View Full Version here: : dumb question about scp.
04-08-2012, 04:01 PM
Howdy all. Slowly progressing with new hobby. Picked up a second hand goto mount for nothing. A little forlorn looking, without scope i must say. :shrug:. Anyway, my question. If I stand with my arm pointing south, then raise my arm 40 degrees(my lat.) am I pointing to the cel. south pole. Is it as simple as that. Or is it that I'm simple. Old guy alert.:screwy:
04-08-2012, 04:11 PM
Hi Rolls-you need to point TRUE south, not magnetic south. True south is about 167 degrees magnetic
yes, it is as dimple as that. that's what you do with the mount, though. not with your arm. ;)
true south, though, not the magnetic south.
maybe, you can put your camera somehow on a mounting plate on the mount? and use it's life view for star alignment with the hand controller?
to take some wide field exposures until your first scope arrives...
which mount did you get?
find out your magnetic declination http://magnetic-declination.com/ (http://magnetic-declination.com/)
so, on a normal compass, the needle should point about 20 degrees east of S.
04-08-2012, 04:38 PM
Sorry Rolls-I wasn't thinking about you being in New Zealand-you have a different magnetic declination to me.
Thanks for correcting that Silv, but the compass needle will still point magnetic south. The mount needs to be pointed 160 degrees.
04-08-2012, 06:33 PM
Great stuff. So I had the right idea,just 20 degrees out. never knew about this declination stuff. So, aim mag. south then according to silv's link turn left 21 degrees. then up 40 degrees, and I should be looking at the vicinity of the scp. So now I can see what the scale on the mount means .Latitude. I've just got the mount plugged in to my 12 volt jump start pack (never thought I'd be using it for this) and it all seems to work ok ,cool. By the way silv, you gave me an idea for mounting the camera . I'll make an aluminum bracket to fit in the dovetail on the mount for the camera. And, I can also use it to mount my barndoor tracker. The possibilities.Love my new hobby. Cheers all.
04-08-2012, 06:51 PM
Oh, and the mount is a skywatcher synscan goto. The scope was nicked in a burglary apparently. So now I have to figure out what to get to to replace it. Still, cant moan. I got the mount for next to nothing.I would just want something I can use for photography. as well as viewing.Cost negates me buying a refractor so i guess a fast newt or something. Not sure. Dont know enough about it all yet.I mean a couple weeks ago I was happy just putting my camera on a tripod.
yeah, enjoying every step along the way :)
lucky you got that mount for nothing!
do you know it's proper model name, maybe?
EQ1,2,3,4,5,6? HEQ5? Something like that?
From that model name you can then find out how much load it can handle. That should then be your guide for when you will buy a scope for it.
when you put your camera on the mount, you should point the lens parallel to that bracket it'll be sitting on - as if it were a telescope.
You will want to practice the star alignment feature of the Synscan hand controller, too, don't you?
The camera in that position will assure that your tracking can work.
05-08-2012, 01:47 PM
Thanks silv. I'll sort it. Finally got my head around the true south and solar noon . I didn't realise it was all quite simple really.
05-08-2012, 01:52 PM
Oh, and if you're still checking this thread, could you tell me if your newt is ok for photography. I think I saw that you had one. I believe they need to be fairly fast for deep sky stuff. Cheers.
yes, the f/5 ratio of my 8" ratio is good for A(astro)P(hotography).
focal length 1000mm / aperture 200mm = f/5
the smaller that number the better for AP. you need less exposure time and you have a wider field of view. (I think...
