Refractor considerations

[cfinn]

I setup and tear down my Esprit 120 on an EQ6R-Pro every night I go out, both for imaging and visual and it is just fine, though I certainly wouldn’t want anything heavier. It is absolutely rock solid in every respect and everything works very well indeed. I think the Tak TSA-120 looks particularly svelte and will be lighter and easier to handle but on the downside it comes with a big price premium. Optically I suspect it will be very difficult to tell these two scopes apart, though common wisdom dictates the Tak will have the edge.

[Space Hopper]

Surprisingly the TEC140 is pretty light for its aperture at 8.4kg

Its also a very manageable size. Easy to mount.

Yes, its expensive, but compare it with something like the TOA150, (or even the 130) and its not so bad.

Cooldown is rapid, faster than any other scope i've owned.

It has the best focuser in the world.

The images is gives visually are stunning. 

And I know its too good for my grotty UK light polluted skys unfortunately.....

 

@Nikodemuzz If you are after a 'lifetime scope' that will perform at the highest level, do your utmost to source one. You won't regret it.

 

[Nikodemuzz]

10 hours ago, cfinn said:

I setup and tear down my Esprit 120 on an EQ6R-Pro every night I go out, both for imaging and visual and it is just fine, though I certainly wouldn’t want anything heavier. It is absolutely rock solid in every respect and everything works very well indeed. I think the Tak TSA-120 looks particularly svelte and will be lighter and easier to handle but on the downside it comes with a big price premium. Optically I suspect it will be very difficult to tell these two scopes apart, though common wisdom dictates the Tak will have the edge.

Thanks for the input! Yes, the Esprit 120 would be easy enough to handle, I'm sure. The difference between it and the 150 is pretty substantial. 😃 The optical quality seems to be up there also, certainly not large enough to warrant the price difference. I have to admit that the main reason for leaning towards the Takahashi is a sentimental one. Since a boy I have seen pictures of Takahashi telescopes in books (and later online), and the best images seemed to often have Takahashi written in the captions. Owning one was never an idea I could realistically entertain until now, although it was a dream. So there would be a special feeling in using a Tak. Whether that feeling is worth paying double is another, very subjective matter. I'm still not quite sure for myself, but it's a definite maybe! 😅

Another twist in this story is the shortage of equipment at the moment. For the Esprit 120 the estimated delivery time goes deep into spring, meaning that it's quite likely I wouldn't get to use the new scope until next season anyway (no darkness here in May-July). A bit more time to save up then, if I so choose. If this wasn't the case I probably would have already placed an order for the Esprit and probably would have been very happy with it for the rest of my days. 😃

[Nikodemuzz]

9 hours ago, Space Hopper said:

Surprisingly the TEC140 is pretty light for its aperture at 8.4kg

Its also a very manageable size. Easy to mount.

Yes, its expensive, but compare it with something like the TOA150, (or even the 130) and its not so bad.

Cooldown is rapid, faster than any other scope i've owned.

It has the best focuser in the world.

The images is gives visually are stunning. 

And I know its too good for my grotty UK light polluted skys unfortunately.....

 

@Nikodemuzz If you are after a 'lifetime scope' that will perform at the highest level, do your utmost to source one. You won't regret it.

 

I hear you! However, if the Takahashi TSA-120 is double the price of the Esprit 120, the TEC 140 is roughly double the Takahashi! The reducer alone at 1900€ is almost as much as the Esprit 120. I was able to present this investment plan to the better half in such a way that she recommended that I go for the Takahashi, but I'm not sure my rhetorical skills could raise the bar enough to reach TEC prices. 😬😅

Used? Yes, absolutely, if only I could find one!

[Nikodemuzz]

One thing I started to think about is thermal performance. Living here in the North means that the scope will have to be able to withstand -30C and lower temperatures without pinched optics or mechanical issues. I keep my equipment in a room that is typically a few degrees above 0C, so not quite room temperature but not ambient either. If a scope cools very slowly and the temperatures are plummeting outside, will it ever reach thermal equilibrium?

What sort of differences should I expect between the Esprits and the Taks in this regard?

I have understood that all in all oil-spaced solutions cool faster than air-spaced. Oil spaced would mean TEC, CFF, or some Astro-Physics scopes. Are there others within the context of my criteria?

