LTP Checklist for Obscurations

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

Definition: An “obscuration” is a loss of detail on a certain area of the Moon. For example lack of texture, loss in visibility of small craterlets, or rilles, on the floor of a crater etc The effect should be short term and return to normal after a while.

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

1) Are any other lunar features similarly obscured? If yes it is not an LTP.

2) If the atmospheric seeing (steadiness of the image) is poor then it is probably not a LTP.

3) Check some images of the area in an atlas, or on-line quickly – try to find ones under similar illumination. If the area looks obscure in these images too then it is not an LTP.

4) Try moving the telescope around to see if the effect is caused by vignetting, or optical defects in the eyepiece, or telescope optics. If in doubt try another eyepiece, or even a different telescope. If the effect remains the same then see Observing an Obscuration LTP below.

Observing an Obscuration LTP: 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 to confirm your observation.

2) Briefly check on the appearance of the obscuration, and write a description or take an image.

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 should avoid observational bias.

4) Return to the telescope and sketch what you see, or take images (video?), at regular intervals until the LTP vanishes. This will help us put a limit on the duration and development of the event. If the effect does not vanish after an hour or more, then it becomes less likely that it is an LTP.

5) If observing visually, try using a red, blue, green, or a Polaroid filters to see how the effect appears – is it more or less obscure in these filters?

6) When the nights 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