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Drift Alignment ~ Skywatcher Star Adventurer

astrophotography beginner dslr imaging
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#1 yewyuee

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Posted 11 March 2015 - 06:34 AM

Greetings from Singapore.

 

I am considering a purchase of Skywatcher's Star Adventurer astro photo bundle (that includes the mount, EQ wedge & counterweight shaft amongst others).

 

My interest is strictly on wide field: with my Nikon D700 + lens (max focal length of 180mm).  I am totally at a loss with regards to polar alignment; specifically...

 

Singapore being situated at 1-degree N, how do I go about doing a proper drift alignment in the open "with just the DSLR + lens"; ie. without a laptop computer and telescope / guidescope.

 

I very much appreciate all the assistance.  Thank you very much.

 

 

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This is my first post on Cloudy Nights.  Mods.  Please move this to the appropriate forum should this not be the right place to ask.



#2 CharlesW

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Posted 11 March 2015 - 09:27 AM

Welcome to Cloudynights. There is a Beginning Imaging section a little farther down under Astrophotography with lots of excellent information.

Without access to a laptop you are asking the nearly impossible, I'm afraid. Drifting involves starting a long exposure on a star, pressing the direction buttons on your hand control for a specified period of time, and then comparing where the star is at the finish from where it was in the beginning.

If you can get a laptop there are a couple of apps, one of which is Backyard Nikon, which are made for your situation.

Right now I would suggest getting a good hiking compass so you can point north accurately and a digital angle gauge so you can set your latitude. That might be close enough for your work at this point.

#3 JoLo

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Posted 11 March 2015 - 09:56 AM

With a wide field lens drift alignment is not necessary.  Using the compass and setting your altitude on the mount will be good enough in most cases, although at 180mm you will be limited to 10-20 seconds.  If the Star Adventurer includes a polar scope, greater accuracy and longer imaging times are possible



#4 orlyandico

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Posted 11 March 2015 - 01:04 PM

The Star Adventurer does have a polar scope, and a pretty good one at that. But Singapore's latitude is 1 degree so Polaris is not visible even with averted imagination.

 

I don't know of any way to polar-align the Star Adventurer other than via drift alignment and the Mark 1 Eyeball.

 

http://www.astrosurf.com/re/polar.html

 

If your camera has Live View and can superimpose a crosshair on the live view, you can use the above procedure.


Edited by orlyandico, 11 March 2015 - 01:07 PM.


#5 yewyuee

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Posted 12 March 2015 - 06:25 PM

Thank you JoLo.  The "bundle" does include a polar scope but is of no use; my country being located so close to the equator.  Though I'll be very encouraged if I could get 10-20sec on my 180mm lens with just a basic alignment.

 

Greetings CharlesW.  Thank you for highlighting the "Beginning Imaging section"; had an enjoyable read through the past two days.  I'll try your method (the compass and the latitude adjustment) once I get hold of the Star Adventurer.

 

Good morning orlyandico.  I'll give some thoughts on how to "improvise a crosshair" on my DSLR's LV.  The "astrosurf link" was a good read.  Thank you.



#6 Raginar

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Posted 13 March 2015 - 08:49 PM

What about the other etchings on the polar scope? I thought they were designed for the Southern Hemisphere?

I have one. The polar scope is great. I would drift align using phd2.

#7 yewyuee

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Posted 14 March 2015 - 05:26 AM

Good morning Chris,

 

Being situated very near the equator, the polar scope will be useless.

 

My primary aim is for portability (mainstream photography being my main) and would not be travelling/hiking with laptops, etc.

 

I guess I'm resigned to using the crude compass + declination (meter) method.

 

Thank you.



#8 SteveNH

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Posted 14 March 2015 - 10:26 PM

Hi Yewyuee, in some ways being situated at almost 0-degrees latitude can simplify drift alignment a bit, but as some mention, doing it with the camera alone may not improve things as much as doing it with a guide scope to refine your aim. But you might try the following:

 

Unless you can get a focusing screen with grid lines for your D700, you will be using the border of the image frame in your viewfinder as a reference. Make sure that the camera frame's long or short edge (long edge preferred) remains perpendicular to the polar axis.

