M81 HDR trial

[Mike Hawtin]

It has been ages since I've been able to take an image, all my clear nights seem to have been spoiled by the moon or lost to high winds, in fact a couple of weeks ago we had some extreme winds which actually blew my mount over, thankfully with only minor damage and now, too late I've bolted the darn thing to the deck!

 Anyway, reasonably clear last night with just some passing thin high cloud so I thought I'd have a bash at doing a High Dynamic Range image.  This is the M81 group taken with the HyperStar and Atik 428, 30 x 30 sec and 15 x 300 sec subs, I had to discard 20 300 sec subs due to the cloud so didn't expect much from the image but I was pleasantly surprised to catch a bit of the IFN.  Not too bad for 90 minutes worth of data so I plan to redo this under better condition as a HDR LHaRGB.

Hope you like it

Mike

[gingergeek]

I like it, good work. I must try to get the IFN at some point. What F speed is the hyperstar running at ?

[swag72]

Great IFN there Mike - How did you do the HDR stuff?

[Mike Hawtin]

Thanks Ginger, the scope is F/1.9 geometrically but taking the central obstruction into account the effective focal ratio is F/2.2.

Thanks Sara, I do two stacks and register them then just bung the registered stacks into the HDRComposition tool with the mask smoothness set to 25 and binarizing threshold adjusted to taste, in this case 0.800.  Then it's Histogram Transformation, HDRMultiscale transform set to 5 layers, 1 iteration, scaling function set to Gaussian(5) and the lightness mask checked.  I followed this with one application of the Exponential Transformation tool at default settings and finished with a light S curve with Curves Transformation.  I'm sure there are more effective methods and probably more appropriate tools but I like the results I'm getting this way.

[swag72]

Thanks for that Mike - I thought it was probably PI, it had that sort of look to it!!! I tried the HDR tool once, but it never worked, maybe I'll have another go. Your results sure do suggest that it's a good tool to persevere with.

[Mike Hawtin]

Thanks for that Mike - I thought it was probably PI, it had that sort of look to it!!! I tried the HDR tool once, but it never worked, maybe I'll have another go. Your results sure do suggest that it's a good tool to persevere with. doesn't seem to gain much if anything by using it 

No probs Sara, I don't think HDR suits all subjects though, the 15 Mon image I took immediately before M81 doesn't seem to benefit much from it.

[ollypenrice]

Good going because the IFN is tough. However, it does have the PI HDR look which is a negative for me. I like processing to be invisible and unidentifiable. There is a kind of iron stamp to HDR wavelets which I don't think I'm ever going to like. For all that, you've gone very deep and controlled some tricky dynamic range.

Olly

[Mike Hawtin]

Thanks Olly, the IFN was a bit of a surprise and has encouraged me to go for more subs as my 15 Mon image is hugely smoother with 33 subs, you are right about longer subs, it makes an enormous difference.  I can see your point about the PI's HDRMultiscale Transform  tools effect as well, It's the best I can do at my present level of skill but still has a harsh look to it.  Perhaps an expert PI driver out there can give me some pointers.

Mike