Quote:
Originally Posted by cristian abarca
T I took the cheap option and bought plate glass. All up it cost about $320 Australian dollars. To get a Pyrex blank from the US ia about $600 US plus delivery.
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Including air freight and taxes a 42mm Pyrex 16" blank ends up at about $1200. But it would be much more forgiving to work with than a 25mm plate glass blank.
If I can make a suggestion, get the scope up and running so you can star test the mirror vertical axis for astigmatism before you begin parabolising. You'll save a lot time that way. From memory I reground and polished the ASNSW 16" at Bowen Mountain 3 times before I was satisfied to figure it, thankfully having the scope to test it in. Being very thin , 25mm, its not crippled by being plate glass and from memory can give a very good image at 400-500 X . The first time I star tested it though , the image was so bad I couldn't get any kind of focus at all, so I learnt a lot about working thin mirrors on that one
