saturn with 8'' reflector

[wenjha]

Hello Jha, the foucault test looks excellent and your secondary mirror does not have to be of high quality compared with primary because it will have little effect on focused image because it is at an angle errors in secondary are greatly reduced.

If you telescope snaps into focus then this is a good test or you can use a star test and look at the diffraction rings for similarity either side of focus.

Company Seven | Suiter "Star Testing Astronomical Telescopes" Second Edition Book Description Page

A star test will be more sensitive to optical errors than foucault test and rarely will a telescope give a perfect test. This should be done many times and in very good seeing to get consistency. JohnH.

thanks johnh

so what's you mean is that the Secondary only introduce astigmatism?

how to caculate the reflector system' PV if I Know the primary and secondary's PV?

"Star test ..." this book is really useful, I had an pdf verison of this book and I did the star test for my telescope, I can see the Spherical error compare the in focus image and out focus image.

just like the photo show in that book, its not equal

[omneferuss]

oh, beautiful city near the sea but bad seeing of the ocean climate:D

I will continue with the planetary, I just changed the color CCD of spc900nc with a B/W CCD. hope it will give a good improvement:)

Yep, and too much humidity lately too

Interesting you change to B/W CCD.. to do mono ?

[MidnightSun]

Great shots there jha.... I'm still trying to get a Saturn like that with my 8".....

[wenjha]

Yep, and too much humidity lately too

Interesting you change to B/W CCD.. to do mono ?

yes, I just changed the color CCD of 900nc with a B/W CCD ICX098BL, and it really has more sensitivity and resolution.

I will try mono saturn in a good weather day:)

here is the link, its easy to change

astrobond.ebrawe

[wenjha]

Great shots there jha.... I'm still trying to get a Saturn like that with my 8".....

thanks MidnightSun, I'm sure you will;)