Glyn80

Hi @Ricochet yes the doughnut is on the red dot. That picture through the cheshire was after I had collimated the telescope by only using the collimating cap. When trying to collimate using only the Cheshire i just can't get it all central. I was definitely using the Cheshire's crosshairs. 

Many thanks @Jasonb and @John. I'm glad you both said it looked ok. Yes I was surprised at how good the star test was (I was expecting a lot worse!) I'm going to stop messing around with the collimation now in the endless search for perfection and i'm going to start enjoying the stars! 🙂 

Hello,

I'm at my wit's end. I've been trying to get my secondary mirror adjusted on my Skywatcher 200p Dob. But i can't seem to get it central in the Cheshire once it's been aligned with the doughnut on the Primary mirror. I can get the secondary mirror nice and central in the Cheshire before I try and line it up with the primary doughnut. But once i start adjusting the three allen screws on the secondary, to get the doughnut in the centre, the secondary mirror always seems to move upwards and is no longer central in the Cheshire. I can't keep the secondary in the centre of the Cheshire AND get the doughnut in the centre as well. As far as I am aware everything should be central at the end of the collimation.

In the end I just used the collimation cap last night to do the secondary alignment and the result is in the photos below.

I took the telescope out last night and tried the Star Test and it all looked really good, all the circles were concentric. The moon also all looked really clear and in focus and I even found Orion's nebula.

I have attached photos of the view through a Collimation cap and the Cheshire. 

My question is, do I keep on trying to adjust it to get it spot on in the Cheshire? Or does it all look and sound good enough as it is? As this collimation is starting to take all the joy out of owning a telescope 😞

Many Thanks for any suggestions.

On 19/09/2020 at 17:15, Pixies said:

Clear skies tonight? Let us know how it goes

I managed to get out tonight to see how the collimation had gone, even though it was a bit breezy with some cloud. I was able to see Jupiter and it's belts and all seemed to be in focus. Even better was Saturn, I was able to see a black line separation in the rings and I even noticed a slightly darker band going around the middle of Saturn. Finally I moved onto Mizar and Alcor and I was clearly able to see Mizar B closely adjacent to Mizar. So all in all everything looked good (well from a novice's perspective it did), i'm assuming if my collimation was poor, I wouldn't be able to see the details on Jupiter and Saturn? 

That all makes sense, I couldn't understand why my laser collimator was out by so much after using the Cheshire. Now I've centered everything properly using the Cheshire, the laser lines up as well now. Thanks for your help, much appreciated! 

OK yes that makes sense. I've been focusing too much on being able to see the three primary clips rather than lining up the doughnut with the cheshire's crosshairs. 

Hello,

I've finally bought a Cheshire and have been using it today. This is how I have ended up with the collimation. I think it's looking ok. I can see the three primary clips (but only when i'm fully racked in) and the primary mirror seems aligned. I had to centre the secondary a bit as well.  Any opinons greatfully received, thanks.

Thanks for the link. That software looks good and it clearly shows the secondary being off centre. I will have a go at adjusting that next, once I get a Cheshire.

I've just had a go at fixing the rotation. In the end I just rotated the holder by hand as I had to adjust the lenght of all the adjuster screws as one of them seemed to be putting a lot more pressure on the holder. To my surprise it was easier than I thought and nothing fell off 🙂 I've attached two photo's. Before and After and I think it looks better now.

OK that's great, thanks for your help much appreciated!

From what i've read on AB'S site, am I understanding it correctly that the secondary mirror is rotated by just using the three tilt adjuster screws?

Thanks for the great advice. The Astro-baby guide is a really useful, especially the tip of putting paper behind the secondary mirror so I can see it's actual shape, which has helped make sense of things. I'm getting frustrated with the laser collimator though. All was aligned up well yesterday but after using the telescope last night and checking the laser collimation today, its off it's alignment. The collimator cap's view hasn't changed and the primary mirror is better aligned as i've just tweaked it. So something seems to be causing a problem with the laser. I try to get all the screws tightened up evenly so ensure the laser is central but something isn't quite right, maybe it's the focuser?. I think I will give the Cheshire a go as @Pixies  suggested to align the secondary mirror, then at least i will know that's ok.

Hello everyone. I'm from the UK and I've recently purchased my first telescope a 200P Dob. I'm a complete beginner but looking forward to learning as much as I can 🙂. Thanks Glyn. 

Hello everyone,

I've recently purchased a Skyliner 200P Dob as my first ever telescope and i've just had a few attempts at collimation for the first time (as daunting as it felt 🙂 ). I purchased a collimating cap and a Baader laser collimator. When i first collimated the telescope I wasn't convinced the laser was ever aligned perfectly straight/centered using the use two tightening screws in the focuser. So I also purchased a Celestron Twist and Lock adapter to try to ensure everything was straight/centered as it could be. I've had a few attempts to try and get it all perfect, I might even be going a bit OCD with it to be honest 🙂. I have taken a picture through my collimation cap with how it looks so far. I think the primary could maybe do with a very slight adjustment but i'm not sure if the secondary all looks as it should? It would be great if someone could just confirm how it all looks, so I then know for future reference that i'm actually do it right. Many Thanks!