M17 and M5

[Jeffkop (Jeff)]

Hi all

Yep, was out again last night until 2.00 ish. Decided to experiment with exposure times on clusters and nebula's. Its pretty hard to get it right isnt it.

I tried not to over expose the cluster. Every time I have tried to image one of these its turned out like a cool mint thats been smashed with a hammer. So I took a series of different exposures. Its really hard to tell exactly what youve got when you take them and you dont want to waste time playing with them right then, there are other things to image.
So this is a 3 minute one L3 RGB3 and I still have a scrambled core. The other shorter exposures didnt really cut it, and even they had scrambled cores.
So this one worked sort of, shame about the bloated star in the corner of the shot and the noise , but I fear I just dont have enough signal in the exposure and to see any of it reasonably means I have to adjust the levels and then comes the noise and the bloat of the star. So perhaps another series of shots the same exposure length stacked will do the trick?

The nebula, I have tried not to clip the black as has been mentioned in past pictures. This one suffers from a lack of detail and so a longer exposure is necessary, but there are some bright stars in there and I think longer may bloat them. This one is L20 RGB15. Would you suggest the same again and then combine the images?


Thanks for your help

Jeff

[jase (Jason)]

Hi Jeff,
Good analogy regarding Globular and cool mints. Imaging globular clusters, you need good seeing. Globular clusters don't handle sharpening very well. That's been my experience anyway. Pleasing to see you've got over the black clipping hurdle in this recent batch of images. While you are probably keen to image as much as possible, may I suggest you sit on a target a night. Collect as much data as technically possible. These two images scream for more data. Take 5-10min subs and heaps of them to start with. As you get your polar alignment sorted, go longer (providing your environmental conditions and equipment will permit it).
A quick way of testing your data quality is a digital development stretch. If you've got inherent noise in the combined subset, you'll probably need more data or calibration wasn't effective. You can tighten up stars which are bloated using deconvolution (to a point). You're on the right track, just focus on a single target and collect as much data as possible. The more data you have to work with, generally the easier the image will become to process. Dealing with noise is never a pleasurable experience. Look forward to more as you progress.

[Jeffkop (Jeff)]

Originally Posted by jase

may I suggest you sit on a target a night. Collect as much data as technically possible. These two images scream for more data. Take 5-10min subs and heaps of them to start with. As you get your polar alignment sorted, go longer (providing your environmental conditions and equipment will permit it).

Thanks for the reply and the great information Jase. I hear you and as much as possible I try to stick to a target. The location of these objects at the moment means I don't have the luxury of being able to image anything until its at a high dec because of the house. After they come over the house roof (2 story) I have about 1 hr before problems with the camera and the mount tripod legs come into the equation and if Im to stay on the same target I have to wait until I can do a meridian flip to continue. Then I have about another 1 1/2 hrs and the trees at the back interrupt the viewing. So I decide what I want to look at and so spend time imaging what I can until the trees get in the road and then I swap to something new coming over, and repeat the process.

My greatest area of uninterrupted sky is to the North and from about about 40 degrees of the horizon, but you'd be amazed how little there is to image in this area. Much more straight over head and also to the south.

Im going to build a 2 story observatory in the future to give me a much more open view to everywhere, but that is at least 6 months away.

Thanks once again for your advise, its great

Jeff