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Ring Nebula in Lyra (M57)...a planetary nebula 2,300 light-years from Earth. 

This is an experiment to see how feasible it is to capture deep sky objects using the ZWO ASI120MC camera instead of the Canon DSLR. The advantages in doing so are getting larger object because of the smaller sensor and not wearing out the shutter of the DSLR....the disadvantages are a much lower resolution and a more grainy image with little extra detail (again because of the smaller sensor). Just like with the experiment in using a Barlow lens with a DSLR to image this object, the conclusion is that it's probably better to crop a larger, hi-res image but I wanted to know if this was possible and what the quality would be like if it was possible. Apart from the difficulty in finding the object with such a small sensor, the process was fairly easy with fewer of the problems that cropped up with Barlow experiment. And the result, though a bit grainy, does show some previously unseen details like the nebula's distinctive shape and the white dwarf in the centre of the nebula.


3 x 45 second exposures

33 x 20 second exposures

37 x 10 second exposures

17 dark frames

No flat or bias frames

Processed in Nebulosity and Photoshop.

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Some detail beginning to show through there but you're not getting a bigger image because the sensor is smaller, nor will you get lower resolution and more grain just because the sensor is smaller.

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The advantages in doing so are getting larger object because of the smaller sensor and not wearing out the shutter of the DSLR....the disadvantages are a much lower resolution and a more grainy image with little extra detail (again because of the smaller sensor)

I found this, but I am not sure about the real motif.

1)Pixel size of ASI is a little small than Canon T3. So it can capture better small details.

2)The resolution (image scale) with ASI is more accuracy than Canon T3 for the same image.

3)For small objects the small size of sensor doesn't create any loss.

It has all to be better than Canon T3 for these small DSOs.

Maybe the problem are with the noise, bayer matriz, spherical distortion in the microlens, distance between the pixels.

My experience with Moon shows that ASI is very better than Canon T3 for details of surface. Where signal is more strong than DSOS.


Adjust gain and colors with ASI120MC aren't easy, also.

I think that ASI mono with filters has better performance because of the real number of pixels. No microlens. No bayer matriz. As all mono camera, it can have better performance.

getting larger object because of the smaller sensor

As camera in direct focus mode doesn't  amplify images, the large appearance is due to resolution: arcsec per pixel.

With the same telescope and accessories the area of an image will be small on small sensor than on large sensor. If the sensors have the same number of pixels, the small sensor will have "more" pixels to that small area of image.

Edited by jsmoraes
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