Collimation required?

[Jaybeeaitch]

Hi, some advice would be very welcome.  I have owned a celestron C6xlt for about a year now.  Had a few sussessful outings, but the weather here in Cornwall has not been the best!  I have been using the 25mm plossl that came with the scope, but wanted something a bit higher power for planetary/lunar observing so just bought a badder Hyperion 10mm. Cloud cover has prevented trying this out for real so have only been able to use it for terrestrial observation.  From my back I have distant views over field to about 15 miles.  I can't actuall get the new eyepiece to come to a sharp focus.  I doubt very much this is the fault of the eyepiece, so first thought was atmospheric haze, but objects 1/4 mile away don't come to a sharp focus either.  Checking a few websites, I wonder if the scopes collimation needs adjusting?   My question is whether the 10mm eyepiece would be more demanding of collimation, asihave been happy with the 25mm plossl. I know the obvious thing is to take it outside and check against a star, but I am going to be travelling for the next month.  If I need to discuss return of the eyepiece with the vendor, I need to do it sooner rather than later.

 

thanks, John 

[beka]

If you have a slight collimation problem it will definitely be more obvious at the higher magnification of the new 10mm eyepiece. However even if there is nothing wrong with the optics, terrestrial views will look softer or more faded at higher magnifications. It will be hard to collimate on a terrestrial object, it may be possible to improve gross miscollimation if you find a high contrast object by trial and error - but to get the best result you would need to do it on a star. Although I have no experience with the procedure, apparently you can also use an "artificial star" indoors as described in this link thttp://http://www.cloudynights.com/page/articles/cat/user-reviews/the-easy-way-to-align-your-telescopes-optics-indoor-artificial-star-collimation-r2798

[Peter Drew]

Hello John, welcome to SGL. A 10mm eyepiece will give you 150x magnification which is a bit OTT for a terrestrial view as mentioned by Beka.

The Hyperion eyepiece is a good one so unlikely to be the cause of the concern. A star test will soon show if there is a significant collimation error, if no star is visible it is possible to use any small distant light source out of focus for a rough test.

[CraigT82]

Hi John, as Peter says above 150x mag is pretty high for terrestrial viewing, bearing in mind that you're looking laterally out across the landscape, through air which is close to the ground and hence subjected to all sorts of thermal disturbances so high power views like this will likely be a bit soft.

However if you suspect collimation issues there's a thread elsewhere about how to make an artificial star with a ball bearing and a torch... Could be useful for you! 

Craig

[Jaybeeaitch]

Thanks to everyone for their comments.  Once my present travelling is over, I will probably go with the Hubble 5 star, and practice collimation in the warm before going out into the cold to try it with a star.  In the meantime, I am off to the Caribbean with my terrestrial 80mm refractor.  I hope for some good skies without frost!

john

[brantuk]

I wouldn't advise collimating a Casseraine scope unless you've done one before and know what you're doing. Best to get someone who knows how, to show you first time. They can be very awkward and you'll only end up asking someone at your local astro club to help out anyway. Just a thought.

[iapa]

Time to take over a thread Thanks for starting it off JayBeeaitcH John

I managed a half dozen 40s shot of M42 the other night, Skywatcher 200P-DS, Canon 70D prime focus, unguided, AVX mount.

 

To me it looks almost acceptable; my spouse of course thought it was wonderful - she's like that . A little stretching should tidy it up a bit. In the unreduced Triangulum is fairly distinct.

However, as it's forecast to be cloudy for the next few days - as usual - i thought I'd check collimation as I am going on holiday later this year. Not planning to DO anything about it yet unless it was REALLY bad as I've not tried it before and would not want to worsen a situation. 

I prefer, check, check and check, before actually breaking something

So, I started with the vanes, seem about even as far as my eyes, and a roller, tell me.

Then a quick squint down the eye piece with a collimation cap:

In the first image I can see that the secondary mirror is not completely dead centre, but am I right in thinking that it is good enough at the moment?

The second is showing the primary is off a touch as well. I'm sure it is possible to work out the angular deviation, but 'd need to brush of my 'O' level Arithmetic.

Would it be reasonable, for the moment, to leave this as is? Or, is it just far enough off to need corrective action?