[Review] TS 115mm f/7 Photo-Line Triplet APO

[Stratis]

So as some of you may remember from my other thread, I am now the proud owner of a 115mm Triplet APO, from Teleskop-Service in Germany. Purchased second-hand on eBay for a mere £750 and in mint condition as far as I can see, I will try to review the general finish and mechanics of the scope ahead of first light, hopefully this evening if the forecast holds.

Specs

This scope is the middle-child of the Teleskop-Service 'Photo Line' range of refractors, generally ED glass instruments around f/7, designed with astrophotography in mind but also excellent visually by all accounts. 

• 115mm f/7 triplet objective; Ohara FPL-51 glass element
• 3" Rack-and-Pinion dual-speed focuser with dual locking, rated for 6kg loads
• Retractable dew shield, screw-on metal cap
• Heavyweight CNC tube rings

...and that's it really. 

The scope is extremely sparse in terms of extras, only the essential elements of a telescope are there; optics, tube, focuser and tube rings. No apparent provision for a finderscope except for two mysterious holes on the focuser, but they dont match any standard fitting I recognise. 

First Impressions

The scope arrived in a flight case which ParcelForce have managed to actually crack and damage, presumably by booting the package across a warehouse floor with code-compliant steel toecaps. 

Fortunately the scope within survived unharmed

First glance, the scope is extremely dense and oddly heavy like most triplets. It can be hefted in one hand, but it is substantially weightier than the 102ED doublet in my stable from (I believe) the same factory and the knowledge of its value seems to add a couple of kilos to that .

Even with the tube rings removed, the additional aperture and triplet element makes itself felt immediately. I wouldn't mount this casually, but I suspect at 8kg plus whatever the focuser adds on, anyone with an HEQ-5 or bigger should find their mount equal to the task.

 

Compared to the 102ED, it is clear that the scope is larger in every sense. The engineering is a serious step forward, Nick from Altair informs me that my particular 102ED is an earlier tube design and therefore lacking in mechanical finesse . I have absolutely loved every minute with my 102ED, so this one does have quite a hill to climb to earn my esteem.

Mechanics

The only real moving parts of this scope are the dew shield and that immense focuser.

The dew shield extends easily and benefits from a little locking screw.... personally I find this one too long so I will probably replace it with something else, but its a nice thought and it prevents the dew shield slipping back down or slipping forward in transport, both of which have occurred with the 102ED.

  

The focuser.... oh wow this focuser.... frankly I am at a loss to think who would truly need such a device. It is rated for over 6kg and a stepper motor is available for it rated at and beyond this weight class. I image with a full-frame DSLR and I am nowhere near 6kg of draw weight. I am told by my TS insider that the focuser is actually rated for this straight down without slippage. Spectacular.

The terminus also sports a huge M68 thread; this fits a number of internally-mounted flatteners and correctors, as well as some medium-format accessories in case I find ten grand in the change jar.

As a result, the focuser is solid as a rock and extremely predictable in motion; unlike the 2" Crayford on its smaller sibling, this one is actually a bit of an inconvenience for visual use; the motion is slow and 'geary' (dunno how else to describe it, you can feel gears turning smoothly within) and bringing the focuser out can be a bit of a chore. It only happens once a session though, and I can only imagine how stable it will be for imaging use. The fact is that with all that metal sliding around, the gears keep it completely under control to the extent that ceasing pressure leads to an immediate halt to motion; all inertia is damped away to nothing.

