saac
-
Posts
3,459 -
Joined
-
Last visited
-
Days Won
4
Content Type
Profiles
Forums
Gallery
Events
Blogs
Posts posted by saac
-
-
I would tend not to allow creepers or any vegetation to grow on the walls of the obsy just from the point of view that they may get in the way of any routine maintenance ; painting , oiling etc. If however you are looking to use the creepers to help blend in the observatory to the garden then I 'd go ahead with that - I think it is really just a personal judgment. Just accept that you may have to manage the creepers by occasionally cutting back . You may here some caution about how vegetation can affect temperature regulation of the obsy but to be honest I think any effect would be marginal, besides once the roof is open the temperature equalises to the outside very quickly.
If you are not looking to do imaging then yes no real need for a permanent pier. If your observatory will be secure and you are content you could simply use a tripod semi permanently placed to give some sort of resemblance of permanent alignment. Alternatively there are pier designs which have used light weight aerated building blocks (thermalite - one trademark) - such a pier could be bolted to a concrete pad in the ground and easily dismantled if and when required.
At the end of the day anything you do which gives a move towards a more permanent setup is going to increase your time at the eyepiece. As a wild card option, if you are not looking for a permanent setup, but more concerned about shelter and blocking out light then you may want to consider a tented type solution . You could again go DIY or there are some commercially available "observatory" style tents available.
Do you have anything in mind for the structure - would it be purpose build or an adapted/modified commercial shed say.
http://astrograph.net/Observatory-Tent-3m-x-14m
Jim
-
1
-
-
No reason why , structurally, you could not make that design work. Of course blocking the sides like that you would be restricting a large amount of your view but if those aspects are badly light polluted them perhaps not such a loss. Have you considered perhaps a dome ? Would your use be visual or imaging or both?
Jim
-
1
-
-
On 26/02/2021 at 09:04, planetman83 said:
Hello,
my name is Manos Tsikalas. I am the owner of the company PLANETARIUM CRETE in Greece. We provide starry nights and planetarium services in the beautiful island of Crete.
A few days ago, it came to our hands a 24.4" f/3.2 primary mirror and a 5.3" secondary, made by John Nichol optical , so our duty is to make a very beautiful, functional and well made truss dobsonian telescope.
My friend Dimitris Manousos designed a very clever sketch of a secondary holder that we already printed. They are 2 parts that hold the secondary together like a sandwich. It is a little larger than the secondary in every dimension so it does not deforms it.
I personally made the spider and the system that aligns the secondary. I made the spider vanes at 80mm offset to each other. At this geometry the spider vanes are mostly loaded in tension when you try to rotate the holder. A very important thing here is for the height of the upper cage to be as small as possible. I have calculated that it will be 28cm total.
I am going to use carbon fiber truss poles for the trusses and for the struts of the upper cage. Using carbon fiber stiffens the construction and the weight stays low. I will kydex or 2mm birch plywood inside the cage also. The goal for the upper cage is to be no more than 6-6.5kg, moonlite 2 speed focuser included.
The height of the mirror box is going to be also 28cm total.
I made a draft sketch of the upper cage and of the mirror box. I haven't decided yet about the truss connections to the mirror box and to the upper cage. There are many solutions, but I am trying to find the best, easier and more durable. Do you have any recommendations?
Hi Manos , I like your secondary holder , It will be good to hear how it functions once you get the secondary mounted on it. I also like your spider, I made something similar for a 16 inch build a few years ago, if you would be able to show more photographs of your spider at the hub and how it carries the secondary I'd be grateful. As for truss connectors, with my build I went for the standard moonlight drelin connectors - I'm not sure that they still make these components anymore. It's a shame because they work really well.
Jim
-
4
-
-
Reasons for plywood in particular are: relatively low cost, good availability , good strength to weight ratio, and ease of working. In general, these are the most common reasons for any material specification in any project. Remember that the classic Dobsonian mount as advanced by John Dobson was intended as a low cost option that would be within the reach and capability of amateur backyard astronomers.
For the mirror box you are looking for a material that is dimensionally stable and lightweight. Quite a few minimalist designs (commercial and diy) use a space frame solution where the mirror cell is held in a minimum structure space frame; great solution for portability.
Jim
-
2
-
-
What an amazing image.; detail holds really well when zoomed in.
Jim
-
There is a lovely video clip of it crossing Orion on the BBC web site - starts about 13 s in .
https://www.bbc.co.uk/news/science-environment-56241511
Jim
-
4
-
-
1 hour ago, PEMS said:
I would think that as Methane could be either organically formed or from another inorganic mechanism then the finder of such methane has two options:
Say that it is just Methane and forget it, or, say it could be from some form of microbial life.
