Polarscope Reticle - is accurate alignment possible with this type?

[Notty]

Hi, I'm slowly putting together a portable imaging setup based around DSLR and Lightrack II mount etc, but I've had a bit of a to and fro over the polar scope, because the one I got first wasn't illuminated, but the one I have now (Lacerta) has a reticle I'm not used to, and looks like it relies of a very rough estimation orientation based on visual parallax with dub/merak etc.  I'm not used to this kind of reticle, I'm used to a more precise finely graduated circle which makes it easy to replicate the hour angle supplied by most apps.

So can anyone tell me, is there a clever way of using this kind of reticle to get precise enough PA for imaging, or is this type only any good for visual?  Note I can't use the EQmod tools because this mount doesn't support it :-(

 

[DAVE AMENDALL]

The recticle is the same as the current polarscope supplied with the Skywatcher EQ6 mount. There is a PDF that can be downloaded "Using the polar scope for EQ6" Acuracy between 2-3 arc minutes is about the best you will get.......Dave

[Notty]

Thanks Dave, it looks to me like this reticule is good enough for visual but nor precise enough for AP, especially as I'll be viewing head down through a diagonal so won't have the peripheral vision to line up on...

[DAVE AMENDALL]

Hello Notty,  Attatched is the recticle design on the new polar scope supplied with my NEQ6 pro which was rather different to the older EQ5 which showed polar star patterns. This new one seems acurate enough for imaging, although i have not tried exposures over 2 mins.........................Dave

[billyharris72]

I think it all depends on the kind of imaging you want to do (focal length, pixel size, exposure time etc). If it's a DSLR and a 35mm lens for 30 seconds then it's over-speced if anything. If its 10 minutes with a C14 then no reticule is going to be good enough and you will have to drift align.

Overall, though, provided the reticule etching is precise, this should be able to get you a pretty accurate alignment that is good enough for short exposure AP, provided you use the setting circles to accurately align the RA axis (i.e. align the reticle as it would be at the culmination of Polaris and then set the RA circle to the correct culmination time, then adjust to current time in the field).

Billy.