Succumbed to classic f15 urge…

[SuburbanMak]

I fed the eBay beast again today picking up a Topic (Towa I believe) 80mm f15 OTA. 

I’ve been looking for a classic Japanese 3in for a while and fingers crossed although there’s a few scuffs on the paintwork this one looks to have clean optics and a smooth focuser. 

The sale includes no mount but rings and dovetail, so should be good to go on my existing mount & tripod. 

I have a Vixen threaded  adapter that I think will fit the drawtube to accept 1.25” diagonal but looking at this setup suspect I may need additional extension to reach focus.

Any detail on Topic-branded scopes generally welcome and specifically conversion of this model to 1.25” inch use. would be amazing , I know there’s a few of these ‘scopes out there in SGL land  

Edited November 4, 2021 by SuburbanMak

[Ian McCallum]

The Cloudy Night's forum has got a lot on these, I was looking it up the other day.👍

[F15Rules]

Congratulations on your new purchase, a classic long achromatic refractor👍.

There is plenty of info here on SGL if you just search in this forum for "Topic 80mm F15" or "Towa" or "Kenko" 80mm F15..

Here's an excerpt from a recent thread in which a member asked about the focuser and drawtube on these scopes, it should help you understand how best to convert the scope for 1.25" eyepieces..there are also some links to other threads which walk you through the process.

(A Vixen adapter is readily available online, it's this one and just replaces the original one which was designed for 0.965" eyepieces)..

"scopes by Towa, Kenko, (some branded for retailers eg Prinz 660, Topic etc), this was known to happen when upgrading a scope originally intended for use with 0.965" eyepieces: these scopes have very long drawtubes, and in the case, for example, of the Topic 80mm F15 1200mm focal length scope, the long drawtubes contained at least one, sometimes two, inner baffles. 

An adapter became available which threaded into end of the chromed drawtubes (the original screw in adapter with 0.965" fitting being removed first), and this adapter allowed the insertion of a 1.25" diagonal or eyepiece instead.

It was noted, however, that the view using some 1.25" eyepieces was rather dim, and investigations showed that the inner baffle(s), which was optimised for 0.965" eyepieces, was actually narrowing the drawtubes' internal diameter, and thus starving the 1.25" of precious light.

Fortunately, the baffles could easily be removed with a sharp tap from a screwdriver and hammer, and this enabled the 1.25" to work properly, often transforming the performance of the old refractor, widening the fov, and allowing often good quality lenses to deliver of their best.

I did this myself on more than one occasion .

These threads might be of interest if you have nothing else to do..

https://www.cloudynights.com/topic/573766-towa-drawtube-modifications/

https://www.cloudynights.com/topic/482086-towa-965-focuser-extension-tube-modification/

(Scope image credit Cloudy Nights).

Dave"

Hope this helps you.

Just a quick note on mounting this scope..yours is shown on a vintage Unitron/Polarex altazimuth mount.. it's a great little mount but isn't suitable for such a long scope.

I realise you've bought the scope only, so hopefully you have the equivalent of a Vixen GP or Skywatcher EQ5, which would be much more suitable and stable (especially the Vixen!😁).

Good luck and do share your impressions once you've made the modification to 1.25"..😊

Dave

 

Edited November 4, 2021 by F15Rules
Additional text info

[SuburbanMak]

59 minutes ago, F15Rules said:

Congratulations on your new purchase, a classic long achromatic refractor👍.

There is plenty of info here on SGL if you just search in this forum for "Topic 80mm F15" or "Towa" or "Kenko" 80mm F15..

Here's an excerpt from a recent thread in which a member asked about the focuser and drawtube on these scopes, it should help you understand how best to convert the scope for 1.25" eyepieces..there are also some links to other threads which walk you through the process.

(A Vixen adapter is readily available online, it's this one and just replaces the original one which was designed for 0.965" eyepieces)..

"scopes by Towa, Kenko, (some branded for retailers eg Prinz 660, Topic etc), this was known to happen when upgrading a scope originally intended for use with 0.965" eyepieces: these scopes have very long drawtubes, and in the case, for example, of the Topic 80mm F15 1200mm focal length scope, the long drawtubes contained at least one, sometimes two, inner baffles. 

