Overview
This page was created because I could not find a single location with a lot of tips and tricks for the Nexstar11. I thought it would be a good idea to get most of the tips in one place for others. I must offer many thanks to the Nexstar11 Mail list. Most of the tips came from there, and if you have a Nexstar11 and you are not on that mail list, you should be. Look below for a list of mail resources... If you have a Nexstar11 tip of any kind, and want it included here, please mail me at tips@nexstar11.com if you find a wrong tip please mail me as well for correction.
Credits: The NexstarGPS mail list on Yahoo is by far the best location to find out more, or new tips. If it were not for the folks there this list would not exist. I just type them, they come up with them!
Note: You use these tips at your own risk! No guarantee of any kind is offered, nor will I be held responsible for any damage caused by the use of any of these tips... Use all tips at your own risk!!! Consider all tips as untested and possibly damaging to your telescope. It is up to YOU to test these tips...
When setting up the Nexstar11 try and position it in a somewhat open area. The GPS satellite receiver antenna is mounted in the top of one of the fork arms. If you put the Nexstar11 close to a large obstruction it will shield the antenna from the satellite and you will not get GPS lock. A normal GPS lock time should be in the 3 to 5 minute range on the outside. Be sure to leave your scope on for at lease 20 minutes the first time you turn it on.
Finding out the current software/hardware version numbers
To find out your current software revision number perform the following steps:
- Turn on the Nexstar11.
- Press the 6 button.
- Press the 7 button.
- The upper line of hand control text will display "seconds xxxx". You are now in the "Factory Debug Menu".
- Press the "0" button. The top line of text will display the current hand controller software version number. The bottom line will display 016, with a cursor at the zero.
- Enter "016" and press "ENTER".
- The bottom line of text will display the current motor controller software version number. Record this number.
- Power Nexstar11 OFF.
IMPORTANT: DO NOT DEVIATE FROM THE ABOVE PROCEDURE, ACCORDING TO CELESTRON YOU COULD DAMAGE YOUR HARDWARE!!!
When transporting the Nexstar11 back the mirror up as far as possible. This will keep the mirror from flopping around on the rails. To do so turn the focus as far clockwise as possible. Light touch here, do not force things, just very lightly snug.
Currently the latest information, (04/09/02) is that M-2, M-77, NGC 3521, and Mintaka (double star) are missing from the Nexstar11 database.
Pause after location or commanding the telescope to an object
You may see a small pause after the Nexstar11 positions itself using the controller buttons, or in a directed search. This is caused by the slop in the gear chain which positions the scope. If you end Nexstar11 movement in the downward and right direction you will get the scope in the right position to minimize the gear slop and hence the pause.
Thanks to Darrell from the NS11GPS mail list at Yahoo for this info.
Blurred images while tracking at high power
In early versions of the Nexstar11, (seems to have ended with units shipped after November 2001), the motor step frequency was close to the resonant frequency of the fork assembly, thus making the entire Nexstar11 a giant tuning fork. This caused small but fast vibrations in the fork assembly, and hence in the Optical Tube Assembly which translated to soft high power images when the drive was turned on and tracking. Call Celestron Technical support for a fix. Before you call Tech Support, get the Software version numbers as described above.
Portable Power Pack for the Nexstar11GPS
I purchased a 17 Amp Hour, 12 volt Lead Acid battery, and a small trickle charger from Batteries Plus and used an old connector cable from a wall bug as the power connector to construct a portable long lasting battery pack. I connected center to Positive, and ring to negative of the power connector I bought from Radio Shack, part number 273-1716. I then housed the entire mess in one of those cold packs used to carry lunch around in. That way if for some reason the battery leaks the fluid has several layers to work through. I used the included "Blue Ice" to keep film cold for transport during astrophotography.
After a nights use I DISCONNECT the scope from the battery pack and plug the charger into the wall. I NEVER connect the Battery pack to the wall with the scope plugged in.
Remember center is positive, ring is negative on my Nexstar11GPS it may not be on yours! If you get it wrong you blow up the electronics of your Nexstar11. It is YOUR responsibility to test BEFORE you connect anything to your Nexstar11. I will not be held responsible for your scope if you blow up the electronics as result of following these instructions! It is YOUR responsibility to insure that your Nexstar11 works as mine does. This is a description of how I built my power pack only.
Never connect the charger to the wall with the Nexstar11 connected to the Battery Pack! Remember, it is YOUR responsibility to insure that this data is correct. This only worked on my Nexstar11GPS, yours may be different. Buy a small Volt-Ohm meter and test first!!!!!
