22 replies to this topic

[ClsscLib]

I’m newly returned to visual astronomy after over four decades away.  We used Mastodon bones for mounts back  then.

I recently received a new AD-10, and I worked on collimating it tonight using the Apertura laser collimator.  I have never collimated a Newtonian with a laser tool, though I have watched the High Point AD-8 collimation vid and another by a couple of British guys (recommended by High Point).

 

To my shock, the scope appeared to hit the collimation marks almost immediately, with no drama. I had to adjust the secondary knobs just a little to get the laser in the center of the primary.  But when I checked the primary collimation, the red dot seemed to be dead center on the 45 degree screen on the first try.

 

 Is this even possible?  I had expected to spend hours collimating, swearing, calling in air support, etc.

My natural inclination is to suppose that I have done something wrong.

 

Thoughts?

[Keith Rivich]

Of course its possible. I would be happy!

[Jay_Reynolds_Freeman]

A friend of mine used to say, "Things can't go wrong all the time -- that would be information!"

[star acres]

Mine, too

[sevenofnine]

Collimation frightened me so much that I didn't buy any tools for at least a year. I just peeked through the tiny hole in the collimation cap and said "Well,...it looks like a bullseye to me...good enough for government" 

Edited by sevenofnine, 26 March 2025 - 08:03 PM.

[Tony Flanders]

I've seen plenty of scopes that arrived properly collimated out of the box.

[therealdmt]

My Dob, a GSO f/5 10" (same as your Apertura), was also good to go out of the box, a happy surprise.

 

I’m so glad I followed the advice of fellow member radiofm74 who advised me to just assemble the scope, take it outside, give the sky a look with it first and see how it goes, and if there’s no issue, just use the scope awhile as it came out of the box before getting into messing with the collimation. Start out with good feelings about the new telescope and all it can show, and start to get the feel of how it works and how to physically handle the thing, before unnecessarily getting right into a potentially frustrating chapter with it if this is one’s first Newtonian (or in my case, my first fast Newtonian after having had an f/11 Newtonian decades ago that I could adjust the toolless collimation of by eyeball). 
 

Turned out the factory collimation was spot-on, and it held that way for at least a year (though I didn’t get to use the scope all that much the first year)

[Mike Q]

Sure its possible  

[Sebastian_Sajaroff]

Mine came well collimated as well.
It stayed so for several months, but I must mention that it never travelled more than 50 ft (from dining room to the backyard). Bumpy roads are collimation killers !

[A Star Geezer]

My ad10 was pretty close to collimated. I got tired of looking at the cloudy skies so I read a lot on collimating the scope. First thing I learned was my Laser was way off made a simple jig with 4 nails and a piece of 2x4 to align it. Second after "studying the process of collimation I still wasn't sure of what I was doing Bought a collimating cap posted pics on CN and with the help of Vic Menard and others I managed to correctly do it. Might be a case of  "blind luck or even a blind squirrel will find an acorn" Third don't get bogged down worrying about collimation just enjoy the scope and learn about using it for now. I was worried about mine in the beginning, now I'm worried abbot putzing around with it and messing it up. Always something to worry about. good luck and enjoy.

[ClsscLib]

Thanks for all the supportive replies to my first post!

 

I spent a lot of time yesterday prepping equipment and no time preparing to observe.  Over the last 40-plus years, clearly I have forgotten whatever I once knew about star-hopping.

 

Unsurprisingly, when I finally got going, I didn’t find anything besides Jupiter, Mars, and some bright stars. (I was using the scope on my back deck — sky was at best Bortle 6.5, and from that location I am limited to the Eastern half of the sky.)

 

The good news is that the star images in the scope were quite clear, and the scope shows a lot of dim stars crisply. That in itself was encouraging, and perhaps evidence that the collimation indeed is acceptable.

 

I’ve now figured out the true field of view of my RACI finder, the various scope/eyepiece combos, and the Telrad that I have yet to attach.  I’m hoping that I have some charts around here that are marked in degrees and displayed in correct images. 
 

