I have the above Fieldscope that I have owned from new since 1996. For me, for the most part, it's been a fantastic piece of equipment - really bright and sharp image with the 30x wide angle eyepiece, not quite so bright but still sharp at the upper end of the range of zoom on the 25 - 56 x zoom. I've recently become more interested in waterfowl/waders and sea watching where a brighter and less restricted zoom eyepiece would be useful. As such I started looking into the alternative options available and have been reading through some of the threads on this forum. I have to admit, it has been quite an eye opener in terms of the recommended caution that I should take before buying a new scope - I never before appreciated how variable the quality of a premium brand scope might be.
So, I read up a little on how to do a star test and thought I would try it on my Fieldscope so that I know what do do when I come to inspect other scopes. Because the image is so sharp on my Fieldscope I fully expected to see something close to an identical set of concentric rings wholly within the bright spot. This turned out not to be the case. Unfortunately, I wasn't able to photograph the image I was getting so I've sketched out what I saw and attach that sketch. In essence, at one side of the focus point the concentric rings were displaced to the left of the bright circle. At the other side they were displaced to the right by an equal amount. If you rotate the attached image by 90 degrees you'll get the gist of what I'm seeing. The displacement was large - less than half (of the full circle) of the concentric rings was visible each time. If I moved my eye across the eyepiece a bit I could see a bit more of the concentric rings but not much more.
I have a couple of questions that I'd like your help with please:
1) Is it possible that I am doing the star test incorrectly and, in doing so, it is producing what appears to be an extreme result? If so, what might I be doing wrong? (I did try moving closer or further away from the star and also changed the eyepiece - neither seemed to affect the result I was getting).
2) If the answer to 1) is 'no' and the test is likely to be good, what does the result indicate is wrong? How should this affect the image of birds etc. that I see through the scope?
Grateful for any thoughts / suggestions you may have on this.
Thanks
David
So, I read up a little on how to do a star test and thought I would try it on my Fieldscope so that I know what do do when I come to inspect other scopes. Because the image is so sharp on my Fieldscope I fully expected to see something close to an identical set of concentric rings wholly within the bright spot. This turned out not to be the case. Unfortunately, I wasn't able to photograph the image I was getting so I've sketched out what I saw and attach that sketch. In essence, at one side of the focus point the concentric rings were displaced to the left of the bright circle. At the other side they were displaced to the right by an equal amount. If you rotate the attached image by 90 degrees you'll get the gist of what I'm seeing. The displacement was large - less than half (of the full circle) of the concentric rings was visible each time. If I moved my eye across the eyepiece a bit I could see a bit more of the concentric rings but not much more.
I have a couple of questions that I'd like your help with please:
1) Is it possible that I am doing the star test incorrectly and, in doing so, it is producing what appears to be an extreme result? If so, what might I be doing wrong? (I did try moving closer or further away from the star and also changed the eyepiece - neither seemed to affect the result I was getting).
2) If the answer to 1) is 'no' and the test is likely to be good, what does the result indicate is wrong? How should this affect the image of birds etc. that I see through the scope?
Grateful for any thoughts / suggestions you may have on this.
Thanks
David