friend's new Apo , 2nd report

[brian nordstrom]

I have had the Honour to be asked to test a friends new ,, ( design and build ) 'Sky Rover' , 115mm f6.9 fluorite triplet , Ouch!
Some here know we did a peliminary test 3 weeks ago using my Takahashi 'SKY90' 90mm f5.5 fluorite doublet .
Not a test of aperture.
A test of 'Fluorite' .
This 115mm passed with flying colours , nice crystal.
The night was one of those very few perfect nights .

ff. 3 weeks .

. last night we tested the 115mm triplet for 'resolution' on the 1/4 moon against my 127mm f8 Istar doublet achromat.
So much fun , report coming but here is a photo .
Last nights seeing was 'fast moving atmosphere'.

Brian .

[JQ]

Hi Brian, I look forward to your second review. I have just purchased the Sky Rover 115 from Astronomy Alive. I was impressed by the specs and look forward to first light.

[LewisM]

The fluorite Sky Rovers were discontinued some time back (last year), replaced by ED glass instead, and Lanthanum in the larger models.

[gregbradley]

I was going to ask if this was genuine fluorite as some manufacturers (notably William Optics) call FPL53 fluorite. FPL53 has a lot of fluorite in it but its deliberately misleading. Fluorite lenses have less scatter and enable the optics designer to achieve a faster F ratio with better colour correction as with TEC fluorite scopes. If you look at the strehl for different wavelengths the fluorite models seem to do better. Fluorite has less light scatter as well if you do the green laser test where its invisible when it goes through the fluorite element but you can see it in the other lesser glass elements.

So if there is any doubt shine a green laser through it and see if you can see the beam. If you can its not fluorite.

Greg.

[LewisM]

Brian did the test before and said that the green laser was invisible.

I wonder why the switch was made to ED glasses for these? Perhaps Fluorite just was not economically viable or too difficult for the Chinese opticians to figure properly (even Roland dislikes pushing fluorite and most optical factories are NOT capable of figuring fluorite). Perhaps they WERE finely figured FPL53 (fluorite enriched glass)- if I shine a laser in my Takahashi FPL-53 objective (FSQ-106ED), I have a VERY hard time seeing the green laser. Yes, William Optics and some others copped some real flak about calling their telescopes fluorite when they most assuredly were not CaF2 crystal but FPL53 instead. It was a marketing ploy - pure and simple.

What matters is how they perform.

The lanthanum glass variety sounds interesting. I have a genuine love of the Vixen eyepieces that use lanthanum.

[gregbradley]

Yuri at TEC likes using fluorite. I suppose its what you get used to and it probably behaves differently when being ground.

Sounds like a hot little scope if its genuine fluorite triplet. Wow, that would be rare company. TEC110 is the only other fluorite triplet I am aware of in that size. And that was a GREAT little scope. Possibly one of Yuri's finest.


Greg.

[LewisM]

Has Yuri ever done anything the easy way? :)

[JQ]

Brian, Could you use a Naglar 31mm in the Sky Rover 115 successfully?

John

[brian nordstrom]

Yes ,:thumbsup::thumbsup:. Yes and yes no problems there , I dont own a 31Nagler but have the next best
thing , Celestron,s awsome 31mm Axiom , and the views thru Brians 115mm SR were just amazing , hope he see,s this and chimes in .

Views were amazing , wall to wall perfect stars as only a quantity APO can show .

Brian.


QUOTE=JQ;1203455]Brian, Could you use a Naglar 31mm in the Sky Rover 115 successfully?

John[/QUOTE]