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  #1  
Old 10-10-2018, 08:27 AM
morls (Stephen)
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Star testing and collimating 180 Mak

I think it's time to get 'under the hood' of my new scope, and star testing/collimation seems a good starting point. I'm reading up on some background provided by Nick and Alex (thanks!), and thought I might use this thread to ask any questions that come up (and there will be many, I'm sure).

My first step is to set up a basic imaging rig so I can post pictures of what is happening. I've pulled apart a webcam and will attach this adapter:
https://www.bintel.com.au/product/bi...ebcam-adapter/

Once I get things set up I'll post some images of star tests. This will also give me a good reference point before I start with collimation.

Here are some of the sites I've found so far:

http://www.bbastrodesigns.com/ratemirrors.html

This one is good, (I hope it's OK to link to another forum here - in this case the page is archived) https://www.cloudynights.com/topic/3...-testing-maks/

https://www.bbastrodesigns.com/JoyOf...arTesting.html

And as suggested by Nick: https://www.telescope-optics.net/ind...LE_OF_CONTENTS


Cheers
Stephen
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  #2  
Old 10-10-2018, 09:26 AM
nsavage (Nick)
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I’m interested to know what webcam you’re using.
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  #3  
Old 10-10-2018, 10:14 AM
morls (Stephen)
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Hi Nick,

I'm using a HD 720p webcam I got from Jaycar a couple of years ago, not sure of the model. It has a threaded socket over the sensor so I'm hoping the Bintel adapter will work.

This video has been my guide:
https://www.youtube.com/watch?v=1gF6iHrZ4Rw
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  #4  
Old 10-10-2018, 10:58 AM
Wavytone (Nick)
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Pretty sure at the prime focus of the scope the webcam will only show points - it won’t resolve the airy disk cleanly as the pixels are too big.

Eyepiece projection or 3X Barlow may be needed.
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  #5  
Old 13-10-2018, 08:28 PM
morls (Stephen)
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I've had a couple of nights with the webcam - it's a lot of fun on the moon. It's also been good for developing my focus technique. I haven't had any success with recording star testing, I think that I'd need a better setup as Nick suggested.

After playing around with the cam it's always a pleasure to go back to visual - the moon has been stunning with my 35mm Panoptic. I've done some more star testing, and I think the scope needs some minor collimation. I'm expecting a new diagonal soon - just using the stock one at the moment. Is it a good idea to wait until the new diagonal is fitted before collimating?
Cheers
Stephen
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  #6  
Old 14-10-2018, 10:18 AM
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doppler (Rick)
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Hi Stephen

Here's a link to a daylight collimation check method. As for using diagonals during collimation, I would think leaving it out would reduce chances of introducing errors.

http://www.robincasady.com/Astro/collimation/

Rick
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  #7  
Old 15-10-2018, 08:11 AM
morls (Stephen)
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Thanks Rick, that's a really useful link. The out of collimation image corresponds with what I'm seeing with the star test. It's not way out, but in need of some adjustment.
I'm a bit nervous about collimating this scope, mainly because I haven't done it before. I've collimated my old reflector many times, but never a closed tube.
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  #8  
Old 15-10-2018, 07:02 PM
TareqPhoto (Tareq)
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I really wish to see any image of planets done with this 180mm Mak and using 3x Barlow producing very high quality image, not just a good image or so so, i really wish.
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  #9  
Old 15-10-2018, 07:30 PM
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doppler (Rick)
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Quote:
Originally Posted by TareqPhoto View Post
I really wish to see any image of planets done with this 180mm Mak and using 3x Barlow producing very high quality image, not just a good image or so so, i really wish.

This is probably the best I have managed with a gso 2.5x barlow and my skywatcher 180mm mack cass and zwo120mc.
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  #10  
Old 15-10-2018, 08:22 PM
TareqPhoto (Tareq)
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Quote:
Originally Posted by doppler View Post
This is probably the best I have managed with a gso 2.5x barlow and my skywatcher 180mm mack cass and zwo120mc.

That is nice, but still not a high quality or mind blowing as from C14 or C11, and i asked with 3x Barlow, but you did a great job, thank you very much!
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  #11  
Old 15-10-2018, 10:55 PM
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doppler (Rick)
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A fairer comparison would be with a c8, remember the 180 mack is only 7" aperture and a slow f15
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  #12  
Old 16-10-2018, 01:12 AM
TareqPhoto (Tareq)
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Exactly, so that i was thinking what is a big jump from 7" [180mm] should be? C11 won't be really a big jump, C14 yes, but anything else? any another big jump from 180mm and not C14 only?
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  #13  
Old 16-10-2018, 08:14 AM
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doppler (Rick)
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Quote:
Originally Posted by TareqPhoto View Post
Exactly, so that i was thinking what is a big jump from 7" [180mm] should be? C11 won't be really a big jump, C14 yes, but anything else? any another big jump from 180mm and not C14 only?

