Re: dob tube length vis a vis CMOS imagers
¿ªÔÆÌåÓýMike, ? When a focal reducer is used with a camera or an eyepiece, the effect is moving the focal plane inward toward the secondary.? All shortening the truss poles does is push the focal plane further out the focuser.? The focal length of the system stays the same.? This can result in part of the light cone from the primary not being captured by the secondary.? As some have mentioned, a larger secondary may be needed to more fully illuminate the FOV when the truss poles are shortened. ? Yours truly, ? Jack ? Jack Huerkamp Jack's Astro Accessories, LLC 38388 Pine Street Pearl River, LA 70452-5192 985-445-5063 30.37N? 89.76W ? All of us get lost in the darkness. ¡¡¡¡¡¡¡¡¡¡¡¡¡.Neil Peart ? ? ? From: [email protected] <[email protected]> On Behalf Of Michael Dreis via groups.io
Sent: Monday, May 13, 2024 9:06 AM To: [email protected] Subject: Re: [ServoCAT] dob tube length vis a vis CMOS imagers ? Gary, ? Can you shorten the tube length?? The purpose of the truss system is to hold the secondary mirror at the correct focal length away from the primary mirror.? Seems to me if the focal length is 1524mm (60 inches), that it has to stay at that length.? Am i missing something? Mike Dreis ? ? On Mon, May 13, 2024 at 9:03?AM K9RX - Gary via <amateurK9RX=[email protected]> wrote:
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Jack Huerkamp