Using the Polemaster with the Fornax Lightrack II

[rareynolds]

As someone who is considering buying a Light Track 2, is the polar scope that is sold with it not accurate enough? What is the periodic error with it as compared to the PM, or give me some indication of the difference in accuracy.

how do you define accuracy? the polar scope is accurate enough to have like a 90% chance to get 5 min and more with 135mm, not 6 min with 400mm. with the PM you gain reliabillty depending on your exp.time and focal length. PE? It is neglectable, around 1 arcsec. see the fred about it

 

[elgol20]

As someone who is considering buying a Light Track 2, is the polar scope that is sold with it not accurate enough? What is the periodic error with it as compared to the PM, or give me some indication of the difference in accuracy.

how do you define accuracy? the polar scope is accurate enough to have like a 90% chance to get 5 min and more with 135mm, not 6 min with 400mm. with the PM you gain reliabillty depending on your exp.time and focal length. PE? It is neglectable, around 1 arcsec. see the fred about it

Stefan, I bought the Lightrack II and Polemaster and have been using it for the past three nights. I am curious which wedge you use to achieve such a fine alignment? I have a Manfrotto 405 geared head which I thought had very fine movements but I have great difficulty getting the green cross to align with the red circle. The best I've done so far is around 1 minute at 300 mm.

I have this one, bought it i an package. Put up to 18kg on top (in the pic below), but had two securityscrews beneath. The trick is to find the right amount of loosening or tightening the adjustmentscrews. too tight makes it difficult to finetune in height. I was afraid that the load could drop, so the extra screws, as can be seen here:





secure 1 min with 300mm is pretty good. 3 to 6 should be possible

--
Best regards
_____
Stefan

 

[rareynolds]

As someone who is considering buying a Light Track 2, is the polar scope that is sold with it not accurate enough? What is the periodic error with it as compared to the PM, or give me some indication of the difference in accuracy.

how do you define accuracy? the polar scope is accurate enough to have like a 90% chance to get 5 min and more with 135mm, not 6 min with 400mm. with the PM you gain reliabillty depending on your exp.time and focal length. PE? It is neglectable, around 1 arcsec. see the fred about it

Stefan, I bought the Lightrack II and Polemaster and have been using it for the past three nights. I am curious which wedge you use to achieve such a fine alignment? I have a Manfrotto 405 geared head which I thought had very fine movements but I have great difficulty getting the green cross to align with the red circle. The best I've done so far is around 1 minute at 300 mm.

I have this one, bought it i an package. Put up to 18kg on top (in the pic below), but had two securityscrews beneath. The trick is to find the right amount of loosening or tightening the adjustmentscrews. too tight makes it difficult to finetune in height. I was afraid that the load could drop, so the extra screws, as can be seen here:



secure 1 min with 300mm is pretty good. 3 to 6 should be possible

--
Best regards
_____
Stefan

So you're using a standard wedge to achieve that kind of precision that Polemaster requires. It looks like you have an Ercole Mini. What is the counterweight assembly you're using there?

 

[elgol20]

As someone who is considering buying a Light Track 2, is the polar scope that is sold with it not accurate enough? What is the periodic error with it as compared to the PM, or give me some indication of the difference in accuracy.

how do you define accuracy? the polar scope is accurate enough to have like a 90% chance to get 5 min and more with 135mm, not 6 min with 400mm. with the PM you gain reliabillty depending on your exp.time and focal length. PE? It is neglectable, around 1 arcsec. see the fred about it

Stefan, I bought the Lightrack II and Polemaster and have been using it for the past three nights. I am curious which wedge you use to achieve such a fine alignment? I have a Manfrotto 405 geared head which I thought had very fine movements but I have great difficulty getting the green cross to align with the red circle. The best I've done so far is around 1 minute at 300 mm.

I have this one, bought it i an package. Put up to 18kg on top (in the pic below), but had two securityscrews beneath. The trick is to find the right amount of loosening or tightening the adjustmentscrews. too tight makes it difficult to finetune in height. I was afraid that the load could drop, so the extra screws, as can be seen here:

secure 1 min with 300mm is pretty good. 3 to 6 should be possible

So you're using a standard wedge to achieve that kind of precision that Polemaster requires. It looks like you have an Ercole Mini. What is the counterweight assembly you're using there?

guess skywatcher. 2 4kg counterwheights with selfmade alu plate
--
Best regards
___
Stefan

 

[rareynolds]

Thanks for the info!

