16 inch project

[cristian abarca]

Hi guys all this talk about 16 inch mirrors got a little bit tempting so I decided to buy a 16 inch blank and make one myself. I have to finish my 10 inch classical cassegrain first but it's almost done. So for my next project I'm going to make a 16 inch F5 truss dobsonian. Here is a picture of the blank.

Regards Cristian

[skies2clear]

Hope it goes well Cristian. Brings back some memories years ago when I did a couple of mirrors, but much smaller than this. Extremely rewarding.

Everyone should have a crack even if nothing else, to learn a lot from it.

Looks like plate glass in the picture? I notice you have a 19" pyrex blank. The 16" will be good practice to hone your skills on first

Clear skies
Nick

[DobDobDob (Ron)]

How much would a blank like that cost?

[norm]

Hey Christian,

Good luck with the project. Keep us posted on the progress. I would like to know how you even start off the grinding process.

[cristian abarca]

Thanks guys. 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. Since I'm going to use this telescope only for star parties I'm not too particular on the cooldown time, etc. The 19 inch blank that I want to eventually use for photography is Pyrex because then I will be fussy about the quality of the glass as cooldown time and temperature variations will affect the image, specially in metropolitan Melbourne.

Regards Cristian

[DavidH]

Nice one Cristian, a 16" is about the size I would like to have a go at next... that is if I ever get finished my 6" mirror.

Regards,
David.

[cristian abarca]

You'll get it done David. This time I intend to keep a diary of this project just to see how long it takes.

Regards Cristian

[Satchmo]

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.

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

[Ambermile]

Originally Posted by Mark Suchting

Including air freight and taxes a 42mm Pyrex 16" blank ends up at about $1200

I have 22" BVC, here: http://www.ajstelescopeworkshop.ca/

Better temperature stability and easier to work...

Arthur

[cristian abarca]

Thanks Mark your advise is always welcome and noted. I was originally going to buy a BVC blank but I sent the guy 5 emails and got no response back so I decided to take the cheap option and save my money for another purchase, like a CCD camera.

regards Cristian