Jump to content

Walking on the Moon

TS Optics Imaging Star 80 mm f/4.4 Flatfield APO review

Recommended Posts

Hi Every one, I have been looking around for another scope for a while now and, I have to admit, I am always cautious of parting with my hard earned cash on any thing, I try and do my home work on what ever I purchase especially when it comes to Astro gear.
so after many hours of shall I or not this is the scope I picked, I am writing up a small review to show you what this little scope is all about  in case your were might be interested in it / or not.
The scope arrived from Bernard at Modern Astronomy just after the last bank holiday Monday.
The box itself felt very heavy for its size and was in good condition delivered by DHL.
after opening the first box I was presented with another box, then another then another until I could see the actual transport box the scope lives in, well packaged came to mind, which is a good thing.


Inside the Transport case the scope revealed itself at last, looking nice in its white and glossy black finishing's.
once out the wrappings it was place on top of the case so I could get a good look at it, checking for marks or any thing that should not be there, all was good, optics looked nice and clean all great so far.




Having had more basic scopes in the past, it was nice to have a rotator on the focus mechanism, which allowed to rotate the focus knobs on top so it cleared the fixing plate, which is very handy if like me you have quite a bit of weight hanging off the back of the focuser and have to push the scope further up in the saddle in the mount, or you just find it easer to have the focus Knobs on top, the rotator was very smooth and positive with a nicely knurled big knob to tighten.
The focuser is a 2.5 ich rack and pinion and  was very smooth, no lumpy of gritty bits here, when using the 10:1 focuser very smooth indeed, no effort required at all, as it should be.
winding the focuser out o the max I was nicely surprised by the amount of travel 88mm in all, Liking this scope allot so far.


At the end of the of the focus tube another rotator, which I was surprised about as nearly all pictures I had seen on this scope it had a tilt mechanism on the end not a rotator, that threw me a little, but after attaching  my normal imaging equipment to it a Atik 383L and Efw2 filter wheel and undoing the three retaining thumb screws a little it rotated a charm, very smooth, on the air of caution don't undo the screw to much , not that you have to, but where the screw go into the recess part it is not that deep so more than 5 turns on the thumb screws your Equipment will fall off.
Just inside, at the back of the rotator you have the Reducer / flattener which is fixed into the inner part of the draw tube, its screwed in for a good connection, all connections are screw in if you unscrew the rotator you will have a m68 thread the rotator and the tilt mech have a m48 thread which screw directly onto the m68.








The lens hood had a good amount of travel, and should stop stray light entering , and very smooth travel over the scope body,
a nice little feature is the Retaining nut on the hood, so once fully extended lock it up and it stays there, also it has a screw in metal cap on the end of the hood, which you ether love them or hate them, compared to a push on cover.



The only gripe so far and it is a very, very small one is the side of the focus knob with the 10:1 travel, the cover for it is so loose it will always fall off,
as I said small gripe.

Now to the fun part, a clear night on the night of delivery  (not a chance I hear you say ) well the gods were being kind and I did have a clear night,
Now the interesting part, what to set the back distance at well, you would think that would be the easy part really, go on the TS web site  and get the back focus distance in the information box,
well the information is there but for the tilt mechanism not the rotator which my scope had come with.
Easy I thought go on the web go on Google and find the information simple yes: No not really, information as yet on this scope is very far and few between at the moment ( hence the review ) and what info is out there its orientated mainly towards the tilt mech.
I have been in a private chat with a member on SGL who is in the same predicament as me and both of us have been going out when the slightest glimmer of a clear sky has been forecast and I have to admit over the past few days it has been off and on with high cloud with clear patches.
Both of us knew that spacing and focus would be quite critical on a reasonably fast frac with a 42mm flat field, how critical, I was about to find out after at least 20 attempts of getting it some where near good.
Having 4 other scopes that have Reducer / Flatteners in them I though this would be a breeze, all the Reducer / Flatteners I have are always around the 55 to 56mm back focus.
so with lots of trial and error around this bench mark I was getting results but not up to the standard this scope should deliver, In fact after 5 hours of trial and error I was getting a little concerned.

picture below of ic 1396 one of the many back focus tests, 5 x 10 minute ha





as you can see not good at the corners and sides at 100% , its not the scope at fault it me :)


ic1396_mosaic at 64mm.png


But last night after re-evaluating my distance buy subtracting the differences between the tilt mech and the rotator I was getting closer, as it stands at the moment I am within 2 mm of optimum back focus, I need to get some 1mm and 0.5 mm shims to get it better.
the distance I am using at the moment is 58mm I need to loose about 1.5 - 2.0mm to get it better please see side view of picture, please note, this is an older picture the variable spacer is not in there now.

