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mpgxsvcd
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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 wouldnít have helped because I had done the Polar Finder setup so precisely.

This is not to say that the All-star alignment shouldnít be used. It does a great job especially when you do a true ďroughĒ 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 (43 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 (27 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 (19 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 (20 downloads)

And this was using the 10x crop mode.

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


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Jeff2011
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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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Happy Birthday John Carruthers
Skiprat
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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 donít 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 canít do the all-star align for any reason then a precise orientation align is a good option. In addition I donít 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
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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
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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 donít 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
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Reged: 06/28/09

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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
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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
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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
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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
scholastic sledgehammer
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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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pjensen
super member


Reged: 04/08/12

Loc: Highland Village, Tx
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5787137 - 04/08/13 11:17 PM

Quote:

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.




Bought a polar alignment scope 2 weeks ago for my CG5. Used it several times now and it works great. In a minute the tripod is dead on (move the tripod, raise/lower a tripod leg).

From then on (after the 2+4 star alignment), the go to's are the best they have ever been.

For the first time, I am getting good goto performance out of this scope. I been seeing new Messier objects on every session.


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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: orion69]
      #5787190 - 04/09/13 12:15 AM

Quote:

Quote:


In addition I donít 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 noticeable in short subs but over 15min it becomes very noticable.




Show me any unguided 15 minute sub with an 800mm or more scope that doesn't have significant star trails. I don't believe you can do a perfect 15 minute sub unguided with ANY of the Polar Alignment methods. Even with perfect Polar Alignment you will still get star trails after 5 minutes unguided.

Edited by mpgxsvcd (04/09/13 12:18 AM)


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mpgxsvcd
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Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: What method do you Polar Align with? new [Re: tboconnor]
      #5787192 - 04/09/13 12:17 AM

Quote:

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.




Yes the Polar Scope really doesn't help much down south.


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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5787274 - 04/09/13 02:16 AM

Quote:

Quote:

Quote:


In addition I donít 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 noticeable in short subs but over 15min it becomes very noticable.




Show me any unguided 15 minute sub with an 800mm or more scope that doesn't have significant star trails. I don't believe you can do a perfect 15 minute sub unguided with ANY of the Polar Alignment methods. Even with perfect Polar Alignment you will still get star trails after 5 minutes unguided.




Why would I do 15min unguided subs???

You can shoot long unguided subs only with high end mounts but they certainly do not use polar scope for PA except for rough PA to get them faster start.


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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: orion69]
      #5787851 - 04/09/13 11:24 AM

Quote:


Why would I do 15min unguided subs???

You can shoot long unguided subs only with high end mounts but they certainly do not use polar scope for PA except for rough PA to get them faster start.




You should have written "I can shoot long unguided subs only with high end mounts but I certainly do not use polar scope for PA except for rough PA to get me a faster start." I can and do get longer subs simply by aligning with the Polar Finder. I only use the All-star Align and drift align when there is something preventing me from using my Polar Scope.

I think part of the problem is that some people have not figured out how to do a precise Polar scope alignment so they just assume it can't be done. Once a few people say that it isn't accurate then it gets the stereo-type of being inaccurate. You have to be extremely precise when doing a Polar Scope alignment for it to work. You also have to be willing to bend down and look through it. In addition you have to be able to shine a light in the front of it and hold your head straight up and down to line it up properly.

All of those things typically make people shy away from doing it that precisely and those are legitimate reasons.

However, that doesn't mean that the Polar Scope cannot be used for a precise Polar alignment without ever doing the All-star align or even a drift align. It can be done. All I am doing is trying to show everyone the procedures for doing it precisely and accurately with the Polar Scope.

A precise All-star align is not always possible if there are no stars in the right place, your alignment is way off, or you don't have a precise way of doing the all-star alignment. In those cases you might choose to just do a precise Polar Scope alignment. That is not to say that it is better. Instead it is just another way of doing it.

I always like to have options in case something goes wrong.