 

You must first level your mount carefully, and accurately set your polar axis angle so that it's tilted exactly 1.3 degrees, or whatever latitude you are at, from level. Then, using a corrected compass or GPS, point the polar axis as accurately as you can due north.

 

Now, find a star near the zenith (just about straight up), like Procyon, and expose it for about 10 minutes, or whatever time it takes to trail it significantly across the frame with the drive turned off. Examine the trail. If it drifts north, turn the mount head clockwise a degree or so. If it drifts south, turn the head counterclockwise. Repeat until the trail is parallel to your frame border, and you should be close enough to do several minute exposures with a 180mm lens on APS format, provided your clock drive is accurate.

 

Edit: I've corrected the camera orientation requirement with respect to the mount.


Edited by SteveNH, 15 March 2015 - 07:08 AM.


#9 Maverick199

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Posted 15 March 2015 - 12:19 PM

Greetings from Singapore.

 

I am considering a purchase of Skywatcher's Star Adventurer astro photo bundle (that includes the mount, EQ wedge & counterweight shaft amongst others).

 

My interest is strictly on wide field: with my Nikon D700 + lens (max focal length of 180mm).  I am totally at a loss with regards to polar alignment; specifically...

 

Singapore being situated at 1-degree N, how do I go about doing a proper drift alignment in the open "with just the DSLR + lens"; ie. without a laptop computer and telescope / guidescope.

 

I very much appreciate all the assistance.  Thank you very much.

 

 

Note:

 

This is my first post on Cloudy Nights.  Mods.  Please move this to the appropriate forum should this not be the right place to ask.

Since your interest is strictly widefield with your DSLR and Lens, you may be better served with a Skytracker or similiar. Having an EQ mount may limit your latitude to 10 deg. North unless the one you are looking for can go all the way down to 0 N.



#10 gvk

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Posted 15 March 2015 - 01:45 PM

The wedge that is available for the Skywatcher Star Adventurer goes to zero latitude, or even a bit below. I adjusted mine to horizontal, and moved it up and down a bit, while I was aligning the polar scope with the RA axis. However, at 1-degree latitude,  a wedge may not be necessary if the tripod legs can be adjusted to set the latitude, though that might make small changes difficult when doing drift alignment.



#11 yewyuee

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Posted 17 March 2015 - 06:58 AM

Thank you Maverick199 and gvk.

Yes.  The Star Adventurer can indeed go down to 1º-latitude.  My bundle includes the wedge.

 

SteveNH.

That's a very detailed procedure; thank you very much.

Just to be safe (sorry for my very basic query), when you mentioned "make sure that the camera frame's long or short edge (long edge preferred) remains perpendicular to the polar axis", would my camera be oriented in the landscape or portrait mode so that the "preferred long edge of my DSLR (focusing screen) is perpendicular to the polar axis"?



#12 SteveNH

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Posted 17 March 2015 - 02:45 PM

Hi yewyuee, I hope the procedure helps - even without drift alignment though, with the initial setup of your mount using GPS, you should be fine especially for your shorter lenses (wider angles).

 

By long edge, I meant that your camera base, in landscape mode, should always be perpendicular to the polar axis. This way, when you are actually polar aligned, stars near the equator passing overhead should trail in straight lines that are parallel to the top or bottom of your camera frame, thus making it easier to check for proper alignment. Again, if you can get grid lines projected on your viewscreen, then you can use those to easily check the deviation of the star trail if there is drift. When you are aligned, the star trail will have no drift  - it will be exactly parallel to your grid lines.

 

If you ever do get a small refractor or spotting scope (or just a longer lens) to refine your aim, you can adjust your polar axis inclination by aiming your camera at a rising star near the equator like Spica or Denebola, and let it drift through the frame, adjusting the polar axis tilt in small increments until the trail lines up with the landscape grid lines (drifts north - tilt down, drifts south, tilt up). But for your current setup, if you can use a good level to set your polar angle to 1.3°, that should work fine. You should use the longest lens you have, and you might simply try random stars that are actually closer to the equator than the two mentioned above, as long as they are rising, at around 10 or 15 degrees elevation, if you have such a view.


Edited by SteveNH, 17 March 2015 - 02:57 PM.


#13 yewyuee

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Posted 18 March 2015 - 03:49 AM

Thank you very much for the detailed explanation, SteveNH; much appreciated.


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