Eek! You're right. But the issue is further confused by the discussion of distortion in lenses here:
in which the radial distortion coefficient K(sub n) is negative for pincushion distortion and positive for barrel distortion.
Though I do understand the idea in that book that pincushion results from a lateral (positive) stretching of the image, and barrel the opposite, I cannot reconcile that with the math that shows if the distortion coefficient is negative you get pincushion.
Perhaps this should become a different thread so not to hijack the discussion of the review of eyepieces.
TEC140 (#216) Leica 17.8...8.9mm ASPH Zoom also barlowed 1.5x/2.0x/2.5x with Baader VIP Modular Barlow WO UWAN 28mm Baader 2" Herschel Wedge with SolarContinuum filter AYO AltAz mount on a Berlebach UNI19 tripod (sold: Zeiss AOII set with Zeiss Abbe 2x Barlow, see Leica zoom vs. ZAOII)
1961 8" F8 Criterion Dynascope Deluxe (dob mount) C6, Celestron GT102 ,PST Vixen Ascot 10x50,12x50 Pentax PCF WP II Denk big easy pairs of TV 32mm,11mm plossls, celestron 25mm plossl, 17mm sterling, 9mm X-cel LX, 20mm superviews AT 17mm 70 AF, 8mm AT Paradigm, AT 12mm plossl ES 82* 6.7mm,11mm,14mm,ES 68* 24mm 2.25x Ultima Barlow VT 25mm Ortho, BCO 10mm,18mm, TV Plossl 15mm,26mm, GSO 40mm plossl, 20mm sterling 1 dog, 3 cats, 2 sons and a beautiful wife
Quote: Looks like it was much harder than the earlier ones, with so many different targets and qualities to examine.
The opinions expressed herein are solely mine as an amateur astronomer hobbyist & consumer. Information herein was correlated from experience, discussions with others, & research from multiple sources freely available at time of posting. All reasonable care & skill was used, but no warranty is made as to accuracy, & liability cannot be accepted for errors/omissions. This is for information only and not intended nor implied to be a substitute for professional advice.
Quote:Barrell (left) Pincushion (right)
Clear skies - Jim Crazy PNW imager !
A-P Mach1 on 12" concrete pier - ROR structure.
Tak FSQ85-EDX, Tak FS-128. Orion 8" f/3.9 w/MoonLite motorized - MPCC MkIII CCD:
SBIG 8300M/FW8, Astrodon 36mm LRGB, 5nm Ha, 3nm SII, OIII - Canon EOS 6D unmod SSI3, SSAG,
Skytools3pro, MaxImDLpro, PSCS5, PSPpro, TheSkyX, TheSky6, BYE, StarTools
Orion XX14g -for visual- diags, ep's, accy tubes, Binocs .