Tracking - Help Needed.

[Spacehead]

Hi All,  Sorry to mither, but I want to confirm i'm doing things as best as my equipment will allow and i'm just not totally sure.

Ok, I have a 200p which I set up each time I observe - I have no permanent place for it yet.

So I take it out - point the N leg of the tripod roughly north to get me going, place the scope on the mount, balance it, re-position it to open the polar scope up - then begins my uncertainty.

So the best thing I can do is diagram.
Here is how my polar scope reticle looks.


This is how the reticle looks when my polar scope is fully open - with the telescope weights pointing down as far as they will go.
My head isnt tilting or anything - that is the angle its at in relation to the polar scope.

So when I got my motors, I thought i'd better have a go at aligning.  I read all over the shop but got so confused by these "setting rings with numbers on" and "next alignment time??" - what I actually have been doing is
just lining everything up so that the Pole Star is in the tiny circle marked "Polaris" and off I go.

Actually this has worked fairly well believe it or not - with the pole star in the tiny circle and my RA motor going, I can get 30 second subs no problem - whereas naturally, without the motor, or with the mount pointing randomly anywhere (say south) - I just get star trails.

So I was pleased'ish - but not knowing really why.

So I thought I better look into this a bit more.

I got an app on my phone, it picks up my GPS location and pops a green dot onto a circle -
This, when I hold my phone vertically - so the same angle as my head when looking through the polar scope is what the app shows.


You will immediately notice that my cross hair in the scope is not at the same angle as the crosshair on the phone app.

So do I tilt my phone so the cross hair looks more like an X than a + and then put the pole star on the circle in the finderscope where it shows the green dot on the app?
Im running out of steam now - I find this so confusing I cant even explain myself.

Any help appreciated.
Cheers

[steppenwolf]

I would suggest that you ignore the cross-hair orientation as this could be at any arbitrary angle - all the two lines of the cross-hair are doing is intersecting at the position of the North Celestial Pole (NCP). The important thing is to arrange for the position of the Polaris circle of your polarscope reticule to match that of your app. However, it is also important to ensure that your app is showing an inverted view as that is what you will see through your polarscope - your app may well have a 'switch' for this requirement

[CraigT82]

Yup just forget about all the dates, numbers etc... All you need is to:

1) Get the position of polaris at your time and location via your app (making sure it's giving you the inverted view). For example let's say the app is showing polaris at the two o'clock position on the circle.

2) now go to your polarscope and look through it. Ignore everything except the large central circle which has the tiny circle on it. Rotate your RA axis so that the tiny circle is at the two o'clock position on the big circle.

3) now use the mounts alt and az adjusters to put polaris in the tiny circle in the polarscope. 

4) done! Remember to check through the polarscope again after you tighten the tripod bolt.

[Spacehead]

Cheers - totally with it now, have had a tinker with the mount and my apps in conjunction with the above posts.

For info, I have two apps now - one has a "View As In Polar Finder Scope" tick box toggle option....... switching it on and off moves the dot 180 degrees to the opposite side of the circle - so yup - looks like I should have it ticked.

The other app shows Cassiopeia and the Plough, so I think I am correct that with that one (which doesnt have the invert switch), once I have rotated my RA axis on the scope, placing the tiny circle at 2 o'clock for example, then the stars should be in the same place on the app as they are in the reticle (which they were - so that isn't inverted).

It all makes good sense to me now (although my mind still boggles a bit when I think about earth rotating with my little scope sat on it and going round with it!!), thanks again.  Looking forward to a clear night now.

[Waldemar]

On your polar scope are setting circles for date and time and most of the time a level at the top.  Level the  polar scope first. Next you will have to put date and time on the setting circles on your polar scope to get the little circle in the right position. If you do that you will not need any app to align, your polar scope will show you what to do.

The position of that little circle changes with date and time, because the earth is rotating, so if you want to use the polar scope as it is meant, you have to follow the above steps.