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"Complete" description of seeing

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#26 WRAK

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Posted 09 November 2013 - 02:51 PM

Norme, I can offer an UCAC4 based map for NGC6811 in Cyg up to +13.5mag and I am preparing one for NGC7789 in Cas - if you are interested just give me the orientation you need.
Wilfried

#27 WRAK

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Posted 09 November 2013 - 03:39 PM

Last night I got what I asked for (some haze in the air) but the results I got were mixed. The sky was clearly brighter than the night before and SQM reading was ~16.8mag meaning one mag brighter but NEML was the same with ~3.2mag - no idea how this may be to explain.
Deneb showed despite the haze a halo of similar size ~60" radius, but the companion was somewhat harder if barely to resolve. Occultation of the primary (my ideas how to do this better proved to be a desaster so it was again leaving the field of view) had this time only minor effect - the halo remained and the companion was equal hard to see as before.
Seeing was not this bad with estimated Pickering ~6 as the diffraction pattern was to my surprise rather crisp and not at all fuzzy but jumping according the Pickering scale for ~6.

Then I started my session in Peg beginning with wide and easy STF2986 31.2" +6.61/8.88mag and limit aperture was 80mm against 26mm RoT proposed - so I assumed this result was the effect of bad transparency. Only later on I found the the companion is probably much fainter.
Next came the surprise with HU987 1.1" +9.2/9.7mag and proposed aperture 145mm. I did not expect much but got already a rod with x140 and a clear split with x200 if only for repeated fractions of seconds but distinctive. With a CO of 0.15 I got a more stable split, same with x200. Same with 0.2 CO. Crisp spurious disks - no sign of fuzzy cotton balls.
Later on results were similar may be with only an exception for very faint doubles - here it was not possible to get to a reasonable high magnification without loosing resolution.

Conclusion: Naked eye haze means in the lower atmospheric layer may not be this problem for resolving doubles. The cotton ball effects must have reasons in haze in the higher atmospheric layers not to be seen with naked eye but only with scopes.
Wilfried

#28 Asbytec

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Posted 09 November 2013 - 10:19 PM

Thanks, Wil, but I don't want to rely on asking each time. Need a good reference I can access at Wil (pun intended.) Actually, I found wikisky quite good. It gives magnitude for stars in overlaid images that can be glimpsed at the eyepeice. Haven't tried it for tight doubles, though.

http://www.wikisky.o...img_source=DSS2

Mulling over your next post...

#29 WRAK

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Posted 10 November 2013 - 04:21 AM

Have seen that in my Deneb map I have also +13.01/13.30/13.67/13.89mag stars included. Should do it too to some degree.
According to my TML check implementation for the RoT the TML for your 155/0.31 scope with NEML ~+4.5mag should be about +13.2mag but currently I assume there is still the factor extinction to consider - so with an average extinction value of 0.3 this should give a ~+12.9mag limit relevant for resolving wide >15" doubles with a companion this faint.
Wilfried

#30 Asbytec

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Posted 10 November 2013 - 05:06 AM

Yes, got it (Deneb map) and will check it tonight. Weather is holding but seeing might be terrible. More later.

Edit: The dimmest star I could see was the 13.01 mag star west of Deneb. The nimbus was extensive tonight, reaching out to the 12th mag star trailing Deneb. Seeing was horrendous at 4/10 Pickering. Blew my difficult observing list out of the water. Shame for such a clear night, but apparently the typhoon is still drawing a lot of moisture and stirring upper level winds.






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