Another superb little feature is the dual locking screw; one small screw hides beneath to lock the focuser wheels in place, and a second much thicker nylon-tipped screw actually grips the drawtube directly. This is beyond solid. With both engaged, the focuser is like an iron bar, no flex and no give at all without unsafe levels of pressure. It was around this moment - engaging and re-engaging the focuser, mesmerised - that I remembered the only other time I'd used an RnP focuser on a refractor; the Celestron SLT102, which I had owned for all of five minutes and promptly returned. That scope was returned thanks to a badly sticking Az drive, but it had a 1.25" RnP that was frankly a mess, made of pot metal. Cheaper scopes I have bought since (my £60 Aquila ST80 is a great example) have had superior focusing mechanisms, proving how far amateur scope design is being forced to advance by the likes of Kunming Optics and their collaborations with European engineering firms like Altair and TS. Yes, top Western and Japanese firms have thought of it all decades earlier, but the premiums demanded for the AP Travellers and TV-85s have kept truly well-designed mechanisms just a bit too far out of reach. I'm glad to see some real hardware engineering filtering down to the common stargazer

Finish

This scope is definitely, definitely the same provenance as my 'Ostara' 102ED, a scope I also picked up for criminally cheap as bankrupt stock and was mostly the same as the 'Ikharus' scopes once sold by Ian King Imaging and minus an upgraded focuser, the same as the Altair 102ED of years past. I have extracted some wonderful images from this scope despite obvious undercorrection of violet wavelengths; this is only noticeable with a CCD and seems to actually improve visual observation, but nonetheless there are limits that an FCD-1 doublet (that's the best guess as to the glass) cannot exceed.

Reviews of TS and Altair scopes of this family tend to mention a 'powder white finish' but I actually dissent on this point; the finish is not powdery at all. The tube surface is polished and laminated against the elements, and beneath the polish is a sparkling glittery pearlescent paintwork. It sort of looks like a blue/white version of the gold/black sparkly finish on modern SkyWatcher scopes. It's really quite pretty from the right angle, and I prefer it to the more boring and plain finishes I've seen lined up. 

The metal fittings are a kind of bronze colour, the functional components piano-black and the screws polished chrome. Not exactly heritage-grade but a very smart-looking scope to mount up alongside your mates' Dobsonians and Cassegraines without feeling like the odd-one-out.

The triplet objective cell is heavily multicoated. Without auto-exposure on the camera, these reflections are very hard to pick out. There are actually more reflections in this lens than in the 102ED, almost certainly due to the additional element.

 

Daylight Test

This caused some consternation as it turns out my house lacks a distant reference point; all I can really see are other houses, and by some quirk of luck they are juuuust out of focus for both scopes. I had to rack the DSLR adapter out to a worrying extension to reach focus at all, and even then it was truly within millimetres.

I have tried to find a high-contrast chimney to point at for both but with the light fading I had to take what I could get

First the 102ED, mounted up on the HEQ-5:

 

Secondly the new 115; significantly closer to the limits of a single counterweight to manage.

 

In addition, I decided to throw in my two baby fracs for the sake of comparison. I have an unusually well-behaved ST80, and my precious ZenithStar 66 SD:

 

Hopefully this is enough to offer a brief preliminary CA comparison (look at the purity of the 115! I thought the 102ED controlled CA well (and it does, you can only see violet if you truly pixel-peep at 20MP) but I am feeling awfully positive so far about the new boy.

Let me know if this is useful to you guys, when I get a chance I shall do a first light and see if I can photograph some focus rings for all four scopes.

Cheers, 

Paul 

[John]

Very interesting report Paul - thanks for posting it !

That scope was for sale just down the road from me and I was quite tempted by it. I'm glad it survived the journey to Oxford unscathed despite ParcelForces's best efforts

I'll look forward to reading about how it performs at night. It's certainly a very smart looking scope

[laudropb]

Thanks for the very full report. It certainly looks like you've got a good one there. Looking forward eagerly to your first light report. Hope the skies are kind to you.

[xtreemchaos]

great report mate,it looks a nice scope,remember to post some astro shots when you get firstlight..thanks for sharing..charl..

[ollypenrice]

Parcel Force need a light dose of the death penalty. This was my Takahashi's flight case after their ministrations. 

I suspect this is a relative of a scope I reviewed for AN and, if so and it's a good one, you won't be disappointed.

