From: "Eric" <eddot1103a@mindspring.com>

Date: July 8, 2006 12:46:56 PM MDT

To: <Astro_IIDC@yahoogroups.com>

Subject: Re: [Astro_IIDC] questions about sharpening before/ while stacking and IR pass filter

Hi Milton,

Sorry I didn't reply sooner here.  I don't know the response of the IR filter, but it doesn't seem to be very broad.  I too have an RGB set of Edmund filters and I find that they have the highest transmission of any of the RGB filters that I use.  Of course, they aren't IR blocked, but the red filter passes both R and IR and has been very useful for me in the past.  I think I'll stick with that one and send back this IR pass filter. 

Thanks,

Eric

----- Original Message -----

From: Milton Aupperle

To: Astro_IIDC@yahoogroups.com

Sent: Tuesday, July 04, 2006 12:43 PM

Subject: Re: [Astro_IIDC] questions about sharpening before/ while stacking and IR pass filter

Hi Eric;

On 4-Jul-06, at 10:14 AM, Eric wrote:

> Hi Folks,
>
> Well, the holiday and some brief periods of fair seeing has given me a
> chance to try out the DMK camera with IIDC. I like the setup and
> it should
> work well in the future :).
>
> I wanted to ask about sharpening before or while stacking. There are
> various degrees of sharpening, including noise reduction, available
> in IIDC.
> The manual shows the differences. I was wondering if anyone else
> regularly
> uses this presharpening and what benefits does it have?

Probably just me :)

> Also, the IR-780 IR pass Schuler filter definitely didn't seem to
> be the
> right choice. It significantly dimmed targets over any of my other
> filters,
> including blue. Therefore, I'm going to exchange or return it if I
> can find
> out the correct spectrum of the filter I need. Anyone know which
> IR pass
> range or filter offers the best transmission? (Alan, I must have
> been wrong
> in assuming you had the Schuler IR-78)

It sounds like the filter has poor transmission accorss the board
spectrum wise.

What does the spectral curve for the filter look like? Basically that
shows the light transmission percentage on the vertical axis and the
blue to red spectrum (low nm to high nm) on the horizontal. That
should tell you how much light it filters out.

I replaced the original IR filter that shipped with my Flea Color
Camera with one from Edmund Optics (this voids the warranty on the
camera). The original Flea Filter was transmitting less than 40% of
the light at 640 nm, 10% at 656 nm ( which important for H-alpha
emissions from Nebulas) was down to almost zero by 700 nm. The
Edmunds filter transmits about 80% at 656 nm, 20% at 700 nm and is
basically zero at 740 nm. So it's giving me a lot more light in the
Astronomical spectral areas I'm interested in, especially for Nebula
shooting. Some day I'll measure it.

HTH..

Milton J. Aupperle
President
ASC - Aupperle Services and Contracting
Mac Software (Drivers, Components and Application) Specialist
#1005 - 815 14th Avenue. S.W.
Calgary Alberta Canada T2R0N5
1-(403)-229-9456
milton@outcastsoft.com
www.outcastsoft.com