Re: [APML] Autumn Star Trails

[Joe Pedit <pedit@email.unc.edu>]

Stan,

Star trails are only a few pixels wide on typical web-sized images.  It is common to get weird 
artifacts on star trails at web resolutions when the trails are nearly vertical or horizontal. 
The effect is less pronounced on the fatter trails left by bright stars.  My own example of the 
effect is at <http://www.unc.edu/~pedit/polaris_07m.html>.  The bright trails above Polaris in 
my image have the same artifacts that are visible in your first image.

Joe

Stan Richard wrote:

> Chris, thanks.  I scanned at 2700 dpi using Vuescan and saved the raw 
> file as a tif *compressed* so it ended up being about 7Meg instead of 
> the usual 25Meg.  Then I scanned the raw file from disk at full 
> resolution.  This is the first time I've tried this so I wonder if 
> that's what caused the aliasing.  I'll try re-scanning it tonite and 
> save it uncompressed and see what happens.  If anyone else has any 
> ideas, I'd be much obliged.
> 
> 
> Stan Richard
> 
>> From: <cschur@cybertrails.com>
>> Reply-To: astro-photo@seds.org
>> To: <astro-photo@seds.org>
>> Subject: Re: [APML] Autumn Star Trails
>> Date: Thu, 24 Oct 2002 13:50:00 -0700 (MST)
>>
>> Stan, those are really cool images.  The jagged appearance is usually 
>> from
>> scanning the neg at too low of a resolution. Try scanning at about 10 to
>> 20 megabyte size and see if the trails are smooth.
>>
>> Chris Schur
>>
>> > Here are a couple images I took while camping several weekends ago.  
>> The
>> >  stars and planets were so bright and beautiful I couldn't resist the
>> > urge to  try some star trails shots.  I've noticed some aliasing
>> > artifacts in the  trails on the images, anyone else ever have this
>> > problem?  Might be time to  trash the Acer.  Comments welcome.
>> >
>> > http://nightskyevents.com/AutumnTrails101102.html
>> >
>> > http://nightskyevents.com/AutumnTrails101302.html
>> >
>> >
>> >
>> > Stan Richard



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