!

Thank you,

Alex 

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[Scott Harrington]

On Wed, May 28, 2025 at 8:57 PM Alex Swartzinski <alex...@gmail.com> wrote:

Thanks for the fast and detailed reply, Scott! 

Was the NW HII "star" completely stellar? Maybe I glimpsed the increased surface brightness (from this feature) inside of the faint halo and filled in an arm? In any case, I try not to let averted imagination affect my observing notes but I think it got me here.

Yes, it appeared stellar and was difficult to see unless you knew what to look for and were prepared to try and see the small, bright core with a fainter stellar knot just northwest. 

As you can tell, I have not done much homework on this galaxy, but I'm happy that it turned out to be a blue dwarf. I likely included it on my list because of this classification.

Probably so.

The circular feature is still a mystery. Maybe it was the core region extending further than I expected? I don't think it's a real feature based on the other observations I've found.  

What a miss on my end! My observations don't line up with the evidence, and I should have done more research.

I'll add this galaxy back onto my list to try again, but I'd be happy to hear other observations!

Yeah, this is one of those galaxies that I'd like to see in Keith Rivich's 25-inch to try and discern more detail. Like, I can't understand how the core can be so stellar but that only shows up on the HST image as a bright knot. What exactly is that? How much of the details in this 2004 paper (https://ui.adsabs.harvard.edu/abs/2004AJ....128..610J/abstract) am I seeing? Two observations under my belt and I'll need several more before I'll fully understand what I'm seeing. And this is just one of many galaxies in which that's the case!

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[Akarsh Simha]

I looked up and I don't happen to have any observations of this. My "Adventures in Deep Space AI Agent" (prototyping still :D) didn't find anything either.

Thanks for the object recommendation, it goes on the list.

[Steve Gottlieb]

My last observation of NGC 3353 (which is on ADS) was made with my 24” at the Golden State Star Party back in 2018.  I apparently didn’t do much, if any, research on this BCD, either before or after the observation, and I don’t recall looking for any feature.  But looking at my notes now at 375x...

"Moderately bright, fairly small, slightly elongated SW-NE, 0.6'x0.45', very small bright nucleus, occasionally a brighter spot was seen on the west side.”

…I’d assume the “brighter spot on the west side” most likely refers to region A (the brightest star-forming region).

I’m glad this object was brought up!

Steve

On May 28, 2025, at 4:13 PM, Scott Harrington <sn4...@gmail.com> wrote:

On Wed, May 28, 2025 at 8:57 PM Alex Swartzinski <alex...@gmail.com> wrote:

Thanks for the fast and detailed reply, Scott! 

Was the NW HII "star" completely stellar? Maybe I glimpsed the increased surface brightness (from this feature) inside of the faint halo and filled in an arm? In any case, I try not to let averted imagination affect my observing notes but I think it got me here.

Yes, it appeared stellar and was difficult to see unless you knew what to look for and were prepared to try and see the small, bright core with a fainter stellar knot just northwest. 

As you can tell, I have not done much homework on this galaxy, but I'm happy that it turned out to be a blue dwarf. I likely included it on my list because of this classification.

Probably so.

The circular feature is still a mystery. Maybe it was the core region extending further than I expected? I don't think it's a real feature based on the other observations I've found.  

What a miss on my end! My observations don't line up with the evidence, and I should have done more research.

I'll add this galaxy back onto my list to try again, but I'd be happy to hear other observations!

Yeah, this is one of those galaxies that I'd like to see in Keith Rivich's 25-inch to try and discern more detail. Like, I can't understand how the core can be so stellar but that only shows up on the HST image as a bright knot. What exactly is that? How much of the details in this 2004 paper (https://ui.adsabs.harvard.edu/abs/2004AJ....128..610J/abstract) am I seeing? Two observations under my belt and I'll need several more before I'll fully understand what I'm seeing. And this is just one of many galaxies in which that's the case!

