Why is my dec. setting circle fixed but R.A. movable? + other quick newbie questions

[uyotg]

Edit: Sorry, typo in the title... "... fixed but R.A...."

Please keep in mind I'm still new to this and just reading up on how to use an equatorial mount... on paper, I think I get it, but I've yet to actually use these setting circles to find anything in the sky (just got the scope on Tuesday, it's been cloudy every night so far ).

From what I understand, the RA coordinates are for finding an object in the sky, and these coordinates are always the same. So shouldn't the dial be stationary? Instead, it moves whenever I adjust the RA of my scope. To put it another way, it's kind of self-centered how will I be able to find an object at so-and-so RA coordinates if, whenever I adjust the RA axis, the setting circle will always read the same thing? On the other hand, if something is at 16H 0M, I can adjust the setting circle and the scope won't actually move, so I'm just pointing at the same thing.

And a couple other newbie questions if you folks don't mind:

1. I'm using the Skywalk iPhone app in the mean time, and the only info it gives about a planet is visibility time and its elevation. I adjust my declination to this elevation, correct?
   
2. Am I never suppose to move my scope along the RA toward a certain direction? It seems that all the balancing tutorials always put the counterweight on the right side and barrel on the left (if looking in the same direction of the scope's), but I don't know if this is a mechanical limitation of EQ mounts or if it's simply just because the RA adjustment knob is in the way.
   
3. Hypothetically, this also means I can't follow a star for 24 hours straight, correct? Simply because the barrel would crash with the various parts of the mount and tripod.
   
4. When putting the mount in the home position, the pin should be pointing to 90 on the declination setting circle, correct? Or does this vary with different mounts? 90 seemed to make sense to me, but from looking at it with my eye, it doesn't look to be aligned with the RA axis.
   
5. Why won't the fog and clouds go away
   

Thanks

[Scott]

hi uyotg. i'm pretty new myself but in regards to counterweights as far as i'm aware, when the counter weight rises above horisontal then you need to do a "meridian flip" which involves rotating the telescope 180 degrees on the dec axis then rotating 12 hrs (180 degrees) on the RA you should then be pointing in the same position. hope this helps.

[Bizibilder]

I would advise ignoring the setting circles completely! They are too small (diameter wise) to be of any real use. It is unlikely you could get within 3-4° with them.

Instead use the "star hopping" method. Find a bright star in the scope and move in careful steps to your chosen target. Use something like Stellarium or Cartes du Ceil to show the background stars so you can find your way about.

The finder is the best tool for this job - as it has a good wide field of view. Then go to the scopes eyepiece (lowest power = largest field of view) and center your target. It takes a bit of practice but you will quickly get the hang of it.

If you are feeling wealthy then a Telrad type finder is very useful addition to your kit for "star hopping" - it produces clearly visible rings against the sky that you can easily line up on the position of your target.

[astromartian]

I guess the mount is very useful for tracking an object once found but it seems from having read several posts that the setting circles are useless.

I have 2 circles on the RA, one fixed (closer to the mount) and the other moving (further from the mount). Not sure how to use them but it does seem like accuracy was not a priority when designing these. The stationary one seems to wobble from side to side slightly.

[E621Keith]

What mount are you using?

The dec setting circles on EQ3-2, EQ5 and many mounts are useless. The RA circles on most mounts are mostly useless. However, on mounts that uses the Vixen polar scope system (Vixen mounts, EQ3-2, EQ5, CG5 ...) the RA setting circle is used for calculating the position of Polaris during polar alignment.

[barkis]

Small circles will give you more headaches than they cure.

If you have to, use only the declination circle, and forget the RA one.

To be reasonably accurate, your polar axis must be set accurately.

That is, the mounts polar axis must point to the north celestial pole.

For observational work, Lining the axis with the star Polaris will be ok.

Once you have the mount PA set, look in a star atlas, or almanac, and find a bright star visible in your night sky. Centre the star in a medium power eyepiece, and then set the declination circle pointer to the corresponding number of degrees on the circle. The circle should not be fixed, but movable. It should be lockable, so look for the screw that locks it in place.

Once you have the declination properly set, then any other object can be found simply by rotating the mount in declination, to read the targets dec. coordinate. Lock the scope in declination, an with the RA clutch loose, sweep slowly in Right Ascension to find the target.

This method works if you have the patience. Once the declination circle has been set by using a known stars dec. it should not need moving again, except perhaps to fine tune it.

Please remember though, the accuracy is dependent upon how well your polar alignment has been carried out.

The Right Ascension of any target you seek, you will need to estimate by star hopping, having found the target from a star map, and comparing it to other stars in the sky.

This is a learning process, no short cuts I'm afraid, unless you buy a GoTo mount . Star hopping is a good way to find your way around. It takes time, but you will eventually be very welcome at star parties, as the whizz kid who can find any object without a map, or a goto .

