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Moon apogee/perigee

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16 years 2 months ago #64292 by pj30something
Moon apogee/perigee was created by pj30something
I've just been reading John's (Skynotes) PDF file and i am wondering about the colour difference between both images of the moon during apogee and perigee.

The apogee image is brighter while the perigee image is darker. Would this be because during apogee the moon is further away from earth and gathers/reflects more sunlight while during perigee the moon is closer to earth thus gathering/reflecting LESS sunlight.........hence the darker colour?

I'll be honest....i always thought the moon had a circular orbit around the earth.

Paul C
My next scope is going to be a Vixen VMC200L Catadioptric OTA

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16 years 2 months ago #64297 by Seanie_Morris
Replied by Seanie_Morris on topic Re: Moon apogee/perigee
The apogee/perigee doesn't really have anything to do with it. It is down to the fact they are 2 different shots, taken at different times, under different conditions, and probably with different cameras.

:?

Midlands Astronomy Club.
Radio Presenter (Midlands 103), Space Enthusiast, Astronomy Outreach Co-ordinator.
Former IFAS Chairperson and Secretary.

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16 years 2 months ago #64300 by pj30something
Replied by pj30something on topic Re: Moon apogee/perigee
I was thinking that was maybe the case Seanie but then i started thinking that a moon closer to earth would be more "in the shadow" of earth thus not as much sunlight getting to it..................hence it would appear darker.

Paul C
My next scope is going to be a Vixen VMC200L Catadioptric OTA

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16 years 2 months ago #64303 by Seanie_Morris
Replied by Seanie_Morris on topic Re: Moon apogee/perigee
If the Moon is in our shadow, then it is eclipsed! ;)

Midlands Astronomy Club.
Radio Presenter (Midlands 103), Space Enthusiast, Astronomy Outreach Co-ordinator.
Former IFAS Chairperson and Secretary.

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16 years 2 months ago #64305 by pj30something
Replied by pj30something on topic Re: Moon apogee/perigee
I didnt mean "in our shadow".....................just closer so that the sun light bending around the earths curve and hitting it is less then when it is further away.

God it's hard to explain what i mean without it sounding like an eclipse.

Let's just go with the different cam,lighting etc.

So basically during apogee/perigee...............................there IS no difference in brightness?

Unless of course the moon is at a different phase during both.

Paul C
My next scope is going to be a Vixen VMC200L Catadioptric OTA

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16 years 2 months ago #64315 by johnflannery
Replied by johnflannery on topic Re: Moon apogee/perigee
That's an interesting question Paul.

The brightness difference between the closest and most distant Full Moon is hard to judge but one can apparently be measurably brighter than the other.

The reason is due to the time of year and this also is a clue as to why the two Moons in Anthony's image are tinted a different hue.

Observe moonrise over a couple of hours and you'll notice the colour of the disk change from a deep golden yellow through to chalk white as the Moon rises higher in the sky. When low down the moonlight passes through a thicker cross-section of our atmosphere, filtering out the bluer wavelengths of light. Higher up and the light is passing through less murky air. The same effect is happening as with the setting sun ranging through yellow, orange, and blood-red.

The apogee shot was in Winter when the Full Moon is higher in the sky whereas the perigee image is mid-Summer and our Moon skirts the southern horizon. Because the Full Moon occurs when it is opposite the Sun a general rule of thumb is high-sun/low-full moon in the summer and vice versa in the wintertime.

Have a look at this dramatic moonrise sequence to see the changing colours ...

astro.ysc.go.jp/moon-Di_Nasso_camera.jpg (notice the flattening of the lunar disk too when it's altitude is low)

The brightness of the Full Moon can genuinely change and there was a suggestion in December 1999 that we would have the brightest Full Moon in 133 years. That was not the case but was touted as such because the Moon was at perigee AND high in the December sky so giving the impression of being exceptionally brilliant.

Jean Meeus, in "More Mathematical Astronomy Morsels", mentions that the next really bright Full Moon we get will be that of January 2nd, 2018.

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