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True field of view

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14 replies to this topic

#1 laedco58

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Posted 12 December 2019 - 06:26 PM

It’s been cloudy for weeks, I want to determine the field of view for my GSO RACI 8X50 finderscope so I can make appropriate size circle templates for planning star hop routes on my charts.

Larry



#2 Adun

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Posted 12 December 2019 - 06:34 PM

It's documented to be 5.6° TFOV


Edited by Adun, 12 December 2019 - 06:35 PM.


#3 skfboiler1

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Posted 12 December 2019 - 06:43 PM

According to the product page at Agena AstroProducts it is 5.4°.  That is a very good idea to make a template.  My star hopping skills improved greatly when I started doing this.  Depending on your star chart and your light pollution, the stars in the star chart, using the template, should be close to matching what you will be seeing in the finderscope. 

 

https://agenaastro.c...age-finder.html



#4 laedco58

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Posted 12 December 2019 - 07:01 PM

Thanks,
Its the finder that came with my zhumell z 12, and none of the literature stated what the field of views were for the finder scope or the included eyepieces. I’ve been thinking of mounting it on my 5” refractor as I have a telrad on the Newtonian.



#5 Rich V.

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Posted 12 December 2019 - 08:36 PM

A simple and accurate way to measure the FOV of your scope would be to locate a couple of stars that fit either side of the FOV and then go look those stars up in your chart to determine their angular distance. I'm sure you can find a pair of stars that fit your FOV and can be easy enough to locate on the chart to get an accurate measurement.

 

Rich


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#6 JOEinCO

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Posted 13 December 2019 - 08:06 AM

Thanks,
Its the finder that came with my zhumell z 12, and none of the literature stated what the field of views were for the finder scope or the included eyepieces. I’ve been thinking of mounting it on my 5” refractor as I have a telrad on the Newtonian.

In case you don't know: GSO and Zhumell and many others are one and the same. 

 

Get a second "shoe" to put on your refractor. $8-$9 on eBay. Then you can use the finder on either scope. waytogo.gif 

.

.

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#7 Jon Isaacs

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Posted 13 December 2019 - 08:14 AM

Thanks,
Its the finder that came with my zhumell z 12, and none of the literature stated what the field of views were for the finder scope or the included eyepieces. I’ve been thinking of mounting it on my 5” refractor as I have a telrad on the Newtonian.

 

I measured the TFoV of my 8x50 RACI GSO finder using a digital level. If I remember correctly, it was 5.6° but there's some error bounds. The Orion measured 5.0°. 

 

Telrads are great but a 50 mm RACI finder provides an added level of precision. My Dobs all have Telrads and RACI finders.

 

Last night I was trying to find NGC 1 with the full moon causing problems seeing this magnitude 12.8 galaxy.  I didn't find it but I did find magnitude 12.0 NGC 16, less than 1/2 degree away. Wit the finder, I could easily identify I was on NGC 16 and not NGC 1, a Telrad wouldn't have been positive.

 

Magnifying finders are also a big help under light polluted skies.

 

Jon



#8 aeajr

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Posted 14 December 2019 - 02:55 PM

I use 8x50 and telrad on my 12" Dob.

I use 5 degree circle for charts.

Edited by aeajr, 14 December 2019 - 02:56 PM.


#9 Night shift

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Posted 14 December 2019 - 09:01 PM

https://astronomy.to.../field_of_view/



#10 JOEinCO

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Posted 14 December 2019 - 10:05 PM

I'm not sure how useful that website is for determining finderscope FOVs for the OP.... shocked.gif 



#11 Night shift

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Posted 14 December 2019 - 10:31 PM

My bad, did not read the finder scope part.



#12 SloMoe

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Posted 14 December 2019 - 10:46 PM

In post #4 the OP states that might like to also know, along with the finders FOV but also the included eyepieces.

 

Here's a link to an online calculator, enter the info you have, scopes FL and eyepieces FL & FOV, click calculate

http://www.csgnetwork.com/telefov.html

 

I use this when eyepiece shopping, 

 

Then when chasing eyepieces and DSO's the exit pupil comes to factor on if the view will reveal the target.

there's a thread a bit further down in the forum addressing figuring EP.



#13 JOEinCO

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Posted 14 December 2019 - 11:54 PM

In post #4 the OP states that might like to know, along with the finder's FOV, the included eyepieces' also.....

My bad now. lol.gif lol.gif lol.gif 



#14 SloMoe

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Posted 15 December 2019 - 12:11 AM

it's really not a big deal either way, the more information we get out for any aspect of eyepiece research & purchase helps everybody

 

Here's a link to a recent topic much like this one, there's more discussion of exit pupil to give you a little bit better understanding in the hunt for DSO's.

https://www.cloudyni...il#entry9809229


Edited by SloMoe, 15 December 2019 - 12:17 AM.


#15 aeajr

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Posted 17 December 2019 - 09:51 AM

You may find this helpful.

 

Understanding Telescope Eyepieces- There are recommendations, based on budget, but the meat of the article is about understanding the issues when selecting eyepieces.
https://telescopicwa...cope-eyepieces/

 

 

Finder Scopes
https://telescopicwa...n-finderscopes/




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