Observation session based on Alt-Az locations but no computer in the field?

[mark3d]

So I am going to setup some manual setting circles on my dobsonian for getting close to the target, and then use a right-angled finderscope to get right on top of it. Can't wait!

The problem is I would rather keep it simple and not have to rely on an electronic device in the field for looking up the current Alt-Az location of objects. I realise it would be so much easier with Stellarium on the laptop (or perhaps my Android phone), but I don't want to have to use it if I can avoid it.

Maps and planispheres seem to use equitorial coordinates not Alt-Az.

I was thinking I could plan my session in advance to view certain objects at certain times, and then I will know their precise coordinates. This would seem to constrain my viewing sessions a bit though (maybe that's the cost of not using the laptop). Alternatively, I thought I could write down how to find things relative to easy-to-find landmarks, e.g. Star X is 3 degrees below and 25 degrees to the left of Jupiter. This would allow me to view anything on the list at any time.

Has anyone else pondered this at some stage?

[bojan]

Your problem will be in a fact that both AltAz coordinates of a certain object change with time (in eq case, only hour abgle changes, DEC stays the same).

So you can't avoid a lot calculations (impossible to perform on a piece of paper in a short enough time to be practical in the field).

Your only chance (if you really don't want to use any kind of electronic device ) is star hopping - the method that was the only option in the past, but sometimes more enjoyable, and the method that will force you to memorise the sky and it's details - which may be very rewarding in the future.
You already mentioned the way - only, your landmarks for observations should be bright stars and asterisms, not planets (they are also moving more or less in days or months, so they are not good for memorising the positions of fainter stationary objects.

[Allan_L]

Hi Mark,
Yes, I have pondered this too.
As far as I have been able to ascertain, two solutions present:
1. You have already addressed it, being to run Stellarium in the field.
This works and I have had good results with this.

2. Obtain an "Astrolabe".
I understand these to be similar to a planisphere except with Alt/Az readings (instead of RA/Dec). I have not as yet been able to source one, although I believe someone on IIS has built a fully adjustable one.
I did see a UK site that would make a custom astrolabe for your nominated loacation for around 30 Quid.

I am wondering if it is possible to convert a standard planisphere to be used as an Astrolabe?

Here is a link a supplier site:
http://www.astrolabes.org/pages/personal.htm

Good Luck and report any further developments

[mark3d]

Thanks Bojan, I am not averse to learning the sky, that's the best way. I am just mindful when I have a small group standing around that it would be good to be able to quickly and easily find a few interesting targets. I guess familiarity will come with experience - I can easily find M42, Jupiter etc, now. This pushto solution might get us viewing a bit more stuff.

Thanks Allan, the Astrolabe does sound interesting. It makes me appreciate the raw calculating power required for this task that Stellarium provides - instantly telling you the Alt-Az coordinates of any object, at any time, from any point on earth.

I note there is a version of Stellarium for Android phones for about $2, developed by the creator of Stellarium, this might be ideal to pull out of the pocket, get a coordinate, and then put away again.

Thanks again fellas!

[Allan_L]

I have been searching Android Apps and have just downloaded SKEYE.
Its Free.
It seems to have Alt Az real time
AND
It says it can be used as a "Push To" navigator on a scope.
Sounds good and will test it out shortly.
Regards

[mark3d]

That looks like it will fit the bill nicely! Even if it just provides the coordinates, the degree circles and altimeter should do the rest with some precision.

[Wavytone]

Hi Mark,

Once you have altaz circles on your scope all I would do is get an Astro app such as SkyMap Pro (iPhone, I'm sure you can find similar for Android) and set it to show altaz coordinates for whatever you select on screen.

At the start of an observing session you will need to set the azimuth circle, by pointing the scope at a known bright star near the east or west horizon, and turning the circle until it shows the correct azimuth.

Adding encoders and a SkyFi adapter would make it a push-to scope and should work fine.

[gb_astro]

Usually the compass function in phones (like most compasses) does not play well with metal tube tube scopes like the Lightbridge when the phone is actually mounted on the scope, so that will usually stuff up those "push to" apps.

I was also going to suggest that a digital readout tilt meter should be more accurate (after testing it) than altitude circles since it is much less dependant on the scope base board being truly horizontal. But I see you might have thought of that?

If you go the star hopping route a Telrad finder is a great help with it's 4, 2 and 0.5 degree circles.

gb.

[AstralTraveller]

I've felt that pressure too but when you think about it you shouldn't worry. It's your scope and your expertise (however great or small) and they are getting something for free. At club nights many people have looked through my scope - sometimes too many. Sometimes it felt like an obligation to provide 'David's skytour' rather then enjoying myself. So now I still let people view through my scope but it is on my terms - what I want to see and it's there when I find it.



