To calibrate or not to calibrate that is the question

[Simon Dunsmore]

Hi Folks, 

Sorry, after moving house, getting through Christmas and waiting for the rain to stop, I finally got to play with my new SW200pds on eq5 goto mount. I aligned everything as per the guidelines, all seemed quite straight forward and then I had a thought (first one this year) do I need to calibrate the polar scope to the finder scope? or do I just need to ensure that the polar scope sits true to the mount? 

Your help would be much appreciated. Also, didn't actually get to find anything as I was looking for as it seems the thing wasn't actually aligned, ahhhhhh well had fun trying, will try again soon. 

One last thing, I have the app on my phone that shows what the position of polaris should look like through the polar scope, I turn the scope to roughly mimic this, is that right? But I can't seem to lock the scope in position. 

Thanks for your help 

Kind regards 

Simon 

[ChrisEll]

I would use computerized polar alignment, e.g. Sharpcap or similar. I've never used a polarscope and the thought of one fills me with dread

[mikeyj1]

Hi Simon,

No you don't need to align the finder with the polar scope, but yes you do need to make sure it is aligned with the RA axis of the mount.  There are several videos on YT to show it, but basically align the crosshair with a point far away (better /easier done in daylight), such as a church spire, tv aerial etc, and then rotate the mount 180 degrees.  If the crosshair moves off the reference point, you need to adjust it using the three small grub screws on the Polar scope - carefully, and only 1/4-1/2 a turn at a time loosen one and them move the others as long as there is little resistance.  your aim is to halve the movement to the reference point.  Turn it back 180 degrees, and see if it is reduced.  It's an iterative process, thats why a fixed point in the daytime is better than a moving star, even polaris!

As far as ChrisEII's answer, (actually he didn't answer your question, did he..), yes you can ignore the Polar scope and do it by software but you need to connect the mount to a computer, have a camera, etc, etc.  My advice, start with what you've got!  As far as the app is concerned, it depends on the type of polar scope fitted (old v new style) as to rotating it to match the sky, or making sure the polar scope 'clock' is showing vertical 12 and 6.  the app i use is Polar Align pro http://astro.ecuadors.net/polar-scope-align/ I can completely recommend it, and there is lots of advice on this site also

good luck

Mike

 

[almcl]

For visual observing, super accurate polar alignment is not necessary - won't do any harm, and isn't difficult with a bit of practice, but it eats into observing time - so just pointing the polar axis north will do.  

The trick is to get the first star of the alignment routine in the eyepiece field of view.  For this it helps if your finder scope is aligned with the main scope - can be done in daylight on a distant object or on the moon or bright star when dark.  Then, if the first alignment star isn't in the eyepiece field of view (which quite often happens to me) there's a good chance it will be in the finder and the scope can be nudged to bring it into view in the eyepiece.  Once centred in the main EP, and a sync command issued, the next object(s) should be at least in the eyepiece if not plumb in the middle.

[Simon Dunsmore]

Hi Folks, Thanks for all the advice. I have taken a look at the Polar Align app, but can't seem to find it for Android :(. 

I'm still a little unclear about the polar scope. As mentioned before, I can't seem to lock it once I have rotated it. The other issue is should I guesstimate the approximate position of the constellations based on what I see and the app or is it more technical than that, I'm concerned that it may need to be more accurate. 

Thanks again 

Simon 

[almcl]

There's an app in the Play Store called Polar Finder.  It isn't free, but at 69p it shouldn't break the bank.  It gives a choice of reticules and shows where to put Polaris using the alt and azimuth adjusting screws.  Once this is done there's no need to lock the polar scope which will rotate with the RA axis, anyway.

[Stu]

@Simon Dunsmore are you imaging or purely visual? If just visual then I would not get too hung up about exact polar alignment. If you are imaging then I can move this to the imaging section to get more answers

[Simon Dunsmore]

Hi, Thanks for your message. Right now I am just visually observing, maybe once I've mastered that I'll move on to imaging