Finding Polaris?

Started 9 months ago | Questions
landscaper1
landscaper1 Veteran Member • Posts: 4,899
Finding Polaris?

I've owned an iOptron SkyTracker Pro for some time and would like to be able to use it.

When I last made the effort (some time ago) I gave up because I found it all but impossible to locate Polaris through the optical sight in the SkyTracker.  To begin with, because of light and air pollution I rarely can see Polaris even though I know the approximate area in the sky where it's located.

Does anyone have a suggestion on how to get around this obstacle?  Or am I doomed to forego using a tracker anywhere other than exceptionally clear night skies?

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hha1 Junior Member • Posts: 27
Re: Finding Polaris?
2

landscaper1 wrote:

I've owned an iOptron SkyTracker Pro for some time and would like to be able to use it.

When I last made the effort (some time ago) I gave up because I found it all but impossible to locate Polaris through the optical sight in the SkyTracker. To begin with, because of light and air pollution I rarely can see Polaris even though I know the approximate area in the sky where it's located.

Does anyone have a suggestion on how to get around this obstacle? Or am I doomed to forego using a tracker anywhere other than exceptionally clear night skies?

I have the same problem, that I can't see Polaris with the unaided eye from my backyard, and I have the Skytracker with the pole finder scope. First I make sure  my tripod is level. Then I set the Skytracker to approximately the right declination using the declination scale. Then I use a magnetic compass to turn the Skytracker horizontal axis to  approximately N. Polaris is then typically visible  in the 6 degree FOV of the pole finder scope. Center and you are done.  In California the local declination is about 15 degrees, so N is 345 degree magnetic.

hha

myb17 Junior Member • Posts: 26
I use an app

My favorite, on the iphone, is Redshift.

It will follow the sky.

landscaper1
OP landscaper1 Veteran Member • Posts: 4,899
Re: I use an app

myb17 wrote:

My favorite, on the iphone, is Redshift.

It will follow the sky.

And how does that help me to aim the tracker's optical sight?

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mermaidkiller Senior Member • Posts: 1,088
Re: I use an app
1

It is damn simple when you are in the northern hemisphere. Polaris has about magnitude +2, so it is easy to spot, even in well light polluted cities.

It is always above the northern horizon, the further north, the higher, its altitude in degrees equals your latitude.

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landscaper1
OP landscaper1 Veteran Member • Posts: 4,899
Re: I use an app

mermaidkiller wrote:

It is damn simple when you are in the northern hemisphere. Polaris has about magnitude +2, so it is easy to spot, even in well light polluted cities.

It is always above the northern horizon, the further north, the higher, its altitude in degrees equals your latitude.

Maybe it's damn simple for you, and maybe you assume too much.  I'm 74 and my eyes aren't what they used to be.  Oh, and I'm well acquainted with the constellations and how to locate the approximate area where Polaris is located, but approximate is good enough for a tracker.

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swimswithtrout Veteran Member • Posts: 3,774
Re: I use an app

I have to agree with Mermaid killer...

Polaris is mag 2.0. Unless you live in a Bortle 9+ zone, it is easily visible. I had no problem at all in a Bortle 8 zone. In, fact a bit of LP makes it easier to find, compared to the multitude of stars visible at my Bortle 2 dark site.

DLutzer
DLutzer Regular Member • Posts: 261
Re: I use an app
1

It may help to light acclimate your eyes first. Make sure you are in the dark with no lights or just close at least one eye for 5-10 minutes. This will help you see better. If you need light to see where you are going use red it helps preserve your night vision

once you know the degree Polaris should set up your tripod, ensure that it is level, and point north. Keep in mind it is the tail end of the Little Dipper and Cassiopeia will be on the other side of it. You can also try to use the mid point of Cassiopeia. Should be a straight line from there.

another trick is to use the Big Dipper:

To locate Polaris, all you have to do is to findthe Big Dipper pointer stars Dubhe and Merak. These two stars outline the outer part of the Big Dipper's bowl. Simply draw a line from Merak through Dubhe, and go about five times the Merak/Dubhe distance to Polaris. If you can find the Big Dipper, you can find Polaris.