5 x 5 minute subs for lights and 1 x 5 each of rgb, due to cloud last night the test was cut shorts but stating to look promising, once I fine tune the Back focus.
I have the tilt mech arriving any day soon as the is slight tilt.









small, compact
fast optics F4.4
well made
Nice options for framing and fine tuning with the tilt mech /or rotator
Great for wide field shots, FL 352mm
Comes with a very nice storage case
Very twitchy on back focus distance
10:1 focus knob cover way to loose.
I hope this small review will help you decide if this scope is worthy of your hard earned cash or not,
any questions please ask.

will update with more information and astro pics weather permitting


Edited by ultranova
added more pics and another
  • Like 6
Link to comment
Share on other sites

Good review Paul.

As the other member here with one of these I can confirm everything Paul has written. This thing is *very* sensitive to spacing, and you'll need that fine focus knob as you can go through focus and out the other side very easily.

ATM I'm working on 84mm from the m68 thread and leaving out the rotator, but I have tilt in my Trius that hadn't been a problem before but is giving problems now.

  • Like 1
Link to comment
Share on other sites

That is a good and thorough review. I'd call F4.4 more than 'reasonably fast' for a refractor, I'd call it screamingly fast! Not many refractors go inside F5, after all, and doing so is never going to be easy for a maufacturer either optically or mechanically. I hope the fine tuning of tilt and chip distance go well and that you'll be back with more.


  • Like 1
Link to comment
Share on other sites

Update :

after getting the tilt adapter from TS, I could now for the first time work out accurately the 68mm

quoted for the back distance to within 1mm

having the rotator on which is longer than the tilt adapter Means I could just about reach

the optimum back focus stated, which is ok but I really would have liked to keep my LP filter

on but that has a m42 thread on it rather than the m48, at the moment my set up has a m48 to m42

adapter on it,

All is not lost as I can put the tilt adapter on which will give me another 25mm to play with, maybe a

off axis guider then the LP filter.

I have attached another photo with the more up to date measurements, going by what TS has quoted

for there 68mm back focus I am there +/ - 1mm,

people with OSC cameras will find it much easier to get the back focus, just take the measurement

from the beginning of the of the 14mm wide rotator part, (don't include the 8mm )  then from there you just need

your back focus distance for you chip, so say you back distance is 20mm you should

have 26 mm to add in your couplings.

which is also a bonus because this works out almost spot on for the Canon slr, most adapters for the camera to the scope are around 10 mm

thick I purchased the very thin 1mm  canon to m48 adapter form Bernard at Modern Astronomy, this allows you to screw the adapter

straight onto the m48 thread on the rotator for pretty much spot on 68mm .

The only verification that I have that these measurements are ok at the moment is I took some day light pics

with the canon attached , it is modified so it has a red hue to the photos, after close examination of the photos,

they do look sharp to the edge, not as good as a star test, but soon as a clear patch arrives I shall get some

decent tests done,

stay tuned for hopefully a image with reasonable stars in the corners soon :) 


60 v3.jpg



  • Like 1
Link to comment
Share on other sites

UPDATE : Well what a journey it has been with this scope and its still not over

Hoping the Tilt adapter would more accurately get me to the quoted 68mm

as quoted on the TS website,

I can confirm its not 68mm ,  in fact still at the moment I can not actually tell you what it is

the sad thing is neither can TS optics, I shall explain.  

