Pleiades Wide Field

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Chuck
Posts: 285
Joined: Tue Mar 31, 2015 1:14 pm

Pleiades Wide Field

Unread post by Chuck »

Have wanted to try imaging the Pleiades for some time and finally had the chance over the past week. However, this was done wide field (with a prime telephoto lens) and I wasn't able to capture the detail I wanted around M45 itself. Also, the star spikes around the brightest stars are too distracting when viewing the image full resolution. Hence, it's better viewed full screen.


The image can be seen at the following Astrobin link with further image acquisition detail. Clicking the image will make it full screen and from there is a link to see it at full resolution.

Image


I was surprised to see some hints of the greater nebulosity in this FOV but much longer imaging time would be needed to get any detail, maybe sometime in the future. I have ordered some step down rings, in hopes of controlling the aperture while the lens iris is wide open. I'm hoping I can still get good images without the spikes on very bright stars.
Chuck M.

Meade 8" LX200 Classic OTA
iOptron CEM40EC and MiniPier on Meade classic field tripod
Canon EF 200mm f/2.8L II
Canon 7D Mark II
ZWO 60mm f/4.6 GS with ASI120MM-S camera
Starizona SCT Corrector II and Virtual View 2" Rotating Visual Back
Pegasus Astro Pocket Powerbox
Bruce D
Life Member
Posts: 5624
Joined: Sat Jun 14, 2003 6:10 am

Re: Pleiades Wide Field

Unread post by Bruce D »

Chuck that's very nice, I like the spikes. You captured the "paintbrush" striations in the nebulosity nicely
Bruce D
Chuck
Posts: 285
Joined: Tue Mar 31, 2015 1:14 pm

Re: Pleiades Wide Field

Unread post by Chuck »

Thanks Bruce. If I tried to be even less aggressive with processing, to eliminate the hints of the wider nebulosity beyond the Pleiades, I'd lose more detail around the Pleiades itself. I guess I could crop the image to compensate but I wanted the whole FOV in the image. As for the spikes, I did like them with my previous images but the main stars in the Pleiades are so bright that they are a little to distracting. Will see how the step down rings perform at some point.
Chuck M.

Meade 8" LX200 Classic OTA
iOptron CEM40EC and MiniPier on Meade classic field tripod
Canon EF 200mm f/2.8L II
Canon 7D Mark II
ZWO 60mm f/4.6 GS with ASI120MM-S camera
Starizona SCT Corrector II and Virtual View 2" Rotating Visual Back
Pegasus Astro Pocket Powerbox
Chuck
Posts: 285
Joined: Tue Mar 31, 2015 1:14 pm

Re: Pleiades Wide Field

Unread post by Chuck »

Received the filter step down rings for my Canon 200mm f/2.8 prime telephoto lens last Friday. Though the night wasn't great for imaging, I was able to experiment using the rings to see how they would work for eliminating the large spikes around very bright stars as seen in my Pleiades image above.

In the following link, in which I cropped the images to concentrate on M45 itself, the rings show to work nicely. I realize it's an apples to oranges comparison due to the integration time differences, but the purpose of the experiment was successful. I had mistakenly chosen the 30mm ring size, based on the native 200mm FL, for an aperture of around F6.6 where with the 1.4x extender, the aperture was really about F9.

Image


As I actually like the spikes in cases where star magnitudes are greater or equal to 4, I won't need the step down rings in most images. I'd like to redo the Pleiades again at some point but will probably need about 20 hours or more to get the proper detail in nebulosity in the wide FOV.
Chuck M.

Meade 8" LX200 Classic OTA
iOptron CEM40EC and MiniPier on Meade classic field tripod
Canon EF 200mm f/2.8L II
Canon 7D Mark II
ZWO 60mm f/4.6 GS with ASI120MM-S camera
Starizona SCT Corrector II and Virtual View 2" Rotating Visual Back
Pegasus Astro Pocket Powerbox
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bluemax
10+ Years Member
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Joined: Thu Aug 13, 2009 5:00 pm

Re: Pleiades Wide Field

Unread post by bluemax »

Chuck, can you brief me on the nature and relationship of step down rings and wide open iris? Why did you get spikes without step down and why step down eliminates them. Thanks.
Frank N

Stellarvue 80mm APO, Skyguider Pro, Celestron AVX

"I'm a seeker too. But my dreams aren't like yours. I can't help thinking that somewhere in the universe there has to be something better than man. Has to be"

Taylor in "Planet of the Apes" 1968
Chuck
Posts: 285
Joined: Tue Mar 31, 2015 1:14 pm

Re: Pleiades Wide Field

Unread post by Chuck »

Hi Frank, check the following link that I used to decide on trying the step down rings. It also describes the principle behind it.

https://www.dpreview.com/forums/thread/4120103

Hope that helps answer your question.
Chuck M.

Meade 8" LX200 Classic OTA
iOptron CEM40EC and MiniPier on Meade classic field tripod
Canon EF 200mm f/2.8L II
Canon 7D Mark II
ZWO 60mm f/4.6 GS with ASI120MM-S camera
Starizona SCT Corrector II and Virtual View 2" Rotating Visual Back
Pegasus Astro Pocket Powerbox
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