Location - accuracy

[iapa]

Hi,

How accurate does your location need to be when setting up GOTOs?

As an example, by default, the Celestron StarSense offers location by City. Where I am, three cities are listed, one about 150miles away, the other tow are both 20 miles and 30 miles away.

Is that sort of error in location actually usable?

Yes, I know that I can set a custom location on the StarSense

Question is around how accurate to I need to be?

Google, OS, SkySafari, SkyPortal, Astro Locator all give different locations, as do many other sites that 'locate' me.

Thanks

[Lorne]

When I had my goto, degrees and minutes were accurate enough, ie XX.XX North YY.YY West, important too is to get the time as exact as possible, usually my objects were in the eyepiece. 

[iapa]

Bad news - you are not that far away from me

Some of the tools that locate me are putting me in Glasgow, some Edinburgh, and one had me in Kirkcaldy - not quite the outskirts of Livi

Hence the question - is a 20mile radius good enough?

 

[brantuk]

Earth rotates 15 degrees every hour - and with a circumference of 24900 miles - one degree is 69 miles. For observing/goto 20 miles isn't gonna make a big difference - for imaging though you may want to be a spot more accurate. Of course it all depends on fov, eyepiece used, magnification, and software accuracy for your particular rig. So... you do the math - as they say lol

You can get your precise long/lat here: http://itouchmap.com/latlong.html

[iapa]

@brantuk ding the math is an issues

I can do 

1,2,3,4,5 , many, lots!

 

 

[Flyingfuzz]

I use Synscaninit,  a free app created by one of the users on the forum, gives spot on location based on your devices GPS.

 

[ollypenrice]

All you need to do is to look in an atlas which will have the Longitude and Latitude scales printed on the side of the map. The mania for electronic solutions can go too far!

Olly

[iapa]

18 minutes ago, ollypenrice said:

All you need to do is to look in an atlas which will have the Longitude and Latitude scales printed on the side of the map. The mania for electronic solutions can go too far!

Olly

@Olly

Indeed - and which scale maps?

OS Standard, land ranger.

My original question is - how accurate do I need to be for polar and star alignment? 

Star sense automatically put me at either Edinburgh or Glasgow. Is 25-30 miles accurate enough? 

If I enter Lat, Long, do I need to take it to hh:mm:ss/deg:mm:ss.

Is accuracy to whole mins enough, or  or should I take it to fractional seconds - if I can get an accurate enough location from which ever source  

[Cornelius Varley]

As an example the Synscan handset only requires degrees and minutes, so you will always be about 30 seconds out on your location coordinates. Try this site to get your location coordinates.

[iapa]

@Cornelius Varley

Hi, and the Nexstar+ prompts for deg,min,sec, StarSense hc defaults to selecting a city.

Herein lies my original question. The cities offered ar 25-35 away in opposite directions.

Is an error in location of c 30 miles accurate enough?? Or do I need to be more precise?

I have a thousand ways to determine a location, with varying degrees of accuracy.

PS The site you suggested, uses data from Google maps. That site differs from the direct use of Google maps by c 0.4".

 

[Cornelius Varley]

The Nexstar handset has preset locations from which you choose the nearest location.  Celestron must have confidence in this procedure to use it by default.

[ronin]

Get it as accurate as you can within reason, remembering that they only go down to minutes anyway.

If your satnav announced that you had arrived when you were 20-30 miles away you would not be happy, so supply data to the handset as accurately as you would like a satnav to tell you where you are.

PS The site you suggested, uses data from Google maps. That site differs from the direct use of Google maps by c 0.4".

Immaterial as the handset as said only takes data to 1 minute which is 60". So whatever the site is it is some 150 times more accurate.

[Pig]

In answer to your question ..... No it doesn't matter at all

[LukeSkywatcher]

My Celestron scope allows me to enter Dublin City (about 30 miles away) or even Belfast (about 150 miles away). I usually just input whatever it is (52-53N and whatever it is W).

Then i just do a single star align or most often a solar system alignment (with a planet).

[monaghan]

Iapa, the good answer is;

1° longitude error is equivalent to 4 minutes error on hour angle (24h) of the polar scope...

Calculation is easy. 24h/360°

 

[astronymonkey]

Maybe its just me but since accurate location and time is so easy to obtain these days I dont see the point of not entering it as close as possible. 

[Psychobilly]

I guess the Starsense just needs to know "roughly" where it is to get the alignment stars it is going to use with it's FOV... It will then "determine" where it is based on what it "sees"...

"Any sufficiently advanced technology is indistinguishable from magic. " - Arthur C. Clarke

Peter...

 

[Peter Drew]

As we are on a rotating platform I've always felt that the time accuracy is more important than location.

[DeepSkyBagger]

On 30/04/2016 at 21:12, brantuk said:

Earth rotates 15 degrees every hour - and with a circumference of 24900 miles - one degree is 69 miles. For observing/goto 20 miles isn't gonna make a big difference - for imaging though you may want to be a spot more accurate. Of course it all depends on fov, eyepiece used, magnification, and software accuracy for your particular rig. So... you do the math - as they say lol

You can get your precise long/lat here: http://itouchmap.com/latlong.html

One degree is 69 miles *at the equator*. It's considerably less at 50-odd degrees north.  At my latitude of 53 North, one degree is just over 40 miles, so 20 miles is going to make quite a big difference. You do the mathS, as we say in my country!

[cray2mpx]

On 1 May 2016 at 12:50, iapa said:

@Cornelius Varley

Hi, and the Nexstar+ prompts for deg,min,sec, StarSense hc defaults to selecting a city.

Herein lies my original question. The cities offered ar 25-35 away in opposite directions.

Is an error in location of c 30 miles accurate enough?? Or do I need to be more precise?

I have a thousand ways to determine a location, with varying degrees of accuracy.

PS The site you suggested, uses data from Google maps. That site differs from the direct use of Google maps by c 0.4".

 

Starsense also lets you enter a user location by lat/lon. To do that press the Option button (the button with the Celestron logo) while in the location menu (see page 11 of the user manual).

[BGazing]

what i do is

a) turn on the gps (have one app in the phone), get the coordinates and round them up to be as accurate as possible in minutes

b ) get the time over the phone, type one minute more than on the phone and wait for the exact moment the minute mark goes up to enter the time in the phone

as accurate as possible.

next stop, reticle eyepiece...LOL

[valleyman]

As already stated, It does not matter that much if you are just observing to use the nearest town location.

When I go to my dark sky site. it is about 20 miles away and never bother to change the location in the handset.

Not had any problems.

Getting the Tripod level and the alignment accurate is more important

You will need to be more accurate if you do Astro.

Hope this helps

Pat 

[popeye85]

Plus one for synscaninnit. Great wee app and removes any doubts about what you need to enter. 

[spillage]

On 27/06/2016 at 20:51, popeye85 said:

Plus one for synscaninnit. Great wee app and removes any doubts about what you need to enter. 

+1 from me too.

[Stub Mandrel]

Surely this only makes a difference to detecting when things become too low to be visible and to avoid pointing the scope at the ground?

Once aligned, you could be anywhere on earth and the goto will work fine (except for really close objects like satellites or the moon)