An adapter became available which threaded into end of the chromed drawtubes (the original screw in adapter with 0.965" fitting being removed first), and this adapter allowed the insertion of a 1.25" diagonal or eyepiece instead.

It was noted, however, that the view using some 1.25" eyepieces was rather dim, and investigations showed that the inner baffle(s), which was optimised for 0.965" eyepieces, was actually narrowing the drawtubes' internal diameter, and thus starving the 1.25" of precious light.

Fortunately, the baffles could easily be removed with a sharp tap from a screwdriver and hammer, and this enabled the 1.25" to work properly, often transforming the performance of the old refractor, widening the fov, and allowing often good quality lenses to deliver of their best.

I did this myself on more than one occasion .

These threads might be of interest if you have nothing else to do..

https://www.cloudynights.com/topic/573766-towa-drawtube-modifications/

https://www.cloudynights.com/topic/482086-towa-965-focuser-extension-tube-modification/

(Scope image credit Cloudy Nights).

Dave"

Hope this helps you.

Just a quick note on mounting this scope..yours is shown on a vintage Unitron/Polarex altazimuth mount.. it's a great little mount but isn't suitable for such a long scope.

I realise you've bought the scope only, so hopefully you have the equivalent of a Vixen GP or Skywatcher EQ5, which would be much more suitable and stable (especially the Vixen!😁).

Good luck and do share your impressions once you've made the modification to 1.25"..😊

Dave

 

 

Thanks Dave - this is helpful indeed!   I have a Vixen adapter doing a similar job on my Hilkin 60mm f13, so you're saying the thread sizes on the Towa are the same and I just unscrew the existing adapter and replace?  If so that would be amazing.

As for knocking out baffles with a screwdriver this will be a new threshold of brutality in scope modification for me who has so far been limited to some light flocking...definitely sounds worth the risk however!  

On mounting, I've been running an old Clarkson brass 3inch f15 successfully on my AZGTi (uprated with the ADM clamp) and Berlebach 312 Report - its quite solid and tracks without vibration provided its not too windy!   I am working on the basis that the Topic will be the same length and a bit lighter as its aluminium not brass.   

In all cases, its part of the fun finding out - I'll post on progress when it arrives and thanks again for the sagely advice!  

(This will be my fourth classic refractor & I suspect not my last, for example there's a 60mm Unitron and a couple of Zeiss Telementors on eBay right now. There's something special about the pin-sharp stars on inky backgrounds and also the nostalgia factor, as a boy with a (borderline unusable) Tasco 4-VTE these were the 'scopes I aspired to!  I might have to change my username to SuburbanFrac...) 

Mark 

 

 

 

 

[F15Rules]

1 hour ago, SuburbanMak said:

I have a Vixen adapter doing a similar job on my Hilkin 60mm f13, so you're saying the thread sizes on the Towa are the same and I just unscrew the existing adapter and replace?  If so that would be amazing

Yes Mark, it should work fine, these old Japanese scopes seem to all have the same thread.. it'll only take a minute to unscrew the Topic one and try the Hilkin one👍..

 

1 hour ago, SuburbanMak said:

As for knocking out baffles with a screwdriver this will be a new threshold of brutality in scope modification for me who has so far been limited to some light flocking...definitely sounds worth the risk however!  

It sounds more brutal than it is..but the baffles are thin, light material so it would be very difficult to cause any damage to the main extension tube..just use a fairly wide bladed flat headed screwdriver (obviously, narrower than the internal width of the extension tube. Just tap it persistently with gently increasing force and it will pop out (if I recall correctly there could well be 2 baffles to remove, so check each tube that lies behind the focuser, as you need to remove all the extension tube baffles to get the full benefit of the wider field.

 

1 hour ago, SuburbanMak said:

On mounting, I've been running an old Clarkson brass 3inch f15 successfully on my AZGTi (uprated with the ADM clamp) and Berlebach 312 Report - its quite solid and tracks without vibration provided its not too windy!

Sounds ideal, just make sure to get the balance set perfectly, it's worth the extra effort and the scope can take high magnification on doubles (200-300x on a steady night!), so you want the most stable setup you can achieve.

Enjoy!

Dave

[F15Rules]

1 hour ago, SuburbanMak said:

there's a 60mm Unitron and a couple of Zeiss Telementors on eBay right now.

