Re: [ATM] Using Barlow to reduce Coma

["Jean-Guy Moreau" <jgmoreau@cablevision.qc.ca>]

While we are on this subject, and taking a practical example
that applies to my present situation :

For a given CCD size, 
will there be more, the same, or less coma at the edges of the image if
i replace my 10" f/4 with a 20" f/4 ?


Jean-Guy


----- Original Message ----- 
From: "Richard F.L.R. Snashall" <rflrs@rcn.com>
To: "'AMT LIST'" <atm@atmlist.net>
Sent: Wednesday, January 25, 2006 4:04 PM
Subject: Re: [ATM] Using Barlow to reduce Coma


> Mark wrote:
> 
>>O.K., so if I were to pop in a 40mm plossl, then coma would look
>>as bad with and without the Barlow?
>>
>>My common sense tells me that as I am only looking at half the field with 
>>the barlow in, so
>>it would be like looking at the centre area without the barlow -  which has 
>>less coma!
>>
> If coma were linear with field angle (i.e.: half the field would
> have half the coma), but the field were magnified twice as much
> (2x Barlow), there would be no gain, would there?
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
>
_______________________________________________
ATM mailing list http://www.atmlist.net/