M13 Experiment

[centroid]

With the full Moon blazing away last night, conditions weren't suitable for anything serious in the way of DSO'ing, so I 'grabbed' a few subs of M13 to process experiment with.

The 30 subs weren't that good, so neither of the resulting images are particularly good quality either. However, they do show the effects of the two different processes nicely.

The subs were de-bayered and stacked in AA4, to produce a 'master' image. Taking two copies of the 'master', one was left 'as is', while the other was subjected to DDP filtering in AA4. Both images were then saved a 16 bit TIFFs, and imported into P'Shop, for final 'tweaking'.

The two pictures below, show the DDP version and the non DDP version. For me personally, I think the non version DDP is the better result, and have decided that I'll not apply DDP filtering to Globular Cluster images.

DDP is a powerful 'tool', that often works very well on Galaxies with very bright cores, but not so with Globular Clusters it would seem.

12" LX200R at f/7 and 30x20 sec subs with the SXVF-H9C

Dave

[MikeP]

Dave,

Could you tell me what DDP is and what effect it is supposed to have on an image. Please pardon my ignorance.

Mike

[CELESCOPE]

well Hmmm for me the top one is the best with better star separation, so still not sure what way around they are , but looking at it the top must be ddp , hey Dave if it is , i have to disagree , top one for me . ehheheh

Rog

[Ant]

Personally I think the second is far more aesthetically pleasing to the eye!

Second one gets my vote!

Ant

[zhgutas]

Ditto fro me too, Ant. the second one looks much more fluffy IMO, that's what glob should look like

Marius

[George]

I'll go with Rog, 1st has more depth of field than the second and looks more natural

[LostNSpace]

Nice M13 Dave.....It has to be the 1st image for me though.....I suppose we all have to try different things when it comes to processing or we will not learn anything at all.......At the end of the day as there are so many ways of extracting data out of your images that the final result is down to personal preferance. It would be quite boring if all uploaded images of the same object were processed the same way and looked the same.......

Mark

Dave,

Could you tell me what DDP is and what effect it is supposed to have on an image. Please pardon my ignorance.

Mike

Mike - DDP = Digital development process - Its a tool used to simulate conventional film characteristics in CCD images.

Unlike conventional film CCD cameras have a linear response to light.

When you start processing your CCD images and tweak the brightness and contrast to see dim objects you end up saturating the bright objects, but at the same time if bright objects are not saturated the dim ones disappear.

Using DDP you digitally simulate conventional film. The S Shaped characteristic curve of the conventional film is applied to the image instead of the normal straight line curve allowing you to enhance the dim objects without saturating the brighter ones.

Hope this helps

Mark

[jcm]

DDP is a very useful tool if your object has been rather burnt out in the centre. This often happens with globular clusters (and some galaxies). You have to apply it with care or the result can become very unnatural. I believe it works by reducing the range of brightness across the image. No doubt a "google" will give the correct explanation

John

PS or Mark's post above

[centroid]

Ok,

Rog, the second one is the DDP version (see m13_30x20sec_ddp_19 5 08 at the bottom of the image)

Mike, I see that Mark has answered your question admirably, so nothing to add there.

John, your description of the DDP process, is as I understand it too.

Astro imaging processing is, to quite a degree, a matter of personal preference as Mark rightly says. I guess its a balance between being what we believe is the more scientifically correct, and what is most pleasing to the eye.

Certainly Globular Cluster are very aged objects, and as such, comprised of old yellowing stars, so the grey/white, as most of us portray our 'glob' images, is most likely scientifically incorrect, and a distinct yellow tinge would likely be a more accurate representation.

In fact in the non-ddp image, there are quite a few old yellow stars showing up.

Anyway, I thought I'd share these results with you, and thanks for your comments. Just what the forum is all about!!.

Dave

[Cloudwatcher]

That was a very interesting and informative thread,Dave. Just goes to show how individual we are in our perception.

Both images are splendid in their own way and I thought perhaps a combination of the two would be even splendider more splendid. Might have worked too if I'd got the alignment right!

Cheer

CW

Click as usual.

[zhgutas]

Good idea CW And an interestingly nice result!

Marius

[Sam]

Very nice shots and interesting discussion on the processing.

[centroid]

An interesting concept CW, and yes it could indeed work. Maybe then pleasing to the eye of those who like neither the DDP or non DDP image.

Dave

[Tim]

i have also enjoyed this thread, there should be more stuff like this!!!

TJ