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Why do I get 'purple' outlines on a Blackbird ? (1 Viewer)

gilesm

Member
Hello all,

During my first few days of using a scope (Meade Kestrel 20x-60x 80mm) I find that my local Blackbird has a 'purple' outline when viewed against an overcast but bright sky. The outline seems to get more intense at higher power.
When I view the same bird against a dark or colourfull background the 'purple outline' dissapears.

Can any offer a reason for this, is my scope defective ?
 
The purple fringing is coursed by the optics of the scope or camera, or a bit of both. If the scope has ED Glass lenses then it will most certainly be from the camera. Ernie
 
Hello,

Yes, I thought as much, my dealer has agreed to examine the scope and exchange it if required, whihc is nice, I fear though that my scope is not actually 'defective' perhaps it's just the way scopes work at this price point (£299.00), perhaps I will need a better scope !

(Is this what is known as Chromatic Aboration ?)
Thanks again
 
I think it's the limitations of the optics and explains why some people are willing to pay £1500 for a scope. I get a similar problem with my £130 Acuter scope under the same circumstances but I am willing to put up with it at this price level. You will probably notice the same effect with a bird on a lot of bright water, especially if you are looking into the light, or anywhere where there is strong contrast in brightness between joining edges.

If you are taking the scope back to the dealers for him to check, he might let you try out some other scopes at a similar price level and you can see if they have the same problem. You know what to look out for now. You never know, if there is another scope at a similar price which is better he might agree to some sort of exchange deal.

Ron
 
No Spring Chicken

My dealer is "Astronomy and Nature Centre" in Camridgeshire, and they have said that I should not be getting this on this scope, so he is willing to examine it and exchange if required. I am starting to think that this is just the way Scopes are at this price range, so we will see.

It's an hours drive from Ipswich though, I hope it's worth it.
 
Your scope has non ED glass so if the image is otherwise sharp there would be no point changing it unless you want to spend more and get a scope with ED glass, or try out other scopes in your price range. At present it sounds perfectly normal.

Not all ED glass is the same so if you are quite sensitive /bothered by it a cheap ED scope (well relatively) such as Acuter/celestron/Opticron may not totally cure the effect but will help. Best way is to try and compare under similar conditions.

Lots of people are endorsing the Nikon ED50 Fieldscope ... perhaps the cheapest decent ED scope but only 50mm objective.

Before you go to cambridge you could try and compare other scopes in local shops (can't think of any of the top of my head but Viking Optical is in Halesworth) and/or let other birders look through your scope.
 
Yes,Sorry to say, that is chromatic aberration and gets worst at higher powers.:-(
Regards,Steve

I thought Chromatic Aberration was a mortal sin with a harmonica until I joined Birdforum. I used to get fringing like that on bins and an old Nikon scope, the problem is that over the years I have gotten picky...now I don't have CA, but it cost a fortune! As NoSpringChicken says, if you're willing to put up with it, that's what you get at the price range, and you have to ask yourself if it really affects your birding in any serious way before you splash out lots of dosh on ED glass. That said, the ED50, although small, is a superb scope and a lot cheaper than any serious alternative.
 
Hi Sancho,Chromatic Aberration sounds like some disease.:) Just a disease of optics and our wallets and purses.:) I went the cheap route,Celestron 80 ED refractor spotter[600mm FL],not portable,not WP but no CA up to 120X,but I use 30x-60x of course.Set up on a back porch overlooking a big field.
Regards,Steve
 
Hello all,

During my first few days of using a scope (Meade Kestrel 20x-60x 80mm) I find that my local Blackbird has a 'purple' outline when viewed against an overcast but bright sky. The outline seems to get more intense at higher power.
When I view the same bird against a dark or colourfull background the 'purple outline' dissapears.

Can any offer a reason for this, is my scope defective ?

The more I think about it, and as fine as the above comments are with respect to shedding some insight into the question, I continue to wonder how much of the natural irridescence of blackbird feather coloration may contribute to your observations. I've almost never seen a blackbird where a black-blue-purple irridescence wasn't prominent in some light in otherwise normal viewing. This natural phenomenom may be all the more prominent under magnification.

