Collimating worries.

[Dubbs75]

Evening all,

I wonder if anyone knows of any clubs near me (Tipton) that I may be able to take our scope along to for some collimating tips. We own a Skywatcher 200 on an EQ5 goto. We upgraded from a Powerseeker 127EQ about 4 months ago. We tried collimating the old scope but ended up getting into a bit of a pickle so we're concerned about making changes to the more expensive scope. To be honest we are not sure whether it needs collimating or not. We've watched some vids on YouTube by Astronomy Shed but we've not answered the question if we need to collimate or not, hence the question about local clubs (or members of SGL who may be local and able to help).

Thanks guys!!!

[umadog]

You will want to check and potentially tweak the collimation each time you view. If you have a sufficiently accurate collimation tool you will probably find that it needs at least a quick tweak each time. Being a solid-tube, though, it should maintain collimation rather well.

[bish]

Hi Don't know if you have seen this Astro Babys Guide to Collimation

As umadog says the scope will hold collimation well.

[Moonshane]

collimation is simple but you do need the basic tools.

a collimation cap (home made with a 2mm hole) and a Cheshire will suffice.

it's something you will be able to do in less than a minute when you get the hang of it. for now and assuming the view is reasonable, just wait until you can get someone to help. if you can collimate a scope out of collimation, you can collimate it back so don't worry about ruining the scope, unless you drop something on the glass it's all resolvable.

[spaceboy]

You ideally need to learn collimation for yourself. If you take it along to a club the chances are you will never want to touch it again in the hope it remains collimated. Unfortunately this is not the case and newts need tweaking every now and again. I agree the newer models hold there collimation much better than the older Helios and Blue tube SW's but if you are regularly handling the scope when setting up it is inevitable it will get knocked out. The link in Bish's post is an excellent guide and tells you every thing you need to know. I'd personally advise a Chesire over a laser collimator but others may disagree. As far as I am aware the nearest clubs around here are Wolverhampton, Walsall, Birmingham campus and Bromsgrove rugby club. A quick search of the net will bring up their locations.

[zedds]

Hello Dubbs.

I have the same scope as you and found AstroBabys guide a massive help.

There is Walsall Astronomical Society based at Rushall Olympic football club in Rushall. HERE is a link to their site.

Hope this helps.

[umadog]

Here is how to use a cheshire/sight-tube combo tool. John Reed Home Page Collimation - Cheshire

The sight-tube part is used for rounding the secondary and pointing it at the primary. The cheshire part is used to adjust the primary. The collimation cap is a cheshire, but without a sight-tube bolted on. Because there's no sight tube you can't adjust the secondary mirror accurately.

A laser needs itself to be collimated to use it for pointing the secondary at the primary (adjusting the so-called focuser axial error). For adjusting the primary you can barlow the laser and project the mirror spot back onto the focuser. When doing this, it doesn't matter if the laser is collimated.

[Dubbs75]

Thanks guys. Now it looks like the skies may be poor for a few days I'd like to try and collimate . The reason I asked about someone helping is my belief that two people can look down a Cheshire and have differing opinions of whether the scope is in or out. It's a wonderful hobby!!!

[Neil McRae]

Maybe I am lucky but do you really need to collimate a scope so often ?

I collimated the scope when I received it and since then have done it twice in a year and found that it was perfect each time.

Star testing also showed a perfect "doughnut" when slightly out of focus.

What would cause the scope to go out of collimation if it was not dropped or jarred etc.

I could understand that thermal differences may cause very small departures of alignment but if the scope is handled with care and not roughly transported there should not be a problem.

Maybe someone can enlighten me.

Neil

[spaceboy]

I put it down to those Gremlins myself.

[assasincz]

Hello Dubbs75,

You can check whether your scope needs collimating pretty easily - do a star test. Pick a very bright star, put in a more powerful eyepiece (magnification 150x should suffice), place the star in the middle of your field of view a take it out of focus in both directions.

If it looks something like this (depending on seeing conditions)...

http://www.willbell.com/tm/IMAGES/StarTest2.jpg

...then you do not need to worry.

If the circles are not concentric, then it is time to collimate your scope. But you can get that sort of tip everywhere anyway

[Moonshane]

I check my collimation every time but sometimes it needs tweaking and sometimes not. it's not a big job and I do it while the primary cools.

[spaceboy]

it's not a big job and I do it while the primary cools.

Not teaching yer granny to suck eggs but you should wait until the mirror has fully cooled before collimating Shane

[Moonshane]

it's never made a difference whenever I have done it before and then checked again afterwards. good point though - should have mentioned I do a check and tweak and then a final check later.