Baby leaves home...

[ollypenrice]

Well, I've just sold the best telescope I've ever used. This is the little Takahashi FSQ85ED. No doubt the new owner will pipe up joyfully quite shortly and, I hope, like it as much as I did.

It is fast, holds focus, has incredible colour correction, gives tight stars, rarely gives internal reflections or halo artefacts and the resolution is formidable. Mechanically it just works, always.

Why sell it? Because I've swapped over to a full frame Atik 11000 and the little one doesn't quite cover the chip, which is 37mm on the long side and needs a 45.25mm image circle. I've switched to an FSQ106. There is a second reason for this in that we aim to be doing some collaborative projects with Tom, who has exactly the same 106/11 Meg setup so the collaboration will be coherent. Although bigger the 106 doesn't hold focus during cool down like the 85 and seems to get more bother from big bright stars. However, it seems to be a great scope and the huge field is great fun. If ever you wonder if the 85 can possibly be worth the price - it is!

The dew tapes are now the right way round!!!

One from the Baby Q:

Olly

[RikM]

What a wrench to let it go, but I am sure the new owner will see it properly used

[rory]

an amazing image olly .

[swag72]

Well I missed this thread - Welcome to your new home BabyQ!!!!

Now where do I put those dew bands?

[ollypenrice]

Well, it has gone to a good home. Yikes, I really had trouble doing this. I've had so few bits of technology that worked so well. Honestly, the only comparably good bit of kit I've ever had in my life is my long distance touring bike. I designed the frame and had it made by Mercian in Derby. Like the Tak there is nothing about it that I'd want to change, even after an awful lot of time spent together.

Anybody who owns a Ferrari and thinks it compares with a Tak FSQ85 is kidding themselves.

Olly

[fwm891]

perhaps just on price....

[brantuk]

Wish you'd told me it was for sale Olly. I had a bike built to spec by Mercian too (many moons ago). Fabulous bikes they produce - but I was a lot fitter and didn't smoke back then lol

[E621Keith]

...

Anybody who owns a Ferrari and thinks it compares with a Tak FSQ85 is kidding themselves.

Olly

You mean this thing?

http://www.astroshop.eu/william-optics-apochromatic-refractor-ap-70-430-zenithstar-70-ferrari-anniversary-edition-ota/p,8742

I have not doubt the FSQ will wipe the floor with the Ferrari.

I noticed your FSQ106 has blue label rather than red. Is it the older fluorite version?

May be Takahashi fixed the thermal expansion issue in the newer iteration, so your 'newer' FSQ85ED can hold focus during cooling.

[ollypenrice]

You mean this thing?

http://www.astroshop...tion-ota/p,8742

I have not doubt the FSQ will wipe the floor with the Ferrari.

I noticed your FSQ106 has blue label rather than red. Is it the older fluorite version?

May be Takahashi fixed the thermal expansion issue in the newer iteration, so your 'newer' FSQ85ED can hold focus during cooling.

Oh, that Ferrari edition is the kind of thing that really turns me off WO. What is all that nonsense?

Our 106 is the old Fluorite, yes, but I think the thermal instability may well be the other way round. I think the fluorites are less affected, which was one reason for grabbing that scope when it appeared on UKABS. So far it is proving not to need a refocus too often, about once or twice a night rather than between every sub. This is also what Tom O'Donoghue finds with his Fluorite 106. I'm guessing that the 85 holds focus by being smaller. Back in the twenties E.E. Barnard wrote that, of his two portrait lenses (Petzvals) the larger one suffered more focus drift than the smaller. Maybe just a coincidence, though.

Olly

[E621Keith]

I thought thermal stability is related to the thermal expansion of telescope tube (i.e. expand when heater, contract when cooled). It makes sense the 85 have less error than the 106. After all thermal expansion is a percentage change, so the longer 106 should experience greater absolute focus shift then the shorter 85. However, I wonder whether Takahashi has listened to user feedback about thermal expansion in the first FSQ and re-engineered the newer 106ED and 85ED with more thermally stable tube, so the 85 has even less focus shift than otherwise.

I didn't realise the lens temperature can change focal length, learned something new today.

