http://celestialwonders.com/articles/lunarmosaic


At 12:45 24/11/2003 -0500, you wrote:
>Hi Juan,
>
>I am enjoying your mosaic very much.  The detail along the terminator
>is striking!  At your focal length you are resolving some features I
>don't get with my C8. The First Quarter has some very interesting
>features.  I guess I have an affinity for high resolution mosaics like
>this, and I suppose it's kind of becoming my specialty :-)
>
>If you're interested, I've just finished an article on the technique I
>use to construct lunar mosaics.  I have hopes of getting this
>published<g>. Your mosaic demonstrates a couple of the hardest parts:
>hiding the seams and normalizing the histograms.  My article discusses
>both of these in some detail.  Since you are using Photoshop to put the
>mosaic together, the article may be of some benefit. I use a CCD camera
>and calibrate/normalize the FITs files before saving as TIFF format,
>but I'd like to try this with a webcam (and film <g>) as I know many
>lunar imagers use these mediums. Anyhoo, the article can be found at:
>http://celestialwonders.com/articles/lunarmosaic
>
>I've never tried a color mosaic and I think you have done a marvelous
>job (and 50 sub images is alot of work)!  The only thing I might
>recommend is a curves adjustment to enhance the constrast in the
>midtones. Please don't hesitate to post your next attempt!  BTW, I
>would kill for 8/10 seeing!
>
>Thanks,  Frank
>http://celestialwonders.com




Hi Frank,

Thank you very much.

Your article is excellent. The information given is great and very helpful.
Thanks for sharing.

When I get some more time, I probably will reconstruct the whole mosaic
from scratch. Then I'll test some of your procedures, especially the eraser
trick to avoid the seams.

After your advice about contrast and some other suggestions received, I
have managed to reprocess the mosaic image. Here is the result (1.9 MB, but
it's worth the bandwith waste):

http://astrosurf.com/pleiades-ap/20030409/mosaic-L-curves-atw.3000.jpg

This is the result of:
1. Adjusting a bit some transitions between subimages to reduce brightness
differences
2. A careful (and difficult) curves adjustment for better overall contrast 3. Boosting wavelet processing / noise reduction to the limit

I have done 1 in Photoshop, and 2,3 in our PixInsight. The amount of detail
is so high this time, that usual bicubic interpolation resampling does not
convince me to preserve sharpness. I have used a high performance bicubic
spline interpolation algorithm to reduce the image, and quality 12 jpeg
compression to prevent detail losses and artifacts.

I have decided to desist of making a color lunar mosaic for now. I'm not
happy with achieved color consistency --- not an easy work that needs much
more accurate proceedings.

Please look with a blind eye to the multiple seams and mosaicing
artifacts... hope to do better next time.

Best regards,
Juan Conejero.