(unknown)

Hi KCC,

This list is primarily for digital still cameras
and not webcamming. We just recently ended a thread
about how we deal with webcam topics and issues.

The QCUIAG

 GoodMorning all...Well last night was a bad night here...Mars was
dancing up a storm.. I thought i was looking at a ghost all night
with very short pauses.. not short enought for me.. tried to get
some picks I uploaded 1 in the mars folder...here is a link...
http://tinyurl.com/mgcx

---

I recently purchased a Meade LX200 12 inch SCT, and want to do
astrophotography with it. I'll be using a Nikon D100 digital camera at
prime focus (or a Nikon 990 with Digi-T ring adapters on a 30 mm
eyepiece).

I know that without a wedge mount, I can't do super long exposures, and
at this time, I can't afford a wedge. My question is, without a field
derotator or a wedge, what is a reasonable limiting exposure length,
assuming dark sky and good Alt-Azimuth alignment for north and south?
Does anyone have suggestions for limits, or do I just go for it and see
what happens?

Denis Anson

--
Denis Anson, MS, OTR
Assistant Professor
College Misericordia
301 Lake St.
Dallas, PA 18612
Phone: 570-674-6413

---

Hi Denis,

A dark frame measures the amount of noise generated by the camera
electronics and CMOS or CCD chip for a given period of time with no
light falling on the chip. Thus the name dark frame. Dark frames are
taken with the same ISO and exposure length as a light frame where
light from the object falls on the chip. The idea is to use the dark
frame to remove the noise added by the camera from the light frame.
This has been done in the past by subtracting the dark frame from
the light frame. But this approach is problematic and so more
sophisticated methods such as adaptive dark frames have been
devised. With todays digital SLRs and the proper use of raw image
data, dark frames, and stacking noise can be very effectively
handled.

Mike

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
 
Ironic, given the name (Coolpix) don't you think?

Can some one fill in a newbie on the concepts of dark frames and
"stretching" of the image? I understand that a dark frame is taken
with the lens covered, to see how much noise is in the imaging chip,
but how long do you go? How does one do this?

If I knew, I could contribute experience with a Nikon D100.

Denis Anson

Marc Paradis wrote:

>Hello Mike,
>
>Thanks for sharing your results. It looks VERY promissing!
>Canon 300d will be available in stores today here.
>
>As you know, A CoolPix 4500 require a cold down period between each
>shot because the heath build up quickly.
>
>Does Canon 10d or 300d have the same behevior? I never heard about
>cool down period except for Nikon CoolPix.
>
>Marc
>
>
>-- In no.spam@mail.pls, "Mike Unsold" <mike_.at._m...>
wrote:
>> I just captured 5 minute ISO 400, 800, and 1600 images using the
>> 300D and stored them in raw format. The three raw images were
each
>> converted to jpeg, 8-bit tiff, and 16-bit linear tiff images.
>>
>> In all three cases the jpeg and 8-bit tiff images showed the
usual
>> hot pixels and some amp glow on the right edge of the image.
>>
>> But the 400, 800, and 1600 ISO 12-bit raw to 16-bit linear tiffs
>all
>> look GREAT. Sorry but I can't get the images to a serve until
>> tonight.
>>
>> I think the 300D is going to be a real winner even if you need to
>> use a remote switch for each bulb exposure.
>>
>> Mike
>
>
>
>Before posting an image to our group please read the space
mangement
guidelines:
>%
20Space%20Ma\
nagement%20Guidelines
>
>Please check the digital_astro FAQ at:
>http://www.szykman.com/Astro/AstroDigiCamFAQ.html
>
>Be sure to visit the digital_astro Gallery and Archive at:
>http://velatron.com/dca/gallery
>http://velatron.com/dca/archive
>
>
>
>
>