 Having the good fortune to of had good weather the past week or so to experiment with trying to

get the best out of this nice little scope with the help of another  SGL member who is in the same predicament as me

we have been in communication on nearly a daily basis trying to resolve where the optimum back focus is for the scope

should be reasonably easy, how wrong were we,

spending nearly all our the clear sky time on trying to get the best out of this scope, in fact I am begging to believe

that getting ok star shapes in the corners of even a smallish chip is near on impossible, yet On the TS website where

on the review of this scope there are two pictures, which you can not make very big to look at but none the less

the stars look quite fair, not distorted ,

after the first night some time last week I rigged it up so that I could use a variable adapter of which I have three

I started at 44mm from the tilt plate, ( bear in mind TS said it was 68mm ) and worked out in 1mm increment's taking 30 second

  subs in a reasonably star populated  part of the sky, , zooming in to all for corners on bin 1 subs checking , discarding the sub as stars

were very badly elongated, then coming out a another 1 mm refocusing taking another  sub and repeating,

Now before I bore you to tears, suffice to say, the best measurement I got and I went up to 96mm ,

pic at 96mm

98mm ff.png


98mm mosaic.png

Clearly 96mm is way to far back,

 one at 78mm

78mm mosaic.jpg

and one at 68 mm The Quoted back distance by TS using the tilt adapter.

68mm mosaic.jpg

as you can probably see the 78 from the tilt adapter is a little better than the 68 quoted, but still not brilliant,

or if you have the rotator ,( I have both  ) its about 56.5 mm about the same as the more common R / F out there around

the 55mm mark.

I purchased some fine tuning spacers from our loverly people at FLO, so I could have more options around the 54 to 57mm

after taking more subs with fine tuning, I found that the stars were not getting much better, here are some quick pics I took with the

imaging time I had left. at

4x 10 minute ha subs at 76mm

ngc7000 76mm from tilt adapter.png

ngc7000_mosaic at 76mm from tilt adapter.png

 pelican 1.png

a quick mosaic

pel and friend.png

with the WO zenith star at half the cost and only 1/3rd of a f number slower below

sadre with wo zenithstar 71 at f4.7.png

m1_mosaic wo zenith star at f4.7.png

with the new scope as best as I can get it so far

sadr at 76 mm from tilt adapter.png

Autosave_mosaic 76mm from tilt adapter.png

all told I have probably taken about 100 x 30 second exposures and  re - focused let the scope settle then redo,

The only reason I have been so patient with this scope is I like it and I desperately want it to work, but after 7 hours now

of trying I think I a going to give up soon,

Bernard from Modern Astronomy, Is helping me to try and resolve the issues, but when TS done even know there back focus

of the R/F that they have in one of there own scopes that speaks volume's to me, but more to the point they did not even offer to try and find out for me

, they just apologised for the inconvenienced caused, .

Im just glad I got mine from Modern Astronomy, Like FLO they help you no matter what, I feel for DaveS, the other SGL member that has had

his scope a few months but due to bad weather he has only now really being testing this scope out, and is struggling the same as me.

so be warned people, take this information and make your own mind up.

I will keep updating the review hopefully with better star shapes, but at the moment I am not convinced that will happen.

I can confirm  the light cone is flat as stated, (flat field) but is it a optically well correct cone of light ?

78mm mosaic.jpg

  • Like 1
Link to comment
Share on other sites

  • 2 weeks later...

Another update :

The Journey continues,  after several contact Emails with TS, the last reply I got

said there is a problem with the scope so a exchange / return to fix .

In some ways I was relieved to here that as the time put into this scope now adds up more than 11 hours

of clear sky wasted, and that's not including the 4-5 hours testing on a Artificial star.

The questions that's buzzing around in my head is, is this a one off, Was I just unlucky to receive a faulty one

As this is ( as far as I know )a relatively new scope on the market information on the web about its overall

performance is  almost nothing.

The scope if it can be corrected to a more decent level has lots of promise, and should be a winner if

the optics can be sorted, I personally think TS could have a winning scope on there hands.

Stay tuned for the next parts of the review.



Edited by ultranova
Link to comment
Share on other sites

The scope is not exactly "new" it came out initially under the APM brand, it changed to have the TS brand on the side after a while. They in effect reproduced the William Optics GTF-81. I would suspect that it is the WO GTF-81 from the same manufacturer but branded APM or TS. I was looking at the scope about two years ago maybe more, I kept a bookmark of it. I effectively gave up thinking about is as WO came out with the WO GTF-102 which received great reviews from the US.

So TS or APM should have by now a very good idea of the required distances, they have had a few years to work it out, at a guess they could just say use the William Optics distances.


