hey all...
this is a newbie question...
I tried PA with Nexstar 4SE and set the wedge to about 35 degrees... and pointed the tripod towards south in general with the aid of compass app on my iPhone.
I took a picture of the sky with the telescope and uploaded the image to astrometry.net hoping to see that Im close to Octans... but I was nowhere near... I think it was around Triangulum Australe instead.
If I move the tripod to about 170 degrees S... I was closer to Octans
Is this what you would do normally and with the aid of Polemaster/Sharpcap etc you fine tune your mount bolts ?
Or my compass app is wrong ? I have true north setting turned on.
Do you have your iPhone set to point to true north or magnetic north ? You want it set to True North - there's 12 degrees difference in Sydney (Settings / Compass / Use True North)
Make sure the scope is in line with your polar axis.
Tape you phone in place if you don't have a holder but make sure it does not move during the following...point the scope (and the mount actually) at where you think CSP is likely to be...take a photo say every minute or so for as long as you can but at least ten minutes...what you can do by looking at all the images is mark out the circles they are making ...the centre of those circles is the CSP...you then can adjust your mount accordingly...ideally you should be able to take a group of photos that has the centre of the circles in the centre of your photos.
Last night ( because I am trying to find the CSP thru trees) I set my had my pole master camera take a ten minute shot in sharpcap which showed exactly where CSP was and I was able to work out octans with one star hidden by a branch.
Anyways with that photo I adjusted the mount so the centre of the star circle was in the centre of the screen and then went into pole master to nail it perfect..I was amazed how close I was just by doing the ten minute exposure and adjusting using it.
But I did not notice the rest of the sky had clouded over so I did not get any imaging done...but polar is good to go maybe tonight hopefully.
Good luck.
Hope this helps.
Alex
You can use a long exposure on your camera ..better still...either just the camera or thru the scope a long exposure will show the arcs which you centre to get near perfect PA...the mount is off during this process.
Alex
Solar noon shadow stick method , maybe old fashioned and crude but it works and enabled me to find a fairly accurate true south line at both my imaging sites ( permanent line scored in the pavers )
I found solar noon time on Stellarium at both sites when to mark the line , so easy. I did the same thing ( true south line and digital inclinometer) for a friend who has my old 10” push nudge Dob, he usually finds his reference star and then main target in a minute using the Az Alt co ordinates off Stellarium
For SCP I just use a digital inclinometer to set local latitude
At both sites , first alignment Star usually ends up in the FOV , then some minor centering , then Synscan PA routine ( 2 or 3 iterations ) and we are done !!
I started off with one of these scopes so hopefully I can help. You only have to be pretty approximate with your starting setup towards south. Remember that your scope has quite a long focal length for its size at 1350mm so hoping that you’re going to get octans in the field of view manually is probably going to end in frustration. Thankfully your hand controller is there to help. If you get it setup reasonably close to south ( as good as you can with your compass on true south ). Do a 2 star alignment. Then pick one of your two stars you used for alignment and slew to it. Then you’ll find in your menus a thing called align mount. Select that and it will take you through a process where it will move away from the star you had centered and you adjust both the elevation of your wedge and physically move the tripod to bring it back to the star being centered without using the hand controller. If you’re planning on using it for photography then it is recommended you do this every time you setup. However if it’s just for goto accuracy you can mark a point on the elevation rod and 3 marks where your tripod legs go on the surface you have it sitting on and every time you setup you can put it back in the same spot.
Do you have your iPhone set to point to true north or magnetic north ? You want it set to True North - there's 12 degrees difference in Sydney (Settings / Compass / Use True North)
Yes the true north setting is turned on... hence my thinking of the compass app not working as it should be...
Quote:
Originally Posted by xelasnave
Make sure the scope is in line with your polar axis.
Tape you phone in place if you don't have a holder but make sure it does not move during the following...point the scope (and the mount actually) at where you think CSP is likely to be...take a photo say every minute or so for as long as you can but at least ten minutes...what you can do by looking at all the images is mark out the circles they are making ...the centre of those circles is the CSP...you then can adjust your mount accordingly...ideally you should be able to take a group of photos that has the centre of the circles in the centre of your photos.
Last night ( because I am trying to find the CSP thru trees) I set my had my pole master camera take a ten minute shot in sharpcap which showed exactly where CSP was and I was able to work out octans with one star hidden by a branch.
Anyways with that photo I adjusted the mount so the centre of the star circle was in the centre of the screen and then went into pole master to nail it perfect..I was amazed how close I was just by doing the ten minute exposure and adjusting using it.
But I did not notice the rest of the sky had clouded over so I did not get any imaging done...but polar is good to go maybe tonight hopefully.
Good luck.
Hope this helps.
Alex
You can use a long exposure on your camera ..better still...either just the camera or thru the scope a long exposure will show the arcs which you centre to get near perfect PA...the mount is off during this process.
Alex
This is a neat trick
Thanks for this
So you could potentially use this method if octans/CSP is only partially visible ?
