Whats the differance?

[KyleStoke]

The following two scopes seem very similar but with a quite a different price tag etc.

first up is this TS Photoline 107  made from carbon fiber what advantages/disadvantages does this have?

and secondly this APM APO Super 107/700 more expensive but I assume that is because of the name/proven reputation.

Anyone had any experience with either scope or input of any type?

Thanks

Kyle

[KyleStoke]

It seems everyone is as in the dark as me, if only in had a spare 5k id get both test them side by side and report back

[RikM]

I don't know either of the scopes but carbon fibre is normally used to add stiffness and reduce the effects of thermal expansion. It normally gives a bit better focus stability than metal tubes all other things being equal.

[KyleStoke]

Cheers Rik, so its a positive to be carbon fiber

[Astrobug]

From what I have heard carbon is usefull only for reflectors but not for refractors.

The expansion of the tube is conpensated by the expansion of the lens.

[KyleStoke]

From what I have heard carbon is usefull only for reflectors but not for refractors.

The expansion of the tube is conpensated by the expansion of the lens.

Does this mean it has no effect on a refractor or has a negative effect, i read in reflectors it saves weight is interfered with less by temperature change and is stiffer

[wuthton]

Does this mean it has no effect on a refractor or has a negative effect, i read in reflectors it saves weight is interfered with less by temperature change and is stiffer

Generally reflectors are bigger, heavier and have much longer focal lengths than refractors. Carbon reduces the weight and focus shift with temperature change to a noticeable degree.

As refractors are generally a shorter focal length and the tube is not the heavy bit the gains will be much less noticeable.

[Astrobug]

Lets say in alu the total effect is less negative vs using carbon on a refractor.

On a reflector you save some weight but not that much (speaking for my scope) vs an alu tube and if your scope is F5 or slower you stay well in focus.

On faster scopes F4 and below many like temperature compensated focusers but I have no experience on these scopes.

[KyleStoke]

Lets say in alu the total effect is less negative vs using carbon on a refractor.

On a reflector you save some weight but not that much (speaking for my scope) vs an alu tube and if your scope is F5 or slower you stay well in focus.

On faster scopes F4 and below many like temperature compensated focusers but I have no experience on these scopes.

Generally reflectors are bigger, heavier and have much longer focal lengths than refractors. Carbon reduces the weight and focus shift with temperature change to a noticeable degree.

As refractors are generally a shorter focal length and the tube is not the heavy bit the gains will be much less noticeable.

Cheers guys so basically it makes no difference for the refractor.

So thats one part of the original question solved, anyone had any experience with either scope?

[Astrobug]

You can allways ask TS for a starttest on the bench?

[Jarno_c]

I think you've already summed up all the differences. Same objective diameter, same focal length and same price range - I'd hazard a guess and say that the optics are from the same manufacturer. They also appear to have the same focuser and tube rings so that just leaves the tube itself and the brand name. Assuming that they are optically the same I looked up the APM scope on their own website and compared the spot diagram to that of an APM-LZOS. Apparently the claim from Teleskop-Express that these scopes are optically very close to LZOS is true. Given the fact that the Teleskop-Express has a carbon tube that's also modular (always enough backfocus!) and is cheaper to boot, I know which one I'd choose...

Jarno

[ollypenrice]

Lens quality will vary. What do the lens manufacturers do with the best, the medium and the worst quality units they produce? Throw away all but the best? I doubt it!    Behind the scenes all these lenses will find their way into the market place. How do you know wht you're getting? I have no idea. Are they all equally good? They can't be! Do I believe anybody who claims to know how to buy only the best of the bunch? No.

Olly

[KyleStoke]

I think you've already summed up all the differences. Same objective diameter, same focal length and same price range - I'd hazard a guess and say that the optics are from the same manufacturer. They also appear to have the same focuser and tube rings so that just leaves the tube itself and the brand name. Assuming that they are optically the same I looked up the APM scope on their own website and compared the spot diagram to that of an APM-LZOS. Apparently the claim from Teleskop-Express that these scopes are optically very close to LZOS is true. Given the fact that the Teleskop-Express has a carbon tube that's also modular (always enough backfocus!) and is cheaper to boot, I know which one I'd choose...

