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Ullomat

Tak FC-100DC(F) vs. TeleVue NP-101is

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Hi all,

I already did a comparison between the two scopes with forum member Marcus, but the FC-100 was on a driven mount and the NP on a more shaky undriven Alt-Az mount setup. The views were close, a little better seemed the Tak in terms of contrast or faint stars.

I want to do this comparison soon again but until then I am looking for opinions and experiences with both scopes. Did anybody of you a side by side comparison, too?

The basic differences (Petzval NP, Doublet Fluorite FC) are clear for me so far. 

I guess the conclusion will be: The NP is the better Widefield Telescope (4,5° with a 31mm Nagler) and capable of high magnifications also but the FC Design has the edge in contrast for visual at high magnifications. 

cs,

Uli

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Would be an interesting comparison with equal mounting and conditions. I have an FC100DC and a Televue Genesis, so I know the low power widefield capabilities of the NP101 but it obviously has much better colour correction and high power performance.

I suspect your conclusion above will be pretty close to the actual result.

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Not compared against a Tak but against an 80mm triplet the 101 has a shade less sharpness, tested by looking at distant factory chimneys with birds of prey standing on them, and later on a bright white star. The diffraction patterns had very identical rings on both sides of focus, and perfectly white on both sides, but not as sharp. I made 85mm, 90mm and 95mm stops to complete the comparo (asked by a friend who wanted to know if he had to keep it or sell it), and the findings were the same.

What a Petzal gains in flatness is lost in sharpness, that's why they sell triplets and doublets with a separate corrector.

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When I was considering a top end 4 inch refractor in 2016 I had some advice from mikeDnight who is a member here. He had owned or used a TV NP101 and now owns a Tak FC-100 F/7.4. His description of the differences was that he felt that he had to work harder to tease out subtle planetary details with the NP101 than with the Tak FC-100.

If wide field observing is important to you then the TV NP101 is a very versatile scope but I already had a good wide field ED 4 inch refractor so I went for the Tak FC-100DL.

Maybe mike will chip in at some point ?

 

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Your initial presumption will almost certainly be the result of your comparison. I owned an NP101 and it was superb as a rich field refractor offering a wonderfully flat field. If sweeping the skies for fuzzy objects is where your heart lies, then you'll be hard pressed to find a better 4" telescope anywhere. However, if high power, high definition, high contrast, lunar & planetary, or binary star observing, coupled with some very respectable deep sky performance is more up your street, then the FC is a hard act to follow in the 4" range. Differences may be subtle at first glance, but the FC will outperform the 101 on moon, planets & binary stars. Conversely, the FC, although good and with a wide field, is no match for the 101's rich field prowess. Both are top class in their own right as general purpose refractors, yet both can rightly be thought of as specialist instruments. Also, the 101 makes a first class astrograph!

I eventually sold my NP101 as I felt it struggled to reach high powers. It needed an awful lot of glass in the focuser, in the form of power mates and Naglers etc, to reach even reasonable high powers, and it felt like the photons were panting for breath when they'd worked their way through it all. I now have an FC100DC which better suits my kind of observing, yet still retains the portability of the 101. The FC is as impressive at X400 as it is at X40, providing the seeing conditions allow for it!

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Hi Uli,

let's do our comparison again with two driven mounts ?. Since you are most interested in deep sky observation, the Borg 107FL might be interesting for you as well...

Clear skies,

Marcus

I can also put the DC on the less stable Advanced Polaris ?

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Posted (edited)

Hi Marcus,

we have to do this, yes. If I will follow the FC-100x route, there is still to choose between the DC(F) and DL.

cs,

Uli

I'll check out the Borg as well. In addition, the Vixen SD-103 and more interesting the Vixen SD-115 seem to be not a bad choice 

Edited by Ullomat
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Posted (edited)

Hi all,

additional question, did anyone once compared the FC-100DC(F) side by side to an TSA-102?

The mechanical differences are obvious but how different are they from the optical perspective?

I have an offer for a pristine TSA-102 right now and this is tempting...

cs,

Uli

Edited by Ullomat

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Hi Uli,

if you are confident, that you can sell the TSA-102 for the price you pay, then go for it! ? You should be aware of the higher mount requirements though.

