Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_30_second_exp_2_winners.thumb.jpg.b5430b40547c40d344fd4493776ab99f.jpg

Sign in to follow this  
blinky

Quick easy question!

Recommended Posts

Just about to nip outdoors and collimate my newt. Can somebody just confirm it's the main mirror that I adjust to get the centre spot bang on and the secondry mirror adjusts the 'outside' you know the 3 'clamps' that hold the main mirror in place.

Just want it confirmed before I mess everthing up, last time I did this I nearly lost the secondry down the tube, that was a scarry moment :wink::D

Share this post


Link to post
Share on other sites

I looked at the video and it all makes sense :D Just had a look and my scope looked to be near enough bang on. I adjusted the primary but only by a very small amount, the black spot was within the small centre circel but not dead centre.

The thing is on Friday night somebody (and it could have been yourself!) had Alberio nice andsharp and with my scope we could not get it as sharp! It was suggested that my scope may need a slight adjustment, I dont think what I just did would make any diffrence as it was very small!

Anyways I have also just cenetered my Polar scope as well so with any lucj next time out I may get some images done :wink:

Share this post


Link to post
Share on other sites

What I found easy was using the old cap of an old film cannister, putting a small hole in its center then putting it in the focuser. Look through it and basically center what you see and ensure you can also see the clips around the edge. To fine tune i then use a laser collimator to bring the main mirror into alignment with the secondary mirror so that the beam goes back on itself back through the collimator. What was taking me ages is now done in a matter of minutes.

Share this post


Link to post
Share on other sites

I have one of the collimation caps, but the thing is the 'scope always looks to me to be pretty near bang on. I dont want to spend 50quid on a laser collimator thats says 'all is well'! If I did need to adjust it everytime I took the 'scope out then I would spend the money but at the moment it looks like this scope keeps pretty good collimation anyway.

Just strange I could not get as sharp a focus as others especially as we were using the same EP in both scopes!

Share this post


Link to post
Share on other sites

damned fine tutorial that -

removed my newbie reservations about getting a big dob at some stage.

thanks for the link.

a few q's:

1. I'm assuming that once you've collimated a scope a few times you learn to do it quite quickly -

or is it always a bit fiddly?

2. Are any brands of dobs easier than others to collimate?

3. Are the big truss dobs harder to collimate or about the same as the tube type?

Share this post


Link to post
Share on other sites

Like i say above I think mine seems to keep pretty good collimation. I have now done it a few times and each time it just needs a small tweak. One tip though, only adjust by very small amounts at a time. I did my usual and made a massive adjustment of one screw and it took about 2 hours to get it all back again. Now though it only takes a couple of mins to do.

Share this post


Link to post
Share on other sites

damned fine tutorial that -

removed my newbie reservations about getting a big dob at some stage.

thanks for the link.

a few q's:

1. I'm assuming that once you've collimated a scope a few times you learn to do it quite quickly -

or is it always a bit fiddly?

2. Are any brands of dobs easier than others to collimate?

3. Are the big truss dobs harder to collimate or about the same as the tube type?

1. It gets easier once you know what you're doing. Like everything else it needs a few times to get the hang.

2. dobs with bob's knobs! I think all newts have the same collimating system and it's the same from newt to newt. However, you can make it easier by fitting bob's knobs. Larger newts are less convenient to collimate because you've got to tweak, check, tweak, check and go from one end of the thing to the other. Also faster newts f/6 and below need more frequent, accurate collimating.

3. Truss dobs need collimating every time you take them down and put them up again. I would imagine there's more room for error.

HTH

Andrew

Share this post


Link to post
Share on other sites

Hi Craig,

It was me that insulted your scope and suggested it may need collimating :wink:, and having read above and engaging my brain, there may be a simpler reason the stars were less well defined, I had to clean my secondary mirror quite early on due to all the condensation, could it have been that your secondary was misted up a wee bit? It was quite damp at the res. With the same eyepiece and a dry night your lovely scope should knock my old dob into a cocked hat.

I also spent about 2 hours the first time I collimated as I was a bit too liberal with my allan key twiddling :D man did I have a bad back.

Gary

Share this post


Link to post
Share on other sites

Howdy, the best advice I found when trying to find out about collimation was from the web site, andys shotglass. Even then it was a bit of a mystery looking into the draw tube and seeing al those circles. :?

I then bought an orion cheshire collimation tool from SCS and tried to collimate my 130, I think that I made it worse on that occasion.

For other reasons I then bought the book, Nexstar Users Guide and found there was a very good section in there re collimating. It recomends that for the 1st time you collimate a scope you should remove the primary mirror cell completely. This gets all confusing images away when you are setting up the secondary mirror, and gets it bang on I think. You then refit the primary and set it up with you collimation tool, whatever type you use. All that reamins is a small tweak when out under the stars. :wink:

I think my 130 is as good now as it ever was, thats after dogfish suggested it might be out a wee bit as he could see a bit of coma in it when we were out on Friday night, I then adjusted the primary just a small amount, thanks Martin...... ;)

Gary A

Share this post


Link to post
Share on other sites

When collimating, adjust the secondary first, then the primary. As much as possible, use only two of the three screws. If you start to get stressed, carefully put your tools down, and walk away from it, and get a cup of tea. Do the job of collimating with the scope in a horizontal or slightly downwards pointing orientation. That way, if you drop the screwdriver, or the secondary falls off, it won't romp down the tube and total your primary.

If you've got the secondary properly lined up, and you are having trouble adjusting the primary, don't decide you must have done something wrong with the secondary and go back to it and start fiddling with it. Your trouble is with the primary, and that's where the solution is.

Your secondary's spider contributes some to stars not looking like perfect dots. In my well-collimated scope, the brighter stars show four little points. I have a four vane spider. The effect is rather pretty, though.

There are various arrangements of collimating screws. The easiest have three screws pusshing against springs. Mine has three screws that pull, sitting beside three screws that push. The secondary has three screws that push, and one great big one in the middle that pulls. It is a pain in the Bottom, but I can still collimate it in fifteen minutes. You get used to it. It doesn't go out of collimation all that easily, so all I've had to do lately is check on it and say, "Ah, that's OK."

Share this post


Link to post
Share on other sites

Well hopefully it's bang on now. I think you may be right Gary, I never checked the mirrors to see if they were dewed up, could even have been the EP with some dew?

Anyway next weekend it should be spot on.....

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.