Link to comment
Share on other sites

I did have an email from TS just after I'd bought it as the outer box said 80mm f/6 and I wanted clarification. Apparently it starts life as a bog-standard 80mm f/6 then has a reducer fitted to bring it down to f/4.4.

I've put this on the back-burner until I get longer dark as I'm fed up with bashing my head against this thing (Or even the wall) at stupid o/c.

I'm back to using the Meg 90 and reducer.

Link to comment
Share on other sites

Shoot me down in flames by all means but I see no reason to believe that the manufacturers know how to mass produce these small fast refractors with an acceptable probability of their working to spec.

We have moved from the consistent successes of the stalwart ED80 (F7.5/F6) to thread after thread of dodgy corners and distorted stars. Is it not time to ease up on the flashy numbers and settle for something more like F6? I'm not a fan of extreme optics because I like optics to work. Lord knows, the IT side of the imaging business gives plenty of opportunity for random failure. At least optics can in principle be perfectly reliable, night after night, if you don't ask for more than the makers are competent to deliver. I could live with F6 and I believe the mid-price manufacturers know how to do that.

It's a bit like houses. The developers want to be able to put '4 bedrooms and garage' on the description so you end up with garages in which you can't open your car door and bedrooms in which you can't fit a bed.

I counsel F6!



Link to comment
Share on other sites

No Olly, I wouldn't shoot you down in flames, I think TS (Or whoever makes these things) has been a bit optimistic in pushing it to f/4.4 when an even 5.0 would have saved a lot of problems. They have another couple of these 3+3 designs working at 5.1, and 5.0. My Megrez 90 with 0.8 reducer reaches f/5.3and gives a much better image than this. The problems WO had with their original 71mm f/4.9 gives weight to your argument.

I think my next 'scope will likely be a 130 f/7 Triplet Apo, with a flattener and a 0.79 or possibly 0.75 (Riccardi) reducer.

Meanwhile I need to gather more evidence of the defects in my example before emailing TS to seek a resolution. Blast these cloudy nights.

Link to comment
Share on other sites

I know what your saying Olly , but you would look at the house before you purchased it

would you not, unfortunately, Telescope manufactures and the people that sell there scopes for

them like FLO and the countless others do not give you the scope for a try before you buy option

And why shouldn't I be able to purchase a f4.4 or a f3.6  scope and expect a certain level of

star shapes in the corners.

I am a very keen photographer and I pay premium prices sometimes for the best optics I can afford

but I don't just choose the brand names that goes with my Camera I pick the best Lens from who ever

is making it and at sometimes half the cost of a higher brand name and so far that has worked out well

I suspect you use Your Tak's at f3.6 when doing wide field  shots, I mean why would you want

to have a scope that can operate at f3.6 and not use it, I dare say at f3.6 if your stars were bad

in the corners you probably would not be using a Tak,

My point is I am not expecting perfection in the corners, Its not a scope I have just paid £4000 plus for

but what ever the cost that's irrelevant, manufactures say they are going to deliver a certain level

of quality, then is it not to much to expect them to deliver there promise.

and as for mass production I have a f1.4 lens that produces exception results in the corners

at f1.4 and it has twice the amount of glass in it that the scope I have purchased has

and they are mass produced.

IF it was not for mass production and decent quality control I would still be taking photos

on a box brownie at f10

In saying all that the yes you are correct Olly if every one stayed at f6 /f7 a lot more

simpler it would be :)





Link to comment
Share on other sites

I think that in this case and in many others there is an interaction between the buyer and the seller in which the seller anticipates what the buyer wants (in this case small fast refractors at less than half Tak price) and tries to deliver it. Inevitably competition between manufacturers means that they don't want to be the ones to say they can't do it, they all want to be the ones who say they can do it. So they push to the very limits of what they can do, they get some prototypes to work, and they go into production.

This interaction is 'policed' by the laws of consumer protection. If they say the scope can do it, it must do it or the sale can be recinded under the law. This system is working, but it strikes me that it is creaking as a system since customers like you are being put through endless faffing about which, in the end, will not be recompensed. Nobody will pay you for your time.

My contention is that it would be better all round for the consumer to demand a little less and the manufacturer to promise a little less by either charging a little more or easing off on the spec or both. If this were a defence procurement contract and you were dealing with the manufacturer to decide price and spec I strongly suspect that you'd pitch in for a slightly slower F ratio and - quite possibly - a slightly higher price.

