new scope has arrived!

[monoxide]

meet the latest member of the family
a shot with the dew shield retracted/extended and of course the clouds..

very impressed with the build quality of the scope too!
now i just need a side by side plate and dew heaters (and some clear skies)

anyone got some tips about what dew strap id need? if it went around the tube behind the shield then its a fair way behind the objective but theres an air gap between the cell and the dew shield
i get the feeling a heater behind the cell on the tube could result in tube currents but a strap on the dew shield may not be effective with the ~10mm air gap?

the OD of the tube is 114mm but the OD of the dew shield is 145mm so i dont know if i could get one that would fit both spots just to see what worked better and i dont want to end up with one thats not going to get used

[Bassnut (Fred)]

umm, is that a Tak FS102? (guessing, based on yr sig)

[monoxide]

whoops, yep its the FS-102NSV
i still have to get some rings for it too. i think it will be a bit more stable than the small footprint of the clamshell..
more $$

[Bassnut (Fred)]

Top purchase, should be razor sharp, interesting to see the diif between that and the ED80. The dew strap would be better just short of the shield IMO, I dont think tube currents would be a prob, its minor compared to other thermal effects. BTW, the OTA and guide scopes shoud both have heaters, they have velcrow strips, and can adapt to a wide range of ODs for experimentaion.

[Ian Robinson]

Green with envy.

Did you get the reducer / field flattener too ?

[monoxide]

thanks Fred, i never really had that much of a problem with dew and never worried about a heater for the ED80 although its a nice scope i wasnt that worried about it dewing up/drying out but the tak is another story.. id really like to keep it dry.
ill be getting heaters for both refractors and a 2" strap for ep's

no reducer yet Ian, the 820mm focal length is something that im really looking forward to but it is on the long list of things to get
i dont think ill see any major problems with the QHY8 but with a 35mm sensor it would probably be a different story, guess ill wait and see.

[Lester]

That is a good purchase.

I have a similar Tak and dew isn't a problem, but that is in a observatory.

Better to be safe than sorry, go for the heater if you experience high humidity.

[Alchemy (Clive)]

youre going to love it, ive never heard anyone complain about the quality of a tak.

[monoxide]

just had a quick look at joop through some thin cloud
the focuser is pretty nice, mabee a little stiff but joop just snapped into focus. no searching back and forth at all.

unlikely ill get a much better look tonight or even for the next week going by this:
http://www.bom.gov.au/products/IDE00902.loop.shtml

to say im looking forward to imaging through it would be an understatement

[Rigel003 (Graeme)]

I've had my FS-102 for nearly 5 years and done lots of visual work and deepsky photography under all sorts of conditions but have not once needed a heated dew strip. Bought one originally and have never connected it. The dew shield is enormous and does its job well.

[Ric]

Congrats Tj, that is one mighty fine looking scope.

Your going to get many years of fine viewing and imaging with that little beauty.

[PCH (Paul)]

Hey Tj,

looks fabulous ! Is there a TAK distributor in Oz? If not, where did yours come from?

Cheers,

[avandonk]

Optics get below the dew point by radiative cooling. That is they lose heat by radiation to a sky which has a temperature of 3 degrees Kelvin. All the dew shield does is limit the amount of sky the optic can 'see'. By very gently heating the dew shield it will then radiate to the optic so counterbalancing the heat loss to the sky. The last thing you want is heat to conduct to your optic. This will distort its figure.

With that out of the way very nice telescope. It does not get much better than this at this aperture. I am sure your joy with its use will be greater than my/our envy.

Bert

[Miaplacidus (Brian)]

I don't know about that, Bert. My envy is pretty goddam high!

Congrats bout the scope, Mr Teejay.

[monoxide]

thanks guys,
no need to be jealous
will probably be a while before i can give it a decent first light to give it a bit of a workout.

Rigel: not wrong mate the dew shield is huge! ive had a few nights of really heavy dew here though where even the mount was dripping, plus im worried if im imaging around zenith that the dew could 'fall' onto the objective

Ric: thanks mate, ive always wanted one of these lil beauties so its great to finally have one and i cant wait to get out there with it

PCH: AEC is the aussie Tak dealer, when i ordered mine they only had 2 of these left and im pretty sure the fluorite scopes arent being made any more by Tak

Bert: thanks for that, i was thinking something similar lastnight. i remember seeing somewhere that the goal isnt to actually heat the objective but the air infront of it.

[Ian Robinson]

Originally Posted by avandonk

Optics get below the dew point by radiative cooling. That is they lose heat by radiation to a sky which has a temperature of 3 degrees Kelvin. All the dew shield does is limit the amount of sky the optic can 'see'. By very gently heating the dew shield it will then radiate to the optic so counterbalancing the heat loss to the sky. The last thing you want is heat to conduct to your optic. This will distort its figure.

With that out of the way very nice telescope. It does not get much better than this at this aperture. I am sure your joy with its use will be greater than my/our envy.

Bert

I believe it's a very good idea to keep fluorite optics dry as they are susceptable to pitting if wet, the CaF2 is slightly soluble in water.

Probably a good idea to use the demister.

molar soubility is 1.24 x 10^-3 at 35deg C.
Ksp = [Ca2+] [F-]^2
= x ( 2x)^2
= 4x^3
= 4 ( 1.24 x 10^-3)^3
= 8 x 10 ^-9

[wavelandscott (Scott)]

Congrats on the new gear and add my name to the "envy list"...My shade of green is not quite as dark as forest green...