Talk:Cosmic distance ladder

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[edit] Proposed merger with Extragalactic Distance Scale (May 2008)

There's strong overlap between the two subjects, but a lot of hammering out is needed to get that done. This ("CDL") page is stronger for the near-distance things. The other article ("EDS") is more like a laundry list at this point, and is more aimed at the extragalactic distances in particular. Ideally I think the two could be merged to a rather large article ... but to do it properly would make an article so large as to be a candidate for splitting. I think both articles can be fleshed out a bit more prior to a reconsideration of the merger. At this time I vote against the proposed merger with a "not at this time, but later" qualifier: both articles should be edited so as to make such a merger seamless in the future. BSVulturis (talk) 15:49, 15 May 2008 (UTC)

I agree, lots of overlap and would throw in standard candle to the mix too. WilliamKF (talk) 22:08, 23 May 2008 (UTC)

[edit] "clarification"

I added a section called "clarification" because I think the article was a bit obscure for people with no idea of the concept at all. It still needs work and I wrote it largely from the top of my head, plus I'm no astronomer so it needs to be reviewed by a pro!

212.153.56.254 13:20, 6 January 2006 (UTC)

[edit] Baseline for parallax measurements

I think the baseline is normally 2 AU rather than 1 AU. The baseline is the diameter of the Earth's orbit (not the radius), doubling the baseline and doubling the angle that must be measured and thus doubling precision. But I'm not confident enough to change the text.

I do believe there's a need for this article. Good effort. --Chris Jefferies (talk) 01:14, 5 January 2008 (UTC)

The baseline across the isoceles triangle is 2 AU. The formal development for parallax involves splitting that isoceles triangle into two right triangles, each with the short leg of the triangle between Sun and Earth (so that is 1 AU) and the long leg of the triangle being the distance between the Sun and the target star. So for measuring, yes, the baseline could be as large as 2 AU, but the parallax is defined with a right triangle whose short leg is 1 AU. BSVulturis (talk) 23:59, 12 February 2008 (UTC)