RA Circle is not correct.

[ItsRiftzy]

Hey there,

I'm fairly new to EQ mounts but I think I know the basics on how to set it up. I've been having an issue where when I polar align to Sigma Octantis then calibrate my RA circle on Sirius. My RA circle is still off when pointing to objects that have majorly different coordinates than Sirius. The steps ive taken are below

1. Polar align to sigma octantis after pointing to due south.

2. Make sure my DEC circle is set to 90

3. Calibrate RA with Sirius by moving the circle to 6h45m

Then I began to try to point it out towards the Orion Nebula, my DEC was roughly correct in the position but my RA was pointing towards the horizon when the Nebula is right above me. 

 

I'm in the Southern Hemisphere so I'm using the bottom set of numbers on the RA circle.

Any help is appreciated!

Edited January 16, 2022 by ItsRiftzy

[Cornelius Varley]

Hello and welcome to SGL. Which mount do you have ? In all but the more expensive eq mounts the settings circles are more or less useless and not particularly accurate.

 

 

[dweller25]

I agree with Peter, I had setting circles on my Vixen mount and they were not accurate enough.

[ItsRiftzy]

13 hours ago, Cornelius Varley said:

Hello and welcome to SGL. Which mount do you have ? In all but the more expensive eq mounts the settings circles are more or less useless and not particularly accurate.

 

 

Hey there,

Sorry for the fairly late reply, I'm using a Sky-Watcher EQ2, and I just had a question, If the mount setting circles aren't accurate, what do you suggest I do to look at dim objects like the Orion Nebula?

 

Thanks

[John]

59 minutes ago, ItsRiftzy said:

Hey there,

Sorry for the fairly late reply, I'm using a Sky-Watcher EQ2, and I just had a question, If the mount setting circles aren't accurate, what do you suggest I do to look at dim objects like the Orion Nebula?

 

Thanks

Unless you are observing from an area with a lot of light pollution or under a bright moon, the Orion Nebula can be seen glowing faintly with binoculars and optical finder scopes.

From Australia, Orion looks like this, with the position of the Orion Nebula marked in this image. Use a low magnification eyepiece (say 30x - 50x) and point the scope towards the part of the constellation indicated and you should see the nebula:

Edited January 17, 2022 by John

[ItsRiftzy]

Hey John,

Thanks for replying. I do live in a fairly light polluted area so that's why my inital thought was using the setting circles on the mount to find objects but if that doesn't seem to work then I guess I won't be using them.

 

Thanks,

[kens]

On 16/01/2022 at 12:24, ItsRiftzy said:

3. Calibrate RA with Sirius by moving the circle to 6h45m

Out of interest, how do you do this calibration?

Also, one problem with setting circles is that you need to recalibrate through the night. Another method is to use the setting circles for Hour Angle where 12:00 is overhead, 06:00 is due west and 18:00 is due east. When your scope is in the home position (for the southern hemisphere it is aligned to both 06:00 if you move right in declination and 18:00 if you move left. So that's the only choice you need to make when calibrating i.e. are you going to be looking east or west. If east then movve the setting circle so that the pointer is on 18:00 and if west move it so that th epointer is on 06:00. When looking for targeets, just about every planetarium application can give you the hour angle at a given time.

As mentioned the setting circles are not very accurate but they should get you close enough to find you taget with the finder scope.

[iantaylor2uk]

I have setting circles on my Losmandy G11, which are very good (and large) and used to use them before I moved to the Gemini-2 goto system. What I generally did was find a bright star close to a DSO I wanted to image, and adjust the setting circles so the RA/DEC of the star was correct, and then moved the mount to the position of the DSO I wanted to go to. With an APS-C sized sensor and small refractor (such as a WO 81) the field of view was large enough you could usually find most DSOs using this method. 

However, it is much easier now I have Goto!

I think it will be more difficult with some of the tiny setting circles on smaller mounts (I remember a HEQ5 mount I used to have 20 years ago and the setting circles were pretty useless on that mount).

[ItsRiftzy]

20 hours ago, kens said:

Out of interest, how do you do this calibration?

Also, one problem with setting circles is that you need to recalibrate through the night. Another method is to use the setting circles for Hour Angle where 12:00 is overhead, 06:00 is due west and 18:00 is due east. When your scope is in the home position (for the southern hemisphere it is aligned to both 06:00 if you move right in declination and 18:00 if you move left. So that's the only choice you need to make when calibrating i.e. are you going to be looking east or west. If east then movve the setting circle so that the pointer is on 18:00 and if west move it so that th epointer is on 06:00. When looking for targeets, just about every planetarium application can give you the hour angle at a given time.

As mentioned the setting circles are not very accurate but they should get you close enough to find you taget with the finder scope.

Hey there,

I simply just point at Sirius or another bright star, check to make sure DEC is correct (if not I'll polar align again). Then adjust the RA circle so it matches Sirius (6h45m), this method should work well but strangely M42 is higher in the sky than Sirius from my perspective but is 1hr lower than Sirius. I'm not sure what I'm doing wrong here. I don't know if I'm using the RA circle wrong.

[kens]

3 hours ago, ItsRiftzy said:

Hey there,

I simply just point at Sirius or another bright star, check to make sure DEC is correct (if not I'll polar align again). Then adjust the RA circle so it matches Sirius (6h45m), this method should work well but strangely M42 is higher in the sky than Sirius from my perspective but is 1hr lower than Sirius. I'm not sure what I'm doing wrong here. I don't know if I'm using the RA circle wrong.

That's correct - RA decreases as you move west. Try using the other set of numbers on the setting circle.

[ItsRiftzy]

7 minutes ago, kens said:

That's correct - RA decreases as you move west. Try using the other set of numbers on the setting circle.

So have I been using the wrong set of numbers on the circle? Because I've been using the bottom set of numbers (furthest away from the pointer) is that correct for the Southern Hemisphere?

[kens]

10 hours ago, ItsRiftzy said:

So have I been using the wrong set of numbers on the circle? Because I've been using the bottom set of numbers (furthest away from the pointer) is that correct for the Southern Hemisphere?

Its so long since I used setting circles that I forget. And it might depend on the type of mount. But use whatever gives the right result. Namely, if you rotate the mount from east to west the pointer mark should point at decreasing RA values. 

Note that if you use the HA technique, that HA increases from east to west.

[ItsRiftzy]

Alright I figured it out (I am stupid) 

I have been using the wrong set of Numbers on the RA circle but for good reason, my mount manual says to use the bottom set of numbers when viewing in the Southern Hemisphere but I've been needing to use the top set the whole time. x)

 

Thank you so much for helping me, now time to pray for a clear night!