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What Do You Do If You Can't See North?

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#1 godelescher

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Posted 29 November 2019 - 06:16 PM

My scope set up area has a large tree directly North of me. There's nowhere else to set it up, (C8 on an advanced GT), so how do I polar align it? It's strictly for visual use and I've been making do with, "North is over there", but at some point, I'd like to avail myself of the go-to capabilities of this mount without having to hunt for my desired object.

 

What's the answer that doesn't cost me another $300?


Edited by godelescher, 29 November 2019 - 06:18 PM.


#2 Barlowbill

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Posted 29 November 2019 - 06:24 PM

A compass and then figure out where "true" north is from your location.  Then mark it somehow.  A big red arrow?


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#3 John Rogers

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Posted 29 November 2019 - 06:31 PM

Star-drift method.  Does not cost anything but a little time:  http://www.astrosurf.com/re/polar.html

 

Works great!


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#4 desertstars

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Posted 29 November 2019 - 06:48 PM

My scope set up area has a large tree directly North of me. There's nowhere else to set it up, (C8 on an advanced GT), so how do I polar align it? It's strictly for visual use and I've been making do with, "North is over there", but at some point, I'd like to avail myself of the go-to capabilities of this mount without having to hunt for my desired object.

 

What's the answer that doesn't cost me another $300?

Been there, done that, a huge mesquite tree between me and Polaris. I've been getting a good enough polar alignment (for visual observing) using a compass and my local geomagnetic declination. Go here to find that number:

 

https://www.ngdc.noa.../magcalc.shtml?

 

I turn the compass ever so slightly so the needle points to the value of the geomagnet declination. The marker for North on the compass is then pointing the way I need to align the telescope mount.


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#5 Astroman007

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Posted 29 November 2019 - 06:49 PM

"What do you do if you can't see north?"

 

"All the good stuff's in the south." ~Bart J. Bok.


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#6 godelescher

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Posted 29 November 2019 - 07:07 PM

It seems counterintuitive to me that I can't triangulate polar North without actually seeing it. Maybe "triangulate" is the wrong word here, but, hypothetically, if I know where stars are at a specific time, and then identify where they are a specified time later, I should be able to deduce their axes, right?

 

The world of astronomy is filled with hyper-intelligent nerds. Can it really be true that the drift method is the only alternative to finding polar North when it's not visible? It seems, I don't know, kind of ghetto.

 

(Granted, I asked for the "free" solution, so maybe I'm okay with ghetto)


Edited by godelescher, 29 November 2019 - 07:09 PM.


#7 rk2k2

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Posted 29 November 2019 - 07:27 PM

Simple method as described to me by Kent at ES.  Eyeball your mount as near north as you can.  Do a GOTO some bright star you are able to see.  Adjust your ALT and AZ until the star is centered.  You now have a PA suitable for observational use.  That assumes no or close to no cone error.



#8 ButterFly

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Posted 29 November 2019 - 07:28 PM

Close enough is good enough for goto.  Tracking is where polar alignment matters, so offset your compass and use the latitude setting circle.  If it realy bothers you, try CPWI from your computer.  It can do the all star polar alignment of the Nexstar+ controllers within the software, but then you are tied to the computer for gotos.  That may not be so bad in your yard.

 

A nice trick I learned from the AVX.  It goes to that first star based on your input time, lat, and long.  It assumes perfect polar alignment.  Set your time, lat, and long correctly, then "polar align" using that first star.  It works rather well.


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#9 godelescher

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Posted 29 November 2019 - 07:49 PM

First, I appreciate the responses and there are a couple of things mentioned so far that I'm going to try. Second, I have a toothache and can't go to the dentist until Monday, so I'm medicating with scotch (It worked for my grandparents), so I apologize in advance for anything I might write that doesn't come off as intended. (My computer should have a breathalyzer).

 

I'm a cabinet maker, (By the way, if anyone wants a custom made telescope case, get in touch with me). If I want to know the width of a raised panel, it's a simple formula: The width of the opening, plus the overlay, minus the width of the stiles, plus the tenon length, minus the expansion.

 

I'm just surprised that the solution to this dilemma is the equivalent of saying, "I need a panel about yay big, so I'll make it too large then sneak up on the right size." It's not math. It's not science. It's a game of astronomical Marco Polo.

 

(Also, when I drink scotch, I have a tendency to overuse parentheses)


Edited by godelescher, 29 November 2019 - 07:50 PM.

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#10 Alex McConahay

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Posted 29 November 2019 - 08:00 PM

>>>>>> It's a game of astronomical Marco Polo.

 

Marco Polo went to China to find a compass so he could polar align his mount. 

 

Alex


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#11 Alex McConahay

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Posted 29 November 2019 - 08:10 PM

OKAY, more serious now.....

 

In the first place, the goto the first star, and then adjust the mount to it works pretty well. Probably about as well as being able to see Polaris, which itself is not at the north pole, but a little off. Same for the compass and such. 

 

Secondly, your mount can correct its goto function for your error in polar alignment. When you build a celestial model (which is what you are doing when you do a two or three star alignment), the computer in your handpaddle figures how far you are from true north alignment, and throws that into later calculations. 

 

Thirdly, your mount does not need to be all that well aligned to track a star. Close enough is really good enough to follow a star for much longer than you might be willing to look at it.

 

And as far as finding the star, your goto will probably get you there within reason even if you are a few degrees off north. At most, use the handpaddle's "Search" function, and the mount will start making little excursions as you watch until the star you wanted pops up. 

 

Furthermore, you probably have a little finder something attached to that scope. If your goto's are not quite where you like them, goto a bright target near your desired target, center that using your finder and such, synch, and then go to the desired target. 

 

Finally, if you want the kind of precision you demand in your carpentry, feel free to do a drift. It really does not take that long. 

 

I hate Scotch. The way it smells, the way it tastes. It may be good for the pain, but there are other ways that they do not involve that smell and taste. 

Alex


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#12 ButterFly

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Posted 29 November 2019 - 08:13 PM


 

I'm just surprised that the solution to this dilemma is the equivalent of saying, "I need a panel about yay big, so I'll make it too large then sneak up on the right size." It's not math. It's not science. It's a game of astronomical Marco Polo.

 

(Also, when I drink scotch, I have a tendency to overuse parentheses)

The issue is the encoders - absolute referenced encoders are very expensive.  There are external lines that are used to reference these encoders.

 

Say you want to measure 16" to within 1/32".  However, you only have markings on your ruler between 15 and 17".  The zero is there too, but it's placed within 1/2" only.  What now?  That's the mathematical problem being solved.  You "measure" 16" in two perpendicular directions and correct the zero.

 

hen I drink scotch, I have a tendency to overuse Scotch.


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#13 godelescher

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Posted 29 November 2019 - 08:57 PM

You "measure" 16" in two perpendicular directions and correct the zero.

Measure from each wall a rough halfway point and make a mark, then measure the distance between them. That makes sense to me.

 

I'm going to try several suggestions mentioned above.



#14 SloMoe

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Posted 29 November 2019 - 10:19 PM

You have a digital level? 

That and a compass, your latitude is the angle needed and compass point to the tree, think about it. 

 

It's not complicated at all.

 

I polar align all the time for solar viewing, no stars at all to set by for solar viewing,


Edited by SloMoe, 30 November 2019 - 09:02 AM.


#15 SloMoe

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Posted 29 November 2019 - 10:23 PM

Or if yu're using auto align, use the tree as north then when the scope picks your first alignment star confirm it with your phone app, center the star and press enter, do the same for the second requested star, now you're aligned.



#16 NorthernlatAK

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Posted 30 November 2019 - 12:12 AM

Use solar noon during the day and mark it. Use a plumb bob at exactly solar noon and mark the shadow of your line. This will point at true north. Use your latitude for altitude. Voila...

#17 SloMoe

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Posted 30 November 2019 - 09:13 AM

Since getting into basic solar viewing, there are no stars to guide my ship by,

 

I use this compass and this digital inclinometer, and since there isn't enough iron in my scope for this inclinometer's base magnet to stick to, I filed out my front top finder shoe so this little thing could fit in and then tighten the thumb screw just enough to hold it there, and set the angle of the mount head using my latitude, 47.7°

 

The basic RA clock drive will follow the Sun for about an hour before I have to tweek it a bit, 

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Edited by SloMoe, 30 November 2019 - 09:14 AM.

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#18 t_image

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Posted 30 November 2019 - 10:17 AM

You are not in the most precise forum where people actually own the type of mount you do,

https://www.cloudyni...estron-nexstar/

 

so there is a lot of noise here in this thread with inefficient advice.