The big jump from a 180mm Mak is the f ratio, f15 down to f10 is a leap astro imaging wise. The C11 has the same focal length but is much faster. Resolution also increases with aperture. Of course the biggest factor for high magnification imaging is the need for good seeing, here in the tropics it's usually pretty ordinary.
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  #14  
Old 17-10-2018, 02:03 AM
TareqPhoto (Tareq)
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Quote:
Originally Posted by doppler View Post
The big jump from a 180mm Mak is the f ratio, f15 down to f10 is a leap astro imaging wise. The C11 has the same focal length but is much faster. Resolution also increases with aperture. Of course the biggest factor for high magnification imaging is the need for good seeing, here in the tropics it's usually pretty ordinary.

f10 is nice, but in planetary sometimes people even go higher to f20 or f25 even f30, so i assume that focal ratio isn't a critical factor here, they all mention aperture or focal length over f ratio.
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  #15  
Old 17-10-2018, 07:01 AM
morls (Stephen)
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I'm still in 2 minds about what to do regards collimation. Is it something to avoid unless absolutely necessary due to complexity? I've read differing opinions on this.

The skywatcher manual doen't mention collimation. There are 3 sets of 2 screws on the back. Are there locking screws which need to be loosened before adjusting, or are all screws part of the adjustment system?

Thanks
Stephen
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  #16  
Old 17-10-2018, 07:32 AM
TareqPhoto (Tareq)
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Quote:
Originally Posted by morls View Post
I'm still in 2 minds about what to do regards collimation. Is it something to avoid unless absolutely necessary due to complexity? I've read differing opinions on this.

The skywatcher manual doen't mention collimation. There are 3 sets of 2 screws on the back. Are there locking screws which need to be loosened before adjusting, or are all screws part of the adjustment system?

Thanks
Stephen

I never touched the screws of 180mm and the collimation is good, i was going to damage it or modify or whatever just only because some are talking about collimation, i just ended up ignoring all that and using the scope as it is, turned out it is really nice and no issues, maybe i am lucky with this copy of mine.
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  #17  
Old 17-10-2018, 08:03 AM
morls (Stephen)
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That's interesting Tareq. Mine is pretty darn good too. I haven't touched anything since buying it brand new. My normal way of thinking is to check things to make sure shipping and handling hasn't unsettled anything. From what I gather these scopes hold collimation very well, so any adjustments would likely be fine tuning, and then the scope should be stable for a good while.
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  #18  
Old 18-10-2018, 08:27 AM
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mental4astro (Alexander)
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To collimate or not collimate? - THAT is the question

So, you have a new scope, Mak, SCT, Newt, dob, whatever. The image it throws up "is pretty good" you reckon so you don't make any adjustments. That's fine.

But remember this - astro is ALL about pushing the very limits of optics to get the very best image your gear can give you. Astro is pretty much the most punishing application of optics that there is! So while you may be happy with the current image your scope gives you, if it is out of collimation, you are only cheating yourself out of the very best your precious scope can give you. So, you have a darn nice scope, but without getting the optical alignment right, the scope effectively has a "black eye"...

At the factory, there are time pressures to push out scopes, or you may have got a scope collimated at 4:00pm on a Friday arvo with the technician paying more attention to the clock than the job at hand, or the technician may feel near enough is good enough, or the technician doesn't know how to get the collimation any better. So the stuff coming straight out of the factory may or may not be good, but rarely is it as good as the scope can be.

So now, after doing all your research, spending your hard earned cash, and feeling pretty good with your purchase, the way I see it you owe it to yourself to become really well acquainted with your scope so YOU can squeeze every single photon into where it should go.

"Scared" about stuffing something up? What are you scared of? If things do go pearshaped, THAT is actually a good thing! You learn from your mistakes, AND this site and others like it are here to help you get it right!, or did you forget that! Believe it or not, I still "stuff up" the collimation process, and sometimes stuffing it up is part of the "getting it right" process! Sometimes the element that you do adjust is not the one that actually needed tweaking, and it is only by stuffing up that you become aware of this.

Oh, and another thing, as your experience grows, so does your visual acuity, and you will pick up on things not being quite right. So while at first you may not notice that the collimation isn't quite right, YOU WILL, and it will bother you like a stone in your shoe! And then what? Are you going to leave that stone in your shoe?

Alex.

