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Old 31-12-2016, 08:07 PM
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Atmos (Colin)
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Seeing: How bad is too bad?

This evening I have been in two minds as to whether to make the effort and head up to Heathcote for the moonless skies. The problem is... it is going to be horrible seeing!
No good for resolution but for RGB? How bad can the RGB be before it starts compromising overall quality and having to be scrapped?
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Old 31-12-2016, 08:19 PM
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lazjen (Chris)
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Might be worth going so you can get actual data to determine for yourself?
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Old 31-12-2016, 08:26 PM
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Atmos (Colin)
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If I could do it from my back guard I would, don't really want I make the 3 hour return trip to dark skies on NYE
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Old 31-12-2016, 09:13 PM
glend (Glen)
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Avoid the frustration, stay home.
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Old 01-01-2017, 05:05 PM
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multiweb (Marc)
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Quote:
Originally Posted by Atmos View Post
If I could do it from my back guard I would, don't really want I make the 3 hour return trip to dark skies on NYE
I don't know how far Heathcote is from your home but if the seeing is bad at home it is very likely it will be bad within a 100km radius. Timing is usually more critical for "local" good seeing rather than location. I've seen instances of very good seeing followed up by utter garbage seeing but very rarely good seeing in one location and bad seeing in another location within 100km or 200km away.

If you check CFN in the dark sky section the wind vectors predictions are actually very accurate. I haven't imaged in a long while but I've been keeping an eye up and the data displayed in the dark sky section is pretty much on the money. Don't bother with other sources if seeing is important to you as they all use GFS.
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Old 01-01-2017, 05:25 PM
glend (Glen)
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I have been finding that seeing improves after midnight, in summer, as the earth has radiated off the heat it has collected during the day. It can be rubbish at 9pm and great at 1am. But as always, local conditions......
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Old 02-01-2017, 05:05 PM
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I usually vote to do wide field (aka DSLR+lens) if the stars continue to twinkle above ~40 degrees altitude.
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Old 24-01-2017, 03:13 PM
pjphilli (Peter)
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Hi Marc
What is CFN and how do you use it?
Cheers Peter
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Old 24-01-2017, 03:28 PM
pjphilli (Peter)
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Hi Glen
Owing to my advanced age I am prone to have to get up at midnight or 1 am
or thereabouts and I often see a nice clear sky but I don't have the go to
get out and take advantage of it. With the sunset at about 8pm these days
good viewing has to wait until at least 9pm and as you say the sky is usually poor for the reasons you give and also a moist NE wind is often still blowing.
Also very late at night the light pollution at my place is noticeably reduced.
The last few months here have been particularly bad for astro imaging.
Cheer Peter
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Old 25-01-2017, 05:25 PM
wastro (Robert)
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Hi Marc
What is CFN and how do you use it?
Cheers Peter
CFN is Cloud Free Night (www.cloudfreenight.com). On the home page you can register for one month of (no obligation) Supporter access to all features. It is the best cloud forecast site for Australia!!!
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Old 26-01-2017, 06:24 AM
Robair (Robert)
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Gday Rob
Thanks for posting the CFN link, it looks like a great resource.
I did have a chuckle though at the testimonial of the photographer who used it to ensure that clouds were aplenty.
This got me thinking that perhaps an IIS forum sticky could be created that tracks when astronomers purchase new whizz bang equipment? They would simply log their general location and equipment purchased, this would then indicate the cloudiness of that location.
For example, I am in Toongabbie and I purchase a tak scope, serious mount and a dome observatory. This would forecast 10/10ths of constant cloud cover for at least a month from that date over western Sydney.
Or;
I purchase a new eyepiece, that would earn maybe a few days of cloud.
I think you know what I am getting at here....
Cheers
Rob B
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Old 26-01-2017, 05:37 PM
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philiphart (Phil Hart)
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Quote:
Originally Posted by Atmos View Post
This evening I have been in two minds as to whether to make the effort and head up to Heathcote for the moonless skies. The problem is... it is going to be horrible seeing!
No good for resolution but for RGB? How bad can the RGB be before it starts compromising overall quality and having to be scrapped?
Adding to an old thread as I am want to do.. but I'd suggest that Seeing forecasts are not skillful enough to ever choose to stay at home if weather and your availability are otherwise positive.

Based on your signature, if you're imaging at 650mm focal length I think you'll always be able to image successfully enough. If it was *really* that bad you could at least collect RGB and prioritise luminance when it's better.

Phil
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Old 26-01-2017, 06:13 PM
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Atmos (Colin)
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Adding to an old thread as I am want to do.. but I'd suggest that Seeing forecasts are not skillful enough to ever choose to stay at home if weather and your availability are otherwise positive.

Based on your signature, if you're imaging at 650mm focal length I think you'll always be able to image successfully enough. If it was *really* that bad you could at least collect RGB and prioritise luminance when it's better.

Phil
It is one of those times that if it is in the back yard it isn't too bad but making the trip out to a dark site, having to get up at 4am to pack up to start work at 6:30 am

At the moment I am imaging at 1.16"/pixel and on a good night I can get <2" FWHM so I can drizzle out a bit more sharpness. On a bad night I am getting 4" seeing or ~3.5 FWHM.

That was the purpose of this post, how bad can the RGB be before it just needs to be retaken?
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Old 27-01-2017, 09:07 AM
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philiphart (Phil Hart)
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It is one of those times that if it is in the back yard it isn't too bad but making the trip out to a dark site, having to get up at 4am to pack up to start work at 6:30 am

At the moment I am imaging at 1.16"/pixel and on a good night I can get <2" FWHM so I can drizzle out a bit more sharpness. On a bad night I am getting 4" seeing or ~3.5 FWHM.

That was the purpose of this post, how bad can the RGB be before it just needs to be retaken?
No debate that dark sky trips are hard if you need to back up to work!

I'm just not convinced that seeing forecasts are good enough to make decisions on. Clear dark nights are rare enough.. once those factors are in place I think seeing is a role of the dice.

Do you see much correlation between seeing forecasts and actual results at home?

Phil
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Old 27-01-2017, 09:11 AM
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Atmos (Colin)
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I use a combination of CFN, Skippy Sky and Meteogram, when they all have strong jet streams and forecast poor seeing, it generally isn't crash hot. I do completely agree that forecasting poor seeing isn't really there yet but when several indicators poiunt towards poor seeing, I tend to believe it
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Old 27-01-2017, 10:45 AM
pjphilli (Peter)
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Hi Robert

Just had a look at CFN which looks very promising.

Thanks Peter
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