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NEXSTAR11GPS Questions

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#1 Guest_**DONOTDELETE**_*

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Posted 17 February 2004 - 04:42 PM

I haven't received my scope yet, but am in the process of ordering accessories and have questions.

The first question I have is: By adding a dew shield and a 2" diagonal, will I need to add counterweight?

Second, can anyone recommend a good power supply? All I've seen is the Celestron power tank, which is 7Ah, is that enough or will I need more?

Third, what is a good RA finder scope? Is a Telrad useful on this scope?

My next question has to do with alignment. I've never used a GPS or go-to scope before, so excuse my dumb questions. Do alignment stars have to be in the north, or can they be anywhere?
Should the scope have an unobstructed view of north during power-up and alignment? For example, if theres a house in the way.

Final question(for now), will the scope rotate completely around, 360 degrees?

#2 Dennis

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Posted 17 February 2004 - 04:59 PM

No need for counterweight with dewshield and 2" diagonal. I'm using both on my 9.25 with a heavy 35mm Panoptic.

GPS align is fairly simple. Start with your scope pointed directly down. It will find North (obstructed or not), then select two stars (such as Sirris, Castor, Aldebaran) for alignment. If you don't like one that's selected, simply press "undo". It will then choose another. BTW, once you've got it aligned successfully, go into the utilities menu and "calibrate compass". This will improve it's targeting to your alignment stars next time you take your scope out and align it. Also, the very first time you do a GPS alignment, it may ask you for your location co-ordinates and your local time. Your new scope will go around and around without any worries.

Other, more knowledgeable folk can help you with the other questions.

You're gonna have some fun!

#3 David A Rodger

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Posted 17 February 2004 - 05:36 PM

With respect to Dennis' otherwise excellent answer to your question about alignment, I'd like to offer the following comment. The telescope will select the alignment stars, not you. Or to be more specific, it will propose stars for alignment. So you need to know the sky pretty well otherwise it may head off to find a star that is not visible, either because there's an obstruction (tree, building, etc.) or it's too low for you too see. You'll save a lot of time if, when it proposes to go off to Aldebaran and Aldebaran is blocked by a tree, you press UNDO and let it propose another star. Dennis may be right about pointing it "directly down" to start. I've always just levelled it at the northern horizon, using the alignment marks on the top of the fork arm. While you wait for the telescope to arrive, why not download the instruction manual from the Celestron Web site. You can do a lot of useful "prep" for that big day when it arrives.

#4 techmgr

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Posted 17 February 2004 - 06:40 PM

As far as an RA finderscope, I just swapped out the straight through Celestron 9x50 on mine for an Orion 9x50 RA - it was on sale, don't know if it still is. I tried a Rigel Quickfinder on my scope as well, and of the three I like the Orion RA the best as far as comfort goes. There are other more expensive options like Russell, Antares, and others.

I'll third the advice that you shouldn't need counterweights for your setup. Without the dewshield it will be back heavy, though.

The scope does rotate a full 360°. No problem with the HC cable, but if you have anything else attached (heaters, etc.) it will still get wrapped.

#5 ridurall

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Posted 17 February 2004 - 07:06 PM

I purchased a Celestron Powertank when I got my NS11 and have no complaints about it and the built in light is great when your through and putting stuff away. If I had it to do again I probably would go to Walmart or some auto supplier and purchase one of those 17 amp jump start batteries. You'll get more powere out of it in case you want to use a dew heater. I didn't need any extra weights for my dew shield and 27 Panoptic eyepiece but did add some when I piggybacked my Takahashi FS78.



#6 Dennis

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Posted 17 February 2004 - 07:07 PM

Excellent clarification David! My wording was unclear, and was intended to indicate that it will find north and it will select stars. The manual does suggest to begin with tube pointed down (page 17) for GPS alignment, but I've wondered if it makes any difference. Will try your method nextime. I too point the fork north to start as it saves some slewing time. Also Jeff, I highly recommend the Nexstar User's Guide available on the Nexstar resource site: http://www.nexstarsite.com/index.html I've found it to have lots of useful information.

I'm wondering about modifying the stock finderscope for RA operation. Has anyone done this?

#7 Guest_**DONOTDELETE**_*

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Posted 17 February 2004 - 07:44 PM

does the orion RA finder fit the original celestron finder mounts?

#8 jrcrilly

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Posted 17 February 2004 - 08:01 PM

The bit about the OTA pointed down is because it is going to swing upwards and expects to trip the level switch as it passes through level. All that is required is that it be aimed a little below horizontal. Later firmware revs dip it first so beginning at horizontal works OK on those.

If it is above the level switch at the start it will swing all the way around until it does trip the tilt switch.

#9 David A Rodger

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Posted 17 February 2004 - 08:16 PM

Here's my experience with the Nexstar 9.25GPS. I will assume this applies to the 8 and the 11 as well. I level it with the marks on the upper end of the fork mount, point it north, turn it on and select GPS alignment. The OTA moves to the northeast (right) for a few seconds, then stops and moves to the northwest (left) for about ten seconds. Then it stops again and moves back to north. It stops there and reports the time (in my case, PST) and asks if that's correct. When I confirm it, it does the star alignment.

#10 go_ahead_ed

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Posted 17 February 2004 - 09:25 PM

You've received a lot of good answers so far so I'll just add my $0.02 worth:

Your scope will work fine without any counterweights, but there is a large body of users who have added a counterweight system (myself included) to reduce the loads on the gear train and "maybe" to improve go-to performance. However, I find that my aluminum AstroZap dew shield almost perfectly balances a large 2" diagonal/eyepiece combination.

