52 replies to this topic

[Jeff B]

Last year I took possession of a used CFF F6.5 oiled triplet, S/N 030, originally purchased in March 2017.  This scope has an oiled objective and uses FPL-55 glass for the ED center element.  I don't know the mating glasses and I respect CFF's design as proprietary so I did not and will not ask what mating glasses are involved.  I will mention that CFF says that this series of scopes have a hand figured aspheric on one of the exterior optical surfaces to help correct higher order aberrations 

 

I believe this model is still in active production

 

Please be aware that this evaluation is of this particular S/N CFF 160 F6.5. 

 

The scope came with an excellent, wheeled travel case (which weighs almost as much as the scope!), mounting rings and dovetail.

 

For those of you who like numbers, the documentation supplied with it includes a test report which lists in green light (5.762 nm):

 

RMS wavefront error:   1/47.7 waves

P-V wavefront Error:     1/6.136 (shoot, I would have sworn it was 1/6.1355)

Strehl Ratio:                  0.983

 

Like my other reviews, this review will be progressive, as the material develops.  I will first evaluate the physical aspects of the scope and its construction, followed by the DPAC evaluation with R,G,B LED's.  The DPAC results will be photo-documented.  I will then evaluate the scope visually, first by itself and then, over a much longer time interval, in comparison with some other 160mm class aperture triplets from TEC and AP.

 

Actually, except for a visual refresher and the comparisons, most of this stuff is already done.  

 

I do need to mention that I have had some very nice technical discussions regarding this particular sample with CFF and they have responded quickly with good technical detail.  I appreciate that.

 

I hope you all will find this useful and interesting.  I'll leave the entertainment aspects   of this posting to those who choose to comment. 

 

Jeff

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Edited by Jeff B, 13 March 2019 - 02:57 PM.

[Kunama]

Got my bag of snacks ready, just waiting for more information/opinions/thoughts .....  

 

(this is a scope I am considering for the future, having seen the build quality up close on a friend's CFF140F7.5 I am very impressed with the brand)

[moshen]

A couple of folks (Rohr & a CN member here) have photographed a double pass knife edge of CFF scopes and was able to see aspheric polishing marks quite easily.

 

Perhaps of no consequence as they may be on the order of 1/50-1/100 wave of light, but someone mentioned CFF did comment on improving their polishing method in the future.

 

I'd be curious if you see / photograph these on your sample and how smoothness compares to the other scopes in knife edge. 

Edited by moshen, 13 March 2019 - 03:53 PM.

[astro42]

I just went to the CFF web site and they have a beautiful 8" F8 refractor.

24,990 euros.

That's $37,672 Canadian dollar. 

Second mortgage on the house anyone?

[Jeff B]

Again, I'll start off with some of the physical stuff and initial inspections.

 

I did replace the excellent stock end cap that came with this scope (which has three radial thumb screws) with a thin AP back with three locking thumb screws.  This endcap configuration has about an extra half inch of back focus over the stock version which is very useful when it comes to bino-viewer use (more on that in a later posting).

 

Firing my Glatter Laser down the tube showed the exit beam dead center in the middle of the aperture mask I use for this test.  Needless to say, the Cheshire eyepiece showed just one, tight and round reflection dot.  

 

The only mechanical issue I did run across was that the dew shield was too loose.  It would not lock when fully extended and would slide back down the tube when the scope was pointed towards the vertical.  This was easily diagnosed and fixed by me by removing the shield's end ring, sliding the shield back past the lens cell and applying an extra layer of rub tape to that which was already there.  Fixed.  And CFF contacted me later with the exact same fix.

 

Some of the physical stuff:

 

1. Length with the new endcap and the dew shield fully retracted is 33.75" (yes, it's that short).

2. Weights are as follows:

     a. Bare OTA :                                               26.0 lbs.

     b. OTA w/rings & dovetail:                           29.5 lbs.

     c. OTA as pictured ready to observe

         with rings, dovetail, finder assembly,

         diagonal and full Denk II viewer system: 36.0 lbs.

 

For comparison, in configuration c., my 140ED (with handle) is 30 lbs., my TEC 160ED F8 is 34 lbs., old AP 152 F9 is 34 lbs., old AP 152 F10 ATM build is 40 lbs., and former TMB/APM 152 F8 was 38 lbs.  This is a very stout scope.

