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The Moon - 13 Dec


brianb
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Worse conditions than yesterday, the seeing was very unsteady.

Moon-101213-1803-1813-FLTX2-mosaic09-small.jpg

1803-1813 UT. WO FLT 110, 2x Powermate, W29 (deep red) filter, DMK41 camera. 9 frame mosaic, 25% resize - full size version is here (select "High Res Image" from the zoom menu).

Diameter 29.95'; altitude 36.2 deg; colongitude 2.7 deg; illumination 51.8%; libration in latitude -06 deg 03 min; libration in longitude -00 deg 53 min.

Transparency moderate to poor; seeing bad with continuous large amplitude slow boiling. Temperature +01C, wind SE force 1-2, baro 1031 mb, rising slowly.

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Conditions have been rubbish of late, but this is excellent. :)

Your setup is almost identical to mine, but for your DMK41 over my DMK21... What does the red filter help to do? Is it to reduce unwanted wavelengths?

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What does the red filter help to do? Is it to reduce unwanted wavelengths?

Partly - it reduces atmospheric dispersion at lower altitudes - but mostly the seeing is steadier in longer wavelengths. Some people even use an IR pass filter, e.g. the Astronomik Planet Pro 742. The W29 is less extreme than this but allows more light through ... six of one and half a dozen of the other, in my experience.

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Hmm... I have a set of Celestron colour filters, and the red one says "No. 25" on the side - would this be of any benefit? It does appear to be quite a deep red. I'll no doubt try it anyway, but the weather seems to be turning cloudy again so I may not get the chance for a while.

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the red one says "No. 25" on the side - would this be of any benefit?

Wratten 25 is a mid red - 23A is light red. It's certainly worth trying but I think a Wratten #29 or Planet Pro 742 would work better, especially with larger apertures and especially when the seeing is on the poor side.

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Thanks, but my Dec 14th effort is much better (so was the seeing).

Sequence broken on Dec 15th due to solid cloud & with blustery snow showers on a freezing northerly gale forecast for tonight I can't see much chance of observing.

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