The align dont work and accurate

[hubble space telescope]

Hello everyone

I have the cpc 1100 gps xlt telescope. Most of my observation i use with sky align method, but all the time when i finish the aligning process and slew to a planet, the planet is not in the center of the eyepiece and dont in the center of the findercope and i dont know why. The finderscope and the eyepiece are sync (the eyepiece is in the highest magnification), in the align process i put the object in the center of the eyepiece and the center of finderscope, but when i slew to a planet with the hand control (when the aligning process is finished) the planet is not in the center of both the eyepiece and the finderscope. Now it is okay for a planet because i can see it and i can use the arrow keys to center the planet. But when i will start to watch/image deep sky object i reliant on the telescope that it will put the object in the center of the eyepiece because i can not see the object...
What to do?
Thank you very much! 

[newbie alert]

Is it only on planets or is it out on dso's also?

I'd look in the handset to make sure it's on sidereal rate..i don't use a cpc but the planets are never bang on in the eyepiece,they're never far away..where as the dso's are bang centre most times..

I must clarify that I use a illuminated eyepiece with cross hairs @12.5mm

[ronin]

For now forget planets and goto a star - Arcturus, center that and then goto say Denebola. I would expect the centering to be better. If it is then don't worry.

Stars+DSO's etc have a "fixed" position and the scope can therefore go to them with reasonable accuracy. Planets have a habit of moving round. So the scope has to calculate the plantes orbit/position and then determine an RA+Dec relevant to the Earth. The calculations are subject to an amount of error. Not sure how well the software will handle the retrograde movement of a planet = It nmoves forward, stops, moves backward, stops then moves forward again.

You could find that getting the planet simply in view is pretty good. Have to accept the limitations of the hardware and firmware.

[hubble space telescope]

ok thank you! 

but all the time the planet is not in his first position (first position in the alignment), and i need to re center the planet in the field of view. and the cpc is not on a solid ground and it vibrate from time to time, it is realeted? 

[ollypenrice]

38 minutes ago, hubble space telescope said:

ok thank you! 

but all the time the planet is not in his first position (first position in the alignment), and i need to re center the planet in the field of view. and the cpc is not on a solid ground and it vibrate from time to time, it is realeted? 

If the scope is not on solid ground, meaning the tripod can move even slightly, then you have no hope of precision in GoTo. The GoTo computer is totally reliant on the stability of the mount.

I find that my GoTo scope is far more accurate on deep sky objects than planets but that may just be a bug in my setup.

Olly

[ronin]

Vibration is sort of "normal". You touch it, it vibrates, and the long focal length kind of amplifies this. Drawback of an SCT type scope and the CPC is a big SCT.

The solid ground is a bit more disconcerting, if the legs settle in a bit and do so unevenly then the aiming of the scope will alter a little. Again I would not worry much as I suspect any settlement will be very small. I assume you are not talking qucksand here. Also you should have in the menu somewhere an option to center a target then synch the scope to that target. If effect you center say Arcturus, then tell the scope that it is pointed at Arcturus so it jsut sets it present position to that of Arcturus and goes from there.

You can get antivibration pads that may spread the weight a bit, but they will not prevemt the vibration that you see as that is tube vibration on the mount. But I half suspect that you are not talking about "soft" ground here.

A lot of goto accuracy is based on how well ther scope is set up and a major factor is how level it is in both directions. The scope has to determine the "unlevelness" then apply compensation for it. So in effect the more level at the start the better. Make life easy for the scope.

Have to remember that you are not going to get perfection, all scopes will go to the predicted location then they will usually need some additional fine tuning. Either a human eye ball or a camera and software. Have said elsewhere the processor in these scopes is likely a 20 years old 8 bit device with very little memory = 4k, 8k or 16k, but it will be kilobytes not megabytes and certainly not giga. The processor will not be able to count to gigia anything. It is not an i5 and 100Gb of memory.

