EAA - Fields of View

Atik Infinity | ZWO ASI224 | ZWO ASI178 | ZWO ASI533 | ZWO ASI294 | ZWO ASI482/485 | ZWO ASI462 | Overview | Various Cameras at the PS 72/432 | Conclusions | Links

On this page, I present some more information about EAA (Electronically Augmented Astronomy), in particular, I present the field of view for my current telescope tubes (as of April 2021) and some common astronomy cameras or sensor chips. I used the Website astronomy.tools for calculating the field of view. In any case, this is the most convenient way for doing so!

Note: The results are also valid for other cameras than those listed if they use the same sensor chip and resolution.

At the end of this page, I collect the results in a table.

 

Atik Infinity

I used the Website astronomy.tools for calculating the field of view of the Atik Infinity camera (Sony ICX825) at my current telescopes (as of April 2021).

Legend: Orange Custom Scope = eVscope; Yellow Custom Scope = PS 72/432; Cyan Custom Scope = C5; Green Custom Scope = C5R (C5 with f/6,3 reducer/corrector)

 

ZWO ASI224

I used the Website astronomy.tools for calculating the field of view of the ASI224 (Sony IMX224/225) camera at my current telescopes (as of April 2021).

Legend: Orange Custom Scope = eVscope; Red Custom Scope = PS 72/432

 

ZWO ASI178

I used the Website astronomy.tools for calculating the field of view of the ASI178 (Sony IMX178) camera at my current telescopes (as of April 2021).

Legend: Orange Custom Scope = eVscope; Red Custom Scope = PS 72/432

 

ZWO ASI533

I used the Website astronomy.tools for calculating the field of view of the ASI533 (Sony IMX533) camera at my current telescopes (as of April 2021).

Legend: Magenta Custom Scope = PS 72/432

 

ZWO ASI294

I used the Website astronomy.tools for calculating the field of view of the ASI294 (Sony IMX294) camera at my current telescopes (as of August 2021).

Legend: Magenta Custom Scope = PS 72/432

 

ZWO ASI482/485

I used the Website astronomy.tools for calculating the field of view of the ASI482/485 (Sony IMX482/485) camera at my current telescopes (as of August 2021). The cameras ASI482 and ASI485 offer the same field ov view. However, the pixels of the ASI482 have a size of 5,8 µm, whereas those of the ASI485 have one of 2,9 µm.

Legende: Orange Custom Scope = PS 72/432

 

ZWO ASI462

I used the Website astronomy.tools for calculating the field of view of the ASI462 (Sony IMX462) camera at my current telescopes (as of August 2021).

Legend: Cyan Custom Scope = PS 72/432, magenta Custom Scope = TLAPO1027

 

Overview

Field of View

I summarize the results in the following table:

 
Field of View
 
Telescope Red. FL Apert. Atik Infinity ASI224* ASI462*** ASI178 ASI533 ASI294 ASI482/485 Remarks
 
Pixel Size >
6.45 µm 3.75 µm 2.9 µm 2.4 µm 3.76 µm 4.63 µm 5.8/2.9 µm  
 
Pixels >
1392 x 1040 1304 x 976 1936 x 1096 3096 x 2080 3008 x 3008 4144 x 2822 1920 x 1080/
3840 x 2160
 
PS 72/432 --- 432 72 1.19° x 0.89° 0.65° x 0.48° 0.74° x 0.42° 0.98° x 0.66° 1.50° x 1.50° 2.54° x 1.73° 1.48° x 0.83° The largest FOV
C5 --- 1250 127 0.41° x 0.31° 0.22° x 0.17° 0.26° x 0.15° 0.34° x 0.23° 0.52° x 0.52° 0.88° x 0.60° 0.51° x 0.29° FOV like C8 with reducer
C5 f/6.3 787.5 127 0.65° x 0.49° 0.36° x 0.27° 0.41° x 0.23° 0.54° x 0.36° 0.82° x 0.82° 1.40° x 0.95° 0.81° x 0.46° FOV a little smaller as with TLAPO1027
C8* --- 2032 203 0.25° x 0.19° 0.14° x 0.10° 0.16° x 0.09° 0.21° x 0.14° 0.32° x 0.32° 0.54° x 0.37° 0.31° x 0.18° The smallest FOV
C8* f/6.3 1280 203 0.40° x 0.30° 0.22° x 0.16° 0.25° x 0.14° 0.33° x 0.22° 0.51° x 0.51° 0.86° x 0.58° 0.50° x 0.28° FOV like C5
TLAPO1027 --- 714 102 0.72° x 0.54° 0.39° x 0.29° 0.45° x 0.26° 0.60° x 0.40° 0.91° x 0.91° 1.54° x 1.05° 0.89° x 0.50° FOV a little larger that for C5 with reducer
eVscope** --- 450 114 --- 0.61° x 0.46° --- --- --- --- --- Same chip as ASI224
eVscope 2** --- 450 114 ---   0.78° x 0.57°         New chip IMX347
Vespera --- 200 50 ---   1.60° x 0.91° --- --- --- --- Same chip as ASI462

