Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Polar Alignment in Southern Hemisphere

Imaging Polar Alignment Mount Equipment Astrometry Accessories Astrophotography Beginner
  • Please log in to reply
16 replies to this topic

#1 Sindaco

Sindaco

    Lift Off

  • -----
  • topic starter
  • Posts: 8
  • Joined: 12 Apr 2020

Posted 19 July 2021 - 11:52 PM

Hello Guys,

I am located in the equator and just getting started in astrophotography. I was wondering if its possible to drift align using software on a star tracker. 

My equipment is as follows:

Ioptron Sky guider pro

ASI 120 mini with guide scope

Redcat51 

Sony A6400

 

Thanks in advance 



#2 AnakChan

AnakChan

    Apollo

  • -----
  • Posts: 1,447
  • Joined: 01 Sep 2014
  • Loc: Oz

Posted 20 July 2021 - 12:44 AM

Would you be able to install an iPolar into your Sky Guider pro?

If you want to drift align, I'm sure you can, but I'd think the iPolar would be faster.


Edited by AnakChan, 20 July 2021 - 12:44 AM.

  • Sindaco likes this

#3 Sindaco

Sindaco

    Lift Off

  • -----
  • topic starter
  • Posts: 8
  • Joined: 12 Apr 2020

Posted 20 July 2021 - 01:25 AM

Im not able to see Polaris from my location since its right at the heroization. So ipolar does not work that well for me.



#4 luxo II

luxo II

    Skylab

  • ****-
  • Posts: 4,308
  • Joined: 13 Jan 2017
  • Loc: Sydney, Australia

Posted 20 July 2021 - 01:35 AM

As I am in Sydney, setting up in suburbia means the south celestial pole and Octans are a big wide swathe of... grey nothingness.

 

When my mount is in equatorial mode (not often, I'll admit):

 

1. I use the dec circle first to get a rough azimuth alignment - star near the horizon east/west to set the azimuth, and clinometer to set the altitude.

 

2. From that I then to an initial alignment with the AZEQ6 mount.

 

3. Then use the Synscan handset to refine the altitude/azmith adjustments as described in section 6.8 of the Synscan manual (version 5).

 

I'm fairly sure a lot of people don't realise the Synscan handsets have that capability.

 

Plate-solving is faster (using SharpCap) but I'm not quite set up to do that yet, and I don't need it often.


Edited by luxo II, 20 July 2021 - 01:37 AM.


#5 Sindaco

Sindaco

    Lift Off

  • -----
  • topic starter
  • Posts: 8
  • Joined: 12 Apr 2020

Posted 20 July 2021 - 02:10 AM

Thanks for the response. I couldn't understand most of what you said since im a newbie :D

So in your opinion, would i be able to drift align using a star tracker like sky guider pro? 



#6 michael8554

michael8554

    Apollo

  • -----
  • Posts: 1,263
  • Joined: 19 Aug 2020
  • Loc: Wiltshire UK

Posted 20 July 2021 - 07:20 AM

The Static Polar Alignment (SPA) and Polar Drift Alignment (PDA) tools in PHD2 were developed by an Australian to aid Southern Hemisphere PA.

 

He has made some YouTube videos on how to use them.



#7 luxo II

luxo II

    Skylab

  • ****-
  • Posts: 4,308
  • Joined: 13 Jan 2017
  • Loc: Sydney, Australia

Posted 20 July 2021 - 07:31 AM

would i be able to drift align

It’s the slowest way. I do steps 1-2 in 5 minutes, step 3 in another 5.

With a camera you could align using plate-solving with SharpCap in less time.

Edited by luxo II, 20 July 2021 - 07:33 AM.


#8 philinbris

philinbris

    Viking 1

  • *****
  • Posts: 585
  • Joined: 10 Jan 2020
  • Loc: Brisbane, Australia

Posted 21 July 2021 - 05:42 AM

SharpCap and its Polar alignment function works great for me here in Brisbane in Bortle 6+ skies.

I use my ASI533MCP in my 8" newt and that works fine - that combination works out at 0.65 Deg FOV.

All done in about 5 mins max.

Cheers


  • DuncanM likes this

#9 Phil Sherman

Phil Sherman

    Gemini

  • *****
  • Posts: 3,491
  • Joined: 07 Dec 2010
  • Loc: Cleveland, Ohio

Posted 22 July 2021 - 12:18 PM

You can drift align from almost anywhere on our planet that's not near the poles. The two alignment points are on the celestial equator near the meridian and 20 - 30 degrees above the E orW horizon. This is easy to do with your imaging camera and requires no additional software.

