From: Alan Friedman <alan@greatarrow.com>

Date: July 25, 2006 10:34:19 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: stacking and histogram questions

Hi Eric -

I find it difficult to evaluate the brightness of the image at night. The image on the computer screen always looks very bright in the dark - but the video can appear too dark when viewed during the day. In my experience, as long as you can determine that you are not clipping the image on the high end, the brighter the better.

That's a very nice lunar image.

best,

Alan

Hi Milton,

Yeah, I know the feeling about slow speeds as I related before. Must switch to DSL or something soon.

Thanks for the advice. The biggest problem I've been having is that most of the movies I recently captured were all too dark. During post-processing, I have to readjust the histogram quite a lot to get the brightness back to normal. No doubt this is causing a lot of problems. I'm not entirely sure how to properly read the histogram as movies are being acquired. As I mentioned, if I increased gain too much, the histogram would appear jagged. I would then reduce but this made everything dark come to find out later.

Eric

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

From: Milton Aupperle

To: Astro_IIDC@yahoogroups.com

Sent: Monday, July 24, 2006 11:06 AM

Subject: [Astro_IIDC] Re: stacking and histogram questions

Hi Eric;

I'm on vacation, communicating via a 2600 baud modem, so getting

e-mails is a major pita.

Astro IIDC will reject frames if they exceed the matching tolerance

that you specify. Even if you pick 0% (ie all frames) of the

histogram, it may still reject frames that simply don't match based on

your tolerance setting.

Part of the issue sounds like you have your gains cranked all the way

up. So when it trys to match up one frame against another it may wind

up just matching noise for low contrast areas.

I'm working on changes to selectively allow smoothing of the images

before doing sharpness and alignment (likely a 1 or 1.5 pixel radius

gaussian blur) which should drop the noise level a lot and remove the

noise.

HTH..

Milton Aupperle

--- In Astro_IIDC@yahoogroups.com, "Eric" <eddot1103a@...> wrote:

> Hi,

> During my laborious processing of various streams, I notice that

IIDC sometimes doesn't stack all of the frames I originally picked.

This has happened for both lunar and planetary sessions. I noticed

with Jupiter that I had to prealign in KIS first before IIDC would

accept all of my hand picked frames. With the moon, if I try

prealigning first, in IIDC it doesn't align them well at all

presumably because KIS allows the black edges to remain if it realigns

a frame. Is there anything I can do in IIDC to get all hand picked

frames stacked? I've had confidence at 0 (because they are hand

picked) and I have tried various matching, but still a certain number

of frames are excluded.

> I'd appreciate any histogram suggestions. Maybe because my monitor

was incorrectly adjusted, not sure, but a lot of what I captured

recently came out with very low gains, to the point where I have to

significantly adjust the histogram of the final stack. During

capture, I had the histogram enabled and adjusted gain until the curve

was "pure" without jagged lines. If I continued to increase gain, I

would get a jagged histogram but not saturated. Can I risk running

the gain where the histogram shows jagged lines and what do the jagged

lines (within the histogram curve itself) indicate? Not talking about

saturation here, just an "impure" looking histogram during capture.

> Sorry for the long questions, but appreciate in advance any

suggestions for the above.

> Thanks,

> Eric

__._,_.___

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