Olly

[Stratis]

First (De)light Report

So tonight is a gorgeous night.... I say is because I am being forced to abandon the clear skies and write this quick report before bed, got work to do during the week so can't be up til 4am again this week

I managed to get the 115 out and under the stars on the HEQ-5; I always begin my scope tests with an hour or so on 'manual'; no powerpack, no hand controller, just moving the HEQ-5 by hand. 

Eager to find out the CA situation I swung the scope to Vega and threw in an eyepiece I keep especially for this; a Meade 10.5mm Research Grade Ortho. I've found colour-hunting in Plossls and their derivatives often self-defeating, as even the best simple EPs do introduce effects inside and outside of focus. RGOs, with their minimal air-to-glass, on-axis sharpness and transmission are perfect.

The star test stunned me. In and out of focus, the star colours were near-flawless. I say near because there was still the faintest fringe of a greenish tinge just outside of focus, but the colour disappeared entirely way before focus was reached yielding a large smooth white defocused circle with a textbook interference pattern. I'd thought my 102ED was decent, but I see now how wrong I was... the triplet significantly outperforms its smaller sibling in colour correction on bright objects.

The 4" still stands up very well even against other ED doublets, but there's a lot to be said for that third lens.

I swung to Arcturus to test red correction and was even more pleasantly surprised; I could detect no false colour of any kind. Perfect coppery circles all the way. 

Star Testing

At this point I felt an urge to get some proper star tests done before proceeding any further; I wanted it on record how the two scopes compared to one another. This took a lot of trial and error (I've never done this before) and I had to throw out most of the images, but in the end I put together these series demonstrating the difference in colour correction between the two:

I am very happy with this result. It falls slightly short of the Astro-Physics star tests I've seen but then so does the price by a factor of ten. This definitely isn't one-tenth the scope of an AP.

Another facet of this scope became more apparent visually than the photos reveal; star shapes are very tight and under control, again compared to the 102ED and also to basically every other scope I own. Stars were hard diamond, as soon as I stopped concentrating on technicalities like star shapes, the true beauty of the image hit me. This was the finest view of 'nothing' I'd ever seen, just a few no-name stars around Arcturus... and yet, the view was just wonderful, with so many fainter stars showing as pinpricks than in even my 127mm SCT.

Deep Sky

Short on time, I fled Arcturus for M13, still high in the sky. The view was lovely, easily discerned core and scattered outer members; again, the scope knocks the 5" SCT out of the park. Clarity and contrast were the best I have ever experienced, the view bested in my C8 only by virtue of more stars being visible. I grabbed a couple of sub-1second shots on the way out.

Next I found the Andromeda Galaxy and again, beautiful. The wispy, smoky arms barely discernable around the softly glowing core; my C8 serves a more distinct view, but contrast and sharpness remain the province of the Apo. 

Then did I find the most stunning application for this scope yet; the Double Cluster. Personally I have never seen much point in this formation, as I have only ever seen it through small instruments unable to resolve enough stars, or large instruments without much in the way of sharpness. The 115 served a view that was just spectacular, again the superior collimation of wavelengths revealing more than the aperture would suggest. All the light comes to a sharp point in this scope, so sharp it is occasionally tricky to focus on a single star.  

I had to call an early night at this point, but early viewings suggest a superb addition to the collection. I don't know if Ill be able to part with the 102ED in the end or not, but I am definitely keeping the 115. 

[damnut]

Some great reads there, congrats on the new scope.

[Zakalwe]

You've got a steal for £750!

lovely lookig scope...I have the Altair version and I am impressed with it.

[ollypenrice]

Very good situation all round.

Olly

[Stratis]

So far the learning curve with the scope has involved the focuser; I'm just not used to such a heavyweight device.

Also, the 'locking screw' atop the draw tube isn't a locking screw at all, it doesn't even come close to fully arresting the focuser movement. I actually suspect it's a tension adjuster, to assist in fine-focusing. The screw beneath the focuser wheels is clearly the actual 'locking' component.