 

1. Level the tripod before attaching the mount. This disconnects the adjustments from each other.

2. Polar align your mount using a compass and the mount's altitude scale.

3. Point your scope to the first alignment point. Set tracking to sidereal, slew rate to 1x sidereal, disable guiding.

4. Start a 70 second exposure. Let the mount track for 5 seconds then slew E for 30 seconds, then slew W for 35 seconds.

5. Examine your image. You should see stars (5 sec tracked) with a "V" shaped tail that ends just past the star.

6. Adjust the azimuth of the mount to make the V collapse into a line that passes through the center of the star.

 

Repeat steps 4-6 until you have the mount aligned. Until you learn which way to move the mount, the first adjustment should be two full turns of the adjustment screw. This will make it easy to determine which way to move the mount to align it. Once done, point the scope to the second alignment point and repeat the process to adjust the altitude. If, while adjusting the mount, the V moves to the opposite side of the star, you moved it too far.

 

If the tripod wasn't perfectly leveled, there will be some interaction between the adjustments. Repeating the alignment process will improve the alignment. The test can be made more sensitive by using a 130 second exposure and 60, 65 second slews. Few mounts in the under $10k price class have adjustments fine enough to support the more sensitive test.



#10 Bowlerhat

Bowlerhat

    Surveyor 1

  • *****
  • Posts: 1,571
  • Joined: 05 Jun 2019
  • Loc: Melbourne, Australia

Posted 22 July 2021 - 10:14 PM

This is a rough alignment guide for skywatcher star adventurer, but I think it'll work as well.

https://www.youtube....h?v=9SZ8Otnr3rs



#11 licho52

licho52

    Vostok 1

  • -----
  • Posts: 121
  • Joined: 15 Dec 2020

Posted 22 July 2021 - 10:41 PM

Nina's 3-point polar alignment plugin works very well for me.



#12 TelescopeGreg

TelescopeGreg

    Gemini

  • -----
  • Posts: 3,424
  • Joined: 16 Jul 2018
  • Loc: Auburn, California, USA

Posted 22 July 2021 - 10:48 PM

Does your mount even "allow" working close to the equator?  My AVX is rated from 7 degrees to 77 degrees latitude.



#13 kel123

kel123

    Vanguard

  • -----
  • Posts: 2,073
  • Joined: 11 May 2019

Posted 22 July 2021 - 11:10 PM

I think most posters do not understand the predicament of the OP but it is also the fault of the OP as the title of the thread doesn't tell the correct story. To avoid the confusion, the OP should edit the title. Something like "polar alignment at the equator or near the equator" as the case may be.

The OP is near the equator and cannot see any of the poles, though maybe slightly on the southern side. Hence, iPolar sharpcap, static polar alignment or drift polar alignment is not going to work.

The only method that will work here is old fashioned declination drift alignment. It is not very difficult and after a few times, you will find it easier and faster. It involves a star close to the junction of the celestial equator and the merdian, which is roughly directly overheated for the OP and a star about 30 degrees high in the eastern or western horizon.

The overhead star is used for azimuth adjustment while the star close to the horizon is for altitude adjustment.

I want to make this very basic for a newbie. Point to the overhead star, if it drifts downward, you adjust your azimuth it to the east and if it drifts upwards, you adjust it to the west until it is moving on a straight line across your screen. Go to the star new the horizon, if it it drifts upwards, you adjust your altitude down and if it drifts downward, you adjust your latitude up. Go back to the star on the horizon and see if there is any drift and repeat. Of course you should level your mount first. And mind you the directions can be opposite depending on your orientation and if you adjust and it keeps drifting faster in the same direction,just know that you should instead be making an opposite adjustment.

Just think about these and understand the principle of drift alignment first as there tend to be information overload on threads like this that can confuse you. Hence, I made the idea very simple.

The easiest method by far is PHD2 drift alignment but that will require you to get a guide camera and connect a laptop to the guide port
  • Bowlerhat likes this

#14 celeron787

celeron787

    Vostok 1

  • -----
  • Posts: 105
  • Joined: 07 Feb 2020
  • Loc: Singapore

Posted 23 July 2021 - 07:22 AM

You can drift align from almost anywhere on our planet that's not near the poles. The two alignment points are on the celestial equator near the meridian and 20 - 30 degrees above the E orW horizon. This is easy to do with your imaging camera and requires no additional software.

 

1. Level the tripod before attaching the mount. This disconnects the adjustments from each other.

2. Polar align your mount using a compass and the mount's altitude scale.

3. Point your scope to the first alignment point. Set tracking to sidereal, slew rate to 1x sidereal, disable guiding.

4. Start a 70 second exposure. Let the mount track for 5 seconds then slew E for 30 seconds, then slew W for 35 seconds.

5. Examine your image. You should see stars (5 sec tracked) with a "V" shaped tail that ends just past the star.

6. Adjust the azimuth of the mount to make the V collapse into a line that passes through the center of the star.

 

Repeat steps 4-6 until you have the mount aligned. Until you learn which way to move the mount, the first adjustment should be two full turns of the adjustment screw. This will make it easy to determine which way to move the mount to align it. Once done, point the scope to the second alignment point and repeat the process to adjust the altitude. If, while adjusting the mount, the V moves to the opposite side of the star, you moved it too far.

