WIDE FIELD ASTROPHOTOGRAPHY - 4 In this fourth lecture on astrophotography with wide field systems, we will outline step by step the procedure required to obtain top rate results with any piggyback system. All of the methods used in this lecture have been proven by many of our club astrophotographers and should provide many useful tips. After mounting the camera lens combination securely as discussed in the previous lecture we can start preparing to take the actual photo. The procedure is to first align the camera in parallel with the main instrument. You may have to offset it a bit as not to include the telescope tube in the bottom of the frame! Next aim the camera at the subject and carefully compose it the way you like. With a low power ocular inserted in the main scope, scan around a degree or so until a suitable guidestar appears within the field. You might like to recenter the camera on the subject at this point, but with a wide field lens, this is not usually a concern. How bright must a guidestar be to be useful? Bright enough to be clearly visible in the guiding eyepiece at the guiding magnification with the reticle suitably illuminated. After a while, you will get a feel for what brightness this star must be. With the guiding ocular installed, and the crosshairs lined up to match East - West and North - South, check the buttons on your drive correctors hand paddle to make sure the star can be moved in any direction in the guiding field. Center up the guidestar, open the shutter and lock down the cable release. Recheck the guidestar, and start your timer. Here is a tip for longer exposures: Most individuals find that a suitable exposure is on the order of 30 minutes with a 400 speed film. But after 15 minutes or so, they cannot go on because of fatigue. One solution that works well is to go for that first 15 minutes, then put the lens cap back on loosely or cover the lens with a small dark cloth. Take a five or ten minute coffee break, then recenter the guidestar if needed, and remove the loose lens cap or dark cloth. Then continue on with the exposure for another 15 minutes. This way you can be guiding your second half of the exposure fresh and alert. This technique has allowed many amateurs in our club to go those longer exposures on the finer grained films, and improve their results measurably. Printing Options. After a long night at the guidescope, the film is ready to be processed. For the home darkroom enthusiast, this can be on the same evening that the astrophotos were taken. More often than not, the development is in the hands of the professional photo lab. For this reason, slide films are best. The lab can do little harm to the color balance of the original shot, and usually the higher contrast of the slides themselves yield more pleasing results. However, since nearly all photo finishers do not know a dark sky background from a poorly exposed terrestrial shot, they may set the automatic cutting and framing machine to chop your hard earned shots to bits! There are two approaches to saving your evenings work from this terrible fate. First if you specify to the photo finisher only to develop but not mount or cut, then you can do it yourself with easy to use slide mounting kits. An alternative is to take some terrestrial shots at the beginning and end of the roll, and then they will have something to line up on the cutting machine. For prints, the problem is multiplied by the printing process itself. In this step the lab tech usually botches up the colors, and nearly always prints them too dark. If you must use print film, a workable solution is to get real friendly with a local one hour photo lab, and work with them into obtaining suitable results. The goal is to achieve a nearly colorless medium dark grey background to your prints, so that the maximum details show through. For commercially processed B&W prints, specify "print for maximum contrast" on the envelope, and this usually works well. One final approach to getting the prints done at the local one hour photo is to get them to make a series of test prints of a typical astroneg with your planned usual film. Pick the best of the test prints and have them match the print density and background in the remaining prints. Now save that test print and tape it onto the envelope you will use later to bring in more astrophotos in. Then they will always have that one standard print to go by in producing more predictable results.