Hi All,
I've owned the Pentax XF 6.5mm-19.5mm zoom EP for some time now and had a chance to really ring it out at the Grand Canyon in June. This is no formal review, but here's what I found.
First as Zooms go, this is a good one. It doesn't remain perfectly parafocal, but the others I have owned didn't either. The Celestron 8mm-24mm was useful, but had bad kidney bean effect. The TeleVue and Vixen (I've owned both) are much better, but still had some kidney bean to deal with. The Pentax has none and is quite clear, up to a point.
That point is when I have brilliant seeing like the first Sunday night at GCSP, and could compare it to some high quality fixed focal length EPs. The types compared were Takahashi LEs in 7.5mm, 10mm and 12.5mm focal lengths, and a Baader Orthoscopic in 6mm focal length. The scope used was an Alter M10/10 Maksutov (Intes Micro) with a focal length of 2540mm (10 inch/f10).
Reading a report like this one only goes so far. You have to see the results with your own eyes to know how you perceive what's being observed.
The results against the Takahashi's were good but not better. When compared to a Celestron or Vixen fixed fl EP the Pentax was much better, but against those mentioned some graininess started showing. It didn't before. Hmmm... Against the Baader, same thing, but the Orthoscopic is much more sensitive to eye position as most are.
OK, does that mean the zoom is no good? Not at all, it just didn't come accross as "crisp" compared to known high quality EPs. At that point it becomes moot to compare to fixed focal length EPs of even higher quality. Yet it did beat the TeleVue 8-24 zoom in previous observation. This comparison was only against the fixed EPs. OK, so it only proves this one EP shows a hint less clarity than some really good EPs under near perfect conditions.
Let's back up to the phrase "Star Party". Using the zoom on Saturn, cloud bands were clear, Cassini division was detectable, but not clear (same as in the fixed EPs) and the rings and moons seemed tack sharp. Well the rings are just now opening up. So I tried a few clusters. Internal reflections might be to blame, but the contrast on the lagoon was better in the TAKs. I got a bit of haze, but no grain in the Zoom. Details and light gathering in the Swan were about the same in zoom or fixed.
As a crowd pleaser able to negate the need to change EPs for most of the evening, it worked out very well indeed.
I have not observed through any other top end zooms, but would certainly recommend this one.
Thanks,
Steve
8)
I've owned the Pentax XF 6.5mm-19.5mm zoom EP for some time now and had a chance to really ring it out at the Grand Canyon in June. This is no formal review, but here's what I found.
First as Zooms go, this is a good one. It doesn't remain perfectly parafocal, but the others I have owned didn't either. The Celestron 8mm-24mm was useful, but had bad kidney bean effect. The TeleVue and Vixen (I've owned both) are much better, but still had some kidney bean to deal with. The Pentax has none and is quite clear, up to a point.
That point is when I have brilliant seeing like the first Sunday night at GCSP, and could compare it to some high quality fixed focal length EPs. The types compared were Takahashi LEs in 7.5mm, 10mm and 12.5mm focal lengths, and a Baader Orthoscopic in 6mm focal length. The scope used was an Alter M10/10 Maksutov (Intes Micro) with a focal length of 2540mm (10 inch/f10).
Reading a report like this one only goes so far. You have to see the results with your own eyes to know how you perceive what's being observed.
The results against the Takahashi's were good but not better. When compared to a Celestron or Vixen fixed fl EP the Pentax was much better, but against those mentioned some graininess started showing. It didn't before. Hmmm... Against the Baader, same thing, but the Orthoscopic is much more sensitive to eye position as most are.
OK, does that mean the zoom is no good? Not at all, it just didn't come accross as "crisp" compared to known high quality EPs. At that point it becomes moot to compare to fixed focal length EPs of even higher quality. Yet it did beat the TeleVue 8-24 zoom in previous observation. This comparison was only against the fixed EPs. OK, so it only proves this one EP shows a hint less clarity than some really good EPs under near perfect conditions.
Let's back up to the phrase "Star Party". Using the zoom on Saturn, cloud bands were clear, Cassini division was detectable, but not clear (same as in the fixed EPs) and the rings and moons seemed tack sharp. Well the rings are just now opening up. So I tried a few clusters. Internal reflections might be to blame, but the contrast on the lagoon was better in the TAKs. I got a bit of haze, but no grain in the Zoom. Details and light gathering in the Swan were about the same in zoom or fixed.
As a crowd pleaser able to negate the need to change EPs for most of the evening, it worked out very well indeed.
I have not observed through any other top end zooms, but would certainly recommend this one.
Thanks,
Steve
8)
