152/1216 fpl-51

[Robindonne]

Is anyone familiar with this telescope in combination with AP.   
Its a 152/1216 triplet, probably brought out with multiple names  

The whole covid price increase thing changed my mind a bit.  Not that its dramatic but while still searching for something new, i put the idea of saving for an esprit on hold.

it will be my first triplet, but the scope from the link is an fpl-51. Im not sure how big of a deal when used in a triplet, so i’d better ask among users if this telescope is more “colorful” than a much more preferred fpl-53 combi.  
 

https://www.tecnosky.eu/index.php/tecnosky-apo-152-1216-lanthanum.html

Edited February 12, 2021 by Robindonne

[Adam J]

3 hours ago, Robindonne said:

Is anyone familiar with this telescope in combination with AP.   
Its a 152/1216 triplet, probably brought out with multiple names  

The whole covid price increase thing changed my mind a bit.  Not that its dramatic but while still searching for something new, i put the idea of saving for an esprit on hold.

it will be my first triplet, but the scope from the link is an fpl-51. Im not sure how big of a deal when used in a triplet, so i’d better ask among users if this telescope is more “colorful” than a much more preferred fpl-53 combi.  
 

https://www.tecnosky.eu/index.php/tecnosky-apo-152-1216-lanthanum.html

I dont know that scope exactly but in my experiance anything that uses FPL-51 as a little bit of blue bloat. Not an amount that is unmanagable in imaging my any means and probably an not so apparent visually. I have a scope with one of the cheaper ED glasses in it and it is corrected through use of a mild Astronomik L-3 filter for AP use.

Generally as aperture increases and F-ratio decreases colour correction is harder but its a non linear relationship and other factors are involved too. The lanthanum doped / coated element will act as a mild - violet filter and so should help in this regard. So the theory would be that a 6 inch FPL-51 triplet will not be perfectly corrected and but that CA will not be very in your face either.

If no one has the scope perhapse that will give you something to think about.

Adam

[Robindonne]

Hmm thanks for the explanation.   I know its an never ending subject for questions.  Too bad manufacturers dont rate their systems.   Not by some fency detailed individual test but more like a percentage of false color for that particular glass configuration.

Ok to be short.  That linked 152mm is not the scope to be forever happy with.  
Only own an 120mm, a doublet, and this doesn’t seems like an overall step up.  
 

Thank you very much for the info/warning. 

[Deadlake]

If AP wouldn’t you want a faster scope, say less then F6 and with a larger imaging size to illuminate the sensor?

The aperture may not increase however obviously time of capture would decrease, which seems a step up.

Above 130 mm usually into mirror based Astrographs.

 

 

[KP82]

You will need a helluva mount to do imaging with a 6" f/8 triplet, something like an EQ8 minimum.

With regards to false colours in a FPL51 triplet, I've looked through an Altair 115 f/7 (FPL51 triplet made by KUO, there are many other rebrands of the same scope) before at a star party and couldn't see any false colours in it. However it's a lot more difficult to get a good figure in a 6" lens than a 4.5". If you could test it out personally, that would be great.

[Robindonne]

2 hours ago, Deadlake said:

If AP wouldn’t you want a faster scope

Oke so i have to look for a shorter/faster.  
yes mainly AP.  If it would be possible to combine it with now and then visual i would be twice as happy of course.  I might have the option for a reducer?

 

38 minutes ago, KP82 said:

You will need a helluva mount

It should be carried by an orion atlas pro(skywatcher azeq6).  Yes testing isnt a good option for me. Not enough experience to rate a scope.  But i quess your and the previous advice here was the push i need to skip this model.  
An fpl-53 triplet.  
 

thx
 

Edited February 13, 2021 by Robindonne

[Deadlake]

41 minutes ago, Robindonne said:

Oke so i have to look for a shorter/faster.  
yes mainly AP.  If it would be possible to combine it with now and then visual i would be twice as happy of course.  I might have the option for a reducer?

I have a APM 130mm/ F6 on order. I choose the F6 for NV usage, however after doing some more research F6 is quite good for being used as a visual rich wide field scope. The only disadvantage for visual of a fast scope is magnification for planetary observing, however I have some high power EP's to get around that, you could also use a Barlow as well for this. 

I did see this when I was looking:

https://www.365astronomy.com/sharpstar-121sdq-121mm-f-5.6-quintuplet-apochromatic-refractor-telescope.html

its also here in the EU but more expensive:

https://www.teleskop-express.de/shop/product_info.php/info/p11518_TS-Optics-121SDQ-Apo-121-mm-f-5-6-Quintuplet-Flatfield-Apo.html

My reservation was would the vendor star test or bench test it and no reviews around. However great value for what it is. 

Edited February 13, 2021 by Deadlake

[Robindonne]

Hmm also nice item. Thx.   Plenty options actually.  Although its a quintuplet, it comes close to the esprit.  Size/price.  

42 minutes ago, Deadlake said:

I did see this when I was looking:

https://www.365astronomy.com/sharpstar-121sdq-121mm-f-5.6-quintuplet-apochromatic-refractor-telescope.html

 

[Louis D]

This diagram from telescope-optics.net gives some idea of the color correction of various glass combinations.

Seemingly, an FPL-51 triplet will perform similarly to an FPL-53 doublet at like aperture and f-ratio.

This question has been discussed repeatedly over the years on both SGL and CN.  Google "fpl-53 doublet vs fpl-51 triplet" for hours of reading.

[Adam J]

7 hours ago, KP82 said:

You will need a helluva mount to do imaging with a 6" f/8 triplet, something like an EQ8 minimum.

