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Kickin' It Old School, 



    
        

            AlenK

Kickin' It Old School

Description

This was my first prime-focus astrophoto setup, shown here ready and waiting for a night of imaging at the Starfest star party near Ayton, Ontario, Canada. (The lens cap was on to keep dust off the corrector plate until it was time to image.) It is based on a Meade MTS-SN6 6-inch f/5 Schmidt-Newtonian telescope, a model introduced in the late 1980's, which I bought used in 1995.

While great for visual use, the telescope needed to be modified to make it suitable for astrophotography. The easiest changes were adding a declination motor and a counterweight bar, both stock items from Meade at the time designed originally for 8-inch SCTs. Some minor modifications were also required to the telescope's beefy 2-inch helical focuser, primarily to prevent flexure from the weight of a 35mm film camera but also to avoid diffraction artifacts from the protrusion of the focusing tube into the optical path with the camera at focus. (I chopped it.)

I also modified the legs of the short, 4-inch diameter pier with a few parts from the hardware store to allow individual height adjustments, which was essential to level the mount as a first step to obtaining polar alignment. Given the solid-steel, 1-inch diameter, RA shaft and the very nature of a fork mount, there is of course no polar-alignment scope. I achieved precise polar alignment using the drift method, which was time consuming but very accurate.

The mount proved to be very stable and the approximate 30 arc-second periodic error in the primitive AC drive was smooth and hence relatively easy to manually guide out using an AC drive corrector while looking through a 12mm illuminated-reticle eyepiece in a Lumicon 2-inch Newtonian Easy-Guider (an OAG) with a 3x relay diagonal. I did exposures up to one hour, which was necessary with film but would be crazy to do today. (Instead, we typically stack many exposures that are much shorter.) When I hear complaints today about autoguiders not working correctly, I feel no sympathy. :)

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Kickin' It Old School, 



    
        

            AlenK