[AstroFest] Eta Carina Nebula with a small scope

[Camelopardalis]

Folks - I've tried this one before from LP central here and wanted to give it a go from somewhere a little darker...

This is a stack from a bunch of frames collected over a few nights from below 35 degrees altitude, down to about 20. 40x 4 minute subs at ISO1600 with the Canon 1100D attached to the WO Zenithstar 71 + reducer/flattener on EQ6. Certainly the longest set of exposures I've captured so far!

I'm not sure where to go with this one, much of the detail popped easily, but any advice/suggestions/etc appreciated as always. It's a little small because of JPEG compression working its evil ways on anything any larger :(

[LightningNZ]

40 minute subs? Holy smokes that's long. I think the low altitude is leaving it looking a little washed out compared to what it could be if it were higher? Don't know, it's far better than anything I've ever produced!
Cheers,
Cam

[Camelopardalis]

:lol: my bad, 4 min subs (corrected original too) :sadeyes:

Washed out could just be my dodgy processing :eyepop: I've been trying to keep the stars in check, after my Veil experience, but it wasn't very high it's true, although the sky was pretty good to fairly low down. Of course I want to try it again when it's higher, it's just a good practice object :D

[RickS]

Looks pretty decent, Dunk! It's a nice bright object so good to practice on.

[cometcatcher]

Nice Eta Dunk. Did you use an LP filter on this one?

[Camelopardalis]

Thanks chaps! No filter, just plain old air...I've only got a UHC type and OIII. Would either of these work? Suppress the stars?

I definitely need the practice...nebulae seems to be the objects I'm struggling with at the moment, so any hints/tips/techniques you'd be free to share would greatly appreciated :)

[cometcatcher]

The OIII would be no good for OSC. Which brand of UHC? Some are dual band with added Ha, others are not.

[Camelopardalis]

It's a DGM NPB.

Would the OIII not be any good for the Veil, or is it the OSC of my camera that's the problem for these wavelengths?

[MrB]

Why?

[cometcatcher]

OIII would not make for one shot colour, which is why I worded it carefully. ;) Sure you could use it, and add it to the green channel. But then it's no longer OSC.

[cometcatcher]

According to the graph I have, the DGM NPB could be used for one shot colour as it passes Ha and OIII. It looks quite narrow band. Expect long subs to compensate and funky star colour.

[Rob_K]

Here's a graphic of why it is necessary to pass OIII & Ha when taking images of the EC Nebula. I've used a Star Analyser grating to obtain a spectrum which clearly shows the strong emission of the nebula in those wavelengths. The zero order images of Eta Car and the nebula are at left, spectra to the right.

This explains the correct magenta-ish colour of EC Neb (red & blue combination), different to the bright reds of principally Ha-emitting nebulae. If you see bright red renditions of EC Neb it is either that the photographer has used Ha filters (filtering out OIII) or it has been colour-balanced or otherwise changed during processing. :thumbsup:

Cheers -

[RobC]

So do you or don't you use Ha or OIII filters with an OSC ?

Thanks

Rob

[LightningNZ]

Thanks Rob, that's really good to know. If you have similar spectra for other well known deep sky objects it'd be great to see them together as a resource.
Cheers,
Cam

[Camelopardalis]

Top stuff chaps, so I should try to get some time with my narrow pass band filter next time I'm up a bit further north then? :D

[cometcatcher]

RobC, you can use OIII and Ha filters with an OSC camera. But... to get full colour you need to take more than one shot since each filter will produce monochrome results. So it's no longer "OSC".

Narrow band with an unmodified, uncooled DSLR also works poorly. The exposure times are much longer, so the noise can be a problem. Forget it in summer. I've seen excellent NB results with modified, cooled DSLR's however.

[kkara4]

awesome picture Dunk!!!. gah makes me want to stake a spot out west now away from the burbs!

[cometcatcher]

Dunk, I think that filter will work better from your LP home rather than a dark sky site.

[Rob_K]

Cam, here's a couple I did a while back - click to full size if necessary.

Nice image in OP by the way - well done Dunk! :thumbsup:

Cheers -

[Camelopardalis]

Thanks chaps! I'm thinking it's got a bit too much red in it? What say you all? :confused2:

Love the spectra Rob - keep 'em coming :)

Might give the filter a go at some point then :D How much exposure time should I be looking to add?

[cometcatcher]

At least a factor of 4, possibly 10. It's not really meant for photography but visual use. It only lets through about 10% of light. Be interesting to see what it does but I think it will be too harsh. That's if you can get enough light in the first place.

[Camelopardalis]

Ah OK thanks Kevin...not sure I'll be able to get that sort of exposure time for a while :(

Would it be wildly different if I had my camera modded?

[cometcatcher]

It would help some, but that filter is extremely narrow. Not really designed for imaging.

If you want a filter for imaging in one shot, consider the Astronomik UHC-E, Baader Semi-Apo or Idas LPS filters.

[Camelopardalis]

Ah OK thanks, will out them on my list for Santa :lol: