Hi Richard,
Those setting circles look really cool
May I suggest one little thing: to improve the visibility (by reducing the number of lines) and still keep the same resolution, perhaps you could design the suitable vernier for each scale? This may be a bit fiddly to do (scale of the printout for each vernier must be reduced by appropriate factor, 9/10 or 5/6), but this may be be useful..
Such verniers were/are used on old-fashioned sextants and callipers (sometimes they have also magnifier for more accurate reading, not necessary here of course). http://en.wikipedia.org/wiki/Vernier_scale
Excellent, thanks Richard, one minor change, can you please separate them into two pdf's, one for alt, and one for the az axis.
will then take them to the local print store.
Thanks
Alistair, will do, but take the A1 size as well, you may find it cheaper to print and laminate than 2 smaller ones.
Quote:
Originally Posted by bojan
Hi Richard,
Those setting circles look really cool
May I suggest one little thing: to improve the visibility (by reducing the number of lines) and still keep the same resolution, perhaps you could design the suitable vernier for each scale? This may be a bit fiddly to do (scale of the printout for each vernier must be reduced by appropriate factor, 9/10 or 5/6), but this may be be useful..
Such verniers were/are used on old-fashioned sextants and callipers (sometimes they have also magnifier for more accurate reading, not necessary here of course). http://en.wikipedia.org/wiki/Vernier_scale
Hi Bojan, I will look into doing that, sounds like a good idea. thanks.
On my azimuth I do have a magnifying glass and find that using the 0.25 gradations is very easy.
But there's nothing wrong with more accuracy
Make sure that the calibrations will suit the situation especially the azimuth to suit the window/cutout in the upper board. May need to compress the design.
Is the azimuth going to be free to rotate independently to line up without having to move the whole dob base? With mine it fits neatly around the lazy susan (not sandwiched in-between) so I'm able to easily adjust the azimuth with a known star then lock in place with a drawing board clip. Makes it real easy.
I will be checking out Bojan's suggestion shortly.
Alistair, if you can wait till tonight I'll draw up a set with the vernier. Drawing them up is no trouble, but fitting the vernier to your pivot will be slightly more involved than just fitting a pointer. But as Bojan pointed out it will be easier to read and more accurate
By the way, You might remember that I use one of those electronic inclonometers (Wixey) for my altitude, simpler still.
Thanks Richard,
yes, fitting the vernier might be a bit tricky as it'll need to maintain proper alignment and stay rigid. but worth a try.
one possibility is to stick it to the underside of a transparent plastic piece and sticking or fixing that to the underside of the top azimuth board. so the vernier scale will be outside the azimuth scale printout when viewed vertically and will rotate with the Dob mount.
yes, i do have an inclinometer as well, will try it out. do you manage to get objects in the FOV with its 1/10th degree resolution and do you have to calibrate it often?
Last edited by alistairsam; 27-10-2011 at 04:09 PM.
Here are the pdf files for the new calibrations with verniers.
As we are trying something different, I think it may be easier to sort out the fine details over the phone. The actual size and layout may need a lot more sorting. I think the altitude is going to be to small, we can extend the radius past your actual radius but this will need a very rigid setup.
As for the inclinometer, it's simple and perfect. I set mine up by locating a main star or planet using my 6mm or 11mm plossl, set the inclinometer to zero, lower the scope till the inclinometer reads the targets actual altitude then zero it again, no need to redo unless you think you need more accuracy. I generally find my targets using my 20mm plossl, sometimes fluke it with my 11mm.
Richard,
this looks good, and it's much easier to read even from some distance....
The cutting should be done such that the black printed edges of the scales are not included - so the lines of both scales and verniers are in direct contact.
Not sure if I've understood it correctly, but wouldn't degrees need to be divided into 60 units for minutes?, so 10,20,30 .. 60?
how do we use the vernier scale from 0 to 9 to read as minutes?
Not sure if I've understood it correctly, but wouldn't degrees need to be divided into 60 units for minutes?, so 10,20,30 .. 60?
how do we use the vernier scale from 0 to 9 to read as minutes?
Currently division is 1° , so resolution with vernier is 1/10° or 6'...
