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  #1  
Old 21-01-2021, 08:58 PM
Martin Pugh
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SharpStar 121SDQ Quintuplet f5.6

Hi there.

I have a loan of the subject telescope from Testar.

Got things reasonably dialled in, although the mount needs additional work.

Ok, its only M42/NGC 1977 but it's also only 5 x 5 min subs.

https://www.martinpughastrophotography.space/m42ngc1977

Taken with a One Shot Colour camera (not a QHY, hint). Antlia filters (jury still out).

As for the scope: What I like:
Very nice optics
Built in camera rotator.
Solid R&P focuser - Controlled by a Prima Luce Sesto Senso2

What I am not sure about.
There is a single thumbscrew that holds the drawtube in place. Its not such much as a lock as it bears down on sort of delrin shim, so it acts like a clutch. You have to find the sweet spot with this. If you leave it too loose, the focuser assembly and therefore your camera is also a bit loose so you will no doubt get some sag and image tilt. Too tight, and perhaps the electronic focuser may struggle to lift the camera package. That said, it didnt take much to find the sweet spot.

What I dont like:
Well, like EVERY other refractor made of aluminum, cool down is critical so focus changes quite a lot until it equalizes with ambient.

cheers
Martin
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  #2  
Old 21-01-2021, 09:10 PM
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Nikolas (Nik)
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$6000??? wow
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Old 21-01-2021, 09:11 PM
Martin Pugh
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Yep, but its quality glass.
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Old 22-01-2021, 08:38 AM
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That's really nice Martin - where are Sharpstar 'scopes made & does it have FPL-53 elements?
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Old 22-01-2021, 01:30 PM
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Quote:
Originally Posted by Andy01 View Post
That's really nice Martin - where are Sharpstar 'scopes made & does it have FPL-53 elements?



SharpStar uses ED glasses equivalent to the FPL53, same dispersion, same refraction index.



Let's clarify, I am quite certain that NO Chinese manufacturer uses the FPL53 glass by Ohara. In fact, if you check in their manuals or official websites, you cannot find "FPL53". You find this specification in the distributor websites so in case of a legal dispute, it will be hard to trace the origin.


SharpStar does not play this game and they just say the truth. The result from Martin are great and as you can see, there is no chromatic aberration.
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  #6  
Old 22-01-2021, 02:48 PM
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lazjen (Chris)
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Well, that's interesting. On the link that Glen gave, it lists: "Excellent FPL53 triplet lens (glass from Ohara, Japan)".

Adriano states: "...I am quite certain that NO Chinese manufacturer uses the FPL53 glass by Ohara"

What's incorrect -> Teleskop Express website listing, Glen's statement about the TS branded scopes or Adriano's statement?
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Old 22-01-2021, 02:58 PM
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lazjen (Chris)
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I could do that, Glen, but I'm far too lazy to do so right now.
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  #8  
Old 22-01-2021, 03:00 PM
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Quote:
Originally Posted by glend View Post
Sharpstar (The Brand) are manufactured by Kumming United Optics, who also make many of the Teleskop-express (TS) branded scopes. In fact you can find the 121SDQ model on the Teleskop-Express website. Details here:

https://www.teleskop-express.de/shop...field-Apo.html

I note that Teleskop-Express mention the glass is FPL53 from Japan, and they have a pretty solid reputation for truth in advertising. They also include a Spot diagram on the web pages related to this scope.

As a personal aside, having owned a couple of TS APO scopes, the TS130 is imho a much better buy, and significantly cheaper, with more flexibility as a platform. It is an f7 Triplet but can be easily reduced to f5,5 with that standard TS 3" reducer corrector, and you get 9mm more aperture.



I am sure that TS optics operates in good faith and they wrote what the manufacturer said.



The TS130 is a triplet, not a Petzeval quintuplet so you need to add a flattener. Also the TS optics is f/7 and not f/5.6.
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Old 22-01-2021, 03:24 PM
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I think one of the potential big plusses with that is being a Petzval, you don't have to fiddle with corrector spacing, only tilt.


