My new self build - plastic Correx Observatory

[powerlord]

well, I've got 2 permanent mounts in there, and they'll be pointing at different targets each night - so a hatch doesn't really work.

tomorrow is looking good for first light. 🤞

[ollypenrice]

50 minutes ago, powerlord said:

yeh i reckon removing or fitting roof is not a good idea if windy. take tonight for example, against forecast I can see stars. but far too windy. it's all a compromise but its not very windy here usually tbh - current chain-storms aside.

tbh its not so much putting on or removing as what to do with it when off if windy - it's too big to put in conservatory, etc. So it has to be calm enough it can be left in garden.

I need to sort out a sort of 'weight bag' I can put on top if the centre when upside down on grass - something not too concentrated.. just in case it gets windier during night like you say. maybe just a bit of 2 foot x 2 foot or so of 1/2in plywood actually - that'd work.

other option is I work out a way it can sit on grass right way up. then wind is fine provided it doesn't get underneath it - but that bit I can't think of a great foolproof mechanism for at present.

 

 

This is not my field and I'll gladly stand corrected but in my present understanding...

...wind does not cause lift by getting under the lower surface.  Some recent research has changed the textbook explanation https://www.cam.ac.uk/research/news/how-wings-really-work#:~:text=“A wing lifts when the,along the lower%2C flat surface. but it's commonplace for roofs to be 'torn off' closed buildings which have a zero windspeed on their underside. The stationary air's pressure on the underside is capable of blowing off the roof when the wind causes the pressure to drop on the upper side. This is counter-intuitive because we naturally suppose that the lifting energy is somehow contained in the highly energetic wind when it is really coming from the air pressure of the stationary air below.

Olly

[saac]

29 minutes ago, ollypenrice said:

This is not my field and I'll gladly stand corrected but in my present understanding...

...wind does not cause lift by getting under the lower surface.  Some recent research has changed the textbook explanation https://www.cam.ac.uk/research/news/how-wings-really-work#:~:text=“A wing lifts when the,along the lower%2C flat surface. but it's commonplace for roofs to be 'torn off' closed buildings which have a zero windspeed on their underside. The stationary air's pressure on the underside is capable of blowing off the roof when the wind causes the pressure to drop on the upper side. This is counter-intuitive because we naturally suppose that the lifting energy is somehow contained in the highly energetic wind when it is really coming from the air pressure of the stationary air below.

Olly

That is effectively the classical description of lift  - the wing is "sucked up" due to a differential pressure.  Air moves faster over the upper surface increasing in Kinetic Energy with a corresponding drop in pressure compared to the underside.   I've often thought that we fool ourselves  by thinking all of our "roof locking down" measures would do anything if the wind blows in an unfavourable manner across the roof.  You only need a small pressure differential acting over a large enough area and before you know it you are lifting a 747 into the air !  I think I also fool myself in thinking that the irregular profile of my octagonal roof helps to disrupt the airflow over it to prevent too much lift.  Touch wood, so far so good  

 

For some mild amusement and demonstration of the Bernoulli principle tear a strip of paper (3/4 inch wide)  and place it on your lower lip. Blow gently over the topside of the paper and it will rise upward due to the lift. 

 

Jim 

Edited February 21, 2022 by saac

[powerlord]

no your quite right olly. (I'm a pilot).

And it's the reason the roof is so secure when on the obsy - since the negative pressure on the top side during wind tries to 'suck' the roof off. But because I made it very airtight, it cannot - since any attempt for the roof to lift causes the pressure to drop inside too, and hence balance out. this is achieved by the long cross over between the roof walls and the ground walls- it's like a big bicycle pump or one of those old ballon inflation pumps if you remember them ?

But that is the same reason why air 'getting under' the roof on the grass will cause it to be blown away. Basically, the same thing happens, but since the roof this time is just lying on the grass, there is nothing stopping it being lifted into the low pressure- and as soon as it is by a few mm, the pressure inside the roof is unconstrained/not sealed. and then - well you've got a wing basically - and up it goes.