If it is found out to be from some form of life then they were amoungst the first to identify a form of proof of life and some kudos. Otherwise they are the person to have seen what could be proof of life then ignored it.
So may as well push the "possibility of life" aspect. They have done the same for Venus and there the atmosphere is sulphuric acid, hot enough to melt lead and a pressur 90x that of the earth on its surface.
To be fair the situation on Venus is a little different from Mars where Phosphine, as I understand, has no other known production pathway other than organically ( anaerobic processes) . From what I remember the team simply reported detection of Phosphine (by radio detection) in the upper atmosphere of Venus well above the cloud level. At this altitude Phosphine molecules would ordinarily be destroyed due to ultraviolet radiation. Therefore, if its presence was confirmed then that would suggest some form of replenishment process - again not necessarily and conclusively organic ! Since their initial publication other researchers challenged the findings but the debate I believe still continues. With the Methane on Mars there is no way to confidently declare it having been produced by life or otherwise without testing a real sample by say mass spectrometer - measuring isotope ratio of carbon 12 and carbon 14. The notion of a simple bio signature that could uniquely and with all certainty point to life is tantalising but it must surely be fraught with difficulty. As with Venus and Mars there will always be the unknown exotic chemistry route . I can't see how any remote discovery of a bio signature anywhere could only ever result in a claim that there is a potential signature of a life process. It's certainly an interesting area and we are going to see more discoveries as the JWT will open up atmospheric analysis of exoplanets.
Jim
-
Two types of methane organic and inorganic (abiogenic) - determined by their production method (pathway) ; the former would obviously be the cause of great interest if detected elsewhere in the solar system.
Jim
-
1
-
-
12 minutes ago, Skipper Billy said:
Point of order - its either 'over' OR 'out' it cannot ever be both. 😃😃😃😃😃😃😃😃😃😃😃😃😃😃🙃
'Over' means over to you.
'Out' means conversation end.
As a mariner it annoys me to hear that phrase in films etc
"say again , over "
-
2
-
-
You could try running it on SharpCap to see if it is a problem with the camera or the software. My last use of PoleMaster I had a problem when it came to making the axis adjustment no associated movement was shown on the screen - it was as though the camera had frozen. I disconnected and ran the polar alignment routine in SharpCap using the Polemaster as the camera and all worked well. It must have been a software issue. I haven't investigated it any further - I have a permanent setup so only do a polar alignment about once a year.
Jim
-
1
-
1
-
-
That is cool. Now please tell me that the professional astronomer he reported it to did not put the coordinates in an envelope and then drive down a poorly lit mountain road at high speed colliding with a truck and killing himself. Thus setting off a chain of events in which the teenager's name is given to the newly discovered celestial body which turns out is hurtling its way towards Earth to bring on an extinction level event . Sounds like the plot of a movie
In all seriousness, well done that young man , kudos to him.
JIm
-
2
-
-
On 30/01/2021 at 22:53, Nigella Bryant said:
I can't see a thing at night through my scope's, lol.
That is some light pollution you have there Nigella
Love your setup.
Jim
-
On 20/01/2021 at 17:15, PeterStudz said:
I’m new here and my first post. My 9 yr old daughter is astronomy mad and wanted a telescope for Christmas. But because of the shortage I couldn’t get what we wanted. Ended up with a Skywatcher skyhawk 1145p. Really wanted something with a little bigger primary mirror and simpler to use. Still, we were lucky to get that and at a reasonable price!
Started off looking at the moon but have only had 4 clear nights since Christmas. And one of those was working out how to polar align and getting use to everything.
This is our first picture of anything in the nights sky. My iPhone 12 was literally gaffer taped to the eyepiece. The stock 10mm. Just pressed the shutter for (I think) a 5 second exposure. All I could do without too much star trailing. Then a little noddy “processing” in Camera+ in order to reduce the light pollution. We are in a city, Southampton, England, so it’s no exactly ideal. Still, when my daughter saw the result she was literally jumping up and down. I known it’s far from perfect but still pleased for a first attempt.
Nice as it’s something we can both do. I hope that she won’t get bored too quickly. The biggest issue at the moment is the lack of clear sky. We now have a phone mount, a couple of better eyepieces and a cheap motor drive. Much to learn!
Peter that is actually superb for an introduction to astronomy especially for a 9 year old. What you have done makes for a really simple and quick set-up and yet produces an image that should enthral any 9 year old (even adults) to get them further interested. What I really like is the immediacy of the image - no long waits for post processing which to be honest can take a lot of the shine out of it. I can well imagine why your daughter would have been delighted with that image, it really is excellent. Maybe have a go at something like Pleiades next or even Andromeda. Andromeda will most likely just be wispy but once you explain to your daughter what that wispy cloud represents (over 100 billion star) I'm sure she will be jumping up and down again. This really is what astronomy should be like at the introduction level - I wish it had been for me when I was at that age - the thought of seeing your Orion nebula shot when I got my first telescope as a kid would have been like magic. I wonder what your phone would make of Jupiter or Saturn!
