A flat field box for the Planewave 14" CDK

December 2017. Long nights but each one is as overcasted as the other. So what to do? Building a flat field box could be an interesting change and no difficult one. The following article shows the building of a flat field box for the Planewave 14" with a diameter of about 36 cm. The materials used are:

The base plate has a surface of 46 cm x 50 cm. 7 strips of LED's (each 40 cm long) are fixed parallel to each other at a distance of 6 cm. A first polystyrene plate is fixed in front of the wooden box painted white at a distance of ± 2 cm from the LED's. As the individual light sources are still clearly distinguishable, a second plate is fixed at a distance of ± 6 cm from the first plate. The dimensions indicated here have been chosen in relation to the parts I found in my garage. So choosing larger distances between the plates can result in an even flatter illuminated field. As the resulting flat box is rather bulky a part of a broken broomstick serves as handle for the box.

The flat box is positioned in front of the telescope by using a tripod. This setup makes it rather easy for positioning the box in front of the telescope.

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Figure 1: What had to be bought? An LED strip light (3 m long) and an opal polystyrene plate - an investment of about 32 Euros. The rest of the flat field box had to be adapted to the parts I found in my garage.

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Figure 2: The box is painted white; the LED strips are glued to the base plate and the individual strips are soldered together.

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Figure 3: And there was light - at the first attempt! The individual LED's are spaced 3 cm apart; the strips spaced 6 cm apart. Only one opal plate close to the LED's is not enough to create an even illuminated field.

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Figure 4: Using a second plate gives the required result. Now the flat field box can be tested with the telescope.

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Figure 5: Planewave 14" and the new flat field box. Until now, I used the twilight sky to get my flats. One of the big advantages of the box is, that you can change your setup several times during one night and acquire immediately the required flats for each setup.

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Figure 6: The flat field box is mounted on a tripod and positioned in front of the telescope. Example of a flat frame (dec. 2017; stretched image, so that every smudge can be seen). See the following link for the analysis of the flat field frame using the combination Planewave 14" - Canon 500d.