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  #41  
Old 10-09-2014, 06:03 PM
rrussell1962
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The thread seems to have deviated from DSO objects a bit. But one object (event) I won't forget is the transit of Venus. Lucky to have seen two and I know I will never see another, so certainly not repeatable for me. With a bit more planning I could have done better than a projection with the Astroscan though.
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  #42  
Old 12-09-2014, 07:57 AM
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mental4astro (Alexander)
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Hmmm, why just limit it to DSO's really - sorry Sab for your original intentions...

I've got a trio for you. On the Moon! Three craters - Armstrong, Aldrin & Collins. Challenge here is getting the lunar phase right and atmospheric conditions stable enough, particularly with Collins as its diameter is around 3km. Sounds big, and I guess a 3km hole is blooming big, but not so easy to see a 3km hole on the Moon from Earth...

The good thing about this trio is a really big aperture is not necessary. 5" should be enough - just. I've seen this trio only twice, the second time I only had fleeting glimpses of Collins & Aldrin. The other was barely any better. Spy out Collins and you are also very close to the Apollo 11 landing site.
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  #43  
Old 12-09-2014, 07:30 PM
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Originally Posted by GrampianStars View Post
Aha! that explains it thought my scope needed throwing out.
haven,t seen the shape either.
& I have a very dark site....

Next November "Snake Valey" party a group effort may be in order
Hi Rob,

The WSAAG crew at Linden Observatory in the Blue Mountains tried one evening / morning in December 2013 to nab IC434 (the Horse) using the Evans 30" dob (0.75m aperture).

It was not visible, despite no moon and a pretty dark site, and we tried for two hours. People had seen the Horse about ten years before at the same site, but the light pollution from Sydney has only gotten worse since then.

The consensus was that it is a doable target if the skies are dark enough. Otherwise, it is not a visual target.

Regards,
Tony Barry
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  #44  
Old 13-09-2014, 08:17 AM
Tropo-Bob (Bob)
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Messier 82 for me. It limps briefly to only 3 degrees above the horizon during the wet season. I saw the nearby M81 on first attempt, but it took me several more attempts and over 2years to find M82, in my 8inch Newtonian. That was in 1985 and I still rate it as my most difficult find with the equipment that I had.

And that ticked off my veiwing of the entire Messier collection (all 110) from the Cairns region.

Last edited by Tropo-Bob; 13-09-2014 at 09:32 AM.
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  #45  
Old 14-09-2014, 12:15 AM
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I nominate Sirius B. Anyone who's seen Alpha CMa B has my respect. At 10 magnitudes fainter than Alpha CMa A and only 10" apart this is a tough one to bag.

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  #46  
Old 14-09-2014, 03:36 PM
clive milne
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A solar prominence, naked eye. (During a total solar eclipse)
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  #47  
Old 14-09-2014, 05:04 PM
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I nominate Sirius B. Anyone who's seen Alpha CMa B has my respect. At 10 magnitudes fainter than Alpha CMa A and only 10" apart this is a tough one to bag.

Cheers
Steffen.
I didn't know this was a hard target, I'm not really into double stars. But Sirius B is always there when I look for it in my 12".
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  #48  
Old 14-09-2014, 10:30 PM
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Quote:
Originally Posted by mental4astro View Post
Hmmm, why just limit it to DSO's really - sorry Sab for your original intentions...

I've got a trio for you. On the Moon! Three craters - Armstrong, Aldrin & Collins. Challenge here is getting the lunar phase right and atmospheric conditions stable enough, particularly with Collins as its diameter is around 3km. Sounds big, and I guess a 3km hole is blooming big, but not so easy to see a 3km hole on the Moon from Earth...

The good thing about this trio is a really big aperture is not necessary. 5" should be enough - just. I've seen this trio only twice, the second time I only had fleeting glimpses of Collins & Aldrin. The other was barely any better. Spy out Collins and you are also very close to the Apollo 11 landing site.

lol didn't even know this thread was mine until I saw my nick under the title! I never specified DSO's though... so anything goes here

My most obscure solar system objects which I observed are the Uranian moons Titania and Oberon in the 8". More difficult than Triton. Triton is actually brighter (m 13.5) than both Oberon (14.1) and Titania (13.9).

