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Cosmic Challenge: Abell 70

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#1 PhilH

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Posted 01 September 2023 - 05:06 AM

Of the more than 80 planetaries listed by George Abell in his 1966 paper "Properties of Some Old Planetary Nebulae," Abell 70 (also known as PK38.1-25.4) is one of the most unique. Actually, the planetary itself is a stereotypical example of a ring nebula, like M57, with a round shell of gas expanding away from the dim progenitor star. But look carefully and there is clearly more here than just that.

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#2 Alex Swartzinski

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Posted 01 September 2023 - 02:25 PM

Thanks for this challenge, Phil! 

 

I plan to attempt this pair with my 15" under magnitude 6+ skies. I don't have an OII filter (yet) so it will be interesting to see how much detail I can pull. 

 

For the galaxy, it will be tricky, but hopefully I can get a good smoke-free night like we've had this week. Too bad the moon is so bright! 


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#3 Herchel

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Posted 02 September 2023 - 08:02 AM

Oohhh another awesome one , thanks phil


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#4 Starman1

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Posted 02 September 2023 - 09:59 AM

I've seen this one a few times in the 12.5" in skies of m.21.3-21.5.

The important thing is excellent transparency of the air and a good O-III dual line filter.

Once the planetary is observed, remove the filter to see the galaxy at the edge.  In 12.5', it resembles a brighter knot on the ring.

I can't say I saw much extension to the galaxy, though the galaxy does extend beyond the core slightly.

A 16" can obviously see more:

https://univerzumkep...-nebula-aquila/

so I'm looking forward to my 16" that is coming.

 

Important:

--Aquila on the meridian

--no moon in the sky

--fully dark adapted eyes

--excellent transparency.

 

Here is a sketch on a much better night from the same observer and scope:

https://univerzumkep...ebula-aquila-2/

So transparency is critical on this one.


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#5 Astro-Master

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Posted 03 September 2023 - 11:30 AM

I remember seeing Abell 70 about 15 years ago in my 18" Dob from LBV in the Anza Borrego Desert before I got the mirror recoated.  I don't remember what power I used but I remember the OIII filter helped.

 

I think it's time for a revisit with new coatings on the mirror and my Ethos eyepieces, thanks for the reminder Phil.


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#6 John O'Hara

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Posted 04 September 2023 - 10:37 AM

I'm making it a point to try this one with my 12.5" Dob. at Cherry Springs State Park, PA this dark moon cycle.  Thanks again, Phil, for these posts and your fine book.  It's nice to see there are still those of us who do visual observation of the deep-sky.  I love the images produced by our imaging brethren, but for me, it will always be visual.


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#7 Epick Crom

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Posted 06 September 2023 - 05:39 AM

Hi Phil and thanks for another awesome Cosmic Challenge!

I shall give Abell 70 and it's galactic companion a go with my incoming 14 inch from bortle 1 skies. Thanks for your monthly challenges, I eagerly await them every month!
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#8 Epick Crom

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Posted 06 September 2023 - 05:39 AM

Hi Phil and thanks for another awesome Cosmic Challenge!

I shall give Abell 70 and it's galactic companion a go with my incoming 14 inch from bortle 1 skies. Thanks for your monthly challenges, I eagerly await them every month!
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#9 Alex Swartzinski

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Posted 15 September 2023 - 09:56 AM

Under good transparency, I completed this challenge last night.  

 

Using a 15" f/4.5, I was able to make out the ring shape of Abell 70. I used a UHC filter for the initial detection at 73x. This observation was quite tricky, but averted vision made the planetary more obvious.

 

Without the UHC, I noticed a very subtle brightening to the northwest. If I didn't know to look for it, I wouldn't have seen it! I'm fairly confident that I saw the core of the galaxy, but I didn't notice any extension. 250x make the detection of this uneven surface brightness more apparent. 

 

This was a tough but fun one! an OII filter is high on my priority list. 


Edited by Alex Swartzinski, 15 September 2023 - 09:58 AM.

