Test and Comparison: Starfield 102mm F7 ED Doublet v Takahashi FC-100 DF f7.4 Doublet (Fluorite)

[jetstream]

1 hour ago, Franklin said:

right up to battle hardened observers who spend most of their lives and most of their money worshipping glass😁.

For sure!

It truly amazes me what the 130mm F5 , $350 Heritage 130 shows with a pocketful of Circle T othos. If a person cant get great views with one of these an examination of why might be in order.IMHO.

[jetstream]

11 minutes ago, Mr Spock said:

That leads nicely into the topic at hand. As well as poor MTF, other aberrations can restrict detail and apparent contrast, such as the afore mentioned spherical aberration.

I wonder if a sag in the MTF curve can affect the angular resolution with respect to aperture and how we see it through a scope? I'm very interested in hearing peoples lunar/planetary reports with respect to spacial frequency, contrast and angular resolution, in any and all telescopes.

[josefk]

12 minutes ago, Mr Spock said:

Without following the can of worms some older Nikkors had poor correction for spherical aberration, like the 35mm f1.4. Use that wide open and you get a dreamy image 

That leads nicely into the topic at hand. As well as poor MTF, other aberrations can restrict detail and apparent contrast, such as the afore mentioned spherical aberration. Correction of all those aberrations is what you are paying a lot of money for 

and without being too philosophical about it the sum affect of these corrections (IMHO) may be more and more difficult to see positively (i don't know) but their absence on the other hand is profoundly difficult to unsee or see through if you care, if your expectations are elevated, and/or if your highly invested one way or another (this i do know).

[ukskies]

Wonderful drawings @mikeDnight thanks for sharing. The detail you sketch is amazing, I wish I could draw detail like that.

[ukskies]

22 hours ago, 900SL said:

I've noticed this across several hobbies or activities that require 'equipment', like bicycling for example, or luxury watches. I suspect the explanation is deep rooted in the male psyche, and connected with the dog pack. 

Aside from the obvious, namely in this case a well made product with a long tradition of optical excellence, and healthy residuals, there is the darker side of the psyche at work here. 

Kudos by association, or ownership. Peer reinforcement. The contemptible phrase 'Premium brand', with everything that includes. Tribal membership. Prestige. Self worth. Snobbery and look-at-me.

I say this as a Rolex owner and a former Yorkshireman. Luckily I am now enlightened as to the ways of the world 😂

I do keep looking at the TSA 120 though. Then I look at how much you get spade handled for accessories and go back to the alternatives..

Maybe I just need some counselling by Jeremy 😉

 

     

 

 

When I was a young boy and through my teen years my Mother always bought the best and taught me the value of doing so. The old "buy cheap buy twice" phrase became ingrained in me.

As a boy "cheap" was anything with made in Japan (yes Japan not a typo) labelled on it. I remember the old metal toys from Japan with thin cheap metal and often sharp edges that would cut your hands. Japan though soon began to produce high quality cameras, good enough to rival the German stuff that dominated the market in those days and you could be confident that Japanese glass was in the top tier as regards quality. I've seen the Chinese glass go from OK to extremely good and the early cheap focusers have also now become very precise and a pleasure to own, things keep progressing.

I believe nowadays the "buy cheap buy twice" phrase has much less importance and some of the less expensive stuff is indeed extremely worthy.

That said I once saw and looked through a Takahashi many years ago and it's cost was way beyond my reach at that time but I promised myself that one day I would get myself one and once I reached retirement age I decided I could it was time.

[ukskies]

21 hours ago, FLO said:

I (speaking personally, not as FLO) have noticed the same. I think it is because their design and manufacture remind me telescopes are scientific instruments. For me, many telescopes sold today, with their shiny CNC-machined, colour-anodised hardware, are too pretty. 

I don't currently own a Takahashi. Though I want to. I will most likely purchase one for my retirement (not yet!). It will be my last telescope. 

Steve

Mine was a retirement present even tho I still work part time, I'm not sure about this last telescope thing though. 😉

My advice would be not to wait Steve I wish I hadn't.

I

[paulastro]

1 hour ago, ukskies said:

Mine was a retirement present even tho I still work part time, I'm not sure about this last telescope thing though. 😉

My advice would be not to wait Steve I wish I hadn't.