Increasing accuracy of GOTO mount
While in alignment mode, when the Nexstar11 asks you to center the guide star in the eyepiece, be very careful to get the star as close to the center as possible for both guide stars. The closer you set them, the better your GOTO capability will be.
Suggested by Mike S. of the Nexstar Mailing list: Cheaper than a crosshair eyepiece and nearly as effective is to defocus the star and then center. The large disk of an out-of-focus star is very easy to center. Use the highest magnification eyepiece available.
Correct for magnetic verses true north during initial alignment
As of February 2002, the Nexstar11GPS alignment procedure did not take into account the True verses Magnetic north difference. The mount would point to Magnetic north, then align to the GPS satellites, then slew to the first guide star. The scope would be pointing not at the first guide star. It would be off by close to the difference between True and Magnetic North in your area.
All in all this is not a real problem because you hand point the first guide star, (see Increasing the accuracy of the GOTO mount), this is corrected if you are careful in your alignment procedures. To avoid this problem totally perform the following steps:
This should place the first alignment star close to center on your finder, thus reducing the error caused by the misalignment to True North vs. Magnetic North. Rumor has it that Celestron will be providing a fix later this year to correct this problem.
Optical tube flips back over past vertical on GPS Align start-up
Part of the alignment process is to locate North, and level the Optical Tube Assembly. During this process the Nexstar11 can become confused if the OTA, (Optical Tube Assembly), is pointing above level. The correction is to be sure that the OTA is pointing about 10 degrees below level when you start GPS alignment.
Increasing the stability of the Nexstar11 Wedge
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Here is the trick to make it "better". Look at the plate that sits on top of the tripod and the two rails that sit on each side of it. You will note that you can actually move that plate to two different positions. The obvious one everyone uses is the position that places the plate even with the side rails. There is a full set of holes that allows you to move the plate about 3" towards the south end of the scope. This includes an extra set of holes for the deluxe azimuth knob. If you move the plate to this position you will dramatically remove a lot of flex and vibration that the previous setup had by nature of the long cantilever. The only thing I found is that it does change the center of gravity of the scope so you need to be aware of this. In fact I found that if you flop the wedge around 180 degrees so that the plate is held on by the threads cut in the aluminum tripod top rather than the inserts you get perfect balance. Of course as many of you know if you mount it this way the azimuth screw will run into the tripod leg top. The solution is to just replace that existing 1/4" x 20 long threaded rod with a longer rod (about 3/4" is right) and place some washers spacers between the plastic handle and the plate side so it will clear the leg top. I haven't been able to quantify the reduction in vibration or improvement in stiffness other than visual and trial by error but it seems significant. Finally make sure you have all of those side plate screws especially the bigger ones tightened down otherwise you could get some movement as the screws move in the holes. I know of some people that have used set screws to ensure that there is absolutely no movement in the areas where the big screws go. |
This tip provided by Bob Berta
Increasing accuracy of GPS alignment
Another tip; while the Nexstar does great with a two star align I found if you do a third and maybe a forth star align using the directions in the manual you will improve the accuracy even a little more especially if you do it in the area you want to observe or image. It is also important to bubble level the tripod in ALT/AZ or with a wedge for best accuracy over the whole sky. This is necessary for any GOTO or mount using digital setting circles.
This tip provided by Bob Berta
Make sure you have the right mode for time set
Make sure that your Nexstar11GPS is set to the correct time mode, either Daylight Savings time, or Standard Time. This will increase the accuracy of locating the first set of guide stars. To do this follow the steps below:
NOTE: If your Nexstar11 is already aligned and tracking enter at step 6
If you are paranoid like me, you can perform steps 6 through 10 to be sure the setting was stored.
This tip provided by Bill Warren
Avoid covering the GPS antenna
The GPS antenna is located in the top of the fork arm with the controller on it, the motor control is located in the handle arm. If you run cables, or mount things close to it, you will cover the GPS. This will result in lack of GPS lock, or extended time waiting for GPS lock.
