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Sniemiec
member


Reged: 08/09/12

Loc: Johannesburg, South Africa
Nexstar 8SE Polar Alignment on Wedge new
      #5585199 - 12/23/12 08:20 AM

So after getting regular success with Alt / Az alignment with my SE8, and even being able to get some success with 30 sec subs using a Canon T1i at prime focus. I decided to ignore all the wisdom from this (and other!) forums. Yup. I decided to use a wedge to polar align my OTA and try to get longer subs!

In my defense, I have got an old Meade 2080 lying around, with an attached wedge. So I figured I should be able to use the tripod and wedge with my SE. The Meade tripod is almost 30 years old, and comes from a time when tripods were REAL tripods. Compared to the flimsy little thing that comes with the SE, the Meade tripod is built like Stonehenge! With the addition of some thick rubber feet, and an aluminum adapter plate, the SE felt really solid!

But no matter what I did, I could not get the Polar Align steps completed. each time I got to do the Polar align portion, it would synch to the star, then slew wildly off. I finally dusted off a laptop and installed NexRemote, just in case. Immediate success.

In case anyone has the same issues. HC 5.20 is known not to work, I have 5.21. Also no good. NexRemote reports HC 5.18!

So, don't even try polar alignment with HC firmware later than 5.18 until a proper fix is published. (Most would say don't try with a single arm mount and spur gears! But the Meade tripod and wedge were just too tempting to ignore)

If anyone's is interested I will document the exact process, and report back on 'first light' experience of the setup..


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C8er
super member


Reged: 09/15/12

Re: Nexstar 8SE Polar Alignment on Wedge new [Re: Sniemiec]
      #5672431 - 02/10/13 02:14 PM

Hi sniemec.

Yes I'd be very interested to hear yr procedure as I just bought a second hand wedge for my 8SE. Like you the updated hand control firmware gives me a wrong slew to the selected star during the all star polar alIgnment process, after syncing to the star successfully in the first step. I haven't tried nexremote yet, but will.

I think you very kindly helped me fix runaway gotos on the mount a few months ago, which was fixed by a hand control firmware upgrade, to the version that now won't work with the wedge!

I have a CG5GT gem mount as well which is my main imaging mount, but want to keep the SE wedge at our holiday house for occasional astrophotography use with the SE mount.

Cheers, Chris.


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Sniemiec
member


Reged: 08/09/12

Loc: Johannesburg, South Africa
Re: Nexstar 8SE Polar Alignment on Wedge new [Re: C8er]
      #5674840 - 02/11/13 09:34 PM

Hi Chris

I'm glad your runaway GoTo's got fixed, and hope you are enjoying your scope as much as I enjoy mine.

Using the NexRemote to do the polar align works exactly as it says in the manual. I just had to reread it a couple of times to get my head around what was going on. To Summarise:

Dig out and insert your illuminated reticle. This really helps. ( Or use the doughnut technique.)
Level the tripod.
Align North/South. I am in Southern Hem so I point my OTA to the south.
Check that you have allowed for Mag Dec! For me it is 18 deg. So can have a big impact.
Re-level tripod.
Point your OTA to your latitude in deg above the horizon by setting the wedge.
Wait for dark as all the above are easiest in daylight!
Select EQ North or South align. This builds a map in your scope.
Then sync on a star, and do the Polar Align. This basically points at where the star should be with perfect polar alignment.
This is where you adjust the wedge manually without touching the HC. You may have to physically move the tripod. The beauty of this method is that you do not have to locate Polaris. Or for me Sigma Octans.
Then repeat the EQ align.
Repeat the above for more perfect alignment.

Good luck & clear skies.

Stefan


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C8er
super member


Reged: 09/15/12

Re: Nexstar 8SE Polar Alignment on Wedge new [Re: Sniemiec]
      #5676100 - 02/12/13 03:37 PM

Thanks for that Stefan. That advice will be very helpful I am sure.

I have a CG-5GT Eq mount as well, so am familiar with All Star polar alignment on a GEM mount rather than with a wedge, and I really enjoy my 8SE in Alt-Az mode, once the firmware upgrade fixed my runaway gotos.

I'm looking forward to seeing if I can now get on top of the challenges of using the second hand wedge I bought for the SE and trying some autogudied images, being well aware of the known limitations of the motors/gears/backlash, the single arm, and the tripod that the SE mount has, which I know will limit how long my subs can be even with guiding.

It's a shame the latest HC firmware doesn't work with the polar align, but I'll give Nexremote a try instead. I haven't ever used Nextremote yet, just the hand control so far. I wonder, given the relatively small number of people using the SE mount with a wedge if anyone has reported the HC firmware problem to Celestron yet. Have you talked to them?

So in your process do you go straight in and do a polar align first, without doing an EQ South two star align first? (I'm southern hemisphere too, NZ). I was assuming I should do an Eq two star align (auto two star or otherwise) then go into the all star polar align process, then turn the mount off and back on and redo a two star Eq align finally, but if I can skip the first two star align that would be great.

I do have an illuminated reticle EP so I'll use that.

My Mag Dec is 20 deg here and a compass app in my android smartphone has that entered in and seems to give surprisingly accurate results so long as I calibrate it regularly (just moving the phone in a figure eight motion with the compass going).

I also have a Wixey WR365 digital/electronic angle gauge/level to check that the wedge is at the right alt angle for the SCP after the tripod/wedget is levelled (also using the Wixey) and pointed south. The Wixey is a very handy device, compact and not expensive and it also means I can use a couple of non powered alt az mounts for push to work using the Wixey and a compass, getting my alt and az angles for my target from the Sky Safari pro app on my smartphone.

