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Equipment Discussions >> Mounts

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hcsceo
super member
*****

Reged: 10/14/09

Loc: Austin, TX
Re: Celestron VX mount [Re: Whichwayisnorth]
      #5693248 - 02/21/13 06:03 PM

regardless of the level you just need to be able to point the RA axis at the celestial pole. You can do this regardless of the tripod level. To illustrate the point you can setup your mount here in the USA and point at the pole. Someone in China can do the same however technically their mount is upside down in relation to yours since they are on the otherside of the world however they still work. Level only matters in two instances. 1. keep the mount from toppling over and 2. Getting to the first couple of stars in alignment based on your location. An unlevel mount only changes your apparent position in longitude or latitude for the computer but is corrected once you are aligned.

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Carl N
sage
*****

Reged: 03/18/12

Loc: San Diego, CA
Re: Celestron VX mount [Re: Whichwayisnorth]
      #5693253 - 02/21/13 06:04 PM

Because your polar aligning the head anyway. Think about your fork on a wedge. If your tripod was off level by one degree, you could adjust your wedge from real latitude to compensate for that one degree.
With EQ mount once you get the Dec pointing at the center of rotation, your aligned so who cares if your tripod is 5 degrees off level, the top of the head isn't once your polar aligned.

Make sense?


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Whichwayisnorth
Pooh-Bah
*****

Reged: 07/04/11

Loc: Southern California
Re: Celestron VX mount [Re: Carl N]
      #5693309 - 02/21/13 06:38 PM

Ok if that is tell me like I'm five then lets go down to tell me like I'm 2.

Here is where I have a problem. When pointing RA at the pole it is understood that as the earth spins the objects will appear to move. If you slew to an object on the celestial pole and track it from the time it rises in the east until it sets in the west, (After a meridian flip of course)then it would seem if your mount was low on the north leg so you adjust the RA up a bit more than you would if it was level. So lets say instead of being at 40degrees you make it 41 degrees. That would mean, to me, that when the mount swings around due south it would expect an object to be at a certian point but instead the mount would be a little too low. Or if the mount was low on the east side and you pointed at the pole, once the mount went over to the west it would be too high. I think what I'll have to do is just take everyone's word for it and go on with my life. I've always made sure my mount was really level so I could rule it out as an issue when tracking.


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Mkofski
Pooh-Bah
*****

Reged: 07/19/11

Loc: Greenfield, Indiana, USA
Re: Celestron VX mount [Re: Whichwayisnorth]
      #5693334 - 02/21/13 07:03 PM

Michael,

I'm with you... I know it doesn't matter because many mambers smarter than me have said so but it make no sense.


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Joe Bergeron
Vendor - Space Art


Reged: 11/10/03

Loc: Upstate NY
Re: Celestron VX mount [Re: Whichwayisnorth]
      #5693390 - 02/21/13 07:32 PM

Thought experiment: take your equatorial head off the tripod. Use your telekinetic power to levitate the head and direct the polar axis at the pole.

Does it still work?


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Carl N
sage
*****

Reged: 03/18/12

Loc: San Diego, CA
Re: Celestron VX mount [Re: Joe Bergeron]
      #5693427 - 02/21/13 07:53 PM

Good idea , Joe.

I think there isn't way to explain this in writing here. Best thing to do is have someone show you on a EQ mount in person.


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jrcrillyAdministrator
Refractor wienie no more
*****

Reged: 04/30/03

Loc: NE Ohio
Re: Celestron VX mount [Re: Carl N]
      #5693448 - 02/21/13 08:03 PM

Best way to look at it is to see what part of the mount rotates horizontally when in use. That part would be inaccurate if the mount isn't horizontal. The good news is on an EQ mount NOTHING rotates horizontally when in use - so that plane is never used as a reference for anything.

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chasdz
member


Reged: 01/04/13

Loc: Seattle
Re: Celestron VX mount [Re: Carl N]
      #5693454 - 02/21/13 08:06 PM

Well I contacted Celestron and was told the Same thing. IT doesn't matter just as long as it's close the computer will fill in the blanks. Too many years using a LX200 I guess .

