Overall Impressions:The Starbase 25mm Kellner is very small – smaller even than the stock 20mm plossl that came with my scope. It looks downright puny in my prism, but, the build seems quite solid and it has a good weight in the hand. It needs more back focus than my other eyepieces – about one cm – to come to focus.
The previous owner flocked the barrel, as it was not blackened originally. The barrel is threaded, but for right now I’m not going to take off the flocking. Eventually, I will since I want to use this eyepiece with my nebula filter!
I spent about 2 and a half hours over three sessions comparing the Starbase 25mm Kellner to my Vixen 20mm NLV and my Celestron zoom set at 24mm (Unfortunately, I don’t have another 25mm eyepiece, but I thought these two would give a decent comparison). This has been a really fun experience for me. I have been so focused on double stars lately, and in particular hard to split tight pairs, that I’ve kind of forgotten how different things look at lower powers. Kind of like I have lost the forest for the trees.
Overall, my first impression is that it is a really good little lens – as comfortable as the NLV and the zoom lens in regards to eye relief and eye placement (no black outs or kidney beaning), and views that were similar to the two other eyepieces, if not better in some cases (see my observing notes below). The top lens in smaller than the NLV and the zoom, but it wasn’t noticeable when switching between eyepieces (unlike say the top lens of the NPL15 I have, which is not small, but still much tighter than the NLV and the zoom)
Other than having to rack the focuser in and out when shifting from the NLV or the zoom to the Starbase, there really wasn’t much to show the difference between the EPs. The very edge of the Starbase seemed a touch “muddy,” but the field stop was well-defined (It may be my eyes, as I had similar muddy edges using the 30mm and 40mm NPLs). I did not see any distortion at the field edge when stars or doubles drifted out of the FOV, but then again my scope is an f11.
I didn’t see any hugely noticeable differences in color between the three EPs, but sometimes the fainter stars just seemed to “pop” a little more in the Starbase and become more noticeable – this was true even when comparing the views in the 25 and the zoom 24, which would have quite similar exit pupils.
One interesting thing to note is that when I checked the magnification of the eyepiece when it was barlowed with my x2 barlow using the ruler test, the magnification was only 1.9 times greater (not a huge difference, but in this barlow, all my other eyepieces have been x2 or x2.1).
For $18 I feel like the Starbase Kellner was a steal, and would have been happy to pay full price. Makes me think of picking up one or two of the Starbase Orthos!
First light was a quick look at Achird (eta Cassiopieae) – Have gotten so used to looking at doubles with 100 + power, that I’ve forgotten how small 12 arcminutes is! Achird was so tight with the Starbase (x36) that I almost couldn’t split it, but I was able to see a little purple dot hanging there next to the big milky-yellow one. With the NLV 20mm (x46), the secondary was much more obvious, but this was due to the higher power, and not much of a difference in overall brightness or contrast between the views with the two eyepieces.
My second target was Struve 254 (a.k.a – WZ Cassiopieae) The NLV20 showed the primary to be a bright intense orange red, and the secondary to be a faint medium blue (indigo by my eyes).
The eye relief of the Starbase is fine and seems similar to the NLV. Both stars, especially the primary seem “brighter,” and to have a more intense hue (but this may just be due to the difference in exit pupil). The FOV was not much bigger, but the little bit of extra field seemed to frame the binary better — it gave a little more context. More interesting is that I noticed a line of dimmer stars to the right & below the primary. They hadn’t registered in the NLV20, but they stood out in the Starbase. In the NLV20 they seemed more like random background stars, while in the Starbase, they became a distinct pattern. Maybe they were brighter in the Starbase, but they weren’t dim in the NLV20, and when I looked again, the line was there, just not as apparent.
My next target was NGC457 – initial impression is of quite similar views. The light of the moon is probably washing out the colors of the stars – the “eyes” of the “owl” looked white and yellow, and just the most basic frame of stars is visible. Here too the 25 seemed to show more brightness on the stars, but again, probably not much more than would be expected with a larger exit pupil.
Bill Paolini noted a similar experience, “At times I was feeling that the background sky was a little starker or darker in the Starbase as an overt impression but could not nail it down as so more critically observing, so interesting that it gave that initial impression at first glance.”
In all fairness, and in full disclosure, when I revisited 254 and 457 a couple of nights later and compared the views in the NLV20, the 24mm zoom and the Starbase, the differences were not as pronounced in the line of stars, and the views between the three eyepieces was quite similar. However, on the same night I noticed the effect again (the Starbase showing brighter stars or more contrast with the background) when observing Miram (eta Persei).
Primary: average medium yellow secondary dim pale purple blue (shifted to grey once I became accustomed)
Zoom 24 (x 38)- Spare area of the sky. Pair clearly separated but lonely.
Starbase 25 (x36) – Definitely wider FOV (no surprise here! 24 is only 40 AFOV).
Surrounding stars seem just a hair brighter. Not really noticeable if you weren’t looking for it, but somehow they do.
Like the view from the Starbase 25 better – wider framing and something about the contrast between the stars and the sky.
Zoom 24 (x38) – Clearly split; primary was a bright intense yellow, secondary a small average white star (surprising that the color was not apparent here!)
Starbase 25 (x36) – Two are touching, brightness and color similar to the 24
NLV20 (X46) – Shows hints of pale green in the secondary
Starbase 25 (Barlowed to x68)- Clear split here, Primary: bright pale yellow, secondary: bright pale green (interesting that the higher magnification has dimmed down the primary a bit and made the color in the secondary more apparent)
Zoom 12ish – very similar view – no significant differences.
Starbase 25 (x36): no scatter or reflection that I could notice (until the star was touching the edge of the eyepiece, and then there was a small glint that ran up the side of the barrel). I was looking for it, but it was not offensive, may not have even noticed it if I weren’t looking closely for it. The star was sparkling a bit, but was not distorted. Was able to split the pair using the barlow (x68). The primary was very bright intense blue-white. The secondary was a very small, but, bright average white dot, just below and to the right (I guesstimated PA was about 210) Rigel was sparkly (i.e., not a clear disc, a bit edgy) but the secondary was clearly visible (confirmed the split and position using the zoom at 8 power (x114)).
Starbase 25 – Nicely framed in the EP – filled but with room to spare on the sides.
There seemed to some chromatic aberration (purple around the upper third, and yellow around the remaining two-thirds) But, I was viewing it early in the evening, as everywhere else was hidden clouds, and it was quite low in the sky and simmering at the edges). There was no distortion that I could notice as the moon moved out of the FOV, and no internal reflections or scatter that I could notice. The view seemed as sharp at the edge of the FOV as it did center axis, and there was no discernable difference between the views with the Starbase 25 and the Zoom 24 – if anything I had the feeling that the Starbase 25 was giving a bit more sharpness, and pop, to features like Tycho’s rays.