BIG observing session! 25-26/7/09

[SAB]

After a cold and cloudy Melbourne Saturday, I was stunned out of my jocks to see that all the Melbourne cloud was evaporating before my eyes as dusk fell.

Yes, it was actually happening, the first clear night in 150,000 years. Better take advantage of it! So all the gear was out the door faster than you can say "zOMG clear skiez in Melbs!!1!"

The night was windy, very windy. But that also meant there was no chance of dew. And seeing was actually quite decent, not perfect but certainly better than anything I've had in the last year (translation: last 5 sessions). I was using my 12" F/4.6 dob for this session.

Equipment: 12" F/4.6 dob

Time: 10:00pm-3:15am

Seeing: 5-6/10

Transparency: 3/5

M57

Kicked off the night with a look at the Ring Nebula. I was surprised by how well it showed, despite it's very low elevation in the murk hugging the northern horizon. I've never actually seen the Ring in the 12", and I was not dissapointed. At 176x, its not-quite-perfect donut shape was obvious, and the northern/southern sides of the ring were distinctly brighter than the ends. The OIII filter rendered the ring to be more uniformly bright, that is the brightness difference between the long axis and the ends was not as obvious. The interior was clearly brighter than the background sky.

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Although I had planned to observe some PNe's, I was distracted by the cool stuff in Sagittarius. I never actually made an attempt to properly observe all the cool stuff there with the 12", so now was time.

M20 Trifid Nebula

At 83x, The dark lanes in the "pink" portion were visible, and easy to detect with averted vision. The "blue" part of the neb was fainter, but appeared to be unevenly bright with a darkening towards the centre, which is marked by a bright orange star. I then added the UHC filter, which greatly accentuated the "pink" part of the nebula, with the dust lanes now easily visible. The southernmost lobe is brighter than the rest of the structure. The "blue" bit remained virtually unchanged.

M8 Lagoon Nebula

At 83x with a UHC filter, the Lagoon was awesome!!! blumming stunning! The cloud took up virtually 3/4 of the field, with the faint outer regions seen in photos clearly visible. Dark rifts break up the nebula into 4 distinct sections, with the two bright sections familiar to observers accompanied by a fainter elongated East-west filament to the north and even fainter haze to the west of the main complex.

M17 Swan Nebula

Again using the 83x EP with UHC filter.... absolutely fantastic. Very bright, and the distinct shape was as obvious as it is on long exposure photos. A fainter filament looping out from the swan's tail and around below the body was clearly visible, as was a bright knot just above the curve in the neck. Increasing power to 176x with the UHC revealed a superbly detailed body, which appears to be superimposed on a fainter background haze which follows the countours of the brighter nebulosity. Infact, the detail in the nebulosity was so complex that it would be a challenge to sketch. Almost a 3D experience. A fainter pool of nebulosity was visible to the north of the main body and adjoining it. In addition, two detached small faint knots of nebulosity were obvious along the extended centreline of the neck.

M16 Eagle Nebula

Faint at 176x without a filter, but the UHC helped alot. With the UHC in place, the nebulosity resembled a swept airplane wing viewed from above or below, oriented NE-SW. An L-shaped dark region was visible adjecent the SE edge of the associated open cluster, with a narrow finger oriented NW/SE pointing towards the centre of the cluster visible with averted vision.

NGC 6772

PNe in Aquila. Quite difficult to detect at 216x without a filter, but the addition of the OIII helped considerably. A large, rather faint oval or oblong shaped ring was visible, with the interior noticably brighter than the background sky.

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At this point it was near midnight, and decided to take a look at Jupiter. Seeing was actually decent, but that being said, it was not perfect. With it still toward the east, the scope was broadside to the wind so was being heavily buffeted. At 176x, to my surprise, I could clearly see the Impact scar, neatly in mid-transit! It appeared as a tiny greyish smudge, visibly elongated E-W.

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Now, with the eye-candy picked off, it was time to hunt some galaxy clusters....but not before answering the call of nature. Upon entering the crapper facility, I almost made the fatal error of turning on the light (well, it's been an integral part of every potty excursion for the entire duraction of my life thus far...). After almost flushing my hard-earned night vision down the toilet, it was time for some hot chocolate and choc chip cookies. Ahhhh, a clear night, great DSO observing with some hot choc and cookies....can life get any better? That's right, it can't

Re-energised and relieved, I was set for some faint galaxies *yay*.

