Degrees horizontal and vertical

[JOC]

I ascertained in a previous thread that at my location I am practically spot on for North alignment if I use a magnetic compass (the difference not being great than the distance I can see in many EP's).  I've noticed that my mount has a scale printed on it, which when I set the pointer to zero lays the OTA perfectly horizontal.  I have to do this before I start the electronic calibration.

Now comes the silly question: 

Does it follow that if can find something to give me degrees N, S, E or W degrees and the up and down degrees on the up and down axis (is this declination?) of a celestial object that I could find that object easier in the sky using a compass and this built in u/down scale on the occasions that I wasn't using the Goto?  I was even wondering if there was a way of marking the degrees around the base of swivelling base on the stationary part of it to even do away with the compass use.  All ideas/comments welcome.

[billyharris72]

Hi there:

From your kit list it sounds like you are using an alt-az mount, so the scales on the mount will be altitude and azimuth rather than RA and DEC.

Because of the Earth's rotation, the position on an object with a given (fixed) RA and DEC will change in Alt and Az, so it is not just a matter of moving the scale to the celestial coordinates of the object, unfortunately. Working out Alt-Az from RA and DEC requires you to know your latitude and longitude and the siderial time at your location and then do a bit of maths that is probably not worth the effort when you could just use a star map.

On the other hand, if you have Stellarium set up to give your location you could grab the alt az coordinates from that - those should align with the object's locatiion in the sky.

Be aware though that this is not likely to be that accurate - it will get you in the right bit of the sky, but may not put the object in the eyepiece FOV. I've always found star hopping to be easier and more reliable.

Hope this helps,

Billy.

[JOC]

Hi billyharris72 - I tend to take the mobile phone version of Stellarium out with me and I've just taken a look.  If I click on a star (rather than 'wish' upon one)and expand the data box I get a rapidly incrementing set of figures which claims to be Az/Alt Currently showing a star in Libra almost due south and almost bang on the ecliptic, this is showing around +180"50' and +22"12'  The second set of values harldy increments at all compared to the first.  Given that due South equates to 180" that implies the first set of values are the North/South values and the others are the up/down movements, ergo if I had the scope facing south and notched the OTA up to 22" I should roughly be in the area of the identified star - in my example its something unpronoucable - zubenelgenubi! - Yes?

[billyharris72]

Spot on. It's saying that the star should be at compass bearing 180 deg 50' (i.e. South) and angle of elevation (alt) of 22 degrees. So if the mount is level and your 0 is pointed North (and provided your scope is well aligned with the mount; it can be a bit out) positioning the scope such as to "dial in" those numbers should leave you pointed at the star.

[happy-kat]

Members have added setting circles to their DOB bases. These give azumith and a wixey can give altitude and used in either absolute or relative terms.

[JOC]

Excellent.  Google has provided an explanation of a Wixey (a digital inclinometer), but I think the marks on the Dob base covers the incline degrees - there is a scale which has a marker on the moving part for getting it level

The hardest job might be making non permanant marks on the non moving part of the base 

[SilverAstro]

10 hours ago, JOC said:

up and down axis (is this declination?)

 

44 minutes ago, JOC said:

 the marks on the Dob base covers the incline degrees - there is a scale which has a marker on the moving part for getting it level

1) No, the up & down axis is not declination.

2) As you say, it is the incline degrees relative to the base. If the base is set level to the 'ground' (edit : ie your horizontal - not your hillside ) then these incline degrees will only then set your scope 'level'. 

When that is all done the incline degrees become the same as the Altitude (Alt) degrees in your Stellarium.

The "rapidly incrementing set of figures" can be ignored for this purpose, it is just the slow moving degrees bit that you need to watch.

hth

[JOC]

8 hours ago, SilverAstro said:

If the base is set level to the 'ground'

Ah, yes, that's a good point to emphasise - I will need to make sure that the whole telescope set-up is level.  It probably won't be sufficient to just think it is level - I reckon a tiny cheap bubble level might be needed.  I think it might be worth looking into what might be possible as it will help me to manually shift the telescope to a rough position and then I won't need to wait as long for the goto to shift it - the advantage of the on-board system is that I can push it without upsetting the electronic movement.

