Optimal FF for a scope

[NickH]

Research is all pointing towards a TV0.8X FF for the TMB 105/F6.2, but anyone got any actual data on which is the best one as there appears to be a few, two of which optimised around the kind of aperture

Tele Vue Optics Article Page

This optimal 55mm distance they quote, with an APS sized sensor, and an Atik motorized wheel in place, any thoughts?

TIA for any advice... if you have one, and use it with the FF and a large sensor, can you post up image results?

[SteveL]

Hi Nick

Two pane mosaic, taken with SX M25C on William Optics FLT98CF with TV TRF2008 FF/FR.

More details on my blog entry >> HERE <<

[NickH]

Thanks Steve

Settled then...bidding on one now!

[ollypenrice]

Great reply, Steve. End of conversation!!

Olly

[NickH]

Yes...superb reply...a picture does paint a thousand words...

That's why I love SGL...no matter what end of the spectrum, someone has an answer...a superb resurce

[SteveL]

There was *SOME* very slight coma in the very corners, but you really had to zoom in to see it, and I am sure it was just a case of fiddling with that +/- 2mm (or maybe a bit more) to get rid of it.

Sadly, not having on obsy to speed things up, I just didnt have the time to waste with that fiddling on clear nights when I should be imaging, so sold the FLT98 + TRF2008 and got the Borg77 instead.

[NickH]

Steve/Olly

I am now trying out an actual TMB F6 optimised FF.. will let you know how that goes...still looking for the Televue one, but will give this a blast first. Still may end up with the TV one...but thanks again for your input

[SteveP]

Nick

Having now read the TV article, I'm surprised that there is such a thing as a generic flat fielder. I'd always assumed that the FF design was to counteract the specific characteristics of the scope and was therefore specific to the scope (or at least manufacturer) I suppose they could provide such a high level of FF that it's not discernible except under high magnification. Steve's image seems to contradict my undeestanding very graphically

The backfocus of 55mm for the TV FF doesn't seen overly generous. I don't know the specific dimensions of your kit. Assuming a FW of say 25mm and a CCD distance of approx 20mm it still leaves a little bit for adapters etc so should be sufficient. I suspect you need to doublecheck your own kit's measurements

HTH

Steve

[SteveP]

There's also an interesting thread on Cloudy Nights which compares 3 FF's (TV, WO and AstroTech) and concludes that the TV TRF worked best in the writer's setup

[NickH]

Thanks SteveP

I have now secured loan units for the TMB and the TV TRF, so can compare and see which works best...again to everyone who helped, thank you so much