Techniques
- CJUtfltiN REQUIRED
Note the warning at the start of this book, and do not attempt any solar observation until you have assimilated all the details in this and other chapters.
To repeat: smoked glass and exposed film cannot be relied upon to act as safe filters for looking directly at the Sun; neither can you depend on CDs, space blankets, aiuminised helium balloons, potato crisp packets, floppy disks, smoked plastic, crossed Polaroid filters, sunglasses, mirrors, medical X-rays or almost any other of the items that may be suggested from time to time as a substitute for the filters discussed below, to act as a reliable filter.
Remember that you may have more than one telescope. Most main telescopes have a small telescope attached to their side to act as a finder, and in some cases there may be more than one. The objective of the finder must be blanked off (covered completely with an opaque screen), or equipped with a full-aperture filter before any soiar observing procedure is attempted with the main telescope» The sunlight passing through a finder if it is not blanked off may be sufficient to cause burns or to damage parts of the telescope. Note also that most finders have cross-wire eyepieces to enable them to be used for aligning the main telescope onto an object. The focused image of the Sun is likely to melt or burn these cross-wires, so the finder should not be used for eyepiece projection unless a non-cross-wire eyepiece is put in place of the normal finder eyepiece (see the section on projection below for further details).
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