From: Milton Aupperle <milton@outcastsoft.com>

Date: April 4, 2012 10:23:04 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Mars APril 2 2012 (sort of)


Hi Ray;


The magnification is controlled by distance from the Barlow lens to the CCD. So you add your extension tube in between the CCD and barlow.


The same principle works with Focal Reducers too - the further back you are from the FR Glass, the more it reduces.


That's why a lot of people actually have no idea what their true magnification is when they use them. If they add in a filter wheel or some adapters etc, they have changed the magnification.


I always measure the distance between some known stars at the Prime Focus, and then with the barlow or FR in place. Then you know the true focal length and how much the Barlow / FR is affecting things


TTYL..


Milton Aupperle


On 4-Apr-12, at 4:25 AM, Ray Byrne wrote:




Hi Milton,


Thanks for the info. A question - does the barlow element increase its magnification by being further from the focal plane of the telescope or further from the camera chip?


TIA


Ray