I took 40 shots of this,
40 @ 4s and 10 darks @ 4s and ten bias frames @1/4000th.
Canon 600D with a 50mm F1.8 lens.
When I add the lot to DSS and run the check for stars, DSS reports only finding 1 star. Registerd them anyway and then it comes up with only 1 frame will be stacked.
I had simply pointed the camera at what appeared to be a "busy" part of the sky. Any ideas of what I should be doing? I am obviously doing something way wrong.
Hi Chris, firstly 4 secs is a very short exposure, so you are not going to get large numbers of stars unless you used a high ISO setting. What ISO
did you use? When starting out in astrophotography don't bother with darks, you can use them when you become a little more proficient; just
enable the high ISO and long exposure functions in your camera, and
the camera will automatically take a dark after each exposure.
To get more stars registering in DSS, and therefore get all your frames stacked, just move the percentage slider further to the left a
bit, and do the star check. Do this again if necessary until you get between 10 and 50 stars. If you go far beyond 50 the registering and stacking will take a long time, unless you have a very fast comp.
You have other things to deal with before attempting stacking images.
Produce quality single frames first. Your focus is way off, how are you doing it? Your stars are not round. These two things need fixing before
you attempt anything further.
If you are interested, at the bottom centre of your image it looks as though you have captured The Toby Jug Nebula; the bright star with a tiny golden coloured cross running through it.
raymo
Last edited by raymo; 27-04-2015 at 01:06 AM.
Reason: more text and more again
In addition to Raymos points i'll add the following; I have trouble stacking photos taken with just a lens, you can turn the star detection threshold down to 5% and it will help with stacking.
from your picture it looks a bit out of focus so the program may be struggling with that also.
use live view then zoom in on a bright star that will help. I find that 8 seconds is about the sweet spot for that lens. here is what you can expect (same lens and camera)https://www.flickr.com/photos/803366...n/photostream/
i'll note that no processing or stacking was done with those - how it is straight out of the camera.
Hi Chris
I don't think you should be getting star trails at 4 secs with a 50mm.
A couple of years ago, i did this image, using just a 50mm F1.8, albeit with a Nikon D7000.
I think i used 10 sec subs at about ISO 3200 or even 4000.
I think i even stopped it down to F4 to avoid the coma, which you can see in yours.
Then i used DSS to stack, and it said there were thousands of stars, although this is a busier part of the sky i guess.
Keep trying though. You can get some great results with just a tripod.
Cheers
I'll try longer exposures maybe 8s as suggested by Russel next time.
The ISO was 800 which I've read somewhere as being optimal for the 600D
Thanks for the other advice, I set the lens at infinity and didn't think of using the live view, will try that
Captured The Toby Jug Nebula; eh? That could only be by good old beginners luck.
Russel,
Tried the 5% with zero stars detected, I need to get the focus better as you said
Bob,
You suggest F4 so I will try that too
All trial and error while I get my feet on the learning curve
I'll try longer exposures maybe 8s as suggested by Russel next time.
The ISO was 800 which I've read somewhere as being optimal for the 600D
Thanks for the other advice, I set the lens at infinity and didn't think of using the live view, will try that
Captured The Toby Jug Nebula; eh? That could only be by good old beginners luck.
Russel,
Tried the 5% with zero stars detected, I need to get the focus better as you said
Bob,
You suggest F4 so I will try that too
All trial and error while I get my feet on the learning curve
Thanks Guys
let us know how you get on - i would pump up the iso to 3200. 800 is too low for a camera that isn't tracking.
Hi again Chris; the infinity setting is useless for astro shots, almost all lenses go beyond the infinity symbol. In Live View choose a bright star, magnify it10x and a white dot will appear in a box at the bottom right corner of the screen.
Adust the focus until the bright star becomes as small as the
aforementioned white dot. If using a zoom lens, make sure that the focusing is carried out at the same focal length that you use to take the shots, as moving the zoom will change the focus.
raymo
Last edited by raymo; 28-04-2015 at 07:09 PM.
Reason: correction
focus is your problem, and maybe dss (i get the same problem trying to stack my own, takes some practice to get it working in dss, i stick with pixinsight mostly. Take notes and work out the software process.
There are NO optimal settings, 4 sec is usable, maybe not to get photos like someone with years of experience and $20k+ worth of gear but you can get nebulosity and certainly more than your eyes can see looking up.