However, I also say that you should pick one method and stick to it for each session. If you are going to all-star align then don't try to do a precise Polar Scope Alignment. The point of doing a precise Polar Scope alignment is that you won't have to do an all-star alignment afterwards. If you get the Polar Scope alignment done correctly all the all-star alignment will do is mess up what you have already done correctly.

If it isn't broken don't fix it.

Edited by mpgxsvcd (04/09/13 11:26 AM)


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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5787975 - 04/09/13 12:34 PM

Well, it's all about final result, if polar scope works for you, that's fine.

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David PavlichAdministrator
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Reged: 05/18/05

Loc: Mandeville, LA USA
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5789255 - 04/09/13 10:21 PM

Quote:

Quote:

Quote:


In addition I donít 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 noticeable in short subs but over 15min it becomes very noticable.




Show me any unguided 15 minute sub with an 800mm or more scope that doesn't have significant star trails. I don't believe you can do a perfect 15 minute sub unguided with ANY of the Polar Alignment methods. Even with perfect Polar Alignment you will still get star trails after 5 minutes unguided.




My friend, Paul Burke (f29pc), posted a 20 minute unguided image at 2400mm focal length using his MI250. Now, he has a Gurley encoder on the RA axis but none on Dec. Less that good PA shows on the Dec axis. He has it polar aligned to the nth degree and add to that the Gurley encoder and you have the makings of a very good mount that can produce incredible results.

Edit: I dug up the thread Paul posted about his MI250. This.

David

Edited by David Pavlich (04/09/13 10:27 PM)


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gavinm
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Reged: 08/26/05

Loc: Auckland New Zealand
Re: What method do you Polar Align with? new [Re: David Pavlich]
      #5789546 - 04/10/13 02:52 AM

Polealignmax or PEMPro pretty much do it perfectly. Never used a polar scope (southern hemisphere) and only use drift alignment for a rough alignment before I use software...and even then, latitude and compass are good enough for software to take over...

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Jeff2011
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Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5789930 - 04/10/13 10:22 AM

Quote:

I think part of the problem is that some people have not figured out how to do a precise Polar scope alignment so they just assume it can't be done. Once a few people say that it isn't accurate then it gets the stereo-type of being inaccurate. You have to be extremely precise when doing a Polar Scope alignment for it to work. You also have to be willing to bend down and look through it. In addition you have to be able to shine a light in the front of it and hold your head straight up and down to line it up properly.

All of those things typically make people shy away from doing it that precisely and those are legitimate reasons.

However, that doesn't mean that the Polar Scope cannot be used for a precise Polar alignment without ever doing the All-star align or even a drift align. It can be done. All I am doing is trying to show everyone the procedures for doing it precisely and accurately with the Polar Scope.






Travis,

I for one applaud your post. I often find myself on the unpopular side of a discusion like the 8 inch vs 10 inch Dob question.

I always enjoy reading posts like yours were someone puts in the effort to try to make something work were others have given up on it. I currently do not own a polar scope, but your post is a refreshing change from the typical, don't get one, its is a waste of time.

How does that old Monty Python sketch go. The king thought I was daft to build a castle in the swamp, so I built one anyways.... and the third one stood.

Jeff


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Footbag
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Reged: 04/13/09

Loc: Scranton, PA
Re: What method do you Polar Align with? new [Re: Jeff2011]
      #5790149 - 04/10/13 12:04 PM

I have the AP PASILL4 and only give it a so-so rating. When I rotate it, I get a slight bit of movement on the centered object. The adjustments seem a bit dangerous. If the RAPAS continues to get good reviews, I'll pick one up eventually.

My favorite PA method is PHD drift method. It probably takes 20m. But I've also been using the AP Quick Drift method. There are a few more things that can go wrong, but the results are amazing.

mpgxsvcd,
Have you tried calibrating your images with darks? I'm wondering whether the noise and hot pixels will calibrate out.


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Raginar
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Reged: 10/19/10

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Re: What method do you Polar Align with? new [Re: Footbag]
      #5790161 - 04/10/13 12:08 PM

Footbag,

Have you tried PEMPRO's polar alignment wizard? It's pretty good too.

