DOB SETTING CIRCULES-AZIMUTH & ALTITUDE

[bcfcciderhead]

Like most dob owners i wanted to add setting circules, so after reading some post's here i set about the task.

I was going to have the circules for the base plate printed out and stuck to the board but decided to write them on myself, so how to work out 360 degree marks?, easy, the hole for the turntable should be centre so i point a pencil line through this to form a cross,i then placed a protractor on these lines and marked of the marks, these gave me equal spaces for 360 degrees.

I then cut a piece of the turntable away to show me the numbers, placed a metal strip on the turntable and added a magnetic marker to the strip, i will use this to "fine tune" to polaris, i also countersunk a compass just to get me close.

For the altitude settings i found a template to print out and laminate, fixed this, and with the scope level, glued a pointer to the scope and have it showing 0 degree.

For the markers i just used some bendy metal painted black with red ends and glued.

Just to aid setting up i drilled a hole through the the turntable and base and i dropped a bolt through to stop the two turning, then using the compass just pop the dob mount on the ground pointing north, take out the bolt and fine tune when aligned to polaris, move the magnetic marker to 0 degrees on the base and level the base (i have a small level fixed to the base).

Have not yet tested any of this due to our lovely weather here in Wales but can't see why it wont get me somewhere near my targets, of course i dont expect to be spot on but with my 32mm EP fitted, should be close enough to see them...i hope.

Of course you coould use a Wixey which i was going to do (still might if it fails) but thought i'l try altitude scale first.

I must say thanks to "Doc's" thread for setting circules which i took most of the plans from...cheers Doc

[PARTY MARTY]

Wow!

I've never seen any Dob setting circles have been made proffesional made like this before. I have seen many, but your design looks standard as if it is part of the scope.

I've no idea why Skywatcher ever come to some idea like this in the first place is beyond me.

However I have goto but you have the advantage than me cos you saved Hundreds £ to achieve a manual goto.

I guess you're using stellarium program to get co-ordinates for DSOs then??

I like the way how you have mounted the Silva compass on the the dob base, superb mate.

Have you considering any adjustable legs for the base, it is criucial that you get the dob perfectly ground level so you can find objects more accurately!!!

Fantastic Modification Lol!!!!!

[bcfcciderhead]

Thanks for the kind feedback, i have adjustable legs to add leveling (you can just see them in the last pic).

I can use stellarium and will do when i have myself a laptop lol, but for now i have a book with all the messier odjects in and there location.

It still amazes me also why Skywatcher or any make dont do this as standard, they must see theses forums and get feedback from customers, it's such a common mod.

[Doc]

Glad you liked my idea.

You will find that they are pretty accurate, I can get the object into my FOV of my 16mm at 0.72° almost everytime.

[brantuk]

Great job bcfc

[acey]

I can use stellarium and will do when i have myself a laptop lol, but for now i have a book with all the messier odjects in and there location.

Very nice work. Unless you're going to put the dob on an equatorial platform you'll need Stellarium or other software (or an astrolabe) to convert from the RA/Dec co-ords in your book to the alt-az co-ords of your circles.

[bcfcciderhead]

Thats a good point Acey, all i need now is a better understanding of the co-ord, i can see them in Stellarium both RA/DEC and ALT/AZ but of course these change as the time goes by, so it's no good me writing some down ready for a night's viewing unless i view these at the exact time...if you see what i mean, so how come they can print these co-ord in RA/DEC and they stay the same?, well seem to, and after looking at my list and then on Stellarium they are the same, just cant get my head around this.

[acey]

RA/Dec co-ords are fixed on the "celestial sphere" (which the stars themselves appear to be "fixed" on). Alt-az co-ords vary depending on your latitude and the time. Astrolabes were designed to make the necessary co-ordinate transformation; a planisphere is a simple astrolabe but without the grids that would make it possible to do the conversion accurately. So best use software such as Stellarium.

I've thought of making circles for my own dob but I don't use a computer with my scope so I'd need to make an astrolabe too - I've just never got round to it.

http://www.astrolabes.org/

http://en.wikipedia.org/wiki/Celestial_coordinate_system

I've also put this link up in response to your other thread (http://stargazerslounge.com/beginners-help-advice/130016-help-understanding-ra-dec-alt-az.html#post1694602)

[LukeSkywatcher]

Looks great Dave. I have a wixey for my Alt and have been thinking of making some AZ circles.

Looking at yours im thinking "How hard can it be".

Putting it on the Dob base might be the tricky part.

[bcfcciderhead]

I was always a bit unsure of doing it myself Paul, it really was easy, just remove the base part and as the hole is dead centre (well i hope so) use a protractor to get the 360 degree marks, your see what i mean when you try it, i thought if it dont work and i cant get the correct measurments, no worrys it's only pencil, rub it off and put it back together, no harm done, or just print them of, i did for the alt ones.

heres the link with the printable scales

Sky-Watcher SkyLiner 200 Dobsonian Telescope

[LukeSkywatcher]

I dont suppose anyone has a link to a template that i can download and print off with the AZ measurements on it?

Just thought i'd ask.

[Doc]

Here Paul

Setting Circles - You are not logged in

[LukeSkywatcher]

That's brilliant Doc. Just what i was looking for.

