Eta carina extreme comparison.

[batema (Mark)]

Hi,

I have attached two processed images of Eta Carina. Both were shot through a William Optics Flt 110 with guiding through PHD using an unmodified Canon 400d at ISO 800.

The first is a single 5 Min exposure that has been processed in Photoshop CS3.

The second is 15 x 5 Min lights with 7 x 5 Min darks with flat and bias flats applied. Stacked with DSS and processed with Photoshop CS3.

Strangely I really like the single shot however do not really know if the second one is a better result in terms of processing. The brighter stars have halo's around them and am unsure how to fix this or maybe I have pushed my levels too much. I tend to like the outer areas of the nebula in the second shot and the dtail but seem to have reduced the actual contrast of the keyhole.

Any comments would be muchly appreciated.

Mark

[astroron (Ron)]

Hi Mark, as you know I am not an astro imager, but the first one is more pleasant to the eye the second to me seems a bit overblown with the Eta star and keyhole just about non existent.
The whole image just does not look right
I still like the first one best

[Bassnut (Fred)]

The 1st ones pretty good for a one shot, but the second one is interesting. You have some exceptional detail buried in there, the guiding and focus are very good, but the whole pic is let down by awefull processing (colour, saturation, levels, curves, posted res).

You must have spent a lot of time getting the rig right, so now do the same in PS .

[bluescope]

The second image should look much better than the single shot Mark ... that's how this astrophotography game works ... the more data you add the better the image should be. You should end up with similar colours to the first shot only it should be smoother and more detailed.

It looks totally washed out so I don't know what you've done !

When in doubt start again ......... it's all practice

[multiweb (Marc)]

They're both excellent shots and there's no better or bad processing. I think Eta is like M42. If you're going to take a wide field and show the outer nebulosity you have to stretch the data so "you're allowed to burn the core". I look at the picture as a whole. If I want to see details inside the keyhole area then I do a narrow field of the area and dim the whole surrounding nebulosity.

[[1ponders] (Paul)]

As Fred said you've got some great detail in there and it's nice and sharp. C'mon Mark, you and Adam come out and play. Let's see what your doing with PS.

[batema (Mark)]

Thanks all and Paul we will take you up on that option as Adam told me he has spoken with you. I am happy with both focus and scope set up and believe I have got good data for my set up but YES processing - my mission at the moment.

[gregbradley]

You got the data there in the 2nd shot. The first one is closer to the mark on colour. It does seem a bit red and that is surprising as your camera isn't modified so it must have good red response.

I don't think Eta is that red overall. It has a bit of bluishness to it.

One way to check how you are going with processing is to select an example of the same image from someone's posted image and then
compare yours to it.

Wodaski's "Zone System" book is probably as good as any out there and fairly easy to understand.

There are also excellent tutorial DVDs. One cheap one that is good is Don Wade from Wade Observatory. I think its only about US$30 and has a lot of data on it and is easy to follow. Adam Block's is also good but more expensive.

Probably the area you need to master first is the use of levels/curves. There is an exact way to use them and it makes all the difference as it is your basic processing tool that is done first after darks and flats etc. It sets the scene for the rest of the processing which hopefully will be minor once the levels/curves are done right. If the scene is not set right then later processing will fail. Wodaski gives a very simple and easy to follow approach to that.

In the case of the 2nd image you probably have boosted the highlights too hard and this gives a blown out look and washed out the colours. You can individually adjust the red, green, blue channels with levels and curves.

Another easy way to get good results is to use Noel Carboni's Photoshop actions. These are great value at about US$30 for I think its about 28 actions.

You click on the action (I usually make a duplicate copy first and run the action on that in case I don't like the result) and viola! Its good for increasing star colour (a common weakness in DSLR images are the stars are often shown as all white when they are not), reducing noise, incresing contrast, reducing star sizes, removing violet halos if your scope is semi-APO etc etc. Well worth it.

So in summary, now you have tracking, focus and image acquisition under control you should consider:

1. Getting Wodaski's "Zone System" book.
2. Download the Noel Carboni Photoshop actions.
3. Consider later on getting "Noise Ninja" which is another very handy tool.

Greg.

[TrevorW]

Hi Mark

Had a quick go at the jpeg (hope you don't mind) and this is what I came up with

play with curves, levels and colour balance and you should be able to do a lot better as the data is there

Cheers

[spearo (Frank)]

not bad at all,
if you can get the colors in the second one matching those of the first you'll be right!
well done
frank

[batema (Mark)]

Once again thanks for the advice. I am a secondary school science teacher and my mate and I doing our best to instil a love and facination for astronomy. Your advice will help increase our students level of enjoyment as much as our own.

Mark