 

Both my Losmandy G11 and GM100 are quite comfortable with the OTA, which comes as no surprise as this sample of the G11 was superb with the TMB/APM 152 F8 and TEC 160ED.

 

I also found the OTA surface finish just beautiful but just a touch more slippery than that of the TEC 160ED, but I still got good grip with my hands. 

 

I did my usual bunch of residual back focus measurements (RBF) with several diagonals as that is important to me for bino-viewer use.  With my standard AP Maxbrite diagonal with the DPAC grating screen placed directly on the top of the diagonal (no 1.25" adapter), I measured 111 mm (!) of RBF using the shorter endcap configuration.  With my Lumicon deluxe 2" diagonal there was 118mm and, in fact, I had to extract the focuser a little to get that figure, while an ancient Novak 2" diagonal from the 80's had 113mm of RBF.  With the Baader/Zeiss prism and BBHS diagonals with 1.25" quick lock top, I had to use a 1.75" extension to get too and measure positions but I neglected to write them down as these are configurations I will never use except for bino-viewing.  

 

More later.

 

Jeff

Edited by Jeff B, 13 March 2019 - 05:19 PM.

[fate187]

With my CFF185 in service right now I will watch this thread   .

would love to test my scope(s) this way as well. Needs a mirror flat and some other less expensive goodies from what I read. 

Edited by fate187, 14 March 2019 - 01:35 AM.

[Kent10]

I just went to the CFF web site and they have a beautiful 8" F8 refractor.

24,990 euros.

That's $37,672 Canadian dollar. 

Second mortgage on the house anyone?

That is with VAT.  You wouldn't have to pay that.  20,317 euros for you.  Now can you afford it? 

 

24 990 Euro, includes VAT 23%. Net export price – 20 317 Euro (non EU countries)

[junomike]

That is with VAT.  You wouldn't have to pay that.  20,317 euros for you.  Now can you afford it? 

 

24 990 Euro, includes VAT 23%. Net export price – 20 317 Euro (non EU countries)

Also the CDN $$$ has been poor/weak these last few years which makes things worse.

The USD is very close the Euro at the moment.

[fate187]

TS has the cff200 for a little bit less than sais here. I was shown the scope when I picked up my cff185 from them. Very large OTa, not a one man show in my opinion. Thats good, otherwise I would have bought it   .

 

I can confirm what moshen said about the a new polishing method...

[Jeff B]

So a few more measurements.

 

Available back focus as measured from the face of thin AP back is 217 mm (!).  Imagers might appreciate that.

 

That's a lot BF and CFF, I believe, offers two choices, 180 mm and 200 mm.  Mine has more as I swapped out the stock back that came with the scope in favor of the thin AP back as I use bino viewers a lot.  That gave me the extra 17 mm.

 

Speaking of bino-viewers, as you can see by the generous amount of back focus, this scope is very bino-friendly in certain configurations.  No corrector/barlow required.  Here are some of the configurations with their residual back focus measurements in DPAC with the grating simply placed upon the top of the eyepiece collet.

 

1. Denk II, 2" nose piece, AP Maxbrite diagonal:               2 mm

2. Denk II, 2" nose piece, Lumicon 2" Deluxe diagonal:     7 mm

3. Baader MK V , T2 quick changer, 2" nose piece, 

    Lumicon 2" Deluxe diagonal                                           0-1mm

4. Baader/Zeiss Prism Diagonal, T2 Quick Changer, 

    2" Nose piece, Denk II with quick changer adapter        46 mm

5. As above but with Zeiss "Std" viewer w/30 mm Prisms  46 mm

6. As above but with Zeiss Lite Weight, "LW", with 

    Mirrors, called "Zeiss Sharpest" by Denis Levatic           38 mm

 

I also found that with configurations 4-6, I had enough room to insert a specially made Denk Power switch with a barlow element in each switch arm (giving 1.7 and 2.8 X).  Using the switches though I had to rack the focuser out 2-3 inches, resulting in balance issues due to the viewer weight.  Also, during extensive visual testing last year, with the exception of configuration 6, using the switch in this manner with this scope was not optimal, leaving a bit of additional residual chromatic effect.  Added chromatism was still there with configuration 6 but much lower in level than configurations 4 & 5.

 

But the best, sharpest high power bino-views to be had with all viewers came when I used the standard Denk Power Switch System.  This was by far my favorite bino-configuration for high power, both in terms of sharpness and back focus positions. 

