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Old 16-05-2020, 09:22 AM
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xa-coupe (Jeff)
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South Celestial Pole and General Whinge

First post..yay me.


Dipped my toe into astro during the lockdown, pretty competent with a camera yet I'm going nowhere fast. I have graduated from a 70-200 lens (canon gear) and a portable rotator type mount (Polarie brand... it sucks but it's borrowed) from which I get reasonable pictures to a Saxon 900mm focal length telescope and it is all going haywire.


I have always struggled with getting my polar alignment right, even with the 'shorter' focal length but 200mm is a bit more forgiving than 900mm. I have to use the telescope as a big lens because during the day I can use the various gadgets to connect the camera to an eyepiece but at night, I get blackness no matter what I do. That's another problem for another day.



As for setting the mount to south, I am using an EQ2 mount (with motor attachment), but I align the main body of the mount to south ( using an Iphone compass) and dial up the degrees until I reach roughly the latitude (37 and a bit degrees) It still trails a little bit at any exposure than can produce a semi useful picture, even at 12500 iso to reduce the exposure to a minimum. Everyone seems to have a way for setting their celestial pole but I can't get it right.



Being in Melbourne I get a shortish period where there's no cloud so I am trying to get this sorted so I have something to show for all my effort.


I've attached a moon pic to prove I am not a complete loser with a camera, only a partially complete loser!
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Old 16-05-2020, 09:34 AM
RyanJones
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Hi Jeff,

If you are using a compass to find magnetic south you are a little bit off. You need to be aligning to true south which for you is about 11deg east of magnetic south. Hope this helps.

Cheers

Ryan
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Old 16-05-2020, 10:02 AM
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xelasnave
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Welcome Jeff.
Your Moon image is most decent, you have no burn out spots and even seasoned veterans still will burn out spots.

Now no one gives me credit for this approach but I promise it will get you very close to a near perfect PA.
You can use you camera and your 70/200 lens or the camera thru the scope..personally I would start with the shortest focal length and gradually increase it as you center things according to my method.
First during the day set up the camera on the mount so that what you see thru your polar scope is what you see thru your camera. If no polar scope align the camera as best you can with the polar axis...now when dark point your gear to where you think is South..without turning on your mount..in others words..NO TRACKING..at this point...take a time exposure of five minutes or more and look at the result...you will see the stars making semi circles...the center of these semi circles is your CSP...you just keep adjusting the mount until the CSP or the center of your circles is in the middle of your screen on the camera.
I did it this way for years and sometimes could run very long unguided exposures...
When you have it as good as you can get switch the mount on and take a short exposure of a star, say 15 seconds, see if it's round, then 20 seconds and keep going until you notice trailing...now if you can only get 15 seconds start taking photos at 15 seconds..and as high an ISO as possible, actually higher than you feel good at...take 200 subs or more ..the fact the mount is a little off and the high number of subs will help with noise reduction.
Read up on drift alignment so perhaps you can make small adjustments..problems East West will almost be due to balance so make sure you adjust balance until East West is the best you can get before you adjust alt or as.
Others will also bring you up to date with software but my idea is so you can get things close and have the software work.
I now use pole master but so often I have to get things close using my method to find sigma.o and interestingly one night having centered things via my method running pole master showed that I lucked in and was spot on.
The key is to accept whatever crook PA you get and take photos..if you only get 10 seconds go for it...longer exposures may be a way off but that no reason not to start capturing..and for starters try high ISO and learn how to manage noise...You won't believe this but recently I ran 25600 ISO on a wide field and sure it could be better but it was way way better than I expected at such a high ISO...and with your long fl you may just need to go against some of your ideas about ISO.
I am about getting a good result with what I have at hand right now...
Good luck just hurry up and post something.
Alex

Good luck
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Old 16-05-2020, 10:16 AM
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jayconnor (Jay)
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Jeff where in Melbourne are you located?
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Old 16-05-2020, 11:41 AM
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Originally Posted by jayconnor View Post
Jeff where in Melbourne are you located?