Abell S 805

A cluster of galaxies in Pavo. The group is easily located by dint of 4 mag 10-11 stars arranged on the western side of the GX cluster in a distorted trapezoid with the long axis oriented NW/SE. A 5th mag 12 star creates a triangle wit the two southernmost stars.

At 283x, the brightest galaxy, IC 4765, was relatively easy to see, as a small, slightly elongted (E-W) blob of light.

Just to the south of IC4765, and adjacent to the north of the star TYC 9073-467-1, is the small high SB elliptical PGC 62408. This GX was actually fairly easy to spot, owing to it's high SB, and was actually the second brightest of all cluster members observed. Also visible on the northern edge of PGC 62408 was the MAG 15.9 star USNAO2-0225-29565747!!!

To the SE of IC4765 is the elliptical GX PGC 62393. This galaxy is located on the northern edge of a small quadralateral of mag 12-14 stars. This GX was extremely faint, at the absolute limit of vision.

Located roughly midway between IC4765 and the mag 11 star TYC9703-1126-1 to the east is PGC 62391. Another very difficult object, virtually at the limit of detection, although it was slightly easier to spot than PGC62393.

To the northwest of IC4765 is the edge on spiral IC 4766. This GX was also extremely faint, but it's NW/SE elongation was visible in momentary glimpses. I'd rate it as difficult as the above PGC members despite its larger size, owing to it's low surface brightness.

The 4th confirmed hit was another edge on spiral, IC 4767, located SSE of IC 4765 on the outer SSE of the cluster. This galaxy appears to be the second-largest of the group on DSS images, but has an extremely low SB. It was incredibly difficult to spot, and when I did manage to see it, it was only in momentary glimpses. After several minutes of intent observation, it's NE/SW elongation was glimpsed. I'd rate this GX as the most difficult of the lot. To find it, I used an isoceles triangle of mag 14-15 stars for reference with the point aiming NE, with the galaxy just off southeast edge and in the same orientation.

About 2 high-power eyepiece fields north/northeast of this complex is a chain of 6 very faint galaxies, dominated by the spiral IC 4769. This GX was not particularly difficult, owing to its relatively high SB core. It was easy to find by using two mag 15+ stars (and a third 14.3 mag star) framing its southern end. The other 5 galaxies are extremely small, faint and escaped my grasp.

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Abell S 912

Galaxy cluster in Microscopium. Initially I used a mag of 283x, and after much searching, finally found the main cluster member, the large elliptical NGC 7012. The galaxy is accompanied by a mag 12.1 star on its SSW edge, which provided a good waypoint. 7012 was relatively bright, and I do mean relatively! Simply appeared as a small hazy blob, with perhaps a slight E-W elongation visible.

Only one other cluster member was seen with certainty, and that is PGC 66118, located just to the SE of 7012. This GX appeared almost as bright as 7012, thanks to its compact high SB profile.

DSS images show 2 very small galaxies located in the small gap between 7012 and pgc66118, so I attempted to hunt these down. Increasing power to 353x, and upon careful scrutiny of the field, to my surprise I managed to catch glimpses of the tiny galaxy located in this gap. (Don't know what the catalogue number is). I've attached an image of this cluster with the GX in question arrowed.

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To finish off the session I had one last look at Jupiter. I was surprised by how sharp it was, at 272x I could see festoons and swirls in the NEB and SEB, including a nice big rift in the NEB. The main belts were wonderfully detailed, infact haven't seen the planet so sharp and well resolved before! What a nice way to end a great session

[Jamie]

A nicely detailed and well thought out report SAB.

I look forward to reading more of your reports when the weather allows.....Nice one!

[Talitha]

Thank you for a lovely report, SAB... excellent descriptions!

[Doc]

A wonderful read. Many of those objects are very low down for us here in the UK so I really enjoy reading reports from your part of the world.

You must have very dark skies to see some of that stuff, well done and I look forward to the next installment.

[bish]

Sounds like a very succesful observing session! Without wishing to repeat (copy?) what Mick said it's interesting reading about the objects that really low down for us in the UK. Thanks for posting

[Casus belli]

I love reading reports from the other hemisphere and this one was a real corker! Thanks SAB!

[albedo0.39]

I loved this report - not only for the detail but also for the information about DSO's which I'm unlikely to see from the northern hemisphere. All the previous comments are on the nail.

