Basic Astrophotography  
     
   /  
    / Home / Photo Gallery / Astronomy / Astrophotography / Equipment /  
     
   
  The basic principles of film photography are very important and will help the user in developing good skill with digital and CCD cameras.  
   
  Although film is slowly fading, great buys are available for the budget minded first time imager. Wide fields of the night sky are readily captured with relatively inexpensive film cameras with quality lenses.  
   
  Fixed lenses have the best optics. This is true with today's digital cameras as well, don't skimp on quality lenses and buy the professional grade filters. Digital cameras need the best multi-coated filters to keep reflections a bay.  
   
  It is harder to make good quality fast mirrors it is the same with camera lenses.  
   
  Telescopes and camera lenses all work the same, following the same basic principles.  
   
  Note the f/ ratio in lenses progress upward , the next f/ stop will double the exposure time of the previous f-stop. An f/8 telescope is twice as fast as an f/11 scope for imaging. You also must remember this also affects the field of view (FOV). Two telescopes using the same size object will have different focal lengths if on is f/8 and the other f/11. The same exposure of 10 minutes at f/8 will take 20 minutes at f/11. This presumes everything is the same and the film is linear, which it is not. (reciprocity failure)(B=Bulb Setting and would be 2 second exposure)  
   
     
     
     
   
  Some of these great films for astrophotography are no longer being made. Elite Chrome or Ektachrome 200 is still being made and is great for wide fields and captures red very well. Hypered-film is film that is cooked in a vacuum (special gas) to take moisture out and increase sensitivity to light. Tech-Pan hypered very well, while color film was difficult. Check out Lumicon who sold hypered-films.  
   
   
  Simple tripod wide field shots of Orion rising over the Three Sisters in Oregon's Cascade Mountain Range. Note the longer shot has longer and more noticeable star trails. Try to stay under 45 seconds with a 50mm lens to avoid star trails. Sky glow is also a problem with longer exposures.  
   
  This chart works with digital as well as film camera lenses in preventing star trails. Remember that some digital cameras, like the Canon 20d do not have full size 35mm (36x24) chips and a standard 50mm lens is really (1,6 factor) an 80mm lens while a 100mm is 160mm. You must compensate for the length of exposure based on the true focal length of the lens.  
   
  Ektachrome E200 (professional) and consumer Elite Chrome ED200 are still available with very low reciprocity rates. See Michael A. Convington's " Astrophotography for the Amateur" and excellent book on astrophotography.  
   
     
   
  This table is for a dark sky site, light pollution can add greatly to sky fog problems. The altitude above the horizon you image at also affects sky fog along with refraction.  
   
  Try to shoot over head or at least 40° above the horizon.  
   
  For all type of serious imaging a very good mount is imperative. The buy the best optics, to get the best results. I can't repeat this enough, save yourself hours, days of frustration and buy quality equipment.  
   
  With all the GoTo mounts out, the non-GoTo mounts have come way down in price. It is best to concentrate on only a few objects a night, when imaging, GoTo is not must, but is nice to have.  
   
  While fork mounted consumer telescopes can be used to image, a solid equatorial mount is preferred in imaging. The AstroPhyics 900 mount of the left is portable and can handle 70 pounds photographically (very good tracking). When looking at mounts remember the carrying capacity of the mount might be 50 pounds but the actual capacity for good imaging can be 50% less.  
   
  The Losmandy G11 with a Celestron 11" SCT and Takahashi FS78 is a capable imaging setup I used for years. This is reaching maximum load photographically for this mount in my opinion. I recommend the G11 mount as an entry level mount that can take you a long ways into astrophotography with film, digital, CCD and web-cams. I used the mount often with just the FS78 or just with the 11" to cut down on weight.
I also did lots of piggyback work with either scope as a guide scope, both manually and auto-guided.
 
   
     
   
  This Meade Cross-Hair eyepiece is nice in that you can move the cross-hairs and center circle around to center the guide star. I tried to use enough magnification so that as long as the star stayed in the inner circle I was OK (not star trails). During hours of manual guiding you will hit the wrong button once in a while. Don't make your guiding tolerances to tight.  
   
  This is my Piggyback setup on the Celestron 11" SCT (Schmidt Cassegrain). I like the heavy Losmandy plates and camera mounts. a flimsy or none solid camera mount will ruin long exposures.  
   
  Lumicon's Giant off axis guider is great. It also has an optional focal reducer inside for wider fields and shorter exposures. The pick-off mirror allows you to guide through the same telescope you image with. This is import with an SCT since it's mirror may move during imaging. A cable release that locks is also helpful to cut down vibrations. Lock the mirror down before you open the shutter, this is also very important with DSLR (digital single lens reflex) cameras being used today.  
   
     
   
  Here you can vary the distance of the camera to increase image size. You can insert an eyepiece for eyepiece projection. These methods will change the f values and are used for lunar and planetary work.  
   
