RA Setting Circle

[AlexF]

Just got my Omni XLT 150 today (w00t).Perhaps I'm missing the point, but why doesn't the RA setting circle move with the telescope?

For starters, I'm COMPLETELY NEW to an equatorial mount, and this is my first big boy telescope. I'm going over the manual and saw the instructions for aligning the setting circle. After I'm done reading it, it seems to be pointless. You find a known star/object, dial it in, and then what? After you lock it, it doesn't move. If you don't lock it, you risk turning it without turning the telescope and throwing off the alignment. Yes?

Feel free to call me an idiot. I just want to understand!

[John]

Someone will explain this shortly I'm sure (I don't use an equatorial mount so I can't help I'm afraid). What I do know though is that most folks don't use setting circles to find objects so knowing all about them is not essential to being able to use the scope.

Looks like a clear sky here so I hope you get 1st light on your scope tonight

John

[blinkity-blonk]

I have the same problem, I've not been able to understand my instructions properly so I've given up for now. lol

If someone could explain it, it'd be nice.

[hoobz]

same problem with my skywatcher 150PL circles, i tend to use them unlocked alex, not fully - but not tight if that makes sense. work a treat like that to be fair

what scope u got blonk?? an what's confusing yer? may be able to help yer as i've just got me head round mine. I'm a n00b an all. lol. but i'll give it a shot.

[blinkity-blonk]

Thanks Hoobz, I've got a 4" Helios refractor on an EQ5 mount. I'm pretty much confused by all my setting circle instructions, well I can understand what each circle/scale does but when it comes to making them work I get confused.

There's no instructions on what the Dec dial does, I assume its similar to the R.A dials, but really I've no idea. I need a step by step set of instructions really. If you've just got your head round yours, explaining it to me should benefit both of us

[milan]

LOL, were all in the same boat. Ive been trying to understand the setting circles for polar alignment as well (unless after reading this they are only used to find other stars?) and im getting even more confused than you guys!

My thread is here:

http://stargazerslounge.com/equipment-help/87286-accurate-polar-alignment-ra-polar-scope-help.html

[Karo]

If you point at say Vega which has a known RA and Dec position, for the sake of argument suppose it's RA 4 hours and 30 minutes, then by rotating your RA axis (or running your motor drive) during the evening you're working to *stay* pointed at RA 4h30m (and hence Vega). Your RA axis value thus shouldn't change, as you're pointing at the same place, so you lock the axis and let the scope move but the axis not. The co-ordinate system itself rotates so RA 4h30m isn't in the same spot for long.

This is how I think about it, which of course could be totally wrong... it's all hopeless though for me as the RA circles on an EQ3-2 don't lock at any other position than 0, so it slips around anyway. All I can do (I think) is to re-calibrate every time I want to use them, which isn't often, fortunately.

[hoobz]

This lol, as a n00b is how i do it, it maybe the wrong way to do it, but for now, it works for me .. hope it helps. (with a EQ3-2)

I hope this message aint overkill lol

first orf i always balance me scope. (read yer blumming manual )

you like me hav probably done the polar align but fort I'd put it up anyhoo.

then I polar align. with polaris in site I point the leg with 'N' on it north.

Then adjusting my altitude to 52 (Ipswich uk) with the adjusting bolts(along with the altitude scale are shown in pic below) put Polaris almost bang centre in my view port(view port shown in pic above)

if polaris aint center of me axis view port I either twizzle me tripod legs a bit or more preferably use the azimuth adjustment knobs to move the mount left or right (azimuth knob just below the left red arrown in the pic above).

right, now polaris is in my scope, I unlock the RA & DEC lock knobs and swing it carefully round to VEGA, yep that one, Bright [removed word], straight up!! aye, 2 weeks off work witha buggered neck huh.

once centered in me viewfinder (lock the ra and dec knobs back up), I then center vega in me main eyepiece, an then double back with me viewfinder, just to make sure their both bang on center thats all. fussy git me.

right now vega is centered u gotta set your RA scale to 18h36m.. unock the ra scale lock knob an turn ur scale til it looks like mine below...

i now dont lock the knob back fully, i just giv it a little tweak. (works a treat for me) You'll notice also that i aligned vegas coord's with the arrow, somebody on here the other day said to align it with the vernier scale which is the numbers in black, but that just confused me more.

now the dec scale should be reading 39.. look below...

this is where i went all **** up because i didn't realise that my dec scale has 2 arrows on it !! how did i not spot 2??? because my motor drive bracket is in front of it!! The one i couldn't see was showin 39, the one i could see was showin 48 or something!

so i used the alan key hole to unlock the dec scale and set it to 39 under the arrow i can see.

confusing ? yes!

works for me, i then moved me scope to 0h43m on the ra and 41o on the dec and andromeda was in me main eyepiece, not centered i may add, but it was there.

now ur dec scale is set, thats it. that doesn't need touchin. my ra scale goes out a touch, but it takes 10 seconds to re-do it.

like i said, hope this helps, I'ma noobie an only 3 weeks in. lol

[milan]

Useful stuff, thanks. My next question was how to set the DEC scale.

[blinkity-blonk]

Nice one Hoobz. I'll be giving that a go... when its stopped raining. I fear I may need to make some more major 'adjustments' to my mount first though - after I rebuilt it and cleaned all the Chinese gluey grease out of it neither axis went back in exactly straight there's about a mm in wobble each way, which plays havoc with everything. But I should be able to learn what I'm doing before having to do that tedious job again!

[hoobz]

cool, hope it helps.

[hoobz]

UNBELIEVABLE! you use the lower set of numbers on the ra scale for the northern hemisphere, thats not what it says in the manual tho. crazy, unless this guy is wrong, (nb), searched this forum for help and found this vid posted by dark knight on another topic....

How to Use Setting Circles

[CaptPaul]

Useful stuff, thanks. My next question was how to set the DEC scale.

Ok so im very very new to this so might not be right (read on at your own risk lol) but i had a go at setting my scope up its on a EQ2 mount this is what i did...

find out what lattitude your on, usually 52 degs for the uk roughly and put that in the altitude scale using the twisty bit at the bottom. Then i set the Dec scale to 90 and locked it then using the azimuth turned my scope towards polaris, im guessing that would mean theoretically the horizons are the 0 points either side. this is really vague and prob wrong but if i got it wrong ill find out why now hopefully. once you done this bit you carry on like hoobz how to, to do the rest (which i found really usfull thanks!)

sorry if this is wrong but hopefully we will all find out the right way soon!