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Polar aligning

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6 replies to this topic

#1 stephenws

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Posted 19 August 2019 - 09:56 PM

Is there a way to polar align without using a polar scope?

 

I have a home-made equatorial mount, made with pipe fittings, that I adapted a very nice clock drive to the R.A. axis.

 

For visual use I just roughly aim my R.A. shaft north and it keeps things in view with minor corrections, which is fine.

 

Problem is, I would like to start doing some basic astro photography. I realize I will have to get more precisely polar aligned. 

 

I would appreciate any suggestions for achieving this.



#2 DuncanM

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Posted 19 August 2019 - 10:16 PM

Is there a way to polar align without using a polar scope?

 

I have a home-made equatorial mount, made with pipe fittings, that I adapted a very nice clock drive to the R.A. axis.

 

For visual use I just roughly aim my R.A. shaft north and it keeps things in view with minor corrections, which is fine.

 

Problem is, I would like to start doing some basic astro photography. I realize I will have to get more precisely polar aligned. 

 

I would appreciate any suggestions for achieving this.

Use Google Earth,

Locate where your mount is. 

Zoom out over the location of your mount and find a visible object that is exact due north and align your polar shaft on that object.

Use a precision angle finder to set your latitude.


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#3 bobzeq25

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Posted 19 August 2019 - 10:20 PM

Is there a way to polar align without using a polar scope?

 

I have a home-made equatorial mount, made with pipe fittings, that I adapted a very nice clock drive to the R.A. axis.

 

For visual use I just roughly aim my R.A. shaft north and it keeps things in view with minor corrections, which is fine.

 

Problem is, I would like to start doing some basic astro photography. I realize I will have to get more precisely polar aligned. 

 

I would appreciate any suggestions for achieving this.

A few ways.

 

I use a PoleMaster.  Very easy, very fast, very accurate.  $300.

 

Drift alignment is free and accurate.  Somewhat time consuming.

 

People also use Sharpcap Pro and PhD2.  I'm unfamiliar.

 

What optics are you planning on using?  Commercial astrophotography mounts are very expensive.  For Deep Space Objects, the required precision is less than 1/1000 of an inch.  The longer your focal length, the more precision that you need.  I've seen homemade mounts work with short focal length camera lenses.  Never with a long focal length scope.

 

The Moon and planets are completely different, but you don't need too good polar alignment for those.


Edited by bobzeq25, 19 August 2019 - 10:25 PM.

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#4 sg6

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Posted 20 August 2019 - 01:34 AM

Software+Hardware as in Polemaster, and other packages seem to offer it - for some reason seems some of the image capture software does.

 

Drift aligning, but that needs to be learnt and so can take time, both to learn and to perform.

 

Polar scope is the easy option, and reasonably accurate. I think that whatever you decide on that you have to make the required adjustments,



#5 BQ Octantis

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Posted 20 August 2019 - 02:30 AM

G'day Stephen,

 

I use two low-tech, fast-n-free methods, but they require the SCP to be visible from my mount.

 

The simplest method is to point your objective aperture at where you think the celestial pole is (i.e., DEC = 90˚) and sweep the setup through through the RA range while looking through the finder scope. The entire scene will rotate around a fixed point; you just put that point on the pole by adjusting the mount's azimuth and latitude adjustments. Once you're in the ballpark, you can look through the objective at low magnification and do this again. Through my 2700mm Mak with a 25mm EP, this gets me ~2 arcminutes of accuracy in about 2-5 minutes.

 

Alternatively, you can mount a DSLR with a fast lens (I like to use my 50mm f/1.8) and do the sweep with an extended exposure (~1-2 seconds at ISO12800). You'll get star trails around the point of rotation; once again, you just adjust your azimuth and latitude adjustment with the celestial pole. Because it's iterative, it takes me 7-9 minutes to get ~2 arcminutes of accuracy.

 

Cheers,

BQ



#6 barbarosa

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Posted 20 August 2019 - 03:12 AM

With a camera the simplest and fastest method that i know is to use the Polar Alignment tool in SharpCap Pro. The cost is $15 per year and worth it. The freeware PHD2 has three alignment tools with both written  and  video instructions. I use PHD2 but haven't tried the alignment tools.



#7 Phil Sherman

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Posted 20 August 2019 - 01:46 PM

Drift alignment using a reticle eyepiece can easily require 5 minutes for each measurement. If you have a mechanized slew capability, you can do drift alignment with 70 second measurements with no additional software. 

 

See:

https://www.cloudyni...ll-do-it/page-2

 

For details.


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