Setting Circles on a mount - How important?

[JohnJ]

Hi,

I'm yet to have first light, but just been messing around with me HEQ5 mount indoors and getting to know my kit. I've read lots about mount setup/alignment and watch the Astronomy shed videos on YouTube (Great vids!). The guy on there is very particular about using the setting circles accurately before a session. He uses a marker pen permanently indicate 'home position' and uses the setting circles to input the 'Polaris transit information'.

My question is how important is this? Can I not just setup/balance my mount and polar align with Polaris then start my Synscan 2-3 star alignment? OR will I run into problems later in my session if the setting circles aren't correctly calibrated?

Would I be better off getting into the habit of setting my circles properly now?

I should say I intend to start DSO imaging in the near future but at this very early stage I will be just visual until I get to know my capabilities.

Regards.

[ndastgir]

He there,

for visual observations a rough polar alignment should be enough. But what I experienced with my mount was that when the polar alignment was poor then the 3 star alignment failed several times.

as for the set circles, you can forget about them and use a free software called Polar Finder (http://myastroimages.com/Polar_FinderScope_by_Jason_Dale/) as advised by most people. I personally like using the circles. it took me a while to figure out how exactly it needs to set and how it works, but now it takes me seconds to set them and do the polar alignment.

with DSO imaging you need the most accurate polar alignment you can get. I know there is a software out there that assists polar alignment. you should find the details in this forum.

good luck,

Naeim

[JohnJ]

He there,

it took me a while to figure out how exactly it needs to set and how it works, but now it takes me seconds to set them and do the polar alignment.

So if using somthing like Polar Finder software WHY do we use the circles - what are they actaully doing for me?

[JamesF]

For visual use I'd probably not even bother looking through the polar scope. Getting the latitude set correctly and aligning the mount to the north by eye is probably sufficient for most things.

For imaging you would probably want to get the polar alignment roughly correct from the polar scope and then use drift alignment to finish off.

James

[JamesF]

So if using somthing like Polar Finder software WHY do we use the circles - what are they actaully doing for me?

On my EQ3-2 I used them to align the polar scope initially, and then at the start of each imaging session I use them to set the current time and date for aligning the mount to Polaris. I use the mount mostly for planetary and wide field imaging, so a little inaccuracy isn't a big deal.

James

[ndastgir]

So if using somthing like Polar Finder software WHY do we use the circles - what are they actaully doing for me?

the circle and the polar finder software do the same thing: they tell you where on the polarfinder's circle Polaris should be.

with the circles once you adjust them you rotate the mount in RA axis to show the date and time, and then when you look into the polarfinder and you move your mount with the alt/az screws to move the polaris to the small circle on the central circle.

the software shows you where polaris should be and you rotate your mount in RA to that position and then again use the Alt/Az screws etc.

for me it's just that now it is too easy to use the circles that I cannot be bothered to run another small software just to tell me where polaris should be!

(maybe stating the obvious: I do the polar alignment without the OTA and weights, as i guess most of the people do)

[JohnJ]

But don't you still need to run software to get the accurate transit information so that you can configure your setting circles accordingly?

Without running software you won't have the transit info?

[JamesF]

But don't you still need to run software to get the accurate transit information so that you can configure your setting circles accordingly?

Without running software you won't have the transit info?

You don't actually need software To align the Polaris indicator I set the time and date rings to midnight on November 1st. At that time Polaris is at its highest above the northern celestial pole, so as the polar scope inverts the image the Polaris indicator should be at the lowest point below the NCP marker. That is, vertically below it. During the day I point the polar scope at a convenient vertical, get the NCP marker aligned with the vertical and then align the Polaris indicator to be on the same vertical below the NCP marker.

James

[ndastgir]

I use 1st November at midnight as the transit date and then take it from there.

you can find other dates on various websites as well.

[JohnJ]

OK I *think* I'm starting to get it. I guess the above methods you describe are for optimal accuracy. If I wish do to some planetary visual and short exposure DSO imaging (sub 2mins) could I simply not:

- Pop my mount down facing North (ensuring it's level)

- Set the atitude for my mount

- Point my polar scope in the aprox direction of Polaris (as in I can see Polaris through my polar scope)

- 'Tweak my bolts' until Polaris 'moves' into the Polaris indicator target circle

- Done

Is it even necessary to touch my setting circles or look up transit info at all?

Or am I missing something?

[JamesF]

For planetary viewing then the first two steps are probably sufficient. For DSO imaging I think you'll need to do things properly. Even short focal length camera lenses start to show trailing fairly quickly (within a minute, often) if the alignment isn't fairly close.

James

[ndastgir]

Agree with James. with a poor polar alignment the maximum exposure time without noticeable trailing is around 20 seconds. if you are into astrophotography you really need to do a proper polar alignment.

[midnight_sky_watcher]

Most setting circles are to small in circumference to be accurate with the gradients on them, I have EQ6 mount and the circles are large and accuracy is better.

Grant....