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A quick collimation question.


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I have a SW 130pds and a Baader MkIII laser collimator. The tool is really easy to use and I know what to do in regards to adjusting the scope but my question is in regards to aligning the tool. I have to put the tool into the 2" to 1.25 adaptor, the instructions state that if you have two screws then align the small white dot on the tool centrally to the screws. So I did that but then where does the adaptor align with the other two screws on the 2" focuser ? as it makes a difference in collimating as to how this all lines up. Thanks in advance.

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I tend to have two screws on one side and two on the other. That said if you collimate each time as you should then it won't really matter. The secondary adjustment has a very minor impact on image quality and you cannot align the secondary in the drawtube with a laser anyhow unless you use specific methods involving bespoke templates.

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I'm not sure I'd worry too much about it either.

I imagine they are trying to compensate for the slight amount of play there will be in the adaptors themselves.

If you try to put the adaptors in the same way each time, what ever way that is and whether observing or collimating, then there shouldn't be a problem.

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10 minutes ago, Moonshane said:

I tend to have two screws on one side and two on the other. That said if you collimate each time as you should then it won't really matter. The secondary adjustment has a very minor impact on image quality and you cannot align the secondary in the drawtube with a laser anyhow unless you use specific methods involving bespoke templates.

I'm not sure what you mean in regards to not being able to align the secondary in the drawtube with a laser!!? 

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9 minutes ago, Rustang said:

I'm not sure what you mean in regards to not being able to align the secondary in the drawtube with a laser!!? 

To get the secondary centred under the focuser you have to look down a sight tube (any cheshire with a long tube is a combined cheshire and sight tube) to make sure that the secondary appears to be central and circular. The laser can be used to align the angle of the secondary so that the laser hits the centre of the primary mirror, but that is the second of the two secondary adjustments.

With regards to the position of the 1.25" adaptor and the 2" focuser, have the adaptor in the position that you have it when you are using the telescope.

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4 hours ago, Rustang said:

I have a SW 130pds and a Baader MkIII laser collimator. The tool is really easy to use and I know what to do in regards to adjusting the scope but my question is in regards to aligning the tool. I have to put the tool into the 2" to 1.25 adaptor, the instructions state that if you have two screws then align the small white dot on the tool centrally to the screws. So I did that but then where does the adaptor align with the other two screws on the 2" focuser ? as it makes a difference in collimating as to how this all lines up. Thanks in advance.

Hi and welcome to the PDS club :)

My first point, - Keep in mind, that a slight mis-collimation of the primary is not a big deal, especially if you use scope for visual only. In this case do not worry about these slight differences you have while lazer is placed in a different manner.

I mean, if you turn around or remove and place back your laser and it shines somewhere around the central Doughnut of the primary, - you are OK.

Laser is a nice tool to adjust collimation of the primary fast and the 1.25" ones are simply not able to be 100% precise.

I personally, do not lock laser or Cheshire in the EP holder, it simply makes no sense, as while you lock it, you tilt it accordingly, - next time you tilt in a different manner and etc...

Just collimate while EP holder is at 12 o'clock (if possible) and let the laser rest under the gravity and try turning it 360 degrees

you will notice, it will change the position of the laser beam and there is no difference how you place the 2">1.25" adapter.

If laser travels just around the doughnut of the primary, - you are OK. If it stays inside all the time, - SUPER!

Yes, F5 is quite sensitive and a slight wobble/Tilt in the Eyepiece holder produces different results, but the main pain is the Secondary mirror, - not the primary.

If you have not yet touched the Central bolt on the Secondary, - do not touch it, unless you will notice your stars are getting bad and you have to.

Proper adjustment of the secondary is a real challenge. But laser will not help to deal with it, you will need Cheshire... 

All videos and manuals, who show how to use laser collimator, never tell you, - DO NOT touch the central bolt of the secondary and if the 3 surrounding bolts are too tight and you simply cannot turn them and you are made to loosen the central one,

do it, BUT very, -  VERY VERY slightly. 

If you have loosened your central bolt of the secondary already, I am 100% sure you will not see 3 Primary mirror holders in the Cheshire and the collimation of the secondary is Off.

However 

Even if it is off, but stars (also star halos, - if you imaging) are round, if you do not notice any coma, if star spikes are symmetric, - enjoy and do not worry.

If you do feel something is wrong, - collimate as best as you can and do a star test (with the bright  unfocused star, it will show if something is not aligned).

If all bad and you feel you need to challenge the secondary mirror, -  the Tilt/Wobble of the Cheshire in the EP holder will be your first enemy...

As far as I have managed to learn during last 2 years of my collimation experience, were are several ways to combat the tilt/wobble in the EP holder:

(And do not get me wrong here, - 2 years means, I am still only learning :) )

1) Throw money at it - :) (usual solution in this hobby), there are 2" collimators, so you will not need to use 2">1.25" adapter which causes the problem and you will have no wobble/tilts, but the price is close or even higher than the PDS itself;

2) Throw a bit less money at it - there is a "toy" called Howie Glatter Parallizer - which was around £39 previously.... Now it is £59... not sure why it is growing in price... Maybe some cheaper analogs are  somewhere on the marked, - I could not find them.

3) DYI - nothing special, just try a tape around the lazer or cheshire, not very reliable, but why not to try before throwing money away, you may be lucky and hit the Spot On position from the second or the 3rd time;

 

 

 

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