[ATMoB-discuss] First photo from C14/ST7

Wed Aug 9 13:54:42 CEST 2006

If the camera has already been taken off the scope, then it's too late
to take a flat. You can use the sky to take flat fields prior to your
imaging run.  This needs to be done just as dusk begins. However, it's a
bit tricky as it needs to be done before the camera can detect stars.
Take a number of them and average them together. 

-----Original Message-----
From: atmob-discuss-bounces at atmob.org
[mailto:atmob-discuss-bounces at atmob.org] On Behalf Of Bruce Berger
Sent: Tuesday, August 08, 2006 6:05 PM
To: 'Buonomo, John'; atmob-discuss at atmob.org
Subject: RE: [ATMoB-discuss] First photo from C14/ST7

Hi John,

Thanks for your suggestions.

These were guided 3-5 minute exposures using the built-in guide chip on
the
ST7. I have 4 darks and 4 bias, and about 9 unfiltered images to stack.
I
will try your advice tonite and repost the result. 

How do I take a flat? I've seen an elaborate setup that Gary Walker
uses. Is
there an 'easy' way?

Bruce

-----Original Message-----
From: Buonomo, John [mailto:Jbuonomo at uhs.harvard.edu] 
Sent: Tuesday, August 08, 2006 3:35 PM
To: Bruce Berger; atmob-discuss at atmob.org
Subject: RE: [ATMoB-discuss] First photo from C14/ST7

 Hi Bruce
I jumping in here late..
Mario has hit most of the major topics 

About the blur, I would say if you have limited images to stack... a
slight
blur would work, but more time on a target is always best.
As for Darks, yes they are to remove the hot pixels as well as other
noise A
bias frames are for the electronic chip noise. 
I use a software tool that creates a hot pixel map this is better then
darks
because is can be scaled and created ahead of time...I have learned that
taking many dark frames and stacking them into a master dark will get
rid of
most of the hot pixels, Flats are good to remove the optical artifacts
like
dust motes and vignetting.

This m57 just needs more images stacked but it is a EXCELLENT start for
the
C14 

Not sure if this will help but my average processing steps for a given
evening and optical config As sky is darkening I take as many sky flats
as
possible Stack these for a master sky flat and apply a matching hot
pixel
map to this master flat.
Take my evening's images (as night progresses my camera's amp glow and
hot
pixels increase) At sign of clouds or twilight I cover the scope's
objective
and take as many dark frames as I can before the sun rises, or begins to
rain...:)

Later I stack the darks and create a master dark and I use a master bias
that I created during a rainy day...(many chances there:)

I will  then apply the master flat dark and bias to each raw image and
then
stack the raw for a summed master for processing

Depending on the target it is either Stretching or DDP for brining out
the
detail and other various tricks I picked up from reading the e-book
Photoshop for astrophotography 

As for the image did you use a auto guider at all? And what was each
exposures set at?

Thanks
John

John Buonomo
http://www.astronight.com/

-----Original Message-----
From: atmob-discuss-bounces at atmob.org
[mailto:atmob-discuss-bounces at atmob.org] On Behalf Of Bruce Berger
Sent: Tue., Aug. 08, 2006 2:17 PM
To: atmob-discuss at atmob.org
Subject: RE: [ATMoB-discuss] First photo from C14/ST7

I may be misunderstanding something. I thought the dark exposures were
supposed to null out the hot & dark pixels. How do you subtract them
separately? Should I apply a 2-4 pixel Gaussian blur?

Bruce

-----Original Message-----
From: mmotta at massmed.org [mailto:mmotta at massmed.org]
Sent: Tuesday, August 08, 2006 1:53 PM
To: bruce at scopemaker.com
Subject: RE: [ATMoB-discuss] First photo from C14/ST7

Choose only those that have tracked well.
do basic processing on each (Dark/ flatt field/ bias).
Then, do the hot and dark pixels on each.
Then, stack your best ones, and do all higher level processing (digital
processing, masking, etc ) on the combined deeper stacked image.

Mario

On Tue, 8 Aug 2006 13:44:17 -0400, "Bruce Berger" wrote:

> 
> Thank you. So here's a question - I have about 8
images
> @ 3 or 5 minute
> exposures. Should I align and stack, and THEN apply Dark & Bias 
> frames, or should the Dark & Bias be applied to each frame before 
> stacking?
> 
> I do not have MaxIm, but I do have Registax, CCDSoft 5.0 and Photoshop

> CS2.
> 
> Bruce
> 
> -----Original Message-----
> From: mmotta at massmed.org [mailto:mmotta at massmed.org]
> Sent: Tuesday, August 08, 2006 1:35 PM
> To: valleli at rcn.com
> Cc: bruce at scopemaker.com; atmob-discuss at atmob.org
> Subject: Re: [ATMoB-discuss] First photo from C14/ST7
> 
> Look on the black "sky" and you will see single pixel white dots. 
> Those are hot pixels.
> Mario
> 
> On Tue,  8 Aug 2006 13:19:35 -0400 (EDT), valleli at rcn.com wrote:
> 
> > 
> > Mario,
> > 
> > I see the dark pixels, no problem. Not sure what you
> are referring to
> > for 'hot' pixels.
> > 
> > Is it the mottled (grainy) background?
> > 
> > I downloaded the JPG and then viewed it in
Photoshop.
> > 
> > What I saw on the laptop screen had a lot more
detail
> in the ring than
> > this processed exposure shows.
> > 
> > Would binning for such a small object have been
> helpful?
> > 
> > Paul
> 
> 
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> ATMoB-discuss mailing list
> ATMoB-discuss at atmob.org
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