  Longer focal lengths have a wider area where good focus can be reached. Fast focal ratios have a very small focus zone and are harder to focus.  
   
  With both film and digital cameras I used and angle finder that magnified the image in order to reach focus.  
   
  I held a fussing filter in front of the lens for 4 minutes to make the bright stars flare.  
   
  All of these phots were scanned at 1200 dpi and had very little post processing. Today's slide scanners like Nikon's Super Coolscan 5000 scan at 16 bit and 400 dpi with a raw tiff (image file) of 130 mb. Photoshop CS2 & 3 can really work wonders on this type of high resolution scan.  
   
  You don't need a lot of magnification to capture night sky object. That is M31 Andromeda Gaxaly lower middle right.  
   
  Processed this shot can be blown up to 16x20 high gloss print.  
   
     
   
  Longer exposures and longer focal lengths at a Dark Sky site can be rewarding. OSP stands for the Oregon Star Party. Remember that 600mm focal length equates to 12x in magnification. You don't need a lot of magnification to capture lots of deep sky objects.  
   
  Stopping down a lens helps to alleviate optical problems but may require a longer exposure. The Tea Pot (Sagittarius) in the left photo and Scorpius in the right.  
   
  The heart of Scorpius, there is some vignetting and gradient problems in this image that can be corrected in Photoshop. See my image gallery for a processed version of this photo.  
   
  A long shot of some galaxies. I can detect over a dozen galaxies in a blow-up version of this photo. Digital SLR's can really do well in several 5 minute shots stacked.  
   
     
   
     
   
  Always be on the look out for satellites and in this case a plane flying into you exposure. Cover the lens or scope till the intruder leaves you field of view.  
   
  Keep a log and make notes for every exposure.  
   
  The image circle for each scope varies. this is the area off optimum exposure with no coma or other optical anomalies. I find that good quality scopes will offer a 20mm diameter image circle clear of any problems. You can still image with a larger area 40mm image circle and you won't see the issues on most 8 x 12 or even 12 x 18 prints.  
   
     
   
  The "H" at the end of 400 means I hypered this film to try and increase it's sensitivity to light. It was more sensitive but also changed the film to a more blue tone.  
   
     
   
     
   
     
   
  You can use these exposures to guide you with the new DSLR cameras.  
   
  As you can see we needed lots of magnification for a planet to appear of any size on 35mm format film. Today's smaller format digital cameras and web-cameras show a much larger image in relationship to the chip size.  
   
     
   
     
   
  It took a lot of shots and lost of practice to get such a sharp lunar image on film. Today you can take a consumer digital camera and take a photo through the eyepiece and get the same or better results your first night out. No flopping mirrors or shutter curtains, to add vibrations. Try it you can even hold a video camera up to the eyepiece and record the moon or Jupiter and then watch it on television.  
   
     
   
     
   
  I was proud to get Uranus on film showing its disc. Today you can dot it the first night out with afocal photography and a simple digital camera with fixed lens.  
   
  Trying to balance the exposure and get Ganymede crossing Jupiter with some of it's other moons showing up.  
   
     
   
  I highly recommend Gimp (Free Ware) to start and now Photoshop CS2 and CS3 for doing great work with 16 bit images.
Always save a master in tiff format, it does not degrade the image. JPG / JPEG compresses and losses information in your image, only use it for the internet or printing low resolution prints when the larger tiff files present a problem. I take images to Costco and get nice prints made for a very reasonable price, way less expensive then printing my own.
 
   
  Remember to take notes on each exposure. You would be amazed to come home and view imaged of stars and see do many you have a hard time figuring out what part of the sky it is. You can also review what is working and what is not.  
   
  I will be doing a separate article and show on just digital imaging in the near future.  
   
  The amazing TU-cam and Baadar UV/IR filter can take some amazing images, You have to buy it used, as it is currently out of production, but for $150.00 for the camera, filter and adapter you are on your way.  
   
  The New canon 40d (Winter 2007) is much better than the 20d. I still use the 20d and it's prices are now very attractive for starting out.  
   
     
   
  Registax is Free Ware and newer versions are now available that can really help web-cam and digital imagers.  
   
     
   
  This is an excellent way to mount your fixed lens digital camera or DSLR for afocal work. You will get great results the first night out. TelVue® makes great adapters, eyepieces, barlows and other equipment.  
   
     
   
  This image was taken with a 300 mm f/2.8 lens with a Canon 2xb doubler and special "Hamma" adapter to mount a canon FD lens to the EOS mount of a 20d. This resulted in a 1200mm focal length at f/7.06. The lens was mounted on a camera tripod.  
   
   Canon 200mm f/2.8 L lens piggyback Winter 2006  
   
     
   
     
     / Home / Photo Gallery / Astronomy / Astrophotography / Equipment /