Question concerning field flattener for WO Z73

[Sam255]

Hi,

I am currently planning on buying a William's Optics Z73 Refractor to use as my main imaging scope, with a crop-sensor Nikon DSLR (D7200). While looking at a field flattener to use on the setup, I realized that the William's Optic 73A field flattener is sold-out in every stores around. I was wondering if it was possible to use another field flattener, like the Explore Scientific 2'' (https://www.otelescope.com/store/product/3035-explore-scientific-2-field-flattener-for-ed-apo-es-ffedapo-00/) , which seems to have the same size and fitting as the other one, and seems to allow for the same 2'' filters. It doesn't say anything about compatibility with other brands, but I am curious to see if it would still be a good fit.

 

Thanks in advance,

 

Sam

[Crackabarrel]

I can't speak as to whether it would be compatible but First Light Optics seem to have the adjustable version in stock on their website.

I've been using this one on my own Z73 and it works very well

[jimjam11]

Both are in stock @FLO and they are both very well made; I would not buy a non-WO flattener for this OTA given their availability.

I have both the Flat73A and Flat73R. When I got my ZS73 there was no reducer option available but I got the reducer version once it was released. With the Flat73A I configured it to the WO backspacing (11.4mm IIRC) and never touched it again. It gave perfect stars from corner-corner. The Flat73R gave me the run-around and when I first used it my stars were terrible. WO do not publish spacing guidance for dedicated cameras and I had to find my optimum by trial-error. They specify 1.8mm for DSLR and mirrorless but with my ASI1600 I have ended up somewhere around 2.7mm. Despite this the field is not as flat as the Flat73A, but it is significantly wider (With my ASI1600 it works out as 443mm vs 346mm or 1.77"/px vs 2.26"/px).

I have not sold the Flat73A yet because it definitely works with a full-frame sensor; there seems to be ambiguity around the Flat73R. Initial material implied it was full-frame compatible, but the WO website now claims it is optimised for ASP and smaller and I am not convinced it would produce an acceptably flat field for a full-frame camera.

 

[TerryMcK]

I also have the ZS73 with the adjustable field flattener and wouldn't consider anything else. As JimJam say they are in stock on FLO and are a doddle to install/setup.