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S@N's FLT132 review???

ollypenrice

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ollypenrice

ollypenrice

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You ae reviewing a five inch refractor costing over TWO THOUSAND SEVEN HUNDRED POUNDS. It is an instrument clearly of interest primarily to imagers and you find it has 'some odd spiking artifacts around bright stars in long exposures' and you describe this as 'a minor quibble.' Not another word on the matter thereafter.

I can't see many FLTs being sold till we know a little more...

Olly.

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JohnWC

JohnWC

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Seems a pity to damn a fine telescope just because of one small phrase in one review.

It may have been just that particular scope for instance.

There are always going to be diffraction spikes I would have thought and this may have been what it was.

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Andrew*

Andrew*

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The article includes an image of the orion nebula, which reveals the artefact very clearly, and it's not just around bright stars, it's every star, and it's ugly.

I certainly wouldn't fork out that kind of money until I had been assured the reviewer got a lemon, or that he'd let a spider make a web on the front of the objective.

Speaking of the reviewer, don't know what he was thinking.;)

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Darth Takahashi

Darth Takahashi

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JohnWC,

How do you get diffraction spikes with a REFRACTOR? ;) I know how I would do it, with a post imaging script, otherwise I have to live without them.

Stars can grow more and more bloated with longer and longer exposures but they shouldn't produce diffraction spikes? To be honest, I haven't even read the review, hence the request for the link. However, I would not touch one of these FLT's with the proverbial barge pole!

There again I don't need to since I have a perfectly good TOA130F which doesn't produce diffraction spikes.

Neil.

Neil.

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Doc

Doc

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The article includes an image of the orion nebula, which reveals the artefact very clearly, and it's not just around bright stars, it's every star, and it's ugly.

I certainly wouldn't fork out that kind of money until I had been assured the reviewer got a lemon, or that he'd let a spider make a web on the front of the objective.

Speaking of the reviewer, don't know what he was thinking.;)

True but at £2700 you shouldn't be getting a lemon.

Think off the hassle trying to get it sorted with WO.

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FLO

FLO

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JohnWC,

How do you get diffraction spikes with a REFRACTOR? ;)

Metal tabs are often used to separate air-spaced lens elements and sometimes produce equally spaced diffraction spikes (one per spacer).

I can't remember what the FLT132 uses, I'll take a look later.

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ngc2403

ngc2403

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Metal tabs are often used to separate air-spaced lens elements and sometimes produce equally spaced diffraction spikes (one per spacer).

I can't remember what the FLT132 uses, I'll take a look later.

???? what? never heard that before i my short astronomy life!

please explain more details of the metal spacers and how they produce the diffraction spikes

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Darth Takahashi

Darth Takahashi

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Metal tabs are often used to separate air-spaced lens elements and sometimes produce equally spaced diffraction spikes (one per spacer).

I can't remember what the FLT132 uses, I'll take a look later.

I've had some nice Vixen telescopes with the same tabs that did not produce diffraction spikes? Not questioning your answer because it seems logical but what's the difference between the FLT132 lens cell tabs and those of lets say a 102ED Vixen?

I agree regarding the lemon statement, for this kind of money the telescopes should all be leaving the factory correctly collimated and optically tested.

Neil.

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jgs001

jgs001

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It was reviewed by Pete, he also says that the camera wouldn't reach focus without the use of the supplied diagonal or a non supplied extension tube, so it might be something in that area that caused the effects on the stars, I presume it's the spikes on the stars along the edge of the running man. Actually they, almost, look like diffraction spikes caused by the aperture blades in a camera lens.

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canuck

canuck

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I can't see many FLTs being sold till we know a little more...

Olly.

well...ahem...I can't see many serious imagers being influenced by a SatN review anyway. :rolleyes:

I have to say that I think their review concept lost credibility some time ago.;)

Richard

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FLO

FLO

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Metal tabs are often used to separate air-spaced lens elements and sometimes produce equally spaced diffraction spikes (one per spacer).

I can't remember what the FLT132 uses, I'll take a look later.

Yes, the FLT132 uses metal spacers which can produce corresponding diffraction spikes. There are a number of materials used to separate air-spaced elements and metal tabs are considered to be one of the best at preventing 'wedged' optics so several manufacturers, including big-name premium brands, use them. This doesn't apply to oil-spaced or cemented elements.

I've had some nice Vixen telescopes with the same tabs that did not produce diffraction spikes?
They don't always show and if the tabs are shielded by a baffle or similar then they won't show at all.
???? what? never heard that before i my short astronomy life!
That's what makes SGL such a great place to hang out ;)
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GazOC

GazOC

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well...ahem...I can't see many serious imagers being influenced by a SatN review anyway. :hello2:

I have to say that I think their review concept lost credibility some time ago.;)

Richard

Couldn't agree more.;) To say the reviews are "lightweight" would be being kind, everything tested gets over 85%...:rolleyes:

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Darth Takahashi

Darth Takahashi

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Not sure how productive some of these statements have become?

So serious imagers only use Takahashi telescopes! ;) Well this statement is about as useful as claiming serious imagers don't read or rate Sky@Night reviews... I'm sure every magazine that has to make such a comment makes certain they are correct first. It's too easy just to dismiss it out of hand.

Well I'm still happy, lots of nice baffles and no metal tabs to be seen

Neil.

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canuck

canuck

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Couldn't agree more.:rolleyes: To say the reviews are "lightweight" would be being kind, everything tested gets over 85%...;)

My favorite SatN moment was when the 6" Intes Maksutov was praised individually as being the best overall scope on test, but was too expensive to win. A few issues later, the Televue Ethos was named the best eyepiece.

Nothing like a bit of consistency:blob10:

Richard

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roundycat

roundycat

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here is the business end of my TMB 152, metal clips and plastic spacers hold it all together. Still recognised as one of the finest scopes made. Look at the many TMB pics on my web site to see the missing diffraction spikes!

Dennis

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Darth Takahashi

Darth Takahashi

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Dennis,

Fully agree with you regarding your TMB. I think the point is WO have been too greedy with the FLT132 and the tabs are obviously being picked up in the optical train. As Steve points out, baffleing would have prevented this. Perhaps then the FLT132 its really a 128mm where an extra 2mm baffling would have stopped this issue dead in its tracks.

Alas we will never know!

I thought the lens cell in the FLT was made by TMB? Does anyone know whether or not this is still true?

Neil.

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FLO

FLO

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here is the business end of my TMB 152, metal clips and plastic spacers hold it all together.

Not just TMB either.

Also, not wishing to spoil anyones fun but do keep in mind that the FLT-132 is one-half the price of the Tak-130 and one-third that of the TMB-152.

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Darth Takahashi

Darth Takahashi

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Not just TMB either.

Also, not wishing to spoil anyones fun but do keep in mind that the FLT-132 is one-half the price of the Tak-130 and one-third that of the TMB-152.

Very true but it does depend on where you buy? I benefit from the fact that I work in Japan for half the year and know a nice Japanese guy called Yamamoto san at Starbase, Akihabara, Tokyo.;)

If you ever get the chance you should drop in a say hello ;-)

Neil.

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