+1 for star hopping. OK - I now use goto but I started out star hopping and can still do it. It's very educational. If you use a telrad and charts get a sheet of clear plastic and draw/print a set of circles that represent 4, 2 and 0.5 degrees on the chart. You then centre the circles over the DSO and you can see where the visible starts should be relative to the telrad circles. This makes the telrad about 5 times more useful.

[mental4astro]

Fellow IISer, hickny, aka Peter (http://www.iceinspace.com.au/forum/member.php?u=361), has come up with an algorithm that converts celestial co-ordinates to alt-az ones using a programable calculator. His working calculator also has the entire NGC catalogue programmed into it, so he just inputs the local time (local geo co-orda preset) & the object u want, & it spits out the alt-az co-ords for you.

There are also little gizzmos that work on producing alt-az co-ords when for when the scope is moved, much like the apps for phones that measure angles. The specific one I'm thinking of name escapes me, bugger! But Peter's also got one that he's used to guide his scope. Works bloody well too! Maybe drop him a PM. I'll let him know about this thread too.

Mental.

[Allan_L]

I have just added azimuth setting circle to my DOB.

I got it from richard here (http://www.iceinspace.com.au/forum/showthread.php?t=60946) on IIS Equipment DIY forum.

Together with digital inclinometer ($25 from Bunnings a few years back).
And SkEYE android app.

Then all you have to do is align the base to North and level it and Bob's ya Uncle... well in prinicple anyway.

But I would be keen to find an Android app that converts RA Dec into Alt Az real time none the less. If they can do it for a scientific calculator, I would think an Android App was possible.

[mark3d]

Thanks for the input folks!

After playing with Skeye, I think that will solve the problem of providing realtime Alt-Az coordinates, more practical than dragging the laptop out and less effort that writing apps - thanks for the interest though.

I got a Wixey WR300 delivered from Amazon for $41, together with $3.69 at Officeworks to print the Azimuth digital circles from CN.

Now, with some planning in advance of the session using Stellarium and my book (Atlas of the Southern Night Sky), I can get a list of likely targets. The pushto system can get me close. The recently acquired 8x50mm finderscope will help to star hop, then I might actually - finally - look at the objects through the eyepiece!

It's looking good outside too...!

[gb_astro]

Allan, SkySafari, apart from probably being the best planetarium software available for a smart phone, does give a real time display of any centred object, at least in the iPhone version. Pretty sure it would be the same with the Android version, but worth checking first. Just set SkySafari to use the current time in it's "settings". You get a constantly updated Az/Alt readout to a tenth of a degree.

gb.

Edit: From the SkEye website: "Real‑time Alt/Azm and RA/HA/Dec coordinates" ??
lavadip.com/skeye/features.html

[Allan_L]

Hi Greg,
Thanks for the heads up on sky safari. Will look into that.

SkEYE - I downloaded a while back, yes it does Alt/Az.
I just haven't had a chance to test it extensively.

Alt/Az on Stellarium (on my laptop) was always "spot on" and helped me find DSO's easily, but as OP says, it is a pain running a laptop in parallel with an observing session. And the program often got buggy after the PC went to screen saver mode.

As usual, plenty of options, just looking to perfect a procedure that will work best for me.

I briefly tested the Push To (Indirect mode) option of SkEYE this week, it got close, but not as good as I'd like. But this is worth another attempt, in case it was due to "Carbon Error". I will have to study the user instructions more closely now that I have been through the process once.

[hickny]

A couple of years ago I investigated how to program my TI calculator to help me locate objects inthe sky. After many hours of research and trial and error I came up with a solution. By communicating with members of IIS I was able to find coordiantes of Messier and NGC objects and program these into the calcualtor.
Last April Troy Greenwald from the USA contacted me via email and aksed if minded if he made some additions to the program. I was stoked that somebody else found the program useful. Troy added star data and then wrote the code to include planet positions.
If you have a TI-83+ or a TI-84 calcualtor you can download the program from here http://www.ticalc.org/archives/files/fileinfo/446/44686.html
At last visit to the site some 700 downloads had occurred. Troy has been the only person though to contact me.

[Allan_L]

WOW Just found what I needed -

Try the site Tonight's Sky Here (http://www.tonightssky.com/) coordinates for an object are in RA/DEC and Alt/Az. The Alt/Az coordinates are given for several times during the night.

Make sure to select Plan Format: "Include Alt/Az over Time"

[gb_astro]

Anyone with a gso type dob might be temped with one of these.

http://www.opticsmart.com/halo-setting-circles.html?dir=asc&mode=list&order=position&price=1%2C200

Expensive but they look pretty good.

gb.

[JethroB76]

I used to use RTGUI when I was running a push-to set up on my dob -its a pity it hasn't yet made the jump to android.
In addition to providing real time alt/az on your own objects, you could do a "best of the sky" tour or produce your own lists of objects to observe by setting your own search limits (by magnitude, object type etc). It also played nicely with cartes du ceil so you could tell it to show you the object in cartes