TAK FSQ Fluorite versions

[ollypenrice]

Hi Olly , I have a mate down here that's just got  a beautiful Vixen  DED108SS  direct competition to the Takahshi  FSQ106  I believe ? , its a sweet AP rig that's for sure , as good as his FL102S visually as well , so now there are 3 in the ring the  FSQ , NP and DED  cool ,

But I  also hear the Vixen have a  101mm f 3.9 coming , based on the Pentax ?  all the best for AP , if you can afford  (find) one .

Brian.

I didn't know about the Vixen, Brian, but it is no longer made if I'm not mistaken? Looks interesting. I wonder what happened to it? It's the FSQ85 that I feel has no rivals, maybe because only Tak would dare to market such a costly scope of so little aperture!

Olly

[perfrej]

The QSI is around 50mm to chip...

/p

[ollypenrice]

The QSI is around 50mm to chip...

/p

 In that case it should be hunky dory with the Tak 85. I'm not sure that the CA35 adapter is obligatory. You could get something made to go straight from the reducer to the camera.

Olly

[Davey-T]

Nice pic in September AN of Pelican Nebula, taken with Tak FSQ106 and 460EX .

Dave

[Earl]

 In that case it should be hunky dory with the Tak 85. I'm not sure that the CA35 adapter is obligatory. You could get something made to go straight from the reducer to the camera.

Olly

I needed the CA35 iirc, but i didnt use a reducer.

an 8300 on the Baby Q is ideal, and an all in the box 8300 ie fw and oag is imo way worth the extra few quid to save all the faffing

[ollypenrice]

I'm sure Olly won't like this but you could do as I do with my FSQ85, my sensor of choice is all wrapped up inside a DSLR body

Mel

Oh no, I don't like it but I do like your images (big time) so it's time I shut up!

Olly

[Astroscot2]

Hi Olly , I have a mate down here that's just got  a beautiful Vixen  DED108SS  direct competition to the Takahshi  FSQ106  I believe ? , its a sweet AP rig that's for sure , as good as his FL102S visually as well , so now there are 3 in the ring the  FSQ , NP and DED  cool ,

But I  also hear the Vixen have a  101mm f 3.9 coming , based on the Pentax ?  all the best for AP , if you can afford  (find) one .

Brian.

Hello Brian,   is your friend called Stuart ?    I owned I think one of the few Vixen 108DED in the UK as i sold it to upgrade to the FSQ.

The DED was a great scope, I do miss it.

[ftherrmann]

Just wanted to jump in and say that after 4 nights experience with the FSQ-85 /w .73 reducer and STL11K I was unable to obtain anything close to a flat field.   I was also sent another replacement reducer which gave the same poor results.  My Nikon 200mm telephoto produces a flat field as good or better than the FSQ-85 w reducer.  Very disappointed.   The FSQ-85 gave a perfectly colimated defocused star at center field.  Rotating the CCD/reducer 90 degrees gave the same results.

 I've seen some images made with the new FSQ-106 and .73 reducer which looked almost perfect.  Any experience out there using the new FSQ-106 (Red Branded) refractor with the .73 reducer?\

TIA 

Fred

[kirkster501]

Just wanted to jump in and say that after 4 nights experience with the FSQ-85 /w .73 reducer and STL11K I was unable to obtain anything close to a flat field.   I was also sent another replacement reducer which gave the same poor results.  My Nikon 200mm telephoto produces a flat field as good or better than the FSQ-85 w reducer.  Very disappointed.   The FSQ-85 gave a perfectly colimated defocused star at center field.  Rotating the CCD/reducer 90 degrees gave the same results.

 I've seen some images made with the new FSQ-106 and .73 reducer which looked almost perfect.  Any experience out there using the new FSQ-106 (Red Branded) refractor with the .73 reducer?\

TIA 

Fred

Dear me.  Well, thats not a good story at all Fred!  Is it all brand new stuff?

[ollypenrice]

Just wanted to jump in and say that after 4 nights experience with the FSQ-85 /w .73 reducer and STL11K I was unable to obtain anything close to a flat field.   I was also sent another replacement reducer which gave the same poor results.  My Nikon 200mm telephoto produces a flat field as good or better than the FSQ-85 w reducer.  Very disappointed.   The FSQ-85 gave a perfectly colimated defocused star at center field.  Rotating the CCD/reducer 90 degrees gave the same results.

 I've seen some images made with the new FSQ-106 and .73 reducer which looked almost perfect.  Any experience out there using the new FSQ-106 (Red Branded) refractor with the .73 reducer?\

TIA 

Fred

Now to be fair to Takahashi they make it perfectly clear on their spec sheet that the 85 scope is never going to cover your chip with reducer in place. They claim an image circle of 40mm with reducer and you need a little over 45mm for the 11 meg chip. That is a heck of a difference. Besides, you'd be imaging at 5.6 arcsecs per pixel so the image would look pretty clunky. The Baby Q without reducer doesn't claim to cover the ST11000 either. It only claims 44mm. Part of the confusion, maybe, comes from the non specific term 'full frame' which Takahashi take to mean 35mm. The Kodak 11 meg is over 37mm on the long side, according to Atik. (I use it in one of theirs.)

