Quote:
Originally Posted by Jethro777
Right.
So, here's some adjustments I'll try. Let me know if there are more, if I have them right or if I have missed something else.
Forum suggested
- Switch off noise reduction. Since I am shooting in raw, it's pointless anyway.
- Aperture should be 2-2.8 from what that lens date looks like - not 1.4 or 8, lol.
- Increase number of frames taken from 9 to 16 or 32 for stacking.
- Make a 'dark' shot (I guess same length as the normal frames I am taking but with the lens on? Is that how I make one?)
My ideas
- Start building a barn door tracker, lol.
- Maybe drop down from 10 seconds to 8, as I can still see star trailing.
- Mozzie repellant. I paid for each final frame with three bites last night.
Questions
1. If the pictures I take look quite 'bright' (light), will DSS 'darken' them so I get a black sky? - Sorry for the stupid question.) If it is quite 'bright' - what should I be adjusting then? For example, I am going to do f/2.0 on a f/1.4 lens at 1600 ISO at 10 seconds. That's going to result in a bright image - right? In my head, I'm thinking "That isn't right!" - but it is, as DSS adjusts it?
2. Also, does the fact that I have a 'bright' object, like Mars mean that the camera is less able to pick up the stars around it? Would I have gotten better results if I hadn't chosen mars? 
3. What ISO is best for my particular situation? From what I was reading, some are doing anything up to 12,000+ and claiming it doesn't matter, while others go for 400-800, or 1200. I'm thinking I should go 1600.
4. Is the best focus actually just short of infinity, or infinity?
Next up will be the Southern Cross with modifications applied.
Edit
Ok, several (e.g.16/32) 'dark shots'. Good for one night. |
Hi Jethro,
As I was in your spot not long ago and from the responses here, I'm not sure if it was clear why you would want to do some of the things noted above and the trade offs etc.
Focus to Infinity. Use your camera's live view on a bright star and zoom in as far as possible to focus. This should result in the best focus. If the moon is up or a street light is visible at a distance (more than 50 mtrs type thing) you can use the Auto focus to focus on it.
Just remember to switch back to manual focus when you go to take your images. (Nothing worse than setting focus, switching to you target to have the camera sit there and try to refocus because you left it on AF).
With star trailing, I thought someone mentioned the "Rule of 500" previously. But given you use an APS-C size sensor you will need to multiply the lens FL by the crop factor (it's 1.6 with Canon sensors).
So your 35mm lens is now "effectively" a 56mm lens. Divide 500 by this 56mm and you get how many seconds you can expose for before getting trailing. (about 8-9 secs). Its not a hard and fast rule but will get you in the ball park for exposure times.
Next point is stopping down the aperture. This is generally done to get better star shapes at the edge of the frame. When the lens is "wide open" (Low F Number) you will get star trailing towards the corners of the frame. Stopping the aperture down can reduce or eliminate this. It comes with the trade off however, that you will not collect as much light and you will need to up your iso or expose longer to compensate.
ISO settings is a bit of a trial and error thing. You should be able to do some google searches around what ISO works best for your camera. I found a page just the other day that mentioned 800 iso on my Canon 1200D was best. I'll try and find the link again.
Generally 800 - 1600 ISO is the sweet spot I think. When I was doing static exposures I would go up to 6400 iso. It brings in alot of additional noise, but with stacking and dark frames you can negate this to some degree. Its a learning curve, so try different iso's and then process them and see what works for your camera and location.
I found that link to ISO for different Camera's -
http://dslr-astrophotography.com/iso...-sony-cameras/
As for your questions about your images looking very "Bright" or white. You want to expose the image for long enough that the histogram is right around 50%. (Google how to bring up the histogram on your camera if you don't know how. It's quite helpful).
If its too low, up the exposure time or ISO or open the aperture up. If its "over -exposed" (Your image looks very white or histogram above 70%) drop the exposure time, ISO or close the aperture a bit. Experiment here till your around the 40-60% mark on your histogram. (Your images could just look very bright due to light pollution or sky glow. In this case your best to head out to a dark site, unless your pretty handy with photoshop, this will make post processing much more difficult).
And the more frames you can stack the better. It will result in a cleaner final image. So try for at least 15-20 frames for both light and dark. (Others may be able to correct me here but 20-30 dark frames will generally be enough even if you do more then that of the light frames).
And always shoot in RAW and turn off Noise reduction in your camera.
Alot of these point's were probably already covered, but from the way your asked your questions I got the feeling you may not of understood some of it. (I felt the same way when doing my research starting out). Hopefully this clarified things a bit and gave you a few more pointers.
