ScopeTech 80mm Fraunhofer Telescopes

[FLO]

Something for the traditional telescope enthusiast 🙂 

Classic Japanese-made 80mm Fraunhofer refractor telescopes. 

ScopeTech STL80A-L 80mm F12.5 Classical Refractor

ScopeTech STL-80A Maxi 80mm F15 Classical Refractor

 

 

[Craney]

Wow...look at the length of that !!

Any objects on the horizon and my SynScan will not know which end of the scope is in which time-zone !!

[Carbon Brush]

I have dabbled with one or two of the 80s 'long' scopes and the glass has been great.
With a half decent focusser (nothing about this in the product description) these should be worth a look through.

I'm guessing FLO will be revising the spec/description as it is sparse and includes the odd typo.

Next question. 80mm and F15 makes it around 4ft long + dew shield.
Will it fit in my observatory? Will I have to stand outside with the scope inside?

[John]

Very interesting scopes - good to see.

I wonder if 4" inch achromats of similar specs might be in the pipeline as well ? 

A side by side comparison between the Stellamira ED F/10 80mm and one of these slow 80mm achromats would be fascinating

I reckon it might need to be the F/15 to match the colour correction of the ED F/10 ?

[ScouseSpaceCadet]

Wow, they're long! Looking forward to a review...

Most importantly though, do they come supplied with a complimentary monocle and deer stalker?

 

[Guest]

Looks like a new super gun! 🤣

[Davey-T]

Wonder if there's a case " in the box " be tricky finding an off the shelf one to fit.

Dave

[AdeKing]

5 hours ago, Craney said:

Wow...look at the length of that !!

Any objects on the horizon and my SynScan will not know which end of the scope is in which time-zone !!

Yes, they look lovely and very tempting.

I was interested by the claim that they could be mounted on an AZ5.

Although the OTA is light, I'd have thought the moment arm of both might make mounting on an AZ5 a bit optimistic.

I'd love one but then reality bites when I consider how little use my 102 f/11 gets due to its shakiness on my EQ5 and Vixen GP mounts.

🤔☹️😢

Edited May 22, 2020 by AdeKing

[Shaun_Astro]

These look great, but a typical 80mm acromat is less than half the price. I guess Japanese quality and low production quantity put the price up. A bresser 90/1350 is £133. 

Edited May 22, 2020 by Shaun_Astro

[John]

I've found some more photos of these on another forum. They remind me very, very much of the Pentax J series refractors. Goodness how I wanted one of those way back when !

These Scopetech refractors look practically identical to the Pentax J80.

 

[Supernova74]

Looks very similar to the 100 Tal Russian scope!?

[johninderby]

I think the F15 would be the one to go for. Should make a nice not too expensive lightweight scope and has better coatings than the F12.5. 

“Note: Unlike the STL80A-Maxi, the STL80A-L has a single layer of anti reflection coating”

Main concern would be the focuser but it may be OK as it won’t be dealing with any big eyepieces. 

 

 

Edited May 22, 2020 by johninderby

[John]

Interesting that Bresser introduced two long achromats a year or two back as well. 90mm F/13.3 and 102mm F/13.2. Different end of the price / quality spectrum than these ScopeTech ones but somebody must think there is a market for them.

A few years ago I think folks thought the long achromatic refractor was no more. Clearly not !

 

[mikeDnight]

The advert sounds a bit desperate, implying some apo's are optically unstable and fall out of colimation. I've yet to see any evidence of either. Other than that, I think they look like nice scopes, but that lens cell looks like plastic?

[johninderby]

Long Post Waning.

Found this on a Japanese website and translated with an online translator hence the sometimes awkward English. It’s from a few years ago but may be of interest.

 

***********************************************

Refractive telescope STL80A-MAXI (with attachment plate, lens barrel band and 6x30 finder)

Product concept

I would like to introduce the way to the revival of this 8cm F15 long focus achromatic lens barrel.

The long-focus achromatic refractor that has recently disappeared. The motivation for reviving it was to get the Mizar "Kaiser" I found at a certain recycling shop.

The 8 cm refracting telescope was manufactured 37 years ago. It was a huge telescope designed with a long focal length of F15 1200 mm in order to bring out the performance of the achromatic lens. At the time of sale, it was a high-end model with a caliber of 8 cm, but the lens had already grown moldy and needed to be repaired.

As a result, when the miraculously revived "Kaiser" is pointed at the starry sky, the view is clearer than I imagined! It was shocking to me that I thought the short focus apochromat lens barrel was the best. (Of course, the apochromat is extremely excellent in terms of chromatic aberration, and the apochromat with a certain focal length looks good with little spherical aberration that impairs resolution.)

Recently, foreign-made apochromat lens barrels with an aperture ratio of less than 7 are gaining popularity, but the assembly and adjustment are not easy and the performance varies greatly. In addition, with two-lens apochromat, many aberrations cannot be removed, and chromatic aberration and spherical aberration are very noticeable. Compared to such apochromat, surprisingly, Kaiser equipped with 8 cm achromat looks much better.

Refractive telescopes have the same type of objective lens (for example, between achromats), but the longer the focal length, the more drastically the chromatic aberration decreases and the spherical aberration also decreases. However, it is said that the F15 and focal length 1200 mm achromat lens barrel had such ability.

Achromat is far cheaper to produce than apochromat, which uses special glass, and the quality of the glass material is stable. Isn't it interesting to make this now? However, the 8 cm F15 focal length 1200 mm achromat lens has not been made for nearly 30 years. The 8 cm achromat lens that is currently made has a focal length of 900 mm for entry-level machines. With the rise of Chinese products, even the lens factories in Japan are no longer polished.

