Polar aligned - at last....

[denniscook]

Skywatcher 130 with EQ2 mount and a Noob.

Well its taken nearly a week of research, adjusting, testing, cursing, more research, more adjusting, more testing, more cursing get the idea?

I read the book on how to Polar align, sounds straight forward, set the scope up pointing to Polaris, set altitude (52deg in my case), tripod reasonably level sight up adjust azimuth and fine tweak altitude and Bingo - Not. Sighted up Jupiter, set the tracking motor on and find I am constantly tweaking RA and Dec -what's gone wrong? After further reading (Astro Babys guide Simple Polar Alignment for Beginners is good) I am convinced it's not me. So knowing the scope and mount is not exactly top drawer, by experiment, I changed the factory set DEC dial to read 85deg instead of 90 and then set the altitude to 60deg instead of 52deg (which is my latitude) and finally nailed it. Rotate the scope RA axis around Polaris and it hardly moves. Sorted.

I know the EQ2 mount is not very accurate but I didn't expect to offset it by the amount I ended up with. So if you have got a Skywatcher 130 and an EQ2 and can't Polar align, it might not be you! Experiment with different DEC settings as well as altitude and you will get there. Don't assume the factory settings are accurate. After each adjustment of Dec, azimuth and altitude, check by rotating the RA axis till Polaris doesn't move. It worked for me.

Now setting circles..... I don't think so.

[dark knight]

That's great news Dennis,,just shows how accurate the scales are,,,NOT

[Astro_Baby]

To be honest the scales are never that great - though my EQ2 was pretty close.

The latitude scale on my HEQ5 is out by miles. At least 5'. I sometimes wonder whay they dont make the lat scale moveable with a small grub screw to lock it. Its an upgrade I have considered at times when I am bored.

[denniscook]

To be honest the scales are never that great - though my EQ2 was pretty close.

The latitude scale on my HEQ5 is out by miles. At least 5'. I sometimes wonder whay they dont make the lat scale moveable with a small grub screw to lock it. Its an upgrade I have considered at times when I am bored.

As a noob, you have to make some assumptions and the large error on the dials is a bit much to grasp as you are not entirely sure you are doing things right. Your guide to Polar aligning was brilliant to confirm that I was doing things right. I wonder if it would help other noobs if you could put a memo that the scales could be wrong if Polaris doesn't stay roughly still when you rotate RA axis? This check should be an essential step before moving on. This would have saved me hours!

Purely as an excercise, I might try the drift method to get things better. Glutton for punishment or what?

[adamsp123]

I ended up making an inclinometer and checked it against the marked dial on my vixen sphinx mount and it was about one degree out, or 2 full moons, or miss the gotos.

[Breakintheclouds]

Your guide to Polar aligning was brilliant to confirm that I was doing things right. I wonder if it would help other noobs if you could put a memo that the scales could be wrong if Polaris doesn't stay roughly still when you rotate RA axis? This check should be an essential step before moving on. This would have saved me hours

I suppose one problem is that there are two reasons why Polaris might move in the polarscope when you spin the RA axis. The first is that the polarscope reticle might not be aligned (which Astro Baby covers really well) and the second is the problem you had, that the mount's scales are properly aligned. So if this was added to the instructions then it would be necessary to distinguish between the two possible causes of error.

[dark knight]

I suppose one problem is that there are two reasons why Polaris might move in the polarscope when you spin the RA axis. The first is that the polarscope reticle might not be aligned (which Astro Baby covers really well) and the second is the problem you had, that the mount's scales are properly aligned. So if this was added to the instructions then it would be necessary to distinguish between the two possible causes of error.

We have to distinguish it anyhow don't we or am I missing something....

[Breakintheclouds]

You're right: if a person follows the recommended path, and aligns the reticle during daylight, then all should be fine. I was thinking of somebody who hasn't done this, and who just sets up their scope at night. When they look at Polaris they wouldn't be able to tell which of the two possible causes was leading to the star moving as they spun the RA axis. Perhaps I'm overthinking it.