The FSQ106 (I have the N version) covers the chip very easily at 3.5 arcsecs per pixel native.

Olly

[ftherrmann]

Dear me.  Well, thats not a good story at all Fred!  Is it all brand new stuff?

Brand new and it was all returned to the vendor for refund.

[ftherrmann]

Now to be fair to Takahashi they make it perfectly clear on their spec sheet that the 85 scope is never going to cover your chip with reducer in place. They claim an image circle of 40mm with reducer and you need a little over 45mm for the 11 meg chip. That is a heck of a difference. Besides, you'd be imaging at 5.6 arcsecs per pixel so the image would look pretty clunky. The Baby Q without reducer doesn't claim to cover the ST11000 either. It only claims 44mm. Part of the confusion, maybe, comes from the non specific term 'full frame' which Takahashi take to mean 35mm. The Kodak 11 meg is over 37mm on the long side, according to Atik. (I use it in one of theirs.)

The FSQ106 (I have the N version) covers the chip very easily at 3.5 arcsecs per pixel native.

Olly

Yes I know that the image is under-sampled at 5.6"/pix.  However I don't really care that much about that part of the story.  Unless you zoom in 400% your not going to notice the under-sampling.  However you do notice the coma shaped stars w/o any zoom.  

As far as the specs are concerned here's a cut and paste from the "Land, Sea and Sky", aka Tak America webpage:   

-Flat field w/60 mm image circle

-Image circle will accept medium format CC cameras or Digital SLRs

The 85 + reducer combination doesn't come close to either a flat 60mm circle or 40mm circle as the stars at all edges and corners of the STL chip are distorted.   This has nothing to do with fairness, just fact.  The only thing unfair about this is the fact that I'm no out $150 in shipping costs based on bad information given by the US distributor.

PS:  If the 85 is spec'd for a 60mm circle I also expect a 60mm circle with the reducer.  Since this is not the case a footnote or disclaimer would be in order.

[ftherrmann]

PS:  If the 85 is spec'd for a 60mm circle I also expect a 60mm circle with the reducer.  Since this is not the case a footnote or disclaimer would be in order.

Just saw the spec for the 85 with reducer.....

With reducer .75x

- Image circle 40mm

I notice it doesn't say "Flat" unlike the 85 OTA description.  However like I said....  It doesn't come close to 40mm.  Illumination isn't a problem.   The edges were 60% illuminated when compared to the center of the fov.   Also the .75x reducer isn't correct.  It's actually a .73x reducer.

[kirkster501]

Well, thats not exactly a vote of confidence in Tak - the fiust bad thing i have ever heard said about them!  Do you think you just got a lemon?

I am after a FSQ85 myself.

[ftherrmann]

Well, thats not exactly a vote of confidence in Tak - the fiust bad thing i have ever heard said about them!  Do you think you just got a lemon?

I am after a FSQ85 myself.

I own both the FSQ-106 (old blue label) and a TOA-130.  Never had any problems with either other than the fact that the TOA-130 w/flattener will not produce a flat field using the STL chip.  Works fine with 8300 and smaller chips.  I didn't try the 8300 with the 85 @3.6 but I kind of wonder if it would flatten to the edges of the 8300....

No I didn't get a lemon.  Land Sea and Sky sent me a 2nd reducer/flat to try and it produced the same results at 0 PA and also 90 PA.  The defocused star at the center of the fov was perfectly round, ie collimation was spot on.  The 85 simply won't work with a large chip, at least not with the reducer.   I'm fixing to process one of the image sets I made with the 85.  I'll post it on my google and facebook page if you interested. 

[ftherrmann]

I own both the FSQ-106 (old blue label) and a TOA-130.  Never had any problems with either other than the fact that the TOA-130 w/flattener will not produce a flat field using the STL chip.  Works fine with 8300 and smaller chips.  I didn't try the 8300 with the 85 @3.6 but I kind of wonder if it would flatten to the edges of the 8300....

No I didn't get a lemon.  Land Sea and Sky sent me a 2nd reducer/flat to try and it produced the same results at 0 PA and also 90 PA.  The defocused star at the center of the fov was perfectly round, ie collimation was spot on.  The 85 simply won't work with a large chip, at least not with the reducer.   I'm fixing to process one of the image sets I made with the 85.  I'll post it on my google and facebook page if you interested. 

PS:  You will also see a slight bit of sag using a large/heavy CCD like the STL with the 85.  I had a fully threaded optical train and still saw some slight differences at 0 and 90 PA due to the chip sagging non-orthogonal to the optical axis.

[ollypenrice]

This is very odd because the Tak Europe importer is perfectly clear about the image circles of 40 and 44mm. http://www.optique-unterlinden.com/catalogue/produit/m/0/p/TK023

Where on Earth are Land Sea and Sky getting 60mm from? It's the first time I've ever come across this claim and I know from using my own 85 that it's nonsense. 

