Problems with Polar/Drift Alignment

[Matty P (Matt)]

Hi all,

I have had two clear nights so far with my EQ6 Pro and I have not been able to accurately Polar or Drift align. I have read many guides on how to Polar and Drift align. I thought I had a fair idea on how to Polar/Drift align but actually doing it and getting it right is another thing. I was really hoping to get some imaging done.

I firstly did a rough Polar alignment then attempted to drift align. I set the latitude to 35deg for Canberra and pointed the best I could to True South. I couldn't find Octans in the polar scope so I just skipped this step. I then put a star in the FOV and observe the drift. I got pretty bad drift within 5 seconds of watching a star probably meaning that I am way off the SCP. I followed the instuctions on drift alignment but no matter what I did, I just couldn't stop a star from drifting.

I really didn't expect Polar and Drift alignment to be this challenging but I guess my initial thought was waaaaaaaay off just like my Polar alignment.

I am at my wits end with Polar and Drift alignment!

Any help will be much appreciated.

[Screwdriverone (Chris)]

Hi Matty,

I just came in from snapping away at Joop and polar aligned quite easily using the guide I wrote here. Have you had a look at it? The main benefit is to identify the "triangle" shape of Sigma Octans and its friends near the SCP through the finder scope.

I lined up my tripod with one leg pointing at 168 deg South (not true south) and then looked through the finder, saw the 4 stars that make up the Octans triangle near the SCP then fine tuned by moving the tripod left and right.

Once this was done ( took me 2 minutes) I had extremely good alignment and didnt need to correct when locked on Jupiter with just the RA drive.

I checked the NOAA website here and input your LAT/LONG location and came up with a 12 deg 22 min variance from true south which means you need to point to 168 deg south like me instead of south as indicated on the compass (that's East of south by 12 degrees.)

I hope this helps, once you have the scope and the finder pointed at the SCP, you could probably fine tune your alignment with drifting but I never bother as I am not as critical with drift as I am not doing overly long exposures using my afocal setup.

I hope this helps, looking forward to some of your top photos again.

Cheers

Chris

[Ian Robinson]

Have you got the tripod properly levelled ?

Have you got the right angle of the dangle on the RA axis for your latitude ?

Here is a finder chart for the SCP (centre of the two circles).

[Zuts]

The trick i found was to

(1) Assuming you have the scope leveled; and pointed close to the meridian and the celestial equator, see this http://www.asignobservatory.com/driftalignment.aspx

(2) Make sure the RA alignment knobe have equal travel on both sides.
(3) watch for the drift, then not using the knobs, rotate the mount an inch or two and keep on until the drift changes direction. Then you have crossed the celestial pole and can fine tune with the knobs.

If the star drifts out of the railway lines in 5 seconds then you are about 5 or more ep FOV's from the pole so need gross quick adjustments to get in the ballpark. I mean just watch for the direction of drift and then rotate. When it is taking 30 seconds to drift accross the reticle lines then use the knobs.

It took me a while, a few months, but now I can plonk it down anywhere aimed roughly between crux and the pointers and have good drift alignment in 40 minutes. I have never tried to find sigma octans.

Paul

[Tandum (Robin)]

Do you have an illuminated eyepiece,

get one. It make it easy.

[Matty P (Matt)]

Thanks for the help,

I have been practising my drift alignment on this drift simulator http://www.petesastrophotography.com...alignment.html. Folowing the instructions I was able to adjust my Altitude and Azimuth until no drift was visible. I have a better understanding now on what I need to do. If I can do it on a simulator I should be able to do it with my EQ6.

I gathered this information and I want to know if it is correct for drift alignment in the Southern Hemisphere.

To correct the Azimuth, I need to watch a star near the celestial equator and meridian. If it moves UP, rotate the MOUNT so the star moves to the RIGHT in the eyepiece. If the star drifts DOWN, rotate the MOUNT so the star moves to the LEFT.

To correct for ALTITUDE, watch a about 15 to 20 degrees above the Eastern Horizon. If it drifts UP, move the mount so the star goes DOWN. If the star drifts DOWN, move it up.

Is this correct?

[Matty P (Matt)]

Originally Posted by Ian Robinson

Have you got the tripod properly levelled ?

Have you got the right angle of the dangle on the RA axis for your latitude ?

Here is a finder chart for the SCP (centre of the two circles).

I always properly level the tripod with a spirit level before use.

Sorry, I don't quite understand what you are saying? Dangle on the RA axis? (Sorry, I am still trying to learn all the new meanings that are associated with an EQ mount)

Thanks for the finder chart.

Originally Posted by Tandum

Do you have an illuminated eyepiece,

get one. It make it easy.

Yep, I just got one.

[Zuts]

Originally Posted by Matty P

I gathered this information and I want to know if it is correct for drift alignment in the Southern Hemisphere.

To correct the Azimuth, I need to watch a star near the celestial equator and meridian. If it moves UP, rotate the MOUNT so the star moves to the RIGHT in the eyepiece. If the star drifts DOWN, rotate the MOUNT so the star moves to the LEFT.

To correct for ALTITUDE, watch a about 15 to 20 degrees above the Eastern Horizon. If it drifts UP, move the mount so the star goes DOWN. If the star drifts DOWN, move it up.

Is this correct?

ALTITUDE is spot on.

