Skywatcher Polarscope - Really Confused - Help Please

[nheather]

I have tried asking for help in words and it hasn't really worked.  So I've decided to try a photo story.

I have purchased a polarscope for my Skywatcher EQ3-2 mount.  Here it is

It doesn't come with any instructions, just what you see in the plain brown cardboard box.

I first contacted OVL who sold it to me and they pointed me at instructions on their website.  They are woefully out of date and refer to a polar scope to fit this mount.

That's no good.  That is for a very old style polarscope that isn't sold any more.  OCL weren't any further help and claimed to have no knowledge of the new style polarscope that they have been selling for years.  Anyway, with help from this site I worked out that you need to remove the old mount

URL=http://s853.photobucket.com/user/nigelheather/media/Polarscope/Removed.jpg.html]

And you can screw in the polarscope.

That's easy ... or is it?

There are two many variables for me to get my head round.  These are

1 - With the new style polarscope the reticule is fixed on the RA axel so rotates with the RA

2 - I know the what the reticule should look like at the Polaris Transit but I don't know where the RA should be at that point.

3 - The indicator mark is fixed in relation to the reticule out of the factory but can be unlocked and moved

So I know that at the polaris transit the reticule should look like this

and I can rotate the RA so the view looks like this but how do I know that the RA is in the right place?

I ask for two reasons

1 - the position the RA ends up in will depend on how the recticule has been assembled in the factory and how many threads it takes before the polarscope is screwed fully home.  I doubt this is the same for every polarscope and mount that skywatcher make.

2 - When I researched about remove the old polarscope mount the thread warned me not to lose the plastic washer.  So I had a look and found that mine had 5 plastic washers

These are very thin, and I reckon they are actually shims used to fine adjust the position of the polarscope indicator line and reticule by varying how many turns are needed to screw the polarscope home.

So using these rings I can fit my polarscope in 6 different ways which will result in 6 different RA positions when the reticule is in the transit position.

Once I have managed to match the reticule and the correct RA position I then need to turn my attention to the scale.  As I said, out from the factory the indicator is fixed in relation to the reticule.  However, Skywatcher don't put much effort into this as I found when I compared my polarscope with a friends.  Holding the indicator at the same place and looking through each of the scopes this is what we found

Totally different and if we just fitted them out of the box we would each end up with totally different reticule orientations for the same date and time.

This would suggest that you cannot rely on the Skywatcher setting out of the box and would need to move the indicator so that the date/time are correct when the mount is set for the transit position.

I think the key is knowing the orientation of the RA at the point of the Transit of Polaris.  Is this correct?  Is it fixed or variable?  If fixed where is it?  My guess would be with the RA in the central position so that the weight bar is pointing straight at the ground.

If this isn't the case I have a clue how to set it up as there are two many variables.

Does this make sense?

If so please can you help.

Cheers,

Nigel

[Alien 13]

I had the same problem but i dont think it matters on the position it ends up provided the Date Time Circles are adjusted to match i could be completely wrong of course but so far have managed to track M31 with 400mm scope ok on an EQ3-2.

[Sandancer10]

Hi Nigel

I'm having exactly the same problem with my factory fitted SW Polar Scope.  When I set the head of the tripod to the home position the small reticule is about 8pm instead of 6pm.  I tried to change it by wearing a rubber glove (as someone at the Astro Club said they had tried to change theirs and ended up with a finger print on the reticule). anyway, I ended up with some sort of sticky stuff (which must be a protecter or something) on the glove and a lovely blur on the reticule.  So, I cleaned it with a J cloth and that seemed to clear it.  Now I am wary of touching it, although I have been told that when the head is straight and in the home position the small circle should point South with the counter weight pointing straight down.  Then you find the HA of Polaris and using the scale showing on the end of the Polar Scope turn it tothe correct degree.  That should turn the reticule to the correct position.  For me, I am not using the small reticule and just putting Polaris on the edge of the large circle in the correct HA position.  Hope this helps.

[nheather]

I don't think you should be touching the reticule.  I believe that is what the 5 shims that I have are for.  By using a varying number of shims the reticule will end up in a different orientation in reference to the RA axle.

The problem is I don't know where the RA should be for the Polaris Transit - once I know that I think it would be simple.  But I could equally be way off - it could be that the RA position for different transits changes and if so I am really stumped.

