Re: [APML] 2 new images

[Brian larmay <power_windows4789@yahoo.com>]

Wow..

Great set of images!

Ive been looking for Konica around here after a
referal and found a few stores that carry it
fortunaley.
Your Wide 4 exposure of Cygnus is also quite amazing
with the 400.

Is this a new film?, or just a newly discovered film
for astro work?

Incredible as always,
Brian



> ALOHA,
> 
> I processed two of my new images taken this month. 
> (Others will take 
> long long time to process.)
> 
> The first one is Subaru Deep Field:
>
http://www.ifa.hawaii.edu/~wang/gallery/picutres/subaru_deep_field.htm
> 
> This one made use of my new flat field technique. 
> Despite the new 
> technique, there is still difficulty in the image
> processing.  The 
> main problem is sky gradient.  In the unprocessed
> image, the sky
> gradient and the vignetting pattern are mixed. I
> cannot find a
> unique solution to decouple these two (perhaps I
> didn't try hard 
> enough).  Therefore, both flat fielding and gradient
> removal are not 
> perfect.  I did a lot "twist" in PhotoShop to
> correct these effects.
> 
> For this reason, I don't trust any brightness change
> in this image 
> that is larger than ~30% of the image size (i.e.,
> large nebulas).  
> They may be just remnant of the imperfect sky
> gradient and vignetting 
> removal.  For small-scale brightness changes smaller
> than ~25% of the 
> image size (small nebulas), I'm pretty sure they are
> real and are not 
> artifacts.
> 
> 
> IC2177:
>
http://www.ifa.hawaii.edu/~wang/gallery/picutres/I2177-2004.htm
> 
> The new flat field technique failed on this one. 
> The vignetting 
> is corrected using my old method that assumes
> axisymmetry for the 
> vignetting pattern.  The reason why flat fielding
> failed is unclear.
> There seems to be some strange scattered light in
> all the 3 stacked
> images, which doesn't appear in the flat field
> shots.  Perhaps 
> such scattered light is caused by the 1.4x rear
> converter.  This
> rear converter is designed for Pentax 67 lenses but
> not for the 
> telescoep.  (The one for my telescope is
> discontinued.)  And because
> of this scattered light, my old method doesn't work
> well, either.
> Again, I did lot of manual twist in PhotoShop to
> remove the leftover.
> 
> Centuria 800 is quite grainy, comparing to Centuria
> 400.  Of course,
> one hour at F9.4 is too under exposed.  This is part
> of the reason why 
> it's grainy.  Although I stacked three images, the
> stacked image still 
> looks grainy, and noisy.  Surprisingly, stars are
> extremely sharp and 
> have well-defined shape.  (Centuria 400 also
> produces very sharp stars.)  
> The finest stars on the film have diameters about 40
> micron, as small 
> as I measured on E100S.  Unfortunately, I have to do
> some smoothing in 
> PhotoShop to remove the grains.  This slightly
> demaged the resolution 
> of the image.  I may take 3 or 4 more 1-hr exposures
> next year to 
> improve the S/N so I don't need to smooth the grains
> and can keep the 
> very sharp stars.
> 
> Any comments are welcome.
> 
> Wei-Hao
> 
>
______________________________________________________________________
> Wei-Hao Wang  :)
> 
> Institute for Astronomy at University of Hawaii
> 
> Address:                       Phone: 808-956-9867  
>                
> 2680 Woodlawn Drive            Personal Website:
> Honolulu, HI 96822            
> http://www.ifa.hawaii.edu/~wang
>
______________________________________________________________________
> 
> 
> 
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