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pjensen
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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
Transmographied
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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
Carpal Tunnel


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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Reged: 01/01/13

Loc: Sugar Land, TX
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
Post Laureate
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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

Loc: Rapid CIty, SD
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 (10 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
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: What method do you Polar Align with? new [Re: Footbag]
      #5790242 - 04/10/13 12:39 PM Attachment (7 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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Reged: 07/15/08

Loc: Reno, NV
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
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
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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Reged: 04/13/09

Loc: Scranton, PA
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
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
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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Reged: 10/20/10

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
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
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
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
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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