In terms of weight, the focuser held my DSLR with oversized adaptor and a 2" PowerMate (which is a heavyweight by itself) without slipping a millimetre; adjusting focus was difficult when climbing against gravity though, and locking focus when fighting gravity was an imprecise process. I think the proper technique has to be locking focus when at 45deg or so, before slewing to any zenith targets.

At f/7 there was no vignetting on the full-frame sensor which is a clear win at native FL, I will investigate the focal reducer possibilities.

One slightly negative point is the field flatness; in many of my eyepieces I noticed that the edge of the field incurred elongated streak-like star images, always tracing precisely outward to the field stop. This isn't visible on the full-frame DSLR test fields I took which seem relatively (but far from completely) flat, it only manifested in visual use.

Is this normal optical behaviour for a telescope of this type? It only seemed to happen with wide-field EPs like my Maxvision 34mm (which is a 2" hand-grenade) so perhaps it is a result of the triplet element at the limits of the light cone?

[Zakalwe]

A triplet will always have (AFAIK) a curved field. You will need a field flattener.

I use the Photoline 0.79 reducer/flattener. Its a bit of overkill for my Atik 428 sensor, but the field in nicely flat.

[ollypenrice]

Only systems with a rear element can have a flat field, it's true.

When we tested 'our' 115 we found the star test turning very slightly oval at the edge of a Radian but not at the edge of a wider Nagler.

Olly

[Stratis]

Understood, I thought it had to be something related to the third element.

It looked strange because I'd never seen anything like it in my SCTs (which show highly-distinct coma without the R/C, which is always mounted even for visual use) nor in my smaller refractors. The ED102 has surprised me with a nice flat field but then again, I have never used it much without the matched 0.8x reducer/corrector element.

It's clear that I need some sort of flattener.... for the time being I can re-use the 0.8x I already have, but it's far from ideal. It vignettes a full-frame (just see my M13 image) quite badly and has a T-thread keyhole to boot. It's a total waste of the massive clear aperture the 115 makes available, currently my only concern is do I go for the large flattener-only and image at f/7 or go for a combined reducer/flattener and bring it down to f/5.5, but with an impeded light cone.... 

Given that I almost always crop my deep sky images it may not matter as much as all that but still

Olly, I've read your review of the 115 on the Altair Astro site, I have confirmed the TS version is identical with the 3" RnP upgrade. Frankly, as I clearly haven't paid too dearly for it and have not yet 'fallen for' the scope with daily use (so my feelings are unbruisable right now ), how would you rate this in terms of long-term keepability? 

I had assumed I would keep my 102ED forever and ever because I loved the views so much, but the 115 has shown me a view of the Double Cluster I'll remember for the rest of my life. I may end up pivoting my future scope choices around this one, so I'd like your honest thoughts on it. I am unlikely to be in the position of buying many-thousands 130mm+ super-Apos from AP and Tak til another few years pass (only 30) and my salary climbs high enough... 

Is it a keeper in your book?

[ollypenrice]

Yes, why not? It isn't Tak/TeleVue/AP in terms of heirloom construction but, looked after, it should be fine as a keeper. And yours has the upgraded RP focuser.

Regarding reducers, all I can say is 'beware.'  I would never believe any claims whatever made for generic reducers. (This is perfect for refractors between x and y mm focal length etc.)  In truth problems frequently, though not always, spoil the party, with internal reflections often being the killer. I've seen this with the Riccardi/TEC140 paired up, for instance, and plenty of other examples. I would only go for a proven reducer-scope combination. On very rare occasions even the dedicated Tak FSQ85 reducer couldn't be used because it created flares - as when I tried it on the Witch Head when the reducer created flares from Rigel.

The official flattener-only worked fine for me.

Olly

[Stratis]

I've heard nothing but bad reports of the Riccardi reducer in terms of internal reflection. The guy who sold me the scope warned against using it for that very reason.

I've never had a problem with the cheap little 2" one I have right now, but I just want better field illumination to do the aperture justice. 