I

I don't know what 'last telescope' means? 😉

[mikeDnight]

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Edited April 5, 2023 by mikeDnight

[Alan White]

1 hour ago, paulastro said:

I don't know what 'last telescope' means? 😉

Sadly none of us will until we have either 1. left the hobby for good (unlikley in my case) or 2. Died (certainty in all cases)

 

[neil phillips]

On 29/03/2023 at 20:31, cajen2 said:

There's always the lure of the exclusive high end..... it's how the likes of Linn, Naim and Rolls Royce still sell products...

Basically, bragging rights! 😆😆

I had a Linn. And it was a lot better than the Rega.  ( I had both ) Sonically. Not the lure of exclusivity. Now they are just silly prices and is truly in the realm of the exclusive high end

For those that have the spare dosh. Buy it and enjoy it. For everyone else those starfeilds sound good

On 30/03/2023 at 00:04, mikeDnight said:

 I had a 10" F6.3 and a 8" F6 stood in the cormer of my observatory for at least 18 months as you'll likely remember Paul. The thing is, I never really remember any spanking going on. The 10" was very good on planets and had an obvious resolution advantage, but using a Dob plays havoc with my lower back, so it definitely didn't get used anywhere near as often as it probably deserved. I do remember its gross diffraction spikes that smeared definition, especially with Venus. Awful!

 The 8" didn't spank the Tak on Mars. The comparison sketch of Mars below arguably shows a slight minor detail in the 8", but the reflector view wasn't nearly as clean or as easy to see as with the Tak. The cloud detail on Venus was easy in the Tak but not so easy in the larger reflectors (too much light)!  And the ultrafine rille detail within the crater Werner while visible everytime in the Tak, was never seen in the reflectors, (again I believe due to too much light blinding the fine definition).

 May be we need to  get our scopes side by side so you can see what you're missing. 

 

Well I am a lunar and planetary imager, so have a different viewpoint on spanking  

Edited March 31, 2023 by neil phillips

[Mr Spock]

I'm all Naim now having retired my Linn Karik. Naim NDX-2, NAC-72, Hi-Cap, NAP 250 - amps traditional olive of course  

[mikeDnight]

*

Edited April 5, 2023 by mikeDnight

[Greymouser]

Sorry for putting the cat among the pigeons, but I had the Starfield for a while and whilst it is without a doubt a great scope; compact; great build quality; absolutely no CA; sharp as a very sharp thing, I have to say my F13.2 cheap Achro, was just as sharp and could take much more magnification; also absolutely no CA. I got the Starfield to use with my AZGTi, but it was to much for it imo. I feel that a high F number beats much, if you are lucky with the draw, as it were. 

Here it is, with a mount, even cheaper than the Starfield: https://www.astroshop.eu/telescopes/bresser-telescope-ac-102-1350-messier-hexafoc-exos-2/p,57357

Or without a mount, which may be/ may be soon, out of production. https://www.teleskop-express.de/shop/product_info.php/info/p9739_Bresser-Refractor-Messier-AR-102L-1350---Optical-Tube-Assembly.html

I do believe quality varied somewhat, but doesn't it always? Mine is a great scope and is an easy fit with the SkyTee 2.

Edit: If too far off topic here mods, please remove.

Edited March 31, 2023 by Greymouser

[ukskies]

4 hours ago, paulastro said:

I don't know what 'last telescope' means? 😉

I thought it meant the last telescope you read a great review of and now want.  🤷‍♂️

[ukskies]

38 minutes ago, Greymouser said:

Sorry for putting the cat among the pigeons, but I had the Starfield for a while and whilst it is without a doubt a great scope; compact; great build quality; absolutely no CA; sharp as a very sharp thing, I have to say my F13.2 cheap Achro, was just as sharp and could take much more magnification; also absolutely no CA. I got the Starfield to use with my AZGTi, but it was to much for it imo. I feel that a high F number beats much, if you are lucky with the draw, as it were. 

Here it is, with a mount, even cheaper than the Starfield: https://www.astroshop.eu/telescopes/bresser-telescope-ac-102-1350-messier-hexafoc-exos-2/p,57357

Or without a mount, which may be/ may be soon, out of production. https://www.teleskop-express.de/shop/product_info.php/info/p9739_Bresser-Refractor-Messier-AR-102L-1350---Optical-Tube-Assembly.html

I do believe quality varied somewhat, but doesn't it always? Mine is a great scope and is an easy fit with the SkyTee 2.

