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Re: [APML] Im Blue

----- Original Message -----
From: Siegfried
 
(snip)
>I have been trying out the Fuji Super 800 film the last couple sessions, 
 
Do you mean Superia instead of Super? The newer versions of the Fuji Superia line of films have completely lost their sensitivity to red emission nebula in the most recent formulations, but have stronger greens and blues. It is possible to get a decent galaxy pic with Superia though, but overall the newest stuff is a lousy astro film. The older Fuji color neg stuff was among the best. Your image looks like it was shot with the newer film.
 
(snip)
Must the color curves be manipulated when scanning, is this the proper technique?
 
Yes. The black points must be set for each color channel. This can be done in either LEVELS or CURVES in Adobe Photoshop. For an explanation:
 
http://www.aa6g.org/Astronomy/Articles/levels.html
 
and
 
http://www.astropix.com/HTML/J_DIGIT/DIGTECHS.HTM
 
Hope this helps.
 
John Boudreau
jeboud@mediaone.net
http://people.ne.mediaone.net/jeboud/astro.htm
----- Original Message -----
From: Siegfried
Sent: Tuesday, September 25, 2001 11:45 AM
Subject: [APML] Im Blue

After processing some images from the other night, they all turned out to have a very blue/violet shift.
 
Now let me just say that the humidity was 100% (at least, heh)...I am aware that humidity will affect film, and have ordered all the parts for a gas purge system.
 
I have been trying out the Fuji Super 800 film the last couple sessions, and have been generally pleased with it cause it picks up stuff fast, I like that because im still new to all this. But these images are far more "blue" then any other I have taken, so i'm left kinda wondering what happened. The entire roll of film, which includes some planetary exposures under 2 seconds is the same - a blue tint everywhere (when scanned, prints are ok). I should also note that this was my 1st attempt at exposures over 1/2 hr.
 
 
I have my negative film processed at a lab...so I'm wondering if this a result of bad film, processing, scanning (the prints came out looking ok).
 
On another note, after looking at the scanned images in PhotoShop it seems the blue channel contains all the "sky fog / film grain" (however badly discolored it is), so I'm thinking that this layer of the film is more susceptible to the extreme humidities...is this possible? But this doesn't explain why the short exposures are blue also. When I rescanned the images and adjusted the curves so as not to pick up so much blue the situation improves, but I'm left feeling something weird was going on here. Must the color curves be manipulated when scanning, is this the proper technique?
 
Also let me just say thanks to those who started the thread about the STV and tweaking the settings so as not to "chase the seeing", the guiding tolerances with my Gt1 have improved dramatically.