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Question about Meade ETX 90 天文望遠鏡

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發表於 2010-1-14 16:30:09 | 顯示全部樓層 |閱讀模式
Is this telescope good?? Is it is using m35 mount if I like to connect with DSLR???
發表於 2010-1-14 17:50:39 | 顯示全部樓層
本帖最後由 mca 於 2010-1-14 17:53 編輯

ETX90 (my sample) is really good, as recognized in recent star party comparing to Tak 6 cm florite, Meade APO 8 cm and Celetron-5.  ETX90 has an optional adapter with M42 thread for connecting DSLR. (You need to buy the camera adapter ring separately. )   Note that the focal length of ETX90 is long (1250 mm) at f/13.8, so it is less suitable for taking wide field pictures like the 8cm f/6 refractors do.
發表於 2010-1-14 17:53:41 | 顯示全部樓層
Herewith is some information from the dealer in Hong Kong on this telescope.
http://www.grandeye.com.hk/pc_etx.htm
Also you can find some information on how to photograph with this telescope from Meade’s instruction manual (see page 40).
http://www.meade.com/manuals/Tel ... -autostar%20man.pdf
QUOTE
For photography with the Meade ETX 90 you need the Meade #64 T-Adapter.
The Meade #64 T-Adapter threads to the rear cell of the telescope, followed by a T-Mount appropriate to the user’s brand of 35mm camera. In this way, the camera body is rigidly coupled to the telescope's optical system, which in effect becomes the camera's lens (see PHOTOGRAPHY, page 40).
UNQUOTE
發表於 2010-1-14 17:58:45 | 顯示全部樓層
I'm using it now, I found the fork mount on the etx-90 cos' quite a lot of limitation. You might bypass this issue by using an eye-piece connected mount, but the narrow optical path alway cos' some internal reflection, especially when taking photo of the moon & sun. the big disc generated quite a prominent unwanted internal flare to lighten the black area. I would suggest to buy a similar version that made by Bosma & a GOTO mount which HKAS recommended(I forgot the brand name). I think that will be a better solution, if mounting a camera is ur main concern.
發表於 2010-1-14 18:15:43 | 顯示全部樓層
I hate the fork-mount of ETX90.  So just bought the ETX-90 tube only.
發表於 2010-1-14 20:30:17 | 顯示全部樓層
I think that ETX series isn't good for photo. First, that is alt-az mount, don't expect too much the photo, because of rotation field. Second, it can not move over 70 degree; otherwise, the camera will hit the mount, and then broken. For visual is fine, but that is not good for photo.
 樓主| 發表於 2010-1-16 01:13:51 | 顯示全部樓層
oh..... too bad.... I just get it.... at http://www.dchome.net/viewthread.php?tid=814432

anyway, where can I buy good tube, the seller don't have any tube include.....
 樓主| 發表於 2010-1-18 12:13:19 | 顯示全部樓層
HI all, if the 可 調 式 投 影 相 機 接 口 mentioned at http://www.grandeye.com.hk/pc_etx.htm is good??
發表於 2010-1-19 15:08:34 | 顯示全部樓層
我在十年前 (菲林時代) 已有那個 Meade 可 調 式 投 影 相 機 接 口 ,價不貴但作用有限,因為係剩 tube ,tube 內不能加 eyepiece 作高倍放大攝影 (比較之下,高橋的 Extender tube 就可內加目鏡但貴幾倍),
最不好是前端只得 1.25" 口徑,用一粒香雞縲絲收實,筒身又幾吋長,加個重相機就把整體的光輻弄曲。

現在是數碼時代,高倍攝影加個 Barlow 挍惦,雖然 extender tube + 目鏡投影也可以,但已少用了

如果你已有 ETX90,還是買個 ETX90 專用的 extender kit 作鏡後攝影用,有兩段,不過只能用 pri focus 攝影 (焦距約 1450 mm) ,問下 Grandeye 啦
發表於 2010-1-20 18:01:15 | 顯示全部樓層
本帖最後由 jojomamani 於 2010-2-6 11:26 編輯

8# carfield

That's my set up for mounting DSL camera(s) on my etx-90.
My APS sized camera is a Canon 500D with 650nm Infrared corrected
The full frame camera is a Canon 5DII for normal visible light.
The image were shoot indoor through the window without glasses in the optical path between the etx-90 & the buildings. shutter were released after 10sec. with mirror locked.
The image that took by the ext-90 & with cameras were sized down to 50% linear.

The eyepiece adaptor is good on etx-90, it yield a better balance in compare with the direct photography rear port. Also it make possibility to take photos with objects at the top of the sky.
         
          B'cos of the position of the finder is quite close to the eyepiece outlet. it's better to use small APS camera. Pls. check the following pictures.
         
          Note that my eyepiece is a very short one, I've been using a longer one cos' I was considering the obstruction with the smart finder, but I found the longer light travelling path cos more internal reflection that lower the contrast of the image, even I matt the internal tube with velvet paper. Plus this lens is long enough already, longer the exiting path narrow down the field of view. Not good at all. You may hv to reconsider whether you need the "variable projection camera adaptor".

          If u compare the image carefully. The image with eyepiece adaptor is not as sharp as the one that took with the direct rear port. I believe it's not my focusing problem. It may be the double image cos by the thin mirror. It's a trade off with the better balance. I keep both setup as a possibility to shoot object that higher than 70°, which the direct mount to the rear port can't do.

100120ETX90-135.JPG

100120ETX90-136.JPG

100120ETX90-137.JPG

100120ETX90-138.JPG

100120ETX90-140.JPG

100120ETX90-141.JPG

100120ETX90-142.JPG

Note the image is vertical fliped

APS frame with eyepiece adaptor

APS frame with eyepiece adaptor

APS size frame camera

Full frame with eyepiece adaptor

Full frame with eyepiece adaptor

Full frame 35mm frame camera, the image circle is not enough to fill up the frame.

The #64 T-adapter(it comes with 2 parts; An adaptor tube between the rear opening of etx-90 & the T-ring,  also an extension tube for full frame  35mm camera) are always hv a balance issue when using it, the weak fiction of the mount is not that good on holding it! expecially using both parts with the full frame camera. Pls. check the image.

Set up with short #64 T-adaptor tube, the focal length is 1250mm f/13.8
100120ETX90-143.JPG

100120ETX90-144.JPG

100120ETX90-147.JPG



APS frame with short tube only

APS frame with short tube only

APS size frame camera with basic #64 T-adaptor

full frame with short tube only

full frame with short tube only

Full frame 35mm size camera with basic #64 T-adaptor, again the image circle is not able to fill up the whole frame.

Set up with both #64 T-adaptor tubes, the focal length will be longer up to 1450mm f/16

100120ETX90-145.JPG
100120ETX90-146.JPG


APS frame with both tubes

APS frame with both tubes

APS size frame camera with both #64 T-adaptor

full frame with both tubes

full frame with both tubes

Full frame 35mm size camera with full #64 T-adaptor, That's the only set up able to shoot full frame 35mm. but the weight & the unbalanced torque/moment make the whole setup very difficult to operate. Not recommended!
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