lhuchison Posted May 18, 2013 Share Posted May 18, 2013 I've just ordered a 40mm series 3000 meade as i've read really good reviews on their quality and i need a good wide field 1.25 lens. the supplier says these are the last japanese made ones, but.....i cant work out the fov i'll get in my edgeHD 8in SCT. After reading through forums on true FOV and actual FOV and how to work it out, i'm still confused!It states: the PL40mm produces, for example, a power of 50X and actual field of 0.88°, almost two Moon-diameters, with an 8" f/10 Schmidt-Cassegrain"i cant get to that result using my calculations! 2000 / 40 = 50 , 50 / 44 (apparent field) = 1.13where am i going wrong? Link to comment Share on other sites More sharing options...
Ben Ritchie Posted May 18, 2013 Share Posted May 18, 2013 True field of view = field stop diameter x 57.3 / telescope focal length.1.25" format long focal length eyepieces are limited by the barrel size. The largest field stop you could possibly get in the 1.25" format is 31.75mm, which would be a TFOV of 31.75 x 57.3 / 2000 = 0.91 degrees. In reality you have to have a bit less than 31.75mm due to the thickness of the barrel, so 0.88 degrees seems right.If you want wider true field of view then you need a 2" format eyepiece Link to comment Share on other sites More sharing options...
Ben Ritchie Posted May 18, 2013 Share Posted May 18, 2013 By the way, you need TFOV = AFOV/magnification, so you have the formula upside down. 44/50 = 0.88, although some sites give the AFOV for the s3000 plossl as 38 degrees not 44 degrees so it may be a bit less. Link to comment Share on other sites More sharing options...
lhuchison Posted May 18, 2013 Author Share Posted May 18, 2013 Thanks Ben, question answered! I have a 2in 32mm but was looking for a 1.25 to help scope balancing , my Panaview is quite weighty, Link to comment Share on other sites More sharing options...
Ben Ritchie Posted May 18, 2013 Share Posted May 18, 2013 Yeah, balance can be a right pain at times with long focal length widefields, especially if you're swapping between tiny higher-powered eyepieces that weigh next to nothing and the 2lb monsters.The only thing that immediately springs to mind are the TMB paragons (+clones), they have a reputation for being a bit lighter than other long focal length SWAs but I don't know if it would be enough to make a difference. Link to comment Share on other sites More sharing options...
lhuchison Posted May 18, 2013 Author Share Posted May 18, 2013 I'll check those out. Thanks Link to comment Share on other sites More sharing options...
michael.h.f.wilkinson Posted May 18, 2013 Share Posted May 18, 2013 I use a Nagler 31T5 on one end of the SCT, and have had no problems, that beast weighs in at 1kg. With a 2" diagonal I would go for a Panaview 38 or Aero 40mm (the latter is a Paragon clone). I had a 40mm Paragon, and it was just 500 g as I recall, very light for such a big EP, but well built. Link to comment Share on other sites More sharing options...
faulksy Posted May 18, 2013 Share Posted May 18, 2013 as michael the sw aero 40mm is very light and well built Link to comment Share on other sites More sharing options...
lhuchison Posted May 18, 2013 Author Share Posted May 18, 2013 Yes, that SW aero does look good Link to comment Share on other sites More sharing options...
Dunkster Posted May 18, 2013 Share Posted May 18, 2013 I also use one or more heavy-ish eyepieces on my SCTs. When I setup, I plan which eyepieces I intend to use and balance using one somewhere in the middle weight-wise. Link to comment Share on other sites More sharing options...
Dunkster Posted May 18, 2013 Share Posted May 18, 2013 Sorry, duplicate Link to comment Share on other sites More sharing options...
lhuchison Posted May 18, 2013 Author Share Posted May 18, 2013 I try the same but the 2in Panaview is a lot heavier than my set of x-cels.the Panaview gives great views so I was hoping to get near that with a good 40mm ( in my price range) you can't beat a good 2in wide lens though, I have heard that this 40mm series 3000 Meade has some nice immersive qualities. Link to comment Share on other sites More sharing options...
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