Another collimation question...film canister method

[BeerMe]

My new (first) scope arrives on Wednesday and all my excitement is being tempered the more I read about collimation.  I have a feeling that if my scope is off, I'm going to be spending a lot of time trying to sort it.

 

I've read as much as I can in here, and also astro-baby's article on the subject and I managed to get a pdf of my telescope manual online which also has a bit on collimation using the film canister method.  I think I understand the instructions on how to do this method but I'm not entirely sure on the placement of the items in the focuser.

 

My understanding is that the cap of the canister with the hole should be placed in the focuser first, top down, then the body of the canister with the bottom cut out is placed on top of it?  Or am I getting this wrong?

 

I hoped there'd be a video online but I can't find anything.

 

P.s  the scope is a skywatcher-heritage 130p. 

[Floater]

First, you shouldn't worry too much about collimation. Even having said that, I know you WILL worry about it; I think everybody does. But the advice given to me and others still stands - once you've done it everything falls into place in your mind and collimation is just part of the fun of using a telescope.

However, I would recommend something a bit more custom-built than the film canister. A Cheshire, or even a collimation cap will be better. The canister method will work but, given your anxiety about collimation, you will reduce any uncertainties in your mind if you use custom-made tools.

Last, I would advise against attempting collimation immediately. Most scopes arrive reasonably well collimated, I believe, Also, your scope will be fairly forgiving - as is my 150 Dob. Use the scope and become familiar with it and how it works.

You will have come across the term airy disc, or disk, in your research. You can play about with your scope and, if you feel it could be better, only then go for collimation.

Most important is - have fun. That's what you're buying a telescope for! It'll be Wednesday before you know it ...

p.s. Sorry, should have pointed out that you only need the canister cap in the focuser if you choose to use that method. It's really just a way of ensuring your eye is centred while looking at the secondary mirror through the focus tube.

[Uplooker]

Not quite. Take an ordinary film canister. Cut the base base off, only the base. Remove the lid and pierce a small hole as close as possible in the centre. reattach the lid and pop the canister in the EP holder. The shoulder around the canister cap will sit nicely on the top rim of the focuser.

Ah, just seen Floater's reply, good information.

[laudropb]

Hi. Try not to worry about Collimation. Hopefully your new scope will not require it at first. I would also recommend getting a Cheshire collimator. When I started out I found it made all the difference. Which scope have you got ?

[billyharris72]

Hi there. I would definitely recommend the collimation cap from FLO. Does the same job as the film canister, but guarantees that the hole is nice and central and fits perfectly in the focuser.

I'd echo the view of others not to worry about collimation. The secondary mirror pretty much always comes well aligned. If you want to check the primary all you need to do is pop the collimation cap in and look through the hole. Is the little "polo mint" sticker centred in the reflection of the cap (with your eye hole in the centre)? If so it's collimated. Even if it's a little bit out (e.g. the eyehole is not dead in the middle off the little sticker hole and is overlapping the white sticker material a bit) it should be fine. No need to tinker unless it's further off than this.

As well as being a great scope optically, the Heritage 130P is really easy to collimate, as the tube is so short you can turn the collimation screws while looking into the cap. Even the first time I ever did it I'm not sure it took more than about 10 minutes. With a bit of practice it takes literally about a minute to get it perfect.

Enjoy.

Billy.

[ronl]

Don't get worried about collimation, your new scope will be ok to use straight from the box, the only mirror that mat be out,

probably not by much will be the primary, the big one at the bottom, if you buy a Cheshire collimator, as laudrupb has said,

you will only need to use that, this one is good http://www.firstlightoptics.com/other-collimation-tools/cheshire-collimating-eyepiece.html

the cap is used to center the secondary and you probably won't need to do that, not straight away, turn the Cheshire toward the light, then

look down the small hole in the top and you will see if it needs adjusting, you may need to tweek it a little, probably not much, then you will

be good to go.

Good Luck and Clear Sky's

 

[Skipper Billy]

The simplest, most effective and cheapest upgrade to that particular scope is a few turns of PTFE (Plumbers) tape round the threads of the focuser - it transforms it from a wobbly sticky thing (scientific phrase!) into a much smoother and more accurate focuser. 

If you do decide to adjust the collimation then the above mod will help.

Cracking wee scope.

 

[BeerMe]

Thanks for the replies everyone!  It came today!!  Literally just arrived. 

 

Once I got it out and assembled I noticed the secondary mirror support,  which hangs from a single vein, was turned 90 degrees.  It turned back no problem with a slight click in to place but it seems to move easier than I expected.

 

 

 

I tried taking a pic on my phone to let you see how it looks down the focuser...I dunno if it will show good but from what I have read, the secondary mirror looks well aligned as I can see the 3 clips when I manage to look down the centre.

 

[BeerMe]

1 hour ago, Uplooker said:

Not quite. Take an ordinary film canister. Cut the base base off, only the base. Remove the lid and pierce a small hole as close as possible in the centre. reattach the lid and pop the canister in the EP holder. The shoulder around the canister cap will sit nicely on the top rim of the focuser.

Ah, just seen Floater's reply, good information.

 

Thanks mate, that makes much more sense lol!

[BeerMe]

1 hour ago, Skipper Billy said:

The simplest, most effective and cheapest upgrade to that particular scope is a few turns of PTFE (Plumbers) tape round the threads of the focuser - it transforms it from a wobbly sticky thing (scientific phrase!) into a much smoother and more accurate focuser. 

If you do decide to adjust the collimation then the above mod will help.

Cracking wee scope.

 

Thanks Skipper, I had read that suggestion before and after a few twist of it I was able to see why...it is kinda sticky and it'd be problematic when you're looking for small, precise movements.

 

I'll get my hands on some today, thanks again

[BeerMe]

Another question...

 

I took the scope in to the back room to see if I could align the finderscope with a block of flats about 3-400 yards away.  I used a cross section at the top of the flats and put the RDF on that.  When I looked in the EP, it was off significantly so I brought the cross section in to view through the EP, then checked the RDF again.  It was above and to the left of the target.

 

I adjusted it down to the horizontal no problem, however when I moved it all the way across to the right as much as I could, it wouldn't go as far as the target in the EP.  I checked the EP again to make sure the tube hadn't moved while I was adjusting the RDF, but it was still centered on the cross section.

 

As I said above, the secondary mirror holder seems to move slightly with minimal force applied.....I expected it to be more rigid and I don't know if this is part of the issue?

 

I have plenty of time to sort whatever the issue is anyway....no clear skies here for a while it seems...

[laudropb]

It might be that your target is not far enough away. Usually you have to use something at least half a mile away, the further the better.