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Old 09-11-2012, 03:17 PM
mbaddah (Mohammed)
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How to (ccd?) drift align a Astrotrac/Vixen polarie for us Southerners using dslr

Assuming you have a standard tripod, 3 way gear head and ball head, can someone please clearly explain to me how they would go about drift aligning their vixen polair/astrotrac here in the southern hemisphere using a DSLR? Does CCD drift reduce the amount of time taken to do it? I haven't been able to find a clear explanation of how to drift align for these devices and I'd greatly appreciate the assistance.

Thanks guys

P.S: I have the polar scope and it's hopeless
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  #2  
Old 09-11-2012, 04:45 PM
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pluto (Hugh)
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So I assume you must have the Polarie attached to the alt/az camera tripod and then the ball head is attached to the Polarie with the camera attached to the ball head.
I could be totally wrong here but wouldn't it be the same as drift aligning an eq mount?
I would use SharpCap, or something similar, as it has an on screen reticule plus a program called ExtraWebcam which lets you use your dslr as a webcam. Then follow the standard drift aligning procedure and adjust the azimuth and altitude of the camera tripod.
I could be missing something fundamental here though...?

*EDIT forgot to mention that you would have to at least roughly align the polar axis of the Polarie to the SCP first using the alt/az controls on the tripod.

*EDIT2 this is the method I use for drift aligning (scroll down a bit): http://www.ozscopes.com.au/how-to-po...ern-hemisphere
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Old 10-11-2012, 12:12 AM
mbaddah (Mohammed)
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Quote:
Originally Posted by pluto View Post
So I assume you must have the Polarie attached to the alt/az camera tripod and then the ball head is attached to the Polarie with the camera attached to the ball head.
I could be totally wrong here but wouldn't it be the same as drift aligning an eq mount?
I would use SharpCap, or something similar, as it has an on screen reticule plus a program called ExtraWebcam which lets you use your dslr as a webcam. Then follow the standard drift aligning procedure and adjust the azimuth and altitude of the camera tripod.
I could be missing something fundamental here though...?

*EDIT forgot to mention that you would have to at least roughly align the polar axis of the Polarie to the SCP first using the alt/az controls on the tripod.

*EDIT2 this is the method I use for drift aligning (scroll down a bit): http://www.ozscopes.com.au/how-to-po...ern-hemisphere
Hi Hugh,

Many thanks for that last link. I had a read and it makes sense except for one part, how do I orientate the camera on the ball head? i.e. The 3 way gear head sits first on the tripod, then the astrotrac, then the ballhead, then the camera on the ballhead (as per screenshot on http://www.astrotrac.com/).

Say I want to do the first part, i.e. point my camera to a bright star on the eastern horizon near the celestial equator. Would I leave the gear head alone (i.e. not touch the az/alt), turn the camera only using the ball head to the east and than make the necessary adjustments with the gearhead? Does the camera have to be in a certain orientation?

Greatly appreciate the assistance.
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  #4  
Old 10-11-2012, 07:56 AM
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gregbradley
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You'd be better off using the compass and inclinometer accessory that fits in the hotshoe.

Drift aligning a Polarie would be very very hard as it has no fine adjustment knobs and with the heavy weight of the cameras its going to be a fairly crude adjustment.

When you say the Polar scope is useless is that because you are using it in light polluted Sydney? In which case it would be as Octans is quite dim.

Greg.
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  #5  
Old 10-11-2012, 08:53 AM
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pluto (Hugh)
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Quote:
Originally Posted by mbaddah View Post
Say I want to do the first part, i.e. point my camera to a bright star on the eastern horizon near the celestial equator. Would I leave the gear head alone (i.e. not touch the az/alt), turn the camera only using the ball head to the east and than make the necessary adjustments with the gearhead? Does the camera have to be in a certain orientation?
Yes that would be correct, leave the pan and tilt handles alone (lock off the roll handle and don't touch it at all) and just orient the camera using the ball head.
It's the polar axis of the Polarie/Astrotrac that you need to align so the camera orientation on the ball head doesn't matter.

