Given the success of the redcat51 + AZ GTi experiment, I'm considering raising my game and look for something in the 400-450mm focal length range that is not very heavy. I'm considering expending 500-900€ (flexible, but definitely below ~1000-1100€) for that.
- 400-450mm focal length. Shorter would make little difference with the redcat, longer may be hard to guide/ride mainly with the AZ GTi (I have also a NEQ6 at my hometown, but it will mostly go with the AZ GTi).
- Decent color correction: I was thinking on either a triplet or a FPL53+lanthanum doublet.
- Full frame coverage (flat, no extreme vignetting, no color kinks).
- I need something to be able to use filters, ideally in a configuration similar to the one of he redcat51 (inside).
- Around F5.8-F6.6
- Ideally no flexure (I experience that sometimes with the redcat and the 70-200 F4 and it is a bit annoying).
I have the possibility to order here in Europe and also in the US in one month.
So the candidates I was checking are.
- Lacerta 72 f6, 2.5kg. 629€ Pros: Really inexpensive, Cons: FPL53+NBM51 seems to be inferior to FPL53+lanthanum.
- Evostar 72 f6. ~350€. Ok, this one is absurdly cheap for a FPL53+Lanthanum. Where is the trap, no Full Frame due to the 2-inch focuser?
- TS 72 f6, 2.2kg + ??. 529+165€ (with the TS 1.0X flattener). Pros: FPL53+Lanthanum.
- AstroTech 72 f6, Not sure if it is equivalent to the TS or the Lacerta. Does it use NBM51? Lanthanum?. Inexpensive, 2" focuser. I would need to find a 1.0X flattener. No FF due to 2" focuser?
- WO ZS73. Virtually identical again, but not sure if it uses lanthanum. More expensive than the previous ones but the nice WO finishing and dedicated flattener.
- TS 70mm f6 triplet: Does not show up anymore in the TS webpage, but still can be found elsewhere.
- GT71. f5.9 triplet, but the dedicated corrector is a reducer and leaves a focal length that is not very different than the redcat's one.
- TS71SDQ. f6.3. I don't really know how to read the spot diagrams, but it doesn't look to be super great. Is it just a doublet + corrector? The advantage is no playing with distances.
- Sharpstar 71. f6.3. The same as before.
Any opinion? suggestions? recommendations? I am open to other brands of coruse, but only if they pouring money to just buy the brand.
Edited by elakrab, 19 September 2019 - 03:39 AM.