Edit: If too far off topic here mods, please remove.

Now that's very interesting your saying Starfield Apo was extremely sharp yet wouldn't handle high magnification like your 102 Achro?

That brings me to a question of how we define sharpness and I believe this to be an individual thing affected by what and how we view and influenced by our own eyesight as well as atmospheric conditions.

To me for example, due to light polluted skies at home I am mainly a Lunar, planetary and double star observer and I'm visual only. Most of the stuff I do from home is at higher magnifications and often pushing or exceeding the "acceptable" limits of magnification for the instrument and mostly pushing the limits of our wonderful atmosphere. 

If I take my 100mm Tak to 200x mag I am at the acceptable maximum for a 100mm scope  and I do view in the 150X to 200X range a lot of the time. At this level I can pronounce my scope is very sharp . This however is where it begins rather than where it ends because on my last night of better seeing and a different diagonal (not sure which made the difference) I have taken the little Tak to over 333X on the moon and then on to just above 400X and the image was still just as sharp and contrasty. This little Tak will go to double and maybe more of the accepted limit for it's aperture and still maintain it's sharpness. This I would describe as "super sharp" as it is way above the accepted limit. Maybe in the future on a night of excellent seeing and with top quality eyepieces I may find out the scopes full capability but it has already proved it's an extremely sharp instrument capable of anything I would wish to do with it.

Please understand everyone this isn't me bragging about how great my scope is, I'm merely making a point about perceived sharpness from my own perspective.

Though I am speaking from my own experience I have also read many reports of exceptional optics on test by skilled and acknowledged observers exceeding the 50X per inch rule and getting to 100X per inch and beyond with no loss of sharpness. It isn't limited to refractors either, I once read an observing report by Rick Singmaster with a 14.5 inch Zambuto/ Singmaster that he and Carl took to stupidly high magnifications on one exceptional night.

So the question is then, what is "sharp"? 

[neil phillips]

2 hours ago, mikeDnight said:

An imagers view on "Spanking" could make an amusing, if not disturbing side thread in its own right. 

Lol wrong forum. 

[neil phillips]

1 hour ago, Greymouser said:

Sorry for putting the cat among the pigeons, but I had the Starfield for a while and whilst it is without a doubt a great scope; compact; great build quality; absolutely no CA; sharp as a very sharp thing, I have to say my F13.2 cheap Achro, was just as sharp and could take much more magnification; also absolutely no CA. I got the Starfield to use with my AZGTi, but it was to much for it imo. I feel that a high F number beats much, if you are lucky with the draw, as it were. 

Here it is, with a mount, even cheaper than the Starfield: https://www.astroshop.eu/telescopes/bresser-telescope-ac-102-1350-messier-hexafoc-exos-2/p,57357

Or without a mount, which may be/ may be soon, out of production. https://www.teleskop-express.de/shop/product_info.php/info/p9739_Bresser-Refractor-Messier-AR-102L-1350---Optical-Tube-Assembly.html

I do believe quality varied somewhat, but doesn't it always? Mine is a great scope and is an easy fit with the SkyTee 2.

Edit: If too far off topic here mods, please remove.

Funny that always wanted to try one. The virtues of longer focal length. On doublets. But your right. I had a small F13 optics were also pin sharp. And your also correct. lucky with the lottery that is mass produced. 

[jetstream]

13 minutes ago, ukskies said:

So the question is then, what is "sharp"? 

Great question. Very interested to hear opinions.

To me sharp means "sharply defined" ie a measure of visual definition and opposite to "soft" . Most optics have a magnification limit that once exceeded the visual image will lose definition and start to go "soft" . Of course this is all relative IMHO. It is very hard to rate telescopes without viewing them together and under excellent seeing.

17 minutes ago, ukskies said:

I once read an observing report by Rick Singmaster with a 14.5 inch Zambuto/ Singmaster that he and Carl took to stupidly high magnifications on one exceptional night.