[happy-kat]

I printed and laminated my azimuth scale then selotaped to the board. Get the direction right for the degrees as it goes the other way if attached to a top board.

[Cosmic Geoff]

Before I bought a larger telescope with GoTo, I experimented with finding objects with my 102mm refractor and alt-az mount,  using the altitude and altitude from Stellarium, the alt-az scales on the AZ-4, and a Wixey gauge. I found that in practice it was a waste of time. Using the Wixey to give an altitude for the manual EQ-5 and the 203mm Newtonian was no more useful.

[SilverAstro]

3 hours ago, JOC said:

 I reckon a tiny cheap bubble level might be needed.  I think it might be worth looking into what might be possible 

  I can push it without upsetting the electronic movement.

A timely post by Cosmic Geoff ! Because I was just about to post that you may need something a bit better than a cheap bubble.

It all depends upon what you intend it to do. If it is just to get you pointing in the right general area of sky, - to speed up the GoTo - as you would standing by a friend and pointing with an arm "It is up over there" then fine.

But if you want it sufficiently accurate to get it in the field of view of your finder ( or, perish the thought, your main scope) then that is a whole other kettle of fish involving at least two carpenters levels set at right angles I'd av thort ?

An experiment with a homemade theodolite type thingumy might be a preliminary step, ( Blue Peter + toilet rolls to the fore !! )

Ah, I wonder, develop that thought, a long stick mounted on swivel with protractor type scales to point out the right area of sky ?? To get familiar with where you need to be pointing, even to select the right-ish star near to your target.

You might end up building a Torquetum even,,, No! not joking, just thinking out-loud here over morning coffee

[JOC]

"Torquetum"

You've just go to love Google - is today's 'thing learned'. 

This is an interesting discussion - it even makes me think that I should do something about making sure the base sits level when I try to calibrate it - Yes, I can sit the OTA at zero on the up/down scale, but clearly this is not absolutely level unless the base I is sitting perfectly flat.  As it is, I normally dump it down on my gravel drive - think 'yeah, that looks fairly square' and run with it.  It may be that a little more attention to positioning would result in more accuracy from the Goto.

[SilverAstro]

4 minutes ago, JOC said:

"Torquetum" You've just go to love Google - is today's 'thing learned'. 

  It may be that a little more attention to positioning would result in more accuracy from the Goto.

Thort you might like that

yes, perhaps, especially if using a one-star method, tho it is more needed to increase the time the found object remains in the eyepiece (there's a huge set of variables)  If doing the whole proper job on 3-star then assuming the manufacturer has used the full math then it should not make much difference. (but that is a whole different topic, as is your previous Q. about Declination, which we can return to at suitable time if ,, ) 

[Astro Imp]

39 minutes ago, SilverAstro said:

yes, perhaps, especially if using a one-star method, tho it is more needed to increase the time the found object remains in the eyepiece (there's a huge set of variables)  If doing the whole proper job on 3-star then assuming the manufacturer has used the full math then it should not make much difference. (but that is a whole different topic, as is your previous Q. about Declination, which we can return to at suitable time if ,, ) 

The scope owned by the OP only gives the option of two star alignment. With a reasonably accurate home position to start I have found the GOTO surprisingly good.

[JOC]

It is surprisingly good Alan, but sometimes, I cba to carry all the electrical stuff outside and any option to help find stuff manually is always helpful.

[Chefgage]

On 06/09/2017 at 22:55, JOC said:

Excellent.  Google has provided an explanation of a Wixey (a digital inclinometer), but I think the marks on the Dob base covers the incline degrees - there is a scale which has a marker on the moving part for getting it level

The hardest job might be making non permanant marks on the non moving part of the base 

Have a look at this thread i started. It shows the wixey gauge for alt and a digital rotary encoder for the az reading and how to use them/set them up.