Re: [APML] Cats paw on the tail of the scorpion

[Ray Butler <ray.butler@nuigalway.ie>]

Hi Len,

>It was the noise removal step that affected it the most.  Here is another
>version.  Not as aggressive on the noise.
>
>http://home.houston.rr.com/lencasady/catspaw01.jpg
>
>  
>
I'd agree with Stuart - the revised version is much more punchy. Maybe 
the noise reduction "pros" outweighed the "cons" in the high resolution 
version of the image, but in this 809x539 pixel version, it's definitely 
better with less aggressive denoising.

>I think the shot was at F/3.3, which is wide open.
>  
>
OK, that would explain the mild chromatics - no fancy ED/FL glass in 
those traditional telephotos. Seems to be a good flat-field lens wide 
open, though - the corners are as sharp as the centre.

Ray "whose lenses all have 'traditional' glass - with the recent 
exception of an ED80 telescope which hasn't been imaged through yet" Butler


>Len
>
>-----Original Message-----
>From: astro-photo-bounces@seds.org [mailto:astro-photo-bounces@seds.org] On
>Behalf Of Ray Butler
>Sent: Friday, March 04, 2005 11:00 AM
>To: Discussion of Film Astrophotography
>Subject: Re: [APML] Cats paw on the tail of the scorpion
>
>
>
>Hi Len,
>
>The colours look fine on my screen (set to 9300K colour temperature). No sign of
>residual vignetting. Can't see any obvious trailing, but the image scale is
>small in that 
>jpeg, so that helps to hide it.
>It does look a bit soft. Hard to tell why, as some jpeg compressors can 
>have this effect too. Was it more apparent after your noise removal step? There
>are clear bluish chromatic halos around stars - so I presume the 
>200mm lens was at full aperture; would that be f4?
>Overall, a very nice result!
>
>Ray
>
>  
>
>>With all the bad weather here in South Texas lately, the only thing to 
>>do is processing.  Of which I need lots of practice.  Thought I try 
>>fooling around with some of my not so well tracked or guided shots.
>>
>>I shot this two years ago at TSP.  This was my first shot with a lens 
>>    
>>
>>>50mm.  I was excited when I first looked at the scan at the lab 
>>>      
>>>
>>without a loupe.  But, when I got home the scan showed some trailing.  
>>I think it was guiding and not field rotation as the elongation of the 
>>stars appeared East-West and linear on the top and bottom of the frame.
>>
>>Just a few details as I would have to find the old logbook... OM1, 
>>200mm, E200, piggybacked on an LX200 w/ wedge.
>>
>>http://home.houston.rr.com/lencasady/catspaw.jpg
>>
>>There was also some very obvious vingetting and noise I tried to 
>>remove.  Does it look way too soft?
>>
>>How are the colors?  On this note, I found that my colors looked 
>>different at home than they did when viewing from work.  Found that the 
>>Nvidia video driver had a setting for "Digital Vibrance" turned on.  I 
>>think it basically ups the saturation and brightness of the screen.  
>>Turned it off and then processed.
>>
>>Comments?
>>
>>Thanks
>>Len
>>
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>> 
>>
>>    
>>
>
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-- 
Dr. Ray Butler
Lecturer, Physics & Astronomy | Physics Department | Computational Astrophysics Laboratory
National University of Ireland - Galway, University Road, Galway, Ireland | www.nuigalway.ie
ray.butler-AT-nuigalway.ie | Tel: +353-91-524411 ext 3788  | FAX: +353-91-750584

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