*) No longer in my possession
*) Up to app version 1.2, the eVscope used a sensor resolution of 1280 x 960 pixels. Since app version 1.3 it upscales the sensor image to 2560 x 1920 pixels.
**) Rectangular format: 2048 x 1536 pixels in Live View mode and 3200 x 2400 pixels in Enhanced Vision mode, which are upscaled from 2048 x 1536.
***) Calculated for 1920 x 1080 pixels.

Application Example 1

I operated the C8 visually using the Celestron StarSense module and found that the accessed sky object was rarely at the center after approach, but often rather at the edge of the field of view. With the 26 mm eyepiece that I had used, the field of view was 0.9°, that is, almost one degree (with an 35 or 40 mm eyepiece, the field of view would have been 1.2° to about 1.3°). With a camera/telescope combination offering a smaller field of view, the searched for object will therefore, depending on the size of the field of view, more or less often not be in the field of view and must be searched for laboriously.

Image Scale

The following table was taken from page Telescope and Sensor and simplified:

   Telescope
Image Scale ["/Pixel]
Examples
Focal Length [mm] (mm) 
Aperture [mm]
f
Pixel Size [µm]
2.4
2.9
3.75
4.63
6.45
Vespera 200 50 4 2.48 2.99 3.87 4.78 6.65
Stellina 400 80 5 1.24 1.50 1.93 2.39 3.33
TLAPO1027 714 102 7 0.69 0.84 1.08 1.34 1.86
PS 72/432 432 72 6 1.15 1.38 1.79 2.21 3.08
eVscope (2), Newton 114/450 450 114 4 1.10 1.33 1.72 2.12 2.96
Celestron C5 1250 125 10 0.40 0.48 0.62 0.76 1.06
Celestron C5R 787.5 125 6.3 0.63 0.76 0.98 1.21 1.69
Celestron C8 2032 203 10 0.24 029 0.38 0.47 0.65
Celestron C8R 1280 203 6.3 0.39 047 0.60 0.75 1.04
Celestron C8R2 1016 203 5 0.49 059 0.76 0.94 1.31

Ideally, the image scale value should lie in a range between 1 and 2. But in many cases, it is admissible that it lies outside this range... Values for the image scale above 2 are called "undersampling", values below 1 are called "oversampling".

Application Example 2

When buying a camera, I ask myself to what extent a camera with a small sensor and low resolution makes sense at all, and whether its image field could not be similarly covered by a camera with a larger sensor. For this, I compare three higher resolution cameras with the ASI224 and choose as telescope the PS 72/432 (the telescope should not really matter - not quite, as we will see...):

While the pixel size plays a role in how many pixels an object is depicted with, only the number of pixels matters when viewing photos. For the former, the finer the pixels, the more pixels an object is represented with. This can be seen with the ASI178, while the ASI294 with its larger pixels displays objects more coarsely on the same telescope. Finally, this is also reflected in the values for the magnification (see above).

If you want to achieve similar pixel numbers with the ASI294 as with the ASI224, you need a telescope with a longer focal length. For me, the "next" telescope in terms of focal length would be the TLAPO1027:

 

Various Cameras at the PS 72/432

The graph above illustrates the differences between various ASI cameras (and Sony chips) at my PS 72/432 refractor. Thus, you can quickly see that the ASI294 provides the largest field of view of all cameras and that the ASI224 (this chip is used by the original Unistellar eVscope) and the newer ASI462 (this chip is used by the Vaonis Vespera) hardly differ in terms of field of view.

ASI 462: 2.1 MP - 1936 x 1096 pixels, pixel size 2.9 µm, sensor: 1/2.8"- Sony IMX462 CMOS

 

Conclusions

The graphics and the table for the field of view allow me to quickly determine the field of view for a certain telescope/camera combination. The table for the image scale also provides hints as to the fit of telescope focal length and camera sensor (pixel size). The image scale should lie in a range between 1 and 2, But in many cases, it is admissible that it lies outside this range...

 

Links

 

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25.12.2022