Polar Alignment using Polar scope

[Barrykgerdes]

That camera idea is worth investigating (and investing in). Once correctly set on your polar axis (telescope) it should make centering quite easy. The polar scope on my G11 was salvaged from another mount (EQ3) and is pretty usless for Bert's reasons (and Polaris graticle). However I think I could build one using camera with a home made "telescope". I must look into it. It might be a worthwhile project.

Baz

[avandonk]

Barry all the EQ range have a north hemisphere graticule as well as south hemisphere. The image is from the GstarEx site and has a field of ten? degrees.

What I would do is accurately drift align the mount and then note the position of the SCP in the GstarEX or other video camera. You could also then align the polar scope very accurately.

When out in the dark sky sites setting up should be trivial.

Bert

[strongmanmike (Michael)]

Originally Posted by avandonk

If I was out in the wilds I would use this for a quick setup. You can attach it to a small monitor from Jcar that people use for reverse view in their car.

Not cheap but a lot easier for us old blokes than waiting for dark adaption and cricking your neck.

http://www.myastroshop.com.au/produc...p?id=MAS-071M2

Bert

Excellent idea there Bert ...polar aligning ease for sure!

Mike

[Barrykgerdes]

Hi Bert

The polar scope I have only has a north graticle. It came out of a mount that only looked like an EQ3. I had hoped it was like the one in your picture but alas it is not. I adapted it to the G11 just to see if it could be adapted but using it as you say is a "pain in the neck"

Your method of alignment is the method I would use.

Barry

[coldlegs (Stephen)]

Does anyone have any long exposure pictures of the scp (at park) after accurately drift aligning? I would be interested to see the different field of views of the different scopes.
Stephen

[Barrykgerdes]

Originally Posted by coldlegs

Does anyone have any long exposure pictures of the scp (at park) after accurately drift aligning? I would be interested to see the different field of views of the different scopes.
Stephen

This can be synthesised very easily with stellarium.
Use the ocular plugin.

Set the telescope and eyepiece paramaters to suit your scope and eyepiece. (don't forget the X,Y settings if the image is on a newtonian.

To give calibration rings use the equatorial grid display.

Centre the display on the SCP .
Select the SCP and then ocular.

The display will show a view window of what the SCP will look like with that particular telescope set up.

If there are too many stars go to the main menu (F4) and reduce the absolute magnitude so only the brighter stars show.

By the way, the meade telescope at park will not park on the SCP. They will park at AZM 0 and Alt 0

The sample views are for an 80mm refractor, 500mm Focal length and 26mm plossl eyepiece (52deg FOV)

Barry

This particular configuration has a FOV of almost 3 degrees
Note that Sigma Octans is visible in the lower right. Time about 4M 17-5-2011

view as seen............. view with 1deg ring.............. view with star names

[mithrandir (Andrew)]

Originally Posted by Barrykgerdes

If there are too many stars go to the main menu (F4) and reduce the absolute magnitude so only the brighter stars show.

Barry is there any way to get Stellarium to display the SAO catalog numbers? It's a pain to convert HIP to SAO for use in my Gemini.

Andrew

[Barrykgerdes]

Not at the moment Andrew

One day we hope to have an assortment of star catalogues that can be used. I am sure there will be one somewhere that uses SAO numbers.

Barry

[coldlegs (Stephen)]

Barry
I'm talking about real images from something like an F10 scope looking through suburban light pollution. I did one last night which I think showed I was close but no prize.
Stephen

[Barrykgerdes]

It's a big at hard to know what you are pointing at with only two stars and no details of the focal length, camera or date/time but I doubt if that is anywhere closer to the SCP than 1 degree.

If that star is Sigma Octans the SCP would be in the direction you have indicated but about 50% further from the star than you have shown

Barry

[coldlegs (Stephen)]

Barry
The field of view is about 10 arc minutes, the scope is an F10 SCT with a toucam at prime.
Stephen

[Barrykgerdes]

Hi Stephen

If the FOV is only 10 arc minutes identifying the stars will be almost inpossible. You will need at least 30 arc mins FOV to get a recognizable view and that star in your picture is hardly likely to be Sigma Octans.