Jarno

Jarno good points indeed. not sure I actual understand the spot diagram myself

Lens quality will vary. What do the lens manufacturers do with the best, the medium and the worst quality units they produce? Throw away all but the best? I doubt it!    Behind the scenes all these lenses will find their way into the market place. How do you know wht you're getting? I have no idea. Are they all equally good? They can't be! Do I believe anybody who claims to know how to buy only the best of the bunch? No.

Olly

Olly, that is very philosophical but to true.

I guess APM been the higher quality name would demand the better quality optics but, but as is said above who can guarantee this. Its all in the reputation 

[ronin]

There is a connection, either business or personal, between TS and APM. Cannot recall the details of something i read but there at least a working relationship.

The APM 152 f/7.9 I have seen branded as TS (also Lunt I think), the TS variant appears to have disappeared now but it was there a couple of months back, and I expect will reappear again.

Also other scopes that started as APM are available as TS items.

Whether or not there are A, B and C grade lens (Strehl) used on different ones I do not know.

Concerning CF I thought that it was a better insulator so cool down was extended. Equally a refractor is not exactly air tight so air should exchange without problem.

[Jarno_c]

Oh, there's definitely a relationship. They've obviously agreed to stay out of each others way for the most part. Generally speaking APM targets the high end of the market while TS caters to the intermediate and entry segments. TS states that "every single Apo is being tested on our optical bench before shipping" so they should be able to provide a test report. CF is indeed a much better insulator but refractors don't have a large volume of air inside the OTA so they aren't that sensitive to tube currents. Unless you happen to be one of the lucky few who own something like this.

@Kylestoke: I'm not an expert but here's what I undestand about reading a spot diagram. The numbers on the left are how far off-center the measurement is made: the top row is on-center and the bottom row is pretty far out at 21mm, that's all the way in the corner of a full-frame sensor. The top row is the wavelength in microns. Note that the color of the plots doesn't necessarily correspond to the color of the light although that's how it's usually done. The black circles are the Airy disk for that particular wavelength, the smallest point to which a perfect lens can focus a beam of light. The rest is pretty simple. Basically, the smaller and rounder the spot, the better. Looking at the APM diagram you'll see that in the center green light is focused into a smaller spot than the Airy disk so the lens would perform better than a perfect lens. Obviously this isn't going to happen but assuming the plot is accurate then in practice the lens should only be limited by diffraction.

This brings me to a question of my own (and apologies for the thread hijack): if you have a spot size which is larger than the Airy disk but smaller than the pixel size of your camera, can you expect the aberration to show in the picture or is it still beyond the camera's resolution?

Jarno

[KyleStoke]

Oh, there's definitely a relationship. They've obviously agreed to stay out of each others way for the most part. Generally speaking APM targets the high end of the market while TS caters to the intermediate and entry segments. TS states that "every single Apo is being tested on our optical bench before shipping" so they should be able to provide a test report. CF is indeed a much better insulator but refractors don't have a large volume of air inside the OTA so they aren't that sensitive to tube currents. Unless you happen to be one of the lucky few who own something like this.

@Kylestoke: I'm not an expert but here's what I undestand about reading a spot diagram. The numbers on the left are how far off-center the measurement is made: the top row is on-center and the bottom row is pretty far out at 21mm, that's all the way in the corner of a full-frame sensor. The top row is the wavelength in microns. Note that the color of the plots doesn't necessarily correspond to the color of the light although that's how it's usually done. The black circles are the Airy disk for that particular wavelength, the smallest point to which a perfect lens can focus a beam of light. The rest is pretty simple. Basically, the smaller and rounder the spot, the better. Looking at the APM diagram you'll see that in the center green light is focused into a smaller spot than the Airy disk so the lens would perform better than a perfect lens. Obviously this isn't going to happen but assuming the plot is accurate then in practice the lens should only be limited by diffraction.

This brings me to a question of my own (and apologies for the thread hijack): if you have a spot size which is larger than the Airy disk but smaller than the pixel size of your camera, can you expect the aberration to show in the picture or is it still beyond the camera's resolution?

Jarno

Jarno, Good info there, when i was looking at the spot diagram I was a bit over faced by the amount of info