As Greg said, it's going to be pretty rough depending on the controls your tripod has and how small adjustments you can make to them.
I'd be interested how good you can get it, good luck!
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  #6  
Old 10-11-2012, 12:53 PM
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naskies (Dave)
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What type of tripod do you have? Unless it's very high end, you'll probably find that it flexes a bit - which means that your polar alignment will vary based on the orientation of your DSLR. This limits how accurately you can polar align.

If your DSLR has Live View functionality, you can use it to drift align. Start with the mount off, place a tiny piece of tape on the DSLR screen to mark a star, wait for the star to drift a little bit, turn the mount on, use another piece of tape to mark the star again - now you have the RA axis marked out between the two pieces of tape.

Using this approach, I've been been able to successfully drift align an Astrotrac quite accurately (e.g. see these images), but that was using the Astrotrac wedge and pier which doesn't flex (much).

If you have a polar scope, there's a much easier way to polar align:

1. Start with the mount off and "polar aligning" it by adjusting the geared head so that the polar scope so that it's at a bright star, such as Rigil Kent. Your polar alignment will obviously be way off, but don't worry about it for now.
2. By adjusting the ballhead, point your DSLR so that the same star is near the centre of frame.
3. Take a short exposure, and use a small piece of tape to mark the location of the star. (You now know where the polar axis of your mount is in relation to your DSLR camera.)
4. Take a long exposure (e.g. 1-2 mins), and you'll see some star trailing. Based on the curve of the star trails, you'll be able to visually pick out roughly where the south celestial pole is in relation to your DSLR image.
5. Adjust the geared head (i.e. change the polar alignment of the mount) so that the SCP is approximately where your piece of tape is.
6. Repeat steps 4 & 5 (possibly zooming into the picture) until your polar alignment is very close to the SCP.

It's actually a very ingenious way to do polar align... thanks to a post I read once on the Astrotrac Yahoo group
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  #7  
Old 11-11-2012, 07:25 AM
mbaddah (Mohammed)
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Guys thanks for all these tips! I'm feeling a lot more confident now about drift alignment

Quote:
Originally Posted by naskies View Post
What type of tripod do you have? Unless it's very high end, you'll probably find that it flexes a bit - which means that your polar alignment will vary based on the orientation of your DSLR. This limits how accurately you can polar align.

If your DSLR has Live View functionality, you can use it to drift align. Start with the mount off, place a tiny piece of tape on the DSLR screen to mark a star, wait for the star to drift a little bit, turn the mount on, use another piece of tape to mark the star again - now you have the RA axis marked out between the two pieces of tape.

Using this approach, I've been been able to successfully drift align an Astrotrac quite accurately (e.g. see these images), but that was using the Astrotrac wedge and pier which doesn't flex (much).

If you have a polar scope, there's a much easier way to polar align:

1. Start with the mount off and "polar aligning" it by adjusting the geared head so that the polar scope so that it's at a bright star, such as Rigil Kent. Your polar alignment will obviously be way off, but don't worry about it for now.
2. By adjusting the ballhead, point your DSLR so that the same star is near the centre of frame.
3. Take a short exposure, and use a small piece of tape to mark the location of the star. (You now know where the polar axis of your mount is in relation to your DSLR camera.)
4. Take a long exposure (e.g. 1-2 mins), and you'll see some star trailing. Based on the curve of the star trails, you'll be able to visually pick out roughly where the south celestial pole is in relation to your DSLR image.
5. Adjust the geared head (i.e. change the polar alignment of the mount) so that the SCP is approximately where your piece of tape is.
6. Repeat steps 4 & 5 (possibly zooming into the picture) until your polar alignment is very close to the SCP.