Cheers,

Nigel

[Sandancer10]

I know, it was a stupid thing to do, but somebody at the Astro Club told me to take the lens off and move it manually.  How do you put the shims in?

[nheather]

The shims don't so in the polarscope - they just go between the polarscope and the mount - like this

Sorry it is a bit blurry but hope you get the idea.

If you have a non-pro EQ3-2 and had to take off the old style polarscope holder then if you look at the back of the removed holder you should see one or more rings - they are very thin and transparent so easy to miss.  You also need something thin and pointy to tease them out.

If you have a pro version mount then the polarscope comes pre-mounted so you would hope that it is also pre-set up but I wouldn't count on it.

My friend has a pro mount and he says that if he just uses the GOTO it comes up with a completely different polar alignment then if he uses the polarscope.  So I suspect that either he is not using it correctly or his is badly set up as supplied by Skywatcher OVL.

Cheers,

Nigel

[Sandancer10]

Thanks for that Nigel, but it is a Pro mount and came complete with the Polarscope.  You're right though, SW seem to just put the thing together and don't allow seem to align it properly.  Hence I just use the outer reticule.

I hope though that when the AP club meets again for a workshop someone more experienced can put it right.

Brenda 

[Cozzy]

I found this site very useful, full descriptions of how to set up your polar scope reticle etc.

 http://www.astro-baby.com/HEQ5/HEQ5-1.htm

Tim

[nheather]

I found this site very useful, full descriptions of how to set up your polar scope reticle etc.

 http://www.astro-baby.com/HEQ5/HEQ5-1.htm

Tim

Thanks, I've seen that before but you are incorrect about the purpose of that article. It tells you how to use a polarscope that has been set up, but not how to set it up in the first place.

I know how to use a polarscope, just a bit stumped in how to fit it correctly.

Cheers,

Nigel

[x6gas]

You can use the polar scope to produce reasonably accurate polar alignment without setting up the polar scope at all.  Here's how:

Download the nifty free programme PolarFinder scope from here: http://myastroimages.com/Polar_FinderScope_by_Jason_Dale/  That will show you where Polaris is relevant to the North Celestial Pole at any given time.  You then rotate the RA axis of your mount (or the polar scope) until the small circle marked Polaris on the reticle is in the correct place with respect to the NCP crosshair.  Then you simply move the Alt Az bolts on the mount to move Polaris in to the small circle and Robert is your mother's brother.

[nheather]

You can use the polar scope to produce reasonably accurate polar alignment without setting up the polar scope at all.  Here's how:

Download the nifty free programme PolarFinder scope from here: http://myastroimages.com/Polar_FinderScope_by_Jason_Dale/  That will show you where Polaris is relevant to the North Celestial Pole at any given time.  You then rotate the RA axis of your mount (or the polar scope) until the small circle marked Polaris on the reticle is in the correct place with respect to the NCP crosshair.  Then you simply move the Alt Az bolts on the mount to move Polaris in to the small circle and Robert is your mother's brother.

Thanks for that - I still don't get it though.  Are you saying that it doesn't matter where RA ends up just so long as polaris is lined up.  The bit I'm missing is that with this polarscope the reticule rotates as you move RA.  So for a given RA position, I can make the reticule show six different positions for polaris depending on how many shims I include.

Cheers,

Nigel

[x6gas]

Thanks for that - I still don't get it though.  Are you saying that it doesn't matter where RA ends up just so long as polaris is lined up.  The bit I'm missing is that with this polarscope the reticule rotates as you move RA.  So for a given RA position, I can make the reticule show six different positions for polaris depending on how many shims I include.

Cheers,

Nigel

"Are you saying that it doesn't matter where RA ends up just so long as polaris is lined up"

Yep, that's exactly what I am saying!  The only thing that matters with polar alignment is that the centre line of the RA axis is aligned with the North Celestial Pole.  The actual orientation of the RA axis doesn't matter at all... with one caveat:  for best results, the polar scope does need to be collimated in the mount.  There should be collimation thumb or grub screws on the polar scope and you can collimate by pointing the polar scope crosshairs at a distant object (TV aerial, say) and rotating the RA to see if the centre of the crosshairs move - there are guides on the web for this; it's a bit fiddly but straightforward and you should only have to do it once.

I have nothing but admiration for people who use setting circles etc to ascertain where polaris should be, but the programme linked to above does all that for you...

