Collimating- 10” quattro

[iapa]

I took delivery of a 10”, 100mm, f4, carbon fibre the other day.

After 8 hrs aligning the secondary, by eye (with my eyesight is never going to get close ) pending using suitable tools.

I think I am getting close.

i expect some coma is not helping, CC to be ordered

the last ‘focussed’ image shows double spikes, so, looks like the vanes are twisted yet.

The off centre target is Dubhe.

appreciate if some expert can conform my conclusions.

1. Focus outward

2. Focus inward

3. Focused by eye - not even got a bahtinov for this?

 

 

 

[VilleM]

8 hours?! If I were you I would buy laser collimator. I bought Farpoint 2" laser and I can collimate my scope (f/4 with reducer to make it f/2.8) in about a minute...

Your focused image is unsharp, also your spider veins arent symmetrical, up and down spikes are off. When focusing on bright star you can see spider veins create diffraction pattern? That can be used as "bahtinov mask" to aid in focusing correctly. Also I can tell just by looking at the unsharp stars in your "focused" image that bottom left corner is going to have weird stars once you get it focused.

Once you have proper tools and done it correctly once youll see collimation is very simple. I took apart my newtonian totally and after cleaning everything and putting it back together collimation was mile (or two) off. I inserted laser, aligned secondary, then replaced laser with cheshire and aligned primary and then lock it with locking screws. Very simple and doesnt take long to do.

[Martin Meredith]

I have the 8" version of the same scope and would highly recommend using the Catseye autocollimator. Even so, the main problem is the jerky response of the secondary, so replacing the bolts by some from Bob's Knobs (or similar) is worthwhile, as is adding some simple home-made plastic washers between the tips of the secondary bolts and the secondary holder to smooth out the response. There are threads about this mod, which is often called the milk-bottle washer mod.

Martin

 

[iapa]

9 hours ago, VilleM said:

8 hours?! If I were you I would buy laser collimator. I bought Farpoint 2" laser and I can collimate my scope (f/4 with reducer to make it f/2.8) in about a minute...

Your focused image is unsharp, also your spider veins arent symmetrical, up and down spikes are off. When focusing on bright star you can see spider veins create diffraction pattern? That can be used as "bahtinov mask" to aid in focusing correctly. Also I can tell just by looking at the unsharp stars in your "focused" image that bottom left corner is going to have weird stars once you get it focused.

Once you have proper tools and done it correctly once youll see collimation is very simple. I took apart my newtonian totally and after cleaning everything and putting it back together collimation was mile (or two) off. I inserted laser, aligned secondary, then replaced laser with cheshire and aligned primary and then lock it with locking screws. Very simple and doesnt take long to do.

I agree it is easy enough. My first few OTAs were all reflectors.

As this was first try, as usually, I double/triple checked everything first - don't fiddle with the secondary alignment unless it really needs it

Didn't do the focuser.

Secondary was not centered with on the main axis of the OTA, nor on the focus tube. So, that took a couple of hours to sort, slow and methodical, .but, I shouldn't need to do that again. Just can't see if the vanes are straight or not, and as shown the answer there is not. Need more star time - only 1hr last night  

Then I just kept going back and forward getting the secondary lined with the primary - using a cheshire, and my eyes get tired easily; one reason I don't observe , and finally got to the primary.

Spent time setting up a rig for the new laser to check it was collimated.

So, 8hrs, feels about right for the 1st time with everything here.

Coma corrector on order, along with bahtinov mask. Will swap the focus motor off the 200PDS to the Quattro. 

Re funny bottom left, I dint try aligning the focuser this time. That may need doing to0

[iapa]

3 hours ago, Martin Meredith said:

I have the 8" version of the same scope and would highly recommend using the Catseye autocollimator. Even so, the main problem is the jerky response of the secondary, so replacing the bolts by some from Bob's Knobs (or similar) is worthwhile, as is adding some simple home-made plastic washers between the tips of the secondary bolts and the secondary holder to smooth out the response. There are threads about this mod, which is often called the milk-bottle washer mod.

Martin

 

I've some teflon and s/s washer on order along with replacement bolts

[alacant]

Hi. You're missing a chunk of the star  bottom and right ( image 1). The secondary isn't centred in the focuser. Use a collimating cap to adjust the secondary to be able to see all the mirror clips equally. Then use a Cheshire with crosshairs to centre the primary donut on the crosshairs. Then you can tweak the primary to perfection.

When I first started doing my f3.9, I thought there was something different I needed to do with low f numbers, whereas in fact it's the same procedure as any other Newtonian. HTH.

[iapa]

13 minutes ago, alacant said:

Hi. You're missing a chunk of the star  bottom and right ( image 1). The secondary isn't centred in the focuser. Use a collimating cap to adjust the secondary to be able to see all the mirror clips equally. Then use a Cheshire with crosshairs to centre the primary donut on the crosshairs. Then you can tweak the primary to perfection.

