Field of view simulator - really cool!

[StuartT]

I'm sure the old timers on here know all about this, but I am sharing it for all the other beginners (like me). It's a really nice way to see what you can expect to see through your telescope. You can select the scope, the eyepiece, your camera, your target. 

Just amazing!

https://www.12dstring.me.uk/fovcalc.php

Edited March 9, 2021 by StuartT

[Budgie1]

There's also Astronomy Tools and Stellarium has a FOV plug-in where it puts your FOV on the screen so you can see what it's like as you scroll across the sky.

[John]

First Light Optics have provided a similar tool here:

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

One thing to bear in mind with these is that they are simulating the field of view, ie the area of sky that will be seen and the relative size of a particular target when using a particular scope / eyepiece combination but they won't simulate how bright or well resolved a particular target object will be when you actually observe it.

 

Edited March 9, 2021 by John

[Tiny Clanger]

39 minutes ago, John said:

First Light Optics have provided a similar tool here:

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

One thing to bear in mind with these is that they are simulating the field of view, ie the area of sky that will be seen and the relative size of a particular target when using a particular scope / eyepiece combination but they won't simulate how bright or well resolved a particular target object will be when you actually observe it.

 

Yes, also I wonder about the static Solar System planet images too ... given the variation in apparent size as they (and we) zap around their orbits, there's a considerable variation . Even in the 8 months I've been observing, the apparent shrinkage of Mars has been striking !

Heather

 

[Pixies]

One of the useful features of FLO's Atronomy Tools FOV calculator, is that you can superimpose multiple FOV indicators over a single image, and so compare scope/EP/camera combinations

[StuartT]

7 minutes ago, Tiny Clanger said:

Yes, also I wonder about the static Solar System planet images too ... given the variation in apparent size as they (and we) zap around their orbits, there's a considerable variation . Even in the 8 months I've been observing, the apparent shrinkage of Mars has been striking !

Heather

 

Maybe it's actually shrinking Heather... 😱

[scotty38]

As above you can compare eyepieces for example but here is where my head hurts. Take the example below. I modified the FOV for the ES to make my point but as you can see the FOV is essentially the same so this is what you see when you look through the eyepiece correct? If that is the case then how can one be 27x and the other be 20x? What fundamental schoolboy error am I making ?

 

Once posted I can see the info is hard to read so the two eyepieces are a 40mm WO at 70 degrees and an ES 30mm 100 degrees edited to be 95 degrees to create the same FOV

 

Edited March 9, 2021 by scotty38

[John]

If you do put a 30mm ES 100 eyepiece into the StellaMira 80mm ED F/10 do please post a photo - it's a 3 inch format eyepiece

That aside, when actually observing you would expect the apparent size of the Moon to be larger given the additional magnification but when comparing eyepiece fields, I guess that the sim can only change the apparent size of the field of view rather than the target object.

This is the un-edited version with the fields of view the correct relative sizes:

 

[vlaiv]

42 minutes ago, scotty38 said:

Once posted I can see the info is hard to read so the two eyepieces are a 40mm WO at 70 degrees and an ES 30mm 100 degrees edited to be 95 degrees to create the same FOV

Same FOV - but different AFOV and magnification.

FOV represents how much sky will you see and how will object appear in relation to that background sky.

It's a bit like watching the same movie on your smart phone and on large cinema screen. Main character will take same proportion of the scene - but view on your phone will be small and very narrow but one on cinema screen will be huge and span almost all of your field of view.

Above compares how much of the scene you'll see and what the size of the main character will be in relation to the scene - but it does not show whether you are watching it on your smart phone or 100" plasma screen 6 feet away

 

[scotty38]

16 minutes ago, John said:

This is the un-edited version with the fields of view the correct relative sizes:

 

Yep I realise that, as I said I specifically edited the eyepiece data so they both "matched" as it were otherwise my question makes even less sense 🙂

[scotty38]

15 minutes ago, vlaiv said:

Same FOV - but different AFOV and magnification.

FOV represents how much sky will you see and how will object appear in relation to that background sky.

It's a bit like watching the same movie on your smart phone and on large cinema screen. Main character will take same proportion of the scene - but view on your phone will be small and very narrow but one on cinema screen will be huge and span almost all of your field of view.

Above compares how much of the scene you'll see and what the size of the main character will be in relation to the scene - but it does not show whether you are watching it on your smart phone or 100" plasma screen 6 feet away

 

I guess this is it (the bit I put in bold). The previous sentence would be correct if you were shown the two separate views but here we show the plasma view and the smartphone view as "looking the same"

Edited March 9, 2021 by scotty38

[vlaiv]

Just now, scotty38 said:

I guess this is it. The previous sentence would be correct if you were shown the two separate views but here we show the plasma view and the smartphone view as "looking the same"

Indeed - one must make target look the same for comparison purposes.

You can't really show AFOV on computer screen because actual field of view on computer screen will depend on how close to computer screen you are. In that sense - both views are relative but can be "normalized" to common thing - in this instance target size.

[scotty38]

I mean logic tells me and it does work that if you want to compare two eyepieces have two separate instances of the calculator tool running. I tried that with my "example" and they now show differently as would be the case 🙂