I have also seen Sirius B numerous times with the 8" dob at magnifications as low as 150x. I actually find Antares B to be significantly more difficult as it is much closer to the primary.
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  #49  
Old 15-09-2014, 04:52 AM
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glenc (Glen)
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Ngc 6164

Paul and I did some observing last night with a 16". The most difficult object was NGC 6164 (top right of the star in the image). NGC 6165 to the lower left of the star is easier. Both of these nebula are in Norma. John Herschel discovered them with an 18.5" speculum reflector. It was 20' long and had no secondary.
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  #50  
Old 16-09-2014, 01:10 PM
ausastronomer (John Bambury)
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Originally Posted by tonybarry View Post
Hi Rob,

The WSAAG crew at Linden Observatory in the Blue Mountains tried one evening / morning in December 2013 to nab IC434 (the Horse) using the Evans 30" dob (0.75m aperture).

It was not visible, despite no moon and a pretty dark site, and we tried for two hours. People had seen the Horse about ten years before at the same site, but the light pollution from Sydney has only gotten worse since then.

The consensus was that it is a doable target if the skies are dark enough. Otherwise, it is not a visual target.

Regards,
Tony Barry
Hi Tony,

I have observed the Horsehead on dozens of occasions over a large number of years. There are some "tricks" to observing it which I will pass on.

Firstly the technical stuff. I believe and I am open to be corrected, that the correct target designation for the Horsehead Nebula is Barnard 33 (B33) which is the dark nebula made visible as the Horsehead, against the illuminated background of emission nebula IC434.

Now to observing it. First and foremost let me say there are some people who may never see it visually, irrespective of how dark the skies and how big the telescope. The reason for this is that IC434 emits its light in the far red end of the visible spectrum at near infrared wavelengths. Some peoples eyes are not sensitive enough at the red end of the spectrum to actually see the emission nebula IC434. If they can't see IC434 they can't see the Horsehead. This scenario was showcased a few years ago at IISAC, maybe in 2008. Andrew Murrell and I were running sky tours with the 18" and 25" 3RF Obsessions. A couple of people asked me if I could put the Horsehead in the 18" Obsession, which I did. I was not using a filter at this time and it wasn't all that difficult a target for me under pretty good skies (Linden isn't what I would call "pretty good", I would call Linden "fair"). Only about 1/2 the people observing at my scope could see it. One of the people who couldn't see it was a colleague and a very experienced observer. I couldn't figure out how I could see it so easily and he could not see it. I then asked Andrew Murrell to put the Horsehead in the 25" Obsession, which he did. In the 25" Obsession it was a simple target for Andrew and I without a filter and with direct vision. Our colleague and a couple of other people still could not see it in the 25" Obsession. I was somewhat baffled by this so I subsequently spent a lot of time researching why this might be so. What I came up with was different individuals own eye sensitivity to light towards the infrared end of the visible spectrum. I have discussed this subsequently with a number of experienced observers and they have agreed with me on this.

Some tips to enable you to see the Horsehead. I have observed it in scopes down to 10" aperture under pristine skies, although it's a very tough get in a 10" scope and it is a target you would normally chase in scopes > 14" aperture.

1) Dark Transparent Skies. You will struggle to see it anywhere within 100km of Sydney. I would call dark skies anything over 21.3 on a properly calibrated SQM. Places like Ilford, Bucketty, Lostock and some places in the Southern Highlands like Canyonleigh etc and several others, within reasonable proximity of Sydney, will be good enough. Places like Coonabarabran and Mount Kaputar will be better still.

2) Clean optics always help as they increase contrast and reduce light scatter.

