Frame/image size with dedicated astro cam?

[imakebeer]

Newbie question here... bear with me as I may not have all the terminology exactly right...

At the moment I've been doing lucky imaging of planets with a Nikon D5500 and Canon EOS 450D - now these DSLRs have a relatively big sensor but we only use a small section of it for capture, through the 5x zoom feature in BackyardNikon/EOS or similar.

But before I activate the 5x zoom feature I can see my target as a smallish dot in a big, wide field of view - this makes getting roughly lined up with my target easy 👍

Now upgrading to a dedicated astro cam like a ZWO ASI120 or 224 isn't out of the question, but...

Don't these cameras have a much smaller sensor? I.e. they only have the the area we actually need for capture. But doesn't that mean you lose that wider of field of view making it hard to actually acquire your target in the first place prior to capturing? (Unless you have a guide cam, which I don't)

Hopefully one of you astroninjas can explain 😁

[Cosmic Geoff]

51 minutes ago, imakebeer said:

Don't these cameras have a much smaller sensor? I.e. they only have the the area we actually need for capture. But doesn't that mean you lose that wider of field of view making it hard to actually acquire your target in the first place prior to capturing? (Unless you have a guide cam, which I don't)

Yes, they do have small sensors, and the FOV is small.  Acquiring the target is a skill you just have to master.  One way of doing it is to center the planet in an eyepiece (it does not have to be in focus) and then swapping in the camera.  Another way is to use a good quality optical finder to get the planet on the sensor.  The capture software should be set to acquire all the pixels when finding the planet - you can reduce the ROI (region of interest) to e.g. 320x240 pixels once the planet is centered.

[vlaiv]

Yep - good finder properly aligned is the key (some people use eyepiece trick, or even flip mirror).

[newbie alert]

The more you do it the easier it is.. some use flip mirrors for ease of target location... 

Personally I don't have too much of an issue, as mentioned above an accurate finder helps enormously