2026AJ....171...17A

The Mittelman-di Cicco-Walker (MDW) Hα Sky Survey is an autonomously operated all-sky narrowband (3 nm) Hα imaging survey. The survey was founded by amateur astronomers, and the northern sky (decl. ≥ 0°) is presented here in its second stage of refinement for academic use. Each 3.6 deg² MDW field has 12 20 minutes individual exposures with a pixel scale of 3$\mathop{.}\limits^{\unicode{x02033}}$2, a typical point-spread function of 6″, and a stack point-source depth of 16-17 mag. The northern MDW Survey Data Release 1 (DR1) includes calibrated mean and individual images, star-removed mean fields, and point-source catalogs for all images matched to Data Release 1 of the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1) and the INT Galactic Plane Survey. (All DR1 components are available at https://mdw.astro.columbia.edu. The catalogs are also made available in the AAS Journals Zenodo repository: doi:10.5281/zenodo.17307324.) Our initial study of Hα filament widths finds a typical FWHM of 30″-45″ in the Lyra region. The matched catalogs (with a median match distance of ∼0$\mathop{.}\limits^{\unicode{x02033}}$5), combined with our distinctive narrowband photometry, are also used to identify Hα variable and excess sources. These initial studies highlight some of the many scientific uses of the MDW Hα survey.