Polar Axis Scope Help

[Mav359]

Ive attached a picture of my polar scope and am a little confused....

The instructions for setup state that i need to use the adjustment screws to re-centre the cross hairs once i move the OTA from right to left, however there are two sets of adjustment screws. there are three hex screws spread equally apart around the scope & two flat head screws which were spaced next to each other.

Logic would dictate that "Adjustment Screws" would be normal screws but they don't seem to do anything, the hex screws do but the reticle starts moving about wildly.

Also whats the silver dial for?

Celestrons instructions are a little vauge

[Neil McRae]

The adjustment is made using the hex screws BUT be careful and turn only a maximum of half a turn at a time as if you loosen them too much the reticle can fall out. You do not move left to right but get a target such as a steeple or tv aerial and centre on it in the cross hairs then turn the declination axis 180 deg and if the image has moved use the hex screws to bring the image HALF way back to the original place. Keep repeating this till the centre does not move.

Neil

[steppenwolf]

As Neil said above.

The other screw is for locking that black ring which has a small 'score' mark on it and this is known as the 'Index Ring'.

The silver disk is calibrated in months with each smaller division representing 2 days - this is used with the RA setting circle to calculate the position of the star Polaris at any time/date with a fully calibrated polarscope.

[Mav359]

I am in the process of trying to set this up, the instructions state that i use my alt/azm & altitude bolts to centre an object on the cross hairs with the OTA on the right of the mount (No weights or OTA). Then i rotate the mount on its axis so the saddle is on the left of the mount at which point it should score a semi circle on the reticle which i then adjust the screws to the scored point.

It never scores anything on the reticle, i dont get it, i have figured out how to use the adjustment screws to move the reticle but with no index point its useless.

There is a focus ring ring and all the screws in the original picture, is there anything i can adjust to get this to score the index? or am i doing it wrong?

[steppenwolf]

OK. The first part of calibrating a polarscope is to ensure that the polarscope's reticule is centred in the RA axis.

To do this, you need to remove the telescope from the mount as you just need the bare mount on its tripod with the polarscope installed. Next, you set the RA axis pointing at a fixed object as far away as possible - the top of a church steeple, top of an electricity pylon or something similar. The idea is to align the crosshair on the fixed object, then rotate the RA axis through 180 degrees and note if the crosshair has moved off the distant object. If it has moved, you should adjust the reticule using the three screws around the polarscope's perimeter until you have made up one half of the error. Then rotate the RA axis back another 180 degrees and repeat the adjustment, again only correcting half the error. Repeat again and again until rotating the RA axis has no effect on the crosshair's position on the distant object.

That is the end of part 1 of the polar alignment calibration procedure but until this part is completed, there is no point in moving on to part 2!

[Mav359]

Cheers for the help Steve, i'll try again tomorrow.

[glowjet]

Understanding the setting up and use of the Polar scope can be a little daunting and confusing, the fundamental basic of the scope is to have the central optical axis defined by the cross hairs in the FOV aligned with the rotational central RA axis of your mount, Steve has already set out at length how this is achieved, once completed the use of the scope is well covered in Astro_Baby`s tutorial on Polar aligning. Yellow pages is quite good for finding hair restoring clinics, once you have managed to master the procedure

[Mav359]

LOL I shaved my head after i bought the scope saved on the pain...

I had another go this morning, part of the issue i found is that im quite high up so in order to set up during the day i have to reduce the altitude to near zero and then tilt the tripod forward at which point the whole rig wants to fall forward.

The only thing i have to use is the corner of some railings on the top of a tower block but that god damn ugly monstrosity of a building isnt even 500m away.

That said with some fine tuning the cross hairs start and finish now in the same place but i have noticed that through rotation it moves off centre and comes back. Is that normal?

Also is my block of flats far enough away?

[steppenwolf]

That said with some fine tuning the cross hairs start and finish now in the same place but i have noticed that through rotation it moves off centre and comes back. Is that normal?

Also is my block of flats far enough away?

Unfortunately, you don't have the reticule right yet - it should not waver throughout a full 360 degree turn otherwise it will simply not be calibrated. A little more tweaking to be done .....

500 metres for your corner of the block of flats should be fine.

[themos]

No, I think that when it's properly aligned, anything you put under the crosshairs should stay under the crosshairs as you rotate by any amount.

Now, it may APPEAR that the whole thing (crosshairs and target) wobbles about as you turn the RA axis but they shouldn't SEPARATE.

[MarkSix]

A question about the reticle. If it falls out during doing the adjustment is it critical in what position it is put back?

[themos]

Luckily, no. If you are going to use the dials, you can adjust them to the new orientation of the reticle. At least, that's my understanding.

[Mav359]

Unfortunately, you don't have the reticule right yet - it should not waver throughout a full 360 degree turn otherwise it will simply not be calibrated. A little more tweaking to be done .....

500 metres for your corner of the block of flats should be fine.

I'm not sure my neck & back have much more tweaking left in the but i shall soldier on....

[Mav359]

Could you use Polaris as you're stationary target if aligning at night?

[themos]

Yes, you can use Polaris. It doesn't move that much in a few minutes. But if the process takes too long you may have to retarget it by repointing the RA axis.

[steppenwolf]

Luckily, no. If you are going to use the dials, you can adjust them to the new orientation of the reticle. At least, that's my understanding.

I can confirm that you are right - but I'm too embarrassed to tell you how I know for sure .....

[steppenwolf]

I'm not sure my neck & back have much more tweaking left in the but i shall soldier on....

Soldier on, Alan but hang on to the thought that you only have to do this part once (unless you really prang the mount and you're not going to do that are you?) but it is a vital part of the whole precedure.

[Mav359]

Once i get this right i thing i'll wrap the mount in bubble wrap and cordon it off with police tape... if after this i prang it i may kill myself. My neck was destroyed this morning!!!!

I think I'll wait to have another go tomorrow morning.