Collimating the Nexstar11 during daylight
This text assumes you have a set of adjustment knobs, (similar to Bob's Knobs), replacing the Phillips screws Celestron supplied with the telescope. Below you will find a rough drawing of the Nexstar11 and a drawing of the front of the telescope as it should look when correctly collimated. Look closely at it, you will be using it as a guide in collimating the telescope. First familiarize yourself with the Secondary Mirror. Look at the alignment screws, these are the items you will be adjusting. Look at the blowups of the secondary, notice how things work. The screws pass thorough the screw mounting plate, and contact the mirror backing plate. As you turn one screw it applies pressure, or releases pressure. The Mirror Backing Plate is somehow connected at the center point to the Screw Mounting Plate so it would wobble if the adjustments screws were not in contact with it. Remember, the screws must be in contact with the Mirror Backing Plate when you are finished. If you look you can see that if you tighten them too much you will accomplish two things. One; you will attempt to remove the Mirror Backing Plate from the Screw Mounting Plate by force, and two, if you succeed, your secondary will fall from the corrector plate possibly destroying the secondary, and the Primary mirror! Remember light touch here, never overtighten these screws. Just finger snug. Also remember you are bound by the disclaimer at the beginning of this page so if you strip out the secondary and it smashes the primary, it's YOUR FAULT!!!
Rough indoor alignment
Take a look at the image below, the picture on the left is a correctly aligned Nexstar11, the image on the right is an incorrectly aligned Nexstar11 SCT.
Notice that the secondary and it's shadow are centered. I made it difficult to see here, because it will be difficult to see in the telescope. You accomplish this by placing your head directly in front of the Nexstar11, and about seven feet back. As you look into the center of the tube from the front, adjust your head position, and distance so you just see the reflected image of the secondary, as slightly larger and behind the real secondary mirror mounted on the corrector plate. Remember what that looks like. You will always return to this position to test your changes.
Figure 1
Step One
Look at your Nexstar11 from 7 feet back and see how bad things are. If they look centered, don't touch anything. If they look offset, you will now start to center them by adjusting the screws.
Step Two
Adjust one of the screws either in or out maybe a quarter turn, don't forget to tighten or loosen the other two screws by a quarter of a turn to compensate. Remember never overtighten or over loosen these screws! Now step back to look. Did it make things worse or better? If better continue adjusting the screw in the same direction as you did a moment ago. At some point you will decide things are as close as you can get them. If things are still not centered, you will have to pick another screw and continue. You know you are finished when you arrive at step two and the images are centered as in the drawing on the right hand side above, and, the screws are finger snug...
Below you will find a general drawing of the Nexstar11. When I want to remove the secondary, I first point the telescope up slightly so when I loosen the the secondary it won't fall out. I then grasp the knurled retaining ring and turn counter clockwise. Maybe two or three turns later the ring comes off. On my Nexstar11 there is a small Allen screw, and a mark on the exact right side of the secondary. There is also a matching slot. When you re-insert the secondary be sure that this Allen screw slides into the slot. It is possible on my Nexstar11 to get the secondary in and NOT have this screw aligned in the slot, (don't ask how I know this), if you do, you will have a devil of a time getting the secondary out. If you are going to be mucking with the optics on any telescope it is a good idea to get in the habit of marking the optics so you can return them to the same rotational alignment they were in when you removed them.
Figure 2
Figure 3
Figure 4
Primary Mirror, click the image of the primary mirror above for a full set of actual photos
Centering the secondary after removal
A few months ago I tried to remove secondary mounting ring, the entire assembly moved, not just the retaining ring. So, yesterday I made a trip back to the dealer. Celestron's standard assembly puts the little notch in the secondary directly opposite the focuser. So, it is pointed at *exactly* 90 degrees when looking at the scope from the front. We realigned mine, and then Name-Removed did something very interesting. He took out a digital caliper and precisely centered the secondary. Made sure it was exactly the same distance from the edge of the scope on all sides. Name-Removed told me that these can not be very tightly mounted, as that would warp the corrector and produce bad images. So, they are just another spot that sometimes needs attention in our scopes. When I got home I took it out to see how it looked (painful, as my motor board is off being upgraded). But, it was easier than it had ever been to get precise collimation. Star testing creates identical image inside and outside of focus. There is a definite snap to on the focus. Images were the sharpest I have ever seen them.
Conclusion: Lots of Nexstars get bumped around in their original shipping. Taking the time to precisely center the secondary makes a vast improvement in the image quality produced by the Nexstar 11.
Tip provided by Jim Gutman
Extending the Nexstar11GPS Hand Controller
The Nexstar hand controller is connected to the telescope fork arm via a 6 conductor telephone like cable using an RJ-11 jack on one end. You will want to purchase a female to female RJ-11 plug, then a straight through 6 conductor cable with RJ-11 plugs on each end. Take the controller and plug it into one side of the female to female plug. Take the new straight through cable and plug one end into the same female to female plug you have the controller plugged into. Now take the remaining end and plug that into the jack in the controller nacelle on the fork arm. Remember, if you don't get a straight through cable your hand controller will blow up. You will send it to Celestron for replacement... It is imperative that you maintain the straight through concept of the cables. This tip thanks to Jeff from the Nexstar11 group on Yahoo.
