Starfield 102 Vs Tak FC100D

[globular]

The OP is trying to do a visual comparison of these telescopes. Not just a pure optical figure comparison, but rather how they perform when used visually using diagonals and eyepieces.

We all know that diagonals and EPs introduce their own issues, and the ones the OP uses may favour one scope over another while a different choice of them might favour them the other way round.

But I’d rather see a range of diagonals and EPs compared in both scopes than an artificial optics only test. We can look up DPAC results or other photographic comparisons on the astrophotography forums. But here in visual we use diagonals and EPs so should try and work out how we can do as fair as possible comparisons with them in the telescopes rather than without them.

That way we’ll be judging which one performs best visually in the reality of doing visual astronomy, not which one takes the best pictures.

[CraigT82]

I’m not trying to conduct a definitive test…. Merely trying to help myself decide which scope to sell.

They are close in terms of sharpness, with the Tak a little sharper (as seen through my existing diagonal and EPs) but obviously there are other things to consider with regards to optical performance but also usability. I am intrigued by the sharpness gap though and I will try with an astro camera straight through to see if that shows the difference a bit more clearly than snapping pics with a phone. 

I have to admit though I’m currently leaning towards selling the Tak. I’d love to keep it but the honeymoon period of owning my first Takahashi has worn off and cold hard reality is starting to bite. 

 

Edited August 26 by CraigT82

[dweller25]

1 hour ago, CraigT82 said:

I’m not trying to conduct a definitive test…. Merely trying to help myself decide which scope to sell.

They are close in terms of sharpness, with the Tak a little sharper (as seen through my existing diagonal and EPs) but obviously there are other things to consider with regards to optical performance but also usability. I am intrigued by the sharpness gap though and I will try with an astro camera straight through to see if that shows the difference a bit more clearly than snapping pics with a phone. 

I have to admit though I’m currently leaning towards selling the Tak. I’d love to keep it but the honeymoon period of owning my first Takahashi has worn off and cold hard reality is starting to bite. 

 

Looking at high power at a low contrast object will tell you what you need to know - I would suggest you look at Jupiter at around x190

Edited August 26 by dweller25

[apaulo]

Having owned and used a starfield for about 2 years now, I  can honestly say its a superb scope and rarely for astro gear , is worth the money.  I feel like craigs prblem is he has a daimler and a rolls royce .  which one do you want most outside your front door.  Good luck craig lol.

[John]

I have a Tak FC100-DL F/9 doublet and a Vixen ED102ss F/6.5 doublet (which uses an FPL-53 element). They are both Japanese made and great performers but the Tak is slightly superior optically, slightly but noticeably. The 1st diffraction ring is thinner and fainter with the Tak and it seems more comfortable at maintaining image sharpness and planetary contrast in the 200x - 300x zone than the Vixen does. The Tak cools down much more quickly than the Vixen (practically immediately in fact, even on a cold night). I love them both though, having owned the Vixen for 17 years now and the Tak for 8 years. I know them well 🙂

I suspect the performance edge of the Tak is down to the F/9 focal ratio, Fluorite glass and slightly better figure and polish than the Vixen but the Vixen is no slouch - it proved at least as good for sharpness and CA control as the Skywatcher ED100 that I owned before it did. 

The F/6.5 focal ratio of the Vixen gives it widefield ability that the Tak can't match and it's overall a more versatile scope. 

Luckily I don't have to choose between these two 😉

Edited August 26 by John

[dweller25]

I have pondered the value for money/best optics issue many times.

Being a Yorkshireman helps because value for money is ALWAYS important - AKA tight 🤣

When making a purchase of anything in life, 99% of the time I check the low to high price range of the type of item I want to buy and get something mid range.

BUT, for Astronomy there are not many clear and steady nights in the UK and you only live once.

So my logic is to get the best optics possible to take advantage of when a clear night comes along 🙂

Edited August 26 by dweller25

[apaulo]

A half yorkshire man. A true yorkshireman would borrow a scope hahahah

[Mr Spock]

I sometimes have pangs for the Starfield and regret selling it. Especially when thinking about the cost; the focuser to fix the Tak's problems, and required accessories such as rings and dovetail, all cost as much as the Starfield!

I do like the zero cool down of the Tak though. That's the only difference there is for the extra £2k cost. I'm too committed financially to go back...

