Observation of the transit Transit of Venus, 1639

crabtree watching transit of venus a.d. 1639 ford madox brown – 1 of manchester murals. crabtree depicted old man although 29 years old when made observation.



an image of solar disk hevelius added report, based on horrocks s description of observation. image not, however, give true representation of horrocks have seen.

horrocks concerned weather unfavourable transit believed rare planetary conjunction produce severe weather:

the chance of clouded atmosphere caused me anxiety; jupiter , mercury in conjunction sun @ same time venus. remarkable assemblage of planets (as if desirous of beholding, in common ourselves, wonders of heavens, , of adding splendour of scene), seemed forebode great severity of weather. mercury, conjunction sun invariably attended storm , tempest, feared. in apprehension coincide opinion of astrologers, because confirmed experience; in other respects cannot despising more puerile vanities.

at around midday on 23 november horrocks darkened room , focused rays of sunlight coming through window onto paper image observed safely. @ location in hoole (the latitude of determined 53° 35 ), calculated transit should begin @ 3:00 pm on sunday 24th, began observations previous day fearing might miss event if calculations proved inaccurate. on sunday began observing @ sunrise, weather cloudy, first saw tiny black shadow of venus crossing sun @ 3:15 pm, , observed half hour until sunset @ 3:53 pm.

when time of observation approached, retired apartment, , having closed windows against light, directed telescope, adjusted focus, through aperture towards sun , received rays @ right angles upon paper ... watched on 24th sunrise 9 o clock, , little before ten until noon, , @ 1 in afternoon, being called away in intervals business of highest importance which, these ornamental pursuits, not propriety neglect ... fifteen minutes past 3 in afternoon, when again @ liberty continue labours, clouds, if divine interposition, entirely dispersed ... beheld agreeable spectacle, object of sanguine wishes, spot of unusual magnitude , of circular shape, had entered upon sun s disk on left ... not doubting shadow of planet, applied myself sedulously observe it ... although venus continued on disk several hours, not visible me longer half-an-hour, on account of [the sun] setting ... inclination point upon failed attain utmost precision; for, owing rapid motion of sun, difficult observe certainty single degree ... rest sufficiently accurate, , exact desire.

crabtree made observations using similar set-up had insufficient time make measurements, cloudy in broughton, , saw transit briefly. according horrocks: rapt in contemplation stood time, scarcely trusting own senses, through excess of joy ... in little while, clouds again obscured face of sun, observe nothing more venus on disc @ time. afterwards, made rapid sketch of venus had passed across sun s disc, allowing crabtree estimate angular size of venus 1 3 , accurate within 1 second of arc of actual size; horrocks s estimate of 1 12 less accurate.

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