This information has been collected from input from Nexstar11GPS users. Please remember this is an informal collection of data and no warranty is offered. There is no guarantee that this data is even close to correct. Just an effort to post what folks tell me.
If you wish to contribute to this database, please send the serial number, the version of hand controller and motor controller software, and on page 16 or 22 of your manual you will find a "Tip" on how to end slews. Please indicate the page number and if it is down and right, or if it up and right. Mail data to serial@nexstar11.com
| Nexstar 11 GPS Feature vs. Serial |
| number list |
| Serial Number | Hand Controller Version Number | Motor COntroller Version Number | Date Purchased | Tip Information | Year Purchased | ||||||
| 935738 | 1.2 | 1.0 | October | Down and Right | 2001 |
| 935880 | 1.2 | 1.0 | October | Down and Right | 2001 |
| 935963 | 1.2 | 1.0 | March | Down and Right | 2002 |
| 936005 | 1.2 | 1.0 | October | No Information | 2001 |
| 936092 | 1.2 | 1.0 | April | Down and Right | 2002 |
| 936128 | 1.2 | 1.0 | May | Down and Right | 2002 |
| 936260 | 1.2 | 1.0 | December | Down and Right | 2001 |
| 936327 | March | Up and Right | 2002 |
| 936358 | 1.0 | 3.0 | November | Down and Right | 2001 |
| 936408 | 1.2 | 1.0 | April | Down and Right | 2002 |
| 936480 | 1.2 | 2.0 | April | No Data | 2002 |
| 936526 | 1.2 | 3.0 | March | No data | 2002 |
| 936539 | 1.2 | 3.0 | April | Down and Right | 2002 |
| 936669 | 1.2 | 3.0 | February | Up and Right | 2002 |
| 936829 | 1.2 | 3.0 | May | Up and Right | 2002 |
| 936881 | 1.2 | 3.0 | April | Up and Right | 2002 |
| 936910 | 1.2 | 3.0 | May | Up and Right | 2002 |
| 936916 | 1.2 | 3.0 | May | Up and Right | 2002 |
| 936954 | 1.2 | 3.0 | May | Up and Right | 2002 |
| 936972 | 1.2 | 3.0 | April | No Data | 2002 |
| 936975 | 1.2 | 3.0 | May | Up and Right | 2002 |
| Sunday, June 02, 2002 | Page 1 of 1 |
Low rumble when freewheeling in azimuth
When "freewheeling" in Azimuth you may notice a low rumbling coming from the base. Having cleaned the bearing tracks the rumbling continued. After wiping the track again (using a lint free rag with 100% isopropyl), the rumbling was still present. I inspected each of the three bearings and found that two of them had VERY small paint chips on them. I removed said paint chips and all is now well... Glides smooth as silk. Seems like this will end up being routine maintenance.
Tip provided by Jeff Richards
Use of the built in power port for the Nexstar 11
As per Celestron Technical Support, the power port should NOT be used for anything over 750 Milliampere, this is more a rumor than a fact, so my advice is to NOT use it in any way that Celestron does not explicitly tell you to. At least one person had burned up the slip rings by plugging in a Dew Removal system. The scope has a set of Printed Circuit Board slip rings that the rotating portion of the scope connects to. These rings are reported to be very thin. If you put too much power through them you can damage them, and cause anything from total failure, to jerky operation of the Azimuth.
Alternate wedge alignment procedure
The Nexstar 11 GPS offers two alignment procedures when mounted on a wedge. These are known EQ North and EQ South. While these procedures achieve the objective of helping the user to polar align their scope, they walk the user through a number of time consuming steps finishing up with a two star alignment. A major issue with these alignment methods is if the two star alignment fails, the entire alignment procedure needs to be repeated again. In addition, if the alignment is for photography, a drift alignment is still required. Here is a polar alignment procedure that when completed, will be satisfactory for viewing or imaging:
1. Level the tripod _after_ you have placed the scope on it.
2. Power on scope.
3. Ignore the alignment options and press menu /tracking and turn on EQ North or EQ South tracking.
4. Now do a drift alignment. Assuming you have the tripod pointing somewhere near Polaris (Northern) or Sigma Octanis (Southern Hemisphere).
