Generic Ramsden SR4mm


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Brand and Model:Generic Ramsden SR4mm
Price ($USD):Not available
Type:Ramsden
Focal Length:4 mm
Barrel Size:1.25 in.
Apparent FOV:35.0 degrees
Field Stop Dia.:0.0 mm
Eye Relief:2 mm
Elements:2
Weight (lbs):
Description:

Vote Highlights Vote
Generic Ramsden SR4mm
I've owned a couple of these cheap eyepieces. In my f/8 Newtonian it is practically useless, being almost impossible to bring to focus. It will give high power views of the Moon but they tend to be very fuzzy and noticably dim, dim enough that there's no need for a moon filter.

But the one that came with my old Jason 60mm refractor performs fairly well with that scope, which is a f/12. Chromatic abberation is a problem and it is still hard to bring to focus but I have seen both the Cassini division and multiple bands on the surface of Saturn with it, maybe not crystal clear but distinguishable. The images are not dimmed quite as much either but the effect is still bad enough that it is only usable on very bright objects like the moon and planets.

Difficulty in achieving focus, serious chromatic aberration, and severe dimming are the biggest problems with this eyepiece. The only pro I can think of is the price, you can probably get one for free from anybody who has bought a cheap scope and upgraded the eyepieces. And they make great dust caps or paperweights when you upgrade yours.

Overall Rating: 2
Optics:2 Value:5
Weight: 20 (Notable Vote)
Date:
By: Whyzard
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=129635


Generic Ramsden SR4mm
Not as bad as everyone states. When compared to a 4mm plossl from GTO I noticed very little difference. Brings in planetary details well enough. Given that on smaller reflecters (114mm or so) no 4mm will perform well, this is a reasonible purchase. Why spend more on a plossl 4mm when it cannot outperform this 4mm by much when used with a smaller scope.

Overall Rating: 6
Optics:5 Value:7
Weight: 10 (Trustworthy Vote)
Date:
By: nafa
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=76185


Generic Ramsden SR4mm
I've used one of these SR4mm with a cheap Meade refractor before, and I would recommend using a cardboard tube and 2 magnifying glasses instead.

If you buy a scope and it comes with this eyepiece, you probably bought the wrong scope. Any decent scopes now come with Kellner or SMA eyepieces.

Its been stated a thousand times, stay away from department store telescopes.

Overall Rating: 0
Optics:0 Value:0
Weight: 10 (Trustworthy Vote)
Date:
By: canuck
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=66737


Generic Ramsden SR4mm
I (stupidly) bought a "department store" telescope when I got into astronomy over 5 years ago, and it came with one of these "SR4mm" eyepieces. Sorriest thing I have ever seen. You can't use it for anything, and all you have to look through is a pinhole. The inside of the barrel is not even painted black to increase contrast! If the telescope you are looking at comes with one of these eyepieces, don't buy it.

Overall Rating: 0
Optics:0 Value:0
Weight: 5 (Veritable Vote)
Date:
By: noahm3
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=125197


Generic Ramsden SR4mm
It is not all that bad for $5. I once glimpsed at a third band on Jupiter through my first beginners' telescope I had since 1998 (I was 8 years old), a 60mm Jason Refractor, but I can't see Saturn's Cassini division which is readily visible with the GTO plossl (my favorite EP) in the same scope. It only works with long focal length telescopes only. This 2-element EP is an excellent eyepiece for solar projecting in small refractors due to its cheap price and high magnification. If you have extra money, I would reccomend a low/mid power eyepiece and a barlow rather than the SR 4mm.
PROS-cheap, good for solar projecting, it works
CONS-2 elements, only good with high f/ratios, moon is "soft"

Overall Rating: 5
Optics:5 Value:4
Weight: 5 (Veritable Vote)
Date:
By: scopedreamer2032
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=118278


Generic Ramsden SR4mm
First, SR4mm is made of two identicle lens much like an OR without chromatic correction. It doesn't look like a K, which has asymetric lens, as far as I can tell. SR4mm is usually comes free with toy scopes, but I it not THAT bad for F/9 optics. It has serious chromatic error, and poor eye releive, but the image is quite bright and sharp for cheap uncoated optics. Even after getting a Japanese OR6mm, I sometimes still used the SR4mm for that extra magnification. The best bet would be replacing it with a OR/Possol 4mm.
I wouldn't classified it as 1 because 1 is reserved for H/Hm, and 0 for all the plastic eyepieces.

Overall Rating: 3
Optics:3 Value:4
Weight: 2 (Unreliable Vote)
Date:
By: Anonymous (xxx.xxx.173.142)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=81997


Generic Ramsden SR4mm
Greetings,
this eyepiece is garbage and earns a zero.
Stop! I gave it a 1 at three reasons:
1. You can break out the uncoated lenses
and use it as a collimation tool.
2. You can use it as a dustcap.
3. At starparties use it for guests and
save your expensive eyepieces become
dirty or broken.

Overall Rating: 1
Optics:1 Value:1
Weight: 2 (Unreliable Vote)
Date:
By: Anonymous (xxx.xxx.57.22)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=48343


Generic Ramsden SR4mm
The older versions work very well in F9 or slower systems and make an ideal unit for double star work in long refractors. Had an older 5mm version and it worked as well or better than a 5mm Ortho in an F9 achromat. The problem with many of the newer production versions is uncoated lenses and acrylic elements instead of glass. However if made properly it is an ideal high power ocular for slow systems delivering high contrast and excellent light transmission. Also the eye relief is actually not bad contrary to popular opinion considering the extreme short focal lengths involved.The prolem is really not the eyepiece but rather the telescopes these are included with. They are usually sub-par and not able to deliver sharp imagery over 40X per inch

Overall Rating: 7
Value:10
Weight: 1 (Unreliable Vote)
Date:
By: Anonymous (xxx.xxx.59.25)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=595785


Generic Ramsden SR4mm
Forgot to mention in previous comments that at f/10 or higher you will
be exceeding 50x per inch. Main optics must be excellent. At these
magnifications this is primarilly an eyepiece that is excellent for
very close doubles at or exceeding Dawes limit, and for Mars with a small
disk.

Overall Rating: No Vote
Weight: <none>
Date:
By: Anonymous (xxx.xxx.162.192)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=44409


Generic Ramsden SR4mm
A poor performing eyepiece in ANY refractor. However, believe it or not,
it actually performs very well in long focus reflectors of f/10 or higher, or with a barlow at an effective f/10 or higher. In my f/12 SCT it works very well on close double stars and high power lunar and planetary. Many of these eyepieces are junk with plastic barrels no coatings etc. Look for the all metal
coated japanese examples. You will be surprised at how well they work when used
in longer reflectors. Of course a .965 to 1.25 will be required.

Overall Rating: No Vote
Weight: <none>
Date:
By: Anonymous (xxx.xxx.162.192)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=44408

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