Thinking out loud

[insomnia]

I need some clarification as to if this is possible....

Can a handheld digital compass or Magellan type handheld GPS be used as a digital setting circle for a Dob?

If North is found and then the device is secured to the center of the dob base then is it possible for a handheld GPS to be accurate enough to tell me if the scope is say 10 degrees from north

Just curious.

[JohnC]

In theory yes it should work, however there tends to be a time lag that can be frustrating.

Protractor would be more accurate i think.

How about protractor with a small led for illumination?

[badgerchap]

I've just hooked up my dob with alt/az circles - just made them myself using a compass and protractor and some paper. Took me about an hour but, provided I set it to north alright, seems to work fine. Next I need to find a way to tilt it up 38 degrees and hey presto, will have a rough equatorial design lol.

[Llamanaut]

a wixey will tell you what alt az youre at

[insomnia]

The time lag would not be an issue as I could aim ahead of the the target and just wait for it to appear in the ep.

[JohnC]

Good point!

[insomnia]

I am in the process of making a cardboard setting circle, I am just wondering if a handheld GPS would be just as accurate.

will a gps version of the pic below be possible?

[Macavity]

Aside from the "protractor plus Wixey idea" there is of course the: Celestron SkyScout and ilk, which at least seems to require a non-magnetic environment. "Maplins"(?) etc. seem to sell various magnetic (compass) transducers for experiment? Yer everyday iPod may even contain something like that these days?

I'd like to have a better idea of the functioning and parameters returned by GPS. Now that my Ioptron has one inside! I note it seems to take quite a WHILE to return information from "the mothership" tho'...

[insomnia]

An ipod touch does not have a GPS function like what the iphone 3G has, so if I point my Ipod towards Jupiter it will not automatically show Jupiter on the screen.

I assume that handheld GPS systems work by satellites and as such are not ideal for pin point measurements. I want a device that if I point it north and then save that direction in the device, can I then rotate the device on its axis and it then shows that it is pointing 10 deg or whatever from the saved north?

UPDATE.

just found this, wonder how good it is. The blurb says that it is accurate to + and - 1 deg

[TheThing]

Hand held GPS are not particularly accurate. They will tell you roughly how accurate they are, depending on how many satellites they lock onto. At best, they are only accurate to between 3 and 5m (but often higher than that!) And remember, that is 3 - 5m radius, so it might actually show you as 6m away from where you really are!

Not too bad if you out in the woods, lloking for a hidden Geocache with a clue, or wandering the hills on a footpath. How accurate that equates to degrees, mins and secs, I'm not too sure. Try it and see?

[insomnia]

I think that will be the problem with gps, it will tell you roughly where you are, but will not tell you what direction you are standing in, so it rules out gps.

I will try the LCD compass as they seem to show what degrees it is pointed, plus they are a lot cheaper than a gps

[brantuk]

Our Skyscout is good for general direction but too erratic to be of any accuracy for pointing the scope base/tripod.

I get better results with two tents pegs, a long bit of string and a regular compass. Orientate the string N-S using the compass (the longer the string the more accurate), then line the base or tripod over it. A wixey then finds the alt and I can get polaris in the finder just about every time - simples.... eeek!!

[vlebo]

This is a good solution

http://stargazerslounge.com/diy-astronomer/80995-diy-dob-setting-circles.html

Vlebo