For reproduction, the problem was whether there was a polishing plate left to polish the objective lens with an aperture of 80 mm and a focal length of 1200 mm. If you don't have a polishing dish, you have to make one, which is not worth the cost unless you order tens of thousands. But in the small Japanese market, I don't think this kind of telescope, in a sense, will sell so much. In other words, the absence of a polishing dish means that the 8 cm F15 lens barrel cannot be reproduced in the future.

However, I couldn't find the polishing dish. Around the fall of last year, when I almost forgot about this project, I learned about the existence of a factory that preserved 1200 mm polishing plates as a posterity. It is a factory of a company that is quite famous for polishing lenses. Let's leave the miraculous process of coincidence to another opportunity. Anyway, in this 21st century, there was a way to revive the 8cm F15 long focus achromat.

This time, 100 lenses have been polished. Since 50 of them were coated, the first production is 50. Perhaps this 100 will be the first and last polish of this century. It is clear that even if you polish the next 100 pieces, it will lose momentum compared to the first sale. No one can hold inventory for a long time.

After repeated prototypes and specification changes, the schedule was greatly delayed, but 80AL-MAXI finally appeared. We have thoroughly invested in the parts that affect the appearance. Particular attention has been paid to the parts that cause a decrease in contrast, such as delustering the inner surface and coating the edges of the lens. The conventional astronomical telescope has a level of multi-coat HTM coating, which is very unlikely to be seen in conventional astronomical telescopes, and boasts unparalleled high transmittance.

However, for parts that do not affect the appearance, a popular draw tube is used, and an objective lens cell that does not have an optical axis correction device is used. I did my best to achieve the level of appearance.

I also learned this time through the production of this telescope. The lens that has been properly polished, centered, and assembled looks much sharper and better than the large tree of Udo, which has only a large caliber recently.

On a day with good scintillation, we conducted a star image test using real vision. The “star image that looks like a needle” that can only be achieved with a domestic product, the achromat, shows the high level of K-optics' technical capabilities that refined this lens.

We also had the opportunity to observe Saturn with our customers on a prototype machine on good scintillation days as well. At that time, it was proved to be an extremely excellent optical system with 240 times, which is equivalent to 3 times the aperture diameter, and with less image collapse compared to other high-end lens barrels equipped with apochromatic lenses.

The STL80A-MAXI is said to have unrivaled high performance at a price below 40,000 yen. Some people may think that 8 cm is a small diameter and stupid, but once you look into it, you will find that it is a high performance telescope that you can not overlook

 

 

Edited May 22, 2020 by johninderby

[Chris]

All I can say is the sight of these makes me happy. I love a good long focus refractor, and these look like they've had a lot of care and attention put into them. Maybe not as practical as a shorter Apo, but if you can mount them properly, the views and the experience of using a decent long focus refractor is something really special. Nice one FLO!

[Froeng]

Amazing,

Vixen used to make an 80/1200 in the 80s - it was their “planet-killer”.

Can’t wait for the first reviews...

CS Frank

[paulastro]

I think these look really cool, and they remind me of my youth.  The experience and image you get looking through one of these is quite something, like stepping back in time.  It would also be good to compare the f15 with my SW  80ED, though the experience would be akin to comparing a Questar with a Meade ETX90 !.  I can just get away with having my SW 80ED set up on the AZ5 in the lounge, but I fear my wife might notice if I swapped the 80ED with one of these beauties 😄.  I dont want one, I dont want one, I dont/do want one, I do want one,  aaarrrggghhh!

Edited May 23, 2020 by paulastro

[Merlin66]

I just bought a SW Black Diamond 102/ 1000 achromat for a PST mod.

weighs in at only 3.3Kg, looks good, feels good and only A$300 delivered.

 

[Shaun_Astro]

Wonder how it would compare to an evostar 120 with an apo filter.

[Peter Drew]

1 hour ago, Froeng said:

Amazing,

Vixen used to make an 80/1200 in the 80s - it was their “planet-killer”.

Can’t wait for the first reviews...

CS Frank

Vixen also did a 102/1500 at that time.  It wasn't popular due to the mounting requirements, the 102/1000 sold the best.  I have a 5" F15 triplet and had to make my own mount for it due to the size!.       🙂

[Dave1]

Yes I'd like to buy this telescope, but not at the moment. Bank account needs to recover. I really like the Scopetech 80mm F15. The Foucault test, strehl ratios for different wave lengths, and spot diagrams are very good to excellent.

Agreed a 4" F15 needs a serious mount, and any bigger must definately have a big mount. 

I might have a John Owen 6" F12 doublet coming my way. Thankfully I have the mount for it !

David

[John]

Yes, 6 inch F/12 refractors need very heavy duty mounts !

I reckon the 80mm F/15 is going to need at least an HEQ5 / Skytee II to control that moment arm force.

 

 

[Rusted]

I'd try one of those long, thin things on a Berry-style, offset, counterbalanced, Dobby bearing, fork mount for small change in plywood.

It's surprising how the moment [mass x distance from the axis] soon catches up with "inadequatorial" mountings.
The moment of the objective & cell is effectively doubled because it has to be balanced [somewhere in the middle] by the focuser and finder at the other end.

I have 90/11, 150/8, 125/15, 150/10 & 180/12 achromats. The difference between mounting the first and last equatorially is mind blowing!
On Berry style altazimuths? Eazy-peasy! Provided you still have the strength to lift the OTA into the forks.  👴🏻

[johninderby]

I’ve been testing the TS Alt-Az counterbalance system and it’s surprising how much it improves the stability of a small mount with a longer scope on it as well as allowing you to mount a heavier scope. 

 

Edited May 23, 2020 by johninderby