For power, I use a 34 amp hour deep cycle marine battery. A bit of overkill to be sure, but you will want a 17 amp hour at least if you use a dew heater.

I replaced my finder with a Telrad (which I already had for my 8" dob), but my scope is an early model that had terrible intial pointing on the alignment stars. Since I've upgraded the motorcontroller & handcontroller initial pointing is usually very good so my reason for using the Telrad is now moot, but I still use it, it's easier on my neck! There is another nice advantage to a Telrad though...you can easily show people exactly where the scope is pointing in the sky.

Yes, the scope will rotate 360 degrees and more BUT, if you use a dew heater or other accessory with a power cord watch out for cord wrap. The scope has an anti-cord wrap feature you can set up from the handcontroller though.

Have fun with your new scope!

Ed



#11 rboe

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Posted 17 February 2004 - 09:31 PM

For my 11 GPS, I play with the tube, dipping it back and forth listening for the click of the micro switch, parking the tube just below the click. Saves time in finding level.

I dumped the straight through finder and went with the RH unit from Orion. Later on I went with their SCT mount for it. Much better. I use the power take off cord to use my car battery via the 12V ports I have in the mini van. The scope is the only thing I run and it's a small drain. A second battery is not a bad idea, but if you're short on funds it can come later.

#12 techmgr

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Posted 17 February 2004 - 10:24 PM

I am using the Orion RA finder with the original Celestron finderscope mount. I did this because I have the JMI quickmount attachment on this bracket. The fit with the stock bracket isn't perfect as the Orion is slightly shorter than the Celestron. But it does seem to work okay and stays put, at least on my scope. The o-ring isn't as tight as with the original finder, but tight enough to keep the Orion from moving around.

Orion says the diagonal and EP on their finder are not removable, but the whole assembly unscrews from the tube. It's necessary to do this to get it into the Celestron mounting bracket.

#13 Rusty

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Posted 17 February 2004 - 11:02 PM

I'm on a Finder Quest - I dumped the original straight-through Celestron for a Gary Russell 10x60. That's a decent and robust unit, but the focus is primitive. Both of those were mounted in a Celestron dovetailed QR bracket.

Now I have an Orion 9x50 with the SCT shoe, which I bought just before I snagged an University 8x50 RA with an illuminated reticle.

My impressions so far:

OEM 8x50: Yuk :p - mostly because it's straight through
Gary Russell 10x60: Very good optically, bullet-proof design. Slide-tube focus, and the reticle is off-center, so if I rotate the diagonal, the reticle goes off-target. Mounted in the Celestron bracket
Orion 9x50: Best of the readily-available. Alignment is very easy (elevation and azimuth - two screws). Helical focus. BTW, it's still on sale at $61.50 + shipping - the SCT shoe is $9.95.
http://www.telescope...&iProductID=158
UO 8x50: Upscale, maybe the best aftermarket finder. Finely etched crosshairs, double outer ring marked in 15* increments. Illumination a plus due to the fineness of the reticle. Helical focus for both optics and crosshairs. :waytogo:

#14 Michael_Swanson

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Posted 18 February 2004 - 03:25 AM

Hi David,

If you press Enter to confirm the time shown, you are bypassing the GPS link. If you wait a minute more, it will link to the GPS satellites, update the date/time to within 1 second of "accurate", update the long/lat and off it will go on it's own to the first alignment star.

It is intended that prior to pressing Enter, a person would use the up/down (6/9 on number pad) to scroll through the other date/time/location info, prior to confirm all of them are correct. This is mainly offered for those rare occasions when you cannot get a GPS link.

Best regards,
Mike Swanson
Author of "The NexStar User's Guide"
Author of "NexStar Observer List"
http://www.NexStarSite.com


#15 David A Rodger

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Posted 18 February 2004 - 09:39 AM

Mike is right. It's been so long since the clouds parted here and the rain let up, that I'd forgotten some of the specifics of just how the GPS set up and alignment works. And, of course, I've done it so often (last summer and fall before the Monsoon) that I do it without really thinking about it now. Looking forward to your book, Mike.

#16 Guest_**DONOTDELETE**_*

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Posted 18 February 2004 - 10:23 AM

Excellent clarification David! My wording was unclear, and was intended to indicate that it will find north and it will select stars. The manual does suggest to begin with tube pointed down (page 17) for GPS alignment, but I've wondered if it makes any difference. Will try your method nextime. I too point the fork north to start as it saves some slewing time. Also Jeff, I highly recommend the Nexstar User's Guide available on the Nexstar resource site: http://www.nexstarsite.com/index.html I've found it to have lots of useful information.

I'm wondering about modifying the stock finderscope for RA operation. Has anyone done this?


i just received the nexstar users guide yesterday. it looks to be quite useful. its definitely going to be a big help.

i did come across some other power supplies made by kendrick. anyone ever used one of those?

thanks for all the info. i do have another question. Should I collimate the scope right away, or only if it needs it? Since my current scope is a refractor, I have zero collimation experience.

#17 Dennis

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Posted 18 February 2004 - 10:42 AM

You should certainly check the collimation, but it will probably be fine. Unless it's really off, I'd wait to make any adjustments until you get some time on the scope.


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