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Datalord

Polar alignment woes

41 posts in this topic

I'm quite frustrated. I need to polar align my mount for imaging purposes, so I'd like to do it properly, yet I simply can't comprehend the tutorials for some reason.

Gear:

Celestron Evo 6, StarSense autoalign (so fantastic for GoTo!), Wedge, Canon 6D.

 

Now, I bought a reticle with the lines in it, but batteries were faulty, so I never got that working. After reading a tutorial about using the lines eyepiece, I somehow still can't wrap my head around it.

So, here goes: What is the easiest way of making that setup polar aligned? I'm willing to throw money at it, so any piece of equipment that will help me is an option to buy. Or alternatively, an instruction that is easily understanable.

 

Edit: should mention that I can make 1 minute exposures, but at 3 minutes I have visible trails. I aim to be able to take 5 minute exposures.

Edited by Datalord

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Have you considered guiding?  Small PA errors are of less concern when guiding as they help keep the gears meshed anyway.

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I have, but it seemed to me that I should learn to do a proper PA before I delve into that can of worms? Is that a wrong assumption?

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1-3 minutes is 'excellent' for unguided errors, I have never managed more than two with my AZEQ6, even spending an hour doing PA..  The illuminated reticule eyepiece is useful for sky alignment, getting the star right bang in the middle, but you already have the starsense, so that should be better..

Depending on where you are in UK in terms of Light pollution, 1 minute might not be too bad :-/ and you can take lots and stack them, have you tried that?

DAN is right,  however, guiding will give you what you want.  Before you go splash out on guiding , wait for an evolution owner to offer some advice.   You can either do it with a finder guider type solution or get the the dedicated guidescope and camera

cheers

Mike

just seen your answer to Dan, that would be true on most scopes, but the evolution is supposed to compensate even for not having the mount level, can you check through the menu to see what the PA error is?

Edited by mikeyj1
update

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I do not think you can PA your mount. You ave to have an EQ mount to do this. There is a wedge available from Celestron but I do not know how good these are.

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Yes, I do have a wedge, which I believe is enough for doing PA?

And yes, I have done stacking, with 30 and 60 second exposures. That does give pretty nice results, but I would really like the deeper details possible. I haven't checked the PA error menu, I always use the skyportal app. I'll give that a read. And yes, perhaps the end of it will be the autoguider as well, but the reviews haven't been great on that one.

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One minute isn't bad unguided at 1.5m focal length, I know I've had much longer subs unguided but always at shorter focal lengths.  Guiding takes the limit off of it and you can continue to expose until the background gets too bright or highlights over expose.

 

Another option for brightening your image is using a reducer, your scope is f10 which is quite slow for imaging.  The apparent reduction in focal length will also allow you to expose for longer before trails appear.

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There is a method for doing PA using Starsense. It never worked well for me when I had SS but you could try it.

Peter

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6 hours ago, D4N said:

One minute isn't bad unguided at 1.5m focal length, I know I've had much longer subs unguided but always at shorter focal lengths.  Guiding takes the limit off of it and you can continue to expose until the background gets too bright or highlights over expose.

 

Another option for brightening your image is using a reducer, your scope is f10 which is quite slow for imaging.  The apparent reduction in focal length will also allow you to expose for longer before trails appear.

I did try a reducer, but it created some nasty arc artifacts on the pictures which totally ruins them. 

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35 minutes ago, Datalord said:

I did try a reducer, but it created some nasty arc artifacts on the pictures which totally ruins them. 

The spacing has to be exactly right or you will get that sort of thing.

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Post wasn't relevant as I hadn't noticed the starsense note. Removed to avoid confusion should anyone else read this.

Edited by Hicks
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On 14/01/2017 at 20:43, Datalord said:

I'm quite frustrated. I need to polar align my mount for imaging purposes, so I'd like to do it properly, yet I simply can't comprehend the tutorials for some reason.

Gear:

Celestron Evo 6, StarSense autoalign (so fantastic for GoTo!), Wedge, Canon 6D.

 

Now, I bought a reticle with the lines in it, but batteries were faulty, so I never got that working. After reading a tutorial about using the lines eyepiece, I somehow still can't wrap my head around it.

So, here goes: What is the easiest way of making that setup polar aligned? I'm willing to throw money at it, so any piece of equipment that will help me is an option to buy. Or alternatively, an instruction that is easily understanable.

 

Edit: should mention that I can make 1 minute exposures, but at 3 minutes I have visible trails. I aim to be able to take 5 minute exposures.

There was  polar alignment facility that you can access with the StarSense hand controller.

I cant remember the precise steps, but do the initial align with the star sense, then select the ASAP option form the menu not he controller - it is documented (but I've misplaced my manual ;(  )

 

 

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missed the edit, and the 'throw money' statement :)

 

1 minute unguided is a  bloody good result

so, in order

  1. try the ASPA, no additional cost.
  2. look into auto guiding - see FLO touptek/st80 bundle
  3. add QHY's polemaster to improve polar alignment
  4. get a GOOD equatorial mount ++++£

3 and 4 are into changeable - in my eyes.

I did 4 then 3.

 

 

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On 15/01/2017 at 00:36, Datalord said:

I have, but it seemed to me that I should learn to do a proper PA before I delve into that can of worms? Is that a wrong assumption?

Yes. Your focal length and camera conspire to give you a pixel scale which is entirely unrealistic unguided.

