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Equipment Discussions >> Mounts

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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
What method do you Polar Align with?
      #5785723 - 04/08/13 11:27 AM Attachment (34 downloads)

I know that there are several different ways to polar align like using a Polar Scope, Using an all-star Align function, or simply using the sun or Polaris to guesstimate it. However, I have really begun to like the Polar Finder Scope method.

I went out on Friday night with the intent of seeing how long I could track without guiding. Typically all I do to polar align is line up the Big Dipper in the Polar scope with its orientation in the sky. This time I decided to do it more precisely.

I looked directly at Polaris and noted two stars that were either directly vertical or directly horizontal of each other in the big dipper. Then I rotated the mount and Polar Finder until those stars were either vertical or horizontal in the Polar finder.

It just seems like it is much easier to align based on points that are directly vertical or directly horizontal in relation to each other.

After I accurately placed Polaris in the small circle in the Polar Finder I rotated the scope to verify that my Polar finder was centered in my mount. It was dead on.

Then I started taking some images. I tried 2 minutes and it looked great so I went for 3 minutes and it still looked fine. Then I went for 5 minutes and it definitely started to show some star trails but honestly it was not as bad as I thought it would be.

I never attempted the All-star align simply because Polaris tracked exactly around the small Polar Finder scope all night long. The all-star alignment wouldn’t have helped because I had done the Polar Finder setup so precisely.

This is not to say that the All-star alignment shouldn’t be used. It does a great job especially when you do a true “rough” alignment with the Polar Finder. However, I have noticed that if you do an extremely precise alignment with the Polar Scope then the error tolerance in the All-star alignment is usually greater than it is with an extremely accurate Polar Scope Alignment.

Please note that this is the second Polar Scope that I have owned. I accidentally let the little piece of glass slip in the first one when I was trying to center it. Once it rotates at all you can no longer do a precise alignment in this manner and the All-star alignment will definitely be a better option.

3 minutes for an 800mm scope and a 2x crop factor camera. This is a 1:1 crop from the center of the image. ISO 800.

Edited by mpgxsvcd (04/08/13 01:03 PM)


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5785731 - 04/08/13 11:29 AM Attachment (42 downloads)

Here is the 5 minute image

Edited by mpgxsvcd (04/08/13 11:31 AM)


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5785741 - 04/08/13 11:32 AM Attachment (27 downloads)

Here is 3 minutes.

Edited by mpgxsvcd (04/08/13 11:33 AM)


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5785743 - 04/08/13 11:33 AM Attachment (30 downloads)

And 2 minutes

Edited by mpgxsvcd (04/08/13 11:34 AM)


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5785745 - 04/08/13 11:35 AM Attachment (25 downloads)

And here was 60 Seconds.

Edited by mpgxsvcd (04/08/13 11:35 AM)


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5785751 - 04/08/13 11:37 AM Attachment (18 downloads)

I also found that using the loss-less crop mode for live view was perfect for getting the focus right.

This is a rough focus using the regular live view.

Edited by mpgxsvcd (04/08/13 11:37 AM)


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5785752 - 04/08/13 11:38 AM Attachment (18 downloads)

And this was using the 10x crop mode.

Edited by mpgxsvcd (04/08/13 11:38 AM)


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Jeff2011
Pooh-Bah
*****

Reged: 01/01/13

Loc: Sugar Land, TX
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5785812 - 04/08/13 12:02 PM

Travis,

Interesting results. I have seen other CN members mention that the polar finder scopes did not meet their expectations. I don't have a polar finder scope but I am going to try the following once the clouds clear.

Since Polaris is about 0.7 degrees from the NCP, I am going to see what it looks like in Sky Safari with the view flipped accordingly for my refractor. Then with an eyepiece that has a field of view only slightly larger, I am going to then try to put Polaris at the approximate position in the eyepiece that Sky Safari shows it should be. When I was looking at it last night in Sky Safari that would have been the 5 o'clock position.

I have currently only used the polar align feature of the mount hand control and have been able to get a 2 minute shot without trailing, but that is with a 430mm focal length refractor.

Edited by Jeff2011 (04/08/13 12:03 PM)


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John Carruthers
Skiprat
*****

Reged: 02/02/07

Loc: Kent, UK
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5785856 - 04/08/13 12:24 PM

Having the reticle rotate doesn't prevent accurate polar alignment. So long as it is concentric with the RA axis it's orientation doesn't matter. The hour circle 'can' be made to match your local sidereal time but I've never bothered.
I often have to replace and update reticles to keep them current. It's not uncommon to have to simply replace one that's dropped out (an O ring behind them prevents this happening)
The little circle may be good if it's fairly new but after a few years the NCP drifts in relation to Polaris.

YEAR RA NPD degrees
1990 2h 21m 47' +2.1
2000 2h 32m 44' +1.3
2010 2h 44m 41' +0.5
2020 2h 56m 39' -0.3

http://www.awrtech.co.uk/oddtopic.htm#POLARSCOPE


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: What method do you Polar Align with? new [Re: John Carruthers]
      #5785919 - 04/08/13 12:48 PM

The important thing to note here is that I am aligning based on the orientation of the big dipper and not its position. That is a critical distinction.

Aligning by position means that you line up Ursa major by the angle it is at in the reticle. Your eyes are not very accurate when trying to estimate an arbitrary angle. However, if you align by the orientation of Ursa Major you can accurately align by using two vertical or horizontal stars.

My observation is that the Polar Finders seem to be accurately aligned from the factory. If you accidently let the glass slip it is very hard to get it back aligned as accurately as the factory. And yes they become less and less accurate over time. However, I bought the one I am using now over 6 months ago and I am still very happy with the results.

