Question on the Basics of drift alignment article [Archive]

bartman

10-12-2009, 09:09 PM

Gotst my reticule yesterday and tonight want to practice using it.
I've read through the - great - article on the basics of drift aligning here on IIS twice. I understand almost all of it. I just have a couple of questions:

I have a neq6 and will be using either a sw 10" newt or the sw 80ed pro, Meade reticule and have sussed out mag dec ( true north), long - latt and height above MSL.

1) in step 3, if the star is more than 30 deg above the horizon (east or west) will it affect the alignment a lot?

2) in step 4 it says 'pick a star on the meridian near the equator' . Just to check- the meridian is the north south line, and equator is the celestial equator. At 9 pm tonight here in Perth, the celestial equator will be past the zenith towards north. this means I need to change the RA to get the scope facing the CE. Is this true?

I understand the logic behind the pictures and the explanations Geoff Smith has given.... it's just that last one that has me double checking.

3) mmmmmm I have to ask just to make sure - tracking needs to be ON when doing this?

I've got a couple of hours before the sun goes down and hope the whispy clouds disappear.

Cheers for any replies!!!!!

Bartman:thanx:

leinad

10-12-2009, 09:58 PM

Hey Bart,

I'll try explain best I can.

1.Setup as normal, balance correctly the RA and DEC Axis.
As you may already know, but in case you didn't. Think of the RA axis as your propeller, DEC axis as your heli-rotor.

2. Just as you balanced horizontally on RA axis. Place the RA axis horizontal.
I usually have weights pointing East.

3. Slew and point the scope now about 60deg North.

Correct your meridian runs N/S, Zenith is right above you.

4. With slewing Sidereal On. Adjust your reticle or webcam, so that when you use the PAD L/R keys, the star in FOV moves L/R.
When you press UP/DWN on the PAD, the star will move either UP/DOWN, or if EP orientation is aligned the other way round, you will get the reverse.
Don;t worry about that. Your goal is to make the star move parallel to the crosshairs.

5. Now you watch for DEC drift, star moving UP or DOWN. Adjust the Azimuth bolts at te frnt mount head, turn knobs either side. I won;t tell you which correction to make, only that adjust the mount more to the East or more to the West. Place a star now on the line or near crosshair center, and see if it moves now slower DOWN, or UP or starts moving quicker in same direction or goes the other direction. You adjust the mount Left r Right accoridngly.
If it moved the other direction, then you corrected to far E or W of the SCP, and you need to adjust the other way again, or maybe just a little.

6. It will still drift a bit now, but not as much. All you do now is, SLEW the RA so that the weights do down, and in turn the scope is moving towards the East. You dont need to SLEW the scope. When you SLEW RA, the scope stays fixed and ends up pointing near the E Celestial Eq.

7. Now you do the same in watching for drift. But to adjust accordingly, you adjust the Altitude bolts. Front and rear levered bolts of the head mount. This tilts the RA axis N/S of the SCP.

You can go back to N again if you want and check the drift again, and you'll notice it may be much better.

After this I can walk away, make a coffee come back in 5mins, and see it has hardly moved at all.

Few rules.
-Don't unlock the clutches and move the mount manually with tracking on.
-Use SLEW speeds, and SLEW the mount.
-Don't worry about having to use the same star when you make your adjustments and the star moves out of FOV. Just use whatever is closest, or s star that is in the FOV.
-Make a good adjustment, over adjust or minor adjust, dont under adjust cause you'll hardly see a change unless you know what is expected, get more practice in large turns and seeing whether you went too far..
-It makes it easier to loosen the center mount rod that holds the mount head to tripod when making adjustments to the turn knobs(azimuth).
-Don't be afraid of how tight the frnt/rear levered bolts are. They are pretty tough and are holding the weight. You'll hurt your hands more.

8. Clear skies! :)