Micrographia — Observ. LIX.

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LIX.

_Of multitudes of small _Stars_ discoverable by the _Telescope_.

_ Having, in the last Observation, premis’d some particulars observable in the _medium_, through which we must look upon _Cœlestial_ Objects, I shall here add one Observation of the Bodies themselves; and for a _specimen_ I have made choice of the _Pleiades_, or seven Stars, commonly so called (though in our time and Climate there appear no more then six to the naked eye) and this I did the rather, because the deservedly famous _Galileo_, having publisht a Picture of this _Asterisme_, was able, it seems, with his Glass to discover no more then thirty six, whereas with a pretty good twelve foot _Telescope_, by which I drew this 38 _Iconism_, I could very plainly discover seventy eight, placed in the order they are ranged in the Figure, and of as many differing Magnitudes as the _Asterisks_, wherewith they are Marked, do specifie; there being no less then fourteen several Magnitudes of those Stars, which are compris’d within the draught, the biggest whereof is not accounted greater then one of the third Magnitude;

and indeed that account is much too big, if it be compared with other Stars of the third Magnitude, especially by the help of a _Telescope_; for then by it may be perceiv’d, that its splendor, to the naked eye, may be somewhat augmented by the three little Stars immediately above it, which are near adjoyning to it.

The _Telescope_ also discovers a great variety, even in the bigness of those, commonly reckon’d, of the first, second, third, fourth, fifth, and sixth Magnitude; so that should they be distinguish’d thereby, those six Magnitudes would, at least, afford no less then thrice that number of Magnitudes, plainly enough distinguishable by their Magnitude, and brightness; so that a good twelve foot Glass would afford us no less then twenty five several Magnitudes.

Nor are these all, but a longer Glass does yet further, both more nicely distinguish the Magnitudes of those already noted, and also discover several other of smaller Magnitudes, not discernable by the twelve foot Glass: Thus have I been able, with a good thirty six foot Glass, to discover many more Stars in the _Pleiades_ then are here delineated, and those of three or four distinct Magnitudes less then any of those spots of the fourteenth Magnitude.

And by the twinkling of divers other places of this _Asterisme_, when the Sky was very clear, I am apt to think, that with longer Glasses, or such as would bear a bigger _aperture_, there might be discovered multitudes of other small Stars, yet inconspicuous.

And indeed, for the discovery of small Stars, the bigger the _aperture_ be, the better adapted is the Glass; for though perhaps it does make the several specks more radiant, and glaring, yet by that means, uniting more Rays very near to one point, it does make many of those radiant points conspicuous, which, by putting on a less _aperture_, may be found to vanish; and therefore, both for the discovery of the fixt Star, and for finding the _Satellites_ of _Jupiter_, before it be out of the day, or twilight, I alwayes leave the Object-glass as clear without any _aperture_ as I can, and have thereby been able to discover the _Satellites_ a long while before; I was able to discern them, when the smaller _apertures_ were put on; and at other times, to see multitudes of other smaller Stars, which a smaller _aperture_ makes to disappear.

In that notable _Asterism_ also of the Sword of _Orion_, where the ingenious Monsieur _Hugens van Zulichem_ has discovered only three little Stars in a cluster, I have with a thirty six foot Glass, without any _aperture_ (the breadth of the Glass being about some three inches and a half) discover’d five, and the twinkling of divers others up and down in divers parts of that small milky Cloud.

So that ’tis not unlikely, but that the meliorating of _Telescopes_ will afford as great a variety of new Discoveries in the Heavens, as better _Microscopes_ would among small terrestrial Bodies, and both would give us infinite cause, more and more to admire the omnipotence of the Creator.

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