To the others, I don't think a polar scope or one of the software alignment routines is going to get you to 15 minute unguided subs. But they do put you in a position to perform a simple drift alignment that will allow you to perform within the specs of your mount. Some are better than others... but you can get your polar alignment that you can do unguided photography. Just depends on the mechanics of your particular mount and the image scale of your CCD/telescope combination.


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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: Raginar]
      #5790240 - 04/10/13 12:39 PM Attachment (12 downloads)

I tried comparing my visual Polar Aligning with the Polar Scope to the All-star aligning last night. The first image below is a 4 minute exposure with the Aligning done visually with the Polar Scope only.

There were no stars that were directly horizontal or vertical so you can see that my tracking was not good for this setup.

The second image below was taken after I did an extremely precise All-star Polar Alignment with my Cg-5 mount. As you can see tracking is still an issue with that image. All it did was change the angle of the drift but it really didnít decrease the magnitude of it.

This is why I say that if you are able to achieve a very good Polar Alignment with the scope then just leave it alone. Using the All-star Alignment will not improve on a ďPreciseĒ visual alignment. However, if you do a rough visual alignment then by all means do the All-star alignment because it definitely can correct most of your original error.

In my experience you can get roughly the same results by doing a very precise visual Polar scope alignment or an All-star alignment. However, doing a good visual Polar Scope alignment requires much more attention to detail than doing a good All-Star alignment.

Anyone can do a good All-star alignment. Not everyone will have the patience to do a good visual alignment. Once you get enough practice at both methods they take about the same amount of time to do.

4 minutes unguided. Not a very precise Visual Alignment because no stars were horizontal or vertical.

Edited by mpgxsvcd (04/10/13 12:41 PM)


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mpgxsvcd
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Re: What method do you Polar Align with? new [Re: Footbag]
      #5790242 - 04/10/13 12:39 PM Attachment (9 downloads)

Quote:

I have the AP PASILL4 and only give it a so-so rating. When I rotate it, I get a slight bit of movement on the centered object. The adjustments seem a bit dangerous. If the RAPAS continues to get good reviews, I'll pick one up eventually.

My favorite PA method is PHD drift method. It probably takes 20m. But I've also been using the AP Quick Drift method. There are a few more things that can go wrong, but the results are amazing.

mpgxsvcd,
Have you tried calibrating your images with darks? I'm wondering whether the noise and hot pixels will calibrate out.




Yes darks definitely works great with the GH3. I was just trying to show that you can track fairly well with the CG-5 even without guiding so I just attached the cropped out of camera image. It cleans up very well if you either do in camera darks or stack with darks in DSS.

4 minutes unguided after precise All-star alignment.

Edited by mpgxsvcd (04/10/13 12:42 PM)


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Peter in Reno
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Re: What method do you Polar Align with? new [Re: Raginar]
      #5790279 - 04/10/13 01:00 PM

In order to get round stars with 15 minutes unguided, I believe you need a pointing model that will take care of refraction and other irregularites in the sky. The only time the stars move at sideral rate is at the Meridian +/- 1 hour (or less) of each side. Even with perfect polar alignment, I don't think you can get good unguided results at least 1 hour from the Meridian without a pointing model.

For example, one night I was finished with polar alignment and slewed to a star in the East which was nearest to my target DSO for imaging, centered the star with imaging camera. The sky was not dark yet so I went insdie and watch TV until the sky got darker. 30 minutes later, I went outside to check on the star, the star drifted in RA instead of Declination. I wondered why drift in RA and later figured out that my mount was tracking in sideral rate and the star was about three hours from the Meridian. If I had pointing model already done, the star would have remained or very close to the center. Drift in RA instead of Declination was an indication of good polar alignment because bad polar alignment will show drift in Declination. If the star was near the Meridian, then the star would have stayed closer to the center of my camera.

