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GSO 8x50mm Straight Through Achromatic Finder - Black

4.2 (13 Reviews) Read Reviews Write Review
Brand GSO
Part Number GS850-B
Availability available

Product Info

Manufacturer Description

Replace the small 24mm or 30mm finder telescope that came with your telescope with this excellent 50mm achromatic finder! With this finder, you will actually start seeing many of the faint fuzzies you're searching for. This same finder is sold by one of the "Big Three" telescope companies and several other smaller companies under their own brand names for significantly higher prices.

This is a very high quality yet economical finder. It features a multi-coated achromatic objective and single eyepiece cross-hairs that allow for precise centering of faint objects. This finder provides an inverted, reversed image and has a black tube finish with black dewshield/eyepiece as shown in the accompanying photo. The finder comes with two plastic end caps. The eyepiece body is made of high-quality molded ABS plastic. The rest of the finder is beautifully CNC-machined from aluminum and powder coated to a glossy finish. The inside of the tube is painted a flat black and the inside of the dewshield features v-grooves to minimize spurious reflections and maximize contrast.

To focus the finder:
(i) Turn the focus lock ring (on the tube right behind the dewshield) towards the eyepiece as far back as it will go.
(ii) Turn the objective dewshield in either direction until you reach focus while looking into the eyepiece.
(iii) Turn the focus lock ring towards the dewshield until it locks into place and can turn no farther. Focus will be locked in this position.
Please note: The eyepiece crosshairs are not focusable.

You can purchase an optional GSO quick-release dovetail bracket and a variety of dovetail bases for different applications. Or you can mount the finder in your own 50mm finder bracket if the bracket has an inner diameter larger than 53mm.

Specifications:
Total length = 239mm (9.41")
Weight = 10.8 oz
Tube diameter = 53mm (2.09")
Dewshield diameter = 58mm (2.28")
Made in Taiwan

Reviews

4.2 (Based on 13 Reviews) 92% of reviewers recommended this product.
Rating Distribution
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    1. Guest

      Skill Level
      Unknown
      Time with Product
      Unknown
      User Notes:
      Review by Mark John
      1505212603
      Sep 12, 2017

      4.0 Very Nice For The Price

      Pros:

      Cons:

      Comments:

      I've always preferred a straight-thru finders. This finder is well made, sturdy, and crystal clear optics. Great value for the money. My only "complaint" is that it does not come with an o-ring, which is not mentioned in the description. I would like to have known that prior to ordering. I had to later order an o-ring separately. Agena sells then for $1.50 but required a $10 order. So that kind of annoyed me. I order the o-ring from Scope Stuff just out of principle...

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    2. Guest

      Skill Level
      Unknown
      Time with Product
      Unknown
      User Notes:
      Review by Martin of South Dakota.
      1320624000
      Nov 6, 2011

      4.0 Nice bright finder.

      Pros:

      Easy to Use,Quality Lenses,Accurate,Strong Construction

      Cons:

      Comments:

      I like this finder. Faint objects show up in it better than a similar 8x50 finder I have. It looks nice also.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    3. Guest

      Skill Level
      Unknown
      Time with Product
      Unknown
      User Notes:
      Review by JCBC of Kentwood, MI.
      1319846400
      Oct 28, 2011

      5.0 Great View Finder

      Pros:

      Easy to Use,Accurate,Strong Construction,Compact,Quality Lenses,Lightweight

      Cons:

      Comments:

      I use it my AT6RC and do the job nicely :)
      Recommended

      Bottom Line: Would you recommend this item? No
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    4. Guest

      Skill Level
      Unknown
      Time with Product
      Unknown
      User Notes:
      Review by astrozelle of Lockport, New York.
      1272931200
      May 3, 2010

      5.0 An Excellent low-cost finder

      Pros:

      Compact,Quality Lenses

      Cons:

      Comments:

      This GSO 8x50 finder strikes me as an excellent value. Optically, while not at the Takahashi level, it's quite sharp and generates pinpoint star images that become comatic only at the very edge of the field-of-view. Eye relief is very comfortable, and fit and finish is very good. I've purchased more than one of these GSO's, and they serve admirably on a couple of high-end refractors.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    5. hhowardn

      hhowardn New Member

      Skill Level
      Unknown
      Time with Product
      Unknown
      User Notes:
      1258563660
      Nov 18, 2009

      5.0 Such a Deal

      Pros:

      Great optics, Great build quality, Low price

      Cons:

      None at all

      Comments:

      I bought this to replace the 6x30 finder on my Meade SN6. It fit right into my Orion bracket which I already had. With a straight through finder, I do not need to also have a red dot finder. It is really hard to believe that Agena can sell such a substantial piece of equipment so cheaply. Great optical quality and build quality and at this price, who could complain?

