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Blending data from two different scopes

Bruce Donzanti
in PixInsight
Is there a specific approach or recipe available on how to blend data from the same object from two different scope focal lengths (e.g., C11" SCT at 2800 and an 80mm refractor at 480)?

I know some folks use Photoshop for this but I am not aware which program would do it best.

Thx
Bruce

Comments

  • BlockHeadBlockHead
    Hi Bruce,

    There are two tricky parts of combining this kind of data. The first hurdle is usually aligning the images. SInce they will have different FOVs and different faint limits (numbers of stars)- this can make using StarAligment a challenge to get everything to register. Cropping the larger FOV to the same size as the more zoomed in smaller FOV usually helps (in your case, you can use this as a reference). The other part is weighting the images correctly. You might want to simply substitute the high-resolution information into the lower resolution image. In this case the weights do not matter. As it happens I am combining images from different setups...but I literally want to integrate everything- so weighting is important.

    -the Blockhead
  • Bruce Donzanti
    Hi Adam

    Thanks a bunch for the tips and advice.  I'll give it a go and see how it turns out.  I suspect I will have a learning curve here like with most new things.

    I realize you are busy, but maybe one day you can make a video demonstrating this.

    Thanks again,

    Bruce
  • BlockHeadBlockHead
    Currently I am dealing with a nuance that gets into the weeds.
    I have data from two different telescopes... and you cannot simply combine them and get the weighting correct. This is because PixInsight will measure the noise...but not take into account the difference in plate scale (solid angle on the sky). Each might be observing the same number of photons...but because the light is spread out more in one compared to the other... this needs to be accounted for... BECAUSE when you register the images this measure is *not* accounted for (you are effectively matching the plate scale).

    -the BLockhead
  • Bruce Donzanti
    ok- got it- 

    To your points about using PI, would Photoshop be a better (i.e., easier option) to attempt this or is the selection of software irrelevant since the issue of light spread still exists?  I ask this because I have seen examples of images where the author states they used Photoshop but I have no idea how they did it.
  • BlockHeadBlockHead
    You can arbitrarily combine images (even in Pixinsight) easily. The point is to blend them in such a way that each is given the *proper contribution* based on the amount of signal and noise. This is mathematical distinction. 

    I am describing two different situations. In my case I am talking about combining, that is averaging, information from two different telescopes. You I think are consider simply "pasting" (for lack of a better word) one image over another correct? In your case you need only align the images (you can do this in PixInsight- Dynamic StarALignment) and get the match the intensity and background (you can do this  Pixinsight, LinearFit). 

    -the Blockhead
  • Bruce Donzanti
    No- I am talking about what you are doing- i.e., averaging info from two different scopes. Sorry if I was not clear.
  • BlockHeadBlockHead
    OK. That aspect is not possible in Photoshop.
    -the Blockhead
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