My setup is always portable, so I think pointing model would have been too time consuming. In addition to good polar alignment, autoguiding should be good enough for any mount. I would not try to work too hard on getting good images unguided. You are better off to add a guidance system using guide scope or Off Axis Guider and you will be happier using autoguiding.

My method of polar alignment is Astro-Physics (A-P) Quick Drift Alignment using A-P Meridian Delay found in all A-P mounts. With experience, it takes less than 15 minutes and it's quite accurate that I can image at 30 minutes sub-exposures, autoguided of course. I also have A-P polar scope which is the same as Losmandy polar scope and found it to be inaccurate for long exposure imaging. It's good enough to get started and help to finish accurate polar alignment quicker.

Peter


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mpgxsvcd
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Re: What method do you Polar Align with? new [Re: Peter in Reno]
      #5790347 - 04/10/13 01:27 PM

These are definitely the type of posts I wanted to see. I just want to know what works and what doesnít and what works for some people may not work for others.

I totally agree with the sentiment that guiding is the optimal solution. However, I simply donít want any wires attached to my mount. My camera allows me to do everything wirelessly and I would like to keep it that way if at all possible. If someone made a standalone auto guider that didnít require a second larger scope I would be willing to pay a lot for it.

I tried the Celestron NexGuide Autoguider with my finder scope and it simply didnít work. It couldnít find any stars with the small finder scope. It looks like the scope they recommend for use with it is too heavy for my mount with my rather heavy AT8IN.

Does anyone have a good auto guider solution that doesnít require wires or another heavy scope? Is there any way to use the NexGuide Autoguider off axis?

http://www.amazon.com/Celestron-93713-NexGuide-Autoguider/dp/B003VRUGRG/ref=s...

http://www.amazon.com/Celestron-Guidescope-Package-125mm-Extension/dp/B004IB2...


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Footbag
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Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5790358 - 04/10/13 01:36 PM

There aren't many fans of standalone guiders here, and I only know that I've seen a lot of people send them back. Is it the wires you don't want or the laptop?

I don't know anythign about them but, TS sells the LVI guider. That may allow you to go laptop-less, but not wireless.


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mpgxsvcd
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Re: What method do you Polar Align with? new [Re: Footbag]
      #5790449 - 04/10/13 02:21 PM

Quote:

There aren't many fans of standalone guiders here, and I only know that I've seen a lot of people send them back. Is it the wires you don't want or the laptop?

I don't know anythign about them but, TS sells the LVI guider. That may allow you to go laptop-less, but not wireless.




It is the laptop that I want to refrain from using. I donít mind the wires as long as they move with the scope. I have wires from the mount to the scope and from the scope to a dew fan. I just donít want wires that go from the scope/mount to anything that is not moving with the mount.


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HowardK
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Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5790471 - 04/10/13 02:32 PM

SBIG. SG4

Stand alone guider...set up one time with laptop for focus then no more laptop needed.

Comes with its own tiny lens...mine is attached to a tiny 50mm hutech scope.


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orion69
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Re: What method do you Polar Align with? new [Re: HowardK]
      #5790513 - 04/10/13 03:01 PM

@mpgxsvcd

You can't evaluate precision of polar alignment by doing unguided subs. Your mount is simply not good enough for that. Even with high end mount you'll need precise star model and absolute encoders for long unguided subs and that is not achieved with polar scope.

I'm not saying that polar scope is useless, of course not. But for longer guided subs in most cases you'll need better PA (drift is the best).
I can say from personal experience that you can get 30min guided subs with ASPA using OAG. As for stand-alone autoguider I would not recommend it. Best option is to get OAG for subs 15min and longer.

Forget unguided imaging.

Cheers

Edited by orion69 (04/10/13 03:06 PM)


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mpgxsvcd
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Re: What method do you Polar Align with? new [Re: orion69]
      #5790570 - 04/10/13 03:33 PM

Quote:

@mpgxsvcd

Forget unguided imaging.

