LTP Checklist for Earthshine Brightenings

The following are based upon the flow charts in Appendix 2 of the “Hatfield SCT Lunar Atlas – A digitally Re-mastered Edition”.

Definition: An “Earthshine Brightening” is where a lunar feature, or a spot, appears brighter than it should do, or where a new (non-feature) bright spot is seen on the lunar night side. It is not related to the brightness of the “whole” of the Moon’s Earthshine, which can vary in the order of tens of minutes and is due to the changes in cloud cover reflectivity on Earth. The transparency of our atmosphere can have a similar effect. Nor does it relate to the brightness of the NW limb of the Moon where the amount of highland area seen against the dark mare varies with libration.

Checks to do: You should follow these steps to eliminate non-LTP causes:

1) Check the TLP location against a Full Moon image and if it is bright on that, then it is not a LTP.

2) Try moving the telescope around, or rotating the eyepiece (or camera). If the feature varies in brightness it could be caused by vignetting, or even glare issues from the day side of the Moon.

3) If brightness changes are the nature of this TLP, do they change with atmospheric transparency or seeing? If so then it is not a LTP.

4) Are clouds passing across the Moon causing these brightness changes? If so then it is not a LTP.

5) Is the suspect feature just at the limit of visibility, and the Earthshine very bright? This is not a LTP.

Observing an Earthshine Brightening LTP: If the above suggest it might be a LTP, then you should do as many of the following, in the suggested order, and do these as quickly as possible because many LTP are short duration events:

1) Identify the feature, or location of the LTP, using a lunar atlas.

2) Is it Aristarchus and is the only feature visible in Earthshine apart from the limb and possibly Grimaldi? TIf yes, then this is perfectly normal. However if you can see Artistarchus with the naked eye (without telescope), then this might be worth reporting as a rare appearance.

3) If Aristarchus is not the brightest feature in evening Earthshine on the Moon, then this is also unusual and might be worth reporting as a LTP after following through the steps below.

4) Quickly telephone, text, or email the LTP coordinator so that other observers can be mobilized.

5) Briefly check on LTP brightness, and write a description, or take an image.

6) Quickly telephone, text, or email a few astronomy colleagues to mobilize them – but do not tell them what you have observed, just the name of the lunar feature. This will avoid observational bias.

7) Return to the telescope and monitor the brightness over time, comparing to other features visible in Earthshine, or to any stars close to the limb of the Moon. If you have a camera sensitive enough to record Earthshine, take an image at least once per five minute to record any brightness variations.

8) Can you see any colour on the feature?

7) When the night’s observing is over, write up your report, including images and sketches and email to the LTP coordinator. Please try to write the report as quickly as possible in case you forget details.

ALPO LTP coordinator: Dr Anthony Cook. Tel/Text +44 798 5055 681. Email: atc @ aber.ac.uk