Is a level mount needed to align POLAR SCOPE only
Posted 08 July 2014 - 07:47 AM
Thank you, Kasey
Posted 08 July 2014 - 08:31 AM
Posted 08 July 2014 - 08:46 AM
It does help to have the mount level when polar aligning for a session if you have not touched yet touched the alt adjuster. That makes it easier to get Polaris in the field of view before making he fine adjustments. This assumes you are always setting up at the same latitude, possibly even in the same exact location.
Posted 08 July 2014 - 08:46 AM
For visual usage it doesn't matter. I've kept objects dead centered for hours with a mount that was not level but was accurately polar aligned.
Posted 08 July 2014 - 09:06 AM
Posted 08 July 2014 - 09:10 AM
(1) If it is a rotating polar scope (rolls with the RA axis), it is possible to use it without leveling if, and only if, you can determine the mount's clock angle without using the tripod as a reference (e.g you got the clocking angle from another star). So, possible, but obviously easier if the mount is leveled so you can use the setting circles to get the clocking angle for Polaris.
(2) if the mount has a non-rotating polar alignment scope, like then Astro Physics RAPAS, then it is depending on the polar scope being level left to right to get an accurate fix. Now, I have taken to leveling the RAPAS housing directly, since there is a little bit of slop in the mounting, to get the most reproducible alignment possible.
While it is possible to take various apparent shortcuts, I really don't recommend them. The outcome of every mount alignment short tcu is the same: cut 5-10 minutes off at setup, get running, get the camera going, get it focused, and then start off taking data, shoot several objects, stay up as late as you dare, then take it down and go to bed. When you can, in the next day or so, you take a detailed look at what came out from the rare all-night er of imaging you get to do, and you discover every #£%!ing star in every single frame is slightly egged, and the longest exposures show obvious swirl in the corners; your alignment was just slightly off, and all that effort netted you nothing.
Never take a shortcut in mount setup and alignment.
Level the mount.
Get the most accurate initial alignment you can, either via a polar scope or by putting in good GPS and time data for a GOTO polar routine.
Follow up with a drift alignment. It's the only guaranteed accurate alignment result. I have a 5x Barlow which has no other use than making drift alignment quick.
Posted 08 July 2014 - 09:21 AM
Posted 08 July 2014 - 01:47 PM
Leveling your mount by eye is the most you need to do.
That's true, up to a point. It's absolutely true if you are able to rotate your polar scope reticle to a level position regardless of the mount's level.
If you can rotate your polar scope, simply place your Pole Star close to the horizontal or vertical line, then move either the lat or az adjuster to see if the Pole Star remains parallel to the line. It's a bit easier with the lat adjuster. If not, rotate the polar scope until it remains parallel then position the pole star in the correct position on your reticle...done.
In general, you should always level your platform (mount) as closely as you can, and also your Polar Scope reticle for the most accurate results, and consistent go-tos.
Posted 08 July 2014 - 03:18 PM
Posted 08 July 2014 - 03:40 PM
This is with a CGEM & CG-5, the polar scopes have allen screws for adjustment as you rotate along the AZ axis. you adjust the allen screws to adjust scope alignment,
I'm not really sure what you mean by Az axis? Unless you're referring to the mount's RA axis?
Anyway, this video by Mitch Arsenault is an excellent guide for aligning the polar scope axis to the mount's axis:
This applies to any polar scope with an adjustable reticle.
Posted 08 July 2014 - 04:13 PM
Posted 08 July 2014 - 06:45 PM