Sensor Size / FOV

[JunglistRex]

Hi,

I have been reading about imaging and had some basic questions to see if my understanding is correct.

This site https://agenaastro.com/articles/guides/cameras/zwo-astronomy-cameras-buyers-guide.html gives formula for calculting FOV as:

FOV in arc minutes = (3436*D)/L

Where D is dimension of sensor (mm) and L is focal length of telescope (mm)

So for a SkyMax 102 and a ASI224MC, I make the calculation

(3436 * 6.09) / 1300 = 16.1 arc minutes

My understanding is the moon is ~30 arc minutes in diameter. So am I right in saying that this combination of camera and scope would fit approximately half the moon into frame?

Thanks

[DMihai]

Hello,

I am very new to this hobby but here is my take:

You are comparing the sensor's diagonal with the moon's diameter. In this case, yes, the ratio will be close to 1:2. However you will not capture anywhere near half of the moon's surface.

For a more graphical representation you can use this calculator:

https://astronomy.tools/calculators/field_of_view/

Switch it to imaging mode, select your telescope, camera and the moon as your target and click "add to view".

 

Hope this helps,

Mihai

[michael.h.f.wilkinson]

That sounds about right. You can always do a mosaic to capture the whole moon. MS-ICE (Image Compositing Editor) is perfect for this (and free). Stellarium also has a handy tool to visualise the FOV, if you enter the right scope and camera specs

[JunglistRex]

10 minutes ago, DMihai said:

Hello,

I am very new to this hobby but here is my take:

You are comparing the sensor's diagonal with the moon's diameter. In this case, yes, the ratio will be close to 1:2. However you will not capture anywhere near half of the moon's surface.

For a more graphical representation you can use this calculator:

https://astronomy.tools/calculators/field_of_view/

Switch it to imaging mode, select your telescope, camera and the moon as your target and click "add to view".

 

Hope this helps,

Mihai

Thanks

This was actually going to be my next question. I had already used that site and put in SkyMax and ASI224MC and messed around with some settings and it didn't seem to match up.

For example, if you also add a 0.5x reducer, my calcations would be:

(3436 * 6.09) / (1300 * 0.5) = 32.2 arc minutes which i think should be enough to frame the whole moon but the result on that site is:

https://astronomy.tools/calculators/field_of_view/?fov[]=1945||266||0.5|1|0&solar_system=moon

So, I have two further questions at the moment:

Why doesn't it seem to match up? (probably me calculating wrong!)

Would a focal reducer actually work with that set up?

[JunglistRex]

16 minutes ago, michael.h.f.wilkinson said:

That sounds about right. You can always do a mosaic to capture the whole moon. MS-ICE (Image Compositing Editor) is perfect for this (and free). Stellarium also has a handy tool to visualise the FOV, if you enter the right scope and camera specs

Thanks, will look at these now

[michael.h.f.wilkinson]

7 minutes ago, JunglistRex said:

Thanks, will look at these now

Creating a mosaic in MS-ICE is a piece of cake. Once you have stacked each of the panels, and sharpened them, just put the results into MS-ICE and away you go. The main thing is to ensure enough overlap between adjacent panes of the mosaic (20-25% is generally enough), and it does help to keep the exposure times roughly constant. MS-ICE can also handle very big images. This is a 155 Mpixel mosaic taken with my C8 and ASI183MC.

[DMihai]

I think you forgot that in your calculations you used the sensor's diagonal not width or height.

As you can see from your link the sensor's diagonal matches with the moon's diameter...

[JunglistRex]

3 minutes ago, DMihai said:

I think you forgot that in your calculations you used the sensor's diagonal not width or height.

As you can see from your link the sensor's diagonal matches with the moon's diameter...

 

Ok understood, i thought it must be my calculations. I was following example given in link provided in OP but had misunderstood it slightly

[JunglistRex]

7 minutes ago, michael.h.f.wilkinson said:

Creating a mosaic in MS-ICE is a piece of cake. Once you have stacked each of the panels, and sharpened them, just put the results into MS-ICE and away you go. The main thing is to ensure enough overlap between adjacent panes of the mosaic (20-25% is generally enough), and it does help to keep the exposure times roughly constant. MS-ICE can also handle very big images. This is a 155 Mpixel mosaic taken with my C8 and ASI183MC.

