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Beginner's Go-To Mount Question


Tim99
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I have had my new CGEM and Celestron Edge 9.25 out twice now.  The first time out, I was able to align and had the mount tracking the moon.  Last night, (new moon) so decided to set up and go-to the Andromeda Galaxy.  

The new Polar Scope was handy for Polar Alignment although after dark, it was impossible to see the etched reticule.  I ended up shining my small red-light into the hole in the mount and got it just right to see the reticule and Polaris.

During two-star alignment, it was had to see the star in the stock finderscope.  (Any suggestions on replacing that stock finderscope?)  What about using an Illuminated Centering Eyepiece?

Two-star align achieved (I think) and one calibration star.  Then, I selected Andromeda on the hand controller, hit enter and the scope began to slew toward the correct area of the sky.  It slowed and I thought, "Wow!  It's working!"

I looked into the eyepiece and ... no Andromeda.  Looking through the finder scope and Andromeda was at the 2 o'clock position.  I used the hand controller to center Andromeda in the finder scope then looked in eyepiece and there it was.  

NOW FOR MY QUESTION:  Now that Andromeda is centered in my eyepiece, if I go-to another object, will that object be found or am I off by the same amount as I was for Andromeda?    Should I have started over and done another two-star alignment etc?  

I know this question is so basic but I am trying to understand how the CGEM thinks.  haha

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Hi,silly question,is your finderscope aligned to your eyepiece? Also when doing a 2 star or 3 star alignment pick stars that are on one side of the meridian for the first 2 stars and then 1 star for the other side of the  meridian,this will help with pointing accuracy.Another feature which you can do is a re-alignment,this will improve your pointing accuracy especially in that part of the sky.As for the polar scope sorry can`t help there as I just roughly point at Polaris.....Just a thought are you using DAYLIGHT SAVING??? Your time might be out by an hour or so.If it happens again,start again  from basics,with the manual,this helped me. Des

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Hey des !    Thanks for the reply.  Yes, I aligned the polar scope when I installed it.  (I think... ha)  The CGEM suggests stars for the 2-star alignment so I just use them.  I did notice for the calibration 3rd star the mount moved to the other side of the Meridian.  Yes , I set Daylight Savings in the hand controller.

Going through the manual "again" is probably a good suggestion.  I got the mount to at least slew to the right ball park for Andromeda.  Ha.   Maybe just refining the process is what I need to do.  I think that I am on about plateau #3 in the learning curve with about 200 levels to go before I can start imaging!  But, it is all enjoyable.

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When doing your star alignment, always end the fine movement with the same two arrow keys; skywatcher say the up and right arrow - this is to mesh things the same way each time to reduce backlash interferring with the alignment. Also if you have a zoom eye piece, centre with the low magnification first, then zoom in and re-centre again, ending with up and tight, then press enter to accept the alignment star(s). I use a 12mm reticle eye piece for my alignments and usually put it in a 2.5x powermate once i've done the alignment once to really get things tight.

James

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Hi,silly question,is your finderscope aligned to your eyepiece?

Yes, I aligned the polar scope when I installed it.

These are different steps. Des is on the right track.

Tim, you need to confirm that the finderscope is aligned with the view through the eyepiece. This is a step best performed during the day, using a streetlight, or other high/distant object (but not the Sun of course).

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Yes, you need to:

- align the polar scope with the RA axis of the mount, as well as

- align the finder scope with the field of view of the main scope

But these two alone or in combination don't determine the accuracy lf your GOTO alignment when setting up. Poor polar alignment will degrade your GOTO accuracy eventually but will take an hour or so, though does depend on how badly you've polar aligned.

James

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Thanks BeanerSA and jambouk.   When I got the Polar Scope, I adjusted the little screws to get it aligned with the RA axis of the mount.  I took the scope out during the daytime and also made sure my finder scope and main scope were zeroed in.  

The problem I seemed to have when I took the telescope out at night was being able to look through the finder scope and find the star that I was supposed to be centering for the go-to alignment (2-star align procedure).  The stock finderscope does not have an illuminated reticle and it was hard to know whether I was centering the star or not.  I thought, there has got to be a better finderscope for my SCT.  I have a red dot finder also but I had the same problem lining up with that because there is no magnification to help me see the star that I am trying to center on.  Do you know what I mean?

On my ES 80mm Refractor, I have an illuminated Finder Scope that works very well on that little scope.  The problem with the Celestron SCT is that it is big and sometimes it places the finder scope in an awkward position to look through.  I researched a little and see that Celestron makes a right angle - illuminated finder scope.  Maybe that's what i need.  Any suggestions?

My thinking is that if I have a good Finder Scope and perhaps an eyepiece with reticle, maybe I can do a better job of centering my stars.  

As I am a beginner, I am literally taking a shot in the dark here!  Ha.