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No
    6. doug76

      doug76 New Member

      Skill Level
      Unknown
      Time with Product
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      User Notes:
      Review by Doug76 of SE Louisiana.
      1249516800
      Aug 5, 2009

      4.0 A fine finder scope

      Pros:

      Strong Construction,Quality Lenses

      Cons:

      Comments:

      I bought my first one to use on my new Astro-Tech AT90EDT Apo Refractor, which did not come with a finder of any kind.
      I liked it so well that when I received an 80mm f/15 Carton Achro Refractor I bought one for it also.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    7. Guest

      Skill Level
      Unknown
      Time with Product
      Unknown
      User Notes:
      Review by Irineu of Campinas, SP - Brazil.
      1243382400
      May 26, 2009

      4.0 Good for the price.

      Pros:

      Accurate,Strong Construction,Quality Lenses

      Cons:

      Difficult To Focus,Unstable

      Comments:

      It isn't wonderfull but has a low price. It justifies the buy.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    8. AstroGuy1

      AstroGuy1 New Member

      Skill Level
      Unknown
      Time with Product
      Unknown
      User Notes:
      Review by cosmic109 of Georgia.
      1237852800
      Mar 23, 2009

      4.0 GSO 8X50 Finder Scope

      Pros:

      Bright and sharp images,Economical,Very well constructed

      Cons:

      Images are reversed,Inverted image

      Comments:

      Many telescopes today are sold with the ubiquitous 6X30 finder scope. Usually they are ok for planet hunting and larger solar system objects. But when you begin to seek out many of the Messier objects, a finder with a little more aperture comes into play. This was the case when I purchased my C80ED, so I decided to purchase a GSO 8X50 finder scope.

      This 8X50 finder is very well constructed. The unit has dark black crosshairs that are easily visible at night, and focus is achieved by loosening the collar around the objective cell and twisting the lens housing to the left or right to bring things into focus. Once focus is obtained, the position is held in place by twisting the collar back against the lens cell. The images are inverted and reversed, but you quickly become familiar with this and adjust your movements accordingly. Views through this unit are surprisingly bright and sharp, and any chromatic aberrations are minimal. By the way, the lens itself is achromatic and multi-coated for better light transmission.

      If you're looking for an economical replacement for your rather small existing finder, this GSO 8X50 should be on your short list.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    9. AstroGuy1

      AstroGuy1 New Member

      Skill Level
      Unknown
      Time with Product
      Unknown
      User Notes:
      Review by Wolf359 of Texas.
      1233705600
      Feb 3, 2009

      4.0 The perfect size finder scope

      Pros:

      Balance of aperture size,Cheap,Reliable,Pairs well with a Telrad

      Cons:

      Not RACI,Easy to misalign

      Comments:

      I'm always amazed when this isn't the default finder scope size on some 8 inch and larger Dobs. There is a vast improvement in finding deep space objects versus a 6X30 finder scope. The 50mm aperture seems to be the point at which I can easily tell some objects such as globular clusters, open clusters, and the brighter nebulas from the surrounding stellar field. And size-wise, this is the largest aperture I can go with on my 12 inch Dob before the tube starts to feel crowded.

      Some people prefer the RACI (right angle correct image) type finders because they require less yoga skills to view through. However, I prefer the straight-through type because (I think) they match up better with a Telrad when placed adjacent to each other. I can quickly close in on the general area of the object I'm searching for with the Telrad, then fine tune my search with the finder scope.

      I also like straight through finders because I can search with both my eyes. For example, I'll look through the finder with my right eye and overlay that view with the regular view through my left eye. Sometimes, this works good enough for me that I don't even use the Telrad. Yes, this requires getting into an awkward position where I'm practically laying on the telescope with an arm draped across, but you love your telescope, so why not give it a hug?

      My only complaint with this finder is that the spring loaded, three screw stalk doesn't hold the finder scope tightly enough. It's really easy to bump out of place which can be annoying. However, for the price and everything else it does well, it hard to be too critical of this one fault.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    10. melonman

      melonman New Member

      Skill Level
      Unknown
      Time with Product
      Unknown
      User Notes:
      Review by melonman of Minnesota.
      1227052800
      Nov 18, 2008

      4.0 GSO 8X50 straight - through finder

      Pros:

      Nice sharp finder

      Cons:

      Not right angle

      Comments:

      My early experience in astronomy had to do with looking at the moon and planets. With these bright objects you can easily line up a small 6X30 finder in one eye while looking at the object with the other. But what do you do with Messier or NGC levels of dimness? My solution was to get a bigger finder. Real astronomy businesses sell the larger 50mm and even 80 mm diameter finders. With these, even my older eyes (59 yrs.) can see many star clusters and some galaxies (M81&M82) through an 8X50 thinking I would use the "line it up method". I chose a GSO 8X50 finder after shopping around from Agena Astroproducts. [I purchased] the finder, the stand, dovetail mounting bracket and adjustable holding ring. Initially I had to adjust the focus by turning the dew shield and objective end and was surprised at how sharp and pleasing the views were through this little wide field scope. My telescope is a home built truss dob and when I mounted the finder on it, I found it slanted downward more than I could adjust for. However, then I noticed I had turned the mounting bracket or dovetail with the tightening screw nearer to the front end of the newtonian this caused the front of the finder to dip down when tight in the dovetail. Turning the bracket around with the set screw a bit to the rear solved that problem.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    11. cosmic109

      cosmic109 New Member

      Skill Level
      Unknown
      Time with Product
      Unknown
      User Notes:
      1195729260
      Nov 22, 2007

