Newbie here some questions about collimating flextubes

[Optic Nerve]

Hey everyone. Recently bought myself a Sky Watcher Heritage 130p flextube and have a few questions, as I understand that as a reflector telescope it will sometimes need to be collimated.

 

• How often is it likely to need collimated? I have heard everything from "I collimate it every time" to "Not collimated in months and it's been fine". I don't move it a lot, just take it out into the garden when its a clear night and then bring it back indoors when finished.

 

• When it first arrived I tried (perhaps foolishly) to try and "collimate by eyeball", training it on the moon and then turning the collimation knobs of the primary mirror in a trial and error fashion, checking the view to see if it got any better or worse. I stopped eventually as I wasn't seeing much change either way. I know that was probably a silly idea, at least until I'm more comfortable and know what I'm doing, but hopefully as there wasn't a noticeable change in quality of the view it's not a massive problem.

 

• At this stage, I'm only interested in observing fairly local objects, mainly the moon and Jupiter and Saturn. Does this make collimation more or less important than if I was observing nebulae/galaxies/further away objects? Or is it the same? I know the scope works by having the mirrors concentrate the light into a smaller area, so I wondered if the fact the moon is a lot closer than some random nebulae, there is more light available for the scope to pick up even if the alignment is not perfect?

 

• Will I need to align the secondary mirror often on this particular scope? The primary seems easy to adjust and I've read that's where 90% of collimation issues are,  but the secondary seems a bit more complex.

 

• Is poor collimation something that gets worse over time or does it just stay at that same "level" of poor until properly aligned?

 

• I've ordered a Cheshire collimation tube. Here's a picture of what I see when I look into the viewer at the moment https://imgur.com/a/MXkEvAV Does collimating the primary mirror basically consist of putting the cheshire in like I would normally put an eye piece in, then I'll see crosshairs on top of that view in the picture, and then I just need to move the collimation knobs on the bottom of the scope until the grey doughnut is in the middle of the crosshairs?

 

I'm very much a beginner at this, only had my scope for a week but I am really enjoying it so far. I can spend ages just looking around the various lunar mares. I live in an area with quite a bit of light pollution and don't drive, so very limited opportunity for truly "dark" sky viewing. But even so, I'm still quite impressed with the views I'm getting. If this is going to be a long term hobby I will need to get familiar with collimation at some point, even though it seems a bit daunting to me right now!

 

 

 

Edited February 6, 2023 by Optic Nerve

[Mr Spock]

If that's a view down your scope then the collimation is way off! 

When you look in the secondary, you should see all of the primary and it should be concentric. That's the first thing to correct.

Then when you adjust the primary, the little doughnut should be right in the centre. Your Cheshire will help you do this.

Does it make a difference? Yes, when a scope is properly collimated the image will be much sharper.

[Optic Nerve]

1 hour ago, Mr Spock said:

If that's a view down your scope then the collimation is way off! 

When you look in the secondary, you should see all of the primary and it should be concentric. That's the first thing to correct.

Then when you adjust the primary, the little doughnut should be right in the centre. Your Cheshire will help you do this.

Does it make a difference? Yes, when a scope is properly collimated the image will be much sharper.

Here's a couple with the viewing cap taken off.

https://imgur.com/a/H0joaLO

 

I can see the primary mirror and the three mirror clips but should all of it be further "up" on the secondary mirror? There's a lot of empty space up there

[Carbon Brush]

Hello and welcome to SGL.
Collimation is still way off.
The key word from @Mr Spock is 'concentric'
All of the circles in your views must be concentric.
Once you get the cheshire, it will be easy.

Did you buy from an astro retailer?
Any astro retailer will be happy to show you collimation if you take the scope back into the shop.
We can offer advice, or pointers to videos. But 5 minutes hands on is (in my opinion anyway) much better.

[happy-kat]

I've the same telescope and only periodically check collimation and I've only used a collimation cap. I did check secondary alignment and checked it's placement with a ruler to ensure it was evenly placed. Astrobaby collimation guide is the one I used to help understand doing collimation. On the occasions I would want to use the most magnification then I'm more likely to check collimation. The moon is quite handy for this when outside with just a collimation cap  it's a great telescope.

