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

dragoncai2008 · Post by **dragoncai2008** » Thu May 06, 2010 2:43 pm

I have a china-made 203mm/f4 newtonian reflector telescope to sell. I bought it half years ago. due to that I am going to DIY my 254/f4.5 tube, therefore I want to sell this 203mm OTA at S$200 only. buyer must collect in Singapore.

If you are interested, pls email me with your contact no to dragoncai@yahoo.com.sg. I will contact you and arrange a time with you to check the tube.

orly_andico · Post by **orly_andico** » Thu May 06, 2010 4:16 pm

what sort of mirror is that? a hubbleoptics mirror? or a synta/gso mirror?

1/10 to 1/20 is meaningless without test data..

rlow · Post by **rlow** » Thu May 06, 2010 5:44 pm

1/10-1/20 is p-v? rms? Is there a reliable test report?

dragoncai2008 · Post by **dragoncai2008** » Thu May 06, 2010 5:47 pm

you only hear synta/gso, they are good, 1/10 around, you can go to their sites to buy.

if i just put 1/10, 1/20 accuracy without any test paper and you believe, then you are either too naive or you are just a newbie.

besides, don't you know not only the main mirror accuracy is first important, the 2nd mirror accuracy is also very critical?

the newtonian mirrors that I talk about here are all manually-made by a very senior chinese mirror maker who has been engaged in such hobby job for 29 years and very famous in amateur circle in china.

I put this info not to make $ for my own. just to introduce you all a useful resource to get your DIY main/2nd mirror. like my 254 mm f5 main/2nd mirrors 1/20 accuracy for only 1600RMB or S$330. if you buy from gso totally cost you S$700.

orly_andico · Post by **orly_andico** » Thu May 06, 2010 5:49 pm

Wow is that for real?

Nobody believes the 1/10 or 1/20 of synta or GSO... even hubbleoptics with their "test data" has been shown to overstate e.g. they claim 0.98 strehl but it turns out to be 0.85 strehl

That said, S$ 330 for a 10" mirror is mind-boggling. Somebody will have to pony up S$ 330 and test it out..

My 10" mirror needs aluminizing so I would be first in line to try a mirror for $330 but a C9.25 fell into my lap (ebay auction gone wrong...) and my wife will kill me if I buy more stuff :-P

Chris · Post by **Chris** » Thu May 06, 2010 6:05 pm

OMG! I feel scammed, I just bought a 4.5" reflector for $330, and it don't even work with my camera

dragoncai2008 · Post by **dragoncai2008** » Thu May 06, 2010 6:06 pm

Hi Buddy, never mind, looks you are not so familiar with that. you may go to GSO website, you can see their mirrows are labled with 1/10 above!

S$330 is just too cheap to believe, right? no problem. I am not forcing you to buy. I am still struggling to collect all necessary parts to DIY my 254 tube, the major issue is the alluminium tube! I plan to complete this OTA tube in 6 months, once I finished and tested, I will invite you who are keen to watch and feel. let real observation to show you.

orly_andico · Post by **orly_andico** » Thu May 06, 2010 6:11 pm

@dragoncai

i am also in search of a 10" tube!!! Sonoco sells sonotube only in 50m length minimum! so I am stuck. Am trying to build the dob as a truss dob but am having trouble finding appropriate truss tubing material...

do update us if you can find some tubing material. i think 10000rpm is also looking for tube.

BTW the 200mm tube you are selling... is this also made by the Chinese master optician? f/4 is pretty fast it would be quite a challenge to make a good mirror that fast..

dragoncai2008 · Post by **dragoncai2008** » Thu May 06, 2010 6:32 pm

@orly andico

I got a friend, who told me he saw a tube factory in KL may have big diameter tube. I have asked him and waiting for his reply in next week. if I got positive reply, will share with you all.

the 203/f4 i am selling here is not made by that mirror master. If anyone is interested in seeing some photos to prove the mirror accuracy I will email you. I just dont know how to put on pictures within this topic!