Indeed, they use the same piece of glass and same quantity of lenses, but it foolish to think that this equates to an “apples to apples” comparison. Similarly, I don’t think it is feasible to compare the FLT-132 or TOA-130 with an Astro-physics 130EDFS simply because it’s a triplet APO using identical glass.
You need to look at the statistics such as spot diagrams, colour correction charts etc (similar to those provided by rsbfoto and RocketBoy) to appreciate the optical differences/controls.
I would highly recommend reading the essays compiled by Roland Christen from Astro-physics - http://geogdata.csun.edu/~voltaire/roland/ Roland is a master optician and produces what many regard as the best refractor money can buy with Strehl ratios of .099! Absolute perfection (many have tried, many have failed). Of interest is some of his essays on single vs. multicoating and colour correction - along with the advantages of correcting up to 1000nm wavelengths for photography. This is something that Takahashi has recently done on their new FSQ.
Don't get me wrong, the FLT-132 would make a great visual scope. I'm extremely reserved in its use for photography. The S&T report indicated that micro 1:10 focuser slips when fine focusing if heavy cameras are attached to the 4" focuser. Fine focusing is critical for photography. In addition to this they reported that when the focus draw tube was locked to hold focus the image shifted. This would result in needing to refocus again. I'm certain better build quality/design could have address this.
The field flattener for the FLT-132 is a requirement, not an optional item as many people think. A native F/7 (no flattener) the image circle size is only 20mm with severe coma in the edges. 20mm image circle would present issues with many DSLRs especially the 5D having a 35mm chip. I believe the flattener increases the image circle to 60mm which is respectable.
This all comes back to what your interests are and managing expectations. I noticed on some of the replies to the thread, cost was deciding factor. While this is valid, unfortunately with optics there are no bargains. You pay for what you get.
Indeed, they use the same piece of glass and same quantity of lenses, but it foolish to think that this equates to an “apples to apples” comparison. Similarly, I don’t think it is feasible to compare the FLT-132 or TOA-130 with an Astro-physics 130EDFS simply because it’s a triplet APO using identical glass.
You need to look at the statistics such as spot diagrams, colour correction charts etc (similar to those provided by rsbfoto and RocketBoy) to appreciate the optical differences/controls.
That's pretty much my point, in the absence of comparable data like that you have mentioned I don't have any basis for detailed comparison or reason to assume that two refractors of the same objective configuration and glass type would have significantly different performance.
If you have any comparative data of that type I would love to see it. Absent that all you can do is star test them ruthlessly (which I plan to do on my FLT-132 when it arrives), read comparisons done by other people or set them up next to each other and compare the views.
The AP scopes might be superior to every other brand of APO but I think that is largely because they are basically hand-made and then individually tested and refined to a point of almost perfection, but the seven year plus waiting list for one rules them out (from what I read on CN people who put their names down in 1999 are now being contacted for the latest production run!).
In all seriousness Stephen, I'm not trying to put you or others off the purchase of the FLT-132. It is a good scope and I feel certain you'll be very happy with it. I simply get disappointed when people draw a conclusion without understanding specifications. It’s like buying Gold, but expecting it to look like Rhodium.
The bottom line is that the same optical design and glass does not equate to the same optical performance. As can be seen in the spot diagrams and colour correction information, there are differences. Many people may see them as subtle, but refractor "aficionados" will assess them for what their worth. A good visual refractor does not necessarily translate to a good astrograph. Hence depends on what you’re looking to do with the instrument. The assessment of optical statistics and performance of refractors is a whole other discussion of which I'm sure there are more qualified refractor "aficionados" than I am that can answer.
Very interesting. What is the vertical scale in the first FLT-132 diagram? If I am reading it right its a diagram of longitudinal sphero-chromatic aberration?
Not quite. Spherical aberration is an image imperfection that occurs due to the increased refraction of light rays that occurs when rays strike a lens near its edge, in comparison with those that strike nearer the center.
What is being shown is longitudinal chromatic aberration (lateral can also be measured). It displays how the wavelengths reach focused at a different distances from the lens. This is commonly seen as fringes of colour around an image. This is due to colour in the optical spectrum cannot be focused at a single common point along the optical axis. The "tighter" the wavelength cross over the less longitudinal chromatic aberration will be present.
Gotcha, got my longitudes and laterals mixed up. The longitudinal colour aberration diagrams I have seen before show the telescope axis on the x axis and the paths of the different coloured light rays on the y so I was assuming that that pic was showing lateral colour aberration.
If I am reading it right now its showing that the FLT-132 is pretty well corrected for longitudinal colour aberration other than for the leftmost ray marked in blue. Strange then that the scale is on the x axis though, wouldnt you be most interested in knowing the distance along the y axis between the points the different colour rays cross it?
Yes, the FLT-132 is quite well colour corrected. Actually, I would expect this for generally any type of triplet. The scale on the x axis show the colour shift or deviation, while the y axis shows the focal ratio (from F/0 at the bottom through to F/7 at the top). You could potentially determine what each y axis scale points are by calculation of the focal length as the focal ratio increases. The most important part is how the colour spectrums converge at focus (at F/7). Adding a focal reducer can change this, so we would need to obtain statistics for its optical design too.
