{"action":"created","issue":{"url":"https://api.github.com/repos/healpy/healpy/issues/356","repository_url":"https://api.github.com/repos/healpy/healpy","labels_url":"https://api.github.com/repos/healpy/healpy/issues/356/labels{/name}","comments_url":"https://api.github.com/repos/healpy/healpy/issues/356/comments","events_url":"https://api.github.com/repos/healpy/healpy/issues/356/events","html_url":"https://github.com/healpy/healpy/issues/356","id":183393133,"number":356,"title":"Improve accuracy of Healpix map analysis","user":{"login":"mreineck","id":898507,"avatar_url":"https://avatars.githubusercontent.com/u/898507?v=3","gravatar_id":"","url":"https://api.github.com/users/mreineck","html_url":"https://github.com/mreineck","followers_url":"https://api.github.com/users/mreineck/followers","following_url":"https://api.github.com/users/mreineck/following{/other_user}","gists_url":"https://api.github.com/users/mreineck/gists{/gist_id}","starred_url":"https://api.github.com/users/mreineck/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/mreineck/subscriptions","organizations_url":"https://api.github.com/users/mreineck/orgs","repos_url":"https://api.github.com/users/mreineck/repos","events_url":"https://api.github.com/users/mreineck/events{/privacy}","received_events_url":"https://api.github.com/users/mreineck/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":5,"created_at":"2016-10-17T11:39:19Z","updated_at":"2016-11-07T16:25:38Z","closed_at":null,"body":"I have been working for a long time to improve the accuracy of the Healpix map2alm operation. In its current state there are two approaches:\n- without any weigts, and\n- with ring weights\n\nThese both produce only approximate results for all multipole moments.\nA few weeks ago I managed to compute new sets of weights that vary from pixel to pixel. If these are used, Healpix-discretized functions on the sphere which have a band limit of lmax=3/2*Nside can be recovered by map2alm with machine precision. If higher multipoles are present, the result is affected by aliasing, but it should still be better than with the previous methods.\n\nComputing the weight sets for all required resolutions is expensive, but they can be stored and read from disk when needed, similar to the approach used with the ring weights. Due to the various symmetries of the Healpix grid, the size of a weight set at a given Nside is about 1/16th of a full Healpix map.\n\nIs there interest in using these new weights from healpy? If yes, it's probably simplest to just write the methods for reading the weights from disk and applying them to a map in Python. I can provide the FITS files if desired.\n"},"comment":{"url":"https://api.github.com/repos/healpy/healpy/issues/comments/258883634","html_url":"https://github.com/healpy/healpy/issues/356#issuecomment-258883634","issue_url":"https://api.github.com/repos/healpy/healpy/issues/356","id":258883634,"user":{"login":"lpsinger","id":728407,"avatar_url":"https://avatars.githubusercontent.com/u/728407?v=3","gravatar_id":"","url":"https://api.github.com/users/lpsinger","html_url":"https://github.com/lpsinger","followers_url":"https://api.github.com/users/lpsinger/followers","following_url":"https://api.github.com/users/lpsinger/following{/other_user}","gists_url":"https://api.github.com/users/lpsinger/gists{/gist_id}","starred_url":"https://api.github.com/users/lpsinger/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/lpsinger/subscriptions","organizations_url":"https://api.github.com/users/lpsinger/orgs","repos_url":"https://api.github.com/users/lpsinger/repos","events_url":"https://api.github.com/users/lpsinger/events{/privacy}","received_events_url":"https://api.github.com/users/lpsinger/received_events","type":"User","site_admin":false},"created_at":"2016-11-07T16:25:38Z","updated_at":"2016-11-07T16:25:38Z","body":"How long are we talking for generating them from scratch?"}}
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