Quote:
Originally Posted by Startrek
Solar noon shadow stick method , maybe old fashioned and crude but it works and enabled me to find a fairly accurate true south line at both my imaging sites ( permanent line scored in the pavers )
I found solar noon time on Stellarium at both sites when to mark the line , so easy. I did the same thing ( true south line and digital inclinometer) for a friend who has my old 10” push nudge Dob, he usually finds his reference star and then main target in a minute using the Az Alt co ordinates off Stellarium
For SCP I just use a digital inclinometer to set local latitude
At both sites , first alignment Star usually ends up in the FOV , then some minor centering , then Synscan PA routine ( 2 or 3 iterations ) and we are done !!
I need to google this... solar noon shadow stick method...
thanks
Quote:
Originally Posted by RyanJones
Hi Ed,
I started off with one of these scopes so hopefully I can help. You only have to be pretty approximate with your starting setup towards south. Remember that your scope has quite a long focal length for its size at 1350mm so hoping that you’re going to get octans in the field of view manually is probably going to end in frustration. Thankfully your hand controller is there to help. If you get it setup reasonably close to south ( as good as you can with your compass on true south ). Do a 2 star alignment. Then pick one of your two stars you used for alignment and slew to it. Then you’ll find in your menus a thing called align mount. Select that and it will take you through a process where it will move away from the star you had centered and you adjust both the elevation of your wedge and physically move the tripod to bring it back to the star being centered without using the hand controller. If you’re planning on using it for photography then it is recommended you do this every time you setup. However if it’s just for goto accuracy you can mark a point on the elevation rod and 3 marks where your tripod legs go on the surface you have it sitting on and every time you setup you can put it back in the same spot.
I hope this helps
Ryan
Thanks Ryan.
I assume this can be done with octans/CSP partially visible ?
I am going to try this later tonight...
With this alignment can you get up to 30 secs of exposure without star trailing ?
Quote:
Originally Posted by CalvinKlein
This page might be useful for you to check that you are pointing in the right area.
"The primary aim, and from what I can ascertain the biggest problem especially those new to polar alignment, is to find the four very faint stars that make up the Octans alignment shape found in many polar-scope reticles. "
Yes this is one of my problem... almost all pattern in the southern part of sky look like trapezium to me
This is a neat trick
Thanks for this
So you could potentially use this method if octans/CSP is only partially visible ?
Well I did the night before last.
Once upon a time that is how I did polar alignment all the time using a DSLR camera thru the scope..the thing is if you want to be perfect is during the day take a photo thru the scope and look thru your polar scope to make sure both are pointing at the same spot.
Today I am trying to process some M33 from last night..the mount as I said required minimal agjustment when I went to pole master. The adjustment was only about 1/4 of an inch on the 75% pole master screen...lining up the two units a little circle and little square required only a squeeze of the adjustment knobs ...anyways last night did unguided one minute subs that look pretty good.
The deal is...set up set your time exposure and take break have a cuppa and see the result when your are finished...if you want to be exact tape a spot marking the centre of your screen..I just guess...so maybe with a spot my ruff alignment may have been better.
And you could have your mount pointing East or West and it becomes clear which way you need to go..I have given up on using a compass both conventional and the ones one the phone...the noon day stick in the sand is good but why bother when a time exposure tells you what you need to know.
Good luck.
Alex
Finding Celestial True South using Solar Noon Meridian method
Items needed
1 metre length of 12mm timber dowel with a 2mm deep 90 deg cross cut into one end using a hacksaw
2 x 3 metre pieces of 1mm string cotton type
4 x weights like a brick or paver etc...
1 x straight edge, alum angle or ruler 500mm long would be good
1 x fine point black permanent marker
1 x 300mm long Stanley or quality boat type builders bubble level
1 x PC with a planetarium software program. Stellarium is a good choice as it’s free and easy to use
1 x Smartphone like an iPhone
Location
Your observing location ( approximately 1.5 sqm ) or where you will set up your telescope mount should be a reasonably flat and level area with a good view of the sun at around midday ( a paved , tiled or concrete area is preferable) At a remote site you will need to clear the ground and make it reasonably flat or level
Procedure
(Setting up for your Shadow)
Erect timber dowel vertically below your preferred observing tripod position and use the 2 strings to anchors the dowel like tent guy ropes at NSEW using weights to hold it in position. Use your bubble level to ensure dowel is exactly vertical at 90 deg in all directions ( very important ) The hacksaw cuts at the top of the dowel make it easy to adjust the dowel NSEW
Finding Solar Noon Time
(Using your Planetarium like Stellarium )
Start your PC mid morning and open Stellarium. Rotate your cardinal point to the North position and raise view up until you see the Sun
Click on the Sun and then click on the clock , move the time forward or backward to the point where the Suns Alt/Az degrees goes from 359 deg to 0 deg or exactly bisecting the North South meridian line ( refer to top left hand data on screen for Az/ Alt deg )
Record this exact time which is Solar Noon ( eg 12.35pm )
(Finding Solar Noon on a Website)
Most meteorological websites show Solar Noon times at or near your observing location
Marking your Celestial True South Line
Go to your observing location 10 minutes before Solar noon with your smartphone , ruler and permanent marker. The dowel should be casting a 12mm wide +500mm long shadow on the surface towards the south
At exactly Solar Noon time mark a thin line on the surface or ground from the base of the dowel outwards along the exact centre of the shadow for at least 500mm ( be as precise as you can )
This line is marks the Celestial Meridian (True North / South )
Use this line to align your tripod front leg to True South and then set up your mount
I found this method far more accurate than any app or compass with magnetic declination
"The primary aim, and from what I can ascertain the biggest problem especially those new to polar alignment, is to find the four very faint stars that make up the Octans alignment shape found in many polar-scope reticles. "
Yes this is one of my problem... almost all pattern in the southern part of sky look like trapezium to me
Is this your website ?