The 'official' internal flattener for this is identical to the Altair Planostar that attaches to the internal enormous M92 (I think) thread, but the previous owner also recommended the TSFLAT2 which is a little baby one by comparison. I suspect it will be a case of trial and error, but unless anyone places a TEC or TOA 130 within my reach I think I'll be sticking with this scope for a long while

[Stratis]

Quick update, as I finally had the chance to do some bright lunar viewing with the 115. My only remaining reservations were, would the triplet objective suffer from a lack of contrast, internal reflection or would there actually be unacceptable CA when exposed to such a bright white target as the nearly-full moon?

Behold some artsy shots of my setup

     

Tonight's visual viewing was with a selection of my finest eyepieces in terms of clarity; a Takahashi LE 30mm, Baader Classic Ortho 18mm, and Meade Research Grade Ortho 10.5mm. The Orthos in particular have proven extraordinarily sharp under high illumination conditions, and reveal substantially more lunar and planetary detail than even my Tal Gen2 25mm Plossl, which is the greatest example of the Plossl optical formula I've ever seen. The Tak LE 30mm is my favourite all-round 1.25" EP, and I wouldn't be parted with it ever again; the contrast it offers for DSO hunting is wonderful.

What I notice yet again is the beautiful constrast offered by the 115, I am used to tales of triplets losing out against doublets in this category but couldn't see anything of that tonight, the lunar surface was clear and sharp. My C8 was shown up yet again as a fundamentally 'muddy' view compared to a good refractor. I still love the SCT for compact aperture, but for clarity of view, my heart still belongs to the refractors.

I added a 2x PowerMate to the 10.5mm for a total mag of 152x, and a glimmer of colour began to appear at the lunar limb, revealing the slightly inferior correction inherent in FPL-51 glass, even in a triplet configuration. Interestingly, the 102ED scope I also own shows colour earlier than this but it shows the blue end of the spectrum, indicating a corrective bias towards the red spectrum. The 115mm shows no violet fringing at all, but it did show a slight reddish tint to the extremity of the lunar limb; this indicates a 'phototropic' corrective profile, optimised towards imaging where violet halos are much more difficult to eliminate than a little stray red. 

While attemping to quantify the amount of CA, I remembered that CA generally appears either side of focus; taking this as a guide, I used the appearance of the red tinge as an indicator of poor focus, and was able to completely eliminate it with a 1/16th turn of the fine focus wheel in each case. This was interesting, as sharp focusing my ED doublets does not eliminate colour like this, it simply minimises its impact on the view. I am assuming that the TS triplet objective specification is actually very well corrected, but only over a very narrow focus plane (less than 1mm), outside of which a red tinge can just be seen.

 

The first image is at native focal length, direct onto the Canon 6D sensor, no filters, no nothing. CA is clearly entirely controlled to the point of vestigiality; you can pixel-peep and catch a slight bluish tinge to the upper and reddish tinge to the lower, but I am not convinced that this is not a simple case of atmospheric refraction given it is aligned perfectly with the horizon and the moon was rather low in the sky. Seeing was very, very unsteady, leading to the softness in the amplified second image. 

The second image is taken with a 2" TeleVue 2x PowerMate in the imaging train; I love this for DSLR imaging as it allows a formidable focal length of 1.6m without adding any optical aberrations, with a full-frame DSLR sensor full illuminated.

The images seem within a pixel or two as colour-free as those taken with my SCT, and clearly superior to the earlier images with the 102ED doublet, free of internal reflections or contrast loss.

Having spent a few nights with the scope now, I am happy to conclude my review with a hearty recommendation for both visual observers and imagers. You won't be disappointed with the TS 115m!

[Brian Nordstrom]

Awsome review and scope , thanks for the time and it looks and performs excellent ! .

Hope you don't mind me posting these 2 shots , but I find my 2x 2inch powermate to be the best single bit of gear I have for luna shooting .

These were taken with my home built iStar 127mm f8 doublet that performs so well I sold my 127mm f7.5 triplet , true .

First is at native  f8 at 1000mm and second is with the TV PM at 2000mm , excellent  kit .

Brian.