Hunting DSOs just above the southern horizon

[Martin Meredith]

We've seen the Lodestar pulling out faint objects under LP and with the moon present, so I wondered what kind of results  could be obtained for objects that culminate close to the murky horizon, objects we might normally give a miss. 

So, in reverse order of maximum height above the horizon, here are a few shots from last night, taken from 36deg 37' N, and facing south . All are objects to be found in Centaurus. This was a long 3+ hour session waiting for objects to culminate, and LodestarLive didn't miss a beat.

There are tons of faint galaxies in Centaurus, many in the Centaurus Galaxy Cluster. Here are a couple of 60s captures centred on ngc4622 and ngc4709 near to culmination at a mere 11-12 degrees above the horizon. I've labelled some of the brighter galaxies here. Obviously, we're going to struggle to see much beyond 13-14th magnitude, but that still leaves a nice-looking field.

Now, getting lower, here's NGC3680, a rather sparse open cluster at less than 7 degrees: (60s)

What about the edge-on Mag 8.4 spiral galaxy NGC4945 which reaches a mere 4 degrees on culmination? (60s)

Finally, Omega Centauri, literally within a minute of rising and well under 1 degree above the sea (30s exposure)

BTW the above is more or less how it appears in 10x50s when about 4-6 deg high.

To make matters worse in the case of Omega Centauri, things got more tricky a few moments later when it got caught in the beam of the powerful Cadiz lighthouse. No amount of stacking is going to remove this kind of artefact ;-)

Sure, none of these are going to win prizes in AP, but if we're mainly interested in seeing more stuff and picking out some of the basic details of objects at this challenging altitude, then nothing is off-limits -- this might be the only way we ever get to see certain objects.

Thanks for looking!

Martin

[oldpink]

streetlamp LP is one thing but a lighthouse
doubt a LP filter would be of any use either

nice shots for some very low objects

[RCompassi]

Lol, LP filter for a lighthouse is a welders mask! But you will need a couple hours of integration time.

Nice pictures!

[DoctorD]

Hi Martin

this is truly the spirt of Video Astronomy - "seeing" things we would otherwise be unable to see - well done!!

CS

Paul

[nytecam]

Amazing images of those southern DSOs - well done :-)

[Dragon Man]

 -- this might be the only way we ever get to see certain objects.

Martin

Except when us Aussies are broadcasting these objects on NightSkiesNetwork as they go directly overhead for us  

Excellent results Martin for such low altitude objects!

Now you know how I feel trying to show Northern Objects from down here 

[Martin Meredith]

Thanks oldpink, RCompassi, DoctorD, nytecam and Dragon Man for your comments.

I also collected an image during the same session (not so low though!) which I found intriguing:

This is the globular M68 in Hydra

What's that planetary nebula just to the upper right of the glob, I wondered?

Focus is clearly off a little, a big problem for me with this scope, but according to SkySafari this is a mag 11.3 star, similar (in mag) to one of its unbloated neighbours. The four prominent stars at the base are all around mag 9, so the bloat seen around the marked star doesn't seem to be simply a question of magnitude. In fact, the nature of the bloat is different as the 'central' stellar object can be seen, shining with a reddish hue.

I looked on a number of other images (Wikisky and SDSS via Aladin) and found that on those the star in question appears not bloated but definitely larger and quite red. So this set me searching more and according to Aladin sources it turns out that this is an S-class star, not quite a carbon star but intermediate between M and carbon. 

Then I recalled something I'd read in Berry and Burnell about a rare form of artefact. They say (presumably about a different object) that this is a deep red star and that we're seeing out-of-focus infrared light (mine being an achromat) at the extreme range of the CCD's sensitivity curve. I also think nytecam mentioned something about this in one of his posts but I can't lay my hands on it right now.

Is this the correct explanation?

Thanks

Martin

[Martin Meredith]

I mean 'upper left of the glob', doh!

[nytecam]

Martin - pretty sure appearance of star Nf M68 is "IR-bloat" eg the refr unable to bright NIR to a common 'visual' focus that the lens is corrected for.  Effectively your lens is priducing a 'circular' [rather than normal linear] spectrum of IR and even with a colour camera it will be colourless [or maybe a cyan bias] via the unfiltered Lodestar-C. 

I get IR-bloat to a lesser extent via my SCT when I use a [lensed] focal reducer which I do most of the time.  A two mirror Newt [and no lensed FR] will be free of this chromatic aberration.  An IR-block filter will elliminate this effect on a refr but kills about 1/3-1/4 of camera sensitivity  You decide!