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New approach for Polar Alignment

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#1 antariksha

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Posted 27 September 2019 - 09:50 AM

The topic of Polar Alignment is not at all new. Lot of approaches, automation tools are available. Yet, some aspects in all the current approaches drove me towards doing some more work. The key aspects of this approach are as follows.- Ability to do the Polar alignment without polaris sited- Relatively less complexity than drift alignment- Ability to address to a good extent the atmospheric refraction to finally locate correct NCP / SCP position- A good starting point for amateurs who wish to graduate towards sophisticated tools and techniques- Ability to quickly verify if the polar alignment is intact after one object photographed or viewed, and the equipment is being pointed to another object. This point is mentioned in light of the fact that sometimes the polar alignment gets disturbed and the next object photographed shows star trails. This is especially true if payload is tweaked for next photo.

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#2 kel123

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Posted 18 October 2019 - 04:48 AM

It is great to have another option for polar alignment. You need to find a name to your approach. Good job.

What do you mean by 10 minutes? Do you mean it tracked for only 10 minutes or you are able to get 10 minutes subs guided or unguided?

Edited by kel123, 18 October 2019 - 06:11 AM.


#3 StrStrck

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Posted 18 October 2019 - 05:40 AM

Tillu-alignment?!waytogo.gif



#4 kel123

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Posted 18 October 2019 - 06:12 AM

Tillu-alignment?!waytogo.gif


I don't get this

#5 StrStrck

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Posted 18 October 2019 - 02:53 PM

I don't get this

That’s antariksha’s last name, so...



#6 kel123

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Posted 18 October 2019 - 03:42 PM

That’s antariksha’s last name, so...


Oh that. I didn't notice. Lol. Someone was saying it is a variation of schenier method of drift alignment. But is I checked that method and I don't think so.

The schenier method can only work for latitudes for 30 degrees upwards and it is apparently more complex.

If this method works. It should be heralded. It is so simple. T

he most difficult part is only finding the named pairs which might be difficult in light pollution since I don't think they are particularly bright stars.
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#7 kel123

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Posted 18 October 2019 - 09:04 PM

This author just posted and ran away. 



#8 antariksha

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Posted 22 October 2019 - 10:52 AM

Hello, Kel123,,sorry for the late response. There has been some family health related emergency , so not been able to login on daily basis.

So, your query is related to 10 min... I tried the tracking for 10 min and it worked well. I had pointed to some object and it was in the dead center of the cross hair of the main telescope focus. I did not try beyond to see the limit beyond which, the drift is observed.

 

 

And dear Strstrck and Kel123,

My sign-in for Cloudy nights, is antariksha. It is a word from Sanskrit ..Ancient Indian language. The meaning is "the universe". And Tillu is my family name, just to clarify.

 

And, finally, the method appears to be simple and cost effective. I mean it does not need the polar scope, or camera pointing towards Polaris and the associated alignment software running on a laptop.


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#9 kel123

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Posted 22 October 2019 - 11:02 AM

Hello, Kel123,,sorry for the late response. There has been some family health related emergency , so not been able to login on daily basis.
So, your query is related to 10 min... I tried the tracking for 10 min and it worked well. I had pointed to some object and it was in the dead center of the cross hair of the main telescope focus. I did not try beyond to see the limit beyond which, the drift is observed.


And dear Strstrck and Kel123,
My sign-in for Cloudy nights, is antariksha. It is a word from Sanskrit ..Ancient Indian language. The meaning is "the universe". And Tillu is my family name, just to clarify.

And, finally, the method appears to be simple and cost effective. I mean it does not need the polar scope, or camera pointing towards Polaris and the associated alignment software running on a laptop.


My sympathies and thanks for for your response.

#10 paolotto

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Posted 23 October 2019 - 04:23 PM

Thank you very much for sharing this method (and for the hard work of coming up with it and doing the initial testing).  I look forward to trying it out and comparing it with software-assisted PA (polemaster in my case).

 

For those who like me don't have a crosshair eyepiece, I just wanted to remind you that you should be able to center stars quite accurately by intentionally shifting the star far out of focus until you get a big "snowball" and align its edges concentrically to the edge of the regular eyepiece's field of view. 



#11 antariksha

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Posted 24 October 2019 - 10:15 AM

thanks.. 

 

Thank you very much for sharing this method (and for the hard work of coming up with it and doing the initial testing).  I look forward to trying it out and comparing it with software-assisted PA (polemaster in my case).

