25mm shootout

[Tweedledee]

I spent a bit of time last night looking at Venus and mainly Jupiter comparing the 25mm ES100 with the 25mm Fujiyama Orthoscopic. I also had a Meade 26mm Super Plossl and an old 0.965" Huyghenian 25mm.

Lack of darkness, the low altitude murk and Konus Mak 150 scope obviously helped contribute to or degrade the views and I have to say that I have seen Jupiter in a darker sky through a 10" LX200 at higher power looking superior to last night's view. Indeed, last night, a larger very slightly improved view was seen at 106x in the 17mm Ethos than on the previous night, but the image got mushy with higher power than that, so the conditions had improved a little.

Some statistics...

ES 25mm fl, 100 degree FOV, eye relief 15mm, measured field lens 44mm, measured eye lens 34mm, elements 9 in 5 groups, coatings FMC, weight 1.15 kg.

Fujiyama 25mm fl, 42 degree FOV, eye relief 22.2mm, measured field lens 18mm, measured eye lens 19mm, elements 4 in 2 groups, coatings FMC, weight 0.12 kg.

Real field of View in the Konus at 72x...
ES100 ~ 1.4 degrees
Ortho ~ 0.6 degrees

It was quickly evident that the Huyghenian was not nice to use, with a tiny, 32 degree field with reflections and spurious ghosts flitting around and no definite detail visible on Jupiter. The Super Plossl with 52 degrees, was quite nice to view through was far superior to the Huyghenian but not quite as clear as the ES and Fujiyama. Nothing wrong with the Super Plossl though for such a cheap and standard eyepiece. So on to the better eps.

Luckily for me the 2" ES and the 1.25" ortho in its 2" adapter just happened to be virtually parfocal needing less than a quarter turn on the focuser between them. This helped make the comparison easier.

At the low magnification of 72x just the two main belts were visible on Jupiter, and they didn't stand out well in either eyepiece. This reduced contrast was probably due to the low power and lack of proper darkness. The disc was perfectly sharp in both as were the tightly focused moons. Moving Jupiter to the edge of the view gave very slight dimming in the ES but not the ortho. This was probably much more to do with the effect of the narrow baffle tube of the Mak vignetting the giant eyepiece. This did not happen at all with the ortho as the baffle tube is designed to properly satisfy 1.25" eps only. With Jupiter's limb just touching the field stop of the ES there was some very slight distortion of the limb of the planet and the tiniest bit of flaring around the disc not evident in the narrow field edge of the ortho. I calculated that this effect was happening within less than the outer 1% of the massive field of view. But when are you ever going to sensibly examine Jupiter so far off axis? The field stop in the ortho was very slightly more sharply defined than in the ES, but with the ES you do have consciously look for the field stop as it is such an expansive view. Viewing position was different with each ep but easy and enjoyable in both. The ES needed the eye a little closer to the big eye lens to take in the full field, closer than you'd think reading of its reasonable 15mm eye relief. The narrow field of the ortho was all visible at varying eye positions, so a little less critical and also helped by the generous 22.2mm of eye relief.

After much swapping between the ES and Fujiyama, I had to conclude that both eyepieces gave absolutely equally excellent views of the two planets. Maybe my eyes weren't good enough to pick out any differences, but I really could not say that one or the other gave brighter, or clearer images or showed any more detail. There were fleeting moments of better seeing when a little more detail showed, but this happened equally in both eyepieces. Maybe the sky conditions and other factors were not ideal for this test. The view in either could not really be faulted, I enjoyed them both.

The ES is nearly 10x as heavy as the Fujiyama and is much bigger. The Fujiyama does actually focus your attention better on the planet with its narrow field. To the other extreme I found it nice that the ES 100s massive field framed the planet within several other surrounding field stars not encompassed by the Fujiyama. If I hadn't known differently, I could have imagined them as fainter satellites in odd wide orbits. For me I have the choice with the ES to concentrate on just the planet or enjoy with the peripheral view as a whole vista, whereas others might be distracted by the large field and consider it unecessary for planets.

So, to sum up I reckon the quality of view in the 25mm ES100 and 25mm Fujiyama Ortho is the same, and pretty much the best you are going to get. The ortho was just like only seeing the central portion of the ES view. However, there are numerous other considerations like price, size, weight, field of view and versatility for viewing different types of objects.

I'm keeping both.

Sensible offers only on the Huyghenian please.

 

 

[Doc]

Fantastic report and a really great read Pete.

 

The fujiyama range are looking better and better, I would be tempted to invest in the entire collection.

 

When I get some spare cash this is what I'm going to do. For planets, solar, and double stars you don't need a large FOV, 42° is Ok as how many times do you observe anything at the edge of your FOV, you don't it's normally always in the centre.

 

DSo's and star clusters are a different kettle of fish, you need that extra field of view, as you say there is space in your tool kit for both.

 

Btw your serial number on your ES25 does that mean yours is the 13th one made.

 

If so that's a pretty early one, maybe the earliest in the UK.

[Tweedledee]

Thanks Mick.

 

This is where I got the ortho from, they are discounted here, but you might be able to find them cheaper...

http://www.lyraoptic.co.uk/Eyepieces.html

 

Lyra had it to my door within 48 hours of ordering, and I ordered on a Sunday morning! So excellent service with personal email confirmations.

Just remember that, as with most orthos, the eye relief gets pretty dire on the smaller focal lengths. Just 3.4mm on the 4 .

 

I think my 25mm ES100 probably was the earliest to be shipped over into the UK. I've had it a year now and still haven't seen any other mention of one being used in the UK.

 

As has been said before, they are just highy unpopular, fifty dollar US eyepieces, and of course, I would have to get unlucky 13!   

Edited June 7, 2015 by Tweedledee

[+Ibbo]

How much will you pay me to take the Huyghenian  :D

Edited June 7, 2015 by Ibbo

[Tweedledee]

For nearly 300 years, this eyepiece has been used in the discovery of almost every known DSO and most other astronomical observations before the advent of astrophotography.

Sorry Steve, but with such a classic pedigree I think it only fair to start it at 99p on ebay with a buy it now of £4.50.

[Doc]

I wonder what some of the Zeiss 0.965" eyepieces are like.

 

I've heard of some astronomers using the microscope variety of Zeiss eyepieces, which you can still pick up pretty cheap.

[Tweedledee]

I've heard that too Mick, but a lot of the old microscope eps had 23mm barrels and need an adapter to 1.25". I think some old TAL scopes were actually made to use 23mm eps.

I've also read that a lot of superb 0.965" (24.5mm) eyepieces where made in the 50s and 60s that far exceeded the quality of the department store 0.965" eps. Mainly they were made by Carl Zeiss, and a few others including a company called JSO (not GSO), Pentax and Nikon. Apparently there were some 0.965" Monocentrics (cemented triplets) made that have never been bettered for quality on doubles and planets but they were only good for a 20 degree or less field of view. These little eyepieces are now quite rare but highly regarded fetching a very high price when they do turn up for sale.

Recently in the US there seems to be a trend for high definition eyepieces made from a single glass sphere. The Steve Couture design and the Siebert Planesphere are apparently the latest thing for planets and doubles if you can put up with a 20 degree field, tiny eye relief and a minute piece of glass you really need a magnifying glass to find. They are sometimes called a ball lens eyepiece. I don't think I would enjoy using one of those
 

[Doc]

I agree they sound awful.

 

Couldn't imagine using a 20° FOV eyepiece.