I seriously thought about the TS 86mm Petzval before I bought my Stellarvue, but I could not find any images shot through one at the time.
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  #10  
Old 23-01-2021, 08:58 AM
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Quote:
Originally Posted by glend View Post
Don't

Obviously someone is missing the point I was trying to make.
The reduced TS130 becomes a f5,5, six element full frame flat field scope, with slightly more aperture than the 121SDQ, and is significantly cheaper (1500 euro cheaper for the combined TS130 and 3" reducer corrector). Numbers based on TS pricing.

. It can also be used at native f7, yes, and some buyers may want dual focal length capability.

The Quint is a nice scope, but over priced and with no flexibility in terms of configuration. My opinion sure, spend your money as you see fit.
that's a fair point of view, but there is a lot of appeal (to me at least) in a scope (like the 121sdq) that doesnt require specific precise spacing. Imaging time is short enough without wasting hours on getting spacing spot on. I dont have the 121sdq but an Askar 400 that is a similar design and I love that aspect of it compared to my Espirit 100ed.
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  #11  
Old 23-01-2021, 11:24 AM
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I got a very interesting answer from Ohara: they said that all Chinese manufacturer don't use their S-FPL53 glass.

I want to highlight the fact that the FPL53 does not exist, the real designation from Ohara is S-FPL53 (check on their website).
If a shop will says that their telescope uses the FPL53 glass, this is controversial but being just a code, it is hard to argue.

If you will read that the telescope use a FPL53 glass by Ohara, that is most likely false. Probably many shops write that in good faith and they logically think that the glass is from Ohara but it is not like this.



Companies that use the S-FPL53 glass from Ohara are:
Zeiss, Leica, Thales Angenieux, Canon, Panasonic, Olympus
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  #12  
Old 23-01-2021, 11:42 AM
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Interesting, I could be wrong but according to this thread Takahashi use FPL-53 as well.
https://www.cloudynights.com/topic/4...lens-elements/
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Old 23-01-2021, 11:44 AM
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That sounds unlikely. There is a plethora of cheaper refractors with air spaced FPL53 triplets on the market.

A lot of them seem to be getting Japanese Ioptron (Canon) made lenses and perhaps the bodies are made in China. So perhaps its true OHara doesn't sell to China and yet it could still be FPL53 glass as they buy lenses from Canon.

Then there is the FCD100 glass which I think is Chinese. So if the lenses are made in China then its most likely FCD100? or FPL51 or some lesser grade glass from OHara?

The term SD glass implies a lesser ED glass rating like it does in camera lenses. The term ED glass gets bandied around as a marketing term so it tends to lose meaning and differentiation.

If it were a true FPL53 Petsval then it is good value as the FSQ130 with I think it was 3 FPL53 lenses was around AUD$22,000.

Greg.



Quote:
Originally Posted by Adox View Post
I got a very interesting answer from Ohara: they said that all Chinese manufacturer don't use their S-FPL53 glass.

I want to highlight the fact that the FPL53 does not exist, the real designation from Ohara is S-FPL53 (check on their website).
If a shop will says that their telescope uses the FPL53 glass, this is controversial but being just a code, it is hard to argue.

If you will read that the telescope use a FPL53 glass by Ohara, that is most likely false. Probably many shops write that in good faith and they logically think that the glass is from Ohara but it is not like this.



Companies that use the S-FPL53 glass from Ohara are:
Zeiss, Leica, Thales Angenieux, Canon, Panasonic, Olympus
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Old 23-01-2021, 12:11 PM
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I am quite certain that Takahashi uses the S-FPL53


The FCD100 is from Hoya that is not a Chinese company: https://www.hoya.co.jp/english/index.html


Long story short, it is not important the alleged glass used in these Chinese telescope but their performance.
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  #15  
Old 25-01-2021, 10:52 AM
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I don't think that it is safe to say that because companies advertise "FPL-53" and not "S-FPL-53" the glass is not the real thing. My own Stellarvue advertise FPL53 (And who would go to the bother of extensive hand figuring of cheaper alternative glass to sell in quite expensive "Premium" refractors that people are bound to performance test?) and a quick search took me to a page on an Explore Scientific scope advertising an "Ohara FPL-53" element with a direct link to the S-FPL-53 spec PDF on the Ohara website.