 

If the tripod wasn't perfectly leveled, there will be some interaction between the adjustments. Repeating the alignment process will improve the alignment. The test can be made more sensitive by using a 130 second exposure and 60, 65 second slews. Few mounts in the under $10k price class have adjustments fine enough to support the more sensitive test.

Interested in this since I'm located at the equator too and having difficulties getting reliable polar alignment with my star adventurer.

My setup is very similar to OP's: star adventurer, star adventurer tripod with extension, redcat51, sony a6400

 

So far I've been using the DARV method with my camera with mixed results.

I was wondering if the star adventurer's buttons and dials could be adapted to DARV.

Idea is set star adventurer to South hemisphere so it rotates W->E, set it at 2x speed for 60sec

After 60sec, set back to North hemisphere so it rotates E->W also at 2x speed for 65sec. That would form that "V shape".



#15 Phil Sherman

Phil Sherman

    Gemini

  • *****
  • Posts: 3,491
  • Joined: 07 Dec 2010
  • Loc: Cleveland, Ohio

Posted 24 July 2021 - 12:11 PM

Interested in this since I'm located at the equator too and having difficulties getting reliable polar alignment with my star adventurer.

My setup is very similar to OP's: star adventurer, star adventurer tripod with extension, redcat51, sony a6400

 

So far I've been using the DARV method with my camera with mixed results.

I was wondering if the star adventurer's buttons and dials could be adapted to DARV.

Idea is set star adventurer to South hemisphere so it rotates W->E, set it at 2x speed for 60sec

After 60sec, set back to North hemisphere so it rotates E->W also at 2x speed for 65sec. That would form that "V shape".

For this method to work, you need at least 60 seconds of tracking to make V tail. The first E slew normally stops the mount from tracking, keeping the gears engaged when the W slew starts. Your mount doesn't have a mode that doesn't track which will complicate the process. A further complication will be changing the mount's settings without causing vibrations that will distort the image. A final issue will be using a 2x sidereal speed which will make that leg of the V tail much fainter than the other leg.

 

You don't actually need the full V tail for this method to work. A better approach might be:

1. Set the rate to sidereal to track for your hemisphere.

2. Start an 90 second exposure and let the mount track for 5 seconds.

3. Switch to the other hemisphere and let the mount track for 60 seconds.

4. Use the slew button to return to the star - just a fraction over 10 seconds

5. Let the mount track for another 15 seconds.

 

You should see the bright star with the first tail attached to it. The second tail will be a short segment above or below the star. The critical part of this will be the length of the high speed slew. I'm not sure aboout the length of the high speed slew, you may need to adjust it.



#16 celeron787

celeron787

    Vostok 1

  • -----
  • Posts: 105
  • Joined: 07 Feb 2020
  • Loc: Singapore

Posted 24 July 2021 - 07:48 PM

For this method to work, you need at least 60 seconds of tracking to make V tail. The first E slew normally stops the mount from tracking, keeping the gears engaged when the W slew starts. Your mount doesn't have a mode that doesn't track which will complicate the process. A further complication will be changing the mount's settings without causing vibrations that will distort the image. A final issue will be using a 2x sidereal speed which will make that leg of the V tail much fainter than the other leg.

 

You don't actually need the full V tail for this method to work. A better approach might be:

1. Set the rate to sidereal to track for your hemisphere.

2. Start an 90 second exposure and let the mount track for 5 seconds.

3. Switch to the other hemisphere and let the mount track for 60 seconds.

4. Use the slew button to return to the star - just a fraction over 10 seconds

5. Let the mount track for another 15 seconds.

 

You should see the bright star with the first tail attached to it. The second tail will be a short segment above or below the star. The critical part of this will be the length of the high speed slew. I'm not sure aboout the length of the high speed slew, you may need to adjust it.

 Sounds interesting but I got lost at #4, does the slew button refer to the 12x button on the star adventurer?



#17 Phil Sherman

Phil Sherman

    Gemini

  • *****
  • Posts: 3,491
  • Joined: 07 Dec 2010
  • Loc: Cleveland, Ohio

Posted 26 July 2021 - 08:28 AM

 Sounds interesting but I got lost at #4, does the slew button refer to the 12x button on the star adventurer?

Yes. That's why the duration of the button press needs to be 1/12 of the main tracked portion plus a tiny bit to reset the mount to it's starting position so the final tracked portion creates the short segment of what normally would be the return leg of the V. The duration of this button press may need a bit of adjustment to account for gear clearances.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: Imaging, Polar Alignment, Mount, Equipment, Astrometry, Accessories, Astrophotography, Beginner



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics