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using 125 without tracking

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#1 dogeddie

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Posted 05 January 2013 - 03:45 PM

I have an ETX 125 and want to use it without the "go to" ability in hopes that astronomy will be more rewarding and exciting as I learn the sky and find targets visually, rather than with the computer's aid or setting circles. Has anyone done this? If so, what is the recommended initial set up procedure? I really don't want to defork it and put it on a GEM. I am also considering removing the LNT module in favor of the right angle finder I have. Anyone experienced anything like this? Thanks for any input.

#2 Christopher Erickson

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Posted 05 January 2013 - 08:18 PM

If you put the scope in polar orientation, you can do this.

However as long as it is in Alt-Az, it has to be aligned with the sky in order to track the sky.

#3 dogeddie

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Posted 05 January 2013 - 08:30 PM

Couldn't you do a quick alignment and basically accept whatever the scope tells you and then manually find stars using just the Autostar directional arrows after that? At that point it should compensate for earth rotation correctly, right? Wondering at what point I know the scope will track objects with the least Autostar input from me.

#4 Christopher Erickson

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Posted 06 January 2013 - 12:23 AM

Couldn't you do a quick alignment and basically accept whatever the scope tells you and then manually find stars using just the Autostar directional arrows after that? At that point it should compensate for earth rotation correctly, right? Wondering at what point I know the scope will track objects with the least Autostar input from me.


A really-rough alignment while in Alt-Az will result in really rough sky tracking.

#5 dogeddie

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Posted 06 January 2013 - 08:12 AM

But if I only need to use it as a clock drive it shouldn't matter - just to keep objects in view?

#6 Christopher Erickson

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Posted 06 January 2013 - 12:56 PM

But if I only need to use it as a clock drive it shouldn't matter - just to keep objects in view?


That's the thing.

When the scope mount is aligned with the celestial North Pole, all it needs is a steady clock drive to keep things in the eyepiece. However when the mount is oriented with the ground in Alt-Az, the motors on both axes must run at different rates, depending on which part of the sky you are pointing at. And that requires math, a microcontroller and an accurate GOTO alignment.

#7 dogeddie

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Posted 06 January 2013 - 05:30 PM

Thanks for the help. So as long as I do a decent initial alignment I can use it the way I explained earlier, without go to - correct? Although at that point not using the scope as it was intended seems kinda dumb. Might make more to look at a different scope for this plan

#8 Christopher Erickson

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Posted 07 January 2013 - 12:55 AM

Thanks for the help. So as long as I do a decent initial alignment I can use it the way I explained earlier, without go to - correct? Although at that point not using the scope as it was intended seems kinda dumb. Might make more to look at a different scope for this plan


Yes, you can slew it around the sky with the buttons on the Autostar and it will track the sky properly. However if you unlock the clutches and point the scope manually, it will no longer be able to track the sky properly.

If you have an 884 tripod, you can put the scope in polar orientation, tell the Autostar you are in polar orientation and then use the scope as you are desiring. In fact you can even loosen the clutches and lock them again without losing the ability to track the sky.

I hope this helps.

#9 rmollise

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Posted 07 January 2013 - 08:20 AM

This is not much of a telescope for this sort of thing. If you want to learn to starhop, get a nice (inexpensive) eight inch Dob. Oh you can starhop with the 125, but it's just not well suited for that. You'll have to have it powererd up and hop with the hand control, really--no slow motions. Having it in EQ mode doesn't help much, either. If you want to learn the sky get that Dob and a pair of 10x50 binoculars.

#10 dogeddie

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Posted 07 January 2013 - 11:51 AM

Thanks all - I have never owned a Dob and don't know much about them. They seem so clumsy. Wonder how set up the base in a foot of snow?

#11 rmollise

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Posted 08 January 2013 - 01:15 PM

Thanks all - I have never owned a Dob and don't know much about them. They seem so clumsy.


One might think. In practice a well-made dob is anything _but_. ;)

#12 dogeddie

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Posted 08 January 2013 - 01:19 PM

For the moment I've decided to try to re kindle my romance with my ETX 125 just as she is :winky:

#13 Christopher Erickson

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Posted 08 January 2013 - 03:47 PM

For the moment I've decided to try to re kindle my romance with my ETX 125 just as she is :winky:


Always best to love the scope you have instead of worrying about the scope you don't!

The biggest challenge for newcomers in enjoying a GOTO scope is figuring out the darned initial alignment. Many of them attempt to do what you are considering, which is using the scope without GOTO. Unfortunately Meade (and Celestron and the rest) don't optimize their entry-level GOTO scopes for this kind of operation.

