Basics for Deep Sky imaging

Just wondering if someone wants to offer up a basic walk through for getting decent Deep Sky images.
Let me give you an idea of what I'm after and the set up I'm going to try.

From the ground up,
Manfrotto Pro DBX tripod,
410 geared head,
Astrotrac,
410 geared head,
ETX-125 OTA,
Canon 350 D unmodified.

This setup gives around 3min accurate tracking
with less than 3 arc min drive error.

Say for example I were to shoot M42.
What length of exposure along with ISO setting should I use
and how many shots?
I read things like, darks, flats, subs etc,
I have a basic rough idea of what is to be done but still not 100%.

Any help appreciated.

Ironically enough,
This morning I got in the post Gerry Lodrigusss CD book
(which I mentioned in the Media section) which explains the
basics of DS photography fantastically.
So now insted of kind of sure I am very sure what ye are on
about when ye are talking about Subs, Darks, Flats etc blah..
Sometimes the technobabble is half the battle!

So anyway,
still,
if any of ye Deep Sky nuts want to offer any of your advice
I'm still all ears.
Thanks.

Frank - I'm assuming you're talking wide-field deep sky? Rather than narrow-field deep sky...

Anhow, I can't help you on ISO settings etc but calibration frames are easy enough:

1. Take darks (as it suggests, frames that are taken when no light enters the imager) at the temperature and exposure duration of your light images. Take at least 20.
2. Take flats - this is where your imager is illuminated by a uniform light source. Hard to do but try twilight flats, they're ok. Or even T-shirt flats. Must be taken at the same focus position (or very close to) that used for your light images. Exposurre duration is based on the saturation point of your CCD chip. Take flats so the chip is at no more than about 60 percent of its saturation point. Take at least 20.
3. Bias frames. I've never used them. They can be used to calibrate darks of different exposure lengths than your light frames. But if your darks are the same length as your lights, you don't need bias frames
4. You need to take darks for your flats. Take at least 20.

That'll do for now. When it comes to calibrating your images, the process for each type of calibration is slightly different (darks are subtracted, flats are divided after being dark subtracted).

The book you have might go into more detail...

Anyhow, that's all of the top of me head but it should help :dry:

Thanks Dave.
Well, I guess shooting M42 through a 5'' f/15 Mac-Cass with a
Focal Length of 1900mm would essentially be considered narrow field.
(or on my set up - total nuttyness! : blink: )

The set up I have there is fantastic for wide field and thats grand.
But I have this itch to put the ETX-125 onto the Astrotrac
just for the craic to see what can be achieved.
Now, I know this is not your general set up and has way too many
reasons why it's going to yield less than fantastic results
but still, I have the gear so why not give it a go?
It's just that if I do I want to know that it's not
something I'm doing to cause ill effects.
If I can rule out my ignorance then I can say for sure
X/Y/Z does or doesn't work.

So,
with a slow scope like the ETX125 a focal reducer might come in handy?

The whole combo sounds great. I can;t see that it would cause ill-effects - at least not damage any of your hardware... OK, it might give images that youmightn't like, but to an extent that depends a lot on the targets you choose.

You can calculate the field of view of the ETX coupled with the 350D - try Ron Wodaski's free FOV calculator (just Google it). This will show you (with actual images) the area that setup will cover. If you think its too small, a focal reducer will increase the FOV.

HTH

Dave

:laugh:
IMHO TBH FYI The first thing I had to Google was HTH.

I wonder how much more short/txt hand we can get by on!

Well Dave, I dunno.
I'm just gonna give it a lash and see.
Thanks for the advice.

I dunno if the rest of ye deep sky lads came across it but\
I kept seein all the terms but no or little explanation of what they ment.
Say for example Flats.
Do you just take a stock flat or do you need to take it at the same
temp / exposure length etc...
Many of the sites say take this do that but few say WHY you should.
After further and further delving into the realm of this
committed (- maybe a word very adept for those concerned)endeavour,
I'd be happy with some non smudged / trailed shots of M42 / Andromeda or
whatever...
The nights are to precious (in this country) to be fiddling around with
filter wheels and all that..
Not that I'm saying you guys are nuts..
I'm just saying ye are SERIOUSLY nuts.