Polar alignment Scope

Started 5 months ago | Discussions thread
just Tony
just Tony Senior Member • Posts: 2,164
Re: Polar alignment Scope

Jon Street wrote:

i am realitively new to astronomy. I have a Sky-Watcher 130/900 EQ2

i have modified the OTA to allow for Prime focus, and modified the focuser with a home built autofocuser.

I want to add a Polar Alignment Scope, and yes I know that the mount is not designed to take a scope but that doesn’t stop me from fitting one.

If your fabrication skills are good, this should be within reach.

Using a bracket mounted to the RA axis I am going to mount the scope. Just wanted to find out if anyone else has done this, what scope would you recommend.

The Losmandy polar scope is a total joy. The reticle is cleverly designed to be extremely accurate across a span of time as the Earth's spin axis precesses. Very simple to use. It was still worthwhile to polish the alignment up using the drift technique for hour-long film exposures. I sold the mount before I got into digital cameras but I would expect that the scope alone should get you into the territory of stack-worthy 5 minute exposures, probably longer.

I've surmised that the Astro-Physics polar scope is of similar caliber, and I expect that the same might be true of any of the scopes that have reticles with marks not just for Polaris but also a second reference star.

A really good reticle will also have star alignment markings for the Southern hemisphere.

There are some scopes that have reticles with very simple markings, such as a pair of concentric circles and a series of radial lines. There are phone apps that help walk you through the use of those.

Be sure that any optical polar scope that you buy has an adjustment to get the reticle's center crosshairs precisely coincident with the RA mechanical axis.

There is another option, an electronic one that rapidly helps you complete an excellent accuracy drift mode alignment with few steps: http://www.qhyccd.com/PoleMaster.html You'll need a laptop or notebook PC to run it. There are inexpensive Windows notebooks that use a USB power input, and can run for a huge time interval on it's internal battery plus an external USB power brick.

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