Where is the `stretch` button please?

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Gasman
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Joined: Wed Jan 30, 2013 12:05 pm

Where is the `stretch` button please?

Post by Gasman »

Hi
Just working through Star Tools tutorial 1 and it mentions on page 6 clicking on the `stretch` button but can`t find it on screen is it called something else now as the tut is dated Feb 2012?. I`ve opened a lum,red,green and blue fits which look out of alignment but not sure how/where to proceed next?
Thanks
Steve
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Re: Where is the `stretch` button please?

Post by admin »

Gasman wrote:Hi
Just working through Star Tools tutorial 1 and it mentions on page 6 clicking on the `stretch` button but can`t find it on screen is it called something else now as the tut is dated Feb 2012?. I`ve opened a lum,red,green and blue fits which look out of alignment but not sure how/where to proceed next?
Thanks
Steve
Hi Steve,

The tutorial you're using is for 1.2 (if you look in the download section it says 'obsolete').
Screen stretching is obsolete as of version 1.3.
As of version 1.3, the difference between linear (for which screen stretching is needed) and non-linear data has been abstracted away; all operations now *appear* non-linear, but some are, in fact, performed on linear versions of the data in the background. StarTools accomplishes that by 'going back in time' while your data was still linear, applying the operation to that version of the data, then calculating how the result would have looked after all the steps you performed after you decided to apply the linear step; it's akin to time travel where you change the past in order to change the future.

What this means for you is that you don't have to worry about keeping your data linear for, for example, deconvolution - you can now apply mathematically correct deconvolution any time, for example after stretching, HDR optimisation, Wavelet Sharpening, etc.) - it will still work! StarTools will calculate the result for you as if you performed deconvolution before you applied stretching, HDR optimisation, Wavelet Sharpening, etc. Neat hey? It's ultimate freedom! And not to mention much more user friendly... :)

The same is true for global stretching (using either the AutoDev or Develop modules) - you will notice that if you launch these modules a second time, they will actually ask you if you want to 'go back in time' and redo your global stretch. This is why screen stretching is now gone - you actually get to experience stretching your data for real, but still have the chance to change your mind or apply steps that traditionally require linear data.

For more information on how StarTools is different from traditional/classic applications such as Photoshop, PixInsight, etc., have a look here.

Cheers,
Ivo Jager
StarTools creator and astronomy enthusiast
Gasman
Posts: 25
Joined: Wed Jan 30, 2013 12:05 pm

Re: Where is the `stretch` button please?

Post by Gasman »

Thanks for the reply Ivo ;) . I suppose what I`m looking for is a sort of up to date Dummies guide to Startools !. For instance if I open a fits image say of M42 I`m faced with an option of maybe 14 to 15 choices in the left hand side of the screen and I`m uncertain which to try first. Maybe I should try processing a bit differently to using PS for instance where you try one filter then the next and so on.
I understand Startools only allows the choices available at the time but you still have quite a few to choose from. Maybe its a process of trial and error to see which way suits the individual best but a step by step guide (and why those particular steps are chosen) would be ideal as I`m quite a novice at imaging anyway. I keep watching the vids and I see the end result but its not clear (to me at least :think: ) how you arrive at that.
Maybe its an age thing :P I`d have no hesitation at all buying a licence if I could suss out how to use ST. I`ve just loaded a luminance,a red,a green and a blue fits of M42 and noticed the blue a little out of alignment but I`m not sure if ST allows frame alignment??
Best
Steve
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Re: Where is the `stretch` button please?

Post by admin »

Gasman wrote:Thanks for the reply Ivo ;) . I suppose what I`m looking for is a sort of up to date Dummies guide to Startools !. For instance if I open a fits image say of M42 I`m faced with an option of maybe 14 to 15 choices in the left hand side of the screen and I`m uncertain which to try first. Maybe I should try processing a bit differently to using PS for instance where you try one filter then the next and so on.
I understand Startools only allows the choices available at the time but you still have quite a few to choose from. Maybe its a process of trial and error to see which way suits the individual best but a step by step guide (and why those particular steps are chosen) would be ideal as I`m quite a novice at imaging anyway. I keep watching the vids and I see the end result but its not clear (to me at least :think: ) how you arrive at that.
Maybe its an age thing :P I`d have no hesitation at all buying a licence if I could suss out how to use ST. I`ve just loaded a luminance,a red,a green and a blue fits of M42 and noticed the blue a little out of alignment but I`m not sure if ST allows frame alignment??
Best
Steve
I understand Steve. The flow in the video tutorials is pretty much the same for any sort of data, if it is 'good' data - i.e. properly calibrated with dark/bias and flat frames.

Here is what each step accomplishes (and why);
  • Load your image and switch Tracking on; tracking in StarTools allows you to redo things as described above, while also tracking noise levels for each pixel of your image.
  • First (global) stretch (using Develop or AutoDev); see what you have, what your data looks like and if there are any defects that need addressing (stacking artefacts for example).
  • Address defects; use Crop to remove stacking artefacts, or Bin to convert resolution into signal fidelity if very noisy.
  • Remove gradients and/or light pollution (Wipe)
  • Redo (global) stretch (using Develop or AutoDev); now that all defects are gone, your first global stretch can more accurately bring out details globally.
Mix and match these as you see fit;
  • Local stretch (using Contrast and HDR); these stretch your image locally (i.e. depending on local characteristics in your image), so that detail in those areas becomes better visible, without adversely affecting detail outside that area.
  • Wavelet Sharpening; enhance detail globally by bringing out detail of a specific size.
  • Deconvolution; reverse any blur in your image that was caused by bad seeing conditions.
When you're done using the available modules in Tracking mode, switch Tracking off. This will let you perform final noise reduction that is tailored exactly to how you processed your data.

From here, it's all up to individual taste.

If your data is not properly calibrated or suffers from other acquisition related problems, StarTools totally equipped to assist, but the way to proceed will deviate from this generic flow.

Would you perhaps be able to share your data with me?
Ivo Jager
StarTools creator and astronomy enthusiast
Gasman
Posts: 25
Joined: Wed Jan 30, 2013 12:05 pm

Re: Where is the `stretch` button please?

Post by Gasman »

Excellent Ivo cheers for that, just what I was looking for :D . Thanks for the quick reply :bow-yellow:
Steve
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Re: Where is the `stretch` button please?

Post by admin »

No problem - here to help! :thumbsup:
Ivo Jager
StarTools creator and astronomy enthusiast
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