It's actually a very ingenious way to do polar align... thanks to a post I read once on the Astrotrac Yahoo group
Hi Dave. Your pictures are amazing and it's the kind of shots I'm looking to do I LOVE that Polar Scope idea! Definitely going to give that a try first followed by watching the live view mode on my 5D2.

I have a Benro A257 Tripod, Manfrotto 410 geared head and a Manfrotto 488rc2 ball head. I can attach some weight to the tripod to improve stability.
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  #8  
Old 11-11-2012, 10:18 AM
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rogerg (Roger)
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I'd suggest organising yourself a laser holder:

http://rogergroom.com/astronomy-reso...lescope-mount/

Your geared head should be accurate enough to do decent fine-tuning adjustment and get a good alignment. I used one recently (I don't have one, I have the AT Wedge) and I was surprised and impressed how heavy duty and fine those Manfrotto geared heads are.

There are many methods of drift alignment mentioned on the Yahoo! AstroTrac forum, are you a member? I would suggest searching there.

A friend of mine used a "sped up" variant of polar alignment with his AstroTrac. I haven't tried it, but the explanation I have from him is as follows:

Quote:
I'm ecstactic! I finally discover an easy, quick, repeatable way to drift align the Astrotrac without the need of any PC or software. I did a quick trial tonight and even though the clouds keeps rolling in, I found that I can now do it a whole lot easier and quicker. It's a combination of traditional drift alignment and the DSLR/CCD method but with the Astrotrac!

This involves first puting the Astrotrac in Test mode. In this mode, the Astrotrac will move forward at the same speed as rewind speed. I set my exposure for 2 minutes and 5 seconds, the first 5 seconds with the Astrotrac at Start position, I then start the Astrotrac at full speed forward for one minute and then rewind it back for the second minute. The results is the same as the CCD method.

You'll be able to see the drift easily on the camera screen at full
magnification and then adjust the wedge accordingly.
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  #9  
Old 11-11-2012, 05:51 PM
mbaddah (Mohammed)
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Hi Roger,

Firstly I love your site! Keep up the great info and pics

Many thanks for the tips. I am indeed a member of the yahoo groups. Most members there had recommended I do a drift alignment without going into too much detail (hence why I posted here).

I like the sound of your friend's speed up trick. If the skies are clear tonight i'll try a few of these methods and report back how they go.

Thanks a million

Quote:
Originally Posted by rogerg View Post
I'd suggest organising yourself a laser holder:

http://rogergroom.com/astronomy-reso...lescope-mount/

Your geared head should be accurate enough to do decent fine-tuning adjustment and get a good alignment. I used one recently (I don't have one, I have the AT Wedge) and I was surprised and impressed how heavy duty and fine those Manfrotto geared heads are.

There are many methods of drift alignment mentioned on the Yahoo! AstroTrac forum, are you a member? I would suggest searching there.

A friend of mine used a "sped up" variant of polar alignment with his AstroTrac. I haven't tried it, but the explanation I have from him is as follows:
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  #10  
Old 12-11-2012, 11:21 PM
mbaddah (Mohammed)
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I managed to take the astrotrac out last night and try out the polar scope align method (aim at star nearby, centre star in liveview, adjust accordingly to SCP).

I managed to get a 50sec shot of Orion Nebula at 200mm. Definitely an improvement! With some minor refinements I'm sure I could get it to 2minutes using this method.

I'll try the ccd drift align next with the astrotrac in test mode. Things look promising
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  #11  
Old 14-11-2012, 02:16 PM
Jameswillia
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I am new to polar alignment and used this ccd drift method the other night and it worked (perfectly) in just minutes....

http://www.astrophotoinsight.com/node/568
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  #12  
Old 14-11-2012, 03:44 PM
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naskies (Dave)
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Your alignment is starting to look good! You're in some intense light pollution though... no wonder you're not having any luck with the polar scope! Even in light pollution free sites, I found the polar scope very difficult to use.
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