From: "Milton Aupperle" <milton@outcastsoft.com>

Date: April 11, 2009 9:36:48 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: Meade f3.3 FRs...

Mark;

You can' remove "Black Edges" with Flats (note I said BLack not Gray or slightly darker, BLACK). In fact, if you have more than about 20% brightness variance across the field, you should fix or reconfigure the optics as your likely going to get very poor results.

And since the Guide Prism will be in the "Black Edges" area, you get no light there, which means you are much more limited (likely only 4th mag stars) in what stars you can use for the OAG.

And it IS a big deal, if your losing 20 or 30% of your field of view due to vignetning with a 640x480 pixels, that's a lot of pixels lost.

But do what you want, it's your money.

Milton Aupperle

--- In Astro_IIDC@yahoogroups.com, Mark Gaffney <markgaffney@...> wrote:

Milton, It says in the "Dome Flats" section of the linked article that

vignetting is present & that a shadow was cast on the chip but

that..."In practise this isn`t a huge deal as it is only on the upper

5% of the image & can generally be flat fielded out without a

problem.." This is surely a good application of your "Flat Frame

Correct Movie" option, although obtaining a flat frame the same size

as the movie in question may be difficult- I don`t know- I was hoping

you`d have some insights..! As for the back motion, can`t this be

solved by having an extender tube on the nosepiece of the imaging

camera as I`ve already been using with the Flea 2 & the f6.3 FR? You

may be right I`ll have further problems with co-inciding the focus of

the 2 cameras? I was going to buy one of these f 3.3 FRs to experiment

with it unless I heard a good reason I`d be wasting my money & I think

the expenditure going on these parameters (above) may be OK after all.

I guess I`ll never know unless I try it in practise! Mark.

On 11/04/2009, at 6:38 AM, Milton Aupperle wrote:

Mark;

On 10-Apr-09, at 10:21 AM, Mark Gaffney wrote:

Hi Milton, following on from my message to you privately today I`ve

been re-investigating f3.3 focal reducers. I got a good deal of

advice on these on the SCT user group a while ago & I think the

consensus was that the new version of the Meade f3.3 FRs were OK

but the older version was a bit suspect?I may have it the wrong way

around. I`ve been looking at this link I believe you sent me;http://benedict.isomedia.com/homes/cvedeler/scope/focal_reducers.htm

This is the place I got my Antares f6.3 FR & looks like a good deal

for them; http://www.agenaastro.com/Meade-f-3-3-Focal-Reducer-and-Variable-T-Adapter-p/ofr-me-3.3fr.htm

What do you think? Mark.

What do I think? About what am I supposed to offer an opinion on?

Pricing?

It's pretty clear the drop off on the edges of a F3.3 adapter is

excessive, and you get a lot of distortion too. And you may not have

enough back motion to get both cameras into focus. Lasltly, the drop

off on the edges will negatively affect the star brightness of the

Pick Off Prism on the OAG too for an F3.3.

Hope that helps..

Milton J. Aupperle

President

ASC - Aupperle Services and Contracting

Mac Software (Drivers, Components and Application) Specialist

#916, 742 Kingsmere Crescent S.W.

Calgary Alberta T2V2H8

1-(403)-453-1624

milton@...