The drift method is wonderful because it removes both gadgets and software, both of which introduce their own ability to create errors!

Olly

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There is a really good 'How to Polar Align' (using a reticle eyepiece) on the Ian King Imaging website, it's under the Articles tab.

It takes you through the process step by step in such a way as you always keep a handle on where your scope is pointing and what adjustments to make to reduce the error.

With your set up and no guiding, I think you need to get your Polar alignment as close as you can for multi minute exposures. 

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THE QUESTION IS FROM A STARSENSE USER WITH A WEDGE ON AN EVOLUTION . PLEASE DON'T CONFUSE THIS PROCESS BY DESCRIBING VISUAL ALIGNMENT WEDGE PROCEDURES THAT ARE VERY DIFFERENT.  HERE IS THE CORRECT STARSENSE ON WEDGE PROCEDURE...

Evolution and WiFi users should note this must be done by Starsense HC. Unfortunately,  Polar Alignment using Starsense has not yet been implemented in SkyPortal or SkySafari. Most of this is omitted from the (useless) Starsense manual.

ADDED...

I have deleted the rest of this post as I have since posted more comprehensive instructions lower down this thread.

Noah

post-257973-0-16526500-1486462565-1.jpg

Edited by noah4x4
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Wow, nice Noah. Only saw this now. 

So, I tried this. My problem is that on step 9 the mount goes FAR away from the goto star. Like, I think I would be adjusting it to latitude 55 or something ridiculous. This is where I gave up on it. 

 

And yes, considering the gem now... :-( 

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On Saturday, March 04, 2017 at 13:29, Datalord said:

Wow, nice Noah. Only saw this now. 

So, I tried this. My problem is that on step 9 the mount goes FAR away from the goto star. Like, I think I would be adjusting it to latitude 55 or something ridiculous. This is where I gave up on it. 

 

And yes, considering the gem now... :-( 

I initially had that problem too.

You have to get the 'rough alignment' along the S Meridian within a  + or - 2° error else you will see your Cal Star move outside FOV ( but use your 40mm EP too) else your wedge latitude adjustment can be extreme. Simply forgetting to adjust for for magnetic pole deviation from true north will  also screw you up.  Get a decent Silva compass and take extra care.

Also use a 12.5mm cross hair reticle EP to calibrate camera/tube and centre stars. Until I got one I didn't realise how far off centre I was!  A RACI finderscope also offers benefits.  You do need to be highly accurate during each step to get an accurate PAE. But that isn't different on a GEM. I have achieved a PAE of 20 arc-seconds seconds on a wedge,  and reckon I can get better with practice and more care.

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Interesting. So in other words, I messed up the initial position of the tripod.

Alright, I'll hope for clear skies soon (one damn night in over a month) and try all this out.

Thanks again!

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1 hour ago, Datalord said:

Interesting. So in other words, I messed up the initial position of the tripod.

Alright, I'll hope for clear skies soon (one damn night in over a month) and try all this out.

Thanks again!

It's not easy to get under a 2° error from the S meridian, even with a compass. There isn't a guide line down the centre of the Tube,  and the 8" or 9.25"  Tube's actual centre isn't over the centre of the mount. So where do you put the compass to make the rough alignment? 

What I have since done is set up the mount correctly along the S meriden.  Then rotated the mount arm 180° so that it is still pointing north, but now on the other side of the Tripod with the Tube now also pointing north. I then put the Tube parallel with the Mount arm and physically got Polaris in my Finderscope and EP by moving the entire telescope and only the wedge altitude knob. Not easy! But I knew this was a decent visual Polar alignment.

I then rotated the mount arm back to its original position and put the Tube back to its correct check marks. I then marked the position of the Tripod legs on my patio so I never have to seek Polaris again (I leave my telescope assembled).  Now I just plonk the telescope on these check marks knowing that it is inside the 2 ° tolerance. Seems to work fine! Now I regularly get my Cal star inside the FOV of a 40mm EP and progressively get down to my 12.5mm reticle cross hair from there.  It's crude, but effective. 

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Funny, I had the same thought when I had a moment to think it through.

Good stuff! Thank you!

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Ok, I'm close to disassembling the thing, wielding the legs of the mount as weapons and going on a rampage in the Celestron headquarters to hunt down the developers of this software.

Finally, I have a starry night after a month of clouds. Out I go and try to set it up and polar align the beast.

What I did:

1. got the mount roughly on south.

2. placed the tube in direct parallel with the arm, pointing to polaris.

3. centered polaris physically.

4. Did the starsense 3 point dance.

5. Centered perfectly(!) on Regulus.

6. checked the polar align error. about 1" on both axes.

7. pressed a polar align. Used Regulus again.

8. it slewed away and then back perfectly on Regulus. Then it took the picture.

9. Then it slewed away and asked me to polar align with the knobs.

This is what it did:

58d0611982bf7_celestronfubar.thumb.jpg.c06c7caf60134bb374e1de71b33129ea.jpg

That arrow is roughly Regulus. I'm not kidding. That is not a 1" error. It's not even in the remote flipping ballpark of an error. Any suggestions? 

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So you have the right latitude/longitude co ordinates set / date etc 

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Yeah, it's all pretty well setup and like I said, after the first alignment, it puts the goto star right smack in the center of the eyepiece. I just can't comprehend this kind of error, so frustrating.

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Is the date in the right format  sometimes the day is in the month box or vice versa

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