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Newbie collimation Question

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#1 Tdj873

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Posted 15 July 2020 - 12:39 AM

I recently purchased an Apetura DT6 after using a 70mm refractor for around two years. 

 

I have read everywhere that most scopes come from the factory pre-collimated, but when I look through the focused tube by itself, nothing seems to be aligned with the primary mirror dot. 

 

Does this mean the primary is out of collimation? I have looked at multiple how-to-guides on collimation, but I'd be lying if I said I wasn't a tad overwhelmed by it all. I bought a sight tube/ Chesire combo, but I am having trouble distinguishing the differences between what I see in my scope and the illustrations that most guides provide.



#2 sg6

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Posted 15 July 2020 - 02:01 AM

Persoanally I would leave it and take it outside and look through the scope first. You have Jupiter and Saturn as targets and should provide a good indication of how well or otherwise the scope is performing.

 

Also gives you a bit of time to think about it all.

 

Everytime someone says they have a newtonian almost the first response is collimate it. Have no idea why.

 

As you look down the focuser you have no guarantee of your eye being in the right position and as everything concerns angles I would doubt you see everything, or anything, in good alignment. Especially where reflections are concerned.


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#3 Sorana

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Posted 15 July 2020 - 04:55 AM

Hello! Newbie here also with telescopes, so take everything with a grain of salt.(I just got mine yesterday)

Does your manual include collimation instructions? After assembling it I decided to check the collimation (I don't have a collimation cap or anything so I just did it by looking with my eye) and following the instructions in the manual:

1. Look (either with a collimation cap or with your eye) through the focuser: (I don't know how to upload images so here you go - https://imgur.com/a/qcvxBoO, fig d - needs adjustment, fig e - the secondary mirror is properly aligned ). If you can't see the three clips - the secondary mirror needs adjustment (look in your manual)

After either is good or aligned it properly you want to look at the primary

2. Look through the focuser (https://imgur.com/a/HqO736V). If it's like the last two images, than the telescope is collimated, if not, again, use your manual. If the image is similar to the first one, than it needs collimation.

 

I did this in daylight so it would be easier. At night I looked at a star out-of-focus to see if it's collimated or not (you can also do this first, I just had some time in the afternoon and decided to look at it in daylight)(https://imgur.com/a/zOfDtKG)

 

Here are some readings that helped me as well:

https://nimax-img.de...Collimation.pdf

 

the collimation instructions from my manual: https://www.apm-tele...tcher/en/47.pdf

 

Personally, mine was perfectly collimated! Hope this helps


Edited by Sorana, 15 July 2020 - 06:10 AM.


#4 sixela

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Posted 15 July 2020 - 06:02 AM

I recently purchased an Apetura DT6 after using a 70mm refractor for around two years. 

 

I have read everywhere that most scopes come from the factory pre-collimated, but when I look through the focused tube by itself, nothing seems to be aligned with the primary mirror dot. 

 

Most things close to it are not supposed to be concentric with it. You need to insert a collimation cap or Cheshire to see _something_ (i.e. the pupil or reflection of the Cheshire ring) that you can compare it with. The other things that need to be concentric are the edge of the primary's image (duh! otherwise it's not a centre spot) and the inner edge of the focuser tube, but good luck evaluating that (and if you don't have a perfectly centred pupil even that does not hold, hence the need for a collimation cap).


Edited by sixela, 15 July 2020 - 06:03 AM.


#5 moonrakercat

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Posted 15 July 2020 - 06:23 AM

Hi & Welcome to the forums !  Hope you enjoy your new 6" dob !    You're going to have to learn about lining the mirrors up - it's important for good views - it does not have to be perfect.  Yes it can be confusing- I know.  

 

For about the first 15 years of astronomy I struggled with collimating my dob with a cheshire.  

 

There are many, many websites out there that try to explain collimation - but so many are really confusing - imho anyway.

 

You might try this link - about 1/2 way down page there is an illustration showing 3 easy steps - this page helped me greatly to understand how to collimate using a cheshire. 

 

https://skyandtelesc...ctor-telescope/

 

Then about 6 months ago I bought a meade laser collimator - cheap - I think I paid about 60.00 cdn for it - one of the best purchases I've made regarding astronomy.   You can align your mirrors in a few minutes - and so much easier and accurate to do rather than a cheshire. 

 

Hope this helps !



#6 rhetfield

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Posted 15 July 2020 - 07:58 AM

I am a big fan of these two articles:

 

https://garyseronik....to-collimation/

 

https://garyseronik....pe-collimation/

 

The first article covers how to do the initial primary and secondary collimation using tools (primarily a collimation cap).  The second article covers how to use a star to do the collimation fine tuning that is needed to optimize performance.  Both are necessary.  The tools will get you close, but they are not perfect.  Often, the center donut is not perfectly centered or the mirror's physical center is not the same as optical center.  The end goal is to make the stars look good - which is why the star collimation is a must.


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#7 Tdj873

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Posted 15 July 2020 - 12:01 PM

Thank you all for the help! I think I finally got It down. I will check it tonight with a star test.

One small question though. Is it normal to have to do large adjustments straight from the factory like this?

#8 Richie2shoes

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Posted 15 July 2020 - 12:53 PM

Thank you all for the help! I think I finally got It down. I will check it tonight with a star test.

One small question though. Is it normal to have to do large adjustments straight from the factory like this?

When I got my AWB OneSky, it only required a tweak of the primary mirror for collimation, when I got my AD12, I had to adjust the secondary, tighten down the entire primary mirror cell and collimate it.  So, it all depends.



#9 rhetfield

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Posted 15 July 2020 - 01:00 PM

When I got my AWB OneSky, it only required a tweak of the primary mirror for collimation, when I got my AD12, I had to adjust the secondary, tighten down the entire primary mirror cell and collimate it. So, it all depends.

surprising the secondary didn't need it on the OneSky. It often gets out of wack on the boat ride from China.
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#10 rhetfield

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Posted 15 July 2020 - 01:05 PM

Thank you all for the help! I think I finally got It down. I will check it tonight with a star test.

One small question though. Is it normal to have to do large adjustments straight from the factory like this?

factory will rough it in, but not spend a lot of time with it. Then it will get sent half way around the planet on a slow boat. Best one can hope for is it to be good for low/mid magnification. For high magnification, tweaking is expected. Some of these guys claim to need it every night.
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#11 Richie2shoes

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Posted 15 July 2020 - 02:00 PM

surprising the secondary didn't need it on the OneSky. It often gets out of wack on the boat ride from China.

I was a little surprised by it myself. 



#12 JJack

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Posted 16 July 2020 - 01:13 PM

I am a big fan of these two articles:

 

https://garyseronik....to-collimation/

 

https://garyseronik....pe-collimation/

 

The first article covers how to do the initial primary and secondary collimation using tools (primarily a collimation cap).  The second article covers how to use a star to do the collimation fine tuning that is needed to optimize performance.  Both are necessary.  The tools will get you close, but they are not perfect.  Often, the center donut is not perfectly centered or the mirror's physical center is not the same as optical center.  The end goal is to make the stars look good - which is why the star collimation is a must.

To a beginner, the start of that first article (re: the primary mirror) is PERFECT.  

 

To a new person, Everything that follows is just as hard to understand as it is with any of the other methods.


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