My first attempt at aligning polar scope

[AstroEd]

Hi folks I have a Celestron CGEM DX and last night I tried to align my polar scope. Most videos I see says if aligning in day time to pick an object at least 50 feet away, It is VERY cold out so I thought I would try it inside the house on a point on my garage door but it is only 35 feet will this make a huge differance when I point at polaris will it still be aligned? I will add some images of how I was set up to do the alignment and video links of what I did and the end result. Video 1 method used, Sorry for jerkyness of first video was setting up the ipad cam in front of the polar scope.  Video 2 Final results, For some reason my images are rotated in the post.

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[MiguelMJr]

Hello AstroEd,

The further away your alignment target is the better, 50ft. seems a little short to me.

I know it's very cold in Missouri right now but maybe you can pick out a more distant object once it gets warmer. Excellent polar alignment is one of the keys to good astrophotography.

Check out the youtube videos by "Astronomyshed" if you haven't already. There you will find some videos on adjusting the polar scope for correct alignment and many more astronomy based videos.

After you have everything sorted out check into this very inexpensive software that should help in getting you mount very precisely polar aligned.  http://www.alignmaster.de/index.aspx

Hope this helps,

Miguel

[AstroEd]

Love Astronomysheds videos and already bought Alignmaster although I have not used it yet. A bit frustrated with my set up it is too tall for me looking for a shorter mount that can handle a 11" EdgeHD, using a Explore Scientific 80mm triplet f/6 as a guide scope for video observing and future imaging.

[wxsatuser]

I used the tip of a TV antenna that was about 35 feet away.

I did this in the summer with the mount, HEQ5 on the tripod.

When transfered to the obsy pier I checked it again on Polaris and it was nye perfect.

[AstroEd]

Well if it ever warms up I will check it on Polaris.

[jefrs]

You can estimate accuracy with the tangent angle i.e tan = perpendicular / base. (down & dirty)

it we assume the target spot has an apparent 1mm diameter and the distance is A = 10 metres or B = 100 metres

(the target spot cancels so it does not matter what size it is; it is the same both times, we could call it "n")

then

tan(x) = 1/10,000

and

tan(y) = 1/100,000

therefore the angle ratio is

x/y = 10

(we don't really have to go through that lot; it's "show working")

i.e. it is 10 times better to increase the distance by 10 : the accuracy (field of view (FoV) angle) is directly proportional to the distance.

The garage wall test may confirm if your finder is good enough or way off the mark and you need to take it outdoors to calibrate: I can see line of sight clean through our house which is guesstimate six or seven car lengths; probably not enough to calibrate the finder but good enough to check whether it needs resetting.

I would not recommend making any adjustments indoors, you'll only need to re-do them  (I spent many years operating a calibration laboratory).

I'm setting up / playing with a Star Adventurer tonight. Although we're 51°N it's not that cold outside but it is completely overcast: no Polaris yet :-(

[jefrs]

Whilst setting up in the house I found the view bleary and so unscrewed the eyepiece, they had used enough grease to service the wheel bearing on a car and got it all over the graticule disc. So I had to dismantle and wash it clean in iso-propyl alcohol (lens cleaner): there should be just the merest smear of grease on these screws not great blobs. If you ever grease these things then use half as much as you think you need and then divide that by two.

So then I had fun with the 1.5mm Allen key, good job I've got tools because they didn't provide (I'm part engineer). Having used bow-spring compass dividers on the collar to get the graticule in and out it needed basic realignment; it was way out. I've got maybe 30 paces from scope to kitchen. The view is reversed L to R to it was counter-intuitive: tightening a screw pull the graticule towards it but you can only loosen and nip up the other two, and it's back to front; you need point of reference, which way am I moving, a dot in the sky is not good. The torque settings on (any) screws this small is minute; less than my finger-tight. The book advises no more that 1/4 turn on any adjust and I concur. My nominal 30 metres (4 cars parked) seems to be a sufficient distance to do this. I do need to check down the garden and beyond, I've got a telegraph pole about 100 metres away that makes a good aiming sight.

I couldn't  get at Polaris due to heavy rain and solid cloud cover :-(