Re: Polar alignment through main scope #iEXOS-100 #alignment #sharpcap


 

Tommy,
 
Nope.  Think about what the axes of your mount are doing during tracking and it should become clear.  
 
In a perfect world, the RA axis is in line with the celestial pole. The RA's tracking rate is basically countering the Earth's rotation, and the stars ahead of it appear to stay in the same place.  The DEC axis lets you aim the scope to either side of that rotational axis.  
 
So, let's say that that you did set the altitude on your mount's RA axis reasonably well, but just plunked the tripod down without much concern for the azimuth.  In other words, you have a poor Polar Alignment.  But one way or another, you do manage to slew to a target of interest and track.
 
What happens next?  Well, the RA axis will rotate, but it will not rotate in line with the celestial pole, so your target will drift away on you.  
 
If you are doing unguided AP, you should see streaks quite quickly from a bad PA.  If you are guiding, PHD2 will try to stair-step the DEC and RA movements to keep your target centered and your stars round, but there are limits to this, and where those limits are will depend on the size of the error, guiding and imaging resolution, target location, etc.  Might be ok for a given session, might not.  It's not uncommon for AP'ers to sometimes deliberately leave a small error in their PA, just to keep the DEC gears moving slightly - but we're talking minor, not major.
 
Bottom line, a good polar alignment is a prerequisite for good tracking. You didn't say which mount you have, but I assume from the question that you have an iExos-100, which does not come with an azimuth adjuster (the EXOS2 does come with one).  
 
The Az adjuster is recent option, and some here were doing creditable AP long before that. I think nudging tripod legs and fiddling with mount head bolts were the usual techniques for doing the Az adjustment, back in the day.  Just do the best with what you have - but the Az adjuster will help you get a better PA faster.  FWIW...
 
As to Explorestars, that's mostly for visual, rather than AP.  For AP, you'd likely use something based on either ASCOM or INDI - but that's really a whole 'nother thread's discussion.
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64

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