Review of the TeleVue Delos 12mm Eyepiece
TeleVue Delos 12mm: Imaged taken from http://alpha-lyrae.co.uk/2014/05/04/televue-delos-eyepiece-review/ where you can find another beautiful review of the eyepiece.
A certain originality in choosing the names of their products must be given to TeleVue.
If we exclude the Plossl, we think of the Genesis or Pronto refractors, or the Nagler or Radian eyepieces (whose apparent field of view is roughly a radiant), or the Ethos.
Even though the other brands use aseptic acronyms, TeleVue has chosen another path.
We come to the object of our review: the TeleVue Delos (perhaps from the name of the island of Delos, birthplace of Apollo, god of the Sun?) with the focal length of 12mm.
Based on the official website, TeleVue carry over the features:
Apparent field (AFOV): 72 degrees
Eye Relief: 20mm
Weight: about 410gr
Field Stop: 15mm
Parfocal with all TeleVue eyepieces with 31.8mm barrel
Price: £309 (in July 2018)
The packaging is good, but for the purchase price you would expect a bit more. No other accessories, except for the caps, are present.
Apart from this, however, the eyepiece is well kept, of good quality.
The size and weight are obvious (without being at the levels of an Ethos) and the comparison with a regular Plossl of 13mm highlights its different dimensions.
The lens scheme includes a negative optical assembly placed in the lower barrel.
The hood has the classic continuous sliding system of TeleVue, with the external barrel that slides over the central one and is locked / unlocked by 2 ring nuts.
After understanding how it works, it becomes really useful and allows a personalized adjustment based on the needs of the observer.
In addition to this there is a small resealable rubber hood.
A short negative note though: the cap is very loose and you may lose it.
The anti-reflective treatment is excellent however.
Practical test. To test this eyepiece, a C8 XLT (170x) and a C11 XLT (233x) were used, with 2″ diagonals of the TS and a Barlow Baader Q-Barlow 2.25 lens.
The focal length of 12mm is not a focal length for large stellar fields or diffuse nebulae (even in short focal instruments), but lends itself more to the observation of the stars of the solar system or objects not particularly extensive (globular clusters, planetary nebulae) , galaxies or double stars.
An operation that I think is necessary right from the start is the adjustment of the hood: the parallax effect is present but if the hood is well adjusted the eye is guided and allows you to comfortably enjoy the whole field. The field diaphragm is very clear. As soon as the eye is resting the vision is satisfying: you can comfortably embrace the whole field, the sharpness and the contrast are at the highest levels, up to the edges of the field. The field is leveled.
In this test, the 12mm Delos was compared to 2 economic eyepieces (a 70 degree field SWA and a common Plossl), to see if the much higher cost is, actually, reported to the actual performance.
Excellent: no diffused light, clear and contrasted to the edges, feeling of ‘immersion’ in the lunar landscape.
For comparison, the Plossl is still clear but has some light diffused and a dominant brownish. The SWA is clear in the center but not at the edges.
If seeing allows it, Delos enables us to see better than the Plossl (which has more diffuse light), the sky background is darker and the details of the planet more accessible. Even the colors are more saturated.
In the deep sky a characteristic of this eyepiece emerges: the excellent transmission of light, it seems to see more of the other oculars, the vision is crystalline.
The darker background, the high contrast, allow you to better disconnect the subtle details of the nebulae or galaxies.
With the globular we touch the sky, they are perfectly framed and defined.
For comparison, with the SWA the image is slightly more kneaded and the contrast is lower.
Use it with a Barlow
I tried the Delos with a Baader Q-Barlow 2.25 (which would be in reality the ideal companion of the BCOs).
Apart from the fact that the barrel of Delos does not get to the point, for the rest the optical performance is excellent.
To summarize, this is an excellent eyepiece, with great performance and obviously recommended if price is not a problem.