Collimation?

[Dan_]

Hi there, I'm pretty new to SGL and telescopes and bought a Celestron Astromaster 130eq a little while ago.

I've really been enjoying seeing the moon in more detail than I've seen before and Jupiter for the first time! It's just amazing to see the moons! But after looking a Jupiter over a few nights I'm still struggling to see much detail in the bands. I can just make out two dark bands, but the planet appears a bit fuzzy and white. However the moon appears to be crisp to my uneducated eyes.

So I was wondering is this a case of a slightly unfocused scope? Or is it just the atmospheric conditions, or maybe I need a filter of some kind? Or perhaps I'm expecting too much? ... lots of questions!

I'm totally new to all this so hopefully I'm being clear.

Thanks,

Dan

[Doc]

Could be anyone of them. Jupiter at the moment is pretty low in the sky and you will encounter alot of disturbance in the atmosphere so this could be a reason for the poor viewing.

[yeti monster]

Probably just seeing conditions. If you doubt your collimation just get a bright star in the centre of the FoV and de focus. You should see an even do-nut with the secondary shadow central in the de-focused star. If it's offset a wee tweek of the locking screws may be enough to bring it back in, don't over tighten things though...

[dag123]

Hi Dan,

I have the same scope as you and so can compare notes.

Can I ask what eyepieces you are using, just the ones (10mm and 20mm) that came with the scope?

When I have viewed Jupiter recently, as I increased the magnification, I noted that the image started to get a little fuzzy to the point where it did not seem to be worth adding extra power. Using my X-Cel 10mm I was able to see two dark bands accross Jupiters disk. Adding the barlow and/or the 5mm EP did not make the bands any clearer at all.

Regarding Collimination, I posted a report a few weeks ago about how I sucessfully managed to collimate my scope with nothing more than a 35mm film canister, paper, scissors and a blob of blu-tac. My need for collimation was indicated while looking at stars at high magnification and noting that they were not quite right. Also when defocusing, the shadow of my secondary mirror was clearly not-central.

Hope this helps.

dag123

[umadog]

There are two differences between the moon and Jupiter. Firstly, the features on the moon are often quite high contrast, particularly when there are shadows. This makes the features easy to see. Jupiter, on the other hand, has quite low-contrast features. Secondly, the features on the moon come in a very wide range of apparent sizes. There are plenty of large features which are easy and impressive at lower powers. So you don't have to push the seeing envelope to see lots of detail. Jupiter appears small to us so you need to magnify a fair bit to see details. If the atmosphere doesn't support this then you ain't seeing those details. As others have said: wait until it's high in the sky. The higher the better.

Remember, if you use the star-test to assess collimation, that you expect to see concentric rings only if the star is in the centre of the field. The rings will not look concentric if the star is off-centre.

Focus is probably not your problem. Small amounts of de-focus are made up for by your eye's ability to accommodate.

[John]

Beyond the two main belts, details on Jupiter such as the Great Red Spot, additional bands, festoons etc are not readily easy to see in small to medium aperture scopes to be honest. As this additional detail will only be clear momentarily, during very short intervals of good seeing, you need to spend some time studying the planet - by that I mean an hour or more. If you put the time in your eye will become accustomed to the glare and will start to perceive these lower contrast details and you will also be attentive when those fleeting moments of good seeing present themselves and you can, just for a moment, see what your scope is really capable of delivering

On magnification, I'm finding 150x - 180x is delivering the crispest views of Jupiter with my 120mm refractor and 152mm mak-newtonian. More power gives a larger apparent disk, but no further detail.

[Dan_]

Thanks for all the great replies, It's good to hear what people think. It sounds like it's probably just the seeing conditions. I do get waves of detail as umadog and jahmanson mentioned, I faintly see the bands and then seconds later it turns to a plain disc. I have been spending a while looking at Jupiter but maybe I need to have a little luck getting the proper clear skies.

I've noticed the donut shape you get when unfocused, I'll have a proper look at that to see if it's central next time I get the scope out. Thanks for the tips!

Dag123 - Yes I've only got the two EP's that came with the scope, I've also got a cheap barlow but it's pretty worthless for looking at Jupiter, just a fuzzy mess. Your collimation idea sounds great! I don't have a collimation tool so if it turns out I need to do that I'll give your idea a try!

[dag123]

Hi Dan,

Just in case you need it, here is a link to the thread about collimating my scope.

http://stargazerslounge.com/equipment-discussions-help-telescopes-whole-setups/149395-i-think-i-need-collimate-my-astromaster-130eq.html

About EPs, I think you might like to think about upgrading the ones that came with the scope. The ones that came with mine are back in the box. The ones I switched too, the Celestron kit, which helpped me better understand the whole magnification-thing and the even-better X-CELs make a huge difference to what I have managed to see.

dag123

[Dan_]

Thanks, I had a read about your collimation technique! It sounds a bit fiddly, hopefully I won't have to do that just yet! But I'll have a proper check next time I get the telescope out.

Yeah I have had a look into new eye pieces, I think I'll have to get some new ones at some point, the Celestron kit looks great but is a bit expensive since I've only recently got the telescope and have a lot to learn. Maybe I will invest in some once I've got the hang of it all a bit more.

Thanks for your advice!

Dan

[dag123]

Dan,

I was very apprehensive about collination, but as many others here have said before, it turned out much easier than I thought. It is more the worry that you will make things worse that got me. The most tricky/worrisome thing was removing the primary mirror and marking the centre spot. I thnk a lot of other scopes come with mirrors pre-marked.

I think you will know when the time comes for collimation. For me it was when looking at some double-stars at higher magnifications (8mm, 6mm, and/or barlow). The star shape was flaring off to one side, even when centred. Post-collimation, the centre position is fine.

Use the EPs that came with the scope for now. I understand about the expense of the EP kit, almost as much as the scope! However for me it was all about understanding what what EP was best for what, so a wide range was good. Just bear in mind you can pay the same again, or even more, for a single EP! So when the time comes to upgrade best ask here for advice.

dag123

[todd8137]

i used my 12"reflector for a year with out touching both mirrors,when i did get brave one day and a little help from sgl ,i took the plunge ,put it this way i still can not be leave i seen any thing at all the secondary was miles out and as for the prime mirror looking through the Cheshire,the donut was about a 1 inch from the center but now most times i put it out i have a check and all is good be brave you can not break it,the only thing that made me do it was i flocked the tube and had to take every thing out.