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Old 14-10-2020, 06:40 PM
tornado33
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NGC 55 in great seeing

Last night I noted the guide star was very small and tight, the best seeing Ive seen in some time, from my backyard in Newcastle. I was doing NGC 55, manually guiding my 1986 vintage 10 inch Newtonian.

Image is 6 x 15 minutes ISO 400. No filters.

Some of the bright stars aren't 100% round, I think its the full thickness mirror still a bit warm as the night air cools down, setting up a bit of an air current. Its a Pyrex Sutching mirror so no question of its quality

An off axis guider that "looks" from behind a coma corrector is just so nice. Round, not comatic guide stars, and the plastic worm wheel surprisingly well tracking, with its regular and easily correctable periodic error allowing me to keep the guide star sitting nicely on the virtual reticle.

Im investigating using a 2x converter to double the magnification and focal length, for those smaller objects where there is so much wasted space in the full frame camera view.

The EOS Ra is just great to focus, with 30x live view. Helped by the fact I disassembled the focuser, degreased it and coated the contacting surfaces with Teflon based gear oil, now it feels so smooth to focus and with absolutely no play at all.

The view shown is a full resolution crop, and a larger view is here https://www.astrobin.com/611z1k/0/
calibrated and processed with freeware IRIS and finished in Photoshop.
Scott
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Old 14-10-2020, 09:39 PM
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Woohoo it's clear

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Yes, despite the slightly elongated stars, the seeing does look to have been quite good ...great when that guide star fits in a single pixel of the guide camera...(err?..or eyeball )

Mike
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Old 15-10-2020, 07:15 AM
tornado33
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It seems really good seeing is quite rare in the Newcastle area. Many years ago when my scope was new I had it at a mates at Raymond Terrace. Just before dawn I saw my best visual look at Saturn ever. The Sutching mirror showed even tiny Enckes Division as a sharp thin line and dusky spokes easily visible on the rings. Never seen Saturn so good since.
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Old 15-10-2020, 09:53 AM
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multiweb (Marc)
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Very cool shot. Love the colors and details.
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Old 15-10-2020, 10:11 AM
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Woohoo it's clear

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Quote:
Originally Posted by tornado33 View Post
It seems really good seeing is quite rare in the Newcastle area. Many years ago when my scope was new I had it at a mates at Raymond Terrace. Just before dawn I saw my best visual look at Saturn ever. The Sutching mirror showed even tiny Enckes Division as a sharp thin line and dusky spokes easily visible on the rings. Never seen Saturn so good since.
Yeah, during our 5 year move to Newie 2007 - 2012, I imaged from Thornton, Kurri Kurri and New Lambton and all were noticeably worse than here in and around Canberra I had the then new AG12, set up in my mums backyard in New Lampton for over a year and never got good seeing The first night back and set up just outside Canberra on our return in late 2012, it was a revelation ...I had actually started to doubt the quality of the optics in my AG12 surely the seeing couldnt be soft every night...surely??..but yep, the seeing in the Newie area is, generally, just crap, certainly compared to the Canberra region anyway, that is for sure! Ok for wide field low resolution imaging, ie imaging at 3.5"/pix or higher should be fine but at 0.84"/pix....just a waste of image scale
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Old 15-10-2020, 07:54 PM
tornado33
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It must be the wind funneling down the hunter valley or maybe proximity to the ocean with land and maritime air mixing over the valley which is nasty for seeing, or maybe the jetstream spends a lot of time over the area
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Old 15-10-2020, 08:01 PM
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I read somewhere that the seeing is getting worse globally because the atmosphere is getting warmer and the difference of temperature between ground level and the stratosphere is increasing convection and makes the whole layers more turbulent. There's less stability between the boundaries. But like the air masses between the poles and mid latitudes. There's no clear limit anymore and incursions of very cold air down into warm aire and vice versa. That's how they got this 35c day and blizzards at -9c in a 24h period in the US in the fall. Very quick exchanges.
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