My Rambling Thoughts

It's really cloudy tonight

My first post on Cloudy Nights, with some grammatic correction:

I just started planetary observations with my 127SLT and this thread resonates pretty strongly with me. :-)

I read up quite a bit on magnification and eyepieces before I upgraded my stock eyepieces, and I also wanted to buy just once, so I went for the highest tier that I was willing to spend on: Explore Scientific 82 degrees.

When I popped in the ES 8.8mm EP to view Jupiter, my first reaction was, "wow, my stock 9mm Kellner eyepiece is pretty good!" :lol:

And after viewing for a short while, I had to chuckle. After telling myself I would settle for nothing less than 82 degrees FOV (since ES is good and affordable, why not?), I found that I didn't really like it that much, mainly due to the short eye relief. So I backed off and saw maybe 60 – 70 degrees only. And that's fine for planetary observation. It was then that I realized the stock 9mm EP could show Jupiter with its 4 moons at the same time with its mere 45 degree FOV. It's tight, but good enough for me.

The third surprise was magnification. After 170x (8.8mm), I tried 223x (6.7mm), then 272x (5.5mm [11mm / 2]), then 341x (8.8mm / 2), then finally 448x (6.7mm / 2), using the ES 2x Focal Extender. The last two were somewhat dim (0.37mm and 0.28mm exit pupil), blurry and extremely difficult to focus, but I was surprised floaters weren't that bad and seeing was so good. It's due to my latitude (1.3521° N) — Jupiter is near zenith — and being surrounded by sea. I believe 223x already shows as much detail as my scope can give, but this makes me want to try a bigger scope that can support 400x magnification.

Where do I go from here for planetary observations? One, Ortho. :-D Two, binoviewer! :lol:

It took almost a week for my account to be approved, as the administrator thought I was a spambot. :duh: My second post:

I see that you are at 25.4052° N, beside the sea and desert? That would account for good seeing. But 900x? That sounds out of this world. :-D

Jupiter shimmers sometimes at 448x (didn't see it at 341x), so that is about the max at my location, regardless of the size of the scope.

As sg6 mentioned, it is good to use your existing equipment — to figure out what you like and what you don't — and determine the next course of action.

I had not intended to get an Abbe Ortho eyepiece, but I felt there was still something left on the table, so will give it a try. Also, since I found seeing was so good, I decided to opt for something highish, i.e. 7mm F.L. (214x) .

This guy just wants to use as high magnification as possible. All newbies do that. :lol:

Abbe Ortho eyepieces

KSON (开信) Ortho

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OEM for University Optics (UO) Super Abbe series.

This is budget-class Ortho and by all accounts, its build, coating and image quality are a notch below other Orthos.

Fujiyama HD OR

フジヤマ. By Kokusai Kohki. The original line was discontinued for a while around 2012 – 2013 (earthquake in Japan, shortage of raw material, death of sole lens maker), then resurrected as Fujiyama.

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OEM for UO HD series and Baader Genuine Ortho (BGO) series.

This is the minimum acceptable standard for Ortho. Cheaper ones are not good enough that there is no point getting them. More expensive ones are very slightly better, but they cost at least double the price. :sweat:

They are made in Japan. The list price is 9,800 yen (US$91.40), but a Japanese price chart show they are discounted by 20% (7,800 yen) — introductory price? I only found one TaoBao seller with stock (price as above)...

Takahashi MC Abbe


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Suspected to come from the same assembly line as Fujiyama Ortho eyepieces, but built to higher spec.

Teasing out details

An online poster ranks exceptional planetary eyepieces in tiers:

  1. Singlet, Supermono, Pentax XO, ZAO (Zeiss Abbe Ortho)
  2. AP-SPL, CZJ (Carl Zeiss Jena), Pentax SMC Ortho
  3. Brandon
  4. UO HD, BGO, Meade RG (Research Grade)

UO HD is lowest on the totem pole... :sweat:

Phasing out old bikes, carrot and stick

News: Owners of older motorcycles to get up to $3,500 to deregister vehicles

Date: 6 Apr 2018. Source: ST.

To improve air quality, the National Environment Agency (NEA) is offering an incentive of up to $3,500 for owners of older and more pollutive motorcycles to deregister their vehicles over the next five years.

In a media release on Friday (April 6), NEA said all owners of motorcycles registered before July 1, 2003, are eligible for the incentive if their vehicles have a valid 10-year certificate of entitlement (COE) as of April 6 this year, and are deregistered on or before April 5, 2023.

About 27,000 motorcycles are eligible, said the agency.

27,000 out of 141,304 bikes (end 2017) are before 2003 (more than 15 years).

Carrot: $3.5k to deregister bike.

Stick: in July 2028, bikes registered before July 2003 will not be allowed on the road, period, unless they are on 5-year non-renewable COE, classic or vintage vehicle scheme. This is pretty draconian.

NEA waxes on pollution, but if they make any real observation, they will find that there are very few old bikes on the road — they are not used as daily transport. LTA just wants the old bikes gone, their COEs recycled for new bikes.

