T-Shirt Flat Field Hoop

The idea for using a T-shirt placed over the front of the telescope came from Ron Wodaski (The New CCD Astronomy) who demonstrated how easy and accurate a flat-field can be obtained.  The T-shirt acts as a diffuser and can be used during the daylight or night.  By using my "Flat-Field Hoop" the T-shirt can be easily and rapidly placed on the scope, without the fuss of rubber bands or bungee cords.  It is always ready for use.

Materials can be obtained at your local craft store:  thin foam, glue gun, needlepoint hoops, straight edge, utility knife. Buy the hoop slightly larger than your dew shield or scope:  8" hoop for an AP 155 and 6" for an AP Traveler. Cut the foam into strips and glue foam to the inside of the inner hoop. Glue as many foam layers as needed to make the hoop snug with your scope.  I needed two layers for the 8" hoop and 5 layers for the 6".
Use an old T-shirt, placed between the hoops, and cut to size. Finished "Flat-Field Hoop."  Make sure the cloth is taut to give even illumination. It fits perfectly.  Increasing the layers of cloth can be done to decrease the light levels. Ready to image.  Make sure light is not shining directly on the cloth.  You can aim at a shady area or a white board.

 

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Email:  JGPierce(NOSPAM)@comcast.net