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Takahashi TOA 130 Versus STF 180 Mirage Deluxe

Posted by richard best   07/10/2004 12:00AM

Takahashi TOA 130 Versus STF 180 Mirage Deluxe
TOA 130 versus STF Mirage 180mm Deluxe
By Richard Best
Sussex, England.


I’m not sure if I am qualified to conduct this review since I only became involved in astronomy as a hobby in 1999. At that time £600 seemed an extortionate amount of money to spend on a telescope to look at the stars that I could already see with my naked eyes. I remember with clarity my brother taking only one look and saying, “For the price of that thing you could have a nice holiday.” At the time I did somewhat agree.

In this review I wanted to compare two telescopes of different designs to see, if nothing else, whether an expensive purebred can better a Maksutov crossbred.
It may also be that there are people finding it difficult to justify spending a lot of money on a telescope based purely on guesswork. Hopefully this review can make someone’s decision easier. Since I have purchased both of these telescopes and conducted fairly extensive tests, I feel that I can at least talk about them honestly and with no undisclosed outside interest.

My imaging skills both film and CCD but mainly CCD have come a long way since I started three years ago. This is mainly due to the fact that I have invested in the right tools to make things easier like for example autoguiding. Over the last year even our National magazine “Astronomy Now” even seems to think my images have improved by presenting my images in the reader’s submissions, two even made it to Picture of the Month status WOW.
I have included lots of pictures to keep you interested so make a cup of tea / coffee and I hope you enjoy my first review.

Takahashi TOA 130S

Lens shade shown nearly retracted. Note the stop ring.



























Here is a close up of the TOA 130 lens assembly.































STF MIRAGE 180mm Rumak Maksutov Cassegrain (deluxe)

Here is the STF Mirage with its fixed lens shade and fixed cooling fan on top.


























Here is a close up of the STF lens assembly. You can clearly see this is of the Rumak type because like Schmidt Cassegrain telescopes, this also has a separate secondary mirror rather than reflective spot on the inside of the front corrector.


























As you can clearly see they are both superb looking instruments. The Takahashi has a more showy appearance with its high gloss paint and lustre that the STF lacks. Having said that, the STF has a different look and feel to it, one that is more centred on performance rather than sheer aesthetics.

The review is broken down into the important criteria of specification, optics and my conclusion. (Bearing in mind that the editor’s decision isn’t final!)

Specification

The Takahashi TOA 130 is an air-spaced triplet refractor APO with the central lens being ED glass. The focal length is 1000mm and the focal ratio is f7.7. The tube weighs in at 10kg/22lbs and feels slightly nose heavy (it’s a big lens cell with lots of glass). This is one reason why Takahashi ships the OTA with a tube weight/counterbalance similar to the tube rings made of cast iron. It does work well but adds even more weight (nearly 1kg/2.2lbs). The OTA is 1120mm long with the retractable dew shield extended and 980mm with shield retracted. When you buy the TOA 130 it only comes standard with the visual adapters, so be ready to spend more money on finders, rings, etc.

The STF 180 is a Rumak-Maksutov Cassegrain variation of the Maksutov design. Simply put, this means it has a separate secondary mirror instead of a reflective spot on the rear of the corrector lens. This, I’m told, affords the telescope designer more freedom to alter f-ratios, enables better field correction and corrects for coma. But, this all this comes at a price premium as compared to standard Maksutov Cassegrains.
However, the STF is still only just a third of the price of the TOA 130, which makes it in my view very affordable!
The STF has an aperture of 180mm and, being f10, gives a very usable 1800mm focal length, which is great if you’re looking for a high resolution imaging scope. Strangely, the STF weighs nearly the same as the TOA (8.5kg) but without all the heavy rings it feels a bit lighter. It still however makes you feel that it is a quality telescope (heavy is quality right?).

My STF is the deluxe version. This means it comes standard with 1/8th wave optics and a cooling fan. More will be said about this later.

