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Acceptable wind speed for imaging


Guest sharpie78
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Guest sharpie78

Just wondering at what wind speed other people just don't bother tyring to image DSO's ?


 


I've got 12mph WNW winds with gusts up to 27mph. So far I've only had to scrub 4 out of 20 images as the gusts aren't too frequent but the forecast says the wind is going to pick up later on. When should I just knock it on the head ?


 


Cheers


Jack


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I'm no imager, but would have thought it depends on various factors, such as stability of the tripod/pier, how big a sail the scope is, and how sheltered it is. On DSO's it should be slightly less of a problem than with a 4x barlow on Jupiter.


 


I suppose you will just have to think whether you are prepared to waste an even higher percentage of your subs than the 20% so far. Maybe some sort of makeshift wind break or re-siting the scope to a more sheltered position would help reduce the problem. Don't wait till the rig has blown over :o .


Edited by Tweedledee
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Guest Tweedledum

Pete has it, also depends on the turning momentum with all the kit on the mount. You will be surprised at the wind pressure on the ota. Caught in one storm , did not need any sail, just the mast and still needed a drogue...

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Guest sharpie78

Thanks for your responses. :)


I've got a quattro 8s (newt) + ST80 guidescope on an HEQ5 which is on a concrete pier in my obsy. I've got it all nicely balanced etc and  I haven't had any probs at all with startrails until last night. It's obviously pretty well sheltered thanks to the obsy. I think the main problem last night was that I was imaging M31 around 7pm so the top of the scope was poking out of the roof as M31 was pretty high up near the zenith. I think the gusting winds were catching the top of my scope and my dew shield so I took that off and the startrails did reduce quite dramatically. I only lost 1 from 10 subs after that and then it clouded over. :(


I think I might make some kind of windbreak which I can just pop out of the roof a foot or two on the side of the wind direction on any particular night. The scope only pokes out of the roof by 10 inches or so (of that 10 inches, most of it is dewshield). Fingers crossed the windbreak idea will help out. Any other suggestions greatly appreciated :)


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Guest Tweedledum

If the top of the scope is out of your lovewly warm obsy :) , then it is providing maximum torque to the mount. Try it without the dewsield on as with the breeze there should not be much dew if any collected. Your dewstrips should cope.


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I did consider setting up with the smaller scope but that meant being out of the shelter of the obs, so I did not bother.


 


For me it depends on the gusts and the size of the scope


 


a steady wind I can cope with


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Guest sharpie78

I've never bothered setting up before when the gusts have been up to 27mph like last night but seeing as it was already setup in my new obsy I thought I'd just give it a go. When I've bothered setting up and it's been windy in the past, it's been a steady wind and like Steve....I've coped with it


 


As absterreo mentioned....and I found out.....without the dewshield on the startrails were dramatically reduced.


 


At present the dewshield is my only form of dew prevention though.


 


I'm installing a fan at the primary end of the ota this weekend and have ordered the parts to make a dew strip for my guidescope but I haven't sorted anything for the secondary (other than the dewshield I already have).


 


I think for the time being I'll just image when the wind isn't so much of an issue


or


try the windbreak idea


or


not have the dewshield on and have a possibly shorter session before dew becomes a problem on the secondary mirror.


 


EMS advice helps out once again :)

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the last time I was at the Galloway star party I used the wind break and had the mount as low as I could mange with tit


 


Myself and Mike have used them up at Belper to good effect as well


 


I managed this the other year http://www.eastmidlandsstargazers.org.uk/topic/241-the-mad-mans-horsehead-in-ha/?hl=mans


 


 


even I would not have tried with the C11 on Friday though, which is what is on the mount at the moment the baby 60mm Tak would have been another story

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