To calculate the FOV I need the focal length of the telescope F10 gives nothing about focal length just the ratio of the aperture to the focal length. I need one or the other to find the focal length.

With the tucam I need the chip size to calculate its FOV when coupled to the telescope. However at a guess I would expect from my experience the FOV would be about 1/4 of what I see using a 26 mm eyepiece and you would get about 9 arc minutes FOV if it was couple to an 8" SCT of the Meade or Celestron size.

Barry

[coldlegs (Stephen)]

Barry
The focal length is 2500mm and the chip size is 4.6mm X 3.97mm.
I'm fairly sure the field of view is somewhere around 9-11 arc minutes
but just wanted to verify the view from a real picture as well as stellarium.
I think there are two maybe three stars in the view..1-easy to see..2-dim...3 very furry and very dim but this maybe an effect of light pollution. Still it would be good to see someone else view of the scp, maybe from a dark location.
Stephen

[Paul Haese]

Legendary stuff Mike. With the EM400 I never got to use the polar scope because of the sky being blocked by the observatory walls and roof. I did note though that the view was a little hard to get right with lighting. Always have respect for anyone that can get polar scopes to work.

[Barrykgerdes]

Originally Posted by avandonk

If I was out in the wilds I would use this for a quick setup. You can attach it to a small monitor from Jcar that people use for reverse view in their car.

Not cheap but a lot easier for us old blokes than waiting for dark adaption and cricking your neck.

http://www.myastroshop.com.au/produc...p?id=MAS-071M2

Bert

Hi Bert

I ordered from your description but that is only the bracket. The camera costs another $500 odd. However I have adapted a webcam ($40) to fit the bracket that might just be sensitive enough to work and is USB compatable.

I will test it sometime



Barry

[steve000 (Steve)]

I took this pic may 9 2010 from mums place, I have marked the near approximate location of the SCP

I often find it easier to locate things on an actual image rather than a star map.

the red dot inside the circle

[Barrykgerdes]

That's pretty close. You are about 3 or 4 arc mins out. The pole is, reference to your picture about 3 or 4 pixels up and to the left.

Look at the star just above your marker. Move about 1/4 of that distance up and to the left.

Barry

[Barrykgerdes]

Originally Posted by Barrykgerdes

Hi Bert

I ordered from your description but that is only the bracket. The camera costs another $500 odd. However I have adapted a webcam ($40) to fit the bracket that might just be sensitive enough to work and is USB compatable.

I will test it sometime



Barry

Here is Polar Scope Mk2.
I re-boxed the Web cam and made a new mounting bracket.

[RobF (Rob)]

Another way of doing this of course is turn on the crosshairs in your camera software and use the finder or main scope cameras.

I've always worried my scope mounting wasn't totally orthogonal with the mount, so recently I drift aligned my heart out in alt and az then tweaked the mounting assembly best I could to get close to the SCP.

Anyway, I've also attached some guider (SSAG) and CCD (QHY9) pics respectively for those interested. My FOV for the finder is about 2.5 degrees and the CCD about 1 degree. Hope these are of some use. Obviously you have to make sure your finder is very well centred on the CCD field (I used a bright star to do this). My finder in normally at PA180 (upside down versus the CCD when that is set up for N/S East/W i.e. PA 0 degrees).

p.s. I didn't say I was perfectly aligned here either for you perfectionists, but Maxim hardly even nudges my dec with this sort of alignment, so its not too far off.

Actually I'm getting the best Polar alignment I've even had by pigging-backing some home made VB.NET off Maxim that monitors the average subpixel drift with tracking turned off and converts it to an arcmins value. I find with just 20-30secs of drift data I can get a pretty good indication or where I am for iterative adjustments. The monitoring time is left to increase of course the closer I get to the pole. Program also converts arcmins into "standard skywatcher azimuth knob turns" which is now an internationally metrologically sound unit for expressing PA error at my house......

[Astroman (Andrew Wall)]

I will most likely try mod the webcam idea also, I thought about doing this from this youtube video http://www.youtube.com/user/astronom...24/5L6IvfievRE

I will most likely drift align to get it closer to perfect though.