NGC 1858 and friends

[rat156]

Hi All,

Here is at least three NGC objects, NGC 1858, 1850 and 1854/5.

Two hours of 20 minute Ha, combined with half and hour of R, G and B in five minute subs.

8" RC with SBig setup.

There is one interesting star in this that lights up in the Ha but not in the red channel, it is cropped from the original subs and the combined, anyone have any ideas as to why this is so?

Cheers
Stuart

[Octane]

Could it be a planetary nebula? *shrugs* No idea!

It looks a different hue of red in the RGB composite.

Are these neighbours in the Large Magellanic Cloud region?

Regards,
Humayun

[rat156]

Hi Humayun,

The planetary nebula is my best guess from my extremely limited knowledge of such stuff.

The different hue is due to the large Ha contribution in the Luminance channel, like the nearby nebulae.

Yes, theses are in the LMC, it's my idea of widefield :)

Cheers
Stuart

[sjastro]

It's definitely a planetary. The fact it is visible in Ha and not red indicates a line spectrum that is outside the bandwidth of your red filter.

Stars on the other hand have continuous spectra and should be visible in both filters.

A fine image.

Steven

[rat156]

Hi Steven,

But the Ha emission line is covered by the Red filter.

Here's an animated gif of the region. I normalised on a star and the background, there is a corresponding increase in intensity of all the Ha in the picture, as well as the star in question, so I suppose it could be filter related in that the Ha filter has a much lower background count?

Cheers
Stuart

[AlexN]

Ha will always have a lower background count than a R filter...

Ps - Great image mate, Another in your series of obscure targets... I must say, its not common to see someone post consecutive, high resolution images of nebulae in another galaxy... :) Impressive.

[AlexN]

Looking at the animation, I think the target is visible in both images, it is just a hell of a lot more prominent in the Ha image... That would indicate that its a Ha target, so, planetary nebula is a fair guess I would imagine.. The reason it shows so much brighter in Ha is that nothing else is hiding it (ie - skyglow/moon glow etc..)

[rat156]

Thanks Alex,

Like I said it's my way of doing widefield....

Cheers
Stuart

[AlexN]

:) a very nice wide field it is... Although, from memory back when I had the 8" RC and ST10, your field of view is... well... claustrophobic... to say the least :D

[TrevorW]

Depends on the target Alex

Nice one Stuart but looks like it could do with more subs

Cheers

[rat156]

Yep, got another two hours of Ha data, but I need new darks as I could only get down to -5C last night for the Ha, -10 for the colour.

I have used scaled darks for this, but it is causing trouble. Needless to say I can't get the camera down to -5 ATM.

Cheers
Stuart

[AlexN]

The size of the field of view does not depend on the target? More, some targets seem small despite the claustrophobic FOV.. :) :P

[sjastro]

Hello Stuart

I suspect the your red filter transmission is trailling off at the Ha wavelength. This probably has a greater effect than the lower background count through the Ha filter.

Steven

[rat156]

Hi Alex,

I think what Trevor was eluding to, as indeed I was is that this stuff is in the LMC, which, by comparison to most of the other stuff you'll see here, is a long way away, hence widefield. Taken to an extreme, I capture extremely widefield images of other galaxies often. So I substitute a wide angle lens (and the corresponding ease of tracking) for a 1625 mm FL scope and a target that's a long way away. I'm starting to think I'm nuts!!

Cheers
Stuart

[AlexN]

You're not nuts mate.. Narrowfield imaging (or I suppose extreme wide field depending on which way you look at it :D) is the best type in my opinion...

Nothing I like more than seeing something up close and personal.. The 8"RC + ST10 is awesome for it! :)

[Dave_H]

The object is:

IRAS 05081-6855; or
SMP LMC 28

It is a planetary nebula in the LMC. [Humayun was correct in his guess!]

Anyone wanting to investigate 'odd' objects in their images should take the time to become familiar with the Aladin program of the Centre Donnees Stellaire. It is a simple executable downloadable from:
http://aladin.u-strasbg.fr/aladin.gml
which allows you to plot catalogue identifiers overlaying survey images, with tools to easily extract the catalogue info. There are versions for all platforms. For investigating what is on your images, it makes any commercial planetarium software a child's toy.

Dave

[Bassnut]

Some nice detail there Stuart, for only 20min Ha, more should do the trick nicely.



I cant get to -10 often in the summer, so I use water cooling... and now I always do :).

Once its set up, its easy, set and forget, never a bother. Tipping a bit of ice in the bucket 1st up (if required) is a routine that gets you in the groove, and its satisfying to watch the temp plummet regardless of ambient :thumbsup:.

[rat156]

Thanks Dave,

I actually stumbled upon Aladin and identified the object myself late yesterday. It's a great tool for this type of thing. I had no idea that there were so many planetary nebulae in the LMC! I found a paper by Reid and Parker reporting the discovery of 471 PNe in the LMC, published in 2006. This one was one they confirmed, so it had been previously identified. Interestingly they used pretty much the same method (albeit with a much larger scope) to find the PNe.

Cheers
Stuart

[strongmanmike]

:rofl: SBIG camera cooling method in the summer months

Just a little joke Fred :poke: :scared3:

[AlexN]

Teehehehehe

[Bassnut]

Yeah well, sad but true. The ST10 is not flash in the cooling department, at all. But then I wouldnt trade 90% QE for any amount of tricky cooling :D

Come to think of it, thats exactly how it looks, after a few southerns, struggling up the cliff, in the pitch dark :lol:

[AlexN]

90% QE is hard to sneeze at thats for sure.. -60c delta temps wont help you catch more signal... it will just slow nose from drowning out whatever signal your camera catches... If there is one thing I miss from my ST10 its the sensitivity.. Why cant they make a larger sensor with 90% QE :(