But I suppose that finding things in the sky really should be the subject of my next post!

 

Thanks again.

[csrlice12]

One thing I miss about brick and morter astro shops.....mine put my dob (10" Intelliscope) together collimated it and made sure the intelliscope parts worked at no charge.  Drop ship just ain't gonna beat that.

[Vic Menard]

...I recently received a new AD-10, and I worked on collimating it tonight using the Apertura laser collimator.

...To my shock, the scope appeared to hit the collimation marks almost immediately, with no drama.

...Thoughts?

Using a simple thin beam laser collimator should give you a reasonably accurate focuser axial alignment (outgoing beam aligned to the primary mirror center marker) and a "usable" primary mirror axial alignment (return beam aligned to the laser emitter). A follow-up star alignment will likely find the "sweet spot" near the center of the field of view. No drama.

 

That said, a thin beam laser can't "see" the secondary mirror placement, which is responsible for most of the Newtonian collimation "drama". If your secondary mirror holder locks in the rotation adjustment (see the picture below), that could improve the possibility of the scope arriving pretty much "collimated" (or not--see post #15).

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Edited by Vic Menard, 27 March 2025 - 03:10 PM.

[Vic Menard]

Here's the view from the back of the "no rotation" secondary holder "on axis":

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Edited by Vic Menard, 27 March 2025 - 03:08 PM.

[Vic Menard]

If the secondary holder is round (see image below), rotation adjustment (and drama*) is enabled. 

 

*If the holder is 3-lobed and the rotation adjustment is not correct**, secondary mirror drama is elevated to angst and potential loathing.

 

**Yes, there is a fix.

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Edited by Vic Menard, 27 March 2025 - 03:16 PM.

[sunrag]

☝️Funny post!

[sunrag]

I wonder if it is possible to make a secondary holder that has a tapered top, so you can rotate the top (not the secondary, just the top) so that you can tilt the secondary easily without the need for the 3 or 4 tilt screws.

[Spile]

One thing I would recommend when aligning your primary mirror with the return beam of a laser is to confirm alignment with a cap. Cheap and simple to use. 

[triplemon]

I wonder if it is possible to make a secondary holder that has a tapered top, so you can rotate the top (not the secondary, just the top) so that you can tilt the secondary easily without the need for the 3 or 4 tilt screws.

Essentially all the standard secondary holder allow to rotate the secondary. Its a good thing and no problem for collimation.

The problem is just if the secondary is adjusted by folks without a good strategy to handle the dual options of rotating vs tilting the secondary. It can result in accumulating rotation that is counteracted by tilting the secondary more and more. It will result in some minor asymmetry in the secondary vignetting, which is still pretty benign, as it does not affect any other on or off-axis aberations.

 

So anytime you after "normal' collimation end up with a notably tilted secondary, just reset the secondary tilt so the gap in between the spider and the secondary holder is essentially even, Then first adjust rotate the secondary to get the laser spot on the primary as close as it gets first and only after that adjust tilt with the usual secondary tilt controls. That gets it all set up "as good as it needs to be".

 

All this is meant for users of a properly constructed scope. I..e a secondary holder that has a usefull tilt and a focuser that is reasonably aligned with the center of the secondary. Any alignment issues with these are adressed at contruction time - its not things that get out of whack due to normal use. So anytime your collimation angst drives you into modifying the secondary holder, its a lot more likely that you are going to permanently and possibly fatally damage an otherwise not broken at all scope.

 

Its similar with the degrees of freedom to adjust the secondary. Even if the rotation axis for the secondary were different, you would be able to destroy alignment as easily as with the normal configuration. So it really would not help.

The only somewhat helpfull option seems to build a holder that prevents users from rotating the mirror after construction is finsihed. But this adds problem to the initial construction, as these missing degrees of freedom would then require more expensive or heavy adjustment elsewhere to get it initially set up.

