Quote:
Originally Posted by Renato1
I use a red No. 23A filter on smaller telescopes and red No. 25 filter on larger telescopes to make the polar ice cap stand out. If you don't have them, you can try to improvise with any orangey sunglasses you may have, or that red translucent plastic gift wrapping stuff that you can find around the place.
Cheers,
Renato
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Hi Renato, whats the difference between these 2 filters? Is their transmission spectrum different?
I tried using an Astronomik UHC filter to increase contrast, but it just seemed to add a blue halo around Mars.
Thanks
Luke