[Ratlet]

1 hour ago, apaulo said:

A half yorkshire man. A true yorkshireman would borrow a scope hahahah

Scope?  Scope?!  LUXURY!

When I were a lad we used to dream of scope.  Our dad would get us up 5 hours before we went to bed and work for 27 hours down t'mine so we were properly dark adapted before we'd go out for a look at the sky.  Course we were so poor we could only look at the house the next town over that could afford a candle.

Try telling kids these days that and they won't believe you

[IB20]

No testing required, keep the Tak. You’ll find selling a cheaper scope easier too! 

[CraigT82]

5 minutes ago, IB20 said:

No testing required, keep the Tak. You’ll find selling a cheaper scope easier too! 

Yeah this is a good point. Also the market seems pretty slow at the minute. There is mint  DF with accessories on UKABS sat unsold at £1600 which is think is too low. 

I’m now tempted to keep both and turn the Starfield into a dedicated solar scope. 

Honestly I’ve given less thought to buying a house than I’ve given to which of these two scopes to keep! 

[CraigT82]

Test number 2: Astro cam straight through - no diagonal or EP.  Used an ASI485mc. Exact same settings for both images, and used sharpcap edge detection feature to find best focus for both. 
 

Starfield on the left and Tak on the right:

 

[RobertI]

27 minutes ago, CraigT82 said:

Test number 2: Astro cam straight through - no diagonal or EP.  Used an ASI485mc. Exact same settings for both images, and used sharpcap edge detection feature to find best focus for both. 
 

Starfield on the left and Tak on the right:

 

Looks a bit grainy to me. 

[CraigT82]

Couple more crops from the images captured today with the Astro cam straight through. 
 

The first one shows what I believe is better contrast in the Tak. This blob thingy in the shadow on the underside of the wood (chrysalis or spiders egg?) Again Starfield left, Tak right. 
 

The second image is a crop of some bird poo 😂. Which was located at the far right of the frame (the image in my previous post was on axis). The sharpness difference is much bigger here, perhaps due to more field curvature in the f/7 Starfield compared to the f/7.4 Tak?

 

[John]

20 minutes ago, CraigT82 said:

Couple more crops from the images captured today with the Astro cam straight through. 
 

The first one shows what I believe is better contrast in the Tak. This blob thingy in the shadow on the underside of the wood (chrysalis or spiders egg?) Again Starfield left, Tak right. 
 

The second image is a crop of some bird poo 😂. Which was located at the far right of the frame (the image in my previous post was on axis). The sharpness difference is much bigger here, perhaps due to more field curvature in the f/7 Starfield compared to the f/7.4 Tak?

 

If that is replicated visually, say on lunar or jovian detail, that's quite a difference in both contrast and sharpness, IMHO.

If it's only noticeable when observing bird poo on wood then it's a more questionable benefit of course 🤨

 

 

 

Edited August 26 by John

[dweller25]

If all things are equal, the scope on the right gives the sharper image with better contrast - it’s brighter too.

Edited August 26 by dweller25

[Mr Spock]

39 minutes ago, John said:

If that is replicated visually, say on lunar or jovian detail, that's quite a difference in both contrast and sharpness, IMHO.

Not replicated visually with my two scopes. Both were even as far as detail, sharpness and brightness. I've no idea about these images... If that's a real difference then I'd send the Starfield back as it's not performing as it should.

[RobertI]

I wonder whether atmospheric turbulence wipes out these differences most of the time for the average observer, and it’s only when viewing very fine low contrast detail (eg: Jupiter) under excellent seeing conditions at high magnification that a slight difference might be seen? 

[vlaiv]

1 hour ago, Mr Spock said:

Not replicated visually with my two scopes. Both were even as far as detail, sharpness and brightness. I've no idea about these images... If that's a real difference then I'd send the Starfield back as it's not performing as it should.

Does Starfield come with any sort of certificate / guarantee of quality?

What is expected quality of starfield scope?

[CraigT82]

Don’t get me wrong these images I’ve posted are heavily cropped. When viewed uncropped (below) the differences are much much more subtle, and that’s when looking at a still image capture. When viewing at the eyepiece I cannot see any differences at all. Seeing, extra glass (diagonal and EP) and crucially, eyesight, all work practically eliminate the differences these cropped images above show. For me that is… there are definitely people out there with better glass and better eyes who could see the difference between the two scopes. 