RA I am not so sure as it depends on the number of reflections. For my refractor with a diagonal i have an odd number of reflections so do the exact reverse of what you say. If you have an even number of reflections then you are correct.

So my understanding is odd number (refractor with diagonal, SCT with diagonal do what I say, Newt without diagonal do what you say.

Basically though if you move it and the drift gets quicker then you are going the wrong way

It's not rocket science, though when you are starting out it sure seems like it

Paul

[Matty P (Matt)]

Originally Posted by Zuts

ALTITUDE is spot on.

RA I am not so sure as it depends on the number of reflections. For my refractor with a diagonal i have an odd number of reflections so do the exact reverse of what you say. If you have an even number of reflections then you are correct.

So my understanding is odd number (refractor with diagonal, SCT with diagonal do what I say, Newt without diagonal do what you say.

Basically though if you move it and the drift gets quicker then you are going the wrong way

It's not rocket science, though when you are starting out it sure seems like it

Paul

Thanks for your reply Paul.

If you know what you have to do, it makes everything that much easier when you are actually doing it. Like you said, it is not rocket science but when you have absolutely no idea what you are doing, it sure is.

So for my scope (SCT) I will have to reverse the instructions that I posted.

To correct the AZIMUTH, I need to watch a star near the celestial equator and meridian. If it moves UP, rotate the MOUNT so the star moves to the LEFT in the eyepiece. If the star drifts DOWN, rotate the MOUNT so the star moves to the RIGHT.

I think I got it now.

[Geoff45 (Geoff)]

The best method of drift alignment I've ever seen is here on Cloudy Nights.
OK, I know its a US site, but the author is from Oz, so I guess it's OK to quote it. You have to think a bit to see what he is getting at, but once you do, you'll never use anything else.

For southern hemisphere if you have an odd number of reflections in your optical train the method for azimuth is this:
Hold your right hand flat with palm towards your face and with your thumb in the direction of drift. Adjust the azimuth so that the star moves in the direction your fingers are pointing. Repeat until there is no drift.

For an even number of reflections use your left hand.

For altitude (for all scopes, both hemispheres), if the star is in the east, adjust to make the star move in the opposite direction to the drift. If the star is in the west, adjust to make the star move in the same direction as the drift.
Geoff

[[1ponders] (Paul)]

Matty, don't worry about which direction the star drifts in Azimuth. The aim is to stop the drift correct? So when you put a star on the cross hair, watch it drift, then crank your Azimuth adjuster at least half a dozen full turns. Then recenter a star and watch again, if the star drifts much more slowly then you've gone the right way, if it drifts the other way you've gone too far. Either way you now know which way you haver to turn your adjuster.

If on the other hand your star drift is faster then you know you've gone the wrong way.

Now on some occasions I've not seen any change in the rate of drift, which means I'm waaay out. In this case I will actually pick up the two back legs of the tripod and move the tripod one way or another about 150mm and start again and repeat the process.

It sounds really rough, and it is, but you would be surprised how quick you can get with it. Plus you don't have to worry about which way us north or south or up or down or to turn left or right. In fact you can use this technique to determine if you drift one way which way to you turn your Azimuth adjustment for you scope. (remember it will be different with and without a diagonal).


To finish off I use K3CCDTools to fine tune.

BTW When you move the legs make sure you recenter your Azimuth adjustment before moving the legs.

[Matty P (Matt)]

Hi all,

On Saturday night I had another attempt at Polar aligning. This time I didn't bother trying to find Octans in the polar scope and went straight to Drift aligning.

I found a star close to the intersection of the Celestial equator and Meridian. I adjusted my azimuth until I didn't see any drift in DEC but instead there was a lot of drift in RA. Is this supposed to happen?

Problems with the Alt adjustment knobs stuffed up the whole drift alignment procedure but I am now fairly confident that I was getting pretty close to the pole.

Maybe next time?

[[1ponders] (Paul)]

The RA will move based on your Periodic Error but it should not "drift in RA as such. If it's drifting, look at your tracking speed (check to make sure you aren't in Lunar or Solar tracking) and again check your balance, also check your clutches are firm enough. Does it drift in RA if you meridian flip and line up on the Meridian/CE ? If so is it drifting in the same direction (tracking rate) or in the other direction or not at all (balance).

[Matty P (Matt)]

I corrected the drift in the North and South direction but as I watched a star, there was a steady but slow East drift.

Am I supposed to see any drift when adjusting the Azimuth?

Does this mean I was way off the SCP?

[[1ponders] (Paul)]

Don't worry too much about East, West, North or South atm. When you get a star centered in your reticle at the meridian, rotate the reticle so its lines are parallel to your hand paddle movements. From there check to make sure you have your orientation correct, up and down arrows for Dec and left and right arrows for RA. (You probably already know this but it helps to eliminate possibilities)

No matter how far out you are in polar alignment you don't get drift in RA, only in DEC. If you are getting a slow steady drift in one axis only then I'd say that is your Dec axis. The above process will help you to check that. If it is in your RA axis then something is definately wrong.

[Matty P (Matt)]

Thanks for the advice Paul,

I have probably gotten the directions mixed up.

[[1ponders] (Paul)]

If you haven't been orientating your reticle to start with it make it very hard to judge which way it is drifting. I still don't trust myself to work it out without using the hand paddle.