If we compare the TOA-130 longitudinal chromatic aberration chart (attached), you will note the colour deviation is much finer. It’s listed as a maximum +/- 0.01mm deviation for the visual wavelengths g 436nm (blue) through to c 656nm (red or h-alpha). Takahashi provide a chart showing the chromatic aberration through the visual spectrum from UV through to infra-red (400nm through to 900nm – actually this should be all the way to 1000nm).
The chromatic aberrations lines are tighter on the Tak compared to the TMB. It would help if they provided identical charts, but it’s not too difficult to make an assessment. As part of the evaluation process it’s important to also look at spot diagrams and the Strehl ratio.
Last edited by jase; 09-05-2007 at 03:43 PM.
Reason: typo
here are the first 2 shots through the new scope - the eta carina shot was done on a very good night (seeing 8/10) very still, the M83 shot was done while seeing was 5/10 and quite windy. I found the focusing to be quite easy with the focus lock working fine (none if any image shifting) For me focusing using the 10:1 reducer was harder and found it easier using the main focus knob to get it as close as I could.
more to come soon - I sence some good winter weather coming on in mudgee!
Nice results Grahame. Please provide some more info. What is the camera you're using and are these photos taken through the TMB field flattener?
Pleased to hear you didn't have any focus lock issues (with image shifts). Did it take you longer to reach optimal FWHM star values using the coarse focuser? Have you experienced any minor color finging as you approach focus?
Nice results Grahame. Please provide some more info. What is the camera you're using and are these photos taken through the TMB field flattener?
Pleased to hear you didn't have any focus lock issues (with image shifts). Did it take you longer to reach optimal FWHM star values using the coarse focuser? Have you experienced any minor color finging as you approach focus?
The camera is a canon 20D (not modified) and focusing was done by eye, no software help yet
It is easy in my eyes to tell if you are not in focus as the stars look nothing like the pinpoint sources they should be.
Mount used is a Losmandy G11.
The camera is a canon 20D (not modified) and focusing was done by eye, no software help yet
It is easy in my eyes to tell if you are not in focus as the stars look nothing like the pinpoint sources they should be.
Mount used is a Losmandy G11.
Thanks for the info Grahame. No TMB field flattener used??? The Canon 20D chip size is still the same size as the 10D (22.5mm x 15mm). Close to the 20mm flat field image circle the FLT-132 will deliver without the TMB field flattener. I originally thought the images may have been cropped.
Thanks for the info Grahame. No TMB field flattener used??? The Canon 20D chip size is still the same size as the 10D (22.5mm x 15mm). Close to the 20mm flat field image circle the FLT-132 will deliver without the TMB field flattener. I originally thought the images may have been cropped.
Hi Jase,
The TMB field flattener was used for both of these shots, with the first 2 images posted being the cropped ones (check the file names for info)
I have photographed the moon without the field flattener but am yet to review the shots (will do that tonight and post one or two of them)
I have the opportunity to purchase a used, as new Tak TOA-130 for the same price as I would have to pay for the new WO FLT-132. What do I do boys and girls? I've read with great interest all of the constructive replies to this thread however it hasn't made it any easier for me to make a decision. The WO looks stunning, has a great carry case and the Tak looks a bit bland in comparison. I know this may look to be a pretty shallow view but a lot of pleasure can be derived from this hobby by how one feels about his/her equipment. Any input would be greatly appreciated.
By the way, I think Grahames's images taken with the FLT-132 are stunning, well done.
Without hesitation, I would go for the Tak provided it was in an as new condition and you had some evidence of its age, care, handling and performance.
Sometimes plain is good – all the good stuff is in the core design and not the pretty looking bells and whistles. With this kind of investment, my prime goal would be reliability, pedigree and performance – a known quantity with the Tak scopes, even though their doco is very poor, accessories are very expensive and sometimes difficult to get.
But, I’m sure you would be happy either way. Decide on a course of action and stick with it. Don’t look back, otherwise buyer’s remorse will set in, lessening your enjoyment of either fine instrument. Good luck!
"ditto" to the comments made by Dennis. The Tak has my vote as well, but let me elaborate some more.
Firstly, is it the TOA-130 an S or an F. The S has the 2.7" focuser, while the F has the renowned Takahashi 4" focuser? The 4" focuser will see you well into the large format CCD market should you decide to go down this path. The Takahashi will have a better resale value, they do hold their price well in the second market should you decide to sell. WO has some great accessories and yes, the FLT-132 comes in its own case and even includes the WO flagship 2” diagonal. But remember you are buying a scope to look or photograph through, not because it has a "flashy" case or “ultra cool” diagonal. Accessories can sweeten the deal, but you need to assess whats important to you. Indeed, the Takahashi does look sparse when you compare included accessories. This is somewhat intentional as Takahashi doesn’t know what you intend to do with the scope. As you can see there are a variety of accessories/adapters for the TOA-130S/F that you can choose - http://www.takahashiamerica.com/cata...em%20Chart.pdf
I understand you were merely making an assessment, but don't be fooled by images (or at least not too easily anyway). In the hands of an experienced image processor, they can turn an average image into a masterpiece. Certainly, acknowledge them but obviously don't base your conclusion on this alone. The reason I provided the statistical data on both scopes in this thread is so the community can digest this info and make an informed decision. There is a little research required on understanding optical designs and test criteria, but it's well worth understanding.
