NGC 7789 “Caroline’s Rose”

Moira’s wonderful talk last night on the constellations around Cassiopeia made me look back into my archive for images.  I have reworked this one today – a September 2014 capture of NGC 7789,  an open cluster in Cassiopeia known as “Caroline’s Rose”.  It was discovered in 1783 by Caroline Herschel and catalogued by her brother William.

Caroline's Rose 2016 version reduced20 frames of 45 seconds stacked, Nikon D90 through Altair Wave 115/805, ISO 3200.

Simon

Planets still in a line!

Not sure whether this was worth the effort, from a photographic point of view, but it was still a glorious naked-eye sight from the trig point on The Helm yesterday morning just before 7 o’clock.  Mercury is there too, either behind that CIC (“curiously immobile cloud”) below and to the left of Venus, or lost in the sunlight.  Binoculars might have tracked it down, but scanning the eastern horizon with binoculars at sunrise is a mug’s game.

This is about 16 shots with a fixed 50mm lens, stitched together using a wonderful programme called PTGui.

The Lovejoy Trio

Here’s a preview of my three photos of Comet Lovejoy taken from the church car park in Old Hutton on the evening of the 18th of January.  Come and see them on the big screen at the February meeting (Monday 2nd, 7pm at Kendal Museum, all welcome!) when I’ll share a few words on how they were taken and processed.

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Clear skies!

Simon

The importance of good skies

As mentioned at the last couple of meetings, I’ve been taking every opportunity to catch a photo of comet C/2012K1 (PANSTARRS) making its way across the night sky.  It has brightened to about Magnitude 8 at the moment, but as the nights get shorter around the summer solstice, it becomes harder to photograph a such diffuse object against a dark sky.

Here is my effort from last night (to be precise, early this morning), highlighting several issues that upset good astrophotography.  20 exposures of one minute each, stacked together with the 20 frames aligned on the comet – so the stars appear as short lines because the comet has moved a slight amount from one exposure to the next.

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What are the issues ?

1.  At this time of year, the Sun dips only 12º below the horizon at night.  Full astronomical darkness needs 18º below (which won’t happen again until the 3rd of August), so in astronomical terms the sky isn’t really dark.

2.  The comet is visually only about 60º away from the Moon, which is also above the horizon and more than half illuminated.  The moonlight lightens the background even more than the twilight, making it hard to distinguish the comet tail.

3.  Although the sky looks clear to the eye – and there are no clouds visible – there is a high level of humidity (about 90%).  The humidity catches the moonlight and creates the illusion of streaks across the sky as the telescope mount tracks the movement of the stars.

4.  The comet is now only 25º above the horizon, which means it is being photographed through much more of the Earth’s atmosphere.

Compare the result with an earlier photo, which was processed identically to the above.  This one was taken on the 26th of April in full darkness, with no Moon, 60% humidity and the comet at an elevation of 83º (almost vertically above the observer).

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Even though the comet is a couple of magnitudes fainter, it is much more distinct in the photo.  Dark, clear skies are the key.

Simon

 

Now that was a challenge…

When I wrote that the Night Sky in March would include a “big sky” view of Jupiter’s highest point, I thought at the time that it would be a fun challenge.

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The cloudy forecast for the 13th meant that I had to take up the challenge a couple of days early, so Jupiter wasn’t quite as high and the Moon was a bit more central than I would have liked. Anyway, here’s how the evening turned out.