 

[Cosmic Geoff]

Don't expect perfection. If the desired object is somewhere in the field of a low-power eyepiece that's a success.  With the Celestron software I have not found the GoTo performance to be any worse with planets than with stars. In fact my standard check in recent months after aligning the GoTo is to command it to find Jupiter, with the expectation that it will appear in-field.

I often find that on using the GoTo to find various objects they are consistently off to one side of the field.

[hubble space telescope]

ok i think i understood!

i will find a way that the telescope will vibrate a little less

i will try 2 star alignment

and dont worry about the DSO because you think that the camera/telescope will catch it in the field of view...

this is good conclusion?

and thank you guys for all your help!!!!!

[hubble space telescope]

My scope is on a in on a stage made of wood and all of my steps are felt. And the problem that you (cosmic geoff), that you the object in the eyepice but not in the center? (did i understand you?) i dont see the object in the field of view...

Hopfully it will work if i will use 2 star alignment or to stabilize the the telescope or really to use in the alignment a different eyepiece...

But thank you all of you guys! It is really help and i really appriciate it!!

[JOC]

I don't know about your own setup, but I know that my own Goto Dobsonian is incredibly sensitive to the weight of the telescope itself.  I've only got to add an hand-grenade style Eyepiece, heavy dewshield, extra finder and the goto motor starts to have problems lifting and moving the telescope.  Clearly if this happens during 'callibrating' the goto unit it might not be accurate.  I would suggest making sure that you only have the telescope in 'manufacturers' supplied kit only - as it came out of the box, no extra stands, gizmos or covers and just an EP it was supplied with.  The before you start the calibration start with the telescope in the position suggested in the book.  For mine this was Pole Star north.  I missed this vital bit of info and had real problems.  Now I start off by finding the pole star in the eyepiece and then lowering my telescope straight down to horizontal.  Then and only then do I click to calibrate on my handset.  I also do it with the scope in 'unfettered' out of the box state, but then I have to remember that every bit of weight I then add might throw things off.  HTH

[hubble space telescope]

Ok, it was really helped!

No extra weight ti the telescope, and in the align to use the north star (polaris) and to find a star close to the horizon?

Thank you!

[spillage]

It may also be worth updating your handset to the latest firmware if yours is out of date.

[JOC]

1 hour ago, hubble space telescope said:

and in the align to use the north star (polaris)

yes

1 hour ago, hubble space telescope said:

and to find a star close to the horizon?

Take a look at your mount, mine has a scale which shows a zero and I align a pointer on the bit that moves to that.  Your mount might have similar, but if not you might be able to use a spirit level or even an app. for your mobile.  Hey, it might not even be necessary for your sort of mount, but surely most of these Goto systems have a similar point of reference?  For the sake of trying I think you have nothing to lose.

Another thing is to make sure you have the date/time/lat-long etc. in the correct format.  The mobile app SynScan Init 2 might be useful to you for the settings.  Things like the dates are often in USA format - month/day/year and not standard UK day/month/year format.  The time also needs to be correct and don't forget you might need leading zeros in the lat/long depending on where you are and you need to make sure you enter East or West and possibly North or South (though you are probably not in Australia and standard North will probably do).  FWIW I have made every mistake listed here - this is def. from one beginner with the benefit of hindsight to another!!  SynScanInit 2 has all the settings in the correct format for my system and I expect yours too.

[alanjgreen]

Hi, As an ex-owner of a CPC1100, here are my alignment tips!

 

1. as said above, the telescope must be on solid ground and the tripod must be level - DO spent time getting the tripod level before mounting the scope

2. make sure the 3 screws holding the scope to the tripod and nice & tight

2. use the right eyepiece. Do not align with the standard 40mm eyepiece, you need much more magnification for accurate centering. I used a 12mm that gave around x250 for the alignment process

2. Never choose planets as alignment targets, they are too variable and introduce errors that results in poor alignment

3. Never use 1 star alignment, it is only accurate in the area around the location of that single star and will be very innacurate anywhere else!

