Newbie help with Jupiter

[rob3910]

Good afternoon! I have drilled a 2.5 mm hole dead centre in a spare lens cap. Here's a couple of pics of what I am looking at..

I don't really know what I am looking for to be honest but the reflection of the secondary mirror looks off centre to me??

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[rob3910]

Just to clarify what I mean if I haven't worded it correctly, in the first pic the reflection of the inside of the lens cap and my eye isn't central in the reflection of the secondary mirror?

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[happy-kat]

I am absolutely no expert on this. I too am learning what collimation is about.

Taking the 4 spider vanes to the secondary mirror. I am guessing these should be all equal in length so the mirror when you view the scope from the open tube end is dead centre.

It is OK that the bit in the middle of the reflection is biased one side as you have a fast scope but first I think need to confirm your secondary is correctly placed. I used a ruller on mine from the open end and carefully measured the placement. Yours does not look to bad.

There are lots of good guides, I like the one Moonshane has but I can't find it right now.

[happy-kat]

Found it, I found it good to follow.

http://stargazerslounge.com/topic/197640-collimation-and-star-hopping/

[Northern Soul man]

Hi Rob, Happy Kats I think is correct, only I've not collimated a Dob/Newt for absolutely years now, it looks like the whole secondary mirror needs to be moved over to the right a little in the image.  You can also see the chamfur of the secondary mirror - so the tilt of the secondary is out a  little.  First you need to centralise the secondary mirror holder in the tube, it needs to be moved over to the right a little, you may be able to loosen the vane on the left and tighten the vane to the right - this may move it enough.  The dark central piece is also out of line, but I think you need to centre the secondary in the tube first before you can adjust anything else.  If you have a long draw tube that slides inside the focusser, you can extend the draw tube out as far as you can - this will show the mis - alignment better.

Paul.

[rob3910]

Thank you both, I have had a play about with it and read moonshane's article, it was really helpful. I'm finding it difficult to make out perimeters of things now the natural light has gone, I'm struggling doing it in the living room with the big light on so I will have another go tomorrow after work. I think my main problem is actually identifying what exactly I am looking at!! If I still can't get my head round it I may see if someone in my area will run through it so I am certain of how to do it again. Would I be right in saying To centre the secondary I would adjust the 3 screws behind it at the top of the scope?

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[Northern Soul man]

Hi Rob, you need to adjust the length of the vanes (the four lines going from the outside of the tube to the centre of the tube which actually hold the secondary mirror in the centre of the main tube) towards the top of the main telescope tube, there should be little screws on the outside of the main tube - you need to loosen the screw on the outside of the tube and tighten the screw directly opposite it to move the whole secondary mirror and support towards the right hand side of the tube in your first picture to centralise the secondary - you want to end up with each circle inside each other circle (moving out from the centre) to get collimation spot on, but you need to make sure the secondary mirror is central in the main tube before you start - as Happy Kat said its not too far out - so just start with very small adjustments, wonder if you are anywhere near me in the Midlands -  could pop over and help.

Paul.

[rob3910]

Hi Paul, I'm about 2 hours from you in Rochdale otherwise I would drive over, thank you for your offer, much appreciated! I understand you know, I didn't think of adjusting the secondary mirror in relation to the tube, I just thought you adjusted the mirrors themselves with the respective 3 screws. I will give that a try. And do some more reading!!

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[rob3910]

Edit* I understand you * now, not *know. Haha.

[Northern Soul man]

Ok Rob, Thanks, yeah the three screws at the back of the secondary, just tilt the secondary in the tube for fine tuning.  once you have the secondary centred in the main tube you can then begin to collimate.  Not sure on your scope wether you can adjust the main mirror at the bottom of the tube using the mirror clips that hold the mirror, you should be able to see the mirror clips (around the edge of the main mirror, in your first picture they look like oblong bumps positioned at about 12.30 o'clock, 4 o'clock and about 8.30 o'clock) in the secondary, if you can see these clips, then the main mirror is very close to collimated as in your first picture.

Keep in touch mate.  Paul.

[rob3910]

Thanks Paul, will do!!

[buzzlightyear]

You could check if there is a telescope shop in your area and ask them if you could bring it in for them to show you and check it for you.

A good dealer will be glad to help.

[happy-kat]

Take your time :-)

Before moving anything use a ruler and measure if the secondary is in the middle can also use paper to help, I did a look don't touch approach when I started.

[Moonshane]

in the first pic your secondary needs to come 'down and to the right' i.e. towards the primary

you then need to adjust the secondary tilt and primary - you are not too far away.

[rob3910]

Thanks moonshane, I will spend some more time on it this evening. I have got my head around it now, I think the penny has dropped. Initially I didn't realise you could actually move the secondary, I thought you could just adjust the angle of it. Rob.

[Moonshane]

the main thing is just be very careful about undoing the central bolt too much as the secondary can drop.

I generally take it right off to check the length of the thread and then count the number of turns you have to get it right. you then know roughly how much of the bolt is still inserted.

if I do this then I sometimes epoxy a threaded rod in and use a nut to adjust the position as this was you can see how much thread is left more easily.

[rob3910]

Great idea, thank you.

[Northern Soul man]

Great input for you Rob, just a thought though, don't get too wound up about perfect collimation  -a lot seem to think that the performance of the scope solely relies on absolute perfect collimation, looking at your pictures you posted earlier in the thread shows that its not too far away and by getting perfect collimation, its going to drastically improve the views and make Jupiter come alive with a wealth of detail.