[Sunshine]

On 25/01/2021 at 03:49, Nikodemuzz said:

The reducer alone at 1900€ is almost as much as the Esprit 120.

OMG! is that a fact?  insanity.

Edited February 9, 2021 by Sunshine

[jetstream]

11 minutes ago, Nikodemuzz said:

If a scope cools very slowly and the temperatures are plummeting outside, will it ever reach thermal equilibrium?

If were talking refractor triplets-yes.

Re: lens cell vs -30c

1. Some scopes cool down successfully at times, not always like my SVRT90 and SW120ED. The SV has had more succesful cooldowns.

2. My Tak 120 so far has cooled successfully every time, no astg from cell distortion/pinched optics. There is a zero guarantee they will all work like this

3. Avoid oil spaced triplets for cold temps- its very hard on them.IMHO

4. Once a successful cooldown happens its my experience the scope will be fine, no aberrations.

5. Keep trying and if a succesful cooldown happens just keep the scope near ambient. ie my 90mm SV is ready to go, in the seacan at -30c today.

These are just my thoughts on this.

[Nikodemuzz]

1 minute ago, Sunshine said:

OMG! is that a fact?  insanity.

It's pretty nuts, isn't it. Suddenly the Takahashi accessories seem reasonably priced, even cheap! 😃 

I believe this is the one that is usually recommended with the TEC140: https://www.baader-planetarium.com/en/072x-telekompressor-korrektor-für-tec-140160180.html

I don't know if it's the only reducer you can use with the TEC, maybe an owner could inform us on that. Of course you don't NEED the reducer, but it would be nice to have. The dedicated flattener is not exactly cheap either, at 900€.

I'm sure the quality is there, though.

[Sunshine]

4 minutes ago, Nikodemuzz said:

It's pretty nuts, isn't it. Suddenly the Takahashi accessories seem reasonably priced, even cheap! 😃 

I believe this is the one that is usually recommended with the TEC140: https://www.baader-planetarium.com/en/072x-telekompressor-korrektor-für-tec-140160180.html

I don't know if it's the only reducer you can use with the TEC, maybe an owner could inform us on that. Of course you don't NEED the reducer, but it would be nice to have. The dedicated flattener is not exactly cheap either, at 900€.

I'm sure the quality is there, though.

This is not the only reducer I've seen in that price range or even higher, it begs an explanation by an optics expert, please, someone please explain how a reducer could possibly cost so much.

Are they very difficult to make? do they break 6 lenses before getting one good one? I would understand that.

Edited February 9, 2021 by Sunshine

[Nikodemuzz]

2 minutes ago, jetstream said:

If were talking refractor triplets-yes.

Re: lens cell vs -30c

1. Some scopes cool down successfully at times, not always like my SVRT90 and SW120ED. The SV has had more succesful cooldowns.

2. My Tak 120 so far has cooled successfully every time, no astg from cell distortion/pinched optics. There is a zero guarantee they will all work like this

3. Avoid oil spaced triplets for cold temps- its very hard on them.IMHO

4. Once a successful cooldown happens its my experience the scope will be fine, no aberrations.

5. Keep trying and if a succesful cooldown happens just keep the scope near ambient. ie my 90mm SV is ready to go, in the seacan at -30c today.

These are just my thoughts on this.

Thanks for the input, Gerry! Good to hear your experiences, I know you enjoy an even colder climate than mine.  

What makes you say that the cold temps are especially hard on oil spaced designs? Is it because of the oil is squeezed between the elements as the lens cell contracts in the cold? Air is compressed but oil won't, causing stress? 

[Nikodemuzz]

6 minutes ago, Sunshine said:

This is not the only reducer I've seen in that price range or even higher, it begs an explanation by an optics expert, please, someone please explain how a reducer could possibly cost so much.

Are they very difficult to make? do they break 6 lenses before getting one good one? I would understand that.

I dom't think that there is a justification in the optics or the design, but I would be happy to be corrected on that.

I think it's just that Skywatcher et. al. can produce these thing in large enough quantities to drive their prices down. Even Takahashi production is large scale compared to AP or TEC, I imagine. There is probably a decent amount of steps and time that go into making a reducer when it's done by a person, so there we go. Often I like to support the craftsmen and small producers, in this case I don't have the coin for that, at least if buying new.  

