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Two Crescents - 01 Dec

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brianb
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« on: December 03, 2010, 08:52:01 am »

Venus and the Moon captured in morning twilight on December 1st.


0750 UT.  William Optics FLT 110, W29 (deep red) filter, 2.5x Powermate, DMK21

Diameter 42.2". Phase 23.8%. Altitude 15.39 deg.


0720 - 0732 UT. William Optics FLT 110, W29 (deep red) filer, 2x Powermate, DMK41; 7 frame mosaic, 24% resize. A full size version can be viewed here (select "high res image" from the zoom menu).

Diameter 32' 39.6". Colongitude 210.5 deg. Age 25.07 days. Illumination 23.7%. Libration in latitude +07 deg 25 min; libration in longitude +01 deg 52 min. Altitude 20.75 deg.

Note the very similar phases! However the size is very different...

Here's a crop of the Aristarchus area from the full size image; allowing for the difference in pixel pitch between the DMK21 & DMK41 cameras (5.6 microns and 4.65 microns respectively) this is almost exactly the same image scale as the Venus image at the top of this post.



Transparency good. Seeing poor to bad with substantial boiling. Temperature 0C; wind E force 3; baro 1020 mb, steady.
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rjgjr
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« Reply #1 on: December 03, 2010, 04:07:11 pm »

Excellent images as usual Brian, beautiful mosaic of the Moon. Love the long shadows on the crop.
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jjb
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« Reply #2 on: December 03, 2010, 10:22:36 pm »

Good images Brian nice detail.
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markt
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« Reply #3 on: December 04, 2010, 10:03:02 am »

Brilliant images as usual Brian!

What is the difference in image scale between the 21 & 41 not allowing for the pixel pitch of the 2 cameras?  Curious about this...
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brianb
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« Reply #4 on: December 04, 2010, 12:53:15 pm »

Quote
What is the difference in image scale between the 21 & 41 not allowing for the pixel pitch of the 2 cameras?
The DMK21 has 5.6 um pixel pitch, the DMK41 has 4.65 um pixel pitch.

WO FLT 110 focal length is 770 mm.

With x2 Powermate, 1540 mm: DMK41 image scale is 0.617861 arc sec per pixel

With x2.5 Powermate, 1925 mm: DMK21 image scale is 0.595273 arc sec per pixel

Or if you prefer 2.5 / 2.0 is approximately equal to 5.6 / 4.65

The image scale with DMK41 & 2x Powermate is very nearly the same as the image scale with DMK21 and 2.5x Powermate.
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markt
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« Reply #5 on: December 05, 2010, 10:47:27 am »

Thanks for that Brian!  Smiley
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martinastro
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« Reply #6 on: December 05, 2010, 05:05:56 pm »

These are outstanding Brian!, the lunar detail is exceptional and the crescent phase of Venus is beautiful. Congrats on such a rewarding photo session.
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