The bad news for amateurs
•BVRI filters are simple to mass produce (coloured glass) and thus cheap – a reasonable set can be bought for a few hundred dollars.
•Sloan ugriz filters are special, interference filters and made to order.
–They are not catalogue items.
–A typical price is $3000-$10000 per filter.
–Smaller professional observatories cannot afford them.
–They are totally out of reach of 99.99% of amateurs at present.
–They have a limited lifetime and need replacing.