Work on getting good focus, try autofocus off the moon to get you started, stars will still be distorted away from the middle of the frame (using a slower aperture can improve this). Get a good set of shots (dozen lights and dozen darks, raw not jpg) that are in focus even if its boring part of the sky (no matter where you point the camera there are always going to be stars to align and stack with. now play with DSS, take notes, work out what settings will work to use your test set. Its a tedious boring process trying to get going in AP, nothing to do with buying better gear or just pushing a button. Experiment and learn and take notes.
once you get the process of taking photos and processing them then its just a matter of where in the sky to point its all good. its interesting to plate solve a random shot and find you've captured a cluster, galaxy, nebula in the shot and then learn to reprocess to try to bring them out better.
Sil
focus is your problem, and maybe dss (i get the same problem trying to stack my own, takes some practice to get it working in dss,
once you get the process of taking photos and processing them then its just a matter of where in the sky to point :) its all good. its interesting to plate solve a random shot and find you've captured a cluster, galaxy, nebula in the shot and then learn to reprocess to try to bring them out better
I agree that focus is an issue,even trying live view as I did with the two attached images it's still pretty poor.
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Raymo
Hi again Chris; the infinity setting is useless for astro shots, almost all lenses go beyond the infinity symbol. In Live View choose a bright star, magnify it10x and a white dot will appear in a box at the bottom right corner of the screen.
Adust the focus until the bright star becomes as small as the
aforementioned white dot.
raymo
I haven't noticed a white dot on the screen, I'll have to check for that. The live view didn't seem to help much but I will keep trying.
Both lenses I have used in the pics below are manual focus.
Both exposed at 8s, 800 ISO, not the same area of sky.
The first one is the 50mm @ f1.8
The second is a 6.5mm @ f3.5
These are both single raw shots converted to jpeg after playing around with them in Raw Therapee
When using live view to focus on a star I find that it is best to use a high iso to focus (this will make any stars on the screen much brighter) then lower the iso to start taking images.
When using live view to focus on a star I find that it is best to use a high iso to focus (this will make any stars on the screen much brighter) then lower the iso to start taking images.
Rick
+1
Get the focus done first. Point your camera at the moon and autofocus, or the brightess object in the sky (star/planet, doesnt matter) and set your focus before setting up to take photos. Once you have good focus its set for everything in the sky basically. Take it slow, there is usually some lag in camera live view and you might see a star vanish on screen or others appear, the better the focus the more live view pinpoints of stars you will see. Do this on a tripod, let the vibrations settle take a test shot at a faster shutter speed (try faster than 1/ (500/focal length) ) just as a test to zoom in on shot and look at the stars in the middle of the shot. They should look like little "soft" round blobs, they won't be sharp points (btw turn off in camera sharpening). They should not be discs that are bright at the edge and duller/uneven in the middle.
Your last two shots: the first is way out of focus, the second much better but not sure DSS will work with trees/roofs in shot but otherwise the stars in that shot should be in focus enough.
I played with DSS myself last night, threw it a bunch of shots i took a few nights ago, lights, darks, flats, bias all as jpgs (current dss doesnt support the raw from the camera i used). no problems with star detection etc at all. Not a recommended way of processing, I just tried it for fun to see if anything else came to mind to help you out.
Are you using the latest version of DSS from the yahoo group or the one on the website? (link to yahoo group is on the website too). I think the way its star detection works is to look for a round feature that quickly increases in brightness from the background to a peak then quickly falls off the other side. Out of focus stars do not look like this to the software.
As an exercise, you could try batch processing your shots to resize to a quarter size or possibly throw on a small guassian blur to turn the out of focus stars into better dots. These you should be able get DSS to work with. Certainly warmer than taking more test shots. When I get slight focus problems or reprocess shots to bring out a deep space object near a corner where lens distortion is common I manually register in pixinsight and can use star masks and other techniques tomake the stars a bit rounder. While others may throw away the data and reshoot later I am still happy with signal I can pull out of the poor data, it all helps refine my skills.
Get the focus done first. Point your camera at the moon and autofocus, or the brightess object in the sky (star/planet, doesnt matter) and set your focus before setting up to take photos. Once you have good focus
Will try that with an AF lens instead of the manual ones I have been using,
Cheers
When using live view to focus on a star I find that it is best to use a high iso to focus (this will make any stars on the screen much brighter) then lower the iso to start taking images.
Thanks for the tip, I need all the help I can get. Will need to wait for good conditions again, which includes shift work
its all good. its interesting to plate solve a random shot and find you've captured a cluster, galaxy, nebula in the shot and then learn to reprocess to try to bring them out better.