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Hi Marcus,

I'll check out first if it fits on my AzMount Pro. But should do so since the weight is just abt. one kg more than the NP-101is. 

The price tag seems to be OK. 

cs,

Uli

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Hi all,

a lot of testing and reading has been done. The TSA did not fit for the AZMount Pro, too heavy and too long. It seems the AZ Mount has reached it's limits there.

Now the choice is between the FC-100DF and the DL. I had the chance yesterday to do a side by side comparison of the TSA-102 and the DL at my preferred dealer. Very impressive, the DL was on the same level. Testing on an artificial star at 250x - 300x. 

Unfortunately, they had no DF or DC in stock to compare the f7.4 Version, too. 

As a surprise for me, the DL was quite stable on the AZ Mount. The length compared to the TSA is quite the same, but it is abt. 2,5kg less. This made it I guess. So the DF would be very solid. 

I know, the decision is mine at last, but I would appreciate any thoughts concerning this topic. 

I guess some of you are already through this ?

For both of them money's not enough ? but I can call me fortunate enough to be able to buy one of these great scopes. 

cs,

Uli

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Posted (edited)

Hi Uli,

A couple of years ago I had my friends DL on the GP mount in my observatory. I normally use this mount for my DC, and its manual slow motion are the Vixen short control knobs. When using my DC it is very easy to reach the controls, but when the DL was mounted on the GP it was just a little bit of a stretch to reach them comfortably.So longer manual controls or electronic drives would be needed for a GP style mount if the DL were to be used comfortably.  I have also used both the DC and the DL on an AZ4, and found the AZ4 to handle the DL surprisingly well. Again, the slightly longer DL made reaching the tension knobs of the AZ4 a bit of a stretch, but doable! I think if the AZ4 is on the tubular steel tripod it will cope significantly better than the aluminium tripod that my friends DL was on. I'm not a fan of the Chinese aluminium tripods as the are weak, and so even for my DC I chose to use my AZ4 on an older heavy duty Vixen tripod that is seriously solid.

It's a difficult choice between the DF and the DL. The DL didn't exist when I bought my DC, and the F7.4 DC amazed me from the very first moment I looked through it and continues to do so. It has shown me some truly amazing things since I bought it in March 2015. I have no doubt that if you're looking for a truly top class lens mounted in a short, light weight tube, the DF/DC will be hard to beat optically. If however you're happy to accommodate the slightly extra focal length and slightly narrower field of the DL, I very much doubt you'll find a better refractor anywhere, ever!   If I were buying an FC today, I would go for the DL simply because I'm primarily a lunar and planetary observer, but I've now had my DC for four years and we've become best friends. I doubt I could ever part with it even if the opportunity for owning a DL came along, which it has twice already. Both are great performers on all targets, and both have their own wonderful optical qualities. Id say that if money was not an issue, and you are not too bothered by the difference in focal length, then close your eyes  and blindly reach out and grab one. Whichever you chose will be a fantastic scope!

It's often said that a picture speaks a thousand words, so I've attached some pics for comparison. It's important to note however, that the accompanying sketches were made on different nights under different seeing conditions, but I'm sure you'll agree that as 4" refractors go, the views are quite pleasing.. :happy11:

 

 

2019-03-10 17.21.35.png

2019-03-10 17.22.31.png

2019-03-10 18.20.24.jpg

20190310_181652.jpg

Edited by mikeDnight
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Posted (edited)

I know no one else does it but I find adding a counterweight to the AZ-4 is ESSENTIAL. Most of the mass is at the rear and toward the right so the countermass has to be at the front and toward the left, of course.

 

20171110_155238.thumb.jpg.b977dd1cf48e71dc37b6e3c1a5670175.jpg

 

This was an unused weight from an equatorial mount that was sold with two counterweights when one was enough. I drilled and tapped the side of the head but just clamping the Z-arm (made of L's bolted together) will do if you don't want to drill it. Look between the top and the bottom of the head in your AZ-4, you will see it tilts.