Just do a little experiment if you can and have a look at, say the Moon, if you haven't already done so - your views will be breathtaking and you will forget about a slight mis - alignment.  The unsteady atmosphere will degrade the views far more than the slight mis - alignment you have now, even doing a star test will give very nice views and you may only just notice your collimation when de - focusing a star making it flare slightly in the direction that your alignment is off - but not a great deal - not making too much difference to the views and still very enjoyable.

Paul.

[rob3910]

Thanks Paul, I think my main problem I have been having is not spending enough time at the ep and the seeing not being so clever. Even on the few times the sky has been clear ish the stars have had plenty of twinkle in them, which I have been told is not a sign of a steady clear night. I think I will try and do some small adjustments but nothing drastic. If I can get the alignment a little better well that's great, but if I struggle to make any positive changes then I'm not that bothered to be honest at this stage of the game. I need to get my head into my new books, Haynes manual of astronomy, turn left at Orion and will trion's Cambridge star atlas. I could do with knowing more about the night sky before I can run! I will try and get it a little better If I get chance later, but like I said, if I can't I won't loose sleep over it.

[Northern Soul man]

Nice 1 Rob, its a little daunting at first but you'll soon get the hang of things - excellent choice of reading matter though.  Visual is, I think (I'm biased here) is a step up from just looking up at the night sky and just wandering whats up there, to just having the scope set up before a nights observing - even with Binoculars, you get a whole different outlook (pardon the pun) on the sky, it opens it up to a wealth of star fields, double stars, different coloured double stars and misty patches of light that are just waiting for a little aperture and magnification to explore them.  As with the books, you get, I think, a little dis heartened when you think that the pictures/images on the web and in the books are what your going to see visually, but once you get an idea of whats up there for us to see with our Bino's and scopes and understand just how long the light has been travelling from each object to reach us (just think the light has been travelling that long that some of the stars may have already gone Supernova by now) you begin to realise just how fascinating this hobby is, the best is you can delve as deep as you want to or just become a casual "looker upper".  The trouble is though, that once you get hooked, the infections called aperture fever, photo/imaging and just down right becoming a star gazer bite you before you know it you end up like me - a forty something man that creeeps around his garden with a silly red light on his head!!!

 Paul.

[rob3910]

Haha, I suppose I've got all that to come!!

Well I've made some adjustments to both mirrors and adjusted the secondary mirrors position in relation to the focuser tube slightly also so everything lines up, here's what I am looking at through my drilled film cannister...

As you can see the veins that hold the secondary mirror bolt are non adjustable so I've made slight adjustments by backing off the 3 adjuster screws and loosening the main bolt slightly. Would you say I'm any closer? The only thing that worries me is that I can see the side of the secondary mirror housing in the reflection in the primary slightly, as though it's at a slight angle?? Everything else looks plumb to me...

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[Northern Soul man]

Great Rob, you've done a fine job there mate, the reflection of the back of the film canister needs to come down towards the 7 o'clock position I think and there seems to be a little more of the top mirror clip (near to the 12.30 o'clock position) showing, the secondary mirror looks as it needs to be pulled back towards the top of the scope - but only ever so slightly - not sure if you can adjust the whole secondary housing though I'm not familiar with the scope -  but there isn't much needed to get it spot on.  A slight adjustment on the tilt of the secondary will hide the secondary mirror holder, you've done a very good job - only really small adjustments needed now really well done.

  You can keep messing with it all day, as said before there really wouldn't be much of a difference though if your anything like me, when I first started I had an 8" newt and I used to spend hours trying to get it right - but the more you adjust and see how things alter by adjusting different mirrors and after a while you will only spend seconds adjusting and not hours like I used to.

To say its your first time collimating, you've grasped the concept a lot better than I did Rob - all the best.

Paul

[rob3910]

Thanks Paul! Great to know I'm making progress, I will make some more adjustments once the children are fed, watered and put to bed, and what's more important the forecast for tonight is clear spells so I might get a chance to see how it performs. I can totally relate to you spending hours messing with collimating, it's took me a good few hours just to get my head around what reflections move with what screw!! Rob.

[Northern Soul man]

yeah, nice 1 - the clouds are thick and fast here, just checked the weather and not sure if its going to clear here or not, could do with trying the web cam on Mars, but the planet is really low down and I have a row of houses running from sort or SE, round to the South and a little further over towards the West, so not really ideal, but Mars and Saturn are really low in the sky this year, so, having to fight with the atmosphere is going to be the major problem this time around, I had an 8" SCT last time Mars was on view, so would like to see if I can get some better images with the 11".  Mars and Saturn will be close to the roof tops of the houses though, having Jupiter so high up has been really nice, checking the threads, we've had some really excellent images of mighty Jupiter - just goes to show that with small scopes we can see an absolute wealth of detail and capture it from our gardens.

Nice to know your enjoying the new scope and having a good time under the stars mate.  Keep in touch and let us know how your getting on Rob.

Paul.

[rob3910]

Will do, managed to get the scope out for a couple of hours last night, didn't change anything collimating, just made the most of the ckearish skies. Managed to get a good look at the moon for the very first time, it was breathtaking. I couldn't beleive how much detail I could see. Managed to get the focus bang on and got some great views. Here's a quick pick I took with my phone..

It was awesome to see. Hopefully going to the observatory in todmorden tonight, even though we have cloud forecast I may still be able to get some good advice and maybe some hands on collimating experience. Rob.

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