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#10 Starman1

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Posted 15 September 2023 - 10:04 AM

Under good transparency, I completed this challenge last night.  

 

Using a 15" f/4.5, I was able to make out the ring shape of Abell 70. I used a UHC filter for the initial detection at 73x. This observation was quite tricky, but averted vision made the planetary more obvious.

 

Without the UHC, I noticed a very subtle brightening to the northwest. If I didn't know to look for it, I wouldn't have seen it! I'm fairly confident that I saw the core of the galaxy, but I didn't notice any extension. 250x make the detection of this uneven surface brightness more apparent. 

 

This was a tough but fun one! an OII filter is high on my priority list. 

I observed this earlier this week in the 12.5".  It was more visible with no filter than it was with the O-III or narrowband.

That surprised me.  I didn't try a broadband filter, but that could have been the optimum.

The best view was at 166x and 205x, for me.  


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#11 Alex Swartzinski

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Posted 15 September 2023 - 10:26 AM

I observed this earlier this week in the 12.5".  It was more visible with no filter than it was with the O-III or narrowband.

That surprised me.  I didn't try a broadband filter, but that could have been the optimum.

The best view was at 166x and 205x, for me.  

That's surprising! It's good to hear that my unfiltered observations were similar to your experience, and I wasn't too compromised by lacking the OII. 

 

My best views were 150x and 250x. I figured higher power would help bring the planetary out, but 330x was a little too much.  


Edited by Alex Swartzinski, 15 September 2023 - 10:27 AM.

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#12 Redbetter

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Posted 18 September 2023 - 02:48 AM

Note:  I believe the PK designation provided is a little off and has been slightly muddled/combined with the PN G designation.  It should be PK 38-25.1 while the more up-to-date catalog would be PN G 38.1-25.4 (or PN G038.1-25.4)

 

I observed this one on 9/12/23 with the 20".  The sky was running bright at ~21.0 mpsas.  The PN and galaxy were found unfiltered right away at 227x.  At 278 and 357x I observed the galaxy as "xF, ave SB, ~4:1 WNW/ESE elongated on N portion of nebula, w//xxF stellar core."  Switching to an OIII filter at 227 and 278x the annular structure was only weakly apparent, while the galaxy was greatly dimmed. 

 

Overall, the nebula was of more modest surface brightness than I expected.  The PN has a mean surface brightness in the ~22.5 mpsas range from what I can tell, essentially an average galaxy surface brightness.

 

I expected the annular structure to be more apparent, particularly when filtered, but it seems that much of what is seen of the brightest outer ring in images is redder emissions that the scotopic adapted eye does not pick up well, and the red emissions are lost with the OIII filter anyway.  


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#13 columbidae

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Posted 18 September 2023 - 08:31 PM

I observed this last night at the dark site, with (at least for an hour at the beginning of the night) above-average transparency, in a 12" so consider me a legitimate challenger (or just challenged). 

 

From the log: "Ghastly!  The faintest circle using averted vision at 190x, v. difficult.  Filters only help a little since already so dim." (UHC and OIII)

 

The filters did help, though each about the same amount I think.  With them, the PNe becomes a more well defined circle that is easier to obtain (but not really hold) using averted vision.  You gain a tad bit better contrast, but there really isn't a whole lot of photons to spare.  Without the filters, it was a very tough and intermittent circular-ish light patch.  I don't know if the less clean shape was because of the background galaxy or the sheer difficulty of observing it at all.  In neither case was there any visible structure - just an evenly dim patch.


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#14 Digital Don

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Posted 25 September 2023 - 10:57 PM

Living less than 50 miles from Chicago, I wouldn't even attempt to find this object visually.  However, using my MallinCam I was able to observe both Abell 70 and PGC 187663 from my backyard observatory.

 

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#15 Starman1

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Posted 26 September 2023 - 09:02 AM

Living less than 50 miles from Chicago, I wouldn't even attempt to find this object visually.  However, using my MallinCam I was able to observe both Abell 70 and PGC 187663 from my backyard observatory.

Your pic would make a nice finder chart for the planetary.




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