LTP Checklist for Shadow Effects

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

Definition: “Shadow Effects” LTP can involve temporary glows or visibility of surface detail in shadow areas of the Moon, or shadows that turn temporarily grey before returning to their normal black state. However observers can be tricked by glare from bright areas in their optics, seeing flare, and even scattered light off the inside of illuminated ray crater walls. It is a challenging observational area as one is trying to detect faint detail in dark places with extremely bright illuminated terrain adjacent to this.

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

1) If you can see detail, or greyness, in shadows of other features at the same distance from the terminator, then it is not a LTP.

2) Check a lunar atlas, or an on-line image, at the same stage in illumination, and if the effect is seen here then it is not a LTP.

3) To check for glare effects off of the optics, try rotating the eyepiece or camera, or moving the field of view of the telescope. If it is really on the Moon it should remain static with the Moon.

4) Try changing the eyepiece and/or telescope and if the effect vanishes then it is not a LTP.

5) Is there short term rapid movement of the glow in the shadow, or can you see faint “spur”-like features on bright peaks on the terminator – if so then it is seeing flare.

6) If the crater is a ray crater, or at least bright at Full Moon, check on-line on http://target.lroc.asu.edu/q3/ and see if you can find an image with the crater shadow filled, then zoom in to see if you can see detail inside the shadow – if so it is not a LTP but just scattered light off the bright illuminated walls.

Observing a Shadow Effect 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) Quickly telephone, text, or email the LTP coordinator so that other observers can be mobilized.

2) Briefly sketch, write a description, or take an image of the LTP noting its position.

3) 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.

4) Return to the telescope and sketch what you see, or take images, at regular intervals until the LTP vanishes. This will help us put a limit on the duration and development of the event.

5) Always keep a look out for seeing flare or similar shadow effects on other nearby features

6) If you have filters, what color is it more easily visible in and try a Polaroid filter and rotate it.

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