PIER-05 Star Halos, transparency and max integration time

Brian

we are edging towards the wet season now in Spain so high cloud can be an issue and we have been working our socks off the last few weeks setting the roof temperature to try and avoid the high atmospherics as much as possible. 

I doubt 300s was to long as it’s a dark neb after all, perhaps attaching an image may help throw some light on what it could be

steve

Hi Steve,

Thanks for that.  I attach thefinal image, Made from the 90 "best" subs (out of over 150).  The star counts in each sub were quite variable, so I only too look those  33% of the medium  of better.  To me, this is symptomatic of haze.  But if I removed them, then how come the halos are still there, unless there was haze al the time, or my subs were too long.  

I really appreciate you guys fighting against the weather at this time, and I query is less about the weather (which I can do nothing about!) or my observing strategy (which I can). 

THanks

Brian

Thanks for the image

Pete said he will take a look today and get back to you, having said that the blue hot stars in this image always tend to be a little like this due to the surrounding nebulosity

Its also an object that may have benefited from requesting "moon down" in retrospect. Moon down, unfortunately does prolong capture times quite a bit however but for some objects it is needed

Steve

Hi Steve, Thanks for the advice on requesting Moon down.  I might do that in future, as well as limiting my exposure length.  I had a look at other images (Astrobin) of the same area, including those taken with a Tak180ED, and they don't show the same halo extent.  So I don't think it can be nebulosity in this case.  My own suspicision as a mixture of cloud, moon and too long sub-exposure length.  This is a difficult target (faint IFN with bright stars), so perhaps I should have been less ambitious to start with.  
CS Brian

Morning

Your points do have merit to be fair

As for  you point re sub lengths, an F/4 telescope on the whole is classed as a very fast optical system, the E-180 is one full F-Stop quicker at F/2.8, so that's the same amount of data in half the time of an already fast F/4 system, so yes bright stars will suffer from over exposure

HTH

Steve

Hello Brian,
I have checked the data and the halos you refer to were caused by high haze in this case. When ever I check data before sending unless there are excessive frames that have issues I would normally resubmit them. I will always include all data good or bad frames so they do need quality checking before stacking as other have their own ideas what falls under those categories. When ever you feel you are short of frames for what ever reason please just resubmit a new job with a note attached to say they are to replace bad frames etc.
Peter

Hi Peter,  Good to have that confirmed.  I will re-submit in 9months time or so.  Although circumpolar, I figured it is alway best to image things as they rise.  To be honest, its only the only data-set to date (out of half-a-dozen) I have reduced where the data has been anything short of very good.  As a former professional observatory direction, I know how challenging - and expensive - quality control of "service observing" is.    No complaints here.  
Regards
Brian