4. Do use "auto 2 star" alignment, this is the simplest alignment and offers decent accuracy. The scope will choose the second star based on the first star that you selected. The choice of stars is IMPORTANT to the accuracy of the result

5. three star alignment is the most accurate alignment but unfortunately is the most fiddly. If you choose stars yourself then they must be at least 90 degrees apart and at least 30 degrees above the horizon. If you choose the wrong stars then you will not get a good alignment. There are apps out there that help you choose the best pairs of stars for the alignment process. Any two stars will not do!

6. always centre stars during "fine centering" by moving them RIGHT then UP (as the final movements). to do this if you move the star to the 7-oclock position in the eyepiece, then you can use one movement RIGHT and one movement UP. Lots of little movements during fine centering introduces inaccuracy! If you miss the centre then go back to bottom left and do the RIGHT and UP once more. (all this helps with the worm gears and replicates the actual RIGHT & UP movement that the telescope will use later)

7. if you have trouble centering the star, then a tip is to "defocus" the telescope slightly to make the star "grow" in the eyepiece. If you grow the star to a decent size then centering becomes much easier as you are just putting a large circle in the centre of a not much larger circle.
 

So having given the tips, this is what I would try this...

1. choose "AUTO 2 STAR" alignment

2. choose "POLARIS" as the first star - its the best choice as it does not move on the sky and therefore gives you time to centre it accurately.

3. perform rough align on polaris with the finder scope

4. perform fine centre align on polaris with a 10 or 12 mm eyepiece (and remember RIGHT & UP as the last movements)

5. The telescope will automatically pick the next star! press ENTER to accept the chosen star

6. The telescope will slew to the star that it selected (and it will miss it by some amount )

7. perform rough align on chosen star with the finder scope

8. perform fine centre align on chosen star with a 10 or 12 mm eyepiece (and remember RIGHT & UP as the last movements)

9. now, alignment is complete

10. test the alignment by using "Named stars" & "Polaris" (or the first star you started with) then let the scope slew to it.

It should be accurate but may not be dead centre.

 

You may need to do it all again, if the 2nd star the scope chooses turns out not to be visible from your location! Just choose a different star at step 5 (use the UP/DOWN scroll buttons on the handset to scroll through the list of 2nd alignment stars that the scope is offering based on your selection of the 1st star of "polaris")

Hope this helps.

Alan

[hubble space telescope]

wow! alan what a beautiful answer! thank you very very much! it really helped! and i really appreciate it!

and just for understanding 10 or 12 mm eyepice is big or small magnification? (i dont understand it well)

and again, thank you very much alan and all of you!!!!

[alanjgreen]

CPC1100 has a focal length of 2800mm

You divide telescope focal length by eyepiece focal length to get the magnification

2800/40 = x70 (40mm eyepiece gives x70 magnification in CPC1100)

2800/10 = x280 (10mm eyepiece gives x280 magnification in CPC1100)

Higher magnification will enable you to centre the stars more accurately.

[hubble space telescope]

got it!

thank you!

[Geoff Lister]

I use Synscan for my GOTO alignment, and have found that, quite often, having accepted the suggested 2nd alignment star, the scope swings round to point directly at an opaque object (house, fence, tree etc.), and I have to start all over again. To avoid this problem, I used "Stellarium" to select a pair of bright stars, easily visible from my patio at dusk, for each month of the year. In most cases, Synscan has my preferred star as its first recommendation, but I sometimes find I have to step through its list to avoid the "invisible" ones.

Before turning ON power, I usually try to set my ALT/AZ mounts level, OTA level and pointing roughly North. It may not be strictly necessary, but it should make it easier for the alignment software's sums, and seems to give very good, long-duration, tracking accuracy, after brightest star alignment.

Geoff