You would probably be wary of a Chinese made scope at a very competitive price that just says "ED" glass though.
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Old 25-01-2021, 02:24 PM
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There are lots of scope makers who are using FPL53. Some high end ones use FPL55 like CFF.

AstroPhysics, Takahashi, TEC, Wiliam Optics, Stellarvue, CFF for starters.

TEC have swung away from FPL53 in recent years and now only offer Fluorite.

Greg.
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Old 25-01-2021, 06:24 PM
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Quote:
Originally Posted by The_bluester View Post
I don't think that it is safe to say that because companies advertise "FPL-53" and not "S-FPL-53" the glass is not the real thing. My own Stellarvue advertise FPL53 (And who would go to the bother of extensive hand figuring of cheaper alternative glass to sell in quite expensive "Premium" refractors that people are bound to performance test?) and a quick search took me to a page on an Explore Scientific scope advertising an "Ohara FPL-53" element with a direct link to the S-FPL-53 spec PDF on the Ohara website.


You would probably be wary of a Chinese made scope at a very competitive price that just says "ED" glass though.
But have a read on the Stellarvue site about optics and you will read Vic's story how they are experimenting with other glasses and that they feel a number are equivalent to fpl53 (for aperture 130 and less) and they will be gradually moving to fcd100... starting with their svx130t... they have stocks of fpl53 they will use up and use that for larger lenses until Vic is confident it is equivalent. The core of the argument is that the strehl is more important than the glass type.
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Old 25-01-2021, 06:30 PM
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Quote:
Originally Posted by Robert_T View Post
But have a read on the Stellarvue site about optics and you will read Vic's story how they are experimenting with other glasses and that they feel a number are equivalent to fpl53 (for aperture 130 and less) and they will be gradually moving to fcd100... starting with their svx130t... they have stocks of fpl53 they will use up and use that for larger lenses until Vic is confident it is equivalent. The core of the argument is that the strehl is more important than the glass type.
The pairing glasses is also vital per Roland Christen.
One major problem these scope makers have with O'Hara is defects in the glass that come up in the handling and cause them to be rejected with no refunds from O'Hara. Also they can have difficulty in getting the glass they need in the size they want free from defects. It makes it hard for them.
That's why sometimes some sized scopes are discontinued due to supply issues.

Agema sells doublets that are supposed to be better performing than triplets.
These new APM Lanthanum and ED glass doublets review well.
So anything is possible.
Greg.

Last edited by gregbradley; 08-02-2021 at 06:47 AM.
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Old 25-01-2021, 08:04 PM
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Quote:
Originally Posted by Robert_T View Post
But have a read on the Stellarvue site about optics and you will read Vic's story how they are experimenting with other glasses and that they feel a number are equivalent to fpl53 (for aperture 130 and less) and they will be gradually moving to fcd100... starting with their svx130t... they have stocks of fpl53 they will use up and use that for larger lenses until Vic is confident it is equivalent. The core of the argument is that the strehl is more important than the glass type.
I suppose that is the crux of it isn't it. If it demonstrably, provably works, then what is the problem?

My point above was more that scope makers marketing "FPL-53" rather than S-FPL-53 is not really one I would necessarily take to mean they are not using the real thing.
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  #20  
Old 08-02-2021, 05:34 AM
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I hope this doesn't become another
'if it isn't FPL53 it's substandard & the death of a perfectly good instrument CN style", there's been far too much of that already on the aforesaid forum.
If a picture is worth a thousand words, the image speaks for itself, nicely done Martin . I think returning the 121SDQ to Adriano might be difficult .
I own its little brother, the 76EDPH & could not be happier with it. With regard to the FPL53 topic, I'm not a bit surprised manufacturers & retailers are stepping back from the wholesale use of the term in favour of "ED glass" to describe their optics.
O'Hara has some healthy competition & manufacturers are likely keeping their options open in this competitive market & at the same time leaving the door open for other developing ED glass types & combinations of ED glass
(as Greg mentioned above) to gain a similar status to that of FPL53. Perhaps even O'Hara themselves would prefer their newer developments weren't overshadowed by their own legendary FPL53. Just my 2 bobs worth..
I can can vouch for SharpStar's commitment to quality & also Adrianos' knowledge in the field of optics. Sorry for the lengthy post, I'll go now...
Clear skies,
Tony
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