Home / Rini 30mm 1.25" Eyepiece
by Alexander Pruss 12/10/09 | Email Author
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I am in Central Texas, and am still very much a beginner, with about
1.5 years of experience. I have three fast dobs: homemade F/4 8",
Coulter F/4.5 8" and Coulter F/4.5 13.1", and a fast homemade achro,
F/5.3 68mm, which tends to be the finder of the 13.1".
Paul Rini made his eyepieces at home, in the 90s, as a labor of love
and sold them for extremely low prices. Telescope Warehouse (
continues to sell some Rini eyepieces. The 30mm 1.25" Rini is
advertised as having a 60 degree AFOV and 15mm eye-relief, and sells
for $25.42, with free shipping in the U.S. Comes with bottom and top
caps, and is threaded for filters (apparently some earlier Rinis
When I got it, this was a gigantic eyepiece to me, weighing in at a
whopping 7 ounces. But it doesn't look big beside my Hyperion 13mm.
There is no eyecup. Instead the top of the eyepiece has a T-thread.
I had a front light-shield from an old dead camcorder that fits over
the thread very nicely, and makes a very nice eyecup. Without that,
it would be hard to position the eye. I think I'd make a cardboard
eyecup for it if I didn't have the shield. The barrel is nice, black
and smooth, and there is a clear "RINI 30MM" stamped on it.
The eye-lens is not edge-blackened, and I assume the other lenses
aren't either. Both the eye-lens and the field lenses are coated.
In daytime, I would have to move my eyes a little to see the edges of
the field of view, and there was an odd distortion in the last five
percent by diameter--as if suddenly there was a boundary between glass
surfaces, with a visible and sharp bend. The field stop is out of
focus. At night, none of this bothers me. However, in my F/4.5
scopes, the outer 20% or so (by diameter) of the field of view has
stars distorted into little lines, and a little more in my F/4 scope.
I carefully measured the true field of view on my F/4.5 8" to be 1.65
degrees, by finding two stars near assiopeia that distance apart.
With the advertised 60 degree AFOV, I would have expected 2 degrees,
so something's off. That basically corresponds to what one would
expect from an ordinary 52 degree AFOV 30mm Plossl. But the AFOV of
the Rini is definitely wider than a Plossl's--it is much more pleasant
to look through--though it looks narrower than the 60 degrees
advertised. I would estimate it somewhere half way, maybe around 56
degrees. That means that the eyepiece isn't actually a 30mm, but
closer to 27mm.
The eyelens is very large and, once one manufactures an eyecup, the
eyepiece is very comfortable to use.
When I got it, I was disappointed by the TFOV being lower than I
expected, but I decided it was a keeper when I looked at the Double
Cluster from my backyard with my F/4.5 8", and saw lovely pinpoint
stars, some of them sparkling red. I had not seen color in the Double
Cluster before and was sold. Though, to be honest, I haven't seen
color in the Double Cluster since, so I guess it was just a lucky
night. But it was a very nice view.
On Jupiter, I do get false color, but this is an eyepiece for wide
views. Pieces of the Veil look great in it through my 13".
The Rini 30mm continues to be my finder eyepiece for all my
reflectors, and at $25 seems quite a good, slightly wider alternative
to a cheap 30mm Plossl, and a step up in quality from the 27mm Kellner
that my Coulter 8" came with.