When to perform drift alignment

[Black Knight]

I'm trying to capture DSO images on my DSLR, but my last attempts were um, somewhat less than stellar to say the least, showing a certain amount of drift. So next time I'm out, along with tightening up the levelling and polar alignment, I'd thought I'd also have a go at drift alignment.

My questions are:

1. At what stage do I perform the drift alignment procedure? After polar alignment of course, but before or after the 3 star Synscan alignment?

2. Can I manually move about the Dec and RA axes when the motor drive is on, or would this bork Synscan's perception of where it is pointing to in the sky?

I'd be very grateful for any help you guys can give me. Thanks.

[barkis]

You don't even need the drive switched on.

If you locate a star around 20 - 30 degrees of the celestial equator, and get the scope pointed to it so that it is seen in a reticule eyepiece. Orientate the crosshairs so that the horizontal line bisects the star as you move east and west manually, using the RA axis. Make sure the Dec. axis is locked, as you do not want that to move. Once that's done, wait a few minutes, then carefully move the scope to catch the star up, because it will have moved. If the star as moved above or below the crosshair, then the alignment is off. If it has drifted North, remembering that some scopes invert the Image, so North will at the bottom, The polar Axis is too far West of the Celestial Pole. If the star has drifted South, then the axis is too far east of the Celestial equator.

In order to check if the mount is pointing too high or too low above the celestial equator, you need to choose a star on the East or West Horizon. If it is a star in the East, and the drift is Northward, then the mount is pointing too much above the pole. A south drift means it is to much below the pole.

Use small incremental adjustments, you will be able to judge how much effect your movements are having.

Ron.

[Black Knight]

Thanks Barkis, sounds like a plan . Would I need an illuminated reticule EP for this?

[barkis]

Thanks Barkis, sounds like a plan . Would I need an illuminated reticule EP for this?

I would say yes, it makes it easier if you can see the crosshairs, and having parallel ones is ideal too, although I made do with only a cross years ago.

Ron.

[Black Knight]

Thanks Ron, you've been a great help

[barkis]

No probs, but just to clarify that when I said earlier in the thread that you should wait a few minutes then gently move the scope in RA to catch up with the target star, it was not intended to suggest that that time was sufficient, but merely to give an indication as to whether or not the star was drifting and attention to the mount would be required. The longer you can get the star to remain in between those parallel lines, the better the alignment will be.

That applies to both the E W calibration (Meridian Star) and the N S calibration (East or West Star.)

If you can get a duration of 10 minutes, your mount will have very little work to do in the way of guiding corrections.

Ron.

[Black Knight]

10 minutes then, excellent, thanks Ron