Recently Browsing 0 members
No registered users viewing this page.
I have an Orion 8" f8 Ritchey-Chretien telescope and I'm trying to figure out the correct extension spacing from the back of my RC telescope while using a focal reducer. I'm using a TS optics 2" ccd47 .67x focal reducer and the stated distance from sensor of camera to the reducer is between 70-90mm with 85mm being the preferred or ideal distance. I've got the spacing to 82.78mm distance from the sensor and I'm curious if this distance is supposed to be "subtracted" from the back focus of the telescope with the extension rings? The telescope came with one 2 inch and two 1 inch extensions for back focus from the telescope, should I use just one 1 inch extension ring, or no extension rings and just attach the focuser straight to the back of the telescope, or a specific combination? I've included an image to help explain my question. The left side is the telescopes manual image train examples and on the right side is a representation of my question. Also when attaching the camera with the 82mm extension tubes and the focal reducer together would you insert the whole setup inside the focuser until the camera is flush with the focuser, or merely insert just the reducer in the focuser and tighten it down that way? (which im assuming is the correct way based on images I've seen with different setups)
Telescope: Orion 8" f/8 Ritchey-Chretien Astrograph (1600mm focal length)
Camera: Altair Hypercam 183c pro
Camera specs: Sensor size 1" (15.86mm diagonal)
Pixel Size 2.4um
Resolution 5440 x 3648
Hi, guys i have a Opticstar ARX200 f/3.9 astrograph which came with a f/3.9 adjustable coma corrector and I am struggling to work out the back focus! I am using a Nikon D5100 DSLR which I know the the air gap is 48mm from sensor to imaging plane.
When I use the corrector I can only gain focus with it when it is 0mm but still get major coma around edges of frame. I have tried at every point from 0-55mm and cant gain focus anywhere else??
Anyone any ideas what I am doing wrong??
Have you ever thought about why your Newton telescope has the dimension it has, primary and secondary mirror, focuser, f/number and so on?
I stumbled in to this tool Newt-Web that Kenneth H. Slater has developed further from Dale Keller's code. It's an online design tool page for Newton telescope.
It's a very intuitive page where you can put in some figures about a Newton telescope that you want to built and get back information about it's performance. It give a ray trace and important data back. From that you get understanding when a Newton telescope design is good or not.
I have done some test and written it down on my homepage so you can see the different steps and my comments:
I already know some of the physics and math, but never got to know so much in short time what happens when you change a parameter and what happens inside the telescope. Beware, I'm still in the learning process and not all what I have written is fully correct.
I recommend you to take a look at Newt-Web page even if you never will built a telescope, you get knowledge and understanding that could be very valuable when you shall buy a Newton telescope.
Can I trouble you all with a quick question?
I was 'lucky' enough to get my hands on a 200p ota from WEX Photographic in their sale last year. It cost me the princely sum of £40 but it had no base. My thinking was that I'd get the ota and then spend a bit of time over last summer making a base from some plans I'd found via a post on these pages.
All went well in that the tube fits well and moves around nicely. I fitted a telrad and thought I was good to go. However since eventually spending some time with the scope, I'm unable to reach focus.
When I place an eyepiece in the focuser, despite racking the focuser all the way out, I'm still well out of focus, and the only way I can get to focus is to partly extract the ep from the focuser, and even then, it's not particularly great.
Is this a collimation issue? Everything that I've looked at would suggest not. I've got a Cheshire and everything seems to be lining up okay, but of course I could be doing it wrong.
Any help or suggestions would be gratefully received.