3) Use a high light transmission and high contrast eyepiece having an exit pupil between 3mm and 5mm, 4mm is ideal. A 4mm exit pupil gives you the right contrast ratio. In other words in an F5 scope you would use about a 20mm eyepiece. In an F4.5 scope about an 18mm eyepiece and in an F4 scope about a 16mm eyepiece. A couple of mm in focal length either side of this will be fine. What you don't want to do for example is stick a 31mm Nagler or 27mm Panoptic in an F4.5 scope. The large exit pupil will reduce contrast too much. The eyepiece doesn't have to have a huge FOV. A medium FOV eyepiece between 45 and 70 degrees is probably best, but don't be scared to use a 17mm Nagler T4 for example if this is the focal length you need.

4) Try for the Flame or Tank Tracks nebula (NGC 2024) first, before you try for the Horsehead. The Flame Nebula is a little to the east of Alnitak (Zeta Orionis) and is illuminated by it. If the conditions and the telescope are not good enough to see the Flame Nebula, don't waste your time trying for the Horsehead.

If the Flame Nebula was doable then try for the Horsehead. It is located South of Alnitak and you need to push Alnitak just outside the FOV of the eyepiece. Pushing Alnitak out of the FOV greatly increases the contrast within the FOV.

5) A H-Beta filter is the filter of choice but if you do not have one don't despair. A wide bandpass UHC filter helps a lot. You need to use a UHC filter that has a high bandpass in the H-Beta line at 486nm and a bandpass in both OIII lines at 496nm and 501nm. My Astronomiks UHC filter works very well in my 18" Obsession. Not quite as good as my dedicated H-Beta filter, but not far behind it.


I think that just about covers it. Good Luck !!!

Cheers,
John B
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  #51  
Old 16-09-2014, 03:09 PM
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Hi John,

Many thanks for your tips on observing the HH.

Your suggestion that the failure to observe was due to red sensitivity in the eyes of the viewers is intriguing. I shall share your post with other members.

You comment that the sky at Linden is now just "fair" rather than "dark" and yes, when objects are in the east and in the Sydney skyglow, it is a sad situation. To the north and west it is not so bad. But it is not pristine (to use your term). Still, it's WAY better than trying from UWS Penrith (closer to Sydney). On the plains, the light pollution is really serious.

Regards,
Tony Barry
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  #52  
Old 17-09-2014, 09:07 AM
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Terry B
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Quote:
Originally Posted by ausastronomer View Post
Hi Tony,

I have observed the Horsehead on dozens of occasions over a large number of years. There are some "tricks" to observing it which I will pass on.

Firstly the technical stuff. I believe and I am open to be corrected, that the correct target designation for the Horsehead Nebula is Barnard 33 (B33) which is the dark nebula made visible as the Horsehead, against the illuminated background of emission nebula IC434.

Now to observing it. First and foremost let me say there are some people who may never see it visually, irrespective of how dark the skies and how big the telescope. The reason for this is that IC434 emits its light in the far red end of the visible spectrum at near infrared wavelengths. Some peoples eyes are not sensitive enough at the red end of the spectrum to actually see the emission nebula IC434. If they can't see IC434 they can't see the Horsehead.

snip

5) A H-Beta filter is the filter of choice but if you do not have one don't despair. A wide bandpass UHC filter helps a lot. You need to use a UHC filter that has a high bandpass in the H-Beta line at 486nm and a bandpass in both OIII lines at 496nm and 501nm. My Astronomiks UHC filter works very well in my 18" Obsession. Not quite as good as my dedicated H-Beta filter, but not far behind it.


I think that just about covers it. Good Luck !!!

Cheers,
John B
Jonn
Interesting description.
My only comment though would be that if you are using a H-beta filter you are filtering out all light except for the green coloured H beta line.
For this line it doesn't matter whether you eye is sensitive to the deep red of a H-a
I don't know how much H-beta IC434 emits but there should be some.

Terry
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  #53  
Old 16-10-2014, 06:19 AM
N1 (Mirko)
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For me, it's the Gegenschein and the Light Bridge connecting it to the Zodiacal Light.
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  #54  
Old 16-10-2014, 12:45 PM
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ZeroID (Brent)
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Hamburger, NGC 5128. Went hunting for it to image and could only just see it through averted vision. Mind you, it was from my rather LP'd Ob site in Auckland.
I got enough frames to get an ok pic from it with some push in the processing.
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