From: "Alan Friedman" <alan@greatarrow.com>

Date: April 12, 2007 9:55:34 AM MDT

To: <Astro_IIDC@yahoogroups.com>

Subject: Re: [Astro_IIDC] Starting Out and Would Appreciate Camera Advice

Reply-To: <alan@greatarrow.com>

Hi Doug -

The solar work I have done has been with a 640x480 chip with full disk images

made with mosaics (the number of panes varying with the focal length - I can

mount my 90mm filter to achieve native FL as short as 450mm and as long as

1100mm). You can see some of my solar work on my website:

http://www.avertedimagination.com/

A larger chip would be an advantage in low resolution full disk solar images. The

lower the magnification, the less seeing will be a factor. At higher

magnifications, a large chip will have a small area of sharp focus even if the image

is on band across the field, due to the funky daytime seeing conditions. The

biggest problem with full disk images (from my very personal opinion, of course) is

that they become a bit of a bore over time. Zooming in on solar features helps you

to enjoy the ever-changing dynamics of the sun. As you increase resolution, seeing

becomes a big factor and the shutter and capture speed become much more

important. Often seeing will make it futile to average frames together - the

sharpest image will come from a single frame. Fortunately, the sun is bright and

there is enough signal to make this possible.

My recommendation would be to start with a 640x480 chip and exhaust the

limitations of this format. The DMK 21AF04 is a good place to begin. I hope to

have an early copy of Paolo's camera to test with Astro IIDC shortly and will report

back to the group on how this works.

look forward to seeing your solar images,

Alan

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

From: "Doug" <dwd3m@virginia.edu>

Reply-To: Astro_IIDC@yahoogroups.com

Date: Thu, 12 Apr 2007 14:27:29 -0000

Hello Everyone - I would like to start solar imaging in a serious way (up until now

I have

just been capturing video with Meade EEP and A to D converter). I just joined this

group

because I plan to use Astro IIDC and I'm now shopping for a suitable firewire

webcam. I've

searched this and lots of other forums, checked out manufacturer's sites and

camera

specs and now I've reached the analysis paralysis stage - I'd be grateful for some

help at

this point. Sorry if the post ends up a bit long....

I am reasonably familiar with digital imaging and processing because aside from

being an

avid amateur photographer, I use cooled CCDs for low-light microscopy in my

day job. I

should qualify the latter; I direct a lab where others far more knowledgeable

actually do

the hands on work but I make the purchasing decisons and criticise the output,

LOL.

In any event, my sole astro-imaging interest at the moment is H-alpha (and CaK

to lesser

extent). The camera I purchase will be dedicated to this task so I'm looking for

the "best"

camera for the intended application, not necessarily the most versatile. I will be

using

primarily a Solarscope SF70 (70 mm) F-P etalon attached to a TV 76 refractor. I

would also

prefer to stick with a non-tracking alt-az mount for the time being unless

someone tells

me this is definitely not the way to go (I'm assuming image shift over a few

second capture

period can be handled by registration/stacking software). Finally, I am very

interested in

being able to image the entire disc with little (or possibly) no stitching. BTW, the

SF70

gives remarkable on-band performance across the entire disc without any

detectable

"sweet spot".

I'm thinking larger format chips (1/2-3/4") would suit my needs best and with a

telecompressor would give me a big chunk of the disc through the TV76 (480

mm w/o

reduction). However, I don't know how to gauge whether the frame rates are

good

enough. 15 fps seems pretty fast to me for an application where I'm not really

light limited

(i.e., solar) but maybe I'm wrong about this? I know capturing even 15 fps full-

res with the

largest webcam chips would tax the cpu but don't have a feel for how a current

Macbook

(pro?) running ASTRO IIDC would handle the data stream (via firewire).

As for cameras, I've got the following short list - monochrome of course: DMK41

series,

PGR Flea2 (wondering about Optronics but haven't priced yet) or waiting for one

of Paolo

Lazzorotti's cameras, which seem promising at the specs currently listed. I take

Lumenera involves too many headaches for use with a Mac?? Should I not be so

wedded to

the idea of larger format at the expense of fps? I'm not so concerned about

resolution but

my feeling is that if the cpu can handle the data then why not higher-res?

I wish I could grab one of the >$15k cooled large chip CCDs on my microscopes

outside

for a try but alas, I cannot...

thanks for any advice or suggestions,

Doug