keybaud Posted February 13, 2016 Share Posted February 13, 2016 (edited) I have a Skywatcher MN190 and recently acquired an Oticstar ED80S, both of which I bought second hand. I'm now starting to build up the eyepieces I think I will need and I have read up on eyepieces, to better understand FOV, TFOV, focal length, exit pupil and all the other factors that affect how they behave. As a result of this, I decided to try and find reasonable quality 82 degree eyepieces and to keep the number I buy as low as possible, whilst giving me the best options to choose from. I played with Excel and created a table that would calculate the eyepiece focal lengths I should consider, by keeping the magnification difference between each eyepiece constant. I have a Hyperion 2.25X Barlow, so the calculations also took this in to account. I then added eyepiece focal lengths to the spreadsheet, so that each increase in available focal lengths provided a 50% change in magnification and ended up with the following: 2.1mm (Barlow 4.7mm) - n/a 3.1mm (Barlow 7mm) - 49% 4.7mm (Explore Scientific 4.7mm) - 51% 7.0mm (Skywatcher Nirvana 7mm) - 49% 10mm (Barlow 23mm) - 46% 15mm (Barlow 34mm) - 48% 23mm (Don't have one yet) - 52% 34mm (Meade SWA 34mm) - 48% is my logic sound or am I missing out of the emotional aspect of purchasing eyepieces or something else more fundamental? Edited February 13, 2016 by keybaud Link to comment Share on other sites More sharing options...
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