How critical is the location setting?

Using SharpCap's Polar Alignment feature
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GregMcKay
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Joined: Wed Sep 06, 2017 6:43 pm

How critical is the location setting?

Post by GregMcKay » Mon Sep 14, 2020 4:34 am

In the polar alignment settings one of the options is "estimate from time zone"
My friend swears location must be dead-on accurate for P. A. to work properly.
If that's so, why have time zone as an option?

Thanks

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Re: How critical is the location setting?

Post by admin » Mon Sep 14, 2020 8:07 pm

Hi,

there are two things that the location data gets used for in the polar alignment.

1) calculating the amount of refraction correction that is necessary – this only depends on your latitude and having your latitude correct within 1° is certainly accurate enough. To be honest, unless you're in the tropics then having your latitude correct within 5° probably good enough :-)

2) calculating the movement directions the suggested (up/down/left/right) during the final alignment stage. This depends on your longitude which can be estimated from your time zone. If you're longer chooses 15° out then SharpCap might say 'move down' when really you should be moving in a sort of 5:30 o'clock face direction. The difference isn't really very much and actual accuracy isn't affected at all because you could completely ignore the up/down/left/right suggestions and just put the indicated star into the box by trial and error and get perfectly good alignment.

So, in summary, your location doesn't need to be particularly accurate for the polar alignment to work. In fact it it can work in a basic way if it only knows your hemisphere!

Now, in SharpCap 3.3 there is a new sequencing tool which has all sorts of ways of setting up SharpCap to capture automatically. One of things you can ask it to do is to wait for a particular time of day before starting to capture – for instance wait until astronomical darkness starts. If you want that to work correctly then you do need to enter your location properly!

Cheers, Robin

GregMcKay
Posts: 9
Joined: Wed Sep 06, 2017 6:43 pm

Re: How critical is the location setting?

Post by GregMcKay » Mon Sep 14, 2020 9:01 pm

Robin,

Thank you for clearing up that mystery with such a detailed explanation.

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