[dark knight]

No, I think your absolutely right (what's your name to stop me having to type your long user name, oh I am lazy). When you think of the precision we require, the scales are next to useless...

[Breakintheclouds]

My name's Ian, although there seems to be some debate about that... see here:

http://stargazerslounge.com/primers-tutorials/90030-primer-understanding-night-vision-averted-gaze-telescope-tapping.html

:-)

[Astro_Baby]

Its a worthwhile addition which I will make to the guide in the week.

To be honest when I had the EQ2 I would tend to align Polaris in the main scope and let it go at that. For observational use I found it was accurate enough for tracking to stay aligned for quite long periods with only the occasional 'bump' on the hand controls to correct tracking errors.

I dont do astroimaging so I dont ever need super accurate alignment.

With the HEQ5 I tend to go for a good alignment on Polaris because without it the Synscan can get a bit sniffy when you do a three star align and I have found by experience that the better the polar alignment is the less hassle I'll have aligning the GoTo.

Theres also a view that an EQ mount doesnt really need to be level as its movement will cancel out any levelling errors. While that may be true in theory I have found Synscan can be messed up if the mount isnt fairly well level.

I'm a bit of a perfectionist for this stuff with the HEQ5 only because the GoTo can be very picky about it.

[denniscook]

Hi Astro Baby,

Thanks for the interest in my comments. I am not looking for perfection in Polar Alignment, lets be clear about that, it's just that after my initial alignment with all the errors that I now know, it was just hopeless. The DEC and RA needed constant adjustment to the extent that I thought I had done something wrong. I was expecting to give the odd tweak to the slow motion controls but my initial errors were so bad that I once thought I had the wrong mount! In fact it was easier (less adjustments) to track manually than to use the motor. I can't believe I am the only one with duff dials but I do see a lot of posts with noobs asking for Polar Alignment advice.

To cover all bases, a final check on rotating RA around Polaris proves all OK which you do mention in your second method, and not to believe the dials are calibrated better than +- 5deg which is not quite good enough for simple star tracking. Your very clear and easy to follow guide gave me the confidence to look elsewhere knowing that my intial settings "by the book" were right. Thanks very much.

My procedure was then to adjust the DEC +2 deg adjust az and alt to centre Polaris, rotate RA and check the swing. If better adjust DEC further and after readjust, if worse, adjust DEC-2deg and repeat. For me I had to go to -5deg before it became reasonable, which resulted in a lat of 60deg on the scale instead of the original setting of 52deg and DEC setting of -85 instead of 90. It's not absolutely perfect, but it's good enough for me and very usable now.

[Astro_Baby]

Always interested in comments on the guides - thats how I improve them to make them useful for beginners. Its a tough old learning curve at the start ( I still bear the scars myself ) and the guides were done to make it just a tad easier for a newbie to get to grips with it all ( and to save me retyping it every time on private mails )

[Jeremy]

I suppose one problem is that there are two reasons why Polaris might move in the polarscope when you spin the RA axis. The first is that the polarscope reticle might not be aligned (which Astro Baby covers really well) and the second is the problem you had, that the mount's scales are properly aligned.

Actually the accuracy of a mount's scales have absolutely no bearing whatsoever on whether Polaris (or any other object for that matter) moves in the polarscope when RA is rotated. The only causes of this are:

a) Reticule misalignment (as you mention)

Wobbly RA axis and/or unstable mount

c) Polarscope optical axis slightly misaligned with respect to RA

You can't usually do anything about © but that doesn't matter since reticule alignment can compensate for it.

[denniscook]

I started this thread as a Noob with a problem on the simple EQ2 mount on a Skywatcher 130 where I couldn't align with Polaris. For the avoidance of doubt, my set-up doesn't have a Polarscope only a finderscope. Astro Baby has two excellent tutorials, one on the Simple EQ2 to which I refer and one on the HEQ5 to which Ian and Jeremy refer. Just thought I'd point that out as we seem to be going off on a tangent.

[Jeremy]

Just thought I'd point that out as we seem to be going off on a tangent.

Yes - fair point.

Using the telescope scope itself as a polarscope - as in astrobaby's tutorial - always struck me as a really neat thing to do!