[jetstream]

34 minutes ago, Nikodemuzz said:

Thanks for the input, Gerry! Good to hear your experiences, I know you enjoy an even colder climate than mine.  

What makes you say that the cold temps are especially hard on oil spaced designs? Is it because of the oil is squeezed between the elements as the lens cell contracts in the cold? Air is compressed but oil won't, causing stress? 

Years ago I talked to Astro Physics and wanted to buy a scope- they are excellent to talk to- but didn't want to wait years for one. I was advised against the oil spaced lenses for hard fast cooling. "Lens shock". I think the oil can leak out.

I tried to find  info to post but can't find it. Maybe check the Company 7 web site.

I enquired about a TEC but no response. I would still own an oil spaced refractor but wouldn't risk using it in the extreme cold.This is another plus for the TSA120-air spaced.

Edited February 9, 2021 by jetstream

[jetstream]

@Nikodemuzzhttps://www.baader-planetarium.com/en/blog/apochromatic-triplet-objective-why-oil-spaced-lenses/

"Oil-spaced lenses by TEC, Astro Physics and Baader:

• do not have to be protected from leaking oil. Horizontal storage is no problem, either. You only have to avoid temperature shocks. Never carry such an expensive instrument from the freezing cold outside at eg. -25°C into your cozy living room – this would mean a temperature difference of 50°C in a couple of minutes! But temperature differences of 25°C didn't cause any problems in tests over long periods of time. We are using a cool chamber in our production facilities to test dome parts, motors, circuit boards – and even lenses – at a temperature of -86°C to reliability of operation and perfect function under extreme conditions. Oil leakage is one of the few problems which can rarely affect lenses by Zeiss, Astro-Physics, TEC or by us – but only if they were mistreated. Here at Baader Planetarium, we have experienced opticians who have completed a multi-year training at Carl Zeiss Jena. We repair such oil leakages of lenses by Astro Physics/TEC and Zeiss since more than 20 years – quick and easy. So we think that the advantages of oil-spaced"

[Adam J]

If I had that kind of money it would be the TSA-120 for sure. 

Adam 

[Deadlake]

2 hours ago, jetstream said:

@Nikodemuzzhttps://www.baader-planetarium.com/en/blog/apochromatic-triplet-objective-why-oil-spaced-lenses/

"Oil-spaced lenses by TEC, Astro Physics and Baader:

• do not have to be protected from leaking oil. Horizontal storage is no problem, either. You only have to avoid temperature shocks. Never carry such an expensive instrument from the freezing cold outside at eg. -25°C into your cozy living room – this would mean a temperature difference of 50°C in a couple of minutes! But temperature differences of 25°C didn't cause any problems in tests over long periods of time. We are using a cool chamber in our production facilities to test dome parts, motors, circuit boards – and even lenses – at a temperature of -86°C to reliability of operation and perfect function under extreme conditions. Oil leakage is one of the few problems which can rarely affect lenses by Zeiss, Astro-Physics, TEC or by us – but only if they were mistreated. Here at Baader Planetarium, we have experienced opticians who have completed a multi-year training at Carl Zeiss Jena. We repair such oil leakages of lenses by Astro Physics/TEC and Zeiss since more than 20 years – quick and easy. So we think that the advantages of oil-spaced"

Out of interest whats your view on Petzval's and temperature. They have four lenses that need to adjust, so I would imagine harder to engineer and test. Any experience with them up near the Artic circle??? 😄

Glad I didn't get an oil filled triplet.

Edited February 9, 2021 by Deadlake

[jetstream]

6 minutes ago, Deadlake said:

Out of interest whats your view on Petzval's and temperature. They have four lenses that need to adjust, so I would imagine harder to engineer and test. Any experience with them up near the Artic circle??? 😄

Glad I didn't get an oil filled triplet.

No idea about Petzvals but I did look at Televues 101, 127. Just so many scopes out there...

I think with modern coatings the air spaced triplets rival the oil spaced but no doubt this could spark debate. check out Astro Physics site  under support for grat info including thermal shock.