Thanks guys ...


I live bayside suburbs.
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Old 16-05-2020, 07:50 PM
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xa-coupe (Jeff)
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I have to thank you all, particularly ryanjones for his hint about celestial south.


Attached is a pic of M42 which has no particular merit (it was taken from a single jpg) other than it was a 30 seconds exposure. It's far from perfect but it is a quantum leap from where I was yesterday.


again, thank you
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Old 17-05-2020, 11:05 AM
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Quote:
Originally Posted by xa-coupe View Post
I have to thank you all, particularly ryanjones for his hint about celestial south.


Attached is a pic of M42 which has no particular merit (it was taken from a single jpg) other than it was a 30 seconds exposure. It's far from perfect but it is a quantum leap from where I was yesterday.


again, thank you
You are pretty close to a pa. Next step download Deep Sky Stacker. it's free.. and stack a few.. probably back off to 20 seconds.
Great job.
Alex
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Old 17-05-2020, 12:59 PM
Startrek (Martin)
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How to find true south the good reliable old way using the Sun

I set up my EQ6-R Mount and 8 f5 newt last night on my true south line to image the Bubble galaxy and only needed to tweak the Az bolt a tiny little bit ( Alt was spot on ) and polar aligned in 5 mins. My permanent true south line scored on the ground is really accurate , never lets me down , better than any app or compass !!!!

Finding Celestial True South using Solar noon ( Shadow ) method
Items needed
1 length of 12mm diameter timber dowel or rod with a 2mm deep hacksaw cut 90 degree criss cross on one end
2 x 3m pieces of 1mm diameter cotton builders string or similar
4 house bricks or pavers or weights
1 x straight edge , ruler or aluminium angle about 500 or 600mm long
1 x fine point permanent marker
1 x Stanley or similar 350mm builders bubble level
1 x PC or laptop with Stellarium down loaded or Smart phone

Location
Your observing location ( approx 2m2 ) or where you will set up your telescope mount should be a reasonably flat or level area with a good view of the sun around midday ( a paved, tiled or concrete ground is preferable) At a remote site you will have to clear the ground of rocks and debris to leave a fairly clear flat area

Procedure
Setting up for your solar noon shadow
Erect timber dowel or rod vertically at your telescope mount location and use the 2 strings to anchor the dowel to the ground like tent guy ropes at north , south , east and west. Use bricks , pavers or weights to hold down the strings tight so dowel sits firm upright. Now use a bubble level vertically against the dowel to ensure it is 90 degrees on all 4 sides N,S,E, W, The hacksaw cuts in the top of the dowel make it easy to make fine adjustments
either way

Finding Solar Noon Time

(Using a Planetarium like Stellarium )
Start your PC or laptop in the morning and open Stellarium
Move your planetarium view to the left or right until you reach the north (N) cardinal point and move up until you see the Sun
Click on the Sun and you will see its read out data on the top left of the screen
Now open the Time window and move the time forward until you view the Sun bisecting the north meridian line or until read out data on Az/ Alt degrees goes from 359 degrees to 0 degrees
At that very point and time , record the time from the clock ( eg 12.35pm )This time is your Solar noon time which you will use later

(Finding Solar noon on a website )
Most meteorological websites show solar noon times at or near your location

Marking your Celestial True South Line
Go to your location about 15 minutes before the designated solar noon time with your smart phone , ruler or straight edge and permanent fine tip marker
The timber dowel or rod should be casting a 500mm long thin shadow across the ground towards the south
At exactly solar noon time , mark a line on the ground from the centre base or the timber dowel or rod outward along the exact centre of the shadow to at least 500mm out. Use your ruler or straight edge and be as precise as you can.The more precise you are , the closer you will be to true south and eventually polar alignment.
This line represents the True South line and can now be used again and again when you set up your tripod , mount and telescope
I found the above method of finding True South far more accurate than any compass with magnetic declination or phone app etc....

Hope the above is helpful
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