WTS : 203mm f/4 newtonian OTA + Rings (Sold out!)

orly_andico · Post by **orly_andico** » Thu May 06, 2010 6:54 pm

@stuart,

Yup that Roddier test is the sh*ts :-)

I intend to try it out RSN. I just don't have a good mount yet (getting high power star tests with a non-motorized mount sucks) but I'm waiting for VPOST to give me some good news..

orly_andico · Post by **orly_andico** » Thu May 06, 2010 7:50 pm

@Stuart, about that artificial star... I saw some calculations that to accurately simulate a point source with a 10" f/5 newtonian, the artificial star has to be 50m away!!

orly_andico · Post by **orly_andico** » Thu May 06, 2010 8:04 pm

@Stuart, I think the calculation was from the Dutch guys' book (I could never remember their names hahaha)

I don't think dragoncai2008 is really a sales person or that he means to make a business out of this.. besides the Chinese master mirror maker probably can't scale so if he gets popular you'd be looking at months-long wait times.

and the somewhat brusque "feel" of his posts are probably an artifact of non-native English.. (I think)

I'm using a plate-type cell ala Gary Seronik in my dob right now.. for a 10" or smaller, thick, mirror, the cell doesn't need to be anything fancy.

rlow · Post by **rlow** » Thu May 06, 2010 8:27 pm

scope with 1/10 optics is already an excellent scope. Can't get at such cheap price. There is no free lunch, folks.

If u wanna test it, I got an artificial star, and ronchi eyepiece. And maybe we can compare it with another excellent scope here, say with ZOC mirror.

orly_andico · Post by **orly_andico** » Fri May 07, 2010 1:24 am

@rlow

i'm sure it won't be a ZOC. or maybe the guy can make a ZOC class mirror once in a while, but if he could do so consistently, they wouldn't be S$330!

actually the mass produced optics like GSO can already hit 0.95 strehl on the WinRoddier if you get lucky... so a ZOC class mirror from China is quite possible.

dragoncai2008 · Post by **dragoncai2008** » Fri May 07, 2010 10:39 am

@rlow, I am not a salesman at all! I am not trying to sell you any such kind of mirror. I had pointed it out in my previous post, this is just and mostly to give everyone here some useful information! and I will be the first one who's going to buy such a miracle mirror.

what i really want to sell is my used 203/800 f4 newtonian I bought half year from a chinese telescope manufacturer.

I have not yet obtained my 254mm mirror, I dont have any test equipment to check the accuracy of that big mirror. I guess most of amateurs don't have either. a suit of knife-edge apparatus used to check the accuracy of big mirror is very expensive even in china.

I think no point to argue much about how possible 330$ for such a good mirror. I tend to believe, because

1) the mirror maker who's chinese name 苏鲁锭,is a very famous mirror-making master in china.

2)I have read lots of praising posts and photos taken by telescopes with his mirrors.

3)I have made appointment with the master in June when i go to china on a biz trip and he will show me how he tests mirror accuracy and will do comparing test with market brand mirrors.

4)I put my order in Jan 1,2010, if you wanna one mirror from him now, you got to wait for half year. there're many people in waiting queue. he's not making a living on mirrors, he got his official job. therefore we can expect a cheap price but in high quality. he likes the challenge of making high performance mirror.

5)if you want guarantee, you may go to buy Meada/Celestron or even AP, ED OTAs. for amateur, our goal is always to make out the best tube in a least amount money.