5. The hand controller will still be asking you to select an alignment method. Select two star alignment.
6. Level the tube roughly around the down stop click sound.
7. Select two stars and align. As tracking is still on, centering an alignment star is very easy. If alignment fails select another set of stars and repeat from step 5. It is best to choose two stars with at least 10-20 degrees difference in declination.
8. GOTO what you want to view / image. If the object is not centered in the eyepiece, re-centre and do a realignment (press the align button from the 'Nexstar ready' display). By performing a re-alignment, you can then install a camera slew off to a bright star to focus the camera, and then return to the same spot to image.
Stephen Macmillan smacmillan@qvalent.com
Mounting the Nexstar 11 GPS or Nexstar 8 on the wedge, a better way
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Here is a excellent tip for owners of the Nexstar 11 or 8" scope who want to use them on a wedge and find it very difficult to get all that weight onto the wedge.... Remove the scope from the wedge. Remove the wedge from the tripod and reverse the direction so that the single leg points to the North. This can be easily done and still allow balancing of the scope if you reposition the wedge plate in the second set of holes provided by Celestron on the side castings. Celestron even provide for relocating the deluxe azimuth adjusting knob BUT the knob will run into the fork leg casting at the extremes of its travel. Remove the Deluxe Azimuth threaded rod and knob and obtain a length of 1/4" x 20 threaded rod from you local hardware store along with a 3/4" long 1/4"x20 thread nut that is used for joining lengths of threaded rod. All hardwares stores carry these. Remove the existing threaded rod from the butterfly handle (unscrews if you put the handle in a soft jaw vice and use a vice grip plier to unscrew the threaded rod. Put the new threaded rod in place and thread the 3/4" long nut down to the handle and tighten it. Make the new d exactly as long as the old threaded rod plus the total length of that 3/4" nut. Reassemble. Now, back to that slick tip... Tilt the telescope wedge and tripod (without the scope) over on its two legs until the wedge plate is parallel to the floor. Use a tape measure and measure the distance from the ground to the wedge. Cut a 2" x 2" board to that measured length. Now to operate this simple device just tilt the tripod/wedge over on the two legs and rest it on top of the board using the wedge plates rectangular casing marks to hold it in place. You now have a tripod that is comprised of two of the metal legs and one wood leg. You will now find it extremely easy to lift the scope up onto this assembly. Fasten the scope down with its screws and when done simply tilt the scope back into working position. Reverse for removing the scope. Even with my Meade GFT which sits significantly higher than the stock setup.... It is very easy to mount my N11 on the wedge... In fact it is actually easier than trying to mount the scope in ALT/AZ and trying to find that darn pivot pin. |
Here is another tip; accidently discovered. I had a hand controller that I thought was dead...readout went away and wouldn't move the scope. I found that if you hit the Menu button the display will come back..go to Utility and the option that turns off and on the backlight and turn it off and on...in my case and my friends case (his also acted up) the hand controller came back to life. Think it was some sort of a system crash and the method I used seemed to bring it back to life. Note that while I couldn't get any display to auto start up...when I hit the Menu button that came up.
Yet another fine tip provided by Bob Berta
One of the biggest problems about trying to do daytime viewing of planets and bright stars is getting the telescope aligned. The solution is simple, align at night and keep the scope aligned. I do this at star parties and in my own observatory. The trick is simple, when you are ready to pack it in for the night but want to have the scope ready to slew at a later time simply turn the tracking off. The scope will continue to keep track of the celestial sphere but the scope will no longer rotate, this allows you to cover the scope from the elements. I will typically slew the scope to a good parking position to get the cover on or the observatory closed. To wake the scope up just go back into tracking and turn it back on for either polar or Alt/Az.
Tip provided by Mike Zeidler
Alt-Az tripod mounting tip
For those of you having any difficulty mounting your NS11 GPS scope on the tripod for Alt/Az operation, here's something you can check. I noticed that the locating pin in my tripod could move up in the tripod to gain more height off the deck mounting surface. I raised the pin by loosening the nut on the threaded tightening bolt under the tripod head and turning it higher into the aluminum centre of the tripod. Now the pin shoulder is flush with the deck and the pin itself rises a few millimeters higher off the mounting surface. Now the scope has somewhere to drop after the user locates the scope over the locating pin. What a difference a few millimeters make. The scope sort of snaps into place just like I believe the designer intended. Just take care that when you tighten the nut under the tripod head that you don't raise the shoulder of the locating pin higher than the mounting surface. If you do, the scope will rock on the shoulder instead of sitting flat on the deck in a stable position. Richard Jordan.
T
How to perform a Calibrate Level on the Nexstar 11 GPS telescope