From: Alan Friedman <alan@greatarrow.com>

Date: October 21, 2005 3:06:08 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Grid Pattern

Hi Duane -

On Oct 21, 2005, at 3:05 PM, Duane wrote:

In any case, can you give me the low down on how you process your images—if you let

those trade secrets out :)

Here are a few questions I have, How long can you get away with shooting before the

globe turns enough to smear the image?

This depends on the focal length of your set-up and the resolution that the seeing will allow - but in general, 3-4 minutes for mars. There are a couple of considerations here - also related to your question below. You do not need high resolution in the RGB image if you a using a luminance layer for the detail. The albedo details are visible in R and G but hardly at all in B. So there is some fudge in the above formula - if you shoot your R and G streams within 3 minutes you should be OK if the blue goes over a bit.

How long do you take of each R, G B, L?

I capture 1200 frames in in red, 1000-1200 in green and 600-800 in blue. I have used both 33ms/ 30fps and 66ms/15fps exposures. It is easy to capture 1200 frames in each at 30fps - a bit of a stretch at 15fps. My most recent images use a shorter f-ratio making good s/n 33ms exposures easier with my 10". My yield out of these numbers is 150-200 frames/ stream in poor-fair seeing, 200-300 in fair-good seeing. I only get seeing better than fair-good in my dreams. I make my luminance from an average of R&G so it uses 500-600 frames. The number you need will depend on the s/n of the individual frames which will depend on the shutter/gain settings you use. There are a lot of variables to play with!

When you hand pick your images, do you use quick time pro or something else? (or is

there a way to do that in Astro IIDC?)

I use Keith's Image Stacker if I am going to hand select and align. My recent images of the dust storm have used AstroIIDC for stacking and aligning - it works very well, especially with smaller disk sizes (150-175 pixels). I will post a comment I made to another group here after I send this email that might offer some useful thoughts.

Any focusing tricks that I don't know about? There seems to be a lot of play between focus

and not focus.

A good focuser with zero image shift is ideal. Focus gets harder as the image size imcreases because you lose contrast and sharpness. For this reason a smaller image size might be the right way to go (f30, say) unless the seeing is very good.

Alan

Milton,

In the graph that comes up for choosing the confidence %, what does the vertical axis

represent?

It would be nice... advice is always so easy to give :) ...if Astro IIDC could open the

quicktimes to hand pick out frames (if I didn't overlook that it does already) for stacking.

Glad to hear you got your drive going. That would be a pain in the butt. It's bad enough

that my Meade swings back and forth from periodic error. Once I get the mean of the

swing in the center of the frame it's OK as it just swing back and fourth over about a

minute. Until I find that center though, I have to keep nudging it as guide speed until I find

the sweet spot.

The Unibrain also has a vertical bar that takes up about 20% of the screen that has a

different pattern to it. I tend to stay away from that spot. Can't wait to try out the new

camera. I got the color wheel from Apogee. Seems a pretty good deal. I'm happy with the

quality. I had to get a C-mount adaptor because they didn't have a camera in stock with

the 12mm thread. I also had to get the +$100 trigger camera because they didn't have the

trigger-less model in stock. Oh well. If I can get a few more good shots of Mars, I'll be very

happy.

Next mission, Saturn!

Duane

PS. This is so much fun!

--- In Astro_IIDC@yahoogroups.com, Alan Friedman <alan@g...> wrote:

> Yowee, Duane - you went to school and graduated all in one night!

> Excellent mars image.

> best -

> Alan