need help stacking images

[little col]

got some images of a double cluster in perseus ngc869 / ngc884 last night but i am having problems stacking them in dss , i can load and stack but its bringing an error up on the dark frames , saying that i am using dark frames with jpeg files , because of the lossy compression the calibration is not working with the jpeg files:shrug:
thanks colin

[[1ponders]]

What format were the originals (lights and darks) taken in? Raw or Jpeg?

[little col]

they were all in large jpeg paul , tried another stack but all the colour is discarded , one frame seems to look better than the stack of 32 :shrug:

[[1ponders]]

I've not tried to stack Jpegs with DSS. I'd suggest doing them in RAW next time. There is a program called Imagestacker that you could download and try. It works natively with Jpegs
http://www.tawbaware.com/imgstack.htm

Alternatively you could try Registax 4, but it will be a slow process unless you have plenty of RAM

[little col]

only stacks in 640 -480 dimensions on the download version , thanks anyway , do you think i should try registax ?

[[1ponders]]

Give it a go, it can't hurt. I'll give DSS a go shortly on some Jpegs (after I convert from RAW) and see how I go.

[little col]

ok i will post the rsult whatever happens:thumbsup:

[[1ponders]]

OK here are 14 frames of Corona Australis @ ISO400 @ 240 sec each and converted from RAW to Jpeg using the Canon proprietary software. Dark framed subtracted with Jpegs. No flat field so you can really see the vignetting.

Number 1 image is straight from DSS and into Photoshop. When it came out of DSS it was totally white, I couldn't see any stars. When I opened it into PS it looked similar to other preprocessed TIFFs I have opened in PS. The size reduced and quickly leveled and curved processed image (number 2) looks "sort of" ok (except I haven't colour balanced it) at first glance, but it really is bad. The third image is a crop about 2/3 the way out to the top left corner and the fourth is from near the center. You can see the problem in the center one. The dark subtraction didn't work properly and dead pixels were smeared during the alignment and stacking process. It is generally a pretty grubby image. There are also a lot of artifacts that screwed up the registration processes and therefore the stacking process.

You can see the same image here using RAWs (http://www.iceinspace.com.au/forum/attachment.php?attachmentid=29140&d=1183994204) rather than Jpegs. And here is a crop of the same corner (http://www.iceinspace.com.au/forum/attachment.php?attachmentid=29132&d=1183984819)but a bit further towards the corner

[little col]

:eyepop: looks like dss really cant handle jpegs , looks similar to the way my image come out of dss , but i think i am going to have to image in raw.
here are mine
1: 1 x frame iso 800 30secs
2: out of dss 32 x of the above
3:best i can do in ps :shrug:

maybee this will be a good lesson , oh and they were taken with an st80 refractor , neodymium filter + fringe killer filter

[Tamtarn]

Col all of our images are JPG and are stacked in DSS. Just ignore the message will not calibrate and continue.

The image produced will have very little colour and is sometimes very dark or light so you will have to play with the Luminance and Colour Saturation but don't overdo the colour you just need a hint of colour leave the major post processing to PS or equivalent

[[1ponders]]

I didn't get any messages when I processed the jpegs. Do you have the latest version of DSS?

[rat156]

Hi Col,

The error message is right, if you try a dark frame subtraction using Jpgs, you'll end with artifacts.

I tend to use the in camera dark frame subtraction, it doubles the time between exposures, but rarely do I see artifacts. The problem is that your camera heats up while you're using it and the dark frame doesn't match the light frame. That's why the SBigs etc control the temp of the CCD.

Cheers
Stuart

[little col]

yes it is the new version , i think i will post the single frame :)