Good luck

Ron.

[astromartian]

So I'm finding a known star with a known declination to align the declination circle on my EQ5? I understand but I don't think the Dec. circle on the EQ5 is moveable. I'll check when I get home. The R.A. circle is (I think) ajustable - there is a small screw next to it.

[marshy123]

I would honestly recommend reading around about how GEMs function and why they move in the way they do. I had someone explain it to me on a forum several times before and it just didn't sink in properly. I genuinely don't mean this to sound really obnoxious (and I hope it doesn't) as I am very much a beginner too, but if you don't know the answer to this question then probably do some more reading and investigating!!! I had to build little models and watch videos and simulations about how the earth, sun etc interact before I got my head round it. Now it really has sunk in though and what used to look like a bizarre torture device actually makes perfect sense. I still reckon the setting circles are rubbish though, I'm looking into ways to ascertain how far out the setting circles on my EQ2 are. Cheers, Chris.

[E621Keith]

So I'm finding a known star with a known declination to align the declination circle on my EQ5? I understand but I don't think the Dec. circle on the EQ5 is moveable. I'll check when I get home. The R.A. circle is (I think) ajustable - there is a small screw next to it.

The RA set screw is for locking the hour circle when you adjust the date circle on the second stage of the Polaris position calculation in polar alignment.

Polar alignment

1. Set polaris in polar scope vertically down. Set time and date to midnight, 1st November.

2. Lock hour circle using the set screw and rotate the RA axis until the date circle matches today's date.

3. Unlock the hour circle and rotate RA until the hour circle matches the current time. Apply local meridian correction if necessary. Lock RA clutch when this is done.

4. The polaris indicator in the polar scope is now set to the correct position. Look through polar scope and perform polar alignment.

[astromartian]

I would honestly recommend reading around about how GEMs function and why they move in the way they do. I had someone explain it to me on a forum several times before and it just didn't sink in properly. I genuinely don't mean this to sound really obnoxious (and I hope it doesn't) as I am very much a beginner too, but if you don't know the answer to this question then probably do some more reading and investigating!!! I had to build little models and watch videos and simulations about how the earth, sun etc interact before I got my head round it. Now it really has sunk in though and what used to look like a bizarre torture device actually makes perfect sense. I still reckon the setting circles are rubbish though, I'm looking into ways to ascertain how far out the setting circles on my EQ2 are. Cheers, Chris.

Yeah I understand what you're attempting to highlight but I'm more interested in practial application of theory which I am already vaguely familiar with. It is the paculiarities of the EQ5 mount that are throwing me not knowledge of Polar Allignment, why the sky moves the way it does and what Declination and Right Ascension setting cirles indicate. It doesn't really help that the instruction booklet which came with the scope contradict berkis' advice. The instructions talk about setting (calibrating) the R.A. setting circle using the method berkis described for the Declination setting circle.

I'm off to immerse myself in books and might come out with something more useful to add than questions.

[E621Keith]

Yeah I understand what you're attempting to highlight but I'm more interested in practial application of theory which I am already vaguely familiar with. It is the paculiarities of the EQ5 mount that are throwing me not knowledge of Polar Allignment, why the sky moves the way it does and what Declination and Right Ascension setting cirles indicate. It doesn't really help that the instruction booklet which came with the scope contradict berkis' advice. The instructions talk about setting (calibrating) the R.A. setting circle using the method berkis described for the Declination setting circle.

I'm off to immerse myself in books and might come out with something more useful to add than questions.

The declination circle is marked in 2 degrees increments, or roughly 4 times the diameter of the moon. This is why they are useless.

[marshy123]

I'm off to immerse myself in books and might come out with something more useful to add than questions.

Really hope I didn't come across as pompous. Hard to get the intended tone across sometimes, even with smilies.

My instruction manual was in German!

[astromartian]

Really hope I didn't come across as pompous. Hard to get the intended tone across sometimes, even with smilies.

My instruction manual was in German!

Don't worry about it, it's hard to get the right tone across in text form. I do think it is useful to include links to guides/threads when telling people to go away and read up on stuff. This is after all a Beginners' Help section.

Having said that I checked the manual and there is definately no mention of using barkis' star hopping technique.

Oh yeah, about the German, mine too has a German language section but this is the second part of the manual, the first bit is in English but it did confuse me a bit when I flicked staight to the last few pages the first time I opened it.

freie himmel! (Clear skies! in German)

[astromartian]

This says quite a lot since it comes from the manufacturer's own 'mouth'.:

"The setting circles will get you close to the object you wish to observe, but are not accurate enough to put it in the centre of your Red Dot Finder's field of view. The accuracy of your setting circles also depends on how accurate your telescope is polar aligned."