Hi there I am just new to the Astronomy bug and having just picked up a telescope ( celestron astromaster 130 ) am after the best way to check and align the mirrors. I have watched a couple of youtube clips of a guy doing it with an eyepiece laser which looked easy to me but will this method work on this tele and where is the best place to pick a laser up from to fit the 1.25" eyepiece? I also live on queenslands sunshine coast and could maybe give our local obsevatory a call if they would do it for a small fee chers Andrew.
Hi there I am just new to the Astronomy bug and having just picked up a telescope ( celestron astromaster 130 ) am after the best way to check and align the mirrors. I have watched a couple of youtube clips of a guy doing it with an eyepiece laser which looked easy to me but will this method work on this tele and where is the best place to pick a laser up from to fit the 1.25" eyepiece? I also live on queenslands sunshine coast and could maybe give our local obsevatory a call if they would do it for a small fee chers Andrew.
A cheshire and a laser as you've mentioned will definitely get you started. There are a lot of tutorials online about collimating newtonians. The process is iterative.
1_ center the secondary in the focuser
2_ tilt the secondary so the laser hits the center of the primary
3_ tilt the primary so the laser reflected from the primary hits the center hole of the laser.
4_ Check with the cheshire and go through 2 to 4 again.
If you have joined a club locally many people will be able to advise you and show you how to do it.
Lots of threads on collimation - I suggest that you read up on these.
If you are currently doing nothing to collimate, a cheap laser collimator will make it better. As you will read, both a cheap laser and the technique it uses to align the primary mirror are less than perfect, but much better than doing nothing. And easy as well - in daylight or at night.
Here is a cheap one:-
"Guan Sheng deluxe Newtonian laser collimator" at Andrews Communications:-
Just don't be worried about it too much. There are recommendations that you should check collimation every time you get the scope out. I probably only tweak mine a bit every 5 or 10 times i use it as i have found that it holds collimation well.
If you take it in the car lots or it gets a few bumps when carrying it outside then the mirrors might need a little bit of tweaking more often. Apparently, the smaller the mirrors the less often you should need to collimate.
I've got a Saxon Laser collimator which i bought from Star Optics on the Gold Coast but you can buy them online for about the same or less. It's a good tool to get it 'about right'. I've also recently started using the 'star' method for collimation and that seems to work well too.
I have found for more serious collimation I watched a series of Youtube videos from http://www.youtube.com/watch?v=zd-fl9SEYHw about 9 parts. Way over the top for a lot of visual observing but does say that. What I found though was I helped me under in a lot of detail about the Newtonian and how it works.
I have found for more serious collimation I watched a series of Youtube videos from http://www.youtube.com/watch?v=zd-fl9SEYHw about 9 parts. Way over the top for a lot of visual observing but does say that. What I found though was I helped me under in a lot of detail about the Newtonian and how it works.
I watched all 9 videos. The video is missing the part about how to align the focuser axis which can be accomplished by either:
1- Fine tuning the secondary mirror to redirect the single laser beam to the primary center or
2- Fine tuning the secondary mirror to align the primary center spot with the sight-tube cross hairs
In addition, the video shows the primary mirror being adjusted when the OTA is at horizontal position -- not a good idea. It is recommended to have the OTA at around 60 degrees when the primary mirror is adjusted
Jason
I watched all 9 videos. The video is missing the part about how to align the focuser axis which can be accomplished by either:
1- Fine tuning the secondary mirror to redirect the single laser beam to the primary center or
2- Fine tuning the secondary mirror to align the primary center spot with the sight-tube cross hairs
In addition, the video shows the primary mirror being adjusted when the OTA is at horizontal position -- not a good idea. It is recommended to have the OTA at around 60 degrees when the primary mirror is adjusted
Jason
With those twist clamps for lenses, the focuser adjustment is not much of an issue, I will be buying one of these later and will check.
There are a couple of things I would do a little differently, for primary adjustment placing in both horizontal (near enough to) and 60deg is a good idea for both. Only recently I was checking mine and picked up a set-up error with my scope checking both, but I think it was also placed horizontal to allow better youtube instruction.
Although mostly not for primary adjustment it is good practice not to tilt a newtonian above 45deg as it is possible for things to fall or be flicked in and potentially damage the mirror. I think that was mentioned in the video although I do remember this being a concern before watching the video.
I'd be interested in knowing why you would put it at 60 deg and not lower?
With those twist clamps for lenses, the focuser adjustment is not much of an issue, I will be buying one of these later and will check.
Focuser axial alignment is about eliminating tilt between the primary mirror and eyepiece focal planes. This can only be accomplished by adjusting the secondary mirror. I have described the two typical methods used to complete this alignment in my previous post. This alignment is completely missing from the video. The "Precision Centering Adapter" shown in the video has little to do with this alignment.
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There are a couple of things I would do a little differently, for primary adjustment placing in both horizontal (near enough to) and 60deg is a good idea for both. Only recently I was checking mine and picked up a set-up error with my scope checking both,
Aligning the primary mirror with the OTA in horizontal position can be problematic since primary collimation might shift substantially after the OTA is raised.
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but I think it was also placed horizontal to allow better youtube instruction.
The presenter could have said something to this extent.
