Meade f6.3 reducer working at f5.1?

[rich_t]

Hi,

I recently accquired an SXVF-H9 from a forum member and bagged my first picture with it, had to be M27 at this time of year:)

I'm really pleased with the result but don't understand how I've managed such a big FOV from a 10" LX 90 LNT and an F6.3 reducer. It's quite a nice problem to have though!

Astroart is telling me the horizontal FOV is 24.2 arc mins, which using some calculators on the web means I have a focal length of ~1275mm that is F5.1?

I've read that the reducer to CCD spacing should be 105mm to get down to F6.3, my spacing is ~76mm!

I've also read that that the Meade 3.3 reducer has a focal length of around 90mm and the 6.3 reducer is around 230mm, well mine seems to be at 130mm (I measured my 3.3 reducer at 90mm as expected).

I'm pretty confused by all this and just wondered if anyone has come across anything similar?

Thanks very much,

Rich.

[barkis]

Just be mightily pleased with the result Rich. It is a brilliant Image, and I'll warrant you are over the moon.

Well done. What are the details, how many subs, and at what lengths?

The horizontal size is less than the diameter of the full moon as you know, so not that huge really.

Ron.

[rich_t]

Thanks very much Ron, the LRGB exposures were 15*2min for L and 4*3min for RGB at F5:)

L and RGB all binned 2x as I didn't trust the weather to hold out for long enough for 1x.

If I remove my 30mm spacer I can get to a about F6.8, so I think the 15mm spacer wil be around f6.3ish but not tried this yet.

The reducer seems to work really well, just not the same as other people's.

When I bought it (this was 2006!) I was expecting to be able to use it visually, but couldn't reach focus with a 2 inch diagonal. Maybe that's because of its short focal length compared to the 230mm other people have quoted. I mainly want it for imaging though so not too bothered about this.

Thanks again,

Rich.

[Merlin66]

There was a "bad batch" of x0.63 reducers manufactured where the focal length was around 140mm instead of the design 230mm... sounds like you have one of them!

[rich_t]

Thanks, the "bad batch" at 140mm seems to fit with what I'm seeing, works really well though, not sending it back!

I heard there was some f6.3 reducers made with f3.3 elements, maybe mine's got both f6.3 and f3.3 elements!

Thanks,

Rich.