So what we end up with is a perfectly-enjoyable little GOTO scope with a steep initial learning curve which results in a great number of these scopes ending up in the back of a closet for the rest of their life!

So in conclusion, what I would suggest is focusing on figuring out how to do a proper initial alignment. Once you have done that, using the GOTO function will be an absolute pleasure and not a hindrance.


Some potentially-helpful GOTO Initial Alignment notes:

* Initial alignment is based on True North, not magnetic North. At some locations on planet Earth, the difference can be over 20 degrees!

* Level the tripod/base with a bubble level. Get it close but no need to be fanatical about it. Not mandatory but every little bit helps.

* Daylight Savings Time = Yes in the summer and No in the winter. If you are in Arizona or Hawaii, DST=No all year around.

* Your location should be configured to the nearest city in the scope's database. Up to several-hundred miles off is not a problem for the scope.

* Use your scopes finder and your lowest-powered eyepiece for centering the two alignment stars. Orion (telescope.com) has a nice 20mm crosshair eyepiece that is ideal for really-accurate star-centering. It isn't required but it is a nice accessory. The more accurately you center the two alignment stars, the more accurate your GOTO's will be.

* Planets move and require complicated formulas to compute their current location. Small GOTO scopes use mathematical shortcut formulas. This means that GOTO's to planets will not be as accurate as GOTO's to objects outside of our solar system. This is normal.

* The alignment stars are usually the brightest stars in the general-direction of where the scope is pointing during the alignment process.

* A modern Android/iOS smartphone/tablet running a planetarium program like Astromist, Sky Safari, SKeye, Mobile Observatory or Sky Map can help you properly-identify the brighter stars at night so you can figure out the correct alignment stars. Just point the phone/tablet at the sky and it will show you the names of stars and constellations in that direction. Stay away from large metal objects for best accuracy.

* Always start observing with the lowest-powered (biggest mm) eyepiece you have. Once you have acquired your object in the low-power eyepiece, you can move up to higher-powered ones. The TeleVue Panoptic 24 is a stunning, wide-field, panoramic eyepiece for the ETX scopes. A bit pricey but worth every penny. Stay away from the 40mm Plossl's. In 1.25" focusers, they show you the same amount of sky as a 32mm Plossl, only a lot tinier!



What I do to align Alt-Az scopes for GOTO operation:

1. Make sure to have fresh, quality, brand-name batteries or a proper 9-12VDC power supply.
2. Level the scope base/tripod/pier.
3. Mount scope on base/tripod/pier, control panel/power panel pointed in compass direction indicated by instruction manual. Usually East for an ETX.
4. If the scope has hard stops in the azimuth rotation, Make sure scope base is rotated half-way in between the hard stops.
5. Turn on power.
6. Make sure that you can find Polaris in the sky. It is NOT the brightest star in the sky. Use Smartphone/Tablet, as needed.
7. Ignore display and manually-slew scope to point at Polaris, the North Star. Only use the Up/Down/Left/Right buttons.
8. Center Polaris in the eyepiece and then slew the scope straight down to level. Only use the Up/Down buttons.
9. Use your bubble level to get the optical tube nicely level and then turn off the scope.
10. You are now in the perfect home position!
..........
11. Turn on the scope and feed it your correct Date/Time/DST information.
12. We'll assume that you have already entered your correct location data and scope data. Otherwise enter that data now and go back to step 11.
13. The display should say "Align:Easy".
14. Press the ENTER button to start the alignment process.
15. Read the long scrolling message about initial alignment and home positions, if desired.
16. Press the ENTER button again to skip the message at any time and the scope will slew to the first alignment star.
17. Use the Up/Down/Left/Right buttons to center the alignment star and then press ENTER.
18. Use your smartphone/tablet for star-identification assistance, as needed.
19. You can vary the button-slewing speed on the Autostar/Audiostar by pressing the 1-9 buttons. I usually swap between speeds 9 and 3.
20. Scope will slew to the second alignment star and ask you to center it.
21. Use your smartphone/tablet for star-identification assistance, as needed.
22. Center the second alignment star and press ENTER.
23. If all has gone well up to this point, the scope will display "Align Successful".
24. You are now aligned with the sky!
25. You can now select from any of the objects in the scope's database and press GOTO and the scope will either slew to it or tell you it is below the horizon.
26. Go forth and slew happy, learning the night sky via a great little GOTO scope and your Android/iOS smartphone/tablet!

I hope this helps.

#14 dogeddie

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Posted 08 January 2013 - 04:04 PM

Thanks Chris.

#15 Christopher Erickson

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Posted 08 January 2013 - 04:29 PM

Thanks Chris.


Please let me know if this helps.






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