Resolving cores of galaxies

[NickK]

I'm thinking again.. hot on the heals of redshift vs Ha, M42 trap E&F..I, it's how to really resolve the cores of galaxies. I think a lot of this is going to be shared..

Obviously we're talking resolving what is a really bright DSO object compared to the surrounding area. Minor signal variations is what I'm after so noise reduction is high on the list.. however are there any techniques to this during capture?

Cutting out and treating the core separately with lower exposure times to prevent burnout.. also are filters such as Ha 3nm better for assisting the finer details?

I'm assuming that the higher energy output would mean that narrowband on the core would return some better results but I'm also thinking that would the narrow band required would be on the higher energy levels as the core of galaxies are an energy hot spot.

Any thoughts/pointers?

[ollypenrice]

I think you'll find that narrowband on the cores gives very little. In fact the Ha information you get for galaxies is entirely different from that which you get for emission nebulae. On nebulae it contains exquisite structural detail and high contrast. I process it for sharpness. On galaxies you generally get formless blobs indicating the H11 regions. There is nothing to sharpen, the layer will just give red patches where the star formation is occurring. Exceptions are the nice Ha jets you see in M106, M82 etc.

I've tried short subs on a few galaxies, as have others I've spoken to, and we've all found them useless in the end. The same applies to Alnitak. I think what happens is that you avoid blowing the hotspots but you don't get any of the fainter signal away from those hotspots. When you try to layer them in you end up with the hotspot better controlled but then a sort of 'information hole' around it.

I was able to resolve Alntak into a double using full length subs (with caveat to follow) and a certain amount of convincing data around it. This was the difference.

The caveat is to use RGB only on your hotspots. It burns out less easily. My method is to make an RGB and an LRGB and then do a soft stretch of the RGB only, the idea being to get the dark regions as bright as possible (to match the real LRGB image) but keeping the bright stuff down. For this the curve obviously has to rise steeply at the bottom but then flatten off very early. This won't look good as a pic in its own right but if you have some faint data and a controlled hotspot you have what you need to layer into the LRGB.

Olly

[NickK]

What would be interesting is if you could use a narrowband with a low bandwidth (i.e. 3nm) to observe differences in the core - just finding which optical spectra (rather than radio/UV/IR) is going to be better and if it's possible to do anything with it. From my previous Ha calculations it would be possible to just start seeing velocity differences with 3/4nm Ha compared to standard 13nm bandwidth Ha for example.

Reading up there's obviously more energy released, RGB is a good way of reducing the output. Just thinking if there's anything that narrow band can do to enhance the (based on the core rotation speeds etc). I'll try the RGB

It would be interesting to see if it's possible for some amateur photography to show some science occurring. The upside is more control over the brighter DSOs (especially those with mechanical shutters).