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After a 2 star alignment with 2 stars 90 degrees in the sky apart, I input coordinates or an object choice. The telescope slews toward the object but is off about 2 degrees. If I ask the telescope to slew back to one of the original alignment stars it misses that star by 1-2 degrees as well.
If I center an object - say M57- in the eyepiece, then press the hand box button to get a "precision alignment" it the obkects tracks perfectly, but if I slew away even a few degrees and ask the telescope to recenter M57 then I am off 1-2 degrees again. I'm stumped.
I've looked at the obvious; loose worn stripped gears, grease on the LED optical encolders, etc.
Do you think my problem is mechanical or electronic with the GOTO?
Most problems tend to be mechanical. Have you 'trained' the drive and set the backlash values? Those 2 can have dramatic effects on pointing accuracy. Also, if the optical tube is not in alignment with the mount, then nothing will work correctly. To check that, have the telescope in Alt-Az configuration, inside the house, loosen the RA lock, and shine a laser pointer on the corrector plate. as the telescope is rotated about the RA, the reflected spot should be steady. Adjust the DEC to minimize the diameter of the circle that is drawn. What is left, is the out-of-true on the DEC axis. That can be adjusted with the tube cradle alignment bolts.
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Aligning a scope requires several things to be correct.
1. You must follow the setup in manual 100%
2. You must pick the correct alignment stars. Most failed alignments are because you aligned on the wrong star. So alignment requires you to learn the names of a few bright stars and be able to spot them in the sky.
3. With many goto scopes there might be a "home position" to start the alignment. For example, tube pointed roughly North, and level. Check your manual for a "home position. Also time, date, and site must be correct.
Clear skies,
TelescopeMan
www.telescopeman.org and www.telescopeman.info
First the good news. Personally I believe a computer GOTO scope or a Dobsonian telescope with PUSHTO makes a great telescope for a beginner.
Why? Because you can use the hand controller to help you find those dim sky objects that are almost invisible from a typical suburban observing site with lots of light pollution.
Also if you pay attention you will learn many of the brighter stars in the sky, the Constellations, and the location of many of the brighter sky objects.
Now for the bad news. There are many cheap goto telescope systems being sold that do not work as advertised, and you still need APERTURE to see many of the dimmer sky objects. So a goto with a little 70mm refractor mounted on it will frustrate you!
Right off the bat let me list a few links to the better goto and pushto telescopes. See these web sites:
http://www.amazon.com/dp/B0023RRD9Y/ref=asc_df_B0023RRD9Y994674?smid=ATVPDKIKX0DER&tag=googlecom09c9-20&linkCode=asn&creative=380341&creativeASIN=B0023RRD9Y This is just the mount, you need to also buy the telescope tube. I would suggest a 6 inch Celestron SCT Optical Tube Assembly (OTA), and also what is called a "dovetail" metal bar to mount the scope tube onto the side of this goto mount.
http://www.celestron.com/c3/product.php?CatID=11&ProdID=392 This is a computerized equitorial mount. It works differently than the scopes listed above.
That should be enough to get you thinking! All of the ones listed above will have good goto performance IF:
You read the manual TWICE!
Test the scope out INSIDE in the light before you take it out at night and learn how to operate the hand controller.
Follow all the instructions in the manual about training the drives and or calibrating motors.
Accurately center BOTH alignment stars. Yes you will need to learn the names of a few stars in the sky.
AND NEVER plug or unplug the hand controller while the scope is turned on! This can burn out the circuits in the scope!
I would suggest that your first goto telescope be like the very first link above; a Dobsonian with a PUSHTO hand controller. This is the cheapest and best entry point to own a computer telescope. Yes, the prices are a little higher and old timers will tell you you do not need the computer goto to find objects in the sky.
I disagree! Beginners get very frustrated with the hobby when they cannot find anything other than the moon or several bright planets; or search for several hours to find one other dim sky object. Also most of us live in light polluted cities, and hopping around from star to star to find something is not really possible.
Add eye problems like cataracts and you will only see 6 or 7 stars in the sky, not enough to use to find other sky objects.
If you decide to buy a GOTO scope, please attend several star parties at your local Astronomy club. Many of the members will have this kind of telescope. You can ask questions, and they may even let you DRIVE the telescope!
Remember, READ the manual, train the drives, and do all the other initial setup that the manual recommends. Yes, you will need to know the names of a few bright stars in the sky! Your new computer telescope is not as smart as 3CPO in Star Wars!
Once the scope has taken a GPS fix and knows TIME, and SITE, and you do a two star alignment your alignment stars overide any automatic alignment issues.
You could turn off the GPS put in Time, Date, and Site, do a two star alignment and everything would be fine. Centering the alignment stars is the "trick". Apparently the scope also finds NORTH OK, or the alignment stars would be way off. Since you pre-level the tripod already the software can FAIL on "tilt" and you still get good gotos.
I would not worry about it, especially since your gotos seem perfectly fine.
You will NOT be able to locate those stars at the exact coordinate given for them. This is a scam.
While it might make a nice gift, we recently tried to locate a gift star using our Astronomy club's 16 inch computer GOTO scope. NOTHING was at the location in the sky.
Sorry but other than a "nice" gift you will not find anything in your 4.5 inch scope.
PUSH TO -- encoders can be mounted on to the base RA and DEC. After aligning on two known stars the hand controller will "point" to objects in the sky.
Did you calibrate the motors and TRAIN the drives? If not do these first--
During alignment the "alignment" stars may or may NOT be visible in the eyepiece-- CENTER the star. Once you do this with two stars your gotos should be good.
This makes sure that the scope is calibrated properly.
Do an AUTOMATIC ALIGN
when asked to center star, look for the BRIGHTEST star that is close to the scopes field of view. It will be that star you need to used the arrow keys on to centre it in the scope eyepiece and press enter.
This star can be as much as a HANDS distance away from the centre of view
If you cannot identify the star it is asking you to use, press the SCROLL DOWN key to choose another star, keep doing this until you see a star you recognise.
That's it!
You can also hold down the MODE key for about 4 seconds and scroll through the scope info. Make sure you have the correct location coordinates ( Lat/Long) and the correct time set.
Select a bright object first such as a planet and GOTO it. Once you have manually centered it in the eyepiece, press ENTER and hold it for 6 seconds, the handset will say " Press ENTER to sync", press enter and you have updated the scope with the coordinates of that object.
Do a FAKE alignment-- (I assume that the scope is trained and has the proper date, time, and site)-- just push the buttons for the alignment stars that you cannot see. Then do a GOTO to a star that is in your field of view--- center the star and SYNC. Your gotos will now be OK in your limited field of view.
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