NGC6357&6334 in 3nm Nitrogen NII

[avandonk]

Had a short window last night between clouds.

This is only four frames of four minutes each taken with 3nm NII filter.

These objects seem to have about the same if not a bit more of NII versus HA. NII is a forbidden transition of Nitrogen and needs hot or very hot blue stars to produce it.

The HA filter is 3nm wide centered on 656.3 nm. The NII filter is also 3nm wide and centered on 658.4 nm. Any HA filter that is wider than about 5nm actually picks up both these transitions. It should be interesting down the track to see what objects have very different distributions of H and N.

Below is a diagram from Astrodons site.

Here is the large image at full resolution 6MB

http://d1355990.i49.quadrahosting.com.au/2012_04/ngc6357&6334_NII.jpg

Once I get the guiding etc sorted will do much longer exposures.

Bert

[strongmanmike]

Man, looks like you could image through a ND1000 neutral density filter and still get stuff :eyepop:

Mike

[Paul Haese]

Looks like there is a little field rotation in this image too. The NII should provide an interesting colour and detail perspective to images though.

Get that guiding going Bert and let's see what you can do with the system.

How deep are you cooling at present?

[avandonk]

Mike I tried to image with the scopes cover on. Did not work!

[avandonk]

Paul I have the temperature set to -20.0 C. This will give me head room in hot weather. I do not want to muck around with different temperature data it is confusing enough with nine filters.

Bert

[strongmanmike]

I have used -30C all year for two years now with my PL16803, only had to wait an hour or so one night for the temperaure to drop below +28C :)

Melbourne area should have no worries operating at -30C :thumbsup:

Mike

[avandonk]

Thanks for the info Mike. I may go down to -25.0 C as too many summer nights lately in Melbourne can be over 30C till after midnight.

Is there all that much difference lower than -20C?

Bert

[multiweb]

Simply awesome. Loads of details. :thumbsup:

[Peter Ward]

So the learning curve starts... good stuff.

Did you reduce the data Bert? (i.e at least dark subtraction) as that hot column should have subtracted out.

[gregbradley]

Great start Bert.

I set my Proline to -30C in warmer nights but usually I use -35C most of the year. Darks at -30 or darks at -35 whilst not being totally accurate, because the image is so clean anyway you will not see a difference. I have both -30 or -35C but to use -20 you may as well have used some other brand. High cooling is FLI's main feature and high cooling solves almost all camera image issues. Richard Crisp did a good paper on that - its not just the thermal noise its defects etc that fade as cooling gets deeper.

Does it make a difference? Yes. That column will fade at lower temperatures placing less emphasis on your darks getting it.

The images will be almost noise free. This makes it easier for darks and flats to work their magic.

Especially with narrowband and 3nm you will need the lowest noise you can get. Noise reduces by half every 6C drop in temp on these chips so -20 to -35 is what, about 6 times less noise?

Greg.

[avandonk]

Thanks Greg. Collecting darks at -30 C right now. Will do another lot at -35 C when it is cooler.


Bert

[Paul Haese]

Just caught up with this. Yes going deeper makes a huge difference. Every 6 degrees halves the noise level upon stretching. One of the reasons I bought the new 683 was the increased cooling capacity. I have been usingg -25C easily and the extra cooling has helped a lot with images. Your gear should be able to hold -30C easily. Graeme has a micro line and it holds -30C all year long. Your camera has slightly better cooling still and you could do as Greg has suggested.