[ollypenrice]

Without doing back to back tests it's hard to know where the problem lies and whether or not the old ones really do suffer less than the new. I've some reason to think that they do, though nothing really conclusive. It's just based on chatting to owners who have used both types here. What I've heard is that the lens spacings had to change considerably when Tak felt obliged to stop using fluorite and that this may be the cause of the problem on the later ones. It may be the lens cells rather than the tube itself which does the expanding and contracting. So far as I know Tak haven't done anything about it. Rectifying issues in their designs isn't one of their strong points! (They went on shipping their very expensive mounts with Pegasus, the worst planetarium software since Ptolemy, and have only recently pulled themselves up to scratch on this.) They're a very conservative firm. The manual that came with mine says that I should expect focus drift during initial cool down of half an hour. The implication is that then it will be stable - but I doubt it will be totally so. For all that, its mighty sharp and easily covers the 11000 chip. That's the main thing. My sampling rate is 3.5 arcsecs per pixel so there's some tolerance built in there.

Olly

[Earl]

Personally I would of gone for a different camera

[ollypenrice]

Personally I would of gone for a different camera

It certainly crossed my mind but I'd hoped the 85 might cover the chip. What camera would you have gone for? The 8300 is 19.7mm x 15.04mm which is less than a third of the size of the 11000 by area. Using the reducer the FSQ85/8300 doesn't cover all that much less sky than the 11000 in the 106. It's 10.14 square degrees versus 7.7 square degrees. It would be interesting to compare the FSQ85-reducer/8300 with the FSQ106/11000 on the same target. You have optical resolution and pixel resolution in play. There's no way in the world I'd really trust a theoretical comparison. I'd want to see the pictures. However, I'm going to bet that FL530mm is going to out resolve FL328mm by quite a lot. The sampling rate is nearly the same in both, 3.4 versus 3.5 arcsecs per pixel in favour of the 85/8300.

Another reason for the change is planned collaboration with Tom's FSQ106/Atik 11000. Two identical rigs make sense.

And finally an 8300 chip at F7 and 1.89 arcseconds per pixel in the TEC140 might be a long slog. I have to bear that in mind.

What I will say, though, is that an 8300/FSQ85/focal reducer is going to be a storming widefield setup. I'm not going to knock it!

Olly

[Earl]

What I will say, though, is that an 8300/FSQ85/focal reducer is going to be a storming widefield setup. I'm not going to knock it!

Olly

Thats where id go, only quest is which camera, id really like it all in the one box, less faffing.

[ollypenrice]

Thats where id go, only quest is which camera, id really like it all in the one box, less faffing.

In that case QSI? The electronics are excellent, the quality and cooling ditto. Expensive, though.

Olly

[Chris]

End of an Era.

I look forward to seeing the fruits of your new venture though:)

[ollypenrice]

End of an Era.

I look forward to seeing the fruits of your new venture though:)

Just waiting for the Milky Way to rise and we'll get cracking!

Olly

[martin_h]

Thats exactly why I got the WO ZS71 - reduced to f4.7 with the 8300 - QHY chip. Just waiting for Cygnus to rise a bit earlier.

[opticalpath]

Thats where id go, only quest is which camera, id really like it all in the one box, less faffing.

I'm very happy with my QSI 583wsg .... with its built-in filter wheel and OAG - that's 'all in one box'!

Adrian

[gingergeek]

Sara,

Well done there, it is in good hands......you certainly kept that quiet !

GG

[swag72]

Sara,

Well done there, it is in good hands......you certainly kept that quiet !

GG

[E621Keith]

Sara,

Well done there, it is in good hands......you certainly kept that quiet !

GG

Congratulation on your new scope.

What's it like compared to your Pentax 75?

[swag72]

So far, the only complete data I have is some luminance on M101 and I'm very happy with that. It's a lovely scope that's for sure.

Compared to my little Pentax ......... seems an unfair comparison to make in my heart The Pentax gave me some cracking data, as will the BabyQ!

[mftoet]

May be Takahashi fixed the thermal expansion issue in the newer iteration

No, they did not. I've owned a Takahashi FSQ-106ED for several years. Excellent astrograph, but I sold it because of the temperature-focus-shift issue (you have to refocus when temperature drops 1º C, maybe even every 0.5º C).

Here you can see an animation of the focus drift during 5 hours (without refocusing) with the FSQ-106ED and ST-8300 + 7nm Ha filter. I haven't record how much the temperature dropped during those 5 hours, but probably not more than 1 degree/hour.

[E621Keith]

So it sounds like the FSQ85 is the one to go for if you want a trouble free imaging scope.