With regards to false colours in a FPL51 triplet, I've looked through an Altair 115 f/7 (FPL51 triplet made by KUO, there are many other rebrands of the same scope) before at a star party and couldn't see any false colours in it. However it's a lot more difficult to get a good figure in a 6" lens than a 4.5". If you could test it out personally, that would be great.

The camera is more sensitive to blue and red than the human eye and hence in AP you will see CA that you cant see by looking through the scope.

This being said the 115 F7 is a excerlent example of a well optomized FPL 51 design and I have seen many great AP images with it.

Adam

[Louis D]

5 hours ago, Adam J said:

The camera is more sensitive to blue and red than the human eye and hence in AP you will see CA that you cant see by looking through the scope.

This being said the 115 F7 is a excerlent example of a well optomized FPL 51 design and I have seen many great AP images with it.

Adam

I'd totally believe that.  I wonder if a fluorite doublet outperforms an FPL-53 triplet.  Based on the cost, you'd think it would.

[Adam J]

1 hour ago, Louis D said:

I'd totally believe that.  I wonder if a fluorite doublet outperforms an FPL-53 triplet.  Based on the cost, you'd think it would.

I would not think so, fluorite is not that much better than FPL53 and worse in some ways. More likely it would be on par with a FPL 51 triplet.

Adam

[dweller25]

7 hours ago, Adam J said:

I would not think so, fluorite is not that much better than FPL53 and worse in some ways. More likely it would be on par with a FPL 51 triplet.

Adam

 Hello @AdamJ never heard that before.

 In what ways is fluorite worse than FPL53 ?

Edited February 14, 2021 by dweller25

[mikeDnight]

A friend of mine bought a Meade 127 triplet that I'm pretty sure used FPL51. This was quite some time ago and I hate anything with the Meade label on it. Honestly, that scope was as colour free  (visually) as any apo I've ever used. I suspect the Tecnosky 152 triplet will be as good if not better as a visual scope. When mated with the right elements a FPL53 triplet can be a beautiful apo.   

[Robindonne]

23 minutes ago, mikeDnight said:

A friend of mine bought a Meade 127 triplet that I'm pretty sure used FPL51. This was quite some time ago and I hate anything with the Meade label on it. Honestly, that scope was as colour free  (visually) as any apo I've ever used. I suspect the Tecnosky 152 triplet will be as good if not better as a visual scope. When mated with the right elements a FPL53 triplet can be a beautiful apo.   

Yes but the technosky is a fpl51. I think its a good scope for visual use.  
Im afraid for saving and spending (on a scope for mostly Photography) and ending up selling it. 

 

[Robindonne]

1 hour ago, dweller25 said:

 In what ways is fluorite worse than FPL53 ?

Walletwise

[Robindonne]

19 hours ago, Louis D said:

Seemingly, an FPL-51 triplet will perform similarly to an FPL-53 doublet at like aperture and f-ratio.

What a helpful link and diagram. 
im sure there are much more factors to rate a certain lens combination, but this is very helpful.  Thx.

Edited February 14, 2021 by Robindonne

[dweller25]

@Robindonne

This FPL53 doublet looks interesting.... less money than the FPL51 triplet and according to the above graph almost the same performance, lighter too 🙂

https://www.teleskop-express.de/shop/product_info.php/info/p12046_TS-Optics-Photoline-150-mm-f-8-FPL53-Lanthan-Dublet-Apo---2-5--Focuser.html

Edited February 14, 2021 by dweller25

[dweller25]

@Robindonne

Another thought - have you thought about a used Takahashi TSA120, a superb triplet and much easier to carry and mount than a 6” F/8.

Edited February 14, 2021 by dweller25

[John]

2 hours ago, mikeDnight said:

A friend of mine bought a Meade 127 triplet that I'm pretty sure used FPL51. This was quite some time ago and I hate anything with the Meade label on it. Honestly, that scope was as colour free  (visually) as any apo I've ever used....

I think they might vary a bit Mike. I used one which showed a touch more CA than my ED120 doublet did.

I think this comparison involves a similar scope:

https://astromart.com/reviews-and-articles/reviews/telescopes/refractors/show/orion-120ed-vs-astro-tech-127edt

 

 

Edited February 14, 2021 by John

[KP82]

11 hours ago, Louis D said:

I'd totally believe that.  I wonder if a fluorite doublet outperforms an FPL-53 triplet.  Based on the cost, you'd think it would.

I doubt it. This is the same as implying FC100DZ beats both TSA102 and TSA120. But it's not the case in reality.

[Adam J]

3 hours ago, dweller25 said:

 Hello @AdamJ never heard that before.

 In what ways is fluorite worse than FPL53 ?

It's brittle harder to polish and less inert (doesn't like water). 

[Robindonne]

59 minutes ago, dweller25 said:

@Robindonne

Another thought - have you thought about a used Takahashi TSA120, a superb triplet and much easier to carry and mount than a 6” F/8.

Of course.  If one comes for sale and is in very good shape, i would be very interested.  Cant think of a better buy/investment than a used tak.  

[dweller25]

15 minutes ago, Robindonne said:

Of course.  If one comes for sale and is in very good shape, i would be very interested.  Cant think of a better buy/investment than a used tak.  

I know someone who has too many Taks, but has put a handle on the only one he uses - maybe he will sell his TSA120 cheap .... 😂😂

Edited February 14, 2021 by dweller25

[mikeDnight]

12 hours ago, Louis D said:

I'd totally believe that.  I wonder if a fluorite doublet outperforms an FPL-53 triplet.  Based on the cost, you'd think it would.

It would depend on who made the fluorite doublet and FPL53 triplet.  Merely being made of fluorite or FPL53, doublet or triplet is no guarantee of performance.  And there's much more to a scope than colour correction. If the over all optical figure is high, then that's the scope that will perform best, even if its an achromat.