[red dwalf]

when i first bought my Celestron cg5 gt mount, it took me weeks to get it to work properly, i like you Dennis thought that there was something wrong with the mount, i read from the instructions on how to do it using the RA axis, making sure the mount was level, but then when i went to a target after an alignment it was always way off, so having thought about it and thinking that the scope may not be sitting on the mount squarely, i started looking though the scope so using it as the RA axis, and it`s alot better even on a quick align.

very hard to get your head around it when you`ve just started the hobby.

cheers Rob

[dark knight]

Yep, good idea using main scope as polar scope,,however you still need to know by how much to offset Polaris in the field of view if wanting to image as it's about 3/4's of a degree from true North Celestial Pole.

[BlueAstra]

I do a quick polar align by using the progamme 'polar align' to show me where polaris should be on the polarscope circle for the given time and date. I then move polaris to the indicated place by adjusting the Alt and Az mount screws. I don't look at the scales on the mount.

I later realised that the handset on my EQ6 pro gave me the same information after entering the initial time, date, etc. The display show the 'hour angle' of polaris which I think is the same 'clock' position shown by the programme.

The polar align programme can be found here:

Polar Alignment

[Astro_Baby]

YOu can use the main scope as a polarscope but you should be aware this will never yield super accurate results. Partly because without a polar alignment scope with a calibrated reticule you'll find it hard to know execatly which bit of the EP polaris should appear in.

BUT - with that said on a low cost mount like an EQ2 you'll probably never achiev huge accuracy anyway. What you'll get will be more than adequate for viewing.

On a scope with a polar scope in the mount you'll find that when the mount is correctly aligned and the main scope is in line with the mount Polaris will be unlikley to be in the main scopes EP view. There are various reasons for that but the big one is that the offset between the main scope and the mount is significant at the narrow viewing angles that even a wide angle scope like a reflector allows.

That gives you a perpective on how far out aligning a non polarscoped mount can be.

With that said what I used to do was mess about with the Alt Az controls until when I moved through the RA axis polaris stays staionary while the stars around it move around the EP. Thats probably (short of drift alignment) the best accuracy you can achive and more than good enough for half an hours worth on DSOs without having to give the mount a manual helping hand.

ps - as promised I have added a note to the simple polar alignment guide to reflect your issues with wonky latitude scales.

[Jeremy]

I do a quick polar align by using the progamme 'polar align' to show me where polaris should be on the polarscope circle for the given time and date.

Why do you do this, when the polarscope itself is designed to calculate this information for you?

[dark knight]

Hi Jeremy, using "Polar Align" saves having to set the time and date circles on the mount.

[Jeremy]

Hi Jeremy, using "Polar Align" saves having to set the time and date circles on the mount.

But not as much fun though...

[OzDave]

Skywatcher 130 with EQ2 mount and a Noob.

I read the book on how to Polar align, sounds straight forward, set the scope up pointing to Polaris, set altitude (52deg in my case), tripod reasonably level sight up adjust azimuth and fine tweak altitude and Bingo - Not. Sighted up Jupiter, set the tracking motor on and find I am constantly tweaking RA and Dec -what's gone wrong?

Hmmm, I might be wrong, since I'm quite new at this as well, but Jupiter (being a planet) does not follow the same path around the North Celestial Pole as the stars do. Instead it follows its orbit around the sun and follows a path pretty close to what is called the "ecliptic", which is the path the the sun follows through the sky.

Therefore, if you've set your mount to to "sidereal" tracking, you'll be able to track the stars fine if you have an accurate alignment, but you won't be able to track things that are not stars, like planets or the moon. Instead, you may find that switching the tracking mode to say "solar" might work for you, assuming your mount has that option.

The other thing you can try to verify your alignment is to sight up a bright star in the southerly direction and see if your mount is able to track that.

I also suggest having a look at the path planets follow in a planetarium software package like Stellarium as that will show you why the mount doesn't track them in the default star-tracking mode.

Hope that helps.

David

[dark knight]

Yep, that's correct David, Polar Alignment is what it says on the tin.