Thanks.

I just have to figure out how to put what one i want onto a disc and take it to my local print shop. I'd also have it laminated.

I dont think my printer can handle a job that big to fit my Dob base.

Much obliged.

I am one step closer to having AZ scale on my Dob.

[parkway]

I added setting circles to my 12" Dob last year (well, az scale plus wixey). I picked up a cheap Palm PDA off fleabay (Tungsten E for £8). There's several FREE Palm programs (Astro Info, 2sky) which you can download and will give you Alt/Az coordinates. both programs have plenty of catalogues (although you may need an SD card should you wish to install the big star catalogues - as they also function as planetariums). Both programs support Night Vision and you can turn the brightness of the display all the way down. The only problem is a 2-pixel white border (inherent to all Palms) but I don't find this to be an issue. It can easily be covered over! (either tape or red acetate)

You can get a program to blacken the border on the Palm TX/LifeDrive models but they're much more pricey (40-50+ 2nd hand). But there's no point given the price of the older models.

The only real issue is trying to use it with a stylus when your fingers are freezing off!! Some kind of cradle to hold it would be marvellous.

Astromist is also an excellent program, but it's commerical. And there's another one called Planetarium, which is shareware but fully functional. All are great tools to play with for the sake of a tenner.

[bcfcciderhead]

Thanks Parkway, never thought of using a PDA, thats all i really want, just something to give me the ALT/AZ coordinates like stelliurm does.

[parkway]

The beauty of programs such as Astro Info, and Astromist, is they can help you plan your sessions as well. You can search for objects in certain parts of the sky. You can also filter by type of object, magnitude, so on and so forth. Very handy. While Stellarium is indeed a great piece of software, it is primarily a Planetarium. And not everyone wants to lug their shiny laptop out into the garden.

There are other tools for looking up AltAz, such as using Psion's, graphic calculators. But I think given the price of a 2nd hand palm, and the excellent programs available for free.. Palm is definitely the best route if you find it inappropriate to lug the laptop outside.

If there's enough interest, I would consider writing a small tutorial on using a Palm to look up AltAz coordinates.

[bcfcciderhead]

thats the only reason i'm thinking of getting a laptop for, to take outside to use Stellarium and the like, so something like a PDA would be great, as would a tutorial (for me at least lol) , just want to get home now and search fleebay

[parkway]

If you don't have a laptop already, then a Palm would be more suitable. Unless of course you can think of uses for the laptop other than using it as a tool to look up Alt/Az while out with the telescope. You don't need a flashy Palm like the T/X which often go for over 50 pounds. I find the Tungsten E to be perfectly adequate. Make sure it's in good condition, complete with charger. The only thing you're at the mercy of, with them being quite old devices, is the quality of the battery. Unfortunately they're not simple to replace as they're soldered to the board. So if you're unlucky that the battery doesn't maintain it's charge very well, you can buy a replacement, but you will need to be handy with a soldering iron. The Tungsten E's usually go for around 10-15, but I got mine for £8.

I shall write the tutorial. I'll post back when it's complete. :-)

[bcfcciderhead]

Thanks Parkway you have been very helpful, top man.

Due to the I.T lot here in work my internet is limited but did manage to get on Amazon, can't believe the price's, looks like some good one's in the £50 mark which i dont mind paying, is there any kind of spec i should be looking for?

and yes it is only to use with the scope to find ALT/AZ co-ord

[parkway]

Hi Dave,

I'd probably stick to eBay. I find the "buy it now" prices on sites like Amazon, etc. to be rather inflated. There are many bargains to be had in the auctions. There are of course many models you could use, ranging from a fiver to 70 pounds!

The most basic palm models have mono displays which aren't backlit, possess little memory, and no memory card slot. While the more expensive ones will run any kind of software. Obviously a colour model will allow you to use the night vision feature of the software I mentioned and are backlit. When I initially got the idea to use a Palm, I found the Tungsten E model to be the best priced (for second hand) in terms of it's specs and it comfortably runs the programs I use whilst at the telescope. Like you, I need it purely for locating objects. Don't confuse the E with the E2, which is a better version of it, and thus more expensive. The E is quite capable and I did really only pay £8 for it. And I've never seen one go over the 15 mark. Wiki link.

I've started work on the tutorial. Rather than write purely about the Palm, I will cover other options so you can get an idea of what would suit you, rather than rush out and buy the Palm. :-)

Peter

[acey]

An option would be to cover the screen with red film (e.g. Rubylith or Lee filter gel).

It would be nice if some designer could come up with a gizmo with very big buttons (for use with gloved hands) where you'd input latitude and local time at the start of session, then type in RA/dec co-ords to get alt/az. A programmable calculator would do it.

Alternatively I suppose you put encoders on the dob and make it read out RA/Dec, then you've got push-to.

[parkway]

Yeah, I've seen quite a few methods of getting coordinates. Psions and graphic calculators. I like having the databases of objects at my disposal though. Using any device is a problem in the cold!! I still need to devise some kind of cradle to hold the Palm in. Something like a sat-nav holder with a suction cup stuck to the OTA would be ideal.