[Optic Nerve]

10 minutes ago, Carbon Brush said:

Hello and welcome to SGL.
Collimation is still way off.
The key word from @Mr Spock is 'concentric'
All of the circles in your views must be concentric.
Once you get the cheshire, it will be easy.

Did you buy from an astro retailer?
Any astro retailer will be happy to show you collimation if you take the scope back into the shop.
We can offer advice, or pointers to videos. But 5 minutes hands on is (in my opinion anyway) much better.

Bought it online.

That's a shame it's off, I have to say I'm not looking forward to tweaking the secondary mirror. Primary seems straightforward enough when I get my cheshire.

I've actually been quite impressed with the views I've got so far, of the moon. Once I've got the mirrors properly aligned will I see things even sharper?

[Clarkey]

17 minutes ago, Optic Nerve said:

will I see things even sharper?

Simple answer - yes. For visual use once it is collimated it should only need minor adjustments, usually the primary. For photography collimation tends to be more critical.

[happy-kat]

The view is very dependant on the night's viewing conditions and this can vary as you're observing, the Moon can really shows this.

[Spile]

I prefer to make a judgment from an image taken through a cap. Can you do that?

[Mr Spock]

41 minutes ago, Optic Nerve said:

Once I've got the mirrors properly aligned will I see things even sharper?

Indeed. It's not comparing like with like but with my 12" I've just been looking at Mars at x380 and seeing a lot of detail. A poorly collimated scope would be blurred with little or no detail and certainly wouldn't be able to hold high magnification in good seeing conditions. No scope on Earth will see fine detail in poor seeing conditions though!

[Optic Nerve]

12 minutes ago, Spile said:

I prefer to make a judgment from an image taken through a cap. Can you do that?

I've ordered one of these https://www.firstlightoptics.com/other-collimation-tools/astro-essentials-cheshire-collimating-eyepiece.html will post an image through that.

1 minute ago, Mr Spock said:

Indeed. It's not comparing like with like but with my 12" I've just been looking at Mars at x380 and seeing a lot of detail. A poorly collimated scope would be blurred with little or no detail and certainly wouldn't be able to hold high magnification in good seeing conditions. No scope on Earth will see fine detail in poor seeing conditions though!

Are there any "before and after" photos showing how objects like the moon look with poor collimation versus properly collimated?

[Mr Spock]

14 minutes ago, Optic Nerve said:

Are there any "before and after" photos showing how objects like the moon look with poor collimation versus properly collimated?

There's a few here http://www.astrophoto.fr/collim.html

[bosun21]

Your secondary mirror looks way off but i will reserve judgment until you get your Cheshire as the angle you hold your phone when taking the picture can be deceiving. The outermost dark ring is your focuser draw tube and you want your secondary mirror bang in the centre of it with the mirror perfectly round. Once you receive your Cheshire and snap a few pictures then we will be able to help further. Once you achieve good collimation then 9 times out of ten it’s only your primary mirror that may need a tweak.

[Spile]

It's definitely worth checking visually even without a cap or Cheshire, though its not as easy or accurate of course. Pull your eye back from the tube and confirm it looks like this...

[PeterStudz]

11 hours ago, Mr Spock said:

Indeed. It's not comparing like with like but with my 12" I've just been looking at Mars at x380 and seeing a lot of detail. A poorly collimated scope would be blurred with little or no detail and certainly wouldn't be able to hold high magnification in good seeing conditions. No scope on Earth will see fine detail in poor seeing conditions though!

It’s basically this. If the telescope is poorly collimated you’ll really notice it when you are at the limits - eg at high magnification and/or when you need good contrast.

So is the bit about seeing. It always amazes me how much more you can see on a night of good seeing (transparency too) - no night is the same - which always makes me want to take a look. 

As for holding collimation. Once the secondary is done you rarely need to touch it. The primary might need a tweak before a session but once it’s settled down I generally don’t need to touch anything. One example - I took a small reflector on an aircraft. After a car/taxi journey lasting a total of 3.5 hours, rattling through an airport, 4 hour flight, 45 min ferry journey… I was pleasantly surprised to find that collimation was still spot on. But it doesn’t mean it’ll always be that way.

Edited February 7, 2023 by PeterStudz

[Optic Nerve]

17 hours ago, Spile said:

I prefer to make a judgment from an image taken through a cap. Can you do that?