In my opinion the FSQ85 is the best telescope I've ever used. Like any other it has its limitations but the figures quoted on the Tak Europe site agree with my own findings. It produces fewer artefacts than anything I've used, controlling very bright stars without flares when the 106 did produce them. (A friend used my 85 Witch Head data to patch his 106 image, for instance, because Rigel, out of shot, had flared in the 106.) As I said earlier, focus holds well, too. In short it's the most incredibly productive, vice free scope - in my view.

The 106 is bigger, has a bigger circle, etc., but I don't feel it's quite as good optically.

Olly

[kirkster501]

They must be good since they are as rare as hens teeth on the used market - as I am finding out now

[ollypenrice]

They must be good since they are as rare as hens teeth on the used market - as I am finding out now

True. A few years ago this was a little known scope since everyone with lots of dosh went for the 106. However, the 85 has carved out a niche for itself, and rightly so. Its biggest enemy will be the new full frame 29 meg chip which plays perfectly, on paper, with the 106. A new APOD factory machine is born!

(Ouch, did I say APOD? Thread closure imminent!  )

Olly

[kirkster501]

106 is overkill for me I think.  I have no desire for a bigger chip than my 460 (famous last words.....). If covering a huge field is a requirement to me at some point I will move to a good 200mm Canon lens and cover a *serious* amount of sky

[ollypenrice]

106 is overkill for me I think.  I have no desire for a bigger chip than my 460 (famous last words.....). If covering a huge field is a requirement to me at some point I will move to a good 200mm Canon lens and cover a *serious* amount of sky

Yes, that's a good way to get a wider field on a smaller chip. Prior to the 11000 that's what I did.

Olly

[mftoet]

A word of caution; the refocus issue and the theory that the 106N is less affected is an 'Olly and Tom' concoction and shouldn't be taken as gospel. We find that our 106Ns hold focus quite well, needing one or two adustments per night. We know this is not true of the ED. Maurice Toet made a video of focus drift in his ED 106. I think, in fact that he made it here, under familiar conditions. So our theory is factually-based but not at all rigorous. Yves, who has had both 85 and 106EDs doesn't buy it, for instance. I'm convinced, though.

The video of subs that shows focus drift over the course of 300 minutes was made on May 23, 2010 at home (Zoetermeer, Netherlands). Here it is:

This was captured through a 7 nm Baader H-alpha with a SBIG ST-8300M behind a FSQ-106ED, 20 minute subs at f/5.

With the small stars you get using narrowband filters, focus (drift) is probably more critical than using LRGB filters.

I had to refocus my FSQ-106ED several times a night. Also when I imaged with it at Olly's. Or at least I checked it every hour or so at the beginning of the night (when temperature drops are often greater).

If I had to make a guess, I think it is essential to refocus the FSQ-106ED every change in (ambient) temperature of 1 ºC, but maybe even preferable every 0.5 ºC. Especially when using it at f/3.6. For me it was the reason to eventually sell the FSQ-106ED. Setting up an autofocusing routine turned out to be not my piece of pie.

Since several months I own an Epsilon-180ED with an even more critical focus zone. Luckily focus drift doesn't seem to be an issue with the Epsilon.

I'm with Olly and Tom that the old fluorite FSQ-106 doesn't seem to have as much focus drift issues as the FSQ-106ED.

[kirkster501]

Such constant refocusing would to me be a complete PITA, especially if it had to be done manually with all the messing about that entails slewing away from target etc.  My £300 SW ED80 with stock focuser (excellent scope) holds focus for hours so I'd certainly want a £3000 telescope to do so. 

[ollypenrice]

Such constant refocusing would to me be a complete PITA, especially if it had to be done manually with all the messing about that entails slewing away from target etc.  My £300 SW ED80 with stock focuser (excellent scope) holds focus for hours so I'd certainly want a £3000 telescope to do so. 

Thanks to Maurice for coming in here. Excellent video.

You have to accept that the faster your F ratio the shallower is your depth of field. The angle of the light cone is steeper so that's that, a geometrical law. Likewise, the smaller your pixels the more critical it becomes. And, though I'm not dead sure about this, I think the larger the flat field the more critical it may be.

However, the ED106 does have an issue, of that there's no doubt. Solutions are to robotize the focus (and if Maurice doesn't fancy it I can promise you I certainly don't!!) and, just an idea, heat the tube routinely. Maybe insulate it as well.

The simpler solution is to go for the less fickle 85 or orginal fluorite 106.

An historical note; the Petzval portrait lens came into AP over 100 years ago. EE Barnard had two, a larger and a smaller. The smaller one held focus better...

Olly

[swag72]

I do find a bit of focus drift on my FSQ85, but this is generally early in the imaging run, even after an hour or so's cool down.

I focus initially using the Bahtinov mask and grabber, do a couple of 30 minute subs, then have a check of focus using Maxim's quality tab in the stacking routine. I then use the FWHM focus method as it's only a tweak, so I don't need to slew to a bright star again for focus. I know now which way the focus has moved and so it's a matter of minute to get it right for the rest of the night. I can then get a 6-7 hour run with focus maintained.

I've also found that running dew bands has helped.