Good Afternoon All,
I was able to spend about 2.5 hours last night with these eyepieces in my 10"/F5.3 scope. I haven't had this scope all that long and it was a good opportunity to further evaluate the scope also.
Unfortunately the 6mm Carl Zeiss Jena orthoscopic would not come to focus in this scope. It needed about another 6mm or 7mm of focuser intravel to reach focus. As this scope only has 2 collimation bolts on the primary mirror cell (as opposed to the normal 3) I can't push the mirror any further up the cell to adjust the focus point. I am pretty sure this eyepiece will reach focus in my 14"/F4.5 SDM and my 18"/F4.5 Obsession as these scopes are optimised for use with a paracorr which requires more inward travel than a normal eyepiece. However it may not be so easy to get seeing conditions good enough to support the power these eyepieces give in those scopes.
Last night I spend quite a while using Achernar and testing for things like On Axis Star Image Sharpness, Off Axis Star Image Sharpness, Lateral Colour, Internal Reflections and Light Scatter. I also spend some time on the full Moon. As you all know the full moon isn't the ideal time to observe it and do critical evaluation, but I thought I would see if these conditions showed any glaring differences between the eyepieces. The lunar targets I used were around Mare Fecunditatus. I used some craters which had some mountains and internal craterlets, including craters Goclenius and Langrenus. I also spent some time on Dorsa Geike which is a ridge about 250km in length.
As I indicated previously these are all very good high quality eyepieces with excellent on axis performance and the differences between them are going to be fairly subtle. I went into this evaluation very open minded and wanted to evaluate everything 100% objectively. However, I did feel that with the advantage of 15 years of technological advancement the DELOS would be a slightly superior performer to the TV Radian. Well I can tell you the Radian is in this fight right up to it's ears. Whilst I have only compared all the eyepieces on bright high contrast targets up to this time, whatever I have been able to see in the DELOS, I have been able to see in the Radian. In a couple of tests using Achernar the Radian outdid the DELOS. Maybe things will change when we get to dimmer threshhold targets where the expected gains from contrast/light throughput advances in technology, will be more evident and favour the DELOS. On axis sharpness and observable detail with the Nagler Zoom and the UO HD Ortho have also been the equal of the DELOS and Radian, but they have fallen slightly short of the others in a couple of other criteria like scatter control etc when tested on Achernar just outside the EOF. In some of the testing I did on Achernar, the Radian outpointed the DELOS, notably scatter control when Achernar was pushed just outside the FOV (slight advantage to the Radian) and in EOF performance as Achernar was allowed to drift from the centre of the FOV to the EOF. In the Radian the Star image stayed tight for 90% of the FOV and was still very good and useable right to the field stop. The DELOS was not as good, with the star image deteriorating from 70% of the way off axis and being essentially unuseable in the outer 10% of the FOV. Granted the DELOS has a 20% larger FOV but the Radian was clearly better in this regard for mine. I will do further critical evaluation on the EOF performance of these eyepieces using some testing double stars over the coming weeks. This testing was also conducted without a paracorr and when seeing permits I will also conduct these tests with a paracorr in the 14"/F4.5 scope.
If you own any of the eyepieces in this review you can take comfort from the fact they are all very good ones with minimal differences between them on bright high contrast targets.
As an aside, whilst I didn't compare the 7mm Pentax XW to any of the 6mm eyepieces on the Moon, as the magnification difference was too great, I did include it in my evaluation on Achernar in terms of its on axis and off axis sharpness of star image, EOF lateral colour on Achernar and internal reflection and scatter control with Achernar just outside the EOF. What I can tell you is that I will not be selling any of my XW's in a hurry.
Stay tuned. Lot's more to follow as we get to some varied and more testing targets. Hopefully these will start to sort out the men from the boys.
I like the new DELOS a lot but I can tell you the 6mm Radian is also impressing me on these bright high contrast targets.
Cheers,
John B
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