Yet Another Question, Long and Lat

[leon]

Hi Guys, yes it seems that I am asking plenty of questions this week, but I'm sure you don't mind.

This regards my Long and Lat of my position in my back yard.

At present it is the location of Ballarat, which is 37:34 South and 143:52 East,but last night I was playing around with Google Earth and put the Curser on the exact spot of my Observatory.

The reading there was 37:35 South and 143:50 East, I know that there is not much in it, but would it be a good idea to reset the coordinates in the g11 to fix this, or wouldn't it make that much difference.

Thank You.

Leon

[iceman (Mike)]

How far are your goto's off?

The more accurate the better, in general.

[gbeal]

Not sure it will make too much difference Leon, but what the heck, change them and see. Like Mike says can't hurt to be spot on.
Gary

[leon]

Thanks Guys Go-To's are pretty much spot on, every time, but then, as you say what the heck see what happens.

leon

[Dennis]

Hi Leon

I understand that for general observations, a Lat and/or Long uncertainty of a degree or two isn’t critical for GoTo’s, and a time error of 10 to 15 mins doesn’t seem to have too much affect either in terms of placing the object in the FOV.

Where you do need more precise Lat, Long, Time and altitude above sea level settings, are for tracking man-made satellites, as their proximity to Earth magnifies any location/time errors. I think that satellite observers usually sync their notebooks with atomic time to ensure accurate location/tracking of these Earth orbiting objects.

Cheers

Dennis

[Kokatha man]

Originally Posted by leon

Hi Guys, yes it seems that I am asking plenty of questions this week, but I'm sure you don't mind.

This regards my Long and Lat of my position in my back yard.

At present it is the location of Ballarat, which is 37:34 South and 143:52 East,but last night I was playing around with Google Earth and put the Curser on the exact spot of my Observatory.

The reading there was 37:35 South and 143:50 East, I know that there is not much in it, but would it be a good idea to reset the coordinates in the g11 to fix this, or wouldn't it make that much difference.

Thank You.

Leon

Hi Leon - haven't a clue what the g11's accuracy is (fully compensated, that is) but a bit of quick maths indicates your original coordinates were 99.98% accurate with regard to longitude and 99.95% accurate with regard to latitude - both percentages calculated in regard to minutes of arc using the Google coords as accurate.....

This equates to an error of 0.012 seconds of arc in longitude and 0.03 seconds of arc in latitude: even if your set-up is on a rock solid pier I can't imagine these sort of figures having any influence - especially when you consider the differential expansion rates of the various elements (temperature wise, that is) in the pier/mount assembly etc....!

Regards, Darryl.

[Karlsson]

Originally Posted by Kokatha man

Hi Leon - haven't a clue what the g11's accuracy is (fully compensated, that is) but a bit of quick maths indicates your original coordinates were 99.98% accurate with regard to longitude and 99.95% accurate with regard to latitude - both percentages calculated in regard to minutes of arc using the Google coords as accurate.....

This equates to an error of 0.012 seconds of arc in longitude and 0.03 seconds of arc in latitude: even if your set-up is on a rock solid pier I can't imagine these sort of figures having any influence - especially when you consider the differential expansion rates of the various elements (temperature wise, that is) in the pier/mount assembly etc....!

Regards, Darryl.

This is correct provided both sets of coordinates refer to the same map datum (reference grid, not unlike J2000 and B1950 for RA/Dec) - do not take that for granted though...

[Kokatha man]

Originally Posted by Karlsson

This is correct provided both sets of coordinates refer to the same map datum (reference grid, not unlike J2000 and B1950 for RA/Dec) - do not take that for granted though...

You are most certainly spot-on there brother: working off raw data, your comments are even more pertinent: I guess (?!?) my response, especially factors re mount inaccuracies that rarely get canvassed, make some of the musings rather less relevant than some make issue of.

I note that you're an engineer Karlsson - though I don't know of what persuasion: consulting on my own projects with your profession has led me to understand that factors such as soil movement and structural expansion/contraction can have significant effects; for IIS purposes re the stability of any optical alignments, particularly when many consider that piers etc are "set-and-forget" procedures.

I'd be interested to hear your own views on these matters.....

Regards, Darryl.

[peter_4059 (Peter)]

Great thread - really puts it all in perspective.

[leon]

Well by looking at the responses I don't have to much to fear then, thank you for your imput.

leon

[netwolf]

Don't goto's Triangulate your Lat/Long from the Alignment stars? Why is an external GPS or manual coordinate entry important? I guess it might make the intial slew to the Alignment star more accurate. Has someone actually measurred the benefit of GPS?

[Ian Robinson]

Originally Posted by netwolf

Don't goto's Triangulate your Lat/Long from the Alignment stars? Why is an external GPS or manual coordinate entry important? I guess it might make the intial slew to the Alignment star more accurate. Has someone actually measurred the benefit of GPS?

.... I suspect the addon GPS Meade and Celestron are flogging is a gimmic.

Now if the gadget gives a digital display of where you are : I might buy one if I can use in when I do 4x4 / fishing safaris.