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GTBaker
member


Reged: 02/01/13

Re: Celestron VX mount [Re: jrcrilly]
      #5693456 - 02/21/13 08:07 PM

Still waiting for my 8" EdgeHD with VX. The waiting is making me silly. Only good thing is the weathers been poop.

Edited by GTBaker (02/21/13 08:13 PM)


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chasdz
member


Reged: 01/04/13

Loc: Seattle
Re: Celestron VX mount [Re: GTBaker]
      #5693467 - 02/21/13 08:13 PM

I know I'm off topic Seattle's weather been gray for weeks

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186vett
member


Reged: 01/29/13

Re: Celestron VX mount [Re: benula]
      #5693670 - 02/21/13 10:15 PM

Wow!
Fasinating discussion! Received the VX mount & 8 EdgeHD about a week ago & all my expectations for visual just fantastic! About 10 years ago, did AP with a fork mounted Celestron 8, Nikon 4500, & an lens from a company called Scoptronix, which attached directly to the camera. Well, you folks could not imagine how much I enjoyed the AP experience, & if interested could post some photos from my experience at that time. Monday, will receive a Tak 85EDX & really feel this is the way to begin imaging again, with a Canon 4Ti. Then perhaps, purchase, the reducer for the Edge HD, & really enjoy, what we all
attept to attain, Great photos of the dark sky.
Take Care All-Jerry


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Starhuckster
super member


Reged: 09/09/10

Loc: Boston, MA
Re: Celestron VX mount [Re: chasdz]
      #5693686 - 02/21/13 10:26 PM

After reading this thread and checking out the mount online, I'm pretty interested. I see they're coming out with a compact guide scope accessory too, which seems like a nice option. I've been reluctant to get into imaging, but if this is as good as it seems so far, it could totally work.

Since I have no experience with imaging, and I'm kind of a noob overall, is $329 for the guide scope add on a good deal? It seems like it might be, if it works.


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Falcon-
Post Laureate
*****

Reged: 09/11/09

Loc: Gambier Island, BC, Canada
Re: Celestron VX mount [Re: Starhuckster]
      #5693716 - 02/21/13 10:39 PM

BTW - regarding levelling. I agree that for visual use no need to worry, just set it up and go, the go-to calibration Knows.

For *imaging* with long exposure though a quick levelling of the top of the tripod (especially east/west) before putting the mount head on does the trick. I have a 6" bullet level packed with my astro-gear for that. (this works with my lowly CG5 so I assume the AVX will do fine that way too )


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SkipW
sage


Reged: 02/03/11

Loc: Oklahoma, USA
Re: Celestron VX mount [Re: Falcon-]
      #5693742 - 02/21/13 11:04 PM

As many have noted, the tripod head doesn't need to be level to work, as long as the polar axis is pointed at (or near) the pole.

Those bubble levels can be helpful in setting up, even if they're not accurate, as long as they're repeatable. If you get the mount reasonably well aligned with the bubble indicating level, the next time you set up (in the same vicinity), the latitude adjustment will already be close if the bubble is in the same spot. Now you just have to find true north.

With an equatorial mount, you want the polar axis to be parallel to the earth's axis of rotation. The orientation of the base it's sitting on doesn't matter at all (as long as it's stable).


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core
Pooh-Bah
*****

Reged: 02/23/08

Loc: Mostly in Norman, OK
Re: Celestron VX mount [Re: Starhuckster]
      #5693779 - 02/21/13 11:40 PM

Quote:

Since I have no experience with imaging, and I'm kind of a noob overall, is $329 for the guide scope add on a good deal? It seems like it might be, if it works.




If you're referring to the soon-to-be-release StarSense Accessory, it is NOT a guide camera - once installed, it automatically aligns the VX mount for you, for GoTo's. For long exposure imaging, you will still need to polar align the mount - the All Star Polar Alignment routine will assist, but you will still need to physically tweak the altitude and azimuth adjustments of the mount.

