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Tecnosky 125/975 F7.8 FPL-53 Doublet APO - First Look


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The truth is that I have very little experience with refractors, to say nothing. For more than 25 years all my tubes have been reflectors, from the first 114 mm to the last 16 ". Last night, observing Sirius at 75X with my new TS Photo Line 125 SD refractor there was one aspect that caught my attention, and it was that the focused star flashed around, I don't know how to explain it, it was impossible to make it completely punctual, and the higher the magnification used, the more remarkable the effect. The night was stable, and the tube had more than an hour of acclimatization with very little variation of room temperature. Later the Moon, in binocular vision, already 140X was simply sublime. Comment that for monocular vision I use a diagonal mirror 2” Baader Click Lock. In extra focus I do not observe decollimation of the optics, nor a trace of punctured optics, at least as far as my knowledge goes. Perfectly concentric circles. What do you tell me about this?
 

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Tecnosky 125/975 F7.8 FPL-53 ED Doublet APO Refractor Arrived this morning from Astrograph. 👍🏻 First impressions are it’s a very solid and well made scope. Finish is a WO like pebble finish

Tecnosky 125 and friend. 🙂 The 125 and CC8” should make a nice pair. 👍🏻 And the Lacerta wedge for white light solar. 🙂

So much for the clear skies. Lots of cloud around earlier but now just very hazy so not much to look at except for the moon. Had chance to try a variety of eyepiecehs and a Baader prism and a WO diago

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The flashing of Sirius can be due to atmospheric turbulence, or residual heat inside the refractor tube. Sirius will rarely ever appear stable because of its low angle. 

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It was bad seeing for sure. What made me wonder were the website Meteoblue seeing forecasts for my area. I do not understand how they give a forecast with a green value of 5/5, with a Jetstream greater than 30m / s, which is precisely the opposite indicator. Hence the twinkle of Sirius.

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On 25/03/2021 at 21:13, Acrab67 said:

It was bad seeing for sure. What made me wonder were the website Meteoblue seeing forecasts for my area. I do not understand how they give a forecast with a green value of 5/5, with a Jetstream greater than 30m / s, which is precisely the opposite indicator. Hence the twinkle of Sirius.

Yes, Meteoblue, which I use a lot as well, is sometimes hard to interpret. However it is important to know that the presented measures at Meteoblue are not all summed up in the seeing index numbers, which you refer to with 5/5. Have a look at the explanation on their website:

https://content.meteoblue.com/en/spatial-dimensions/air/astronomy-seeing

Basically the two seeing index numbers are based on two atmospheric models and an integration through the turbulent layers to estimate visibility through theses turbulent layers. They are not connected to the jetstream estimation, which is a different measure.

In a nutshell, all measures at meteoblue have to be "good" to indicate a really good night: all three seeing measures, the jetstream and the bad layers as well....

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Posted (edited)

Not brand new. More expensive than the similar TS version though. Not sure what if any difference there is.

Edited by johninderby
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32 minutes ago, johninderby said:

I was thinking this one, given the price and certificate:

https://www.teleskop-express.de/shop/product_info.php/info/p12851_TS-Optics-CF-APO-130-mm-f-7-FPL55-Triplet-APO-Refractor-with-Certificate.html

I'd imagine getting to a certain Strehl costs time..

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I thought FPL55 was supposed to be more friendly to figure and polish, so theoretically it should be easier to achieve the desired min strehl than the FPL53 counterpart. Maybe the new 55 model has other improvements to warrant a £500 price increase.

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6 minutes ago, KP82 said:

I thought FPL55 was supposed to be more friendly to figure and polish, so theoretically it should be easier to achieve the desired min strehl than the FPL53 counterpart. Maybe the new 55 model has other improvements to warrant a £500 price increase.

If there are comparing it to LZOS then the figuring is pushing up the price. Cannot see any other way there can justify the cost. I've not seen a review of any of these scopes.

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Read a review comparing the earlier TS 90 FPL53 triplet and the new FPL55 TS CF triplet and they concluded that they were equivalent but did say they were excellent optically though.  

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9 minutes ago, Deadlake said:

If there are comparing it to LZOS then the figuring is pushing up the price. Cannot see any other way there can justify the cost. I've not seen a review of any of these scopes.

I think you're right. They are probably trying to copy the marketing strategy of Stellavue and LZOS by offering minimum strehl. If they could fit these well figured lenses in a full steel lens cell like LZOS, then that £500 increase is certainly worth it.

Edited by KP82
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1 minute ago, johninderby said:

So similar strehl to the Tecnosky then.

Question is can they be collimated? That's how a dealer can push the performance, or so Rupert told me in the case of the 125 mm Tecnosky doublet.

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3 hours ago, johninderby said:

Read a review comparing the earlier TS 90 FPL53 triplet and the new FPL55 TS CF triplet and they concluded that they were equivalent but did say they were excellent optically though.  

Owning the TS 90 FPL53 triplet myself, I'd be interested in reading that review.  Do you have a link to it that you could share here?  My only complaint is acclimation time for the triplet.

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On 16/04/2021 at 18:47, Deadlake said:

Question is can they be collimated? That's how a dealer can push the performance, or so Rupert told me in the case of the 125 mm Tecnosky doublet.

The FPL53 triplet version of TS (and Tecnosky) has a temperature compensated lens cell which can be fully collimated:

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p7717_TS-Optics-PHOTOLINE-130-mm-f-7-FPL53-Triplet-Apo---3-7--Auszug.html

as does the FPL53 doublet I have:

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p10133_TS-Optics-Doublet-SD-APO-125mm-f-7-8---FPL-53---Lanthan-objective.html

The dealer I got mine from (not TS directly) told me that these TS scopes are easy to collimate and he prefers the collimation mechanism of the TS (and Tecnosky) over ES for example....

Also the new FPL55 triplet is fully adjustable:

https://www.teleskop-express.de/shop/product_info.php/info/p12851_TS-Optics-CF-APO-130-mm-f-7-FPL55-Triplet-APO-Refractor-with-Certificate.html

So collimation should not be a problem on any of those.

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13 minutes ago, alex_stars said:

The FPL53 triplet version of TS (and Tecnosky) has a temperature compensated lens cell which can be fully collimated:

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p7717_TS-Optics-PHOTOLINE-130-mm-f-7-FPL53-Triplet-Apo---3-7--Auszug.html

as does the FPL53 doublet I have:

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p10133_TS-Optics-Doublet-SD-APO-125mm-f-7-8---FPL-53---Lanthan-objective.html

The dealer I got mine from (not TS directly) told me that these TS scopes are easy to collimate and he prefers the collimation mechanism of the TS (and Tecnosky) over ES for example....

Also the new FPL55 triplet is fully adjustable:

https://www.teleskop-express.de/shop/product_info.php/info/p12851_TS-Optics-CF-APO-130-mm-f-7-FPL55-Triplet-APO-Refractor-with-Certificate.html

So collimation should not be a problem on any of those.

If these scope where as fast as F6 I'd give them a look, shame they are not. A reducer does not work for my use case.

I do look forward to the reviews for the Triplets as I suspect they will start to get close to the premium makes. 

Also the difference between FPL55 and FPL53, if figuring the FPL55 maybe we will see that, interesting...

Edited by Deadlake
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