 

[powerlord]

Oh also , I should add that I watched this happen before I added the roof strengthening/doming. As the wind caused the pressure on the roof to drop, the roof 'popped up' into a dome, as the pressure inside was then enough to sort of 'blow it up'. Buy add the strengthening and pre-doming, I take away a bit of the kentic energy.

If however, say the door was open - all bets are off.

[saac]

6 minutes ago, powerlord said:

Oh also , I should add that I watched this happen before I added the roof strengthening/doming. As the wind caused the pressure on the roof to drop, the roof 'popped up' into a dome, as the pressure inside was then enough to sort of 'blow it up'. Buy add the strengthening and pre-doming, I take away a bit of the kentic energy.

If however, say the door was open - all bets are off.

Add a few vortex generators to the roof powerlord and you'll sleep easy on the most stormy of nights   

Jim 

[powerlord]

well forcast is awesome for tonight. still 25-30mph winds. but going for it.

I might see if I can squeeze the roof into the conservatory, but if not will just have to put some chairs on it.

fingers crossed.

don't trust asiair Plans - I've had quite a few times where they have just stopped for no reason, so I've got 2 targets per mount planned for tonight - (hours due to visibility from my location)

mount 1:

SY135+asi1600 widefield:

5 hours fox fur/cone and rosette

3 hours heart and soul

mount 2:

500mm 80ED, asi533 and new IR/UV filter I got from @AstroNebulee

3 hours on M33

7 hours on Bodes

🤞🤞🤞🤞🤞🤞🤞🤞🤞

[Ouroboros]

Blimey! I’m lucky if I got through that much in a whole season. 😀  Keep that up over a few nights and you won’t have time to process it all. 

[powerlord]

All setup and ready to go.

 

[Richard_]

Been following this awesome thread! Good luck on your first light and hope everything works well for you pal. 

[Mick J]

'awesome thread'  very impressed, especially in this weather.  Any thoughts on sunshine if we ever see any ?

Edited February 22, 2022 by Mick J

[AstroNebulee]

4 hours ago, powerlord said:

well forcast is awesome for tonight. still 25-30mph winds. but going for it.

I might see if I can squeeze the roof into the conservatory, but if not will just have to put some chairs on it.

fingers crossed.

don't trust asiair Plans - I've had quite a few times where they have just stopped for no reason, so I've got 2 targets per mount planned for tonight - (hours due to visibility from my location)

mount 1:

SY135+asi1600 widefield:

5 hours fox fur/cone and rosette

3 hours heart and soul

mount 2:

500mm 80ED, asi533 and new IR/UV filter I got from @AstroNebulee

3 hours on M33

7 hours on Bodes

🤞🤞🤞🤞🤞🤞🤞🤞🤞

Sounds fantastic Stu. You've got some great targets planned there, good luck, can't wait for your images and reports from the obsy first light👍

[powerlord]

thanks all;. fingers crossed.

@Mick J I think will have to wait and see. main defence of it getting too hot it the fan system. this should change the air out every few minutes stopping it getting too hot. If that isn't enough it might need some sort of reflective layer on the roof (mylar maybe). or, worse case, I just don't leave the OTAs out there when it's roasting hot.

It's still pretty windy just now, and some rain forecast for 3ish. So I think I'll leave taking roof off till 5.30-6. And if I can Im gonna try to squeeze it into conservatory with the wind tonight. Other than that, hoping it goes ok. I've only shot HSO with the 135 once a while back as I had to jerry rig an adapter to get it all together and focus. Since then I've got the proper zwo adapter so should be better  - and I was inspired by @geeklee post of the rosette widefield to try something similar.

And though I've shot M33 a few times now, and once with the 80ED, I shot it with a cheap svbony IR/UV blocker which I'm not sure is very effective. So looking forward to see if @AstroNebulees zwo one is better. also shooting at native 500mm rather than  through the 0.8FF. Just for kicks.