 

For those who like me don't have a crosshair eyepiece, I just wanted to remind you that you should be able to center stars quite accurately by intentionally shifting the star far out of focus until you get a big "snowball" and align its edges concentrically to the edge of the regular eyepiece's field of view. 

interesting suggestion about a substitute method for crosshair.... thanks



#12 kel123

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Posted 28 October 2019 - 09:41 AM

Hi antariksha

If I may ask, what is the effect of light pollution on those pairs of stars. Are they useable in the city or only at dark sites.

Secondly, will this work at latitudes close to the equator or even the equator itself?

Thanks

#13 antariksha

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Posted 29 October 2019 - 05:54 AM

The stars listed are brighter than Mag 4.5.

Heavy light pollution will definitely mask some of the star or affect the visibility of some of the stars in the tables. For example, I live in Mumbai, India. This is a mega city and I practically see no stars from my City residence. However, my telescopes and other astronomy gear is in my village home ( its name is Antariksha which translates in English to "the universe"). At this place, the sky is not perfectly dark, none the less, the stars upto Mag 5.1 are visible. Thus, I can locate all the stars in the two tables.

 

And, since the mathematics used is irrespective of the latitudes, I feel the technique should be usable from Equator or even from Southern hemisphere without any issue.



#14 kel123

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Posted 29 October 2019 - 06:30 AM

Thanks so much for your prompt response. When I wonder about latitude, I am thinking in terms of of the star pairs as it relates to refraction, since their position in the sky is determined by your latitude. For example when you are closer to the south pole, some of those pair will be close to the northern horizon. I feel that should be taken into account when it comes to compatibility with different latitudes.

Another question. What will be the be the effect on accuracy when you use mag 2.5 stars instead of 4.5. How bad will the effect of refraction be?

#15 antariksha

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Posted 30 October 2019 - 11:52 PM

Agree with you. Refraction will play a significant role. When I did the verification of the resultant star pairs, I always selected the pair which was up in the horizon from the DEC table. For RA pairs, I selected that pair such that the two stars were almost equally placed from the zenith position ( of course one star would be eastward and the second one in the pair would be westward). The above choice was to minimise the refraction effect.

 

And the effect of accuracy of say 2.5 Mag vs 4.5... I have not given any thought. Let me revert on this.



#16 kel123

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Posted 31 October 2019 - 12:47 PM

So for those leaving close to the equator these pairs may not be optimal.

#17 MikeBY

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Posted 05 November 2019 - 11:58 PM

I can see that based on geographic location and time of year you will need different star pairs to use for this method. But what remains is the technique, which is straightforward and easy to implement. For those close to the equator, polar alignment is very low to the horizon so this method actually has significant advantages when it comes to atmospheric refractive influence and visibility of stars. I haven't reviewed the list published by antariksha for variety of location and suitability for various lat/lon. combinations, but I would think it wouldn't be to difficult to start with a larger table and then provide subsets based on location and time of year. 

He hasn't provided his method for pulling these pairs, but the criteria seems clear enough. The accuracy/precision depends on the angular distance between the pairs along the selected RA or DEC lines. I can see there may be difficulty with mirror flop crossing the zenith or meridian for certain types of telescopes that may be a limiting factor, but in that case, selecting stars on the same side of the zenith or meridian may be a better alternative. 

 

I'm not sure if this iterative process would be faster than a 3 star alignment or drift method, but it sure will be handy when the view toward the pole is blocked.



#18 antariksha

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Posted 08 November 2019 - 06:58 AM

So for those leaving close to the equator these pairs may not be optimal.

Thanks so much for our offline discussions. As discussed, I will increase the number of pairs. And magnitude related query is addressed now.



#19 antariksha

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Posted 08 November 2019 - 07:00 AM

I can see that based on geographic location and time of year you will need different star pairs to use for this method. But what remains is the technique, which is straightforward and easy to implement. For those close to the equator, polar alignment is very low to the horizon so this method actually has significant advantages when it comes to atmospheric refractive influence and visibility of stars. I haven't reviewed the list published by antariksha for variety of location and suitability for various lat/lon. combinations, but I would think it wouldn't be to difficult to start with a larger table and then provide subsets based on location and time of year. 

He hasn't provided his method for pulling these pairs, but the criteria seems clear enough. The accuracy/precision depends on the angular distance between the pairs along the selected RA or DEC lines. I can see there may be difficulty with mirror flop crossing the zenith or meridian for certain types of telescopes that may be a limiting factor, but in that case, selecting stars on the same side of the zenith or meridian may be a better alternative. 

 

I'm not sure if this iterative process would be faster than a 3 star alignment or drift method, but it sure will be handy when the view toward the pole is blocked.

The way the calculations were done, there is no dependency on location as such, although I had no opportunity to verify this at various latitudes. I definitely await feedback from our community on this.




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