Canon EF 50mm f/1.8 II lens for Astrophotography

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weixing
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Canon EF 50mm f/1.8 II lens for Astrophotography

Post by weixing »

Hi,
I done a simple test at various f-stop (F1.8, F2.0, F2.2, F2.5, F2.8, F3.2, F3.5 and F4.0) and below is the result showing part of the image at the edge. The image of the test shot (60s exposure @ ISO800) is at actual size and no processing had been done.

The test shot show that at F3.5 or slower, the stars image looks the best.

Have a nice day.
Attachments
Canon EF 50mm f/1.8 II Test Shot
Canon EF 50mm f/1.8 II Test Shot
EF50F18LensTest.jpg (89.75 KiB) Viewed 9086 times
Canon EF 50mm f/1.8 II
Canon EF 50mm f/1.8 II
ef_50mm_f18_ii.jpg (12.62 KiB) Viewed 9086 times
Yang Weixing
:mrgreen: "The universe is composed mainly of hydrogen and ignorance." :mrgreen:

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weixing
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Favourite scope: Vixen R200SS & Celestron 6" F5 Achro Refractor
Location: (Tampines) Earth of Solar System in Orion Arm of Milky Way Galaxy in Local Group Galaxies Cluster

Post by weixing »

Hi,
Below is the full image (no other processing done other than scaling down the image) at F1.8 and F2.8.

Can see the that the stars got tail even the image is scale down at F1.8, but the stars look ok at F2.8 when scale down.

Have a nice day.
Attachments
60s Exposure @ ISO800 F2.8
60s Exposure @ ISO800 F2.8
EF50-F2_8.jpg (50.79 KiB) Viewed 9080 times
60s Exposure @ ISO 800 F1.8
60s Exposure @ ISO 800 F1.8
EF50-F1_8.jpg (42.79 KiB) Viewed 9081 times
Yang Weixing
:mrgreen: "The universe is composed mainly of hydrogen and ignorance." :mrgreen:

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weixing
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Posts: 4699
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Favourite scope: Vixen R200SS & Celestron 6" F5 Achro Refractor
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Post by weixing »

Hi,
Some more shot at F3.2 and F4.0.

Have a nice day.
Attachments
60s Exposure @ ISO 800 F4.0
60s Exposure @ ISO 800 F4.0
EF50-F4.jpg (60.25 KiB) Viewed 9074 times
60s Exposure @ ISO 800 F3.2
60s Exposure @ ISO 800 F3.2
EF50-F3_2.jpg (54.82 KiB) Viewed 9074 times
Yang Weixing
:mrgreen: "The universe is composed mainly of hydrogen and ignorance." :mrgreen:

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kingkong
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Post by kingkong »

what caused those streaking effect at larger aperture?

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weixing
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Post by weixing »

Hi,
what caused those streaking effect at larger aperture?
I think it is cause by the uncorrected aberrations of the lens at wide open and vignetting cause by the LPR filter which is smaller than the lens.

Also, I think the pink and greenish colour at the edge is cause by the vignetting of the LPR filter when the lens is at faster f-stop... you can see some pink and greenish colour on the LPR filter if you look through it at an angle.

Have a nice day.
Yang Weixing
:mrgreen: "The universe is composed mainly of hydrogen and ignorance." :mrgreen:

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kingkong
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Post by kingkong »

yes weixing, the vignetting caused by the filter is pretty obvious....
could you please indicate where the test shots came from the full frame?
i'm curious since with the filter the shots should be from a relatively center location of the frame...
thanks

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weixing
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Post by weixing »

Hi,
could you please indicate where the test shots came from the full frame?
I have mark (by the white box) the location of where the test shot was taken from on this F3.5 image.

Have a nice day.
Attachments
60s Exposure @ ISO 800 F3.5 (location of test shot mark by white box)
60s Exposure @ ISO 800 F3.5 (location of test shot mark by white box)
EF50-F3_5.jpg (58.95 KiB) Viewed 9045 times
Yang Weixing
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kingkong
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Post by kingkong »

ah i see. thanks weixing.
did you do a comparison of the centers to see if it's usable larger than f/4?

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weixing
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Post by weixing »

Hi,
did you do a comparison of the centers to see if it's usable larger than f/4?
Center is usually ok even at wide open.

Anyway, below is the center of test shots... 300x300 pixels at the center. The open cluster in the image is the M6 butterfly cluster. :)

Have a nice day.
Attachments
Canon EF 50mm f/1.8 II (300x300 pixels of the image at the center)
Canon EF 50mm f/1.8 II (300x300 pixels of the image at the center)
EF50F18LensTest-Centre.jpg (70.02 KiB) Viewed 9031 times
Yang Weixing
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kingkong
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Post by kingkong »

ah. that's very good. thank you for sharing weixing.

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