 

[archaeo]

I've been referring back to this thread for some time, as I waited for my fornax LT2 to arrive. I am about to order the polemaster as well, as it seems it will allow the mount's claimed low PE to be best utilized through a very accurate polar alignment.

I have a quick question that I just want to be sure about, which has to do with the off axis polar arm that the LT2 uses: Does the polemaster compensate for the (imagined or real) error that might occur by mounting the polemaster on that pivoting arm? I'd hate to go through the collimation process like I do when I use the reticle polar scope.

I've seen that there is an adaptor out there that allows one to mount the polemaster directly onto the center rotational axis screw where the ballhead eventually screws on, but that would mean that I would have to polar align and then remove the Polemaster and replace with the ballhead and camera/lens. And, as mentioned earlier, this could possibly introduce some flex onto the tripod mount, throwing off the accuracy.

I guess my bottom line question is whether the best way to proceed is to mount the polemaster in the fornax's pivoting arm mount while fully loaded with camera gear, or use the center axis adaptor to place the polemaster directly on the RA, then add the gear after achieving polar alignment?

Thanks for any help, it may be a simple question but I am a newbie to this area.

D

 

[Pogo65]

You do not have to algn it precisely with the mount's axis. The polemaster compensates for it. However if the polar arm does not rotate exactly on the mounts axis, your accuracy suffers.

 

[1llusive]

You do not have to algn it precisely with the mount's axis. The polemaster compensates for it. However if the polar arm does not rotate exactly on the mounts axis, your accuracy suffers.

Right, it is accounted for in the rotations you make during setup.

You should use the PM with the mount fully loaded. This can be tricky but is the only way to account for flex.

 

[archaeo]

Thank you pogo65 & 1llusive !

 

[starman1969]

I bought the Polemaster for my Astrotrac back in 2017 but I really struggled to set it up and eventually sold it lock stock with my Astrotrac and telescope.

It was during rotating the polar arm where it all went wrong for me. As soon as I moved anything, the cross hairs went all over the place and I just could not get them to go in the green box. Maybe it was the flexure in the geared head I was using that was causing all the problems. I did eventually purchase the Astrotrac TW3100 wedge (see image), but my goodness that contraption was difficult to use. Although the wedge was more solid than the geared tripod head I used before, it was far too complex to get precise alignment using it compared with the simple two knobs adjustment on the geared head. I get the feeling that if I used the Polemaster today with my NEQ6 I think I could make it work.







--
Steve

 

[ChildInTime]

Hi all,

Last night I did a little experiment. Instead of using the polar scope arm of the mount, I used some good double sided tape to stick the pole master, to the tracking arm of the mount right above the red logo. It sat nice and stable. I then put the mount in it’s most western position and iso of two movements of 30 degrees I used only 15 due to the mounts limitations. The software had no problem plotting a perfect circle and alignment worked like a dream. I left a polar finder in at the usual place and was able to calibrate it really well while using the pole master. This way you are also sure to use the actual axis of rotation. Another advantage was that I could keep it running while pointing the camera and could fine tune the alignment once it was.

cheers,

Peter

Hello,

Can you please tell us if you found this method reliable and it's worth using instead of putting the PM on the pivoting arm?

Has anyone else tried this method?

Thank you.

 

[Pogo65]

Hi all,

Last night I did a little experiment. Instead of using the polar scope arm of the mount, I used some good double sided tape to stick the pole master, to the tracking arm of the mount right above the red logo. It sat nice and stable. I then put the mount in it’s most western position and iso of two movements of 30 degrees I used only 15 due to the mounts limitations. The software had no problem plotting a perfect circle and alignment worked like a dream. I left a polar finder in at the usual place and was able to calibrate it really well while using the pole master. This way you are also sure to use the actual axis of rotation. Another advantage was that I could keep it running while pointing the camera and could fine tune the alignment once it was.

cheers,

Peter

Hello,

Can you please tell us if you found this method reliable and it's worth using instead of putting the PM on the pivoting arm?

Has anyone else tried this method?

Thank you.

Yes I find it more reliable, as my polar arm has a bit of play, so there is no way to tell if it rotates exactly parallel with the tracking axis. Sorry for my late response.