ZWO ASI 178-Cool ?

[Spaced Out]

Hi All

I’ve been thinking about a cooled camera for imaging galaxies with my Skywatcher 200 PDS (and maybe the 130 PDS).

I thought that the ZWO ASI 178mm-cool might fit the bill, not sure if that would be a good choice but looks like they’re discontinued anyway. I was just wondering if there is a newer camera with similar or better specs now available ?    

Thanks

[tooth_dr]

Hi Gary

The 178 has very small pixels, I have one of these myself, non cooled version.

It has 2.4um pixels.  So at 1000mm focal length on the 200PDS, you will have an image scale of 0.49/px which is very oversampled.   It would also present a tiny FOV, but for galaxies, maybe?  You'd still need to bin it to get a decent image scale, so at 3x3, you'd be imaging at 1.5"/px, and have a 1032 x 693 resolution.

 

Edited March 24, 2020 by tooth_dr

[Spaced Out]

Thanks mate.

Yep small FOV and high resolution is what I was after I guess for galaxies with my 1000mm ? I wasn’t quite sure if the 178-cool would be suitable or not. Can’t honestly say I understand much about pixels and image scale etc !

Any other suggestions for suitable cameras to investigate ?

[wimvb]

Altair and qhy produce(d) a camera with the same sensor. These may still be available.

What's your budget? There are several alternatives available from ZWO, QHY, Altair Astro. 

Edited March 25, 2020 by wimvb

[wimvb]

11 hours ago, Spaced Out said:

Thanks mate.

Yep small FOV and high resolution is what I was after I guess for galaxies with my 1000mm ? I wasn’t quite sure if the 178-cool would be suitable or not. Can’t honestly say I understand much about pixels and image scale etc !

Any other suggestions for suitable cameras to investigate ?

My ASI174MM has 5.86 um pixels, and at 1000 mm focal length, my images are still moderately oversampled most of the time. Detail in your images will depend more on sky conditions and tracking (guiding) accuracy, than on pixel size. With smaller pixels, the signal will be smeared out across more pixels. Each pixel collects light from a smaller section of the sky than if you have large pixels.

With 1000 mm fl, and even with 650 mm fl, a 3.8 um pixel camera has enough "resolution" for any practical purposes, even for galaxy hunting. As for sensor size, you can always crop empty sky from a galaxy image. Small sensors won't give you larger or higher resolution images than large sensors. But they will give you smaller files to work with.

The main reasons I bought an ASI174MM, was that it has large pixels with a high full well capacity, and good pixel scale (arcseconds of sky covered by each pixel) at the focal length I wanted (1200 - 1600 mm at that time). Price was also an important factor. The small sensor meant that files wouldn't be large, and stacking would be faster. 

Edited March 25, 2020 by wimvb

[Adam J]

Get something with a 290 mono  and use the short exposure method. 2000x5s subs.

[Spaced Out]

On 25/03/2020 at 19:28, wimvb said:

My ASI174MM has 5.86 um pixels, and at 1000 mm focal length, my images are still moderately oversampled most of the time. Detail in your images will depend more on sky conditions and tracking (guiding) accuracy, than on pixel size. With smaller pixels, the signal will be smeared out across more pixels. Each pixel collects light from a smaller section of the sky than if you have large pixels.

With 1000 mm fl, and even with 650 mm fl, a 3.8 um pixel camera has enough "resolution" for any practical purposes, even for galaxy hunting. As for sensor size, you can always crop empty sky from a galaxy image. Small sensors won't give you larger or higher resolution images than large sensors. But they will give you smaller files to work with.

The main reasons I bought an ASI174MM, was that it has large pixels with a high full well capacity, and good pixel scale (arcseconds of sky covered by each pixel) at the focal length I wanted (1200 - 1600 mm at that time). Price was also an important factor. The small sensor meant that files wouldn't be large, and stacking would be faster. 

Thanks all for your replies, I might look into a 2nd hand asi 174mm. My budget is £0 at the moment but I am just planning ahead for future savings !

[wimvb]

4 minutes ago, Spaced Out said:

Thanks all for your replies, I might look into a 2nd hand asi 174mm. My budget is £0 at the moment but I am just planning ahead for future savings !

When you are in the market for a new camera, use a fov calculator to compare sensors.

http://astronomy.tools/calculators/field_of_view/

Also, for deep sky work, always go for a cooled camera. Dark frames need to match light frames in temperature, which is much easier to do if you can set the temperature of the camera.

[Spaced Out]

1 minute ago, wimvb said:

When you are in the market for a new camera, use a fov calculator to compare sensors.

http://astronomy.tools/calculators/field_of_view/

Also, for deep sky work, always go for a cooled camera. Dark frames need to match light frames in temperature, which is much easier to do if you can set the temperature of the camera.

I've been using that already and looking for smaller FOVs, trouble is it isn't all about FOV is it, gets a bit more complicated than that. I would be looking for cooled for sure.

Thanks again👍