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Allen Moss Regular Member • Posts: 229
Re: Finding Polaris?
1

Get to the site before dark.  Get the tracker pointed as best you can to where Polaris should be.  As twilight approaches Polaris will be visible first since it’s very bright.  You should have your best chance for alignment.  Good luck!

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mermaidkiller Senior Member • Posts: 1,088
Re: Finding Polaris?

Here an image, showing the method like DLutzer says.

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landscaper1
OP landscaper1 Veteran Member • Posts: 4,899
Re: Finding Polaris?

mermaidkiller wrote:

Here an image, showing the method like DLutzer says.

Thanks, but I've known this since I was a kid.

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bmike
bmike Senior Member • Posts: 2,332
Re: Finding Polaris?

How long or wide of a lens are you using?

When I haven't been able to see Polaris with wider lenses I did the following:

1. Level tripod.

2. Adjust declination based on your latitude.

3. Point North with compass (adjust for magnetic declination). My tracker has a declination / compass mount for it.

Then, if using a long lens, or needing really long exposures, once it gets dark sight through the scope... but if you are in heavily light polluted areas a long exposure might just blow out your image.

I'm using a Vixen Polarie - so I also open SkyWalk2, search for Polaris, then put the phone on the back of the mount, and tweak (if needed). Now that I have a polar scope for it I do steps 1-3 and sight through (assuming I can see Polaris...)

You might have to wait until you can travel a bit and get out of the city though, if you are having trouble seeing.

landscaper1
OP landscaper1 Veteran Member • Posts: 4,899
Re: Finding Polaris?

bmike wrote:

How long or wide of a lens are you using?

When I haven't been able to see Polaris with wider lenses I did the following:

1. Level tripod.

2. Adjust declination based on your latitude.

3. Point North with compass (adjust for magnetic declination). My tracker has a declination / compass mount for it.

Then, if using a long lens, or needing really long exposures, once it gets dark sight through the scope... but if you are in heavily light polluted areas a long exposure might just blow out your image.

I'm using a Vixen Polarie - so I also open SkyWalk2, search for Polaris, then put the phone on the back of the mount, and tweak (if needed). Now that I have a polar scope for it I do steps 1-3 and sight through (assuming I can see Polaris...)

You might have to wait until you can travel a bit and get out of the city though, if you are having trouble seeing.

Mike,my problem is with the SkyTracker Pro's own optical (1x) sight.  It has a fairly narrow field of view.

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stargazer ch Forum Member • Posts: 60
Re: Finding Polaris?

Following on from bmike‘s suggestions:

  • level the tripod
  • set the angle on your tracker to your geographical latitude. 
  • at Night, Point your tracker roughly towards north.
  • while looking through the finder scope, Turn the tracker left/right around the vertical axis until you see a reasonably bright star. Chancen are high this is Polaris. 
  • fir fine-tuning, use an app (I use the native app from ioptron) to put Polaris at the right place in the circle you may see in your finder scope.

That‘s at least how I manage to find Polaris with my skytracker. 
Lastly - don’t overdo polar alignment if you only want to image at small focal lengths(say <85mm). And as long as exposure time is small (<30 sec) a rough alignment is more than enough to produce good results.

Just my 50c,

Michael.

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landscaper1
OP landscaper1 Veteran Member • Posts: 4,899
Re: Finding Polaris?
1

stargazer ch wrote:

Lastly - don’t overdo polar alignment if you only want to image at small focal lengths(say <85mm). And as long as exposure time is small (<30 sec) a rough alignment is more than enough to produce good results.

Just my 50c,

Michael.