I've had quite a few nights imaging ruined though by the asiair plan just 'sticking' - sometimes for no reason - saying its running but doing nowt, sometimes failing to stop plate solving after a meridian flip, and a few times, losing guiding for some reason and getting off target, and then since it only ever does a goto once at the start of each plan it continues to take merrily subs of something else entirely for several hours (that one I've moaned to zwo about and asked for a 'goto after x subs' type option). Long and short of it is, assuming forecast is accurate(!), i'm gonna be up most of night checking my ipad and my samsung tablet all the time to make sure first light is a success!

Now, down to Aldi to see if they have any virgin chickens left in stock - I feel a sacrifice is required. 🐔🔪🩸🙏

 

[AstroNebulee]

Good luck tonight, hope all goes well Stu and the filter performs better than the svbony one, was nice on my set up when used 👍, hoping for some clear skies  myself tonight if the reports are correct, to test out my alterations 

Edited February 22, 2022 by AstroNebulee

[powerlord]

Well, blue sky, roof off. I did fit in conservatory just in case gets windier.

 

[Ouroboros]

Your neighbours have got some massive scopes! 😉

[powerlord]

Well, first light went like clockwork. Great conditions last night. I PAed both mounts, checked the guider focuses and bogged off back inside.

I setup my gopro for some timelapse so we'll see what that looks like later too.

As I say - don't trust asiair plans, so I managed the targets myself on the asiairs - lost a bit of time on mount 2 as that asiair had never had the filter wheel on it before - so had to faff about setting that up - and I think in the end got the names of filters wrong.. so my H is S, and my S is H, but won't matter really.

It seemed pretty calm during the night with decent seeing - the 135mm was getting FWHM less than 2.

I got all 4 targets shot for as long as they were visible. My framing of my widefield wasn't as great as I'd want, but as I started with Oiii, it was an hour in before I noticed and didn't want to lose that data my reframing.

Mount 2 (the dodgy EQ6 I got and fitted rowan belt kit to), so knowhere near as good as my new EQ6Rpro - but it was getting 0.7rms or so on the first target, and about 1.2rms on the second, which is good enough for the widefield.

Mount 1, the new EQ6-R was ticking along at 0.3-0.6rms most of the  night with the 500mm 80ED on it (1rms by last target) Looking at the subs from this, there is some stretching of stars at a few corners, but with the targets in the middle of frame I reckon I will still get more detail than if I'd shot with the 0.8 reducer/FF.

Out this morning, shot the flats, popped roof back on, went inside and downloaded all the subs over the network then told alexa to 'turn the stars off', turning the power off and alarms on.

So first light complete, and around 20 hours of imaging in a single night !! 🤩

It could be I've never noticed this before, but I was amazed anyway - when I noticed that 1 second guiding exposures were getting me clear detailed images of M42. I should have screenshotted one, but didn't think. I did screenshot bodes later - +6.7 target, and still clearly visible in a 1 second sub - thought that was quite amazing (but probably just never noticed before as it's only now I've sorted the guidescopes to be aligned with main OTA). It was 6am by this point and it was getting lighter as I faffed around trying to remember how to get a screenshot on ios, so by the time I did it was far less visible - but still.

Edited February 23, 2022 by powerlord

[Ouroboros]

Excellent for a first night. 

[Stuart1971]

1 hour ago, powerlord said:

Well, first light went like clockwork. Great conditions last night. I PAed both mounts, checked the guider focuses and bogged off back inside.

I setup my gopro for some timelapse so we'll see what that looks like later too.

As I say - don't trust asiair plans, so I managed the targets myself on the asiairs - lost a bit of time on mount 2 as that asiair had never had the filter wheel on it before - so had to faff about setting that up - and I think in the end got the names of filters wrong.. so my H is S, and my S is H, but won't matter really.

It seemed pretty calm during the night with decent seeing - the 135mm was getting FWHM less than 2.