At first I'm planning to use a smaller lighter OTA for my wedge experiments on the SE mount, rather than the 8 inch SCT, to take some load off the gears/motors and see if that makes some autoguided imaging practical. I've got a smaller Mak-Cass OTA so I might try that to start with, or even my ST80 refractor and try some really wide field targets.

Cheers,
Chris


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Sniemiec
member


Reged: 08/09/12

Loc: Johannesburg, South Africa
Re: Nexstar 8SE Polar Alignment on Wedge new [Re: C8er]
      #5676529 - 02/12/13 08:20 PM

Hi Chris

Sounds like you have an impressive array of kit. I'm jealous.

Sorry if I wasn't clear. You must first do the EQ South align to build the sky map. Then Polar, then power cycle and EQ South again.

I would be interested in your results. At present, my 30sec subs when in Alt/Az mode give better results than using the wedge! I am assuming 'pilot error' so plan to keep trying.

Cheers
Stefan


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C8er
super member


Reged: 09/15/12

Re: Nexstar 8SE Polar Alignment on Wedge new [Re: Sniemiec]
      #5676530 - 02/12/13 08:22 PM

Hi Stefan,

I tried Nexremote (Firmware 4.21 which was the highest that my installed copy of Nexremote had available) and as with your own experience Nexremote works for the slew after the sync during all star polar align while my HC(Nexstar+ HC with firmware 5.21.2200) gives a bad slew.

Cheers,
Chris


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Sniemiec
member


Reged: 08/09/12

Loc: Johannesburg, South Africa
Re: Nexstar 8SE Polar Alignment on Wedge [Re: C8er]
      #5676618 - 02/12/13 09:24 PM

That is good to know Chris.

I have avoided upgrading NexRemote in case it was the version that killed the alignment.

I would think this type of issue would be of interest to Celestron support. But my experience with them is very poor. No response other than what looks automated. This forum is my support site!

I would be interested in your AP experience using the wedge.

Cheers
Stefan


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C8er
super member


Reged: 09/15/12

Re: Nexstar 8SE Polar Alignment on Wedge new [Re: Sniemiec]
      #5677961 - 02/13/13 04:27 PM

Hi Stefan,

I've sent off a report of the hand control slew error in the polar align process to celestron support so we will see if anything comes of that. I have had a response from them in the past on another issue, even if it was weeks later.

I'll let you know how the imaging experiments go.

It may be just the known limitations of the wedge on the 8SE mount that are limiting your sub times rather than pilot error. They discontinued the wedge for perhaps good reasons.

I will try it with autoguiding so that may help, but even that may not overcome the limitations. I'm hoping that a smaller, lighter OTA will make it at least workable.

At least the polar align works well now using nexremote thanks to me seeing your post here.

Cheers,
Chris


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Menefist
newbie


Reged: 09/24/13

Re: Nexstar 8SE Polar Alignment on Wedge new [Re: C8er]
      #6098505 - 09/24/13 01:36 PM

Hello Chris,

I was curious to know if Celestron did ever answered to your request.

As of today the latest firmware for the Nexstar+ is 5.21.2336 , I haven't had the chance to try the Polar Align function yet but I'd like to know if anyone had success with it or still had some problems with the incorrect slew.

I've recently purchased an HD Celestron Wedge and I'll be trying it soon with my 8SE.

Best Regards,
Andrea.


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C8er
super member


Reged: 09/15/12

Re: Nexstar 8SE Polar Alignment on Wedge new [Re: Menefist]
      #6098799 - 09/24/13 04:17 PM

Hi Andrea,

Interestingly I have been talking to Celestron directly about it in jusst the last few days as I had to talk to them about other things, and the enginer who will be doing the fix tells me the firmware fix to the All Star Polar align problem on the Nexstar+ Hand Controllers has been delayed again by other higher priorities.

The bug only occurs though on mounts used in the Southern Hemisphere so you should be able to do polar aligns with your wedge if you are in the Northern Hemisphere. If you are southern hemisphere you can use the Nexremote hand controller emulator program on a PC with a Celestron serial cable to the hand controller to do the aligns and drive the mount instead of using the hand controller until the bug is fixed. Nexremote gives you the option to choose which firmware version to use when you run it and older firmware versions (the version before 5.21 I think) do the polar align just fine anywhere in the world.

I hope that helps Andrea. If you are northern hemisphere the bug shouldn't affect you anyway.

From my exeprience so far don't expect too much from the SE mount with the wedge as the single arm and the accuracy/robustness of the mechanics of the mount limit how well a wedge can work on it for astrophotography, especially if you use a heavy OTA on it like the 8" inch SCT with a heavy camera. It may work ok though with a smaller, lighter, widefield scope on it and a lightweight camera, and with relatively short sub exposures. Celestron stopped selling the wedges for the 6/8 SE mount for that reason, as it was never a very successful combination for the astrophotography work they had hoped it would work for.

Right now I'm wrestling with getting one of the new starsense auto align accessories working on my mounts in the Southern Hemisphere.

Regards,
Chris M

Quote:

Hello Chris,

I was curious to know if Celestron did ever answered to your request.

As of today the latest firmware for the Nexstar+ is 5.21.2336 , I haven't had the chance to try the Polar Align function yet but I'd like to know if anyone had success with it or still had some problems with the incorrect slew.

I've recently purchased an HD Celestron Wedge and I'll be trying it soon with my 8SE.

Best Regards,
Andrea.




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