How to identify grades of lenses?

is there anywhere I can find how to differentiate between the different grades of lenses, either here or on another site?

Dustin gave me this link to a paper that I have been using as a guide…

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I am not sure. Maybe there is something official out there. I personally don’t grade lenses. It might make sense for a writing a paper, but I think if you think you found a great lens, then just post it in a discussion.


From the SuGOHI paper:

"(…) We then visually inspected the resulting sample with the purpose of refining the candidate classification. Nine co-authors of this paper assigned to each candidate an integer score from 0 to 3 to indicate the likelihood of the subject being a strong lens. We used the following scoring convention:

  • Score=3: almost certainly a lens. A textbook example for which all characteristics of lensed images are verified: image configuration, consistency of colour and, in case of extended sources, surface brightness among all images. Additionally, the possibility of lensed features being the result of contamination can be ruled out with high confidence.
  • Score=2: probably a lens. All of the features match those expected for a strong lens, but the possibility that some of the features are due to contaminants cannot be ruled out.
  • Score=1: possibly a lens. Most of the features are consistent with those expected for a strong lens, but they may as well be explained by contaminants.
  • Score=0: almost certainly not a lens. Features are inconsistent with those expected for a strong lens.

Additionally, in order to ensure consistency in grading criteria across the whole sample and among different graders, we proposed the following algorithm for assigning scores.

  1. Identify the images that could be lensed counterparts of each other
  2. Depending on the image multiplicity and configuration, assign an initial score as follows:
  • Einstein rings, sets of four or more images, sets consisting of at least one arc and a counter-image: 3 points.
  • Sets of three or two images, single arcs: 2 points.
  1. If the lens is a clear group or cluster, add an extra point up to a maximum provisional score of 3.
  2. Remove points based on how likely it is that the observed features are the result of contamination or image artefacts: if artefacts are present, then multiple images may not preserve surface brightness, may show mismatch of colours, or may have the wrong orientation or curvature around the lens galaxy.
  3. Make sure that the final score is reasonable given the definitions outlined above.

The rationale for the third point is to take into account the fact that
(a) groups and clusters are more likely to be lenses, due to their high mass concentration and
(b) often produce non-trivial image configurations which might be penalised during the fourth step.

Finally, we averaged the scores of all nine graders,and assigned a final grade as follows:

  • Grade A:〈Score〉>2.5.
  • Grade B: 1.5<〈Score〉<=2.5.
  • Grade C: 0.5<〈Score〉<=1.5.
  • Grade 0:〈Score〉<=0.5."