The tube is a compact 765mm in length with the integral dew shield attached and only 500mm when removed, although you would never need to remove it except for cleaning

The STF Deluxe comes with a safe wooden shipping crate and an extremely well made canvas padded bag. It is also supplied with a very good 7x50 finder, a nice camera holder that attaches the same way the finder does and an integral cooling fan. There is also a separate auxiliary fan that screws onto the rear cell (one pushes air from the eyepiece end while the top pulls air through the OTA). Believe it or not, I even found I could leave the gentle top fan running and the visual impairment was next to nothing. No eyepiece adapters are supplied but the cell threads are the same as Schmidt scopes so take your choice!


Both are very well built with the TOA taking the lead at this point in the review just due to its sheer finesse and attention to detail. They will both easily last a lifetime, just buy a damn good case for the TOA! (Takahashi really should supply a case considering the cost of the scope.) Both the Takahashi and the STF will need a moderate mount especially if you will be imaging and using separate guide scopes. The Astro Physics (600, 900 and 1200), Losmandy G11, Vixen Atlux ect are going to be the minimum requirement.


Optical and Field Performance


When you first take these scopes from a warm house to the outdoors you will notice that the TOA acclimates much faster. Despite what some people say, I find it to be very good in our British climate. It needs no more than 30 minutes.

The STF will require longer (I found often nearly an hour) but using the cooling fan could often reduce this time to as little as 10 minutes. I did find that as the temperature drops, the STF would need the fan turned on for a moment to keep it on track with dropping temperatures.

Both scopes have excellent dew shields that work well.

Both telescopes have excellent mechanics and show zero image shift while focusing. Of course they operate entirely differently, but from a visual and imaging point of view, they couldn’t be any better. My TOA has the 2.7inch focuser, which, until they come out with a CCD the size of 6x7, isn’t a problem. Also, as many may be aware, the Takahashi focusers are legendary and with the addition of the 10:1 micro adjustment accessory, they are still as good as anything currently available.
The STF is fairly similar in layout to all the Meade and Celestron Schmidt-Cassegrains in that the focuser and eyepiece placement are the same. I find the focuser to be a useful size even with gloves, however it can sometimes seem slow in it’s gearing when making large alterations (for instance, changing to the f6.3 reducer) but it is extremely precise for fine focusing. The focuser is fairly long and this can cause it to clash with the diagonal/ binoviewer in certain positions.

One important aspect of visual astronomy for me is the use of binoviewers. I have the Denkmeier standard refractor version with the 2” f5 rich field Starsweeper. The STF worked extremely well with and without the Starsweeper. The TOA 130 is fantastic with the binoviewer but to my surprise didn’t have quite enough forward travel to use without the 1 ¼ OCS. This is a shame because the TOA should be fantastic for low power rich field views. At high power (4 x powermate, bino viewer and 12.5mm Ortho’s = 320 times power), the views are still incredibly sharp and full of contrast.

Planets / Moon

While viewing Saturn and Jupiter, I found I could never see quite the same detail with the STF as I could with the TOA. By detail, I mean low and high contrast areas. Both planets were noticeably brighter in the STF, which can obviously be attributed to its larger aperture. Often the views were more stable in the TOA. I found I would spend nearly all my time looking at the planets through the TOA. One key point to remember is I never knowingly had a night of exceptional seeing, which may work in the favour of the STF with it’s larger aperture.

Looking at Jupiter’s moons is another pleasing past time with the TOA. With practice one can tell which is which purely based on size, brightness and colour shade. This is not quite the case with the STF although the difference between the scopes was very subtle.

Using a Meade 18mm SWA in the binoviewer and 2x OCS (110x magnification), the TOA would show nice detail quite clearly and precisely. The STF with the same setup, minus the OCS, (giving 100 x magnification) seemed softer and slightly lacked low contrast detail cutting edge contrast of the TOA.

In my opinion, the TOA is the better planetary scope.

With lunar observing, I believe contrast is more important than overall brightness. Since the TOA is probably one of the finest colour corrected refractors money can buy (my opinion) the issue of colour didn’t even arise. Surprisingly though, the STF appeared slightly warmer in colour than the stark views through the TOA. Looking at the crater Plato, I could easily discern 4 or 5 craterlets but with the STF, at times it was hard to see 2 or 3. While viewing Copernicus, the TOA would show the central peaks as three main structures whereas the STF could only manage two. Tyco showed a similar result with the TOA clearly managing to show the crater walls with more definition.