I got all 4 targets shot for as long as they were visible. My framing of my widefield wasn't as great as I'd want, but as I started with Oiii, it was an hour in before I noticed and didn't want to lose that data my reframing.

Mount 2 (the dodgy EQ6 I got and fitted rowan belt kit to), so knowhere near as good as my new EQ6Rpro - but it was getting 0.7rms or so on the first target, and about 1.2rms on the second, which is good enough for the widefield.

Mount 1, the new EQ6-R was ticking along at 0.3-0.6rms most of the  night with the 500mm 80ED on it (1rms by last target) Looking at the subs from this, there is some stretching of stars at a few corners, but with the targets in the middle of frame I reckon I will still get more detail than if I'd shot with the 0.8 reducer/FF.

Out this morning, shot the flats, popped roof back on, went inside and downloaded all the subs over the network then told alexa to 'turn the stars off', turning the power off and alarms on.

So first light complete, and around 20 hours of imaging in a single night !! 🤩

It could be I've never noticed this before, but I was amazed anyway - when I noticed that 1 second guiding exposures were getting me clear detailed images of M42. I should have screenshotted one, but didn't think. I did screenshot bodes later - +6.7 target, and still clearly visible in a 1 second sub - thought that was quite amazing (but probably just never noticed before as it's only now I've sorted the guidescopes to be aligned with main OTA). It was 6am by this point and it was getting lighter as I faffed around trying to remember how to get a screenshot on ios, so by the time I did it was far less visible - but still.

Sounds like a very productive first light, and I remember the feeling, it’s very satisfying when all goes well…I too noticed last night that I was getting good data of my target on my autofocus subs which are 6 seconds long, and this was down to using the Optolong L-Xtreme filter, why is new to me and first time I used…just wow…and I would highly recommend to anyone with Medium to bad LP, it really does make such a difference to the amount of detail captured…

Anyway good luck for future sessions…👍🏼

[powerlord]

 

 

[Swoop1]

Nice report powerlord. Really glad things are working for you.

[AstroNebulee]

4 hours ago, powerlord said:

 

 

Get rerport Stu, so pleased it went really well for you and a stunning time-lapse. Look forward to the fruits of last nights labour's, brilliant again 👏

[powerlord]

Just thought I'd do a 2 month in update.

I've probably done around 100+ hours imaging so far. It's still holding up to weather - wind, rain, a bit of snow no bother.

Last night it was 45mph and lashing rain, but cameras showed no movement of the roof at all - no false movement alerts from the cameras, and humidity stayed stable and dry all night.

I moved the ventilation around, so there is now an exhuast fan at the top (unplugs to remove roof) - this is necessary as it does get very hot - even in March had some sunny days, and it was 30+ inside. I now have the automation set so that about 25, the exhuast fan goes on, pushing out all the hot air and it seems to work a treat. However I am also going to add a layer of white correx to the roof to reflect more of the sunlight before the summer. So automation here is >25 turn fan on, below 22, turn it off.

Humidity wise, the automation there is to go on above 65, and off below 60. Again, that works well, with it not really going high very often - only during rain, etc.

Roof still as easy to just lift off and on, and I leave it on the grass upside down during the night, pop it back on in the morning.

I've found even the monster 300pds fits in there with another refractor no bother.

The led light strip I had around the edge has fallen off when it got hot, so that needs a better fixing system.

The camera security is working great still with two seperate systems, and allows me to remotely monitor mount movement and meridian flips too which has been really helpful, especially when it's the monster flipping.

I've done a few moon capture sessions where I've been out there on my stool with the laptop and heated jacket - plenty room, and if it is a bit windy, the walls keep it stable inside.

And being all networked in has been good - I can remotely power things up during the day, load up plans on the asiairs, download the previous night subs, etc then power it down till the night all reliably.

So, so far so good really. Summer will probably need to modifications once I find how hot it gets with the white roof. i.e. maybe stronger fan, etc - we'll see. But other than that, it's been running like clockwork to be honest.

[Swoop1]

A nice update and I'm glad it seems to be working out nicely for you.