  • The mount has a computer in it for a reason,

you might as well use it

rather than a compass for which the polar and magnetic directions differ

and drift that is barbaric for having the expensive tool of the mount you have.

  • You could bother to read the manual to see there is a physical polar alignment function after you've built a simple sky model with alignment stars as Alex mentioned.

 

With no compass nor drift I'm easily able to align my similar AVX [for imaging] that only has a Southern view.

 

As Butterfly also mentioned with the first alignment star, you can also quickly point your mount/tripod Northernly using the Sun(if have necessary protective filter) during the daytime or Moon,

just select solar system align and the scope will point to where the object is supposed to be. Rotate your tripod/tilt lat. appropriately so you are close/there.

You can always shut off, set indexes, and have it slew again to get more precise. Turn off, then leave out till night to perfect with stars..


Edited by t_image, 30 November 2019 - 10:18 AM.


#19 spereira

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Posted 30 November 2019 - 12:14 PM

I looked up the Celestron Advanced Series GT, and I see the Manual and also an Addendum concerning the Hand Controller are available on the Celestron site:

https://www.celestro...m/pages/manuals

 

Both these documents describe performing the mount alignment procedure with a few different options.

 

I believe that using your "North is about there" and then performing an alignment procedure should be doable.  Have you tried this?

 

smp


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#20 Tom Stock

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Posted 30 November 2019 - 05:44 PM

My scope set up area has a large tree directly North of me. There's nowhere else to set it up, (C8 on an advanced GT), so how do I polar align it? It's strictly for visual use and I've been making do with, "North is over there", but at some point, I'd like to avail myself of the go-to capabilities of this mount without having to hunt for my desired object.

 

What's the answer that doesn't cost me another $300?

Compass.  Align to north as close as you can accounting for magnetic declination (variation).  Then set the correct latitude on your mount, and make sure the tripod is level.

 

Then, if you need better accuracy, you can do a drift alignment.  I like this explanation:

 

https://www.youtube....h?v=4OtelWKWntc



#21 Myk Rian

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Posted 30 November 2019 - 07:12 PM

Use solar noon during the day and mark it. Use a plumb bob at exactly solar noon and mark the shadow of your line. This will point at true north. Use your latitude for altitude. Voila...

^^^this^^^
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#22 NYJohn S

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Posted 30 November 2019 - 10:14 PM

I'd like to avail myself of the go-to capabilities of this mount without having to hunt for my desired object.

Are you adding calibration stars after the initial alignment? Whether you can see Polaris or not if you don't add calibration stars the goto's will be off with that mount. I have the same mount. Point the mount north & set the latitude for your location (Close is good enough). Do a 2 star alignment. The mount is usually way off on the first star. Don't worry about it. Just make sure you pick a star you are confident you can identify and center it. Do the same for the second star. Then add 2-3 calibration stars. Your Goto's will be spot on. Make sure the calibration stars are on the opposite side of the meridian from your alignment stars. Read the "Improving Pointing Accuracy" in the manual. It's all there. I can't see Polaris in the summer when there are leaves on the trees and my goto's are right on the money once I add calibration stars.


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#23 Greyhaven

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Posted 01 December 2019 - 02:15 PM

 Great site for determining local noon and other solar values. Use map to plot your Lat. and Lon.

Grey



#24 Starman1

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Posted 01 December 2019 - 06:42 PM

My scope set up area has a large tree directly North of me. There's nowhere else to set it up, (C8 on an advanced GT), so how do I polar align it? It's strictly for visual use and I've been making do with, "North is over there", but at some point, I'd like to avail myself of the go-to capabilities of this mount without having to hunt for my desired object.

 

What's the answer that doesn't cost me another $300?

Free compass app on your smart phone.

They tell you which is magnetic and which is geographic north. 

You want geographic north.

point the mount at geographic north.  Close enough.

 

Free level app on your smart phone.

Place phone on mount and elevate using the altitude screw until the angle matches your latitude.

Close enough.

 

Align mount with scope on it and enjoy. 


Edited by Starman1, 01 December 2019 - 06:43 PM.


#25 SloMoe

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Posted 01 December 2019 - 06:50 PM

Free level app?

 

That's one I've got to get.

 

Thanks Don!




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