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Homemade finderscopes vs commercial ones...

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#1 Earthbound1

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Posted 19 August 2019 - 06:13 AM

I'm toying around with the idea of making a custom finderscope for my 12" f5.8 reflector and was curious as to any suggestions I can get. I'm wondering if I can make a better finder than what a Meade Adventure 80 would be. I want a really wide field of view and low magnification... I have a 70x500 objective to play with as a potential starting point, but am concerned that the 500mm is a little too long for my purposes in this case... Thanks in advance for ALL the thoughts and advice you guys share! - Chip

#2 NinePlanets

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Posted 19 August 2019 - 06:59 AM

All my finder scopes are home made.

But then again, so are all my telescopes.

And yes, a larger aperture, wide FOV, and erect image will spoil you. smile.gif  It's nice to see the ring nebula as a disk and a globular as a globular and the rings of Saturn in your finder. Use a good eyepiece like a surplus Erfle or Koenig.

 

This is the 67mm on my 10". The commercial 45-degree image erector is frosting on the cake. It's nice to not have to break your neck when searching the zenith.

 

 

 

 

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#3 NinePlanets

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Posted 19 August 2019 - 07:10 AM

Here's another of my 17x67mm finders on my 8" f/16:

 

 

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#4 NinePlanets

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Posted 19 August 2019 - 07:11 AM

And a view of Venus through the eyepiece in the daytime sky.  wink.gif

 

 

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#5 Jon Isaacs

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Posted 19 August 2019 - 10:45 AM

I have messed around with finders, modifying finderd, adding optics etc.

 

For me, 500 mm is too long if you're using 1.25 inch eyepiece's, that's a maximum field of 3.1 degrees.  

 

I use a StellarVue 50 mm finder that provides 6.8 degrees at 8.3 x. For me, FOV is more important than a little extra aperture. If I want more resolution, I just crank up the magnification, it will split Castor..

 

Weight is an important factor, particularly for Dobs. For every added pound with a finder, 2 to 6 pounds of countetweight is needed.. very few of the objects I am hunting for are visible in an 80 mm, it's about star hopping.

 

Jon


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#6 Lighthound

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Posted 19 August 2019 - 04:08 PM

Check out SurplusShed.

They usually have a nice selection of acro lenses in stock.

Some are multi-coated.

 

I picked up some 42mm fl142mm (F/3.3) coated doublets to play around with.

 

I also noticed 66mm X fl180 or so I think.

 

66mm F/3 would make for a nice wide finder.


Edited by Lighthound, 19 August 2019 - 04:09 PM.

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#7 howardcano

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Posted 19 August 2019 - 04:26 PM

One needs to be careful ordering from Surplus Shed. Just diameter and focal length is insufficient for specifying a suitable objective lens for a finder. The lens you get might have significant bending, which is great for whatever design it was originally intended, but unsuitable for an object at infinite distance. It's a good idea to contact them regarding a potential purchase to make sure the lens is what you want.

 

But if they have what you need, the prices can be very good!


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#8 izar187

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Posted 19 August 2019 - 04:57 PM

I'm toying around with the idea of making a custom finderscope for my 12" f5.8 reflector and was curious as to any suggestions I can get. I'm wondering if I can make a better finder than what a Meade Adventure 80 would be. I want a really wide field of view and low magnification... I have a 70x500 objective to play with as a potential starting point, but am concerned that the 500mm is a little too long for my purposes in this case... Thanks in advance for ALL the thoughts and advice you guys share! - Chip

In addition to the Surplus Shed option, there is the half binocular.

Where you split an old pair of bino's in half, keeping the center focuser assembly intact for your finder.

You just have to pick the bino with the eye relief and field in view that you want.

 

Another much lighter weight option, is to make a set of 2 point open or peep sights.

You get no dew issues, though sometimes frost.

Unlimited field.

Can cost less than a red dot.

Be as simple as two screws mounted in line somewhere on the ota. Where ever convenient for using them.  


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#9 Earthbound1

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Posted 20 August 2019 - 09:25 AM

Thanks all! Very good suggestions!


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