[JeremyS]

I know you know this, @CraigT82, but a proper star test at night is the only way to tell. Supplemented with Jupiter tough double stars 

Edited August 26 by JeremyS

[CraigT82]

14 minutes ago, JeremyS said:

I know you know this, @CraigT82, but a proper star test at night is the only way to tell. Supplemented with Jupiter tough double stars 

Thanks Jeremy. The problem is that kind of assessment requires not only clear skies and good seeing, but also the energy and motivation to stay up until it’s dark, neither of which I currently have due to two small humans who like to begin their days loudly and usually before 5am 😆 

[IB20]

1 minute ago, CraigT82 said:

Thanks Jeremy. The problem is that kind of assessment requires not only clear skies and good seeing, but also the energy and motivation to stay up until it’s dark, neither of which I currently have due to two small humans who like to begin their days loudly and usually before 5am 😆 

I feel your pain brother. 🤣

[CraigT82]

19 hours ago, vlaiv said:

Does Starfield come with any sort of certificate / guarantee of quality?

What is expected quality of starfield scope?

No it doesn’t come with any certificate or anything. But there is nothing wrong with this one, looking at heavily enlarged still images makes it seem like it’s nowhere near the Tak but in reality under normal visual conditions it pretty much neck and neck. 
 

What I’m most intrigued by is the difference at the edges of the field which I think can only be field curvature (i.e stronger field curvature in the slightly shorter Starfield). I’ve had a read of the field curvature section on telescope-optics.net but as usual I didn’t understand a word that was written there! 
 

I wondered if a slight misalignment of the lenses of the Starfield doublet would produce off axis aberrations, but looking at that section on the site it says that the aberration produced by out of alignment lenses is evenly distributed across the field, so it’s not that. 

[vlaiv]

2 minutes ago, CraigT82 said:

No it doesn’t come with any certificate or anything. But there is nothing wrong with this one, looking at heavily enlarged still images makes it seem like it’s nowhere near the Tak but in reality under normal visual conditions it pretty much neck and neck. 
 

What I’m most intrigued by is the difference at the edges of the field which I think can only be field curvature (i.e stronger field curvature in the slightly shorter Starfield). I’ve had a read of the field curvature section on telescope-optics.net but as usual I didn’t understand a word that was written there! 
 

I wondered if a slight misalignment of the lenses of the Starfield doublet would produce off axis aberrations, but looking at that section on the site it says that the aberration produced by out of alignment lenses is evenly distributed across the field, so it’s not that. 

Yes, it is pretty hard to get the idea of how much difference that really makes.

I'm inclined to think that it is non trivial amount of difference as 485mc picks it up. It is OSC camera so in reality it has only the half of resolving power of mono version (if that is not remedied with Bayer drizzle approach and stacking) and with 2.9um pixels - it is really suitable for around F/14.5 systems - which is double of what these scopes have. We can say that you are under sampled by x4 when using this camera natively - and it still shows the difference between the two scopes.

Here is what I would do to try to make the sense of optical difference between the two scopes:

1. use high quality eyepiece - good ortho - in straight thru configuration (no need to add diagonal, or perhaps even with diagonal to simulate observation conditions)

2. use good smartphone to simulate target (these days any will do as most have good enough screens with good number of pixels).

3. Put image of Jupiter on smart phone screen (very detailed one - find Hubble Jupiter image online) and place smart phone at a known distance (use laser range measuring device to get precise reading - it will be needed).

4. Make sure that image of Jupiter on screen creates about say 45 arc seconds image at a given distance - whilst making sure that Jovian disk covers as much of screen / a lot of pixels on screen so that screen pixels can't be resolved

5. Use DSLR with manual focus lens of appropriate focal length - calculated so that DSLR oversamples by quite a bit (at least x2 given its pixel size as it is also OSC sensor). Focus lens at infinity and use the same settings to take the image between two scopes. Use focuser on each scope to get the best image

6. Scale each image so that pixel size is at critical sampling.

7. Look at such images but also compare images with auto brightness / contrast applied to each (our eye adapts if nothing else is in the view - it adapts to brightness and it tries to do "white balance" or color adaptation as well as contrast adaptation - it can't do miracles but it can do small adjustments - so that image looks "the best").