Hot Pink Pleiades

Wondering why hot, blue, young stars would have a pink "chromosphere." 50mm f/1.8 II, 7D, ISO 1600, 5s@f/2.5, daylight WB. Lens? Sensor? Exposure?

Stacked RAWs (DSS) 100% crop:

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Chromatic aberration. If you were to shoot something white in full sun you would see CA at the edges of the brightest white areas as well. It's all about bringing all the colors of refracted light to one focal point. By adding more glass elements in the light path the misalignment can be corrected.

Corrected optics in a telescope come at a price. Even high end lenses are not corrected completely, high quality triplet refractors however are about as good as it gets for astro.

Here's one example: http://www.optcorp.com …-refractor-telescope.html

Nighthound wrote in post #17227084
Chromatic aberration.

Thanks for the explanation.

Oddly, pictures taken with my 50D (same aperture) don't show the problem. If anything, Rigel should have a pink shell.

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When focusing, use the LiveView and 10x mag.
You will see the larger hallow appearing stars to shrink in size as you focus manually then depending on direction of rotation you would go through Pink to Almost neutral then Blue and again hallow fattening stars.
You should keep your focus at the transient point between the colors to have the sharpest, least CA but then if you thought you could get rid of CA just buy buying some expensive glass, you are wrong. You can minimize but never omit. Sir Isaac Newton proved this long back (Keeping his name on a newer generation of telescopes for ever) and no point for us to discuss on the know subject.
So learn who to deal with CA or enjoy the view as very correctly you have used the aberration on first image and title of this post.
Keep up the good work.

Thanks, samsen, for the encouragement. I probably missed focus slightly with the 7D. I do use 10X live view but even bumping the camera can shift focus sufficiently on the cheap 50mm to degrade the image. I got lucky with the 50D.

OVF , read post #12 on this thread : https://photography-on-the.net …/showthread.php​?t=1403892 . It might help you with your focusing cause you can use the technique whether mounted on a mount , scope or tripod .

Ron:
1- Your suggested method is good but useful only for AF lenses to beging with. Might be useful here for OP if using that nifty50 lens.
But most of my astro lenses or my camera when connected to telescope via adapter are fully Manual and believe this is true for many other users.
2- At least in my hand, it is impossible not hit that focusing ring at least once, accidentally if not several times in darkness of that cold night!
I strongly suggest everyone to learn how to focus on Full Manual mode, all the time for astro shooting. Once learned, it is not that difficult to follow however you remain within the limitations of your lens' IQ at the end that has no way to bypass (Except that hurting technique of stopping down, one or one and a half F).

Celestron wrote in post #17236800
OVF , read post #12 ...

Done.

samsen wrote in post #17236816
Ron:
1- Your suggested method is good but useful only for AF lenses to beging with.

You are correct . I mentioned nothing about manual focus lens because a lot of people are using AF lens . MF lens are usually Prime Lens which the only ones I have are my old Film Camera Lens .

samsen wrote in post #17236816
But most of my astro lenses or my camera when connected to telescope via adapter are fully Manual and believe this is true for many other users.

If your camera is attached to your scope with any adapter you should not be using the lens to focus with . It should be the same as I do where the scope is focused , not the camera lens even if a lens is also used even the adapter that screws to the front of the lens then inserted into the diagonal and locked in . If your adjusting the Focus ring still on the lense then I have to admit out of 13 yrs of my imaging I have never seen or used that technique . Most any other time the camera is attached with an adapter that replaces the lens .

samsen wrote in post #17236816
2- At least in my hand, it is impossible not hit that focusing ring at least once, accidentally if not several times in darkness of that cold night!

The only time I hit the focus ring is when i am putting the lens cap on .

samsen wrote in post #17236816
I strongly suggest everyone to learn how to focus on Full Manual mode, all the time for astro shooting. Once learned, it is not that difficult to follow however you remain within the limitations of your lens' IQ at the end that has no way to bypass (Except that hurting technique of stopping down, one or one and a half F).

And your suggestion are very good Samsen if people are using Prime Lens that are MF all the time and they can do the same with AF lens also . But to be honest i don't believe most people are using MF lens . And besides i have read where many here are using a zoom lens . To be honest i have not read where any are using MF lens . I don't believe Canon has any MF lens in their lineup but if they do i have missed them big time but i will go back to their site and check those lens again . But if I'm wrong then perhaps those that are using MF lens will read this and prove me wrong , and if so i just have to say i overlooked and mis read what they used .

Samsen , i checked out Canon lens and every lens i see is an EF (Electronic Focus) lens includeing all the Prime Lens , Telephoto lens , Tilt shift lens . I see none that are MF so why would most people be using MF lens here on this forum if canon does not have any ? I know there is other brand cameras but i think you'll find the same there also . Now if it's an AF lens but on a different camera that does not recognize the lens then yes you have no choice but to MF if the lens works on that particular camera with an adapter . I have some old Pentax Primes that are film lens and they are MF reguardless and i have an adapter that i ca use to be able to use those lens on my Xsi and they do work great but they are MF . But anyway here's the link to Canon USA and you can check it out , no MF lens can be found there .

http://consumer.usa.ca​non.com …ts/cameras/ef_l​ens_lineup

The 50mm is the only fast lens I have; everything else is f/3.5 and slower. Manual focus is the only way I use the lens, even when taking normal daylight or flash pictures. Even releasing the focusing ring after focusing will shift focus slightly as there is considerable slop in the lens barrel. Its AF is at best inconsistent and useless to get reliably sharp pictures.

I've since put a length of painter's tape around the inner barrel to introduce friction and to stabilize the lens elements laterally. I can now focus and release the ring without it shifting.

Edit: Light "pollution," setting moon, and clouds but the focus is now good.

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