For lunar observing, I found the TOA more satisfying to observe with, no matter what eyepiece set I used.

Stars and Deep Space

This is where the STF shows its aperture advantage. To my surprise, the TOA still manages to compete. For objects like globular clusters, planetary nebulas and other small, tight objects, the STF was slightly better in terms of visibility and ease of viewing. The TOA still manages to show objects such as M13, M3, M45 and the Double Cluster in an almost magical way (remember the often mentioned “diamonds on black velvet”). This is due to the sharp definition of the stars, which somewhat makes up for the lack of aperture. For objects such as M57, M27, M81 and M82, the STF clearly wins due to aperture. One benefit that the TOA has is its ability to use widefield eyepieces, allowing for a “wow” feeling more often than the STF.

Stars snap to focus equally well in both telescopes, though are slightly tighter in the TOA, and reflect what one expects from top drawer optics without a central obstruction!

CCD Imaging

I won’t delve too deeply here because I feel the TOA justifies its own review specifically as an imaging instrument (The STF has already been given a thorough review see below). With the f5.8 TOA reducer/flattener, I believe it’s capable of out performing the Takahashi FSQ though it does come at a significant cost increase. I intend on doing a comparative review soon.

The STF has already been very fairly reviewed by Dominique Dierick on Cloudy Nights and it would be a good idea to read that in conjunction with my review.

What I will add is that these two telescopes are both first rate in their respective fields with the TOA well suited for low-to-medium focal length and the STF for medium-to-long focal length imaging and visual viewing. Using my Starlight Xpress SXVH9, I did find the star images to be sharper and tighter using the TOA as compared to the STF.

Before using the STF, I made sure I was meticulous with collimation. Incredulous as it seems the STF arrived from Germany in perfect collimation! This is a good proof of its tremendous build quality! I’ve collimated this scope only once in 6 months and even that wasn’t really necessary. The STF has the standard 3 push pull screws on the secondary should it need adjustment. However its worth pointing out that the TOA also arrived in perfect collimation. Should it ever need adjusting which I doubt there are not 3 BUT 6 sets of push pull lens adjustment screws yet another indication of quality!







Here you can just see the earlier mentioned collimation screws
























This picture shows both scopes a top my AP 900 GTO mount.





The following images were taken at prime focus with equal processing and similar total duration (10 minutes). The difference in focal length is quite obvious as is the sharpness. What can be clearly seen is that they are both intended for totally different jobs with reference again to image scale and focal length. Decide for yourself what you think you will image more often and what your requirements are.

Remember that tracking accuracy is very important when imaging at longer focal lengths. If you feel your imaging skills and mount may be pushed to and beyond the limits, the TOA may be the better tool. Because of the British climate, the TOA may also get more use visually and for imaging since longer focal length scopes require more stable weather for imaging.
STF Mirage 180 (top image), Takahashi TOA 130 (bottom image)




































CONCLUSION

I was hoping the conclusion would be incredibly obvious, but it is not. This is in part because I really want the TOA’s high price tag to be justified but also because I feel that the STF is a worthy scope. The STF is the sort of trusty friend you grow to really like, much like a pet. It also makes a wonderful package with everything you really expect and more for the money.

However, the TOA is the kind of telescope you would feel justified leaving to your children. It feels incredibly robust and does everything so well. I feel that Takahashi should, considering the cost of the TOA, supply a case to protect it.

In conclusion, the TOA is my favourite visual and imaging scope but as an affordable package the STF is worthy of consideration. As with many things, you do get what you pay for and the cost difference between the two is easily a family holiday! But for the perfectionist, the TOA is a fantastic performer that will never fail to please.

If you want both a great scope and a holiday, the STF is a fine choice. For sheer perfection, it just doesn’t quite compare to the TOA. Used together, both scopes actually compliment each other well. I even mount the STF on top of the TOA on my AP900GTO!
PS Hope you like my first review let me know what you think?
www.bestastroimages.co.uk and leave a message in my guestbook!




Click here for more about the Takahashi TOA-130 Ortho-Apochromatic 130mm Triplet Refractor OTA Only - 2.7" focuser
. -Ed.