Yep - it sure is. I use the technique every time I go out with either of my mounts.
"The primary aim, and from what I can ascertain the biggest problem especially those new to polar alignment, is to find the four very faint stars that make up the Octans alignment shape found in many polar-scope reticles. "
Yes this is one of my problem... almost all pattern in the southern part of sky look like trapezium to me
Is this your website ?
Just trying to help Ed but I’m not sure that everyone is considering what Octans looks like through a 4” F/13 MAK CAS. I’ll tell you from experience with your exact telescope, it’s not easy. I chimed in before and mentioned that your hand controller will guide you through polar alignment on the wedge. If you’re not experienced and don’t know the night sky all that well as most new people are. Use your hand controller, let it help you find SCP and polar align then have a look though your eye prices and see what you really can see.
Just trying to help Ed but I’m not sure that everyone is considering what Octans looks like through a 4” F/13 MAK CAS. I’ll tell you from experience with your exact telescope, it’s not easy. I chimed in before and mentioned that your hand controller will guide you through polar alignment on the wedge. If you’re not experienced and don’t know the night sky all that well as most new people are. Use your hand controller, let it help you find SCP and polar align then have a look though your eye prices and see what you really can see.
You are right Ryan - poor assumption personally on my part assuming that some sort of separate finderscope was being used for the alignment.
I see the 4SE has a red dot finder - I cant help but wonder if it was replaced with a cheap 50mm finderscope pre-aligned with the 4SE would be a useful addition and help with finding the SCP (and would probably help a lot finding the 3 alignment stars).
Yes the true north setting is turned on... hence my thinking of the compass app not working as it should be...
On older iphones the compass app was great, but the newer ones have an inbuilt magnetometer which is affected by all magnetic sources. I have to take my phone out of its case, which has a magnet in it to keep it closed, before I can get any sort of accuracy with it, even then it seems to be a few degrees out when using the SkySafari app.
Rick
Yep . Every sympathy with trying to see octans in a polar scope or at all really. There are lot of nearby star patterns which look very similar and then a lot of light pollution.
Getting an approximation by day would help I agree. If you do not have a GPS compass which is the only almost reliable device at night and an inclinometer accurate to within 0.2 degrees.
You can also check your boundary survey for the magnetic North point and go 12.5 degrees west of that for True North
I use a polar clock utility to remember which way up octans is on any night as you appreciate it spins around the SC pole.
Quote:
Originally Posted by RyanJones
Just trying to help Ed but I’m not sure that everyone is considering what Octans looks like through a 4” F/13 MAK CAS. I’ll tell you from experience with your exact telescope, it’s not easy. I chimed in before and mentioned that your hand controller will guide you through polar alignment on the wedge. If you’re not experienced and don’t know the night sky all that well as most new people are. Use your hand controller, let it help you find SCP and polar align then have a look though your eye prices and see what you really can see.
On the cork-board at my work-desk I have a few cheat-sheets - the phonetic alphabet (handy for spelling out words to people on the phone), apple mac shortcut keys etc ...) - one I've had up there for a few years is a printout of the SCP region.
It was very handy to refer to when I started out with my DIY equatorial mount and helped me to remember the location of the SCP relative to the distinctive Apus and Chameleon constellations.
I find the iPhone True North is accurate but you need to ensure you have calibrated it using the method instructed on the phone.
You should ensure you are not near magnetic objects (including iron) whilst calbrating and measuring it.
I am having the same issue, but slightly different.
The true north vs magnetic north for the compass is a rookie mistake that I wish that I didnt have to admit, but that might be my issue.
I tried for about 4 hours last night to get a polar alignment on my HEQ5 Pro. I set the (whatever you call it, go easy Im new, tilt, wedge) latitude to where I am located and pointed where I thought was due south and wherever I tried, there was absolutely no stars or only one in the polar alignment scope.
Im at the top of the Blue Mountains, so light pollution isnt really a thing for me, but there was a moon last night.......
Ill give it another go tonight if the smoke goes away, using true north on the compass.
Another issue I guess, is that I set the HEQ5 Pro to 33.36 deg via the dial on the side of the mount, but then checked it with phone inclinometer, and it was about 5 degrees out.
Is that possible that the mount is out, or would it be the phone?
I really didnt vaguely think that I would have this much trouble.
Just set your tripod up with the leg that has the N [North] on it pointing
approximately South, and the latitude adjustment set to your location [as you did],as Ryan said, use the polar alignment routine
in the hand controller.
raymo
Last edited by raymo; 08-12-2019 at 02:34 PM.
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