Digital Astronomy

Experiments in Afocal Eyepiece projection Astrophotography

   My start into this hobby was like the cart before the horse. I had purchased a digital camera first. I was taking pictures of everything at the time, but one night at my brother-in-law's home, he had his 4.5" reflector out and was viewing the lunar landscape. I decided to point the camera at the eyepiece. The entrance pupil to the camera was quite small, so it made it difficult to aim the scope and the camera at the same time to have a image show up on the camera's display . Once the image appeared, the other trick was to hit the shutter release without jerking the camera and losing the image. It proved to be a task, but the first results were inspiring. As I look back on these first images, I can honestly say, they are less than desirable, but it helped nurture a new hobby.

   Camera Attachments:

   There are a number of ways to attach the camera to the scope. My first was the EZ-Pix digital camera adapter from Scopetronix. The folks at Scopetronix have a wide variety of attachments for all types of digital cameras and if you are interested in pursuing this hobby, I can't recommend viewing their site enough, it is loaded with help and ideas on digital imaging. Orion has a few themselves that are along the same lines as Scopetronix.

   The initial setup using one of these adapters can be quite a chore. The camera adapters attach directly to the eyepiece by using a 1 1/4" clamp. Attaching the camera adapter to a small plossl is tedious, but can be done, but changing eyepieces during the middle of a image session is difficult. I did manage to attach the adapter to the diagonal of the scope using the 2" clamp that normally is provided with the adapter, but I had to pad the inside of the clamp for a tighter grip. It still proved to be a touchy arrangement .... no pun intended.
  Then comes the alignment of the adapter. Adjusting the camera to the eyepiece to minimize vignetting, it is a process of trial and error. Raising or lowering the camera from the eyepiece while viewing the camera display is the best way to rid yourself of this "hole effect" to your images. 

   Digital Rules:

   Rule #1: 
  Turn off the flash! Don't know how many times that I have done this, but it comes as quite the surprise when that flash of light goes off!

   Rule #2:
 Use either your timer or a remote to trigger the shutter. Any movement to the camera or scope during the time the shutter is open can and will ruin your image. Using the timer function on the camera can be a bit tricky. Depending on zoom settings, you may have to place the object at the outer range of the camera display so that the object will be centered when the shutter releases.

  Rule #3:
 Use rechargeable batteries or a DC power adapter. One can pay a small fortune in batteries with the way digital cameras eat them! Refer to the camera manual for compatible rechargeable batteries or DC adapters. This purchase will pay for itself in no time!

  Rule #4:
 Don't use the digital zoom. The digital zoom degrades the image quality. Use the optical zoom only.

  The setup I currently use is a Olympus C-4000z with a plumbing coupler that I purchased for $5 at a local hardware store. This coupler fits nicely over the entire camera lens and holds a lanthanum eyepiece at the other end. The coupler has one side at an inner diameter of 2" while the other side has an inner diameter of 1 1/4". Hose clamps are used to just snuggly clamp down the arrangement. I normally use a Lanthanum eyepiece. It's outer diameter is the perfect size for the coupler. 
  Some digital cameras will come with a video cable. I use this to cable to output the LCD display to the TV. The TV is used instead of the small LCD viewer on the back of the camera to adjust the focus. This is a great setup for the backyard, but is not recommended at Star parties! Any outside light source at a star party is considered a nuisance.

 Camera Settings:

  Most digital cameras have a variety of settings one can choose from. Digital cameras can have four different shooting modes: Program (automatic), Aperture Priority, Shutter Priority and Manual. The Program mode will use the factory settings which will most likely be designated to the most basic, or Automatic modes. Using the Program mode is not recommended.
 The best setup so far is to use the Manual Mode to adjust the Aperture and Shutter speeds manually. These are some of the settings one can try.

 One can experiment with these settings to try and achieve the best image. If your image shows up as a white blob, it's a good indication that the shutter speed is too slow and it needs to be quicker.
 Example: A full moon image with 1/100 of a second shutter speed turns out to be a white orb, increase the shutter speed to 1/150 of a second to not allow as much light through the shutter. The process is reversed if an image of an object is dim.

 The Elusive Focus: 

 Focusing is the hardest part of digital imaging. Using the auto focus works with lunar images, because the object is bigger and will remain in the LCD display, but by using the timer, there may not be any object to focus on till it comes into view. Some cameras will allow manual focus. By setting the manual focus to infinity, one must use the scope's focuser to properly focus the image. This is where the TV hook up can allow one to see a larger image than what is on the LCD display on the camera to allow for a finer focus. I can't tell you how many images I have sent to the recycling bin that have been out of focus. This is probably the most frustrating part of imaging. The elusive focus.

 Another setting is to set your camera for sequential shooting. This setting will rattle off four images at one time. This is nice when it comes to stacking your images. One can have four images in a row, with barely any time between shots. This is especially nice for planets like Jupiter where the planet surface is in a constant state of motion.

 Doing deepsky images for obvious reasons, one needs a scope that can track the object.  If your camera has a  Noise Reduction feature, it's recommended to use this feature especially for the longer exposures images. As the camera stays on, the camera's CCD chip heats up producing millions of tiny red and green dots in an image and ruining the shot. These dots will increase as the camera stays on. Plus with the LCD display on, all it does is add to the heat within the camera. Again, this is where the TV hook up can allow for more images before the "Dot's of Death" will be produced in every image. The only downside to using noise reduction is that you cannot set your camera for sequential shooting. 

 Processing your images:

 One of the tricks of producing a better image is by stacking your images. This process will take multiple images and practically pile them one on top of the other making a composite image. There are some freeware programs available on the WWW and they are quite nice for the price!
  Registax is a very nice piece of freeware that can process these file extensions; jpg, jpeg, bmp or avi. 
 AstroStack is another nice piece of freeware that can stack images as well. Astrostack works with bmp's and avi file extensions.
 These freeware programs can not work with large image sizes though. From a 3 megapixel camera, a raw image can be somewhere in the neighborhood of 2200x1700 pixels in size. The image must be cropped down to a minimum of 800x600 pixels.
 All digital cameras come with an imaging program to help with the processing of your images. So one can use their imaging software to crop or resize their image prior to introducing it to a stacking program.

 I don't claim to be an expert on this! I have made plenty of mistakes, trying different setups, but hopefully this will help someone to avoid the same mistakes I have made. I am continually trying new ways and settings to achieve digital nirvana and that path is not always straight and narrow, but that's the beauty of digital imagery, if you don't like the image, send it to the recycling bin and try again!

 Bottom line is to have fun and enjoy the Stars! 
And a few pictures of the experience is a bonus!

Backyard
RR

Questions?
Try here Scopetronix "How to" with digital cameras
Or drop me a line.
RokyRhoads@nogarbageaol.com
Remove nogarbage ;-)

I can't say thank you enough
to the folks on the OO Board!
(too many to thank but TD Carls has been an inspiration)
Thank you for sharing the wisdom
and the passion to reach for the Stars.