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Find the right eyepiece XLSX

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13 replies to this topic

#1 dgordontx

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Posted 02 March 2018 - 02:21 PM

Finding the right EP can be a little bit of a pain, especially for those of us who are fairly new. Attached is a fairly completed spreadsheet you can use for 1.25" EP selection.

 

Directions:

     Fill out the aperture and focal length of your scope.

     Fill out your min and max pupil size (if known).

 

What will happen:

     The magnification and exit pupil will update. They will also turn red if they are outside of the capabilities of you or your scope.

     The true field of view will also update for you to compare. Instead of just relying on low, med, and high power, you can see that a 24mm 68deg EP gets you a wider FOV at a higher magnification than a 40mm, 40deg EP that has too high of exit pupil at too low of a magnification anyway.

 

Added bonus:

     Hold your cursor over one of the TFOVs to see the manufacturer, line, and price for that EP.

 

Coming soon: 

     Any added lines that you guys find that I should add (PM me a link)

     2" EPs

Attached Files


Edited by dgordontx, 02 March 2018 - 03:56 PM.

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#2 drneilmb

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Posted 02 March 2018 - 02:56 PM

I love it. Cool presentation of the available data. Awesome work putting all the tool-tips inside of the table. Is that data being imported from some other spreadsheet? If so, it'd be cool to have another sheet in this one with the by-eyepiece data too.

 

More itd-be-cools from someone who loves a good spreadsheet:

- Move the overall telescope and user data to a separate box at the top.

- Label what all those numbers along the top mean

- Color in the boxes on the bottom-right that are out-of-bounds for 1.25" eyepieces due to the maximum size of the field stop

- You have two definitions of max. and min. magnification, one based on exit pupil and one based on rules of thumb. Do you want some eyepieces to be out of bounds because the exit pupil is too small, but the magnification isn't all the way up to 2x/millimeter of aperture?

Screen Shot 2018-03-02 at 13.49.48.png

 

Awesome work. We all await your 2" version! (No good deed goes unpunished smile.gif

I don't know how good the conditional formatting is on Google Sheets, but I've had good luck distributing things that I want to share with the world on there by URL, e.g. https://docs.google....jjhIXr9y2ccCtPA. Then you don't have to worry about things getting out of date.

 

Thanks again, this is already useful for me.


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#3 dgordontx

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Posted 02 March 2018 - 03:13 PM

Definitely will add the labels. Will play with moving Column A data to a row along the top. I'll have to play and figure out a way to make the EP FL red if EITHER mag OR pupil is red. What I plan on doing is an edit to my original post to update the sheet and add a new post saying "Updated to include X". I don't like working with datastores that I don't directly know the person running.


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#4 dgordontx

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Posted 02 March 2018 - 03:57 PM

Updated to add instructions, place your specs above, and top several rows so you do not get lost as you scroll down.



#5 aeajr

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Posted 02 March 2018 - 06:13 PM

Get a zoom eyepiece and you won't have to swap eyepieces. :)



#6 Starman1

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Posted 02 March 2018 - 08:26 PM

Finding the right EP can be a little bit of a pain, especially for those of us who are fairly new. Attached is a fairly completed spreadsheet you can use for 1.25" EP selection.

 

Directions:

     Fill out the aperture and focal length of your scope.

     Fill out your min and max pupil size (if known).

 

What will happen:

     The magnification and exit pupil will update. They will also turn red if they are outside of the capabilities of you or your scope.

     The true field of view will also update for you to compare. Instead of just relying on low, med, and high power, you can see that a 24mm 68deg EP gets you a wider FOV at a higher magnification than a 40mm, 40deg EP that has too high of exit pupil at too low of a magnification anyway.

 

Added bonus:

     Hold your cursor over one of the TFOVs to see the manufacturer, line, and price for that EP.

 

Coming soon: 

     Any added lines that you guys find that I should add (PM me a link)

     2" EPs

17mm and 21mm Ethos are missing.  Ah, nevermind--only 1.25"

There are tons of eyepiece lines missing (more than 40) and hundreds of eyepieces, so what's the purpose of the spreadsheet?

Also, is your TFoV figure computed from TF = AFoV/M, or TF = (FS/TFL) x 57.296?