For resolution of say 10', the vernier should have 6 stripes, stretched over 9/10° on the main scale.
But, I think this is not a big issue at all.
Alistair, I always use decimal degrees, I find it a lot easier and more natural for my simple brain. Note that I have been using 0.25d on my original azimuth scale with a fixed magnifying glass and I have absolutely no trouble finding my targets. My only problem is recognizing a faint object.
Using the vernier as I have drawn it your are able to read 0.1d much easier even without magnification.
Anyway, let us know if you need to change anything, I am more than happy to draw up to your needs. It's up to you to tell me the actual size/radius and which side you need the vernier.
Cheers
Richard
ps Just saw that you added a new post before I posted this one, I'm very slow at this
Sent you a PM
Last edited by richardda1st; 28-10-2011 at 05:16 PM.
Reason: ps and PM sent
I prefer decimals as well for measurements, but for astronomy, this concept of minutes and seconds is a bit harder since its in a scale of 0 to 60.
so when you look at the alt/az co-ordinates say in stellarium, that gives it to you in deg, min, sec.
not sure how you look for 21d 9m in decimals - is it 21.15deg?
my problem is converting the 1/10 vernier scale back to minutes or vice versa.
so 21deg 0.5 on the vernier scale would need to be converted to minutes, 0.5 * 60 = 30mins or 5 * 6 = 30mins if i'm not mistaken.
but if the scale was 1/12 and 0 to 60, that makes it very easy as each division is 5 minutes.
then you'd just need to watch the vernier scale till 30 lines up.
sorry if it looks like I'm asking for too much, but just my thoughts.
if its difficult, pls don't worry about it. this is ample.
Hi Alistair, I wasn't aware that Stellarium only used d,m,s. I have been using Skysafari and Starmap Pro which allow you to use either.
I don't understand your numbers but I have made a vernier with minutes for the azimuth, have a good look and advise me as required. You may want to move the vernier to the inside, or whatever.
After that we can sort out how you want the altitude laid out, if you still want it.
Don't concern yourself about asking to much or to difficult. It's not costing me any money and I enjoy the exercise, so long as we get a perfect result.
Had another play around with the vernier, now I've got the hang of it.
I think this is what you are after Alistair, or maybe just 30min instead of 60min. This will be very easy to use, and very accurate.
Thanks Bojan, I wish you had mentioned it earlier.
Cheers
Richard
ps To those of you who have the earlier versions v.1
If you like to upgrade to v.2 just let me know.
Thanks Richard,
it does look much better. I will print it out and give it a shot.
A suggestion, is it possible to make it half the arc size with 60 minutes?
the current vernier is from 0 to 60 degrees (main scale) and may be too wide to get a quick reading, if the vernier is from 0 to 30 degrees (am referring to the arc length) it might be quicker as number of gradations would be half.
it might be a good idea to practically try out both the sizes in the field.
if you could draw up the smaller scale, i'll print both and bring it to snake valley and we could try it out.
we may not need to fix the vernier scale under the top baseboard. I plan to make an adaptor fixed to the upper face of the top baseboard with a double L bracket. so just need to print out the vernier scale.
I will attach some pics.
Hi Richard,
I presume we'll have to zero the vernier scale once the azimuth scale is rotated during star alignment or align the scale to the objects minutes value?
we'll have to think up an adjustable holder for the vernier as well that can be locked when zeroed.
..... it might be quicker as number of gradations would be half.
Hi Alistair,
If you want the same resolution 1arc min), the number of graduations will be the same, only the distance between them will be halved, meaning you may compromise the readability somewhat (in the dark... it may be tricky for some).
I meant half the gradations with half the resolution as 1 arc minute resolution may not be required to locate visual targets if the TFOV is around 1degree.
so if the resolution of the vernier is 2 arc mins, the line spacing would be similar to the current one but half the number of lines to visually align.
moreover, in the 10 secs or so that it might take to move the mount to the co-ordinate, the object would have moved by 1 to 3 arc mins in Az anyway.
I'm happy both ways, but a practical field test for ease of use would be the best way to determine optimum vernier scale.
