# Distance to stars from my house using the parallax technique?

1. May 30, 2009

### Stratosphere

Is it possible to find the distance to stars from my house using the parallax technique? If I can how close does a star have to be to be measured in a month instead of six months?

2. May 30, 2009

### Nabeshin

Re: Parallax

If I didn't know any better I'd say you were trying to do this yourself.

A star at a distance of 1 pc displays a parallax of 1 arcsecond. There are no stars closer than 1pc, so even the nearest are going to display a parallax siginificantly smaller than 1 arcsecond. And these are annual parallax numbers. If you want to try the measurements in only a month, you can expect much smaller parallaxes, on the order of 1/50 of an arcsecond for typical stars.

So, unless you have that kind of resolving power, I'd say it's out of the question.

3. May 30, 2009

### Stratosphere

Re: Parallax

So would I be able to measure things that would require a longer amount of time?

4. May 30, 2009

### Nabeshin

Re: Parallax

Probably not. Like I said annual parallaxes are going to be less than one arc second. Significantly less, but it's probably even optimistic to hope to get some in the neighborhood of 1/10 of an arcsecond. Annually. Also, given the fact that even under the best of seeing conditions the earth's atmosphere limits resolution to about .5 arcseconds, it seems a daunting task indeed.

Getting down to .5 arcseconds isn't actually that hard, and only requires a ~8-10 inch diameter telescope. But taking precise enough measurements to detect the parallax, owing to the damned atmosphere, would be near impossible for an amateur (I think).

5. May 30, 2009

### Chronos

Re: Parallax

You can do the math with simple trigonometry. The diameter of the earths orbit around the sun is approximately 186 million miles [a very convenient number - 1000 light seconds]. That forms the base of the parallax triangle you have to work with. One light year works out to around 6 trillion miles - a pretty large number compared to the diameter of earths orbit. You need a very accurate [and expensive] devise to reliably measure such small angles.

6. May 30, 2009

### DaveC426913

Re: Parallax

OK, these answers are better than mine. Which was going to be 'Depends on how wide your house is'.