Cheshire arrived today, taken a few pics

https://imgur.com/a/YvShjOV

 

This may be a stupid question but is collimation an incremental process where a small improvement to the alignment results in a corresponding small improvement in the view, all the way up to a perfect alignment resulting in the best view you can get from that scope? Is there some margin for error for example if I get it from being “way off” to “a little bit off” will I still benefit from a much better view?

[Optic Nerve]

Tinkered a bit with the primary mirror screws at the bottom of the scope not sure if I made it better or worse

 

https://imgur.com/a/XIpxJpL

[happy-kat]

It's a bit better.

In your fiddling have you only touched the primary mirror?

[Optic Nerve]

8 minutes ago, happy-kat said:

It's a bit better.

In your fiddling have you only touched the primary mirror?

Yes. There's 3 knobs at the base of the scope to move it, I can reach them while still looking through the Cheshire so I've been doing that in trial and error trying to centre it.

 

[Optic Nerve]

https://imgur.com/a/QzvYuXi

 

Tried fixing the secondary mirror but just made it a lot worse

The mirror was loose at one point and I accidentally moved it so its probably off-kilter now. Maybe I should have gone with a refractor, this is frustrating

[wulfrun]

41 minutes ago, Optic Nerve said:

https://imgur.com/a/QzvYuXi

 

Tried fixing the secondary mirror but just made it a lot worse

The mirror was loose at one point and I accidentally moved it so its probably off-kilter now. Maybe I should have gone with a refractor, this is frustrating

First couple of times is when you get your brains tangled up. Read the guides until it sticks in your head and you can look and know what you're seeing. Once you "get it" it becomes a simple and quick job, so stick with it! Ask any Newt owner, they'll likely tell you much the same. First time I did one of mine, I was faffing for hours. Now takes a few minutes, worst case, when I've bumped it (which happens).

[Optic Nerve]

15 minutes ago, wulfrun said:

First couple of times is when you get your brains tangled up. Read the guides until it sticks in your head and you can look and know what you're seeing. Once you "get it" it becomes a simple and quick job, so stick with it! Ask any Newt owner, they'll likely tell you much the same. First time I did one of mine, I was faffing for hours. Now takes a few minutes, worst case, when I've bumped it (which happens).

Does this look any better https://imgur.com/a/uDitdAO I can't see the three mirror clips for the primary mirror though.

 

Sorry about the image spam by the way. I know this should be simple enough and I dare say it will be eventually, after enough attempts it will just "click" and become second nature but it's a bit confusing right now.

 

Edited February 7, 2023 by Optic Nerve

[happy-kat]

That looks better. I'd go outside and enjoy your telescope and come back to this another cloudy day to improve it. If you are adjusting your secondary then it's safer to protect your primary mirror from anything falling on it.

[Optic Nerve]

2 minutes ago, happy-kat said:

That looks better. I'd go outside and enjoy your telescope and come back to this another cloudy day to improve it. If you are adjusting your secondary then it's safer to protect your primary mirror from anything falling on it.

I wasn't sure, it did seem to look more aligned than the first couple of pics and certainly that last one where the mirrors are totally out of view.  The couple of things that concern me is that I can't see the three clips for the primary mirror although I do seem able to see the mirror itself completely in the frame now. And also, that picture was taken with the cheshire put into the viewer and screwed into place. But it's not firmly in place, the cheshire can move a bit if pressure is applied which makes it look a bit less aligned than that.

[bosun21]

I will try to help you out. 
1: Put your telescope in the horizontal position and pointing to a window or bright wall.

2:- place a piece of card or colored paper blocking your primary mirror from your secondary mirror. Place a piece of white paper directly opposite the focuser.  
3:- Now you want to move your secondary mirror until it’s bang in the centre of your focuser draw tube and perfectly round. To move the mirror forwards and backwards, ie: nearer the primary or nearer the open end of the tube by turning the central screw. Clockwise will move it towards the open end of the tube and vice versa. With the card and paper you will only see the secondary mirror and you can position it pretty easily without dealing with the primary reflection.

4:- When your happy that everything is correctly positioned take another photo without removing the card/paper. If it’s okay I’ll take you through the primary mirror setup. PS:- When it’s positioned correctly the wire cross of your Cheshire will be bang centre of the secondary. Good luck 🍀