Unitron 60mm...hmm🤔. They vary a lot, some good some not so good. But the little altaz mount they come with sometimes (same as your Topic was shown mounted on) are excellent, well engineered and very smooth.

The Telementors are superb, consistently so. A full Telementor scope and original mount with two original eyepieces in good condition is likely to cost between £400-£700..but search here on SGL for Telementor and you'll see why people like them so much.

Dave

[Ian McCallum]

The more I read up on these long focal length Japanese achromats, the more I want one! 😮

[johninderby]

14 minutes ago, Ian McCallum said:

The more I read up on these long focal length Japanese achromats, the more I want one! 😮

Why would you want one of these long thingys? 😁😁😁

there is a reason long focal length achros like the ScopeTech and Starbase are in production again albeit with the latest optical,coatings so perform better than ever. 👍🏻

[Ian McCallum]

9 minutes ago, johninderby said:

Why would you want one of these long thingys? 😁😁😁

there is a reason long focal length achros like the ScopeTech and Starbase are in production again albeit with the latest optical,coatings so perform better than ever. 👍🏻

I just bought a used achromat from a fellow SGL'er, to dip my toe in the refractor water.  If I like it, then perhaps I'll look more into the Japanese drain pipes of starlight!🤣 

[Chris]

Congratulations! I've said this a million times and I'll say it again - there is something special about classic long focus refractors.... and the ladies find them irresistible too!

 

 

 

Edited November 4, 2021 by Chris

[AdeKing]

I picked one of these up Last August for relatively little money from a fellow SGL member and was very impressed with the views it gave me during the Mars opposition last October.

Mine came in a big wooden box complete with mount, but I tend to use mine on my Vixen GP or GPD2.

Lovely sharp views with very little CA and just about reaches focus natively with my Maxbrite binoviewers.

Mine has had a nice brass fitting machined to allow 1.25" eyepieces to be used and gas had the relevant baffles removed so no vandalism was needed on my part.

I had been tempted to get an adaptor machined so I could fit a modern focuser, but I kind of like the fact that everything is original so never bothered in the end.

I hope that you get as much enjoyment from yours as I have from mine.

Ade

[SuburbanMak]

1 hour ago, F15Rules said:

Yes Mark, it should work fine, these old Japanese scopes seem to all have the same thread.. it'll only take a minute to unscrew the Topic one and try the Hilkin one👍..

 

It sounds more brutal than it is..but the baffles are thin, light material so it would be very difficult to cause any damage to the main extension tube..just use a fairly wide bladed flat headed screwdriver (obviously, narrower than the internal width of the extension tube. Just tap it persistently with gently increasing force and it will pop out (if I recall correctly there could well be 2 baffles to remove, so check each tube that lies behind the focuser, as you need to remove all the extension tube baffles to get the full benefit of the wider field.

 

Sounds ideal, just make sure to get the balance set perfectly, it's worth the extra effort and the scope can take high magnification on doubles (200-300x on a steady night!), so you want the most stable setup you can achieve.

Enjoy!

Dave

Thanks so much - am even more excited to receive it now!

[Stu]

4 hours ago, F15Rules said:

Unitron 60mm...hmm🤔. They vary a lot, some good some not so good. But the little altaz mount they come with sometimes (same as your Topic was shown mounted on) are excellent, well engineered and very smooth.

The Telementors are superb, consistently so. A full Telementor scope and original mount with two original eyepieces in good condition is likely to cost between £400-£700..but search here on SGL for Telementor and you'll see why people like them so much.

Dave

Often fancied a Unitron but mainly just to look at, rather than look through from what I’ve heard. Rather pricey for what they are, compared with some of the other scopes discussed here I think?

I do use my Telementor on the Unitron 114 mount and it works pretty well, although it does struggle with the weight when looking at higher altitudes because the Telementor weighs just a bit more than the intended Unitron 60 I guess?

[SuburbanMak]

12 hours ago, Chris said:

Congratulations! I've said this a million times and I'll say it again - there is something special about classic long focus refractors.... and the ladies find them irresistible too!

 

 

 

Thank you Chris. I think she prefers the C100E...

Edited November 5, 2021 by SuburbanMak