August 2021 TSS DSO Challenge

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August 2021 TSS DSO Challenge

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Post by kt4hx »


I will kick things off this month with some of my observing notes for the August targets. Hopefully my experiences will give you some sense of what to expect, depending upon your aperture, sky quality and experience of course. Good luck and let us hear of your successes. :)


Northern Celestial Hemisphere


Messier 29 / NGC 6913 (Cygnus, open cluster, mag=6.6, size=10.0’, class= III3p):
This observation was made from our typical suburban backyard eight years ago with the Zhumell Z10 dob. Conditions were Bortle 5 at that time.

"This cluster was easily picked up in the 8x50 RACI finder as a very small condensed pocket of stellar glow. Moving to the eyepiece (52x) it presented a loosely scattered group with a very prominent square of stars in the middle. I noted 8 prominent stars with many more dimmer ones in the field. I found it an obvious and well detached cluster, but not a spectacular object by any means."

NGC 6939 (Cepheus, open cluster, mag=7.8, size=10.0’, class= I1m):
This observation was made from our typical suburban backyard eight years ago with the Zhumell Z10 dob. Conditions were Bortle 5 at that time.

“I then headed to the Cygnus-Cepheus border to find my next two targets. Sighting in on 3rd magnitude Eta Cephei, I hopped about 2 degrees to the southwest to find the attractive magnitude 7.8 open cluster NGC 6939. I spotted about a dozen stars at 69x with a very noticeable haze of unresolved suns in the field. Using 89x and averted vision, the cluster revealed several fainter stars, but with a persistent haziness. At 114x I noted a somewhat L-shaped pattern of stars roughly pointing at 7th magnitude HD 196085 to the SSE. Even at 142x with averted vision, more stars were revealed, yet a fine haze of unresolved members continued to be present.”

NGC 6946 (Cygnus, barred spiral galaxy, mag=8.8, size=11.5’x9.8’, SBr=13.8):
This observation was made from our typical suburban backyard eight years ago with the Zhumell Z10 dob. Conditions were Bortle 5 at that time.

“Sweeping southeasterly through HD 196085, I found the face-on spiral galaxy NGC 6946. Though it straddles the Cepheus-Cygnus border, it is officially assigned to Cygnus. Glowing at apparent magnitude 8.8 with a dim surface brightness of 13,8, it was found at 69x as a dim, but noticeable rounded glow. It responded well to averted vision, with the core area brightening noticeably. Using 89x, the core appeared brighter without using averted vision, and it grew in size. At 114x to 142x, it became brighter and larger yet, but still remained somewhat dim, and diaphanous in appearance.”

To add some perspective to how this object responds with more aperture coupled with a darker location, the following observation was made two years ago at our dark site house (typically Bortle 3) using our 17.5 inch dob.

“I now turned to the IDSA chart 9-left to continue on with my journey. In locating the field for this galaxy, which was easy enough, I immediately noticed that the view in this direction and elevation was much cleaner, which bode well for the last part of my journey. Aiming the scope at mag 4.3 Eta Cephei, I slipped SSW 2° and the galaxy slid into view. It was large and diaphanous in appearance. I settled in with 110x to study it a few moments.

I have only observed this one from our moderately light polluted back yard with the 10 and 12 inch, where it was challenging as a very dim rounded patch of haze. In this case, with more aperture and significantly darker skies, it was wonderful. It presented as a large and bright oval that had a diffuse appearance. As I continued to observe its spiral structure began to take form to my eye. Not in a bold manner, but rather in a subtle sense. I could detect the delicate swirl of its arms arcing outward from a core that exhibited a very slight increase in brightness. Beautiful and subtle it was such a graceful object, like fine grain sugar spun into cotton candy.”



The following observations of the southern challenge objects were made five years ago from a location at about 5° south latitude. This area was near the ocean and thus was impacted by the marine layer air-mass which at times made observing difficult. For these observations I was using my Explore Scientific ED80 refractor on a photo tripod.


Southern Celestial Hemisphere


NGC 6584 (Telescopium, globular cluster, mag=7.9, size=6.6’, class=8:

"Moving back to Alpha Arae, I shifted my gaze eastward picking up mag 3.7 Theta Arae. I then looked to the northeast and picked up the three stars making up the outline for Telescopium as plotted in the IDSA – Epsilon (4.5), Alpha (3.5) and Zeta Telescopii (4.1). I moved about 1° southwest to mag 6.5 HD 168871 and then continued onward about 1.5° to a triangle of 6th and 7th magnitude stars pointing southeast. Following this triangle to the southeast for about 1° I easily found a pair of 7th magnitude stars. This globular is the apex of a southward pointing triangle with those two suns. Settling in at 27x I I quickly found a subtle but obvious little round glow where expected. Making the small jump to 34x it became more apparent yet still subtle. At 43x it was a little easier still and I even picked up what seemed to be a very slight uptick in central brightness. Using 54x and 71x, it continued to become a little brighter overall, and the impression of a subtly brighter core became more obvious."