 

And I could see that lack of chromatic effect at work in DPAC with this scope too.  This could be a subject for the bino-viewer forum. 

 

But I still do want to pick up at least the Baader 1.25 X GPC too for the Baader & Zeiss viewers.   

 

So this sample is a very bino-friendly scope.

 

Jeff

[Jeff B]

I know, I know...where are the DPAC images?    

 

Well, here you go starting with my buddy green

 

 

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[Jeff B]

And then there is ruby red....

 

 

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[Jeff B]

And finally, bad as s blue

 

 

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[Jeff B]

And at focus, in green

 

....And the crowd went wild.

 

 

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[moshen]

Bottom image shows a very good null in green. Green ronchi shows minor undercorrection on outer edges but in my own DPAC images I know camera can play an effect on capturing ronchi well. Red & blue sphero-chromatism looks very well balanced.

 

Nice job!

[rcg]

Nice thing about CFF they will customize the backfocus. I had mine configured for a 2" Seibert binoviewer, 300mm of backfocus. Also reduced some Optical length by connecting binoviewer directly to dedicated diagonal. Needed to adapt focuser back and extensions to 3" for FTF3545 though to maintain unvignetted optical path for normal viewing. Hadn't noticed before looks like your finder shoe is mounted on the tube reducer instead of the feathertouch focuser, was that an option, didn't see that configuration on their website?

 

Great test results though.

Edited by rcg, 15 March 2019 - 03:57 PM.

[Jeff B]

Bottom image shows a very good null in green. Green ronchi shows minor undercorrection on outer edges but in my own DPAC images I know camera can play an effect on capturing ronchi well. Red & blue sphero-chromatism looks very well balanced.

 

Nice job!

Thanks Moshen.

 

That's pretty much my take too.  If you look carefully, the at focus shot shows the mild but uniform hand figuring swirls from the aspherization.  Sometimes, though, I have to wonder if there is some sort of diffraction stuff going on at the edge in some cases with the ronchi.  

 

Funny as I was surprised that my cell phone camera lens was so neutral and accurate in capturing the images as well as the ease of use.  I can't say the same for my fancy DSLR lens.

 

I'm continually impressed with what CFF has done with this rather "sporty" lens.  Visually sharp too.

 

Jeff

[Jeff B]

"Hadn't noticed before looks like your finder shoe is mounted on the tube reducer instead of the feathertouch focuser, was that an option, didn't see that configuration on their website?"

 

Bob, I always use a finder scope/counterpoise weight assembly mounted on its own ring that I attach to the aft part of the scope.  I find I much prefer that as it adds a little much need weight aft, positions the finder a little forward and allows me to use different finders.  I also completely assemble the OTA, ready to use, before installing it into the rings as this make for a one time, balanced lift into the saddle rings.   

 

Jeff

[rcg]

That explains the binoviewer still attached even in "storage" … a few more ideas to consider … your storage area must be convenient to your observing area ...

Edited by rcg, 16 March 2019 - 11:22 AM.

[Suavi]

You have a great selection of fine glass Jeff! I wouldn't mind acquiring such fast 160mm refractor sometime in the future, if funds permit one day.

 

When I read your opening post and you mentioning mating glass, I remembered Catalin writing about it sometime ago, so I dug out this post. Not sure if your 160mm has the same type of mating glass nor that it really matters.

[Jeff B]

Thanks  Suavi and interesting info.

 

I had the scope out last night and was treated to some fine, sharp lunar viewing.  Even saw the "Pup" around Sirius again, a piece of the rille on the Alpine Valley floor and 8 craterlets on the floor of Plato in high sun.  Not too shabby.

 

I'll be posting some observing comparisons of this scope and a TEC 160ED in another thread.   

 

Jeff

Edited by Jeff B, 17 March 2019 - 09:47 AM.

[Jeff B]

Here's the CFF nice and cozy inside and the freezing its backside off outside.

 

 

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[Jeff B]

Corrigendum:

 

Catalin Fus at CFF relayed to me an error I made regarding available backfocus options.  They are typically 180 and 220mm (not 200mm as I stated).

 

Jeff

[gnowellsct]

Maybe we should ask him why he doesn't put the CFF logo on both sides of the dew shield

[dscarpa]

 It's a great scope!  I  like the logo a lot  too. If I was to order one say a 135 or 140 for my empty Unistar-AP tripod would ask for it on both sides.  David