Longitude offset on polar finder

[Ccolvin968]

I'm just curious as to what this is for. It's an app that I'm using to polar align my skywatcher tracking mount. The iOptron app is showing something different from my scope companion app. The other app for android doesn't like my phone. The scope companion has a longitude offset of -3* east. The iOptron app doesn't state that, but the clock position is off by 17 mins between the apps. I'm trying to find a way to disable the offset but can't find anything. which is more accurate and how accurate does it need to be for photography just with a camera lens and no scope?

[ollypenrice]

In Minnesota you must be around Longitude -94E so you'd be a long way off with a longitude offset of -3E.

Olly

[kens]

It sounds like it might be the offset between your longitude and the longitude where the sun crosses the meridian at midday in your time zone. Or another way to look at it is how much earlier or later the sun crosses the meridian at your location. 17 temporal minutes corresponds to about 4 degrees of longitude if the back of my envelope is accurate.

The offset lets you set a polar scope to the right orientation using a time scale which needs to account for that difference. 

[Ccolvin968]

I'm at -92 degrees. The scope companion app let's me put in my Coords manually. If I set it as my location as -89, it almost identically matches my ioptron app. I'd keep using that one, but it isn't 3g or 4g enabled. So if I'm any further than my back yard, I won't have a clue.

[Ccolvin968]

I can always just do a quick trial with the two apps and see which is more accurate. Or I could just correct the cords manually to compensate as long as it's consistent.