I am very happy with my Stellarvue finder scope as well as the rings and the cross hair illuminator
A bit ragged at the edge of the field, but that could be my glasses. The rotating back makes it easy to change the orientation of the eyepiece, and while it changes the position of the crosshairs, rotating back to the original position seems to put the crosshairs right back where they were. I can put a star within 2 arc minutes or so of the center of the CCD just using the finder. The only bad thing is the apparent absence of a lock on the helical focuser. The weight of the illuminator turns the focuser until the illuminator is pointing down. It makes it difficult to keep the crosshairs aligned with the RA and DEC axes. I would buy again if the need arose.
I bought this scope few years back, it is an excellent finder, makes easy to read the sky and to follow the charts very accurate. For terrestrial view it is excellent with a 25 or 20 mm eyepiece, it's very short F, I believe it is 300mm to which it makes about an F3.75, makes it difficult for the use of a eyepiece shorter than 15 mm, with very bright objects tend to produce a clear astigmatism, which is not much noticeable with stars fainter that 8mag. It is great as a finder scope, and as spotting scope, as a rich acromat is short in quality image for the above mentioned astigmatism.
Can a well-engineered and executed 80mm finderscope serve multiple duties as a finder, RFT (Rich Field Telescope, and grab-and-go scope? In short, the answer is: yes, yes, and yes. Upgrading to a 80mm finder was initially based on the premise that it could be used as both a finder and RFT. At 2.5 times greater light grasp in contrast to the 50mm finder (140X that of the human eye, the larger aperture should provide a significantly more fulfilling experience when gazing rich star fields and viewing large DSOs. Upon opening the box, I was pleased with the fit and finish of the F80 finder, and the glass was pristine. At about 2.5 lbs., the F80 is heavier than the Stellarvue F50 it replaced and I hoped I would not have to counterbalance my Celestron NexStar 9.25” GPS telescope. This scope model is designed to be rear-heavy, and when the finder was mounted, no balance issues were realized and the go-to accuracy remains spot-on. I suspect the more forward positioning of the longer OTA and larger objective assembly compensates for the increased overall weight – balance-wise. In contrast to the reticle on the F50 finder, the supplied 23mm eyepiece on the F80 provides a separate reticle adjustment to bring the crosshairs into focus. The supplied eyepiece also supports Stellarvue’s optional Rigel Pulse Guide Illuminator. Should one not opt for the illuminator, there is a flexible plastic/rubber piece that ships with the finder to protect the threads and keep ambient light out of the eyepiece. This plug reminds me of the F50 objective lens cap – it’s there, but not to be trusted. A trip to Ace Hardware unearthed a rubber license plate bumper found in the “parts bins” (part # RBA-XM that fills the bill beautifully at around $1 and looks “stock.” The helical focuser affords exceptionally fine adjustment and all of my 1.25” eyepieces ranging from 5mm to 40mm of various designs come to focus. And, the ability to rotate the back end assembly (diagonal/focuser, & eyepiece is a nice feature for use during public star parties. Sometimes even a step stool isn’t high enough to allow youngsters to view large asterisms such as the Coathanger when positioned lower in the sky. Simply rotate the back assembly and the eyepiece becomes immediately more accessible. How functional is the F80? As a finder, the F80 performs beautifully. As an RTF when mounted on the telescope, it delivers views well beyond the capability of the F50. I also purchased a separate base and have it mounted on a tripod. This allows the F80 to effectively be used as a grab-and-go scope and I even temporarily mount a red dot finder on it to greatly enhance the ability to locate specific targets. For fans of Sky & Telescope’s Pocket Sky Atlas, the F80’s 3.8 degree FOV nearly matches a 4-degree Telrad overlay ring – a very handy coincidence. I also crafted a solar filter using Baader film and use the F80 as a solar finder for my solar filter protected telescope. Finding the Sun is now child’s play. How does the F80 perform? When grab-and-go mounted, from the back of the La Posada Hotel (near town center in Winslow, AZ, on Route 66 (Eagles song fame, NGC 253 and 288 resolved beautifully and fit into the same FOV. As a solar scope this past January, I viewed remnants of the believed-to-be decaying, once-giant sunspot 978 – deemed to be visually “not very impressive” on the eastern limb at the time. Cool! In early November’08, Jupiter’s Io & Ganymede moons were visually sub-minute apart, and were clearly separated as distinct pinpoints of light viewed through the finder’s supplied eyepiece. When mounted as a finder, the Veil Nebula was a most impressive sight when a 2” UHC filter was held to the eyepiece Bottom line: The F80 delivers as expected and I am very pleased with its performance. Clear skies.