Tarantula Nebula NGC2070

Hagar (Doug) · #1 13-05-2010, 09:58 AM

Last night was a lovely night here in the hills. Seeing was as usual scratchy with highh level wind blowing over the top of the mountains.

I decided I would give tarantula nebula a bit of a go. I thought in the past I have always managed to burn out the core so thought I would use a range of exposures to blend the core properly. I took a series of 1 minute, 5 minute and a few 10 minute exposures for this process.

When I finally looked at the exposures I was a little surprised that the 1 minute exposures had still managed to burn the core so it looks like I will need some shorter exposures for the core.

I have included the total combined image and the 1 minute exposure combined stack to show the burnt core. No processing was carried out on the 1 min exposure except the stacking and combining.

Takahashi FSQ106ED at f5, QHY9 with QHY RGB Filters.

Hi res image: http://www.darkskyau.com/cm/displayi...256&fullsize=1 (1.5MB)

Thanks for looking.

Adelastro1 (Wayne England) · #2 13-05-2010, 10:09 AM

Nice work Doug. I was out looking at this last night with Uni students as part of their Astronomy prac north of Adelaide but looking over the city lights. Wish I was over your way though! Still, I was wishing I had time to take a few snaps of it as it looked impressive through the 12in and the students were suitably impressed too.

What set up did you use to take it?

Wayne

TrevorW · #3 13-05-2010, 10:26 AM

Nice wide field Doug

Hagar (Doug) · #4 13-05-2010, 11:12 AM

Quote:

Originally Posted by Adelastro1

Nice work Doug. I was out looking at this last night with Uni students as part of their Astronomy prac north of Adelaide but looking over the city lights. Wish I was over your way though! Still, I was wishing I had time to take a few snaps of it as it looked impressive through the 12in and the students were suitably impressed too.

What set up did you use to take it?

Wayne

Thanks, The setup, Takahashi FSQ106ED at f5, QHY9 mono with QHY RGB filters, guided with QHY5 and WO 70mm APO all mounted on Losmandy G11 with Gemini. 2 second guide intervals.

Quote:

Originally Posted by TrevorW

Nice wide field Doug

Thanks Trevor. If it's clear agin tonight I will try to add to the image with some more 10 min exposures and some very short exposures.

Lester · #5 13-05-2010, 12:22 PM

Very nice image Doug, I like the colour.

All the best.

multiweb (Marc) · #6 13-05-2010, 12:34 PM

You've done good Doug.

That's a hard one to image. Too many stars, to much nebulosity, looks like a bag of noodle at any FL. The closer you get the messier it gets. Can't win with that one.

Omaroo (Chris Malikoff) · #7 13-05-2010, 12:48 PM

Yep - well done Doug. As Marc says - it's a really difficult wish-washy area to image. Nicely done

Hagar (Doug) · #8 13-05-2010, 04:25 PM

Thanks Chris, Lester and Marc, yes it's a pretty busy area but it does test out the camera and more so the overall processing skills. Mine aren't the best but improving all the time. (I hope).

mill (Martin) · #9 13-05-2010, 05:36 PM

Looking good Doug

The tarantula is almost as hard to process as M42.
That is why one is gone now and the other comes up.
This is to save us from processing disorder

Well done. I am looking forward to more.

gregbradley · #10 13-05-2010, 09:36 PM

You got the colours very nicely. I can't help feeling with some of your images that your focus is just a little bit off. But then again you are imaging with the relatively "small" chip 8300 which gives larger image scale. Is your focus spot on? Are you confident you got the focus as sharp as it'll go? A robofocus or FLI PDF is handy for an FSQ.

The other possibility is the 8300 chip has small wells so I wonder if the 5 minute subs show the stars as tighter than the 10 minute subs. I notice with my 8300 chip that brighter stars spill over and bloat fairly easily with this chip. If you have low read noise then perhaps 5 minute exposures may end up with a tighter looking image without any consequence to the overall noise and brightness. I am going to explore that aspect myself on neb type shots to see if it produces tighter stars.

Greg.

Hagar (Doug) · #11 13-05-2010, 09:50 PM

Quote:

Originally Posted by gregbradley

You got the colours very nicely. I can't help feeling with some of your images that your focus is just a little bit off. But then again you are imaging with the relatively "small" chip 8300 which gives larger image scale. Is your focus spot on? Are you confident you got the focus as sharp as it'll go? A robofocus or FLI PDF is handy for an FSQ.

The other possibility is the 8300 chip has small wells so I wonder if the 5 minute subs show the stars as tighter than the 10 minute subs. I notice with my 8300 chip that brighter stars spill over and bloat fairly easily with this chip. If you have low read noise then perhaps 5 minute exposures may end up with a tighter looking image without any consequence to the overall noise and brightness. I am going to explore that aspect myself on neb type shots to see if it produces tighter stars.

Greg.

Interesting comments Greg, You are not the first to comment on focus but I can assure you focus is as good as it gets. I have been using Robofocus and focusmax and with like comments have gone back to the Bahtinov mask and Bahtinov grabber only to find the autofocus routine in Maxim and FocusMax are spot on. I have even gone to the extent of taking one image each LRGB then refocusing.
I can only put it down to poor seeing here in Mt Beauty. Although a very dark area it does suffer from thermal aberations from the surrounding mountains and often suffers from high level wind blowing overhead while it is perfectly still down here in the bottom of the valley.
There is a marked diference between 5 and 10 minute images but not really in star sizes.

An example of the seeing here: I think I have only had 2 occasions when the FWHM of captured images has been below 3.5 and I have seen another couple but haven't been imaging. Most of the time it is around the 5 mark.
Thanks for the comments. Too many variables.

Hagar (Doug) · #12 13-05-2010, 09:53 PM

Quote:

Originally Posted by mill

Looking good Doug

The tarantula is almost as hard to process as M42.
That is why one is gone now and the other comes up.
This is to save us from processing disorder

Well done. I am looking forward to more.

Thanks Martin. By the way Tarantula is up all the time this
far south.

gregbradley · #13 13-05-2010, 09:58 PM

Yeah FWHM of 5 is pretty rough. Last time I checked at my dark site it using CCDsoft focus graph to tell the FWHM is was between .95 and 1.5.
I think that was better than normal but 5 seems very high.

That would account for it. Don't get me wrong lovely images just the same. We are all limited by the local conditions.

Greg.

mill (Martin) · #14 13-05-2010, 10:43 PM

Quote:

Originally Posted by Hagar

Thanks Martin. By the way Tarantula is up all the time this
far south.

For me it is not really.
Melbourne is in the South/West with it's nice light pollution

So i can only image it when it is in the East/South.