[nheather]

"Are you saying that it doesn't matter where RA ends up just so long as polaris is lined up"

Yep, that's exactly what I am saying!  The only thing that matters with polar alignment is that the centre line of the RA axis is aligned with the North Celestial Pole.  The actual orientation of the RA axis doesn't matter at all... with one caveat:  for best results, the polar scope does need to be collimated in the mount.  There should be collimation thumb or grub screws on the polar scope and you can collimate by pointing the polar scope crosshairs at a distant object (TV aerial, say) and rotating the RA to see if the centre of the crosshairs move - there are guides on the web for this; it's a bit fiddly but straightforward and you should only have to do it once.

I have nothing but admiration for people who use setting circles etc to ascertain where polaris should be, but the programme linked to above does all that for you...

So depending on how many of the 5 shim washers I use, for a given RA my reticule might look like one of these

If I line polaris up on each of these won't they given different polar alignments.

BTW - thanks for the collimation tip - yes I am aware I need to do that and will probably be a subject of more questions if I ever get that far

[Alien 13]

Hi Nheather if you want to use setting circles too they can be unlocked and moved to match the position of the polar scope reticule.

[x6gas]

So depending on how many of the 5 shim washers I use, for a given RA my reticule might look like one of these

If I line polaris up on each of these won't they given different polar alignments.

BTW - thanks for the collimation tip - yes I am aware I need to do that and will probably be a subject of more questions if I ever get that far

Yes, if you did that then you would indeed get different levels of poor polar alignment... but that's not what you need to do.  If you choose to use my method, you can forget about the shims altogether.

Let's say you use the PolarFinder software and it tells you that - for the date and time you are setting up your mount - Polaris should be at the ten o'clock position with respect to the North Celestial Pole - exactly as in the top right image above.

But when you look through your polar scope, let's say for the sake of argument, the small circle for Polaris is in the 6 o'clock position (as shown top left).  All you do is rotate the RA axis so that the small circle is where it should be (10 o'clock in this example) and then move the Alt Az bolts to get polaris in the circle.

[JamesF]

The first thing to do is just screw the polar scope in.  Forget all about the orientation of the reticle.

Then you need to go through the process of flipping the mount and centering the cross (which marks the Northern Celestial Pole) in the middle of the reticle so it always points at the same position regardless of the position of the RA axis.  AstroBaby's site explains this well.

Only once you have done that do you need to worry about the rotational orientation of the reticle.  The process for doing this is also explained on AstroBaby's website, but there is a short cut.  If you assume a time and date of midnight on 1st November, you need the Polaris indicator to appear vertically below the NCP cross.  This is much easier to judge as you can do it by viewing something vertical through the polar scope and rotating the RA axis until the Polaris indicator and cross are aligned against it.

It really doesn't matter where the Polaris indicator is when you initially screw it in.  The later alignment process corrects for that position.

James

[JamesF]

The shims don't so in the polarscope - they just go between the polarscope and the mount - like this

If you have a non-pro EQ3-2 and had to take off the old style polarscope holder then if you look at the back of the removed holder you should see one or more rings - they are very thin and transparent so easy to miss.  You also need something thin and pointy to tease them out.

You know, mine is a very old EQ3-2 and when I first took it all apart to make sure the polar scope was correctly aligned I never found any such shims.  I ended up fitting an O-ring at the end to keep the upper end of the polar scope centered.

James

[Alien 13]

I never bothered trying to get the position of my polar scope reticule in the right place after it dropped out when i slackened off the 3 adjustment screws too much. What is important is getting the scope aligned with the RA axis so that when you rotate through 180 degrees the center crosshair remains centered on a distant object. The mount RA can be moved so that the reticule image is in the correct position then the setting circles can then be calibrated, it makes no difference if the counterweight is pointed in an odd direction. In use a reasonable polar alignment can be done by just eyballing the sky and moving the RA till the polar scope reticule shows the same orientation then locking it off and adjusting till polaris is in the small circle.

[JamesF]

Wuss

Getting the correct orientation is actually a doddle compared with the faff of getting the polar scope aligned with the RA axis.

James

[CodnorPaul]

I am with you JamesF - my polar scope recticule fell out when I was trying to centre it so I popped it back in and followed AstroBabys set up video and it works a treat - really easy to get it all aligned