So you have to set a tight friction but with the counterweight in place friction is barely needed, you get the double benefit of balance and smoothness. The azimut motion was not fluid enough at high power for my taste so a super narrow 2mm ring was inserted. It's made of that tearproof packaging material, I moved it to the side with a toothpick or you wouldn't see it. Such a narrow bearing surface acts almost as a ball bearing, and it's oiled, too. No problem panning left and right at more than 160x with the 80mm.

 

20190310_230928.thumb.jpg.add3654bb895b1db0abdd665eadb2e13.jpg

 

It's so fluid that just brushing the scope will move it if you don't set a minimal amount of friction, you wouldn't believe how little. Twisting the knob less than 45° after it makes contact is enough.

Unless the mount is balanced the "friction" knob acts as a tilt suppressor more than a friction knob, but that requires much too much force. When it's limited to its real job of friction adjustment, the amount that's needed is stunningly small. In fairness I have to say it makes the mount 4 kilos heavier.

Edited by Ben the Ignorant

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Hi Mike,

thanks for this great feedback!

I have some news concerning my personal DF vs. DL challenge. 

I have been at my local Takahashi dealer's store again yesterday and did a complete test of the DL with my iOptron AZMount Pro. The DF was still not in stock as mentioned before.

Final conclusion is, the DL is not as stable as I want to have it riding on the AZMountPro. Due to its length, there is a lot of vibration with the mount mainly in AZ. This is the weak point of the mount since there is only small bearings. This is more a problem pointing on objects near the horizon and gets better with the altitude of the object. Damping time is worse than 3s at 250x in that bad case after a focus change with a high amplitude. This was tested indoors so already a light gust of wind will be a problem under real observing conditions I think. My current NP-101is (more than 2kg heavier) has only 2s damping time due to its shorter tube) and a much smaller amplitude, we testet this, too. 

This is bad news, since the AZMountPro is my preferred portable Mount. This in mind, the choice will be probably the DF version, since I want to stick with the mount. But since I am planning a more portable setup, the smaller and little bit lighter DF is even better in this respect. In addition, my main targets are DS targets and the advantages of the DL optics compared to the DF should be not so dramatic (I hope at least...)

The DL optics are perfect btw, really good. 

Some time during the next weeks I will meet with Marcus, he has both the DL and a FT modified DS so I can do a last comparison of the both (and my current NP-101) optically and mechanically on the AZMount before I finally pull the trigger and buy the new scope.

I'll report the final step afterwards. 

All the best and cs,

Uli

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I agree that you want to mount whatever scope you go for properly if you are going to realise the full potential of the optics.

My F/6.5 Vixen ED102SS is carried well by my AZ-4 mount but my Tak FC-100DL needs the sturdier Skytee II. Both scopes are the same weight but the tube of the Tak is around 20cm longer and that makes all the difference.

 

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Hi all,

I have an update. 

Marcus and I did a comparison for more than three hours and we could test the DL, the DC and a Vixen ED-103 side by side. My NP was not there, but since I know quite well how it performs this was OK. I tried to figure out, if the DC(DF) or the DL is the way to go for me. 

It was quite obvious for me after some time, that I will go with the DL. There is an obvious difference at high magnifications. I noticed finer (smaller) stars and less to no color when the seeing "disturbes" the defraction ring. The view is more "calm". Sorry, I do not know how to explain it better in english. Reminds me of my former TSA-120. 

The DC is really good also, no question. But the DL has the perfection I am looking for.  

In addition, the AZ Mount Pro was fine this time with the DL, much better as the last time. So I decided to use this combination.

Since I sold my NP-101is yesterday, I today pulled the trigger for a brand new DL for a good price and will pick it up next week. 

Thanks all for your comments and opinions!

cs,

Uli

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It's great that you had the opportunity to test these fine scopes side by side so that you could pick the one that you prefer. It is not often that a prospective buyer has that chance. I'm sure you will enjoy the Takahashi FC-100DL - it is a wonderful scope :thumbright:

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Hi,

yes, I was very lucky to have the chance testing and comparing both scopes. Both are very fine instruments.

cs,

Uli

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