Sorry for the bum steer, I thought it would be in exif details, I use a ccd not a dslr, which uses the fits file format and has a fits header similar to the exif header, so assumed it would also be in the exif.
No worries John, I expect somebody will eventually tell me where to find
it, assuming that you can with my camera; it's only a budget level one
after all.
raymo
Perhaps Justin or Chris could clarify what they mean by having Liveview
switched off while imaging[Justin said that it would get rid of the lines
on my images]. I only use it for maybe 20 secs or so with my Bahtinov
mask to get the focus right before starting the session. I will now be focusing using BYE. I don't understand why I would want Liveview on
during imaging.I like to store my images in the camera as well as on the laptop as a backup. This doesn't cause noise does it? Sorry, I'm not very
tech savvy.
raymo
Hi Raymo,
Are you imaging via laptop or on camera?
If by camera, live view will usually shut down after a while unless you have adjusted the setting in the camera.
If via lap top, the live view won't shut down unless you turn it off.
I've forgotten quite a few times only to find a very noisy sub at the end of the exposure.
Jo is right about the display, turn that off as well.
Hi again Justin, Up to now I have been old fashioned and stood at the camera and done all the exposures manually. I turn Liveview on, focus
with the Bahtinov mask, turn Liveview off, and as the screen lights up at the end of each exposure I immediately take the next exposure, so the screen lights up for less than a second at a time.The only time I use the laptop is when using my webcams.
raymo
Alistair, I came upon this one I was playing with. Disregard the colours.
The noise pattern I mentioned shows up better with less colourful images, but is still obvious. This was 50x 20secs @ ISO 400. I'll have a look for some longer individual subs.
raymo
Ray. That is either horizontal banding, fixed pattern noise and just a function of your sensor operation or the result of stacking low SNR images without dithering (or both) - particularly DSLR images. Explanation is complex, so suffice to say that dithering will most likely fix this. If you can move your mount in RA or DEC between images with your hand controller without the image going outside FOV and repeat between images - random is OK - I think you will see an improvement.
I get this too Ray with my Canon 300D. You see less of this with a less noisy camera but as Rowland says, dithering will sort it out. I've got to get dithering going myself.
-Cam
Hi Cam, Let's not dither about, and get on with it then. People on this thread seem surprised that the 1100D has this problem as it is thought
to be a low noise camera.
raymo
Hi guys , I have noticed this "aberation" in both my 1100d and 450d. It seems to be more noticable when the sky has more background glow. (ie moon or streetlights) I wonder if it could be a cannon software glitch?
Hi Rick, Yes it does seem to be more noticeable under certain conditions, but I don't think that it actually varies. I think it's always there if you look
hard enough.
raymo
The consumer CMOS sensors installed in todays digital cameras are active devices. Each pixel is composed of a photosite (the light sensitive bit) co-located with a processing circuit. Consequently, CMOS sensors have characteristic patterns of electronic noise.
This is normal, but typically different for each camera model. Banding is a function of CMOS operation. Some worse than others. To obtain good results from CMOS images, they must be calibrated. In many cases dark and flat frames are adequate for this purpose.
There is nothing wrong with the camera, it's just that we are asking it to do something for which it is not specifically designed - unlike CCDs which are passive devices (please correct me if I am wrong about this) and usually cooled.
I would use in-camera reduction if taking only a few images at a time. It is very convenient, though not necessarily suited to large image sets.
This digital low light imaging thing is hard work at times and there are no shortcuts.
You are stacking lines of electronic noise layer upon layer - the effects are devastating to your data.