Last edited by mental4astro; 18-10-2018 at 08:39 AM.
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  #19  
Old 18-10-2018, 10:58 AM
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Outcast (Carlton)
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Sheesh your posts drive me nuts sometimes Alex....

But, in a good way....

Having already done some 'tweaking' of the mechanics of my recently acquired LX90 8" and, being pushed by others to become way more anally retentive about the precision of my setup & star alignment process now, I'm gonna have to give some serious thought to the whole collimation process....

I really wanted to avoid this but, now I feel compelled....

Thanks...

Quote:
Originally Posted by mental4astro View Post
To collimate or not collimate? - THAT is the question

So, you have a new scope, Mak, SCT, Newt, dob, whatever. The image it throws up "is pretty good" you reckon so you don't make any adjustments. That's fine.

But remember this - astro is ALL about pushing the very limits of optics to get the very best image your gear can give you. Astro is pretty much the most punishing application of optics that there is! So while you may be happy with the current image your scope gives you, if it is out of collimation, you are only cheating yourself out of the very best your precious scope can give you. So, you have a darn nice scope, but without getting the optical alignment right, the scope effectively has a "black eye"...

At the factory, there are time pressures to push out scopes, or you may have got a scope collimated at 4:00pm on a Friday arvo with the technician paying more attention to the clock than the job at hand, or the technician may feel near enough is good enough, or the technician doesn't know how to get the collimation any better. So the stuff coming straight out of the factory may or may not be good, but rarely is it as good as the scope can be.

So now, after doing all your research, spending your hard earned cash, and feeling pretty good with your purchase, the way I see it you owe it to yourself to become really well acquainted with your scope so YOU can squeeze every single photon into where it should go.

"Scared" about stuffing something up? What are you scared of? If things do go pearshaped, THAT is actually a good thing! You learn from your mistakes, AND this site and others like it are here to help you get it right!, or did you forget that! Believe it or not, I still "stuff up" the collimation process, and sometimes stuffing it up is part of the "getting it right" process! Sometimes the element that you do adjust is not the one that actually needed tweaking, and it is only by stuffing up that you become aware of this.

Oh, and another thing, as your experience grows, so does your visual acuity, and you will pick up on things not being quite right. So while at first you may not notice that the collimation isn't quite right, YOU WILL, and it will bother you like a stone in your shoe! And then what? Are you going to leave that stone in your shoe?

Alex.
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  #20  
Old 18-10-2018, 11:30 AM
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mental4astro (Alexander)
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Sheesh your posts drive me nuts sometimes Alex....


Mission accomplished!

It's not hard tweaking a scope. But it does require patience and time to understand. I guess it is a bit pedantic, but you didn't get THAT scope with the express intention of enjoying a half-cocked image, did you now...

If you have an SCT or a Skywatcher Mak, collimating is very easy, but it is time consuming, and in our rush-rush-rush lifestyles this isn't the most enjoyable experience. BUT, get the optics right, and oh-golly-gosh! you are in for a treat tonight! What makes the collimating experience worse is the pressure you put on yourself to get to use the scope viewing through it! It's an unfair pressure and it is all self inflicted. But it's something you need to control. Or do you still want that half-cocked image...?

I'll give you a recent example of mine. I borrowed an 8" SCT from a mate last month. It's about 8 years old, and a stock standard SCT. When I set it up the image was "ok". Saturn was nice with this scope, the Cassini Division was clear, and the cloud bands were noticeable with shading differences, but I did notice that the optics needed tweaking. So I spent some time tweaking the secondary mirror's collimation screws, and spent half an hour slowly tweaking this screw this way, same screw the other way a bit less, tweaking another just a touch, etc. When I got it as good as I could, OMG! WHAT A FLAMING DIFFERENCE!!!

The cloud bands were now able to be seen individually, not just as a difference in shading. The Cassini Division was so sharp. There was such a distinct difference between the A, B & C rings in hue, and the C ring hinted at shading differences. Oh, and the kicker was the Encke Division was now visible!

Was it worth that half hour to tweak the "ok" image? You bet!!!

With a Newt or a high end Mak like an Intes Mak, you have to adjust both a secondary and primary set of mirrors, and it doesn't take that long either. You just cannot rush it. I adjust my Newts every time I set them up because these scopes have a lot of subtly held moving parts that they do shift a little with the vibrations of transport - it's one of the hazards of owning a Newt.

Yes, at first I found it a pain in the bum to collimate, but now it is part of my set-up ritual and not something I would ignore doing as I know it is to MY benefit.

The good thing about Maks and SCTs is they hold their collimation a whole lot better than Newts, so tweaking them is a rare event. But SO MUCH WORTH THE EFFORT!

Alex.

Last edited by mental4astro; 18-10-2018 at 11:41 AM.
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