Here is Celestron's Q&A on the StarSense.


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CounterWeight
Postmaster
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Reged: 10/05/08

Loc: Palo alto, CA.
Re: Celestron VX mount [Re: core]
      #5693822 - 02/22/13 12:07 AM

You are not aligning the mount to the earth or anything on it, you are aligning it to things up in space. As long as your not so messed up that the mount can't point where required (mostly up i hope?), you are good to go.

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Whichwayisnorth
Pooh-Bah
*****

Reged: 07/04/11

Loc: Southern California
Re: Celestron VX mount [Re: Falcon-]
      #5693870 - 02/22/13 12:46 AM

Quote:

BTW - regarding levelling. I agree that for visual use no need to worry, just set it up and go, the go-to calibration Knows.

For *imaging* with long exposure though a quick levelling of the top of the tripod (especially east/west) before putting the mount head on does the trick. I have a 6" bullet level packed with my astro-gear for that. (this works with my lowly CG5 so I assume the AVX will do fine that way too )




See now just when I was ready to take everyone's word for it you come along and it is all back up in the air again.


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WadeH237
Pooh-Bah


Reged: 02/24/07

Loc: Snohomish, WA
Re: Celestron VX mount [Re: Whichwayisnorth]
      #5693902 - 02/22/13 01:26 AM

To function correctly, the only requirement is that the mount's RA axis is parallel to Earth's rotational axis. This allows the mount to cancel Earth's movement by rotation in the opposite direction of the Earth. Achieving this is called polar aligning the mount.

There is no difference in polar alignment between visual and imaging, except that imaging benefits from a higher degree of accuracy. Also, as long as the RA axis is parallel to Earth's rotational axis, the position of the tripod does not matter at all for tracking, etc.

The main benefit to levelling the tripod before polar alignment is that it may be a little bit easier to actually perform the polar alignment with the tripod level. This is because you achieve polar alignment by adjusting the altitude and azimuth of the mount. If the tripod is not level, adjusting the altitude may also slightly affect azimuth and vice versa. If the tripod is perfectly level, an altitude adjustment affects only altitude, and an azimuth adjustment affects only azmuth.

In practice for me, I find that polar alignment for visual use does not require much accuracy. If I just want to observe for an evening, I just plop the mount down with RA axis pointed mostly north (using a compass is plenty sufficient), eyeballing the mount level, and doing a 2+4 align and calibration. I don't even bother to do the all-star polar alignment.

For imaging, I do actually level the mount with a carpenter's level, do the 2+4 alignment and calibration, followed by the all-star polar alignment on a star near the southern part of the celestial equator. This usually works just fine for doing guided imaging. If I'm going to be set up for many nights, I'll sometimes take the extra step of doing a drift polar alignment (using PEMPro). But really, I don't see much difference between doing the drift alignment and doing just the all-star polar alignment.

Just my two cents on the topic,
-Wade


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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Celestron VX mount [Re: WadeH237]
      #5693990 - 02/22/13 03:45 AM

As Wade says the only time when you move the scope in axes that are related to the Earth's surface is when you are doing the polar align. Having the base of the scope level helps for this but it does not need to be precise. A degree or two out will not matter. If you are a long way out - 5 degrees or more - then it will matter, especially for ASPA.

For imaging at home I set the tripod level - more or less - with a builders level and mark the leg positions on the patio. I don't touch the tripod legs and next time I put the tripod down in more or less the same position (within an inch or two) and get on with aligning.

If I wanted to be more precise I would make physical locations for the tripod legs so the position was repeatable to within a millimetre, that way I might be able to preserve the polar alignment.

Chris


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Chuckles34
member
*****

Reged: 08/03/11

Loc: San Antonio, TX
Re: Celestron VX mount [Re: ghataa]
      #5694244 - 02/22/13 09:11 AM

Does anyone know if the Orion pier extension that works with the CG-5 will also work with the VX?

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