how do i...

[tony]

maybe a daft question and the answer is probably quite simple, but, how do i get a bit closer to my target with a dslr without cropping?

zooming in using live view its only the view thats zoomed not the actual image, with a webcam i used a barlow but what about the dslr?

i'd like to get a bit closer on shots like this one. http://stargazerslounge.com/imaging-deep-sky/180858-first-bodes.html

any help much appreciated.

[Jannis]

A bit old thread i guess, but in case you're still wondering about this...:

You can use a barlow for DSLR as well, same as with the webcam. Only other way is to use a scope with a longer focal lenght, or changing to a DSLR with a smaller sensor size.

Zooming in live-view only crops the image the sensor is reading, making it easier for you to see on the small display DSLRs have. It doesn't change anything on the picture that the DSLR is actually capturing.

I would probably recomend to Not use a barlow for DSO though (at least not a strong one), unless you really need to get closer. There are several reasons for this: the higher the barlow magnification, the less light the camera recives. Example: a 500mm f/5 scope with a 2x barlow will turn into a 1000mm f/10 scope. or with a 3x barlow you get 1500mm f/15.

This means you'll need a Lot more accurate tracking/guiding due to two facts: you're getting a much longer focal lenght, meaning unaccurate tracking/guiding will show up much more, as well as you need a lot longer exposures to capture the same amount of light.

Of course, if you can do this, then it might all be good. But also, you can't overlook the fact that adding another glass between the scope and the camera almost always make the picture worse one way or another, it's only a question of how much worse. A good high quality barlow might be OK though, if you're able to track for maybe 3-5x as long without any startrails or other issues.

[Tinker1947]

You could use a EP with the facility to attach a DSLR, I know Hyperion and Pentax XW EP's support this with the use of the T-43 Adapter.

[dmahon]

"Zooming in" depends on two things

1) Focal length of the scope

2) Sensor size of the camera

To address the first: You can x2 Barlow your scope - but this also reduces the speed (focal ratio). This is bad for imaging feint DSO as you'll then have to take subs that are 4x as long. Better to buy a new scope with a longer focal lentgh but same focal ratio (which will mean a bigger aperture and more expense).

To address the second: You can crop your image (smaller sensor size), or you can buy a camera with a smaller sensor. This means either less pixels, or smaller pixels (or both). One risks loss of resolution, the other risks loss of light sensitivity.

It's always a bit of a compromise - unless you have multiple scopes and/or multiple cameras. Have a look at the first link, or download the software on the second link, to see what you can expect.

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

http://www.newastro.com/book_new/camera_app.php

[dph1nm]

Hmm - before you try any 'zooming', check your pixel size (in arcseconds) with the DSLR on your scope. There is no point sampling much below half the typical seeing for your area (which might be a few arcseconds), as you won't gain anything in terms of image resolution.

NigelM