Quote:
|
Originally Posted by DRCORTEX
I read the advice, thought about it, read it again, then went ahead and purchased a 4mm GSO Plossl and jabbed it into a 2X Barlow - the result 
I am going to get one of these wide field 80 degree 11mm from the Andrews catalog - they look allright.
Hope its clear tonight at Linden - I want to "borrow" a few eyepeices ( especially the ones that have chains/dogs/alarms, connected to them ), and see exactly what the differnce is.
Lance
Lance |
Lance,
You need to appreciate your scope has a fast F-Ratio of F5, this is very "unforgiving" of cheap widefield eyepieces. The reason for this is because the angle of entry, of the light cone, into the field lens of the eyepiece increases exponentially as the F-Ratio of the telescope gets faster. In other words the light enters the eyepiece "closer to the edge" of the lens and away from the central axis.
That 11mm 80 degree Andrews eyepiece in an F5 scope would be Lesson Number 2
When you have a scope with an F-Ratio of F5 you basically have 2 options only if you want good images and sharp stars towards the edge of the FOV.
Option 1. Buy premium widefield eyepieces at $400 to $500 each, these work well in an F5 scope. I would also warn you that a lot of the intermediate priced widefield eyepieces at $200 to $400 perform very poorly in an F5 scope. These include 2" UO Konigs and Widescans. These eyepieces do however work very well in slower F8 to F15 telescopes.
Option 2. Buy high grade simple design eyepieces like plossls and orthoscopics.
By high grade I do not mean the plossls that came with the scope, or what Andrews sells, these are fair and that's being very generous. High grade plossls are things like Celestron Ultimas, Parks Gold Series, Orion Ultrascopic, Antares Elite. Televue PLossls and University Optics orthoscopics are also very good. These will cost you between $100 and $200. These eyepieces give image quality as high as any of the premium widefields, the downside is the slightly narrower FOV and decreasing eye-relief as the focal length of the eyepiece decreases. These were exactly what you were needing but I think Dave has sold them.
http://www.iceinspace.com.au/forum/s...ead.php?t=7348
CS-John B