Cheers




Sorry I donít agree with that sentiment. I understand that most people require guiding because their focal lengths are too long and their focal ratios are too large. That is precisely why I bought the scope I have.

I donít need to track for super long durations. In fact I start to blow out the sky in my back yard in about 8 seconds at my max usable ISO(6400). At 4 minutes I have to use my minimum ISO(200) to avoid blowing out the sky. Going any longer than that would be of no benefit to me.

However, I would like to be able to accurately track from 1-3 minutes without guiding. I have found that I can achieve that with the Polar Finder Scope and I thought I would share that with anyone else who would like to do the same.

In my experience things like wind and uneven cooling affect my tracking more than the error in my Polar alignment do if I have done a precise Polar Alignment.

As I have said before. I am not trying to say that using the Polar Finder is the best method. However, if you choose to only use a Polar Finder then trying to line up stars horizontally or vertically will help you get enough precision to do 2-3 minute subs.

One thing I havenít seen mentioned here is the use of apps like ďPolar FinderĒ to aid in aligning with the Polar Scope. I just bought the app for about $1 for my Android phone. It looks good so I am going to try it tonight.

Does anyone else use this app instead of the diagramís of UM inscribed on the Polar Finder?

It is important to remember that you have to set the image orientation to ďTelescopicĒ in the app to accurately find out where Polaris should be in the finder scope. However, that also means that UMA will be on the opposite side of where it appears to be when you look at the etching on the Polar Finder.

If you use the app it is best to just ignore the UMA etching in the Polar Finder altogether.

Ideally you want Polaris to be either vertical or horizontal even with the app because estimating angles in-between those is much more difficult. I really wish that the polar finder had the 15 degree increment marks like the app has. It would be so much easier to be more precise if it did.

http://www.appbrain.com/app/polar-finder/com.techhead.polarfinder


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Raginar
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Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5790622 - 04/10/13 04:06 PM

Travis,

What he's trying to tell you is that it is very difficult for very experienced people to do what you're asking. Your mount doesn't have the mechanical fortitude to perform in a manner you think it can. If it did, why would most of us APers spend several thousand dollars on our MI250s, G11s, and AP mounts?

The real problem is your mount is overloaded. I had trouble with my AT8IN on my CGEM. I imagine you will run into similar issues with your CG5.

I know, it sucks. You could try hypertuning, but you're shining a *BLEEP*. A *BLEEP* that works with light weights (which your AT8IN isn't) and widefield refractors. But a *BLEEP* nonetheless.

Good luck!

Chris


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mpgxsvcd
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Re: What method do you Polar Align with? new [Re: Raginar]
      #5790666 - 04/10/13 04:30 PM

Quote:

Why would most of us APers spend several thousand dollars on our MI250s, G11s, and AP mounts?





That is a great question. So what did make you choose one of those mounts over a less expensive model? Was it because someone told you it couldn't be done with anything less or because you tried other mounts and no matter what you did they wouldn't meet your expectations.

Sure we would all love to have those mounts that you listed. However, some of us simply do not have the means to purchase them. Instead we make compromises and purchase lesser mounts and then spend extra effort on optimizing them to get the results we are after.

In the end we both are happy with our equipment. What gets me is when people say "It can't be done" and what they really mean is that "It is really hard to do".


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Footbag
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Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5790745 - 04/10/13 05:10 PM

Quote:


However, I would like to be able to accurately track from 1-3 minutes without guiding. I have found that I can achieve that with the Polar Finder Scope and I thought I would share that with anyone else who would like to do the same.




If you are happy with your results, then nobody can tell you otherwise. I suspect that as you improve, you will look back at the images you took and not be as impressed as you were previously. This hobby is a moving target. As you improve your images, you realize there are other aspects to improve.

I switched to the Mach 1 because my last mount couldn't do what I wanted. Track 30m guided for narrowband @ 2032FL. At that point, I knew my equipment very well. It wasn't somebody telling me it couldn't be done, it was me trying it over and over. The new mount makes it easy.

