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You gotta be kidding me......

Tim

By Tim
in The Astro Lounge

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Tim

Tim

Posted
Posted

OK, what's the big joke?

Come on, somebody knows.

There has not been a cloud in the sky today, and the visibility is so good you could have read the ring numbers on racing pigeons 20 miles away.

So for the first time since 3rd Jan, I unpack all the gear, set it all up, re-do everything etc after the holiday. Psychobilly sent me a new bahtinov mask to try, so I slew round to venus, the only thing visible in the twilight, and pop the mask on.

When I see that the mask works a treat, just like the others, I thinks to meself "I'll take a pic to show Billy".

In the space of literally 3 yards walking, I look at the screen and wonder where the picture went. No sign of Venus or anything. Go back outside......you got it, wall to wall cloud.

Clear sky to thick cloud in 20 seconds. Unbelievable, unbelievable. This is getting past a joke.

:crybaby: :crybaby: :crybaby: :crybaby: :crybaby: :crybaby: :crybaby: :crybaby: :crybaby: :crybaby: :)

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Psychobilly

Psychobilly

Posted
Posted

Its so frustrating .. it was clear here all day ... so I spent a few hours on a new project in the workshop ready to try it out tonight... and you guessed it... blooming clouds not wall to wall but cant be arsed to fiddle with the new setup whilst fighting the clouds...

Might get soem widefield in but not holding out much hope for that either :)

Glad the GSO mask works though TJ...

Billy...

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John

John

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I was going to put my 12" dob out to cool about 30 mins ago as it was clear - I can now hear the rattle of torrential hail so I'm glad I didn't !

You can see how people with larger scopes can wait weeks before getting a proper 1st light !.

John

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James

James

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I was going to put my 12" dob out to cool about 30 mins ago as it was clear - I can now hear the rattle of torrential hail so I'm glad I didn't !

It's nice and clear just down the road in Taunton John... Of course if I put any kit out it'll cloud over here too...

James

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John

John

Posted
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I was going to put my 12" dob out to cool about 30 mins ago as it was clear - I can now hear the rattle of torrential hail so I'm glad I didn't !

It's nice and clear just down the road in Taunton John... Of course if I put any kit out it'll cloud over here too...

James

Clear patches here now but it would be a waste of time trying to get the 12" out and cooled. I might grab the Vixen ED102 and try and have a peek at Orion if the rain / hail holds off.

John

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Tim

Tim

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It just goes to show that it pays to complain. I was all but ready to hit the button to park the scope, when it seemed to clear a bit.

The visibility wasn't great, and there has been patchy clouds passing over, but I have managed to complete three goals tonight, and also bagged 3 3/4 hours of M81/M82 plus flats, so I've cheered up a bit :)

GSO 8" mask test. We had some concerns with the mask due to a bit of thermal warping, but these proved to be unfounded fears. I checked focus with the mask, then checked that against the crosshairs focus, then checked again against the fine focus method in Nebulosity. The Bahtinov mask got the focus to exactly the point with the sharpest focus indicated by the figures, which is outstanding. As far as focussing goes, I see the Bahtinovs as a "fire and forget" missile, fast, straight to the point, and once done, you can get on with whats important. So again, it's a big BIG thank you to Peter (Psychobilly) for pushing production of these through, I hope to get one for all my OTA's tha I use for imaging. One of the best tools to be had, no question.

TS 9mm OAG test. I have really struggle to get the spacing right with this little off axis guider. The main problem was getting the chip in my guidecam (Meade DSI Pro) to be the same distance from the coma corrector as the main imaging camera, 55mm, as that distance is critical. I think other cameras like the qhy5 might nothave a problem getting the chip close enough, would like to see one, but the DSI is an unusual beast in the way it attaches to fittings. With a little help from a hacksaw, and a grinding wheel, I was able to adjust a 1.25" adapter to a narrower size, an eventually got the spacing the same. Just needed to test the theory, and tonight I had the chance to do just that. As soon as the PHD showed the meade's image, it was very close to focus, a slight adjustment and it was spot on. GREAT!! Spent quite a bit of time on that! I will now complete a full review of the TS OAG when I get a minute, and post a pic of the results.

Third, my boy has had a Celestron SLT 60 thingy on an alt az mount with goto that we bought new off fleabay for less than a hundred quid. Its ok, but was a bit limiting. Tonight I found that by removing some of the housing on the clamp, I could attach my now redundant guide scope (WO72mm) to the mount, and that the mount could cope ok with it. Next step was to attach my also redundant 350D and hand over the remote control. Jake was well away, and we can look forward to his first images anytime soon I think.

All in all not a bad finish to the day in the end. Shame its now really thick wall to wall again, but at least the kit is back out where it belongs, and should be very quick to get going next time.

TJ

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dark knight

dark knight

Posted
Posted

I know exactly what you mean, I was walking the dog about 6.00pm as dusk arrived, Venus was clear as a bell, as was most of the sky. Raced the dog round the field (he's a lurcher so this was no mean feat) and got home, lovely clear sky. Sorted the power to the mount, sky still clear, went in to get camera, and yep you guessed it, the clouds rolled in. I spent the next 2 hours attaching and detaching the mains power and in the end gave up. Managed one 5sec wide field photo of the Pleiades. Trouble is I now have to learn processing raw, as I've only ever done jpeg. I really can't get to grips with this side of processing. My setup is quickly turning into one of the most expensive door stops in the world.

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narrowbandpaul

narrowbandpaul

Posted
Posted

this is my explanation. it may or may not be correct.

weather systems coming in from the east or west (usually) have travelled over a large expanse of water (atlantic if west), and so contain a lot of moisture.

in winter the air is cool becuase the ground is cool because the sun is at such a low altitude it causes hardly any warming.

further more the ground has a lower specific heat than the air, so it warms and cools faster. In winter with hardly any warming, the ground is colder than the air immediately surrounding it. This creates an effect called a temperature inversion, whereby the temperature actually increases as you go higher, because you are further from the cold ground. Eventually this effect dissappers, but below this change-over height, the inversion layer froms a boundary, which keeps stuff locked below it.

Next issue is High Pressure.

In winter high pressure means clear skies and low winds. This means cold (clear winter days are always colder than cloudy ones). High pressure is high, because the air is subsiding (falling). Subsiding air is very stable. With these low temp, high moisture systems from the atlantic comes high humidity (ratio of water in air mass/total amount it could handle). When humidity =100% clouds form. Couple these clouds (due to high humidity) with a low wind, stable air mass, all being contained in that inversion layer, and its suddenly no surprise that fog forms (low alt clouds)

in summer the reverse is true...high pressure=good, becuase the ground is well warmed by the sun in a clear day)

i feel the best time to get a clear spell, is in between fronts. There is usually a wind accompanying the front, which causes mixing of the layers and breaks up fog.

so high pressure in winter (those gloriously clear sunny days with excellent seeing that whet your appetite) usually spell fog for the reasons mentioned above.

in spring the sun starts warming the ground, and the inversion layer dissappears.

thats my explanation. It may be wrong.

paul

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MartinB

MartinB

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You jammy devil TJ! Clear blue early evening sky, good forecast, out of the wind. Was engrossed in setting up when the wife came out and told me it was about to rain. It all came over in 5 mins. Got a gap at about 9.00 pm. All I could do was set up my ED120 on it's Super Polaris, whilst still spotting with rain, and have a quick observing session. Cloudy by 10.00.

No imaging for 5 weeks now.

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