The 15" I have with Ostahowski mirrors will take 760x with the 2.4 HR and Ive barlowed it over 900x... with no loss of definition. This is between 50x and 60x aperture in inches and is typical for a mirror of this size from a well known glass pusher. Lockwood is also at the top of his game, IMHO

Gerry

[neil phillips]

3 hours ago, Mr Spock said:

I'm all Naim now having retired my Linn Karik. Naim NDX-2, NAC-72, Hi-Cap, NAP 250 - amps traditional olive of course  

Lucky man. I am all low end now Marantz cd. Q acoustics. I have six of them though. ( home C ) 

[Mr Spock]

22 minutes ago, ukskies said:

So the question is then, what is "sharp"? 

There could be a definition of sharp should you choose to accept the laws of optics/physics. However, people prefer their own definition of sharp. As such it is impossible to know what people mean when they say sharp as only they can see what they are looking at and give their interpretation of what they see.

For this test at just below x300 I would describe both scopes as reasonably sharp and usable rather than bitingly sharp. Some will make excuses like it was the seeing etc. That's why I had the 12" Dob there too as it is a large aperture Newt which is susceptible to poor seeing. It was not. Compared to the two fracs at the same magnification it was bitingly¹ sharp, detailed and full of contrast, and by direct comparison both fracs looked soft - dialing back the magnification to x150 in the fracs gave a sharp image equivalent to the x300 of the 12"; more or less what the laws of optics tell you it should under ideal conditions. 4" is 4" regardless of the quality of the optics.

As I said, only the observer knows what they are seeing.

¹ We must be careful about using subjective terms as they too are open to interpretation 

[ukskies]

43 minutes ago, jetstream said:

Great question. Very interested to hear opinions.

To me sharp means "sharply defined" ie a measure of visual definition and opposite to "soft" . Most optics have a magnification limit that once exceeded the visual image will lose definition and start to go "soft" . Of course this is all relative IMHO. It is very hard to rate telescopes without viewing them together and under excellent seeing.

Gerry

To me two scopes of equal focal ratio, side by side a night of great seeing with the same eyepieces AND same eyes is required to "prove" which is sharpest. I also believe that during the test one will go soft at a given magnification and one will exceed this level by a margin.

I also believe that scopes could be the same make and model and this will still hold true in many cases, even seemingly identical high end instruments have sample variations.

43 minutes ago, jetstream said:

The 15" I have with Ostahowski mirrors will take 760x with the 2.4 HR and Ive barlowed it over 900x... with no loss of definition. This is between 50x and 60x aperture in inches and is typical for a mirror of this size from a well known glass pusher. Lockwood is also at the top of his game, IMHO

Gerry

That is extremely interesting and I would love to discuss this in more detail however I'm thinking I maybe should have started a new thread as we're veering off topic here now. 😬

Edited March 31, 2023 by ukskies

[ukskies]

25 minutes ago, Mr Spock said:

There could be a definition of sharp should you choose to accept the laws of optics/physics. However, people prefer their own definition of sharp. As such it is impossible to know what people mean when they say sharp as only they can see what they are looking at and give their interpretation of what they see.

For this test at just below x300 I would describe both scopes as reasonably sharp and usable rather than bitingly sharp. Some will make excuses like it was the seeing etc. That's why I had the 12" Dob there too as it is a large aperture Newt which is susceptible to poor seeing. It was not. Compared to the two fracs at the same magnification it was bitingly¹ sharp, detailed and full of contrast, and by direct comparison both fracs looked soft - dialing back the magnification to x150 in the fracs gave a sharp image equivalent to the x300 of the 12"; more or less what the laws of optics tell you it should under ideal conditions. 4" is 4" regardless of the quality of the optics.

As I said, only the observer knows what they are seeing.

¹ We must be careful about using subjective terms as they too are open to interpretation 

Thank you Michael, I'm in total agreement with you here. Sharpness, like beauty is in the eye of the beholder and limited by many other factors.

Edited March 31, 2023 by ukskies

[mikeDnight]

*

Edited April 5, 2023 by mikeDnight

[900SL]

Would it be correct to say that this is more a visual astronomy thing? 

[jetstream]

23 minutes ago, mikeDnight said:

My DZ has given beautifully sharp views of double stars at 500X, and remained surprisingly sharp at 1000X.

An excellent refractor, of any make, will run out of light before the limit of the optics is reached. IMHO. Your observations at very high mags confirm this, again just my opinion. Funny how we share the same observations on some things though. My TSA120 goes up there and runs out of light too, before the optics break down.