As far as the "it cannot be done". In this hobby, one can do anything. That's not to say everyone would be happy with their results. Keep in mind, most imagers throw away their images that show drift, but not all.


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psu_13
sage


Reged: 05/30/10

Re: What method do you Polar Align with? new [Re: Footbag]
      #5791146 - 04/10/13 07:51 PM

Here is my experience with mounts.

I started out trying to use a Mallincam on my 8SE alt/az mount. Here is maybe a 20-30 second frame from that

http://www.flickr.com/photos/79904144@N00/5738121295/in/set-72157629128096583

Notice how the stars are already trailing.

Here is a shot I look later on after I moved the telescope (an 8inch SCT) to a CG5

http://www.flickr.com/photos/79904144@N00/5793350900/in/set-72157629128096583/

This is at around a minute. I found that with the scope at F5 (1000mm focal length) I could get 60 to 90 seconds out of the CG-5 without a lot of jumpiness. I always used the all-star polar align scheme.

As a comparison here is a shot at 300mm focal length (a refractor) at almost 2min

http://www.flickr.com/photos/79904144@N00/6788830992/

After using the CG-5 for a while I decided that I was serious enough about taking pictures and had the money to get a "serious' mount. More on what I think "serious" means later. But I bought a Mach-1. Here is a stack of 2min exposures with the Mach-1 at 1200mm focal length:

http://www.flickr.com/photos/79904144@N00/6835654848/

They register well enough that stacking worked. And there is less trailing than in the short focal length shot above. This is why people buy expensive mounts. They are mechanically more accurate, smoother, and more reliable than the cheaper stuff. This is not to say that you can't make the cheaper stuff work, of course you can. It is just to say that the expensive stuff does have value and it makes everything easier.

I'll also say that even having spent thousands of dollars on the Mach-1, I never managed to do better than about 3min unguided without the stars trailing too much. Here is such a frame, also at 1200mm

http://www.flickr.com/photos/79904144@N00/7213284504/in/set-72157629550839360/

There is enough jitter in even the best gear train to require that you do some kind of guiding or other computer-enhanced tracking (modeling, encoders, whatever). For the Mach-1 I have used the same meridian flip based scheme at Peter from Reno, and more recently PEMPro. My experience with the mount pretty much matches his.

Later on I finally decided I had to investigate guiding, so I bought an SBIG camera with a guider in it. Here's 4 minutes guided without even thinking too hard. Note how everything is rock solid:

http://www.flickr.com/photos/79904144@N00/7828074704/in/set-72157631169684214/

I sympathize with the desire to keep things simple, but we are talking about holding a camera and telescope exactly in sync with the earth's rotation for hundreds of seconds. You can't buy that with just polar alignment and a relatively cheap mount IMHO.

My longer thoughts about mounts:

http://atelescopeinthecity.blogspot.com/2011/05/mount.html

and the Mach-1

http://atelescopeinthecity.blogspot.com/2012/03/value-for-money.html

Oh, and, FWIW, the control box of the Mach-1 does not move, so you can hook wires up to it without worrying about it.

Cheers and good luck


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jsines
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Reged: 09/06/11

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Re: What method do you Polar Align with? new [Re: Dwight J]
      #5792210 - 04/11/13 11:58 AM

Quote:

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.





Question on this method - I've been trying it for a few weeks with good results, but I'm not sure I'm doing it right. Should I polar align, then find a star, then turn on sidereal tracking, then image and move the scope east/west at the lowest speed? Or, should I keep sidereal tracking off?

I'm doing it with tracking on right now, and I'm getting spot-on solid lines every time the first time, with up to 2 minute exposures. I'm wondering if I'm doing something wrong, or if I'm doing something right. :P


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psu_13
sage


Reged: 05/30/10

Re: What method do you Polar Align with? new [Re: jsines]
      #5792418 - 04/11/13 01:48 PM

Since you are moving the mount by hand it doesn't really matter if it's tracking or not. The sidereal tracking only tracks in RA anyway, and you are using the scheme to look for drift in DEC.

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