I appreciate your suggestions

Tim 

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Hi Tim, 

Skywatcher makes an illuminator for their viewfinder [1]. I do not know CGEM, but maybe it would fit to there is a similar part for it? With the polar scope of my GP came a similar device that looks like [2], basically a plastic piece with a small fiber into which you put a small red flashlight. Those are relatively cheap and work well. I do not think that you need to get a new polar scope just for illumination.

On a related note, if you have a camera, you might want to consider a software solution to align you scope. There are quite a few out there that guide you through the process without the need of kneeling before your polar scope (basically some variation of drift align). Also, I would check if there are software methods available for n-star alignment for the CGEM. That would also give you a simpler way to proper goto-performance. 

Sven

[1] http://www.teleskop-express.de/shop/product_info.php/language/en/info/p7086_Skywatcher-Polsucherbeleuchtung-fuer-EQ3--EQ5--Star-Adventurer---.html

[2] http://www.philoktetes.de/files/polsucherbeleuchtung.jpg

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Tim,

I'm at about the same stage in my astro journey as yourself and one of the most frustrating things I've done to date is aligning my polar scope to my mount. I've downloaded and perused heaps of 'instructions' and was getting nowhere, fast. I'm guessing, in my inexperience, that from your description above you may not have your mount correctly aligned.

Your mount seems pretty much the same as my EQ6 so the polar scope alignment routine should be the same. This is the routine that eventually worked for me.

Due to the lack of illumination in your polar scope you've already sussed out that this is a daytime job plus it is a whole lot easier to find the grub screws with the allen key in daylight. I actually did this exercise inside with a 2mm dot on a sheet of paper but hey, get out in the fresh air.

This is probably best done without your scope mounted.

1. Remove the front and rear covers from your polar scope, drop the counterweight bar and rotate the DEC axis till you have a clear view of the reticle.

2. Use the altitude and azimuth adjusters to centre your target on the scope cross-hairs.  Now rotate the RA axis 180° and if the dot is still centered no further adjustment is necessary and you should go buy a lottery ticket.

3. If the dot has wandered off centre when you rotate the mount 180°on the RA axis we now come to the fun part. Using the three grub screws, move the dot half way back toward the centre of the cross hairs. Unfortunately I can only suggest trial and error here as to which grub screw to use but I found that I had to back off two grub screws to adjust with the third one. Use only about I/4 of a turn max on the allen key at this point.

4. When you have done this return the mount to the upright position and using the altitude and azimuth adjusters re-align the dot onto the centre of the cross hairs.

5. Now swing the mount on the RA axis 180° in the opposite direction and using the grub screws again adjust the dot 1/2 way back to the centre of the cross hairs.

6. Swing the mount back to upright and hopefully at this point you are getting pretty close to having the dot centred. If not, repeat the above procedure of alt/az adjustment and swinging the mount both ways on the RA axis and use just tiny adjustments of the grub screws till your target  does not move off the centre of the cross-hairs.

The thing to remember is to use the ALT/AZ adjusters when the mount is upright and the grub screws when it is inverted.

If you have followed this procedure I apologise for my unnecessary post.

Good luck and clear skies.

PS: I eventually put an 'O' ring onto the reticle holder to stop it falling out of place during my early ham-fisted attempts at adjusting the grub screws.

Edited by DarkKnight
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Sven and Dark-Knight, My reading of Tim's post is that he has ssirted the Polar Scope issue, but would like an Illuminated finder scope.

I don't think, i've ever been anywhere dark enough that I can't see the cross hairs in my finder scope, or maybe I have just never noticed.

Is the finder scope a skinny one, or a 9x50? I'd recommend getting a 9x50. There are right angled versions. Orion optics do a finder scope with takes 1.25" eye pieces so you could drop in an illumminated recicle eye piece into that.

On my sktwatcher mount, if I get the mount in the home position before i start doing any star alignment, when i pick the first star to align on the scope takes itself to that star pretty accurately, it may be a case using the finder scope to get the star roughly centred, then swapping to the eye piece to check if it is then in the field of view, and centring.

I've not used your mount, but i think that maybe is doesn't slew itself to the first star, and that the user has to do this, am i correct? If so, pick a bright star well away from the milky way, so not deneb or vega or altair, as there will be too many background stars. Depending on your horizon go for something like arcturus, dubhe, or something due south or south east. If you struggle to look through the straight-theough finder scope, pick a star low down so the angle is better for your neck, back and knees :) getting the first star nailed will be the key. After that I suspect when it slews to the second star it will be much easier.

Also, aligning the finder scope and the main scope in day light is good, but you'll need to refune the alignment at night on something truely a long way away; polaris is good as it doesn't appear to move much. Make sure you are using the lowest power eye piece when aligning to start with, else you'll have an even narrower field of view when looking the scope.

So, hunt down a second hand right-angled 9x50 finder scope, i don't think you need an illuminated one, and even if you do it is easy to sell on 9x50 finder scopes second hand, refine the alignment of the finder scooe with the main scope at night when setting up, and pick a first alignment star which doesn't have too many background stars. You'll crack it.

James

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