Magnification question

[bendiddley]

Can someone tell me how you obtain magnification when taking a photo through a telescope? I assume you can put an EP between the camera and scope somehow but I don't know how, what sort of EP you need to do it and are there any other accessories you need for it? Also is it common practice to use an EP to magnify the image or do most people just use prime focus? I guess it depends what you are imaging but I can't help thinking that most things are going to be very small this way??

[DaveS]

Magnification isn't something that astrophotographers use, we talk instead about focal length. You can use an eyepiece and snap photos of teh moon using a cameral held to it in plce of your eye, but nearly all serious AP-ers will image at the focus of the system, which may include some kind of Barlow or Powemate to increase the FL for planetary imaging. Most DSOs are so big that it's often a struggle to fit them onto the chip.

[Tinker1947]

Prime Focus is purely the scope and the camera nothing else, the scope turns into a large telephoto lens, you will need a EQ Mount and suitable scope, a Dob is ok for the Moon but that's about its limit..there are adapters just depends on your camera and focuser.....

http://www.firstlightoptics.com/adapters.html

DSLR to SCT....

CCD to Focuser...

DSLR to Focuser

[bendiddley]

Ok, so if I had the camera without a barlow just straight in the focuser and pointed the scope at the orion nebula I would get a decent sized image ie. not a tiny spec, or would I need a barlow to get closer in? Sorry if these are dumb questions, I'm very new to all this.

[Tinker1947]

Save yourself a lot of money and buy this, read it a couple of times.....

http://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

[brantuk]

You need to be thinking more about image scale on the chip rather than magnification - and focal ratio (typically f-5 or less). Steve Richards book recommended above explains it all. With your 200P and the 1000D dslr you'll have no problem capturing M31 or M42 and M45 - some of the larger popular objects.

You may need a coma corrector and possibly some spacers to deal with getting the focus point right. But the main problem you will deffo have is the EQ3-2 mount - which is really unsuitable for your setup - it's not going to be easy imaging once you have the scope, counterweights, camera and all the other gear on it.

For dso a/p and the 200P, you really need an NEQ6 pro or absolute minimum HEQ5 pro. The mount is critical in imaging. Hth

[jambouk]

Plug your scope and camera into this website and you get an idea of how it will be framed:

http://www.12dstring.me.uk/fov.htm

I think your set up would result in this:

James

[ronin]

Just about everything is "prime focus" so magnification does not come into it.

For planets people tend to use the scope but add a barlow or powermate into the optics to increasde the size of the image that is formed. Simply the planets are bright enough to allow this to be a reasonable approach.

The image size is determined by the focal length of the scope and the angular size of the object - simply geometry.

[bendiddley]

You need to be thinking more about image scale on the chip rather than magnification - and focal ratio (typically f-5 or less). Steve Richards book recommended above explains it all. With your 200P and the 1000D dslr you'll have no problem capturing M31 or M42 and M45 - some of the larger popular objects.

You may need a coma corrector and possibly some spacers to deal with getting the focus point right. But the main problem you will deffo have is the EQ3-2 mount - which is really unsuitable for your setup - it's not going to be easy imaging once you have the scope, counterweights, camera and all the other gear on it.

For dso a/p and the 200P, you really need an NEQ6 pro or absolute minimum HEQ5 pro. The mount is critical in imaging. Hth 

Thanks. I must add quickly before any one else comments, I will not be using my 200p dob or my EQ3-2 mount. The plan is to get a 130pds and possibly and EQ5 or HEQ5, I am currently using the EQ3-2 for wide field camera only imaging and dob for visual work.

[bendiddley]

Just about everything is "prime focus" so magnification does not come into it.

For planets people tend to use the scope but add a barlow or powermate into the optics to increasde the size of the image that is formed. Simply the planets are bright enough to allow this to be a reasonable approach.

The image size is determined by the focal length of the scope and the angular size of the object - simply geometry.

Thanks