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Undersampled images


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As I sit "patiently" awaiting the arrival of my ED72 I am thinking long and hard about the camera I am going to get with it. In discussions with Steve at FLO, the ZWO 183mm (cooled) was mentioned and it it gives a nice FOV, wider than my old combination of the ED80 and Atik 414ex. I developed more of an interest in narrowband and want a larger FOV to capture some of the larger targets, so the 183 was a tempting prospect with 1.18"/pixel to 1.38"/pixel with the reducer (which I am also waiting "patiently" for ?)

However, once you start looking you see the Zwo1600MM which has a slightly larger FOV and comes in at 1.86"/pixel without the reducer and slightly undersampled with the reducer at 2.19"/pixel.

Then there is the comfort of staying with CCD rather than CMOS and the Atik 383l+ which has a similar FOV as the 1600 but I am familiar with the workflow needed for CCD imaging. However, this route is undersampled with and without the reducer at 3.12"/pixel and 2.65"/pixel - but it does sound like a lovely camera.

From various searches I have been reading about undersampling and the dangers of blocky stars, but also that this might not be a major issue for a wider field unless imaging at or over 4"/pixel. So, for the sort of imaging that I am looking to do, will it make that much of a difference whether I go for the 183/1600 or the 383L+ (other than price) and is the issue of undersampling not really an issue with a wider field of view? Does the 383 push it a little too far, meaning the 1600 is the best compromise?

My old combo of the Atik414ex and ED80 was undersampled at 2.61"/pixel but I never noticed any major issues there, despite the smaller FOV - although that may be down more to my lack of skill that anything else!

I know this is probably one of those "which is the best camera for...." posts and there is probably no hard and fast answer, but I'm just interested in people's views on the "danger" of undersampling, or whether it is not worth worrying about when imaging at a wider FOV? I'm not an expert and don't really understand all the ins and outs of selecting cameras, so perhaps might be putting too much stock in simple figures and need some real world arguments from people who actually know what they are talking about....

Cheers

Mark

 

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Fit a circular aperture mask and reduce the scope'd resolution and your oversampling problems will disappear ?

More seriously, I think undersampling is only a real issue if you blow the image up too large - you should view images at a small enough scale that the eye can't distinguish individual pixels.

If blown up larger a good resampling method will round off your small stars.

 

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I did presume issues with blocky stars can be processed out, but I guess that becomes harder the more undersampled the images are. I can't imagine ever having to blow the images up too big, but a little bit of tolerance is always welcome! ?

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