Edited by triplemon, 27 March 2025 - 06:04 PM.

[Vic Menard]

...The only somewhat helpfull option seems to build a holder that prevents users from rotating the mirror after construction is finsihed.

I believe that was the intent with the 3-lobed secondary mirror support (post #14). The 3 tilt adjustment screws are pretty much confined to a fixed rotation.

 

...But this adds problem to the initial construction, as these missing degrees of freedom would then require more expensive or heavy adjustment elsewhere to get it initially set up.

And that problem has already happened, with the simplest solution being to re-enable rotation.

 

...after "normal' collimation (you) end up with a notably tilted secondary, just reset the secondary tilt so the gap in between the spider and the secondary holder is essentially even...

That's a good idea, but it presumes the other geometries (focuser, spider, truss framework, etc.) are not contributing to the observed error. This was pretty common with truss work Dobs (Starmasters in particular) with thin focuser boards that would warp under the truss stresses, ultimately tilting the focuser. I fixed quite a few of those over the years...

 

...Any alignment issues with these are adressed at contruction time - its not things that get out of whack due to normal use. 

I agree, until it's something that wasn't addressed at construction time (like the 3-lobe secondary mirror mount) or it happened due to normal use (like the StarMaster UTA). Another one that has apparently slipped by the construction gurus is a secondary mirror that's glued to its mount with the major axis misaligned to the mounting's major axis. I've only seen a few of those (but I can only assume there are more out there that haven't been fixed, quietly (or maybe not-so quietly) contributing to secondary mirror "drama").

 

...So anytime your collimation angst drives you into modifying the secondary holder, its a lot more likely that you are going to permanently and possibly fatally damage an otherwise not broken at all scope.

The modifications I suggest are usually simple: stainless steel fender washers to enable rotation, or a focuser mounting plate with push-pull focuser leveling screws, nothing that would "fatally" damage an otherwise skewed secondary mirror. (Fixing an improperly glued secondary mirror is a different problem, and the solution is not for the faint of heart. If the problem is discovered in the manufacturer's warranty period, a new replacement part is the "easy" solution.)

 

...Its similar with the degrees of freedom to adjust the secondary. Even if the rotation axis for the secondary were different, you would be able to destroy alignment as easily as with the normal configuration. So it really would not help.

I'm not sure I understand what you're saying here. If the secondary does not have rotation enabled (the 3-lobe secondary mirror mounting), and the secondary mirror placement (and other geometries) is correct, any subsequent secondary mirror error is then confined to tilt and/or offset, which should be much easier to resolve, especially for beginners. I understand what the manufacturer is trying to do, and, thankfully, they haven't created an unresolvable problem.

 

...But this adds problem to the initial construction, as these missing degrees of freedom would then require more expensive or heavy adjustment elsewhere to get it initially set up.

Considering the number of scopes I've seen with the spider vanes mounted incorrectly (preventing optimal secondary mirror offset) and others with the spider hub rotated incorrectly (no tilt adjustment screw aligned with the focuser axis) complicating simple tilt adjustments, it's not always initial construction... Assembly complications require an additional level of collimation sleuthing.

 

You brought up a lot of interesting points!  

Edited by Vic Menard, 27 March 2025 - 07:24 PM.

[Whiteduckwagglinginspace]

My 8 inch Celestron dobsonian came collimated, but with a big stain on the primary mirror.

After trading the dobsonian for another one, the other one was also collimated. 

[dnrmilspec]

Saw a Celestron 8" SCT the other day that came out of the box dead on the money.  Corrector centered and perfectly collimated.  I could hear organ music. 

 

Enjoy your new scope!!!!

[TheChosen]

My 12" GSO's secondary was about a whole centimeter! lower vertically than it should be. You would never know it only collimating with a laser. They simply didn't spend any time in the factory whatsoever on collimation.

 

Make sure to check with a sight tube or cheshire combo tool about the secondary proper placement. Only then you will know.