 

Very nice!

Have checked out Stellarium and can see how that works. Will read up more about ICE

[vlaiv]

ICE has been shut down and you can no longer download it from Microsoft website - you get "We're sorry, this download is no longer available." when you try to download it for some reason.

Microsoft Ice website is still up and running though: https://www.microsoft.com/en-us/research/product/computational-photography-applications/image-composite-editor/ but when you click on download - you get the message.

It is still available thru way back machine:

https://web.archive.org/web/20190223050207/https://download.microsoft.com/download/7/3/9/73918E0B-C146-40FA-B18C-EADF03FEC4BA/ICE-2.0.3-for-64-bit-Windows.msi

As alternative - you can try this:

http://jaggedplanet.com/imerge.asp

 

[michael.h.f.wilkinson]

11 minutes ago, vlaiv said:

ICE has been shut down and you can no longer download it from Microsoft website - you get "We're sorry, this download is no longer available." when you try to download it for some reason.

Microsoft Ice website is still up and running though: https://www.microsoft.com/en-us/research/product/computational-photography-applications/image-composite-editor/ but when you click on download - you get the message.

It is still available thru way back machine:

https://web.archive.org/web/20190223050207/https://download.microsoft.com/download/7/3/9/73918E0B-C146-40FA-B18C-EADF03FEC4BA/ICE-2.0.3-for-64-bit-Windows.msi

As alternative - you can try this:

http://jaggedplanet.com/imerge.asp

 

Typical! MS produces a good, solid app, and then they cancel it. It was just about their only product I liked.

I don't think imerge supports full colour 16 bit per channel (48 bpp) images, which MS-ICE does. It was far less powerful and easy to use last time I tried

[michael.h.f.wilkinson]

I think I might give hugin another try. It is a free stitching tool, that is apparently now mature

[michael.h.f.wilkinson]

Just tested Hugin: no go for solar or lunar astronomy, as it doesn't like me entering a field of view smaller than 1 degree.

[vlaiv]

39 minutes ago, michael.h.f.wilkinson said:

I don't think imerge supports full colour 16 bit per channel (48 bpp) images, which MS-ICE does. It was far less powerful and easy to use last time I tried

Indeed - I have old version and I remember it having problems with higher bit count.

On website - it says it can handle 16/32 bit Fits though:

But it also says that it can only handle monochrome fits:

So I guess some fiddling - each channel stitched separately sort of thing would work on higher bit images.

Alternative that I did not mention is ImageJ and different stitching plugins.

https://imagej.net/Image_Stitching

but that is sort of advanced use (people don't seem to like ImageJ for some reason)?

[michael.h.f.wilkinson]

15 minutes ago, vlaiv said:

Indeed - I have old version and I remember it having problems with higher bit count.

On website - it says it can handle 16/32 bit Fits though:

But it also says that it can only handle monochrome fits:

So I guess some fiddling - each channel stitched separately sort of thing would work on higher bit images.

Alternative that I did not mention is ImageJ and different stitching plugins.

https://imagej.net/Image_Stitching

but that is sort of advanced use (people don't seem to like ImageJ for some reason)?

Just tested Affinity Photo on some difficult solar H-alpha data, and it did an excellent job. Still need to fiddle with it a bit , but it looks very promising

[michael.h.f.wilkinson]

OK, so here is a solar H-alpha mosaic made using Affinity Photo. This was a difficult data set, with lots of unevenness in the background due to problems with flats, and yet Affinity Photo has made a pretty decent mosaic. It isn't perfect, but a good result on very challenging data.

[davew]

5 hours ago, vlaiv said:

It is still available thru way back machine:

Cheers for the link Vlaiv. Always good to have the app download just in case once it's been dropped by Microsoft. 

Dave.