Four areas are available:
- Mare Humorum
- Mare Nectaris/Fracastorius
All of these calibrated crater sequence images were made using the Bowker & Hughes Lunar Orbiter atlas scaled images, sizes measured to the nearest 1/128th of an inch using steel machinist’s scale and 8x magnifying loupe.
The sizes are accurate to +-100meters on craterlets <4km diameter, +-200 meters otherwise. Note: Imaging artifacts (over/underexposure, variable degrees of focus) on the CLA images used may make some craterlets appear larger or smaller than they appear on the higher resolution Orbiter images.
Some craterlets are not resolved on the images except as undifferentiated ‘spots’. Nevertheless, their positions are accurately indicated. I tried to measure only craters which are simple in form and not sub-resolution multiples or ruined irregular craterlets.
NOTES ON USING THESE CHARTS:
These charts can be used to assess both the state of seeing and available resolution during visual observations.
*For “best optimal seeing” and/or ground resolution assessment*
Craterlet size resolvable as a craterlet/depression, not an undifferentiated spot:
3.8-4km = ~2″ arc best seeing/resolution
2.8-3km = ~1.5″
1.8-2km = ~1.0″
1.75-1.5km = 0.8″
1.3km = 0.7″
The above is based upon mean lunar diameter where 1.86km = 1.0″arc. Resolution of craterlets as undifferentiated spots will be higher by a factor of at least 2 from the above figures, depending on local contrast.