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SHO/HSO SH2-132- Lion Nebula

(James Clark - LSHO)
(James Clark - Starless close-up)
(James Clark - HSO widefield)

Information...

This is a another narrowband image which has been taken with Sulphur II (SII 671.7 & 673.0 nm), Hydrogen alpha (Hα 656.3nm) and doubly ionised Oxygen (OIII at 500.7 & 495.9nm) filters. For the main images the resulting 3 monochrome images have then been combined with the SII being mapped to the 'Red' channel, Hα to 'Green' and OII to 'Blue'. An additional neutral colour 'Luminance' filter has also been used.

For the widefield image, a HSO palette has been chosen, with a dual-narrow band filter used for the Hα ('Red') and OIII/Hβ ('Blue') channels. The 'Green' channel has then been synthesised from a mix of the resulting Red/Blue images.

The Lion Nebula, can be found in the constellation of Cepheus and without this kind of specialist processing is more of 'red / blue-grey blob'!

 

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Map

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Measuring Angles

Hold your arm at full length, then close one eye & use the hand shapes shown above to measure the angular distance between the stars.

(Ain't anatomy wonderful!)

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Apparent Magnitude

The apparent magnitude of a star is a measure of how bright it appears from Earth. The scale was introduced over 2,000 years ago by the Greek astronomer Hipparchus, who grouped stars into six categories. The brightest 20 or so were deemed to be 'first magnitude', slightly dimmer stars 'second magnitude', and so on until the barely visible stars were classed as 'sixth magnitude'.

Later it was recognised that our eyesight, once it has been given time to get used to darkness, has a logarithmic response. i.e. a Mag. 1 star is actually 2.512 times brighter than a Mag. 2 star, or 6.310 times brighter than a Mag. 3 star (2.512 x 2.512 = 6.310).

The six Magnitudes thus corresponds to a 2.5126 difference in brightness or 100x.

Apparent magnitude

Today the scale has now been extended, so that brighter objects can have an apparent magnitude of 0 or even negative. The brightest star Sirius, for example, has an apparent magnitude of -1.44 and the Sun is a whopping -26.74, due to it's close proximity to Earth.

 

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