Often in our reviews and buyer’s guides, as well as scattered in literature throughout the internet on Reddit, Instagram, and Cloudy Nights, recommendations abound for the “gold-line” eyepieces or their numerous rebrands, as well as the newer “red-line” eyepieces. However, very little is devoted to actually reviewing these eyepieces in a quantitative manner.
Who Makes the Goldlines?
Contrary to what many seem to believe, there seems to be no actual difference between the gold-line and red-line eyepieces apart from the rubber grips on the red-line barrels, so rest assured that you are not sacrificing anything by buying a cheaper gold-line.
The “gold-line” eyepieces are unique among non-Plossl eyepieces in that they are sold by a number of different vendors with absolutely no design changes apart from a different colored bezel.
The following companies sell gold-lines and their rebrands:
- SVBONY: Gold and red bezeled versions.
- Agena Astro: Gold version, called “Starguider” occasionally in literature but branded “Enhanced WA”
- Orion: Blue bezel branded “Expanse”
- Knight Owl: Teal bezel branded “Enhanced Super Wide”
- Meoptex: White bezel
- Yoosoo: Gold bezel
- Antares: Repackaged into “W70” and marked up severely in price. Not recommended.
We chiefly recommend SVBONY, mostly because they are usually sold at the lowest price and ship pretty fast.
Which Goldline To Buy/Building a Set
While all are marketed as having a 66-degree or sometimes 68-degree apparent field, the goldlines actually widely vary depending on focal length. As tested and verified, the eyepieces have the following focal lengths and actual apparent fields of view:
- 6mm – 63.5 degrees
- 9mm – 70.5 degrees
- 15mm – 66 degrees
- 20mm – 68 degrees
You might be wondering: what goldline focal lengths should you buy?
If budget is not a huge concern, we’d recommend the whole set. Sure, you might not use all of them very often, the 15mm might not be of much use with some scopes, and the 9mm might invalidate your scope’s stock 9mm/10mm Plossl, but they’re still of great value, and it’s great to experiment with different eyepieces – especially since they are at such a low price. Also, with most offerings for the whole set, you are paying about as much as three of the eyepieces would cost individually, so the fourth is basically free.
If you can only get one: Buy the 9mm if your scope lacks something in that focal length range already, otherwise get the 6mm.
Specifications & Performance of Different Focal Length Goldlines
Remember, to calculate the magnification, you simply divide the focal length of your telescope by the focal length of your eyepiece—e.g., the 20mm eyepiece would provide 60x in a 1200mm focal length telescope. For exit pupil and true field calculations, we recommend this site here, or many programs like Stellarium, SkySafari, and SkyTools can do it for you and provide a visual simulation of what the field of view will look like.
The goldline eyepieces are all derivatives of the König 3-lens design, but the 6mm and 9mm use a built-in doublet Barlow lens to shorten their focal lengths and increase the eye relief, or the distance from which you can look into the eyepiece before the image blacks out (important for those who must wear eyeglasses for astigmatism). The lens edges on the interior are blackened, and the lenses are claimed to be fully multi-coated (which seems to be at least somewhat true).
The performance of the goldlines widely varies with focal length. This is in part because of the built-in Barlow of the 6mm and 9mm units, but also because the overall optical design seems to slightly vary with the eyepieces (part of why the field of view is actually inconsistent).
That being said, let’s go over the performance of each eyepiece.
The 20mm goldline is the longest focal length eyepiece of the four, and provides the lowest power and widest field of view. Being a König, it suffers from edge-of-field astigmatism with scopes with focal ratios below about f/6; stars appear as ovals, commas, or seagull shapes at the edge of the field of view. This may be masked by the coma present in f/5 and below scopes, which can manifest itself in a similar fashion. However, overall the performance in a fast scope is comparable to a cheap Plossl and, thus, I’d deem it acceptable (though not great) for a fast Newtonian. For a longer focal ratio Newtonian, refractor, or catadioptric scope, it is a stunning performer all the way out to the field edge. Due to its wider apparent field, the 20mm goldline is more or less able to supplant the standard 25mm Plossl or Kellner included with many scopes, though it will produce a higher magnification with a given telescope.
As previously mentioned, the 15mm is the worst performer of the goldlines. It has quite a fair bit more astigmatism than the 20mm model and seems to have some internal reflection issues. The center of the field of view doesn’t seem to be particularly sharp either. Performance seems to be decent in Maksutov-Cassegrains and Schmidt-Cassegrains but with any refractor or Newtonian faster than f/8 to f/10, I would hesitate to really recommend the 15mm. It just isn’t that crisp.
The 9mm goldline is easily the best eyepiece in the set. Its field of view is the widest at 70.5 degrees and remains consistently sharp regardless of your telescope’s focal ratio. I have used it in scopes as fast as f/3.5 with pinpoint images throughout most of the field. This is partly thanks to the Smyth/Barlow lens in the eyepiece. Unfortunately, while the 9mm goldline is our #1 pick, it is probably the least useful since many scopes come with a 9mm or 10mm Plossl or Kellner that will probably suffice for a while.
The 6mm is the most oft-cited eyepiece in the line. After admittedly recommending them for years without having actually used the 6mm model, I finally got my hands on one earlier this year and was a bit surprised by the performance. It is very sharp but does suffer from some ghosting/reflection effects that can be particularly annoying on planets and double stars. There is also some “kidney beaning”—eye positioning is relatively sensitive despite the large eye lens, which can take some getting used to. Overall, however, the performance is very good even at fast focal ratios, provided you can ignore the reflections. If you don’t like the reflections, there really aren’t many other budget options at its focal length beside a Plossl which will be super uncomfortable to use, or spending over $100 for something like a Meade UWA. For the price, I think the eyepiece is still a good pick.
Overall, I would highly recommend the goldline eyepieces. While they’re not perfect, the value for the price is quite simply outstanding and they are an order of magnitude better than a Plossl or Kellner.