This is very typical of Singapore. Land is scarce, so old buildings have to make way for new. There is no room for nostalgia.

Simple eyepieces

I'm quite surprised with my Kellner 9mm eyepiece that I wonder, are there any good Kellner eyepieces out there?

Well, there used to be, but there are none now. (You can still hunt them down on the used market.)

The reason is that it is completely outclassed by modern Plössl (普罗索) design in every way: same four air-to-glass surfaces but poorer optical quality (due to three glasses vs four), lesser eye relief (0.5x F.L. vs 0.7x), narrower FOV (45° vs 50°) and does not work well with fast scopes (up to f/7 vs f/5).

(Note that modern "Plössl" design just means 4/2 symmetrical design.)

Kellner design also suffers from ghosting for bright objects, such as planets. I do not know if this is due to poorer coatings or inherent lens design.

Today, Kellner (凯涅尔 or 凯尔纳?) eyepieces are relegated to bundled-eyepieces with telescopes. They are cheap to make and they have decent on-axis quality in slow scopes.

Case closed. :lol:

Abbe Ortho

When people say Ortho with the capital 'O', it is taken for granted they mean Abbe Ortho (阿贝无畸变). An orthoscopic eyepiece (无畸变目镜) is simply one that gives good definition and has little geometric distortion.

An Ortho eyepiece has a cemented triplet and a singlet, so it has only four glass-to-air surfaces even though it has four elements. It has very narrow FOV of ~40°, but it has found a niche as planetary eyepiece due to its superb on-axis performance.

Its advantages over Plössl are, its higher contrast as a result of little light scattering due to its lens layout, and better eye relief (0.8x F.L.). This allows shorter Ortho eyepieces down to 4mm.

It is recommended to use on scopes f/7 and slower only.

In the past, before wide-angle eyepieces, Orthos were no big deal. Today (since early-2000s?), there is a renaissance of sorts. People started to look for specialized designs that can beat modern-day ultra-wide angle designs for specific applications.

Abbe Ortho is one of them. Today, its reputation is not just from its lens design, but also its execution: glass purity, polish and coating. Abbe Ortho does not automatically win over Plössl.


There is one lens design that is even better than Ortho for planetary observation: the "Monocentric". I quote it because the leading example, the TMB Super Monocentric (SMC), is of another design (modified Zeiss monocentric, in turn based on Steinheil monocentric). Nevertheless, it is a cemented 3-element design, so it has only two glass-to-air surfaces.

Pros: high contrast.

Cons: 30° FOV, sharp only on-axis, field curvature, short eye relief.

For hardcore planetary, double star and DSO observers only. Long discontinued (they weren't very popular), the used price is higher than new price.

Eyepiece @ 25mm

I claimed that there is a gap between 52° and 68° for 24-ish mm eyepiece. It turns out there is not. Meade (美德) fills in this gap nicely with its HD-60 25mm 60° eyepiece. It weighs 217.7g.

The whole Meade 5000 HD-60 series: 4.5mm, 6.5mm, 9mm, 12mm, 18mm, 25mm. They are all 60° FOV, with 17mm eye relief, supposedly all with 6 lens elements. Meade describes them as Plossl optical design, but they are more likely to be Erfle.

It is noted by online forumers that the shorter F.L. ones are likely to have more lens elements as they incoporate a Symth/Barlow-like element to achieve long eye relief. (This is the only known technique.)

According to online posts, the 6.5mm, 9mm and 25mm EP are excellent. The 4.5mm and 12mm EP are okay (not perfect across entire field). The 18mm EP is the worst.

The 25mm EP costs US$75 at OPT. It is not on sale on TaoBao.

The Celestron (星特朗) X-Cel LX series is a slightly cheaper rebrand: 2.3mm, 5mm, 7mm, 9mm, 12mm, 18mm, 25mm. They have a claimed eye relief of 16mm. Some F.L. are rounded up, but that is not unusual.

(Update: an online poster took apart the X-Cel LX 9mm EP and it is 1-2-1 König design with a 2-element symth lens. The 12mm EP and below should be the same. 18mm and 25mm EP may not have the symth lens or may have a different design altogether.)

The 25mm EP weighs 207.0g and costs US$66 at B&H Photo.

The X-Cel LX eyepieces are sold on TaoBao, but are slightly more expensive, being imports!

Since Celestron is owned by Synta, the eyepieces are probably made by them as well. They are probably cheaper in Taiwan.

If I had learnt about this series earlier, and knowing what I know now, I would have gone for the 6.5mm, 9mm and 25mm EPs as my first upgrade set — if they were cheaper by 25%. They are a perfect match with my 127SLT. The irony is, if I had gotten them first, I would be wondering how much better the ES eyepieces would be. :lol:

As it is now, I'm only interested in the 25mm 60° eyepiece for its light weight. I'm still somewhat interested in the 6.5mm and 9mm EP (I'll pass on the sub-optimal ones), but I have other eyepieces covering these focal lengths. I'll keep them in mind if I see them on sale. :lol: