saturn with 8'' reflector

[wenjha]

hi,Its my first time post picture here

I think its a global place to share pictures right?

this picture is taken by my 6'' F9 reflector(I made it myself) at 7th may

I prefer reflector because its high performance and cheap price:D

I am sorry with the wrong title, actually its a 6'' F9 reflector,

I caculated wrong, I used to measure in metre and I can't edit the title

here are the equipments I used, the mid is the 6'' F9 reflector, and this photo is taken by this

[dweller25]

Hello Wenjha,

Welcome to SGL.

That is an excellent photo, congratulations.

[MeerkatinBKK]

Hi Wenjha. That's a beautiful shot, and welcome to SGL!

Looking forward to seeing more from your home-made reflector.

Nick

[philsail1]

A lovely photo "Wenjha."

(A warm welcome to Stargazers too!).

philsail1

[omneferuss]

Hi wenjha great shot.. just to clarify, you said "my 8'' F9 reflector", but your picture annotation says "150 F9.. " ...by the scale of it , I'd guess you meant "200 F9" ? ...but f/9 + 3x Barlow.. the scale might just be the extra Fl ?

I'm interested cos my experience is with f/5 6", and I'm hoping to improve with an 'upgrade' to f/6 8" shortly... and your shot matches my expectations (hopes) in that direction.

[wenjha]

hi,I made a big mistake

I am Chinese guy, we usually use measure unit as meter not inch

so I translate 150mm to inch with a mistake

actually its 6'' inch relector

and I think there must be some error in my typing words because of my poor english, I hope you can understand me

[dweller25]

Hello Wenjha,

Your English is very good.

Congratulations on making your own scope.

Your image is exactly as I see it in a 4" refractor.

[drummerp]

Nice image especially from a scope you made, nice work and welcome to SGL.

Cheers

Neil

[Doc]

Fantastic shot and a wonderful crafted reflector.

Well done.

[Starflyer]

That's a great image, well done. That f/9 reflector is a nice looking scope and ideal for planetary imaging.

Ian

[wenjha]

thank you guys

I am very happy to join you!

[omneferuss]

Hi wenjha, thanks for clarification.. that only increases my appreciation of your shot .. excellent! ..and my admiration of your fine scope..also excellent! ..and is that a 250mm f/5 or f/6 there in the new picture too?

No error in your English or typing at all ! ..perfect like your focus in that Saturn shot and I think you had good "seeing" when you took that photo too.. ? It's much better than anything I have done !

Russ

[wenjha]

Hello Wenjha,

Your English is very good.

Congratulations on making your own scope.

Your image is exactly as I see it in a 4" refractor.

thanks dweller

Is your 4'' refractor an APO?

the performace of 4'' refractor and 6'' reflector, which one do you think is better?

[wenjha]

Hi wenjha, thanks for clarification.. that only increases my appreciation of your shot .. excellent! ..and my admiration of your fine scope..also excellent! ..and is that a 250mm f/5 or f/6 there in the new picture too?

No error in your English or typing at all ! ..perfect like your focus in that Saturn shot and I think you had good "seeing" when you took that photo too.. ? It's much better than anything I have done !

Russ

haha thank you omneferuss

you words give me a lot of confidence, thanks again

the other one of the picture is 203mm F5

but it perform poor because of the primer mirror I baught from a company

the mirror of 152mm F9 is made by an experience mirror maker

he said the PV of this mirror is 1/20

And actually it give a very good performance

I can see the airy disk of star

the seeing of that night is good, I think maybe 6

here is the video, I don't know you can visit or not

I uploaded a part of it to a chinese video site

http://player.youku.com/player.php/sid/XOTAwNDQwNDg=/v.swf

although it is compressed, but I think you can see the seeing

I stay in a big city In China: Beijing

Light polution is heavy,So I can only shoot the planetary at night

here is the moon I toke some days before, hope you like it

[johnh]

Just been looking at your image of saturn through your home made 6" F9 newtonian, this scope sounds brilliant so let us see more images from China.

With 1/20PV and F9 this scope is of the highest quality and the secondary must be absolutely tiny giving a refractor performance - all you have to contend with is the seeing. JohnH.

