polar alignment vis-a-vis dec axis w/ no drive
Posted 01 May 2011 - 09:31 AM
Thanks in advance.
Posted 01 May 2011 - 03:21 PM
Posted 01 May 2011 - 05:43 PM
Sorry for these noob questions, this is just the first time I have really used one of these type of mounts before.
Posted 01 May 2011 - 10:49 PM
Posted 02 May 2011 - 08:41 AM
Drift Alignment is used to tweak a mount into final, perfect polar alighment. I will include a link to the instructions.
Before you read it though, let me first say this. For general observing, where you just want tracking, it is not at all important to have perfect polar alignment.
Most of the time, if your aligbment is even pretty close, and if you aren't doing observing at 250x or more, the amout of drift typically just isn't enough to worry about because you may not find yourself looking at objects long enough for them to drift from the field.
If you are imaging and doing long exosures, then drift alignment is much more important.
So, the question would be "Do you really NEED to drift align for general observing?" The answer might be "No".
I use Go-To scopes and if the alignment is not pretty close, I get drift (most Go-To scopes don't track in Dec, so if your alignment is not perfect, the target will drift out of the field), but honestly, even when doing planetary oberving, it is rarely a problem (though I do try to do a decent rough alignment). For most deep sky observing it is NEVER a problem unless I leave the mount unattended for a while and the target disappears totally from the field.
Anyway, here are the instructions for drift alignment. DO this and your problem will be solved...
Posted 02 May 2011 - 09:36 AM
In terms of where the alignment is now, using a 15mm Axiom. Saturn takes about 20-minutes to drift out of the FOV entirely, so I am close but I'd like to nail this. I'll look at the drift site, thanks again!
Posted 02 May 2011 - 10:05 AM
I don't remember seeing anyone mentioning a polar scope. Does your mount have a PS or can be fitted for one?
If you use a Polar Scope (PS) then remember, it is NOT polaris that you want to center, but it is the N.C.P that you want to be centered. Polaris is actually 44' (or 1/2°) from the NCP. Another very successful method that I use is adding in the star Kochab. It just so happens that if you extend a line starting at Kochab and dissecting Polaris and continue the line, it will "intersect" or terminate at the NCP. Most all PS'es are in reverse so be careful there too.
That 44' can make a difference - some may argue.
After performing a near perfect Polar align, then yes, I would progress to the Drift align. I am re-visiting this method myself as I need to fine tune my scope tracking.
The drift align really only involves two major components. Finding one star in the "south" within about 5° of the meridian and celestial meridian. In the Northern H, it is usually due south about 65° to 70°.
Then finding one star in the east about 20° to 30°.
The tutorials will explain what to so with these stars.
Posted 02 May 2011 - 10:36 AM
I knew about Polaris not being the true pole, the problem is there is a huge tree that blocks the pole area just enough that I can't view Polaris when the tree is fully flush with leaves, so I have to do a bit of guessing.
Again, thanks for the information.