NGC 6752 (Pavo, globular cluster, mag=5.3, size=29.0’, class=6):

“As my session was getting close to wrapping up I had a couple more things I was hoping to put in the bag. So I moved into yet another new constellation for me, Pavo the peacock. Directing my attention to Delta Arae further south I then looked to the east and picked up the zig-zag pattern of the western part of Pavo from Eta, to Pi, to Xi and finally to Lambda Pavonis. Using the Rigel Quikfinder to aim the 80mm at Lambda, I moved to the eyepiece (27x) and swept northeast slowly. Affter about 3° I effectively tripped over a very bright round glow of light with an 8.3 mag star pinned just to its south. At 27x it was a very bright and condensed large ball, and I was amazed at the intensity of the core. Using 34x it only got more impressive. The core became strongly apparent inside of a dimmer more diffuse halo. I went ahead up to 54x and I was now picking up more of the dimmer extended halo and the core became strongly condensed – a beautiful sight even in the 80mm. Now using 71x it was stunningly bright, but I also got a sense of the condensed core being slightly elongated, though this may have been nothing more than some slight variation in brightness across its face. At 102x it was very bright and the core seemed to have a tiny bright knot in it, which quite likely was a foreground 7th and 9th mag pair lying just southwest of its center I was also picking up a few little diamonds here in there around the cluster, so some very modest resolution was achieved. This one was very nice even in the 80mm at about 14° above the flat horizon.”


NGC 6744 (Pavo, barred spiral galaxy, mag=8.5, size=20.1’x12.9’, SBr=14.3):

“Feeling a bit adventurous after the wonderful show the previous object put on for me, so I decided to push the limits. Sliding due south from NGC 6752 for almost 4° to a slightly curved east-west line of three stars I had arrived at my intended field. This line of stars has two to the west, with a 48’ gap over to the star at the eastern end. In this gap is where this elusive, yet amazing galaxy resides. Focusing my attention between the two stars, using magnifications of 27x up to 71x, I got a definite, though fleeting, glimpse of a very subtle bit of light, sort of like a dim bloated star while the nearby stars remained focused. This would be the brighter core of the galaxy. Around that, I had a fleeting sense of a very subtle haziness, but it was very tough to be certain about that part. I know I saw the core looking into the darker portion of the sky out over the ocean, but not 100% sure I caught the dim outer structure. The transparency was a bit iffy since the object’s elevation was under 14° above the horizon.”
Alan

Scopes: Astro Sky 17.5 f/4.5 Dob || Apertura AD12 f/5 Dob || Zhumell Z10 f/4.9 Dob ||
ES AR127 f/6.5 || ES ED80 f/6 || Apertura 6" f/5 Newtonian
Mounts: ES Twilight-II and Twilight-I
EPs: AT 82° 28mm UWA || TV Ethos 100° 21mm and 13mm || Vixen LVW 65° 22mm ||
ES 82° 18mm || Pentax XW 70° 10mm, 7mm and 5mm || barlows
Filters (2 inch): DGM NPB || Orion Ultra Block, O-III and Sky Glow || Baader HaB
Primary Field Atlases: Uranometria All-Sky Edition and Interstellarum Deep Sky Atlas
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"Astronomers, we look into the past to see our future." (me)
"Seeing is in some respect an art, which must be learnt." (William Herschel)
"What we know is a drop, what we don't know is an ocean." (Sir Isaac Newton)
"No good deed goes unpunished." (various)
Some people without brains do an awful lot of talking, don't you think?” (Scarecrow, The Wonderful Wizard of Oz)
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Graeme1858 Great Britain
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Re: August 2021 TSS DSO Challenge

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Post by Graeme1858 »


Great report as always Alan!

Interesting that you can see M29 under Bortle 5 with an 8x10 RACI. I failed to identify it with my 10x50 bins! Either the jet stream was above me, I wasn't looking where I thought I was or my bins need replacing!

Regards

Graeme
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Re: August 2021 TSS DSO Challenge

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Post by kt4hx »


Graeme1858 wrote: Sun Aug 08, 2021 7:23 am Great report as always Alan!

Interesting that you can see M29 under Bortle 5 with an 8x10 RACI. I failed to identify it with my 10x50 bins! Either the jet stream was above me, I wasn't looking where I thought I was or my bins need replacing!

Regards

Graeme
Thank you Graeme. Messier 29 is bright enough (mag 6.6) and large enough (10.0') in angular size that you should easily be able to see in 10x50 bins. Of course, it would only appear as a small condensed glow, but definitely should be within reach if you are a typical Bortle 5. That said, the Bortle Scale is a sliding model, and varies as conditions change. I have seen our dark site range from B2 to about B6 in one evening as conditions shifted. Under average conditions it is a B3.

Our home backyard when that M29 observation occurred was a solid B5 under normal conditions. However, in the subsequent years things have worsened and I see it as a solid B6 now, sadly.
Alan

Scopes: Astro Sky 17.5 f/4.5 Dob || Apertura AD12 f/5 Dob || Zhumell Z10 f/4.9 Dob ||
ES AR127 f/6.5 || ES ED80 f/6 || Apertura 6" f/5 Newtonian
Mounts: ES Twilight-II and Twilight-I
EPs: AT 82° 28mm UWA || TV Ethos 100° 21mm and 13mm || Vixen LVW 65° 22mm ||
ES 82° 18mm || Pentax XW 70° 10mm, 7mm and 5mm || barlows
Filters (2 inch): DGM NPB || Orion Ultra Block, O-III and Sky Glow || Baader HaB
Primary Field Atlases: Uranometria All-Sky Edition and Interstellarum Deep Sky Atlas
---------------------------------------------------------------------------
"Astronomers, we look into the past to see our future." (me)
"Seeing is in some respect an art, which must be learnt." (William Herschel)
"What we know is a drop, what we don't know is an ocean." (Sir Isaac Newton)
"No good deed goes unpunished." (various)
Some people without brains do an awful lot of talking, don't you think?” (Scarecrow, The Wonderful Wizard of Oz)
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