[dweller25]

thanks dweller

Is your 4'' refractor an APO?

the performace of 4'' refractor and 6'' reflector, which one do you think is better?

Hello Wenjha,

Yes I have a 4" APO from Japan.

Your 150mm F9 reflector is very good indeed.

I think the two scopes are very similar.

Clear skies.

[MeerkatinBKK]

Ah Beijing, a beautiful city – I've visited it a few times. I lived and worked in Hong Kong (Xiang Gang to you!) for about 14 years, but have since moved a few hours south-west to Thailand.

Again welcome, and it's good to have a member only 1 time-zone away from me!

All the best,

Nick

[omneferuss]

Yep, that Copernicus is WOW too! Long Fl, f/9 at 6" aperture surely works well for Planetary and Solar System targets -with fine optics like this... The "seeing" would've defeated the optics of my factory-made f/5 6" at this Fl.. f/27.

( and my seeing here is almost always bad, ... )

The long Fl also beats that Beijing light-pollution too, I think

The f/5 203mm might be better for Deep Sky Objects ..like dim fuzzy nebula and galaxies ..and then, maybe you'll need light-pollution filters and long exposure camera and all that.. and/or some time away from Beijing in darker skies if you can..

Meanwhile, wenjha.. please keep doing your excellent work and posting the pictures for us all to see !

Russ

[wenjha]

Just been looking at your image of saturn through your home made 6" F9 newtonian, this scope sounds brilliant so let us see more images from China.

With 1/20PV and F9 this scope is of the highest quality and the secondary must be absolutely tiny giving a refractor performance - all you have to contend with is the seeing. JohnH.

Hi, johnh

This mirror with 1/20PV is what the maker said with his experience in Foucault test, he is a amateur mirror maker and doesn't have interferometer. here is the raster pattern he offered:

And I want to prove its accuracy, I can see the airy disk with a PL4 eyepiece, but I can't take a picture with 900nc because it's too tiny,so I cover the front with a mask having a 45mm diameter hole. So the aperture is 45mm and I can take the picture of Airy disk with a 2x balow:

So, from the Rayleigh criterion, we can say that the telescope achived 1/4 PV right? and the primary mirro achived 1/8 PV right? Am I right?

the secondary is 35mm in width and I bought from a company, Its cheap and I don't the PV. So I don't think it flat enough.

I don't know how the secondary effect the telescope system?

and how to prove the 1/20 PV accuricy without a intermeferometer.

[wenjha]

Ah Beijing, a beautiful city – I've visited it a few times. I lived and worked in Hong Kong (Xiang Gang to you!) for about 14 years, but have since moved a few hours south-west to Thailand.

Again welcome, and it's good to have a member only 1 time-zone away from me!

All the best,

Nick

Haha nice to meet you MeerkatinBKK

let me know if you come again, I'll show you my 6'' F9 reflector:p

my msn:wenjha@hotmail.com

Welcome to Beijing again

[wenjha]

Yep, that Copernicus is WOW too! Long Fl, f/9 at 6" aperture surely works well for Planetary and Solar System targets -with fine optics like this... The "seeing" would've defeated the optics of my factory-made f/5 6" at this Fl.. f/27.

( and my seeing here is almost always bad, ... )

The long Fl also beats that Beijing light-pollution too, I think

The f/5 203mm might be better for Deep Sky Objects ..like dim fuzzy nebula and galaxies ..and then, maybe you'll need light-pollution filters and long exposure camera and all that.. and/or some time away from Beijing in darker skies if you can..

Meanwhile, wenjha.. please keep doing your excellent work and posting the pictures for us all to see !

Russ

thanks omneferuss

where are your place?

I will try deep sky if my planetary imaging is better enough;)

[michigander]

Nice picture and nice scope!

Dana

[omneferuss]

Hi jha, I'm in Brisbane Australia. I'm sure you'll do well with deep sky too

..but don't stop doing the planetary

[johnh]

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.

[wenjha]

Hi jha, I'm in Brisbane Australia. I'm sure you'll do well with deep sky too

..but don't stop doing the planetary

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:)