what’s the difference between these two telescope lenses?
Wednesday, December 15th, 2010 at
6:24 am
what's the difference between a 45 and 90 degree angle?
http://www.celestron.com/c3/product.php?ProdID=330&CatID=49
http://www.celestron.com/c3/product.php?ProdID=332
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US $125.02
Both of those are called DIAGONALS not lenses.
They are both ERECTING diagonals which are used for terrestrial viewing and usually NOT for objects in the sky.
One is 90 degrees and the other is 45 degrees. For terrestrial use I would buy the 45 degree, easier on your NECK!
For astronomical use I would buy this type of diagonal:
http://www.astronomics.com/main/Asronomy_echnologies_2%E2%80%9D_99_refleciviy_dielecric_mirror_diagonal_wih_com.asp/catalog_name/Astronomics/category_name/New%20Products/product_id/AT2D
These are not “lenses”; they are erecting prisms. You insert them in between your telescope’s focuser and your eyepieces. Both convert the normally inverted telescope image to an erect image. With the 90° version you look into the telescope from above, 90° to the optical axis of the telescope. With the 45° version, you look in at a 45° angle.