SCT

[recceranger]

Guys,

any useful advice and or links for collimating a CPC 1100?  I would prefer not to go out and buy a tool!?

[Chris]

Hi, it's just the 3 screws on the secondary that need adjusting:

 

 

Always scary having a screwdriver so close to the corrector plate, Bob's knobs can help avoid this

[knobby]

If you don't have an artificial star a ball bearing at a good distance can work ... Or even a real star ! Through a gap in the clouds would be nice .

[Aussie Dave]

+1 for that video link that Chris posted and advise. It's a bit daunting if you haven't done it before but for SCT's it's very simple. I wouldn't worry about buying collimators, I found them useless and got better collimation on a defocused star and the help from that video.

[Highburymark]

There are a couple of recent threads on this forum discussing home made artificial stars - see Ollie's suggestion involving a ball bearing and a cardboard box. It's very effective.

[beka]

Once you get familiar with the process, it does not take very long to collimate the telescope. I have collimated my CPC 1100 a couple of times on a star and it took maybe 10 minutes. Since you have to go outside to observe anyway, maybe it is just better to practice doing it on a star 

[PeterCPC]

I do find it much easier with Bob's Knobs fitted - keeps that screwdriver away from the corrector

Peter

[faulksy]

try and use polaris as well, this will give you as long as you need ,and after each adjustment re center

[VSOP]

Forget the tool. I bought one, tried it & returned it the very next day. It's a waste of time, money & effort. Take your scope outside and target a medium bright star. Polaris works great. center the star and then take it out of focus until you see a circle inside a circle with a number of other circles in between. Adjust the knobs until these circles are symmetrical. Done...

[Dave In Vermont]

On 3/16/2016 at 10:53, PeterCPC said:

I do find it much easier with Bob's Knobs fitted - keeps that screwdriver away from the corrector

Peter

Just two little caveats:

1. When installing Bob's Knobs, only replace one screw at a time. If you were to remove all three at once - your secondary will fall out inside the tube!

2. Keep the SCT level, or even tilted slightly nose-down. This so when you drop any tools, they won't hit the corrector-plate!

With this in mind - Bob's Knobs are a worthy upgrade to one's SCT.

Now for a clear sky.....

Dave

[Pig]

I am with Beka, my first time collimating an SCT was on an actual star.... I wished I hadn't touched it at first but it turned out to be quite straight forward once you got to know how adjusting the screws affected the movement of the doughnut.... Go for it as long as you don't do anything drastic you will be ok.

[Mr Spock]

Collimate using a star. Fitting Bob's Knobs makes it easy.

As you have to collimate anyway after fitting Bob's Knobs there's no need to fiddle with the installation. Just unscrew the plastic outer ring on the secondary housing and the secondary will come out - easy