Jim
-
1
-
-
Welcome to the Hexagonal observatory club Aspic and well done on what looks like a truly solid observatory. For mine (octagonal) I modified a commercial garden summer house - I put cross bracing in the roof and installed a third middle rail to support the roof as it travelled on and off. Like you, I do like the shape over the the rectangular version , and they are perfectly strong once properly modified. I love your winch mechanism for moving the roof does it also function as a hold down against high winds?
-
2
-
-
Shame , it would have been good to have a change of news from the Coivd narrative.
Jim
-
10 hours ago, malc-c said:
Ah... I see... However there is one fly in the ointment... The AstroEQ site has been closed since lockdown last March of last year
With everything in short supply, or sites off line it's going to be hard for the OP to find a resolution - hopefully something may come up in the second hand market
Yep and that is exactly why I mentioned that in my original post!!!!
If the OP wishes to follow up on the Astro EQ then a search for a unit on the 2nd hand market may be worthwhile. Indeed there is also the potential to build your own! Plans and component lists are readily available not least from EQMOD itself. All these options may or may not be of use to the OP or indeed anybody who subsequently reads the thread but they represent a potential route to an effective goto mount at reasonable cost.
Jim
17 hours ago, saac said:Astro EQ may an awful lot cheaper option; I've used it myself and I am sure it would be acceptable but you would need to confirm compatibility with an EQ2 - I'm sure it would be. You would need to add suitable stepper motors - NEMA 17 would most likely be suitable. Only trouble is that it is not available at the moment during pandemic so if you are not in hurry it may be a much cheaper option.
https://www.astroeq.co.uk/purchase.php
Edited - this would suggest it imay be possible https://www.astroeq.co.uk/forum/index.php?topic=154.0
Jim
im
-
3 hours ago, malc-c said:
Then add the cost of the EQ5 pro goto kit ( £330) as it is just a manual mount and you end up paying more than the new warrantied EQ3 pro goto
Plus
So you have the additional cost to purchase a new weight, as without it the mount is useless !
Not the best referral Jim
I did not suggest EQ5 go pro kit at £330 , I suggested Astro Eq which comes in at approx £80 . Quite a sensible referral I thought for a budget EQ5 goto. It is what I started with
Jim
-
EQ5 for sale £120 on UK Astro Buy and Sell at the moment
https://www.astrobuysell.com/uk/propview.php?view=170247
Jim
-
Astro EQ may an awful lot cheaper option; I've used it myself and I am sure it would be acceptable but you would need to confirm compatibility with an EQ2 - I'm sure it would be. You would need to add suitable stepper motors - NEMA 17 would most likely be suitable. Only trouble is that it is not available at the moment during pandemic so if you are not in hurry it may be a much cheaper option.
https://www.astroeq.co.uk/purchase.php
Edited - this would suggest it imay be possible https://www.astroeq.co.uk/forum/index.php?topic=154.0
Jim
-
I think the roll away shed like that on the video linked by fifeskies is the easiest and neatest solution for a large Dob. Fairly easy to build as well no worries really about keeping watertight etc.
Jim
-
13 hours ago, Skipper Billy said:
You can control this relay board via Alexa 😉
Yep I noticed that ; makes it doubly attractive. I've bookmarked the page I think I may be using it in the near future .
Jim
-
That's a neat solution Billy. At the moment I have my main camera and the general observatory camera controlled by Alexa via standard smart plugs. Relays look a more practical solution once the number of devices starts to rise. That's a reasonable price as well for the board .
Jim
-
I follow the argument regarding how we have measured c but I don't understand what supports the premise that the speed of light may/could be anisotropic. The speed of light being a property arising from the nature of the particle (photon, massless) and the two constants which describe the permittivity of free space (the electric constant) and the permeability (the magnetic constant). So what I don't understand is that are we saying the values of these two constants change for a particular part of the return trip? Or have I missed something, quite possible, and usually often
from Maxwell's equation's C = 1/ (ϵoµo)1/2
Jim
-
2
-
-
Learning arduino -working my way through the Arduino ASCOM Focuser Pro2 DIY. On past experience my soldering is less than effective so I've gone for a solderless version.
Jim
-
4
-
In all seriousness, well done that young man , kudos to him.
24.4" f/3.2 truss dobsonian project
in DIY Astronomer
Posted
Manos thanks for the photographs showing more detail of the design. I've never been entirely satisfied with mine so I may take some design leads from yours, it looks more substantial and up to the job.
Jim