I'm a noob, so don't take my word as a bible unless I sound as if it is gospel.)
here (http://www.12dstring.me.uk/fov.php?pxsize=5.1&pxwidth=4592&pxheight=3056&camera=Sony+A290), you can get an idea what your field of view with a telescope and your camera chip would be. (choose M31 for example from the white objects menu.)
if you click the red link "switch to visual view", it also covers the FOV for telescope and an eyepiece.
my mount is an EQ5. max load 9kg as advertised by the manufacturer.
for AP, one has to almost half that advertised weight to be in the proper tracking range of a mount.
my mount is totally overloaded with the tube, the focuser, the dove tail bar, tube rings and camera - 9kg in total.
the tracking is horrible - almost unusuable. If I ever reach 20 seconds exposure without horrible oblong stars and tracking errors, then I can be happy. for visual, this has no noticeable negative effect, though!
this is gospel ;)
that's why I suggested you consider the max load of your new mount when choosing a telescope. or at least bear in mind the effect it has.
05-08-2012, 04:05 PM
Thank you muchly.
05-08-2012, 07:27 PM
Firstly, thanks from me also for the information on magnetic south - I also have a question if I can jump on the end of this thread?
I looked up my location and it states: 11 deg 1' East, Declination is Positive, Inclination: -68 deg. Do I need to use all these values or is the Magnetic Declination value required?
So if I use method as Rolls, (a) find magnetic South on my compass, (b) turn left 11 degrees and up 37.5 degrees = SCP for me?
Sorry if this is such a silly question, I'm trying also to get my head around the machanics of setting up a EQ mount in the backyard soon.
05-08-2012, 11:17 PM
Yes, you have your calculations correct.
11 degrees east means you subtract that from 180 degrees (south) and as it says "East" you would point the scope south and then turn it 11 degrees LEFT or east....
The way I do it is with a cheapo compass with a rotating dial which I set the compass to say 169 on the dial and then hold the compass so its pointing south, then line up the scope so it points to the arrow at 169 degrees.
Rolls, as for your altitude setting, if it is a skywatcher mount, DO NOT TRUST THIS SCALE!
I have had 2 Skywatcher mounts and both of them are horribly wrong when it comes to reading the right angle for latitude. My first EQ2 was actually at 52 degrees when the dial showed 33, and the HEQ5 pro i have now is about 10 degrees out also.
THE best way to set your latitude is to use a magnetic digital level on the scope's OTA and set it based on your GPS coordinates read from say an Iphone or other GPS where the scope is currently sitting. Otherwise, a normal protractor works well also.
Dont trust the manufacturer's scale at all, they are probably put on by myopic trainees with no sense of up/down/left/right.....
06-08-2012, 09:36 AM
The Solar Noon method will gte you true South without all the mathematics. Plumbline and check the web. Most of NZ is about 17 mins past the hour or thereabouts. Then jus chuck in your latitude angle with an Inclinometer on your Apple/Android or Bunnings special and you are more than good =for widefield AP.
Oh ! ... and welcome to IIS btw Have fun !!
07-08-2012, 03:33 PM
Howdy there Russ. Nice to see a fellow newbie. After digesting what chris said I had a think and downloaded "bubble" for my android. Because the phone has a flat side and the app reads out degrees very accurately I solved that problem. I then found a compass app which reads out the degrees audibly. So I rest the phone against the side of the mount and slew it around till it sais 159 degrees.magic. I shall do as Brent said next time theres a fine day.In view of that,heres a site that gives the details.
07-08-2012, 09:35 PM
To be clear, this correction is for your location.
If you reside in Perth for example, the m.dec is 1d 45m West.
the following link shows how much the declination changes in Australia... http://www.smithonline.id.au/?Hidden_Pages:Magnetic_Declination_ Maps
08-08-2012, 10:10 AM
Be careful, a lot of phones compasses are thrown out by the metal in your mount.
A shadow at solar noon is a fail-safe way to do it and incredibly accurate.
08-08-2012, 03:22 PM
Thank's Peter. Just as soon as I get some sun I'll do it. I didn't realise how easy it was.
08-08-2012, 05:02 PM
If you want the official word on your magnetic variation go to Geoscience Australia (http://www.ga.gov.au/oracle/geomag/agrfform.jsp). About half way down that page is the link to the declination images as at 2010.0
It calculates for my place:
Magnetic Field Components
D(eclination) = 12.375 deg
I(nclination) = -64.160 deg
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