Gemini users - A/E errors

[Lee]

Do people use the A:E numbers given by the system (polar alignment errors) as a guide for when they are happy with their alignment? What numbers satisfy you?
Or do people tend to just make sure stars don't drift for how long?

[h0ughy]

yep make sure they dont drift for as long as possible - then the autoguider takes over

[JohnG]

The closer the A and E numbers are to zero the better, even with them at zero, you are still within a 1 arcminute box of the pole, this is where the A and E, + or - signs come into play.



Southern Hemisphere



A+ Move the mount front to the East

A- Move the mount front to the West



E+ Indicates you have to LOWER the mount


E- Indicates you have to RAISE the mount



Information from the Gemini Users Group.

Cheers

[rogerg]

John,

that's a nice summary of the numbers, but what do you mean by "mount front" ? (when looking south or when looking north?)

Thanks,
Roger.

[JohnG]

Hi Roger

The way I understand it is that the front of the mount is the counterweight bar/large elevation knob side, ie:

Looking down from the top, you turn the mount, counter clockwise to get an easterly movement, or:

Looking down from the top, you turn the mount, clockwise to get a westerly movement.

cheers

[Lee]

Gets confusing, the whole which way is up/down/left/right/east/west! I have found the only way to get really good alignment is to drift, and hope for numbers down around 0 or 1 to confirm (makes me feel better)....

I know which way is which when looking through the refractor with diagonal, and have it written down with a picture of which way to "push" the star depending on which way it drifts, depending on which side of meridian the scope (for low horizon drifting)....

I was going to put some stickers on the knobs, but haven't got around to it yet.

I still think the damn PAC doesn't work! Tried again last night.... didn't help.....

[rogerg]

Good idea ... I must do the same. I have written down things like clockwise/anti-clockwise, but glow-in-the-dark marker pen on the mount would be good, or sticker.



yeah, I had a thread going many months ago about that, and my attempts at using it. I gave up in the end, but only tried it 5 odd times I guess. I'm not sure what was going on - maybe it needs some tweaking for the southern hemisphere or something.

I also find the A and E numbers go up and down all over the place when I do 6 star alignments, but the pointing accuracy is always dead on, so I don't understand why it thinks some alignment points are so far out yet the pointing is so good.

So I tend to ignore the A and E numbers as I'm never sure if they really know what's going on.

Roger.

[Lee]

I did send an email to the developer (Goerlich?) - who swears blind PAC has been fully tested in the Sthn Hemisphere and is good to go..... I was to send him a big list of AE's from an alignment, but never got around to it.... gave up and drift aligned instead!

[JohnG]

I tend to agree with you guy's, I always do a Drift Align then build a model from there. The A and E numbers will be quite high for a while but usually settle down after 4 or 5 Addittional Aligns on the one side then finally settle when you do further Addittional Aligns on the opposite side.

At the moment, mine is around 6 arc minutes out in azimuth and 3 arc minutes low in elevation, hasn't effected the GOTO at all and the autoguider has no problems guiding so I have just left it.

Cheers