Ok now I want a Petzval lol!

actually I'm looking at NV specs now too... there a CDN company I wonder if its good GSCI

[John]

The TAL Apolar 125 is the one that I really would not want to try and collimate. 6 elements in 3 groups !:

Edited February 9, 2021 by John

[Deadlake]

5 minutes ago, jetstream said:

No idea about Petzvals but I did look at Televues 101, 127. Just so many scopes out there...

I think with modern coatings the air spaced triplets rival the oil spaced but no doubt this could spark debate. check out Astro Physics site  under support for grat info including thermal shock.

Ok now I want a Petzval lol!

actually I'm looking at NV specs now too... there a CDN company I wonder if its good GSCI

if you read the CN thread I had on 130 mm APO for night vision, the conclusion was that Petzval are not needed for NV. I.e. the centre of the view is more important than the edge. I was getting hung up on that and told it's not really the case. You TSA120 is meant to be really good for NV... At the same time it's murky, the NP101 didn't do so well for NV, was the report on the thread.

Edited February 9, 2021 by Deadlake

[jetstream]

@Deadlake thanks, perfect.

I'm at the point now where I'm just going to use what I have scope wise but plan for imaging as well. i called about getting the TV adapters here- zero idea when i can get them. I could get the NV shortly. I want to make sure though to avoid a costly mistake.

The TSA120 will be used for lunar imaging, visual and NV. Sure glad I got it. I'm also sure your gonna love that APM LZOS.

[Nikodemuzz]

3 hours ago, jetstream said:

@Nikodemuzzhttps://www.baader-planetarium.com/en/blog/apochromatic-triplet-objective-why-oil-spaced-lenses/

"Oil-spaced lenses by TEC, Astro Physics and Baader:

• do not have to be protected from leaking oil. Horizontal storage is no problem, either. You only have to avoid temperature shocks. Never carry such an expensive instrument from the freezing cold outside at eg. -25°C into your cozy living room – this would mean a temperature difference of 50°C in a couple of minutes! But temperature differences of 25°C didn't cause any problems in tests over long periods of time. We are using a cool chamber in our production facilities to test dome parts, motors, circuit boards – and even lenses – at a temperature of -86°C to reliability of operation and perfect function under extreme conditions. Oil leakage is one of the few problems which can rarely affect lenses by Zeiss, Astro-Physics, TEC or by us – but only if they were mistreated. Here at Baader Planetarium, we have experienced opticians who have completed a multi-year training at Carl Zeiss Jena. We repair such oil leakages of lenses by Astro Physics/TEC and Zeiss since more than 20 years – quick and easy. So we think that the advantages of oil-spaced"

Thanks for the link, very interesting! I can easily see scenarios where a thermal shock might be hard to avoid. I wouldn't want to ruin an expensive telescope because leaving it outside after a session is not an option. This might become a deciding factor if the risk of damage is significant.

1 hour ago, Adam J said:

If I had that kind of money it would be the TSA-120 for sure. 

Adam 

Thanks for the input, Adam! It would be interesting to know in a bit more detail why the TSA-120 would be your choice!

[Adam J]

55 minutes ago, Nikodemuzz said:

Thanks for the link, very interesting! I can easily see scenarios where a thermal shock might be hard to avoid. I wouldn't want to ruin an expensive telescope because leaving it outside after a session is not an option. This might become a deciding factor if the risk of damage is significant.

Thanks for the input, Adam! It would be interesting to know in a bit more detail why the TSA-120 would be your choice!

Build quality and consistency of the optics. There is just a lovely sold feel to their stuff. I own a Esprit and the optics are great but as most are. But I still feel like later in life I will want to upgrade the esprit as good as it is has a mass produced feel to it while the TSA feels premium. I would say that a 120mm is optimal for me in terms of weight to performance in a refractor...maybe 130 Burt certainly no more than that. 

[jetstream]

Once @vlaiv has the optics test program built maybe we'll run some test to see whats what.

[Captain Scarlet]

There is a TMB 130 in the for sale section at the moment...

[jetstream]

I really want to see how all these refractors compare.

and the diagonals 😀

[John]

10 minutes ago, Captain Magenta said:

There is a TMB 130 in the for sale section at the moment...

If I did not already have a TMB/LZOS 130mm I would have been onto that one 😀

I have got away with two 4 inch refractors but I suspect my other half will not see why two 5.1 inchers are "essential"

Edited February 9, 2021 by John