EQ6 bubble level

[DaveO (David)]

This thread has been very interesting! At least I know I am not alone!

At last Astrofest I struggled with my brand new EQ6's GOTO functionality. It wasn't until some week's later that I discovered that the latitude scale was off by 6-8 degrees. That had been the one thing I figured I didn't have to worry about!

Now there are questions about the bubble level?

I don't know about you, but when I pay a considerable sum of money for a mount, I expect that at least the simplest parts of it should work as advertised. After all, how hard is it to get the latitude scale aligned correctly, or to place a bubble level accurately? It wouldn't cost that much more - the time difference is not that significant and the wages aren't that high!

I really like my mount and have generaly been very happy with its performance, but these little niggles just make it harder.

Well I'm off to get a level to check the level now.

[matt]

Originally Posted by Dennis

If the mount is not level, you will have to make compound changes to Alt-Az when drift aligning.

Hi Dennis

By this do you mean one would have to go from one to the other making (hopefully) ever-decreasing fine adjustments until the polar alignment is spot on?

Cheers

[Lee]

Originally Posted by DaveO

I don't know about you, but when I pay a considerable sum of money for a mount, I expect that at least the simplest parts of it should work as advertised.

You would think wouldn't you. Although I am becoming more of a cynic by the day when it comes to advertised vs delivered service.

[Dennis]

Originally Posted by matt

Hi Dennis
By this do you mean one would have to go from one to the other making (hopefully) ever-decreasing fine adjustments until the polar alignment is spot on?
Cheers

Hi Matt

I have never drift aligned, so what follows are my theoretical musings on the topic from trying to grapple with it in a mental model – the Tak has an excellent Polar Alignment ‘Scope.

If we start out with our mount level, then our polar axis may be misaligned in altitude, azimuth or both.

An Altitude misalignment is when the mount’s polar axis is off in altitude, pointing either N or S of the true pole. With the mount misaligned in altitude relative to SCP:
Polar Axis too high? Star drifts South.
Polar Axis too low? Star drifts North.
In this case, the star is a bright star in the East, about 15 degrees above the Horizon, near the Celestial Equator.

An Azimuth misalignment is when the mount’s polar axis is off in azimuth, pointing either E or W of the true pole. With the mount misaligned in Azimuth relative to SCP:
Polar Axis too far East? Star drifts North.
Polar Axis too far West? Star drifts South.
In this case, the star is a bright star near the intersection of the Meridian and the Celestial Equator.

With drift alignment, I believe you never compensate for drift in RA, you only watch out for movements in DEC.

If the mount is not level, when you make an adjustment in say Altitude, you will also be making an adjustment in the Azimuth axis as well, so I presume the overall task becomes more difficult, possibly requiring more iterations?

Hope that helps

Cheers

Dennis

[matt]

Cheers Dennis

Believe it or not, I have already mastered drift aligning. It's one of the few things I actually know how to do!

I take it I'm correct in what I said in my prior post?

[Dennis]

From reading stuff about drift alignment, you will end up making smaller and smaller adjustments as you get closer and closer to the SCP, so yes what you said appears correct. I think you also need to watch the relevant star for longer periods to detect the increasingly small misalignment due to making the adjustments?

If your mount is level, then your azimuth movements will be parallel to your local horizon and your altitude movements will be parallel to your local meridian. Making an adjustment in Azimuth to move the mount E or W will not cause any movement in Altitude N or S and making an adjustment in Altitude to move the mount N or S will not cause any movement in Azimuth E or W.

However, if your mount is not level, then when you make an adjustment in Azimuth, you will also be making a corresponding small adjustment in Altitude as well and it is this compound motion in both axes that you want to avoid.

Hmm, must try this one evening to check how accurate the Tak polar alignment ‘scope is.

Cheers

Dennis

[Doug]

Dennis, there remains the very real possibility that the axis about which the altitude adjustment rotates might not be exactly parallel to the base of the mount/tripod base. General machining errors, flexure under load, overall lack of rigidity could easily undo the most exacting tripod leveling. I know a GE mount is not the same nightmare as a Meade super wedge aligning a fork mounted scope, however a lower budget mount is not going to be as well engineered as the more high end mounts.
cheers,
Doug