Really, you can't go wrong with either scope, they both have their target audience. If it were me and the scope was a 130F, I would have already bought it.
Indeed, they use the same piece of glass and same quantity of lenses, but it foolish to think that this equates to an “apples to apples” comparison. Similarly, I don’t think it is feasible to compare the FLT-132 or TOA-130 with an Astro-physics 130EDFS simply because it’s a triplet APO using identical glass.
You need to look at the statistics such as spot diagrams, colour correction charts etc (similar to those provided by rsbfoto and RocketBoy) to appreciate the optical differences/controls.
I would highly recommend reading the essays compiled by Roland Christen from Astro-physics - http://geogdata.csun.edu/~voltaire/roland/ Roland is a master optician and produces what many regard as the best refractor money can buy with Strehl ratios of .099! Absolute perfection (many have tried, many have failed). Of interest is some of his essays on single vs. multicoating and colour correction - along with the advantages of correcting up to 1000nm wavelengths for photography. This is something that Takahashi has recently done on their new FSQ.
Don't get me wrong, the FLT-132 would make a great visual scope. I'm extremely reserved in its use for photography. The S&T report indicated that micro 1:10 focuser slips when fine focusing if heavy cameras are attached to the 4" focuser. Fine focusing is critical for photography. In addition to this they reported that when the focus draw tube was locked to hold focus the image shifted. This would result in needing to refocus again. I'm certain better build quality/design could have address this.
The field flattener for the FLT-132 is a requirement, not an optional item as many people think. A native F/7 (no flattener) the image circle size is only 20mm with severe coma in the edges. 20mm image circle would present issues with many DSLRs especially the 5D having a 35mm chip. I believe the flattener increases the image circle to 60mm which is respectable.
This all comes back to what your interests are and managing expectations. I noticed on some of the replies to the thread, cost was deciding factor. While this is valid, unfortunately with optics there are no bargains. You pay for what you get.
Jase,
While I agree with everything you say concerning the issues and differences between both scopes, I think you also need to consider the reality of the situation.
When one looks at these images of Saturn and Jupiter, taken by Damien Peach using a "lowly" 9.25" Celestron SCT.
I think it becomes painfully obvious that the critical issue is the skill of the person on the end of the telescope and keyboard, not the telescope on the mount, once you get to the premium level of telescope.
If cost is an issue I think the WO will do a great job. If you have other problems in life outside money, you buy the Tak in a heartbeat.
Here's a first light I posted on my new FLT-132 over at CN:
My new WO FLT-132 arrived last week but tonight was the first chance I had to use it. It arrived in a very solid foam padded metal case surrounded by two cardboard boxes and appears to be in perfect condition. The scope is truly a thing of beauty, I found myself just looking at it for the sheer pleasure of admiring the craftsmanship.
I mounted it on myEQ-6 mount and starting at twilight started my gazing. It's lighter than it looks and I found it easy to port and mount. Unfortunately tonight was cloudy in patches and got misty as the night went on so the seeing was average at best but I was impressed by the scope. I started off with Venus and got a nice sharp edge and no colour at all even under high magnification (7mm Pentax XW plus TV 2x barlow = 264x). Later as Jupiter rose higher in the sky I switched to admiring its bands, again without a hint of false colour. I tried a few star tests on bright whitish stars and to my untutored eye the patterns inside and outside of focus seemed identical and nicely symmetrical with no trace of colour.
Star fields were a pleasure to view, nice perfect sharp dots to the edge of the view. I spent a while admiring the Jewel Box and just picking out the different star colours. I definitely enjoyed the subjective aspects of the viewing experience more with this scope than with my Newtonian, it was very nice to be able to sit back in my chair and alternatively look though the EP and gaze up along the axis of the large (to me) refractor, it made me feel like I was experiencing more of a classical telescope experience! Somehow refractors fit my mental picture of what a telescope should look like better than a reflector, irrational I know.
All in all I'm very happy, when the seeing improves I am going to try some comparisons with my 10" Newt to test the different strengths and weaknesses of my two scopes.
I think it becomes painfully obvious that the critical issue is the skill of the person on the end of the telescope and keyboard, not the telescope on the mount, once you get to the premium level of telescope.
CS-John B
That is exactly the point in my last post John;
"Don't be fooled by images (or at least not too easily anyway). In the hands of an experienced image processor, they can turn an average image into a masterpiece. Certainly, acknowledge them but obviously don't base your conclusion on this alone. The reason I provided the statistical data on both scopes in this thread is so the community can digest this info and make an informed decision. There is a little research required on understanding optical designs and test criteria, but it's well worth understanding."
Thus, I acknowledge image processing is critical, but it does not help in determining the difference between the two refractors. Only optical statistics can remedy this.
First Light with FLT-132
