[mental4astro (Alexander)]

Yes. White is the colour that is least problematic when it comes to dew condensing on it, and has less technical consequences to the instrument and mount.

Black is the very worst colour possible. At night it causes the item to drop its temperature below ambient, and as a result it will not only attract more dew, but it will dew up first, and if the ambient temperature is close to zero, the item that is painted black will have the dew turn to frost.

Not only this temperature characteristic of black, it also causes much greater shrinkage of the material. Particularly composite materials.

You will never see a professional instrument painted black for the last reason alone. The complications that uneven shrinkage causes makes it impossible for engineers to calculate the shrinkage of the various materials so they can best control the instrument and accuracy of tracking. How? A big scope is designed with flex in mind, so as the scope slews across the sky, the primary mirror's cell moves the same amount as the secondary cage no matter where in the sky it is pointed to. If the materials that are used in a truss instrument start shrinking at non predictable rates, the alignment of the optics goes out the window. White is the colour you will find the vast majority of professional scopes. This colour provides more predictable shrinkage characteristics, and as mentioned earlier, is least prone to dewing up.

I have paid close attention to the temperature and dew characteristics of items painted black over many years. At the dark sky site I use, dew is an infrequent occurrence, and often when it does form it is light. However, I have noticed that items that are painted black will always attract what little moisture is in the air while every other non-black painted item stays dry. And without fail, when dew does form, those items painted black will be sodden long before anything else is wet, and often have formed frost while all other items are only wet.

It is only amateur instruments that have their instruments painted black or other dark colours, and entirely only because of visual appeal, and without any thought given to possible consequences. And because of the shrinkage and dew issues with black and other dark colours, amateurs go bloody nuts trying to come up with ways to combat heavy dew.

It is becoming increasingly popular to insulate Maksutov and SCT's. This insulation is primarily to prevent a heat plume from developing inside the OTA and the scope can be used at high magnification straight away. Scopes that are painted black show a much more intense heat plume than white coloured ones of the same design and size. As soon as these scopes are insulated, and the key here is the outside of the insulating wrap IS NOT BLACK, and not only does this prevent the heat plume form forming, but dew is also much less of problem for those scopes that were painted black or other dark colour.

Alex.