meteoptic-l [ät] ursa.fi

message archive

This is meteoptic-l [ät] ursa.fi message archive. Note, your can reply the messages on this page only if your are already subscribed the list.

» To the end of the list/message

From: Veikko M{kel{ (PVTMAKELA_at_hidden_email_address.net)
Date: 11/14/1996

• Next message: Paul Schlyter: "Opposition effect"
• Previous message: L-Soft list server at Finnish University & Research Network \(1.8b: "METEOPTIC: error report from NIMA.MIL"

Date: Thu, 14 Nov 1996 08:32:00 -0500 (est) From: "Cornette, William - (I)" <CornetteW_at_nima.mil> Subject: Opposition effect

<snip>

From: Paul Schlyter <pausch_at_saaf.se>
> This "opposition effect" is also responsible for the full moon being
> about ten times brighter than the half moon, and not merely twice as
> bright as could be naively expected, or PI times as bright as if it
> would be if the lunar surface was a perfect diffusor (a "Lambertian"
> reflector).

    Do you have any references for this -- or better yet some data. I have constructed a lunar exoatmospheric irradiance model, which is combined with a solar and lunar ephemeris model. I compensate for:

1. Amount of lunar surface illuminated by sun
2. Variation in earth-moon and moon-sun distance during lunar cycle. There is a total variation in the irradiance of about 26 percent from this.
3. Variation in the albedo of different portions of the moon surface. The irradiance is about 20 percent brighter at first quarter (waxing) than at third quarter (waning) due to differences in the lunar surface.
4. Spectral variation in the lunar albedo (averaged over the whole lunar surface).

       The correction factor for the third factor as a function of lunar elongation is:

      DATA             ELONG /  0., 10., 20., 30., 40., 50., 60., 70.,
     +     80., 90.,100.,110.,120.,130.,140.,150.,160.,170.,180.,190.,
     +    200.,210.,220.,230.,240.,250.,260.,270.,280.,290.,300.,310.,
     +    320.,330.,340.,350.,360./
      DATA             CORREC /0.255,0.259,0.263,0.267,0.271,0.275,
     +       0.284,0.307,0.326,0.361,0.393,0.429,0.465,0.499,0.545,
     +       0.613,0.706,0.829,1.000,0.829,0.662,0.574,0.484,0.422,
     +       0.384,0.354,0.332,0.314,0.305,0.295,0.294,0.292,0.286,
     +       0.267,0.248,0.229,0.210/

    If you have some quantitative values for this brightening due to the opposition effect, which I assume is a sharply peaked value, falling off sharply if the lunar elongation is more than a couple of degrees off from full (180 deg), and any reference, I would appreciate it.

Bill
Cornette

• Next message: Paul Schlyter: "Opposition effect"
• Previous message: L-Soft list server at Finnish University & Research Network \(1.8b: "METEOPTIC: error report from NIMA.MIL"