Now that's something I haven't read before.  Interesting, inasmuch as I'm extremely unlikely to be shooting anything longer than 35mm, and then never more than 50mm.

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bmike
bmike Senior Member • Posts: 2,332
Re: Finding Polaris?
1

landscaper1 wrote:

stargazer ch wrote:

Lastly - don’t overdo polar alignment if you only want to image at small focal lengths(say <85mm). And as long as exposure time is small (<30 sec) a rough alignment is more than enough to produce good results.

Just my 50c,

Michael.

Now that's something I haven't read before. Interesting, inasmuch as I'm extremely unlikely to be shooting anything longer than 35mm, and then never more than 50mm.

Polar scope is good for long lenses, less helpful for wide. Certainly you want to get it as good as you can - but with light pollution likely to lead to shorter exposure and a wider lens - just point it properly north, set the declination and take some test shots.

I managed 120s exposure at a dark site only using latitude and compass, and eventually the eye peephole (not a scope) on my tracker to produce this image, which is a mosaic - shot @ 22mm on a crop. I couldn't site Polaris when setting up - daylight + tree - I did eventually use the peephole when it got dark enough - which is about a 1cm diameter hole you sort of one eye sight through on my tracker...

Muti image mosaic - tracked, stacked, stitched

30s exposures @ 85mm on my 6dmk2 - (I would have shot longer but I left the intervalometer at home). Same process for alignment - angle, north, and in this case sighting through the peephole.

stacked exposures

BlackgumNate Contributing Member • Posts: 634
Re: Finding Polaris?

Can you see Polaris then? Assuming you can, point a green laser at it (I have a little clamp that i clip on a tripod leg) and then look for the laser in your polar scope. As soon as you see it in your polarscope it'll stand out from there.

Depending on how far off your alignment is starting out, and brightness or darkness of skies, it can be maddening to find polaris through the scope.

Nate

Bill Ferris
Bill Ferris Veteran Member • Posts: 6,066
Re: Finding Polaris?

If you're able to see the Big Dipper, you can use the front "bowl" stars as pointers to Polaris.

Courtesy: Earth and Sky

If the local night sky is too bright to see the Big Dipper, there are mechanical approaches you can apply to get close.

Polaris is about 0.9 degree from the celestial north pole. You can dial-in the approximate angle of Polaris above your horizon by setting the finder at an angle equal to your local latitude. If you're at 40° N latitude, set the finder's tilt angle to 40°. Set it to 60°, if you're at that northerly latitude.

To finish an approximate alignment, look up the magnetic offset of North on a compass from true North for your location. With this number, you can use a compass as a reference to rotate the finder around your horizon until it's pointing toward magnetic North. Then rotate the finder according to your local magnetic offset for a more accurate alignment.

You should be roughly aligned and, unless you're using very long focal lengths, should be able to make tracking exposures up to some reasonable length of time.

If you need or want a more precise alignment and are unable to see Polaris, Google "declination drift" method of polar alignment. The rough alignment I've described is a good start to that process.

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nick lamendola Regular Member • Posts: 261
Re: Finding Polaris?

Can you see Polaris by the naked eye, but are having a problem finding it it the polar scope?

This has happens to me occasionally, especially if I'm at a different location than I normally use or if I'm at a darker site where there are more star visible than I'm used to.  When this happens I remove the tracker from the tripod and hold the tracker in my hands and use finder scope like a telescope and scan around the sky to find Polaris that way first. This lets me get an idea of how bright Polaris will be in the finder scope and what it looks like, and makes it easier to find Polaris after I put the tracker back on the tripod.  It works for me anyway.

Good luck,

Nick

swimswithtrout Veteran Member • Posts: 3,774
Re: Finding Polaris?

mermaidkiller wrote:

Here an image, showing the method like DLutzer says.

If the OP can't even see Polaris, than this won't make any difference, because all of the stars are the same brightness as Polaris or fainter, which would equate to a Bortle 11 zone

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