The free market is not a procurement contract, it's an environment in which manufacturers are tempted to promise the impossible. I've said this before but I think the purchasing community should start to make it a bit clearer to manufacturers that we only want products which work. I can guess that they might come back with, 'Yes, but you won't buy them if we make them, you'll buy the ones our rivals fail to make reliably...' 


  • Like 4
Link to comment
Share on other sites

You are of course 100% correct Olly, its just a shame that us the consumer

plays a guinea pig roll in all this, and some of the sharpest photo's I have ever

taken was with my sw 80 ed and f/r at 6.3, and well proven and trusted little scope

I am just hoping that TS can sort this scope as it would be a cracker for the outlay,

we will have to wait an see.

Link to comment
Share on other sites

I must say that I salute your patience.  I have had to return 3 scopes because I couldn't get decent stars in the corners.  I think I was lulled into a false sense of security by my ED80, which just 'worked'.  But I wonder if Olly might be on to somethng with his idea that we should demand a little less and pay a little more.  My next purchase is f/7.  I have fingers and toes crossed.....

Link to comment
Share on other sites

11 hours ago, gnomus said:

I must say that I salute your patience.  I have had to return 3 scopes because I couldn't get decent stars in the corners.  I think I was lulled into a false sense of security by my ED80, which just 'worked'.  But I wonder if Olly might be on to somethng with his idea that we should demand a little less and pay a little more.  My next purchase is f/7.  I have fingers and toes crossed.....

F7? That's not.... :eek::D


Link to comment
Share on other sites

That would be money well spent in my opinion.

Having had my fingers burned  over this 'scope I'm more wary of buying in the future. I note the Altair Wave series of 'scopes come with a test report so you do at least know what you're getting.

Debating with myself whether to see if I can send it off to Es Reid to find out exactly what's going on.

Link to comment
Share on other sites

There was a post on CN a while ago from a guy with a WO132 that had problems and William Yang personally took him another one to try along side it to see if it worked any better.

Shame he couldn't pop over to the UK with a few Star 71s to distribute :)


  • Like 1
Link to comment
Share on other sites

3 hours ago, Singlin said:

How about paying an extra couple of hundred quid for the seller to make sure or adjust the optics before shipping?

Would that necessarily give good results though?  I have no idea how optics are tested and adjusted - do they take them out into the field and do corner star tests?  Is there a bench test that can be done that will tell you if you can get round stars in the corners?  I hear it said that Petzvals can be prone to collimation errors.  But is it possible that a scope could have all of its elements perfectly parallel with one another, but for there still to be errors because the lens spacing within the scope is awry?  I would genuinely like to know.   

Link to comment
Share on other sites

4 hours ago, ollypenrice said:

Totally mad! 'Mad as the sea and wind when both contend which shall be mightier.'

Actually now that I think about it perhaps the word 'mad' is inappropriate.  If I present myself to the thought police will they give me a lighter sentence?  We need a new euphemism for 'stark raving bonkers' - can I suggest the word 'Astrodon'?

Link to comment
Share on other sites

1 hour ago, gnomus said:

Would that necessarily give good results though?  I have no idea how optics are tested and adjusted - do they take them out into the field and do corner star tests?  Is there a bench test that can be done that will tell you if you can get round stars in the corners?  I hear it said that Petzvals can be prone to collimation errors.  But is it possible that a scope could have all of its elements perfectly parallel with one another, but for there still to be errors because the lens spacing within the scope is awry?  I would genuinely like to know.   

There are bench tests for optical alignment, but they're a bit specialised, Zygo interferometers etc. The optical elements can be parallel to each other, but if they're not centered then the stars will not be round. And if the elements are not correctly spaced there certainly will be errors, quite severe ones.

Link to comment
Share on other sites

1 hour ago, gnomus said:

Actually now that I think about it perhaps the word 'mad' is inappropriate.  If I present myself to the thought police will they give me a lighter sentence?  We need a new euphemism for 'stark raving bonkers' - can I suggest the word 'Astrodon'?

*sniffs* Dagenham, 'cos it's beyond Barking.

Sorry, (West) Londoners' joke.

  • Like 2
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.