Edited by Starman1, 02 March 2018 - 08:28 PM.

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#7 dgordontx

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Posted 05 March 2018 - 11:03 AM

 

Finding the right EP can be a little bit of a pain, especially for those of us who are fairly new. Attached is a fairly completed spreadsheet you can use for 1.25" EP selection.

 

Directions:

     Fill out the aperture and focal length of your scope.

     Fill out your min and max pupil size (if known).

 

What will happen:

     The magnification and exit pupil will update. They will also turn red if they are outside of the capabilities of you or your scope.

     The true field of view will also update for you to compare. Instead of just relying on low, med, and high power, you can see that a 24mm 68deg EP gets you a wider FOV at a higher magnification than a 40mm, 40deg EP that has too high of exit pupil at too low of a magnification anyway.

 

Added bonus:

     Hold your cursor over one of the TFOVs to see the manufacturer, line, and price for that EP.

 

Coming soon: 

     Any added lines that you guys find that I should add (PM me a link)

     2" EPs

17mm and 21mm Ethos are missing.  Ah, nevermind--only 1.25"

There are tons of eyepiece lines missing (more than 40) and hundreds of eyepieces, so what's the purpose of the spreadsheet?

Also, is your TFoV figure computed from TF = AFoV/M, or TF = (FS/TFL) x 57.296?

 

AFOV/Mag. Please feel free to PM me lines or if you know a website or two that have many lines that are missing.



#8 dan_h

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Posted 05 March 2018 - 12:01 PM

Good job. 

 

I played with the pupil settings for a bit. It seems that the exit pupil is red flagged if it is smaller than the minimum value entered for eye pupil.  I don't see your reason for this as I often work with exit pupils much smaller than my eye pupil. 

 

Adding the comments was a lot of work. Unfortunately is going to be a royal pain to update.

 

dan


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#9 dgordontx

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Posted 06 March 2018 - 09:56 AM

Good job. 

 

I played with the pupil settings for a bit. It seems that the exit pupil is red flagged if it is smaller than the minimum value entered for eye pupil.  I don't see your reason for this as I often work with exit pupils much smaller than my eye pupil. 

 

Adding the comments was a lot of work. Unfortunately is going to be a royal pain to update.

 

dan

You can change the minimum pupil. I made sure the flags were based off of user input as opposed to a set number.



#10 dan_h

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Posted 06 March 2018 - 10:47 AM

 

Good job. 

 

I played with the pupil settings for a bit. It seems that the exit pupil is red flagged if it is smaller than the minimum value entered for eye pupil.  I don't see your reason for this as I often work with exit pupils much smaller than my eye pupil. 

 

Adding the comments was a lot of work. Unfortunately is going to be a royal pain to update.

 

dan

You can change the minimum pupil. I made sure the flags were based off of user input as opposed to a set number.

 

I understand that. Just caught me as a little unnecessary since eye pupils are usually opened up when observing at night. Novices may not see your reasoning and take it that a red flag means the eyepiece should not be used. Maybe change the color to caution yellow when minimum pupil is flagged .

 

dan 


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#11 Ernest_SPB

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Posted 08 March 2018 - 07:37 AM

I have modified the chart a bit, look attachment

 

Attached Files



#12 Jon Isaacs

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Posted 08 March 2018 - 07:57 AM

AFOV/Mag. Please feel free to PM me lines or if you know a website or two that have many lines that are missing.

 

 

Using AFoV/Mag can be deceiving.  Particularly if one is choosing the widest possible field of view but in general in any situation, one might choose an eyepiece that has the same or even a narrower field of view than another eyepiece simply because of the error in this approximation.

 

Jon


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#13 Ernest_SPB

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Posted 09 March 2018 - 09:16 AM

In any case representation of 1.25" eyepieces made by dgordontx very interesting, compact and useful.

Thanks a lot...


Edited by Ernest_SPB, 09 March 2018 - 09:17 AM.

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#14 dgordontx

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Posted 17 March 2018 - 10:48 AM

I cannot edit my original post anymore...

 

The updated spreadsheet is based off of applying my search ideas to Starman's research. It includes 1060 EPs and completely filterable by you.

Attached Files


Edited by dgordontx, 17 March 2018 - 10:49 AM.



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