Good inspiration SAB - especially this bit

It was easy to find by using two mag 15+ stars

How are you making these out with a 12" ? That's really impressive

[Doc]

I loved this report - not only for the detail but also for the information about DSO's which I'm unlikely to see from the northern hemisphere. All the previous comments are on the nail.

Good inspiration SAB - especially this bit

How are you making these out with a 12" ? That's really impressive

It is very impressive. Our 16" Dobs will only muster mag 13.5 stars. But I do wonder how much further it would see from a really dark site.

[AndyBooth]

Very enjoyable report.

Very inspiring.

[SAB]

Thanks for your kind words on my observation everyone

I loved this report - not only for the detail but also for the information about DSO's which I'm unlikely to see from the northern hemisphere. All the previous comments are on the nail.

Good inspiration SAB - especially this bit

How are you making these out with a 12" ? That's really impressive

Yep. Infact, I can make out mag 15.9 stars with my 12". The faintest star viewed during the session was Mag 15.9 USNAO2-0225-29565747, located just south of IC 4765. This from my suburban Melbourne backyard, although my skies seem to be good by suburban standards, as I'm 42km from the city centre near the city's very outer reaches. It takes alot of patience and perseverance to see such faint stars from my location, but I found it amazing how much more you see with just 5 minutes studying the field. I also had a dark hood over my head to block stray light.

It is very impressive. Our 16" Dobs will only muster mag 13.5 stars. But I do wonder how much further it would see from a really dark site.

Thanks Doc! How dark are your skies? Mine are about 5.5 at best. Some people on another forum I participate in reckon I should see to mag 17 from a truly dark sky with my 12". My 12" dob is actually quite old, with dirty/scratched mirrors, but the optics have been figured to 1st rate standards by a well known local optitian.

[SAB]

Well I've downloaded CartesDu Ciel and the mags of the galaxies are: Not sure if these are visual or photograhic mags, but here they are:

ABELL S805

IC 4765: Mag 12.46

PGC62408: Mag 13.90

PGC62393: Mag 15.3

PGC62391: Mag 14.2

IC 4766: Mag 15.03

IC 4767: Mag 14.38

IC 4769: Mag 14.26

ABELL S912

NGC 7012: Mag 13.94

PGC 66118: Mag 14.00

Still can't get that other small galaxy, doesn't seem to be in any of the databases.

[SAB]

EDIT - disregard above post.

Downloaded the latest PGC catalogue for Cartes V3 and here are the updated magnitudes:

Well I've downloaded CartesDu Ciel and the mags of the galaxies are. Not sure if these are visual or photograhic mags, but here they are:

ABELL S805

IC 4765: Mag 12.34

PGC62408: Mag 13.78

PGC62393: Mag 15.12

PGC62391: Mag 14.02

IC 4766: Mag 14.98

IC 4767: Mag 14.36

IC 4769: Mag 14.10

ABELL S912

NGC 7012: Mag 13.80

PGC 66118: Mag 14.00

Still can't get that other small galaxy, doesn't seem to be in any of the databases.

[Talitha]

It is very impressive. Our 16" Dobs will only muster mag 13.5 stars. But I do wonder how much further it would see from a really dark site.

Wow, i've caught that stellar mag from here with the 8" SCT.. hie thee hence to a much darker site, Mick.

[JamesK]

Awesome report... People ask me if I ever run out of things to see, but even with a Limiting Magnitude of 9.5-10.0 and 11.0 when I get to a dark sky site, it really is a case of so much to see, so little time. If only I could get 5 hours of dark skies. A lot of those beautiful-sounding objects are well out of my reach, though, both in latitude and magnitude!

[Doc]

Thanks Doc! How dark are your skies? Mine are about 5.5 at best. Some people on another forum I participate in reckon I should see to mag 17 from a truly dark sky with my 12". My 12" dob is actually quite old, with dirty/scratched mirrors, but the optics have been figured to 1st rate standards by a well known local optitian.

My skies very rarely get beyond a visual 4.2 mag.

A couple of days ago I was attempting neptunes moon Triton. At mag 13.5 it was very hard but it did appear when the seeing improved so I persume mag 13.5 is about what I can see under my Light polluted skies.

[Beyond_Vision]

An excellent report SAB reading it one could almost imagine being there at the eyepiece too.

Regards

Kevin