      4.0 GSO 8X50 Finder Scope

      Pros:

      Very well constructed; Bright and sharp images; Economical

      Cons:

      Images are reversed and inverted

      Comments:

      Many telescopes today are sold with the ubiquitous 6X30 finder scope. Usually they are ok for planet hunting and larger solar system objects. But when you begin to seek out many of the Messier objects, a finder with a little more aperture comes into play. This was the case when I purchased my C80ED, so I decided to purchase a GSO 8X50 finder scope from Owl Services.

      This 8X50 finder is very well constructed. The unit has dark black crosshairs that are easily visible at night, and focus is achieved by loosening the collar around the objective cell and twisting the lens housing to the left or right to bring things into focus. Once focus is obtained, the position is held in place by twisting the collar back against the lens cell. The images are inverted and reversed, but you quickly become familiar with this and adjust your movements accordingly. Views through this unit are surprisingly bright and sharp, and any chromatic aberrations are minimal. By the way, the lens itself is achromatic and multi-coated for better light transmission.

      If you're looking for an economical replacement for your rather small existing finder, this GSO 8X50 should be on your short list.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No
    12. Wolf359

      Wolf359 New Member

      Skill Level
      Unknown
      Time with Product
      Unknown
      User Notes:
      1188897780
      Sep 4, 2007

      4.0 The perfect size finder scope

      Pros:

      Good balance of aperture/size, cheap, reliable, pairs well with a Telrad.

      Cons:

      Easy to misalign, not RACI (could be a plus to some users).

      Comments:

      I'm always amazed when this isn't the default finder scope size on some 8 inch and larger Dobs. There is a vast improvement in finding deep space objects versus a 6X30 finder scope. The 50mm aperture seems to be the point at which I can easily tell some objects such as globular clusters, open clusters, and the brighter nebulas from the surrounding stellar field. And size-wise, this is the largest aperture I can go with on my 12 inch Dob before the tube starts to feel crowded.

      Some people prefer the RACI (right angle correct image) type finders because they require less yoga skills to view through. However, I prefer the straight-through type because (I think) they match up better with a Telrad when placed adjacent to each other. I can quickly close in on the general area of the object I'm searching for with the Telrad, then fine tune my search with the finder scope.

      I also like straight through finders because I can search with both my eyes. For example, I'll look through the finder with my right eye and overlay that view with the regular view through my left eye. Sometimes, this works good enough for me that I don't even use the Telrad. Yes, this requires getting into an awkward position where I'm practically laying on the telescope with an arm draped across, but you love your telescope, so why not give it a hug?

      My only complaint with this finder is that the spring loaded, three screw stalk doesn't hold the finder scope tightly enough. It's really easy to bump out of place which can be annoying. However, for the price and everything else it does well, it hard to be too critical of this one fault.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No
    13. melonman

      melonman New Member

      Skill Level
      Unknown
      Time with Product
      Unknown
      User Notes:
      1167174000
      Dec 26, 2006

      4.0 The GSO 8X50 straight - through finder telescope

      Pros:

      For the money, a nice sharp finder.

      Cons:

      I now use a red dot finder with it. Right angle is more comfortable.

      Comments:

      My early experience in astronomy had to do with looking at the moon and planets. With these bright objects you can easily line up a small 6X30 finder in one eye while looking at the object with the other. But what do you do with Messier or NGC levels of dimness? My solution was to get a bigger finder. Real astronomy businesses sell the larger 50mm and even 80 mm diameter finders. With these, even my older eyes (59 yrs.) can see many star clusters and some galaxies (M81&M82) through an 8X50 sthinking I would use the "line it up method I chose a GSO 8X50 finder after shopping around for $43 dollars from Agena Astroproducts. The price included the finder, the stand, dovetail mounting bracket and adjustable holding ring.

      Initially I had to adjust the focus by turning the dew shield and objective end and was surprised at how sharp and pleasing the views were through this little wide field scope. My telescope is a home built truss dob and when I mounted the finder on it, I found it slanted downward more than I could adjust for. However, then I noticed I had turned the mounting bracket or dovetail with the tightening screw nearer to the front end of the newtonian this caused the front of the finder to dip down when tight in the dovetail. Turning the bracket around with the set srew a bit to the rear solved that problem.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No
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      Specifications

      Manufacturer GSO