If not a total explanation, I'm sure it can account for some of your observational color phenomena. I.E., you may be magnifying what is actually there, and NOT in the glass.
 
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chromatic aberration

I am almost sure now that this is something that just happens on scopes with non ED glass at the price level I paid for the scope, probably no actual 'fault' in the unit.

My dealer says he is willing to take it back 'if he judges there is a fault' and I suspect he may even refund the price against an upgrade to a better scope.

I guess in the end it's my problem for not being willing to pay enough for my first scope or not choosing correctly. Such is life, so I either 'live with it' or just invest more money in a better 'ED' scope.

I notice in the sales information for the Opticron IS series it mentions 'virtually no chromatic aberration' can anyone here tell me if that's true ? Or again does one have to purchase from the range with ED glass ?
 
I notice in the sales information for the Opticron IS series it mentions 'virtually no chromatic aberration' can anyone here tell me if that's true ? Or again does one have to purchase from the range with ED glass ?

Can't see on their website where it says that for the IS series???
 
I thought Chromatic Aberration was a mortal sin with a harmonica until I joined Birdforum.

Some people think chromatic abberation was invented by Ennio Morricone, but it is in fact much older. It was invented by the great Johann Sebastian Bach:

http://www.zweitausendeins.de/suche/?ArticleFocus=1&ord=-1&alpha=1&cat=all&q=chromatische


Anyhow, in 1968 we didn't have access to extra-low-phonetic-dispersion harmonicas in the wild, wild W.... Italy.

Charlie Bronson

PS: I know another method for putting holes into your ELs but it's noisy. And I can only do six holes at a time.
 
Some people think chromatic abberation was invented by Ennio Morricone, but it is in fact much older. It was invented by the great Johann Sebastian Bach:

Are you sure? I could have sworn it was Arcangelo Corelli in his opus 6 Chromati Grossi. Of course, this was reinvented by Miles Davis in his signature work "Kind of Blue".
 
Are you sure? I could have sworn it was Arcangelo Corelli in his opus 6 Chromati Grossi. Of course, this was reinvented by Miles Davis in his signature work "Kind of Blue".


Dear Robert!
Thank yor for this interesting information. I wasn't aware of Signore Colorellis contibution to musical spectroscopy.

Maybe we are on the trail of some deeper insight?
Some people have pointed out that Leicas have a warmer color rendition than, for example, Zeisses.
Maybe this is due to the fact that Ultravids are tuned to B flat minor, while the brighter, more "snappy" Victories are tuned to C sharp major?!

This theory can also explain why the owners of these respective instruments fail to sing in harmony when they praise their favored "instrument".

Not quite in resonance,
Tom
 
Dear Robert!
Thank yor for this interesting information. I wasn't aware of Signore Colorellis contibution to musical spectroscopy.

Maybe we are on the trail of some deeper insight?
Some people have pointed out that Leicas have a warmer color rendition than, for example, Zeisses.
Maybe this is due to the fact that Ultravids are tuned to B flat minor, while the brighter, more "snappy" Victories are tuned to C sharp major?!

This theory can also explain why the owners of these respective instruments fail to sing in harmony when they praise their favored "instrument".

Not quite in resonance,
Tom

Wonderful observations, Tom. Your working knowledge of musical spectroscopy is rare, and you seem to grasp further the working principles of optical musicology. "Deeper insight", indeed -- perhaps we two should put on our hip waders. As for keeping one's binoculars fine tuned, I couldn't choose between the B flat minor Ultravids or the C sharp major Victories -- so I got a pair of 8+12 harmonic Duovids, which of course play the 8x in C major and the 12X in G major. And by finely twisting the separate occular magnification dials at different rates I can actually see harmonic progressions. A fine instrument, literally.
 
so I got a pair of 8+12 harmonic Duovids, which of course play the 8x in C major and the 12X in G major. And by finely twisting the separate occular magnification dials at different rates I can actually see harmonic progressions. A fine instrument, literally.



C-G.
Very harmonic indeed.
But you have to take care not to drop them. if they go out of collimation you may end up with a flattend fifth that gives you a Gillespie-ing view that makes you dizzy.


Keep swinging,
Tom Dooley
 
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