Thank you,

Alex 

On Wed, May 28, 2025 at 9:27 PM Scott Harrington <sn4...@gmail.com> wrote:

On Wed, May 28, 2025 at 7:47 PM Alex Swartzinski <alex...@gmail.com> wrote:

Hello everyone,

I hope that galaxy season has been treating you well. Up at my 45N dark site, the nights are getting short and haze/smoke will be a concern soon. 

I enjoyed a (relatively) transparent night on Sunday though. One of the targets on my list was NGC 3353, a spiral in Ursa Major. I don't remember why it was on my list, but I'm glad that I took a look at it.

I hope you don't take this the wrong way, but if you check the NASA/IPAC website and search for NGC 3353, it comes back as a 'Blue Compact Dwarf/Irregular H II' galaxy. Then, by clicking on the "Classifications (26)" tab, you'll find that it's not been an easy one to place. In the venerable 1991 RC3, it's listed as a possible barred spiral - peculiar (sb? pec). The NASA/IPAC is one of the best sources for galaxy classifications and allows me easy access to what it was cataloged as in the RC3.

I observed NGC 3353 for the first time last May and again this February. In between those two times, I learned that the galaxy was cataloged as Haro 3 and then Markarian 35 . . . though I believe that the Mrk 35 designation actually belongs to the intense H II knot just northwest of the core.

My notes:

NGC 3353- "Very nice galaxy. A very bright (almost stellar) round core is obvious in the 35mm finder. At higher powers (250-330x), a very faint suspected arm extends just beyond the core with averted vision on the western side. Averted vision also reveals a circular halo to the SE of the core. I'm not sure if this circular halo is an HII region or an imposed star, but it looks interesting."

This NGC catalog image looks pretty similar to my view, but the "arm" was significantly fainter for me:

<image.png>

My observation was made with a 15" f/4.5 dob under mid-6 NELM skies. The site is usually an observed Bortle 3. 

Has anyone else seen these features? I can 100% confidently say there is a circular halo of some sort on the NE side. I want to believe in the arm, but it wasn't on Steve's notes, so I don't have as much confidence 😀

In May 2024, I found NGC 3353 to be visible at 68x in my 16-inch as a small, diffuse glow with a stellar center and a star to its south. At 440x, the galaxy appeared as an out-of-round glow that gradually got brighter towards the middle with a core that was possibly elongated. I was after the compact H II/SFR that was northwest of the core and failed to detect it. The night was May 14, and I saw an auroral display that was phenomenal from even 36N. It was washing out the sky.

In February 2025, I observed it with my 16-inch and at 440x, I got multiple sightings of a "star" on the northwest side of the core and still inside the galaxy's glow. I made a drawing which allowed me to compare to images and prove that I did indeed spot the H II/star-forming region (Mrk 35) even though it appeared stellar.

As for the features you saw, you mention a "circular halo to the SE of the core" and a "circular halo of some sort on the NE side." I never noticed that except that the galaxy appeared out-of-round in the NE-SW direction. You certainly viewed one of those galaxy's that is a bit of a visual enigma! A good report for such a tricky object.

PanSTARRS image of NGC 3353

Legacy Sky Survey Image:

<Screenshot 2025-05-28 8.25.35 PM.png>

Scott H.

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[Uwe Glahn]

For me, the HII region was even brighter than the longish nucleus and clearly nonstellar. Under very high magnification, NGC 3353 looks more like a "V". With the 27-inch, the fainter HII regions at the SW tip were at the limit.

sketch:27", 733x, NELM 7m0+, Seeing II-III

[Mel Bartels]

I looked last night at NGC 3353 in my 30F2.7. 

It's tiny at low power with faint IFN streaks.

At highest X (luckily seeing and scope supported it), it was V shaped with a couple of knots and an overall background glow.

Mel

[Alex Swartzinski]

Thanks for sharing, everyone!

Those large aperture sketches are incredible....

Clear skies,

Alex   

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