The duck Hunt

Guides, tutorials, tips & tricks.
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Joined: Thu Sep 19, 2013 4:07 pm

The duck Hunt

Post by ML7087373 »

So now you’re up to speed here is my response.

I didn’t use binning. I have been concerned about losing detail by doing so. I think my concern was correct. The thing I was incorrect about is that the detail I lose is oversamlping noise, so it’s a good thing. I understand the concept of oversampling but have yet to learn to recognise it visually. Am I correct that the oversampling in my data is caused by the exposure time on the bright subject?
No, that's not how oversampling works.Have a read here to get a better idea of what binning does and what oversampling is. In short, oversampling is recording too many samples (pixels) than are needed to accurately describe the scene. It's all a function of the characteristics of your optics, the recording instrument and the atmospheric conditions (seeing). Recoginising it is fairly easy - if the scene looks like it's got a blur applied to it, your data is oversampled. There are two ways you can then use this oversampling to your advantage; bin the data to make more acurate 'bigger' pixels out of multiple noisier 'smaller' pixels (you lose blur, but not detail), or try to use deconvolution to reverse the blur and increase detail. You can also use a mixture of both.
I didn’t know about using a ROI on a cluster, nor have I ever adjusted the Ignore Fine Detail setting. The IFD made a huge difference.
AutoDev's algorithm is extremely effective at objectively optimising a global stretch evenly to show all detail as best as it can. If fine detail is mostly noise, you can use the IFD setting to have AutoDev ignore such detail and tell it to only optimise for the larger structures/detail in your image.

The Region Of Interest is important if the subject of your image does not cover the whole frame (which is the case here). This way you can tell AutoDev to optimise the global stretch more for that specific area ('more' is subject to the 'Outside ROI' parameter which specifies what contribution the area outside the ROI should still be made to the final optimised stretch).
I think I tried using a ROI in my processing and it made the image too..........something, so I cancelled it and just left everything at default.
It's easy to experiment with what a good ROI is - just keep trying until you've found something that you like. A good ROI includes everything of interest in the proportion that you're interested in, e.g. typically a little bit of background, a lot of primary object 'stuff', an example of a highlight, and example of darker structure. The result will be a stretch optimised for exactly the area that you've given it, all in proportion to the amount of 'examples' of interesting things you've given it. If you give it a lot og background it will mostly optimise for background, if you give it a lot of cluster, it will optimise for a lot of cluster, etc.
I tried Deconvolution, but I did not see a difference in the After/Before, so I cancelled it. Again I did not know what to look for. Also I apparently need to update my version. I have and haven’t found this magical tool "Fat Stars Auto Grow" . It seems like you created that tool for this data. Is it in and I didn’t look hard enough to find it, or is it not there.
Per the processing description I used (which has the 'Decon' preset renamed to 'Fat Stars' to avoid confusion some users had, thinking the preset was only meant for 'Decon' while it is not), and per the processing description I used my own mask because the automatically generated de-ringing mask was too conservative (which is probably why you didn't see a difference). Also per the processing description, what you would be looking for is tightened up (less blurry) stars.
I think the origin of my green stars is my Debayer setting in Nebulosity. I am using settings I got from a friend. There is no other reasoning behind using these settings I have. I am uncomfortable with this, I like to understand the settings I use, but as I have adjusted things in this case I tend to make them worse.That’s another thing to look into. I didn’t use any filters though.
The color balance that ST comes up with indicates that the debayering settings are overall correct (star temperatures seem plausible). The greenish offset wasn't too major. Maybe see if other data suffers from the same quirk...
In your process of my data did you use Scientific Color Style?
Yes. All settings default unless explicitly stated.
How do I save as a JPEG?
Simply provide a .jpg extension whem saving :)
Anything I can do about that big furry star at the bottom right?
You could use Magic to Shrink it, or Heal to remove it completely - the choice is yours :)
Is there a Wiki type page anywhere that describes the visible effect of all of the various settings in the Modules?
As nice as that would be, that's unfortunately not how image processing works - the visuals depend too much on the data set at hand, as well as the settings for a 'this is what it looks like' before and after that is true in all cases.
Anyway, thanks again for continuing to support me and StarTools in general. It's such a great product. I just wish I had more time to collect data to process so I really get to know how to use StarTools. If I can only come up with the winning lottery numbers......
No worries! Here to help (except with those lottery numbers - keeping those to myself... sorry :P)
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Re: The duck Hunt

Post by admin »

Ugh, I'm an idiot. :doh: I edited your post instead of replying to it. Sorry! :oops:
Ivo Jager
StarTools creator and astronomy enthusiast
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