Monday, June 23, 2008

First DSO Image: M13

click on image for full size

Tonight I took my first set of DSO images using the Nikon D40 with my LX200. Sky conditions were excellent, with seeing at 4/5 and transparency at 4/5 as well. I headed up to the local observing spot with a good mate of mine who had one of his many refractors (provided excellent views of a Jovian transit as I packed up).

I targeted M13 initially, as this is a very bright globular cluster and made for a somewhat easy target. Despite some galah incorrectly wiring his telescope nearby causing it to goto objects in the Southern Hemisphere, I was able to focus on the task at hand and managed to take lots of snaps :-)

This image is my best for tonight.

Image details:

10 * 20 second exposures
1600 ISO
Processed in Deep Sky Stacker
Mild curve adjustment and sharpening in Photoshop

A few folks have messaged me asking for the method used. So, here it is. I am far from an excellent astrophotographer as I am just starting out, so take this with a pinch of salt!

  1. Align the scope using 2-star alignment method in Alt-Az configuration.
  2. Set camera settings:
    1. Put camera in full manual mode (“M”) on the mode dial
    2. Press the + Magnifying glass button twice to modify settings, using the arrow cursor key button to navigate to each setting
    3. ISO 1600
    4. Shooting mode to remote control, zero second delay
    5. Quality to HIGH JPEG (this is what I used last night, but I think you’d be better using RAW mode)
    6. Noise Reduction ON (Next time I want to try without noise reduction, I think this actually causing more noise)
    7. Set shutter speed (using click dial on back of camera) to 20” (20 seconds)
  3. Place camera on scope
    1. Camera attached to T-Ring, then 2” T-adapter for use with my 2” diagonal
  4. Command the scope to GOTO a nearby BRIGHT star to use for focusing
  5. View the star in the image finder of the camera, use focuser on scope to get sharp image
  6. Then go to desired object (for example, M13)
  7. Check viewfinder again to see if you can see object
  8. Take a sample shot
  9. Review the sample photo
    1. Try and center it in the field of view. This may be an iterative process
    2. Focus focus focus! This is hard and takes practices, again iterative
  10. When satisfied, take a sequence of shots
    1. I took ten shots for each object
  11. When done, process all images in a stacking software program
    1. Last night I discovered Deep Sky Stacker (DSS). It is freeware and very easy to use.
    2. Normally I use Registax (also free) but for some reason DSS gave me much better results.
  12. Then sharpen and adjust in an art software program like Photoshop
    1. Apply mild sharpening, not too much as it brings out noise
    2. Curve adjustment can be good, brings out subtle colors
    3. I also use freeware noise reduction software like Imagonic Noiseware to try to reduce extra noise in the image.
All in all a good night out. I still have a lot to learn, but an image like this the first night out isn't too shabby at all IMHO. I also took some images of M57 but am working on those and will post them if I think they are any good.

1 comment:

Anonymous said...

galah=Aussie for pendejo.