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Although mostly not for primary adjustment it is good practice not to tilt a newtonian above 45deg as it is possible for things to fall or be flicked in and potentially damage the mirror. I think that was mentioned in the video although I do remember this being a concern before watching the video.
The primary mirror adjustment takes place at the rear end of the scope. Dropping objects on the primary mirror should not be a concern. For the secondary mirror adjustment, Bob's knobs could be installed to reduce the likelihood of dropping objects.
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I'd be interested in knowing why you would put it at 60 deg and not lower?
The 60 degrees is only a guideline -- not a rule. It is recommended to collimate around halfway of the user's observing ALT range. Typically, that would be between 40 and 80 degrees. 60 degrees happened to be the halfway point. Again, this is only a guideline.
okay I picked up an Antarese laser collimator and it was so easy to use until i excitedly went out to view at night to find it totaly out by a long way. I made sure the collimator was collimated and it was spot on but how can it be not right. The laser was an inch off dead center befor i collimated it and now i have gone back to the film canister method and everything is dead center now but when i put the laser in it is an inch from the main mirror center mark. Is this my celestrons 130,s sweet spot or is the laser just crap!
I did as per instructions which says to make a 90 degree corner box to sit it in and turn it on facing a wall and then slowly rotate it. i had a 3m distance to the wall and the laser did not appear to move more than 1-2mm vitually un-noticable. maybe my celestron is not well designed enough for a laser but the film canister seems to work great.
voitty,
You seem to have a misaligned secondary mirror and a well aligned primary mirror. In this case, the film canister will give good results but the laser will not. The laser collimator is sensitive to both the secondary and primary alignments.
Try the following:
1- Adjust the secondary mirror to redirect the forward laser beam to the dead center of the primary mirror spot. This is an important step. Do take your time to ensure the forward laser beam is centered. If there is too much laser glow, shining a flash light on the primary mirror will reduce the laser glow.
2- Adjust the primary mirror to ensure the returning laser beam retraces its path all the way back to the source.
3- Do NOT alter the OTA ALT angle. Remove the laser collimator and insert the film canister. Does it agree with the laser now?
Jason
I am not sure what you mean as it can only be done one way. i put the laser in, turn it on and adjust the secondary to hit the center of the primary than look at the target on my laser and adjust the primary, When that is dead center i go back and check the laser on the primary and its still spot on but looking through it at night or a well lit wall shows that it is way out from center so i am very confused. i even set it up a second time as per instructions which say focus on a planet like jupiter and dont adjust then stick in the laser whith the same results.
If the focuser an the secondary mirror are not aligned then the whole initial alignment is null and void.
Not only does the secondary align to the centre of the primary it also moves to allow the secondary rotate around to look like a perfect circle from the focuser. It is this alignment. As shown in the Youtube link above notice he placed the red card behind the secondary and blocked the primary path with the blue card. This is the easiest way to see the perfect circle of the secondary through the focuser. This cannot be tested with the laser. The red card shows the outline of the circle easier.
There are other methods but this one is the easiest to visualise.
If there is some that can help might be the best way.
voitty,
Let me make sure I understand. You followed the proper steps to collimate your scope using an aligned laser collimator but the results disagree with the film canister by a noticeable amount. You are trying to find the source of the discrepancy. Is my understanding correct?
Can you quantify the film canister error? Is the film canister pupil reflection still within the primary mirror center spot perforation?
You were not referring to the secondary mirror edge as seen from the focuser, were you?
There are 3 distinct collimation alignments. Two have to do with the secondary mirror and one with the primary mirror. You can read the following post to understand these 3 alignments and their impact: http://www.cloudynights.com/ubbthrea...b/5/o/all/vc/1
I read your original post again. You do seem to reference the secondary mirror edge. Check out the attached animation. The laser collimator will hit the primary mirror center and the return beam will hit the laser collimator bullseye center for each frame yet each frame includes a different position for the secondary mirror. Do read the post I referenced in my last post. There are 3 distinct and independent collimation alignments. The laser collimator only covers 2 out of the 3. It does not cover the optimal positioning of the secondary mirror under the focuser. But this is the least critical alignment. It deals with what is referred to as “field-edge illumination” -- read the referenced post. I am including another animation to illustrate how a mis-positioned secondary mirror impact the view. Bear in mind the animation exaggerates the impact for the purpose of illustration.
So, in your case you can use the film canister to center/round the secondary mirror under the focuser. They you are done, use the laser collimator to further fine tune the secondary mirror followed by the primary mirror. That should take care of all 3 alignments.
I did watch all 9 videos and like this guy i am very fussy and like things spoy on. I didnt realize that the secondary moves in and out and twists as well. i did the coloured card trick and got it pretty close now. i have a problem that the 3 secondary adjustment screws are not long enough as i need the secondary to go back another 2-3 mm to get it dead center but like i said its very close now so i will live with that, maybe if I ever get a bigger,better scope it will have better adjustment for this.
Over time you will find small adjustments that make improvements as you go, it is nice to go at it whole hog but realistically time is the best key. I don't know how your scope performs but over time you may find this out.
Atmospherics play a big part in what you see as far as focusing as well. In my time taking photos it is only the last 2 months that I am starting to achieve good results, also in my time about 2 percent of my whole observing time I have achieved good focus due to atmospherics especially on planets.