I don’t want anyone to get the impression that I am saying that using the Polar Finder is the best way to do it. All I am saying is that precisely aligning by orientation with the Polar Finder is much more accurate than aligning by position or by doing a rough estimate(Placing Polaris in the center of the reticle).

If you can’t do the all-star align for any reason then a precise orientation align is a good option. In addition I don’t believe that you should do a precise orientation align along with an all-star align. The all-star align has error tolerances that in my experience have always been greater than when I do the Precise Polar scope alignment.

I have never been able to get the All-star alignment to improve on my visual Polar Alignment. However, I can get the All-Star alignment to equal my visual alignment by doing a rough estimate first instead of taking the time to do the precise alignment.

YMMV though. Does anyone else use the Polar Finder only?


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: What method do you Polar Align with? new [Re: Jeff2011]
      #5785929 - 04/08/13 12:51 PM

Quote:


Since Polaris is about 0.7 degrees from the NCP, I am going to see what it looks like in Sky Safari with the view flipped accordingly for my refractor. Then with an eyepiece that has a field of view only slightly larger, I am going to then try to put Polaris at the approximate position in the eyepiece that Sky Safari shows it should be. When I was looking at it last night in Sky Safari that would have been the 5 o'clock position.





The big issue is that you are putting the scope position and orientation into the mix. If your scope is not exactly in its "home" position your results will be off. Using the Polar finder takes the scope out of the equation completely and just aligns the mount.


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psu_13
sage


Reged: 05/30/10

Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5786166 - 04/08/13 02:34 PM

I've started to use the new polar finder that Astrophysics came up with. It has a reticle that is more like the Tak finders. It's only disadvantage is that it requires the user to carefully align it to the RA axis with some tedious to use push/pull screws. I got it pretty close, but I'm not sure that it held.

Anyway, what I do now it put Polaris close to the right place on the reticle and then use PEMPro's drift align to do the rest. The scope seems to get me within about 5-10 arc minutes, and the final tuning with PEMPro gets it a bit better. If I could remember which knobs make the mount go which direction I'd be able to do this in about 10 minutes, but I always get mixed up. :-)

Pete


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andysea
Pooh-Bah
*****

Reged: 09/03/10

Loc: Seattle, WA
Re: What method do you Polar Align with? new [Re: psu_13]
      #5786370 - 04/08/13 04:40 PM

My with NJP I use the built in polar scope.
WIth the AP mount I have been using the Losmandy polarscope but I will be starting to use the right angle polar scope as soon as I receive it. I know two AP owners who just installed it with no tweaking at all and it seems to be working great.


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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5786405 - 04/08/13 04:58 PM

Quote:


In addition I don’t believe that you should do a precise orientation align along with an all-star align. The all-star align has error tolerances that in my experience have always been greater than when I do the Precise Polar scope alignment.

I have never been able to get the All-star alignment to improve on my visual Polar Alignment. However, I can get the All-Star alignment to equal my visual alignment by doing a rough estimate first instead of taking the time to do the precise alignment.





I presume you are talking about ASPA? In that case you must be doing something wrong because you should get much better polar alignment with ASPA compared to polar scope. That may not be noticable in short subs but over 15min it becomes very noticable.


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hottr6
Carpal Tunnel
*****

Reged: 06/28/09

Loc: 7,500', Magdalena Mtns, NM
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5786540 - 04/08/13 06:06 PM

When I look at your images, why do I see pairs of identically illuminated "stars", all with the same separation. Dead pixels?

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Dwight J
scholastic sledgehammer
*****

Reged: 05/14/09

Loc: Lethbridge, Alberta, Canada
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5786679 - 04/08/13 07:23 PM

Hi Travis: try using your camera to assist you in getting a better polar alignment once you have used your polar scope. It is a modified drift alignment which is best explained by this link: http://www.observatory.digital-sf.com/Polar_Alignment_CCDv1-1.pdf
A camera such as yours is just as capable to do this method.


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Phil Sherman
Pooh-Bah


Reged: 12/07/10

Loc: Cleveland, Ohio
Re: What method do you Polar Align with? new [Re: Dwight J]
      #5787036 - 04/08/13 10:24 PM

I've carefully aligned and marked my mount so I can set it with the polar reticle crosshairs vertical and horizontal when the mount is attached to a level tripod. When Power is applied to the handset, it gives me a "clock position" for Polaris on a 12 hour clock. doubling the difference between this value and 12:00 gives me a 24 hour displacement of the mount. I use the setting circles to move the mount the appropriate amount then polar align in the little circle.

I'm usually only a few minutes off on polar alignment. Accuracy can be improved by verifying that the azimuth adjustment of the mount is parallel to one of the crosshair lines before rotating the mount to Polaris' current position.

This is a manual version of the polar alignment routine used by EQMOD. EQMOD also turns on tracking, which keeps the targeting circle correctly positioned as you adjust the mount.

If I'm setting up for a week of imaging, I'll then do a photographic drift alignment.

Phil


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David PavlichAdministrator
Transmographied
*****

Reged: 05/18/05

Loc: Mandeville, LA USA
Re: What method do you Polar Align with? new [Re: Phil Sherman]
      #5787052 - 04/08/13 10:32 PM

I don't have a polar scope. I use Pempro's polar alignment routine.

David


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gezak22
professor emeritus
*****

Reged: 08/15/04

Loc: On far side of moon. Send help...
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5787111 - 04/08/13 11:00 PM

I have a GM8, and I use the polar scope to align it roughly. I then fine tune it using the drift method with PHD. For me this is the best compromise between speed and accuracy.

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tboconnor
member


Reged: 01/14/10

Re: What method do you Polar Align with? new [Re: gezak22]
      #5787129 - 04/08/13 11:13 PM

I'm in the southern hemisphere - I've never been tempted to use my polar scope

I use Celestrons All star, and it works really well so far.


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