by Jim Ster
Good to hear from you again. Hopefully the astronomy gods will grant us another evening of clear skies and we can all get together for another great night of exploring some eye candy in Leo and Virgo soon.
I also took advantage of the brief window of opportunity on Thursday evening. I popped over to Jane's to do first light and some side by side comparisons with her new Tele Vue 3 - 6mm Nagler click stop zoom eyepiece from her driveway in beautiful downtown Davis. And while we were at it, we also gave her new eq platform a trial run. I brought along my TV-85 to augment her 12.5 Starmaster for the evening. I also brought along my box-o-Naglers and my binovues as well. As it turned out, we ended up with 5 of Jane's neighbors stopping by and we were able to give them a little taste of our hobby. Jane's new platform has made her scope at least 3" taller and the 3 college kids that live across the street were blown away by its well over 6' high stature. There was a lot of moisture in the air and all the equipment needed severe drying out afterwards. We were only able to get 4 stars in the Trapezium and Saturn, which was almost directly overhead in the leading edge of an approaching bank of high altitude moisture, was mostly a colorless bore. Jupiter was definitely the star of the brief night. We finished up the evening by using the binovues on it. What an awesome view. I swear it seemed to have twice the detail when viewed threw the binovues as compared to a single eyepiece.
For the record, we didn't bother wasting time to properly align the platform for a variety of reason. The western skies had a wall of high thin clouds moving in that ultimately ended our observing by 9:00 and we didn't want to waste any time. Polaris was also partially obscured by a nearby tree and telephone poles with streetlights. Despite the lack of proper alignment, it worked flawlessly. At one point Jane became rather frustrated when it seemed that it wasn't tracking properly. After a minute of trouble shooting the clock-drive cables and whatnot, she realized that the platform had run out of travel and simply needed to be reset. Even without proper alignment, it was still an absolute joy to be able to take long leisurely observations of Jupiter's bands and actually watch a moon shadow transit for a while.
We were able to do some very interesting comparisons of Jane's new 3-6mm zoom against a couple of other TeleVue eyepieces, a 6mm Radian and a 4.8mm Nagler. Although it wasn't a direct comparison, we also used my 7mm Nagler to gage the lower end of the zooms magnification range. First light for the new Nagler Zoom eyepiece was on Jupiter, set at 6mm, thru Jane's Starmaster which yielded about 265x and provided a very nice view. Very nice indeed. There were 4 moons clearly seen and the colored banding was wavering in and out slightly, probably due to the mirror not having quite reached thermal equilibrium. We then put it into the TV-85 and were quite please with the view at 100x. I then gave the knurled ring a twist and zoom, the little refractor was instantly at 200x and due to the Zooms being para-focal across its entire range, it was still in sharp focus. The view was still quite spectacular. After a brief and rather uneventful trip over to Saturn and the Orion Nebula (something to do while Jane's mirror settled) we moved back to the 12.5" and on to the eyepiece comparisons.
We chose Jupiter as our object de jour and beginning with the 6mm Radian and the Nagler Zoom set at its 6mm stop, we began some very patient observations thru each eyepiece. We assumed that it would be a very close call considering Tele Vue's reputation for building fine eyepieces in a variety of styles, but we were quite surprised to find that there was some pretty dramatic difference between them which were readily apparent. First, some technical notes. The Nagler zoom only has a 50 degree FOV (thru its entire range) as compared to the 82 degree of standard fixed focal length (FFL) Naglers and the 68 degrees of the Radian series. But don't let that scare you off from one. Despite the Radians reputation for excellent contrast and black background, the little zoom had dramatically better views with noticeably blacker back grounds and the contrast was so much better that we were able to discern at least 5 additional bands on Jupiter in the Nagler Zoom than the Radian as well as significantly brighter colors. Hands down, the little zoom won. Not even close.
When we compared the standard 4.8mm Nagler (and the 7mm as well for that matter) for the most part, we both felt that the compact zoom held it's own. They all produced very dark backgrounds and yielded similar results on Jupiter's bands. After 20 minutes of looking for subtle variations, I think we both agreed that the FFL Nagler eyepieces "might possibly" have had an very slim advantage, but I think it's fair to say that the seeing wasn't stable enough nor did we to do enough comparison to form a definitive opinion. I have to admit that I was very impressed with this eyepiece and will probably make the investment in one in the near future.