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Gregk
Pooh-Bah
Reged: 11/19/06
Posts: 1454
Loc: Gilbert Arizona
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Hello
I recently got a pristine 200mm F4 Nikon manual Lens for
adapting to my Canon XT. Last night shooting the Heart and Soul nebula I noticed Halos around bright stars and medium bright stars at F5.6..I had to stop it to F8 to get rid of them. I proceeded to shoot 5 minute subs at ISO 1600 to make up for the stop loss...This resulted in way too much noise to subtract out..unless I get 20 darks at 5 minutes
temps were around 72deg F
I'm used to shooting at ISO 800 
Would this halo scenario improve in non light polluted
skies ?
The lens is extremely flat It's much better than my WO 66mm
I see no coma in the edges in this lens but yet it suffers
from this halo issue
Thanks for any commentary
Greg
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www.azspaceblog.com/
Orion Star Shoot Pro OSC
Oiron Star Shoot II OSC
Celestron Cg-5 ASGT mount
Celestron ED80 Piggy back with william Optics 66mm APO
Celestron 6" SCT Piggy Back with william Optics 66mm APO
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Jerry Lodriguss
Vendor
Reged: 07/19/08
Posts: 576
Loc: Voorhees, NJ
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Hi Greg,
You are probably seeing chromatic aberration in the Nikon lens.
Shooting under a darker sky will not make it any better since it is in the lens.
You could try using a minus-violet filter.
Jerry
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A Beginner's Guide to DSLR Astrophotography
http://www.astropix.com
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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Greg - could you post a sample of one of the shots with halo?
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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Gregk
Pooh-Bah
Reged: 11/19/06
Posts: 1454
Loc: Gilbert Arizona
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Thanks for the replies Let me post this image It appears to be CA So letting more light in at 5.6 amplifies the lack of color combining....
I have Carbonis tools I could use them or add a minus violet filter along with the Broadband LP Filter
--------------------
www.azspaceblog.com/
Orion Star Shoot Pro OSC
Oiron Star Shoot II OSC
Celestron Cg-5 ASGT mount
Celestron ED80 Piggy back with william Optics 66mm APO
Celestron 6" SCT Piggy Back with william Optics 66mm APO
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Valerio
member
Reged: 05/02/06
Posts: 70
Loc: Italy - Milan
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Hi,
I've the same problem with an other old Nikkor manual focus lens: 105mm f/2.5
http://astrophoto.t35.com/m42/index.html#Orione_NikonD300_Nikkor105mm
This is a 15x600s with an unmodded Nikon D300, Astronomik UHC-E filter and the lens stopped at f/4
I've also astigmatc problems on the corners!
Valerio
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Jerry Lodriguss
Vendor
Reged: 07/19/08
Posts: 576
Loc: Voorhees, NJ
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A broadband light pollution filter may help by itself, depending on the type of bandpass it has. You might not need a minus violet if you use a good broadband filter.
Jerry
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A Beginner's Guide to DSLR Astrophotography
http://www.astropix.com
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ccs_hello
Post Laureate
Reged: 07/03/04
Posts: 3300
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Nikon ED * lens ($$$) helps too.
Clear Skies!
ccs_hello
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