When I first started doing my f3.9, I thought there was something different I needed to do with low f numbers, whereas in fact it's the same procedure as any other Newtonian. HTH.

Used. Collimating cap then Cheshire.

Need to take pictures - it looked circular and centred to my eye ( nearly 6 facades does take its toll on them) and the clips looked right.

crap weather tomorrow so start again.

not doing anything different, just not got the eyes for the greater accuracy required.

got a web cam on order to get decent pics through the cap and Cheshire - will make a frame to get them lined up 

 

[alacant]

18 hours ago, iapa said:

Collimating cap then Cheshire.

Hi. It's this image I'm referring to from your first image; the defocused star is not circular. The bottom and right right is missing which changes to top left on the other side of focus. The Cheshire will get you close. For the final star test, you can use live view whilst you tweak the primary adjusters. Or better, have a friend to tweak them whilst you keep the star centered. I don't think you'll be able to reach both manually on a 10" so your camera's live view on a laptop screen is invaluable. Also attached is a view through my Cheshire/sight tube just before the star alignment; notice the offset. HTH.

EDIT: forgot to say. Star test. No correctors or filters and with the star dead centre of the field of view.

[iapa]

6 hours ago, alacant said:

Hi. It's this image I'm referring to from your first image; the defocused star is not circular. The bottom and right right is missing which changes to top left on the other side of focus. The Cheshire will get you close. For the final star test, you can use live view whilst you tweak the primary adjusters. Or better, have a friend to tweak them whilst you keep the star centered. I don't think you'll be able to reach both manually on a 10" so your camera's live view on a laptop screen is invaluable. Also attached is a view through my Cheshire/sight tube just before the star alignment; notice the offset. HTH.

EDIT: forgot to say. Star test. No correctors or filters and with the star dead centre of the field of view.

Hi

Yeah, I got that, about not circular, and loosened the spider bolts again (loose when it arrived), and remeasured and micrometer showed <0.5mm left/right and same up/down ( using focuser as 'up'). All 6 mirror clips visible and appears even - need picture and measuring for that, for tomorrow. Well, I have from 22:00-03:00 mostly clear

May need to remove and realign focuser - but that is for later

Cheshire had the mirror slept in its cross hairs, and laser collimation on primary looks OK (I have a cross hair hotech).

fingers x'd.......

 

 

[alacant]

9 hours ago, iapa said:

 loosened the spider bolts

Hi. Hope by now it's sorted but if not, I think it maybe the secondary displacement toward the primary that is causing the light loss. On my 208mm, the instructions are to centre the the spider -use compases to make certain it is-. then give 3mm (2 turns anticlockwise on the secondary centre bolt) displacement. ES tell me that if the centre bolt is dead centre in the tube, then the required displacement away from the focuser is taken care of. On a quattro that may not be the case and you may have to perform both displacements yourself. 

 

9 hours ago, iapa said:

loose when it arrived

I've never believed that proviso, '...may need slight adjustment from factory settings due to handling during transit...' OWTTE. What it should say is, 'Needs to be pulled apart completely, reassembled and collimated immediately upon receipt.'.

9 hours ago, iapa said:

laser collimation on primary

When you have the cross hairs of the sight tube coinciding with the donut on the primary, does the laser still point dead centre of the primary?

Anyway, hoping by now this will all be in the past. If not, HTH.

[iapa]

I started from scratch - might as well.

so, still needs more fine tuning - will strip out the bolts etc and apply a LITTLE lubricant 

1st image to show orientation.

looks to be around 0.5mm off centre top/bottom and left/right

 

THis confuses me, the reflection seeems to be circular, just not sure why it is not same size as the dark circle which should be the  frame of the secondary.

May be why I can’t get a ring around the mirror ( REN and blue card in place)

This is supposed to be through Cheshire to show cross hairs re;active to centre spot and also laser to centre spot

Lastly , primary collimating via laser

Still far from perfect, but getting closer I hope.

see what tonight brings

more to read - and also need to check laser collimating, seems slightly off.

 

 

[alacant]

Hi. This one shows the bit missing in the star test. I think the secondary needs moving toward the primary and then rotated and tilted correctly to make it look right. Here's the view through my cap. HTH.

[iapa]

Yeah,

0.5mm is too much deviation I think.

its a slow process to get it all right, but, I will develop the necessary patience.

only got this about a week ago, and I’m a slow learner

eyesight is my challenge ?

and the difference between Cheshire and laser needs resolving.

also not sure focusser is square - best part of image seems to be right of centre

and lots of coma. I expected that but not quite as much as this

[spillage]

Hi @iapa

I am by far no expert but I am not sure this is coma and looks possibly like a tilt issue. I was sure that if it was coma it would be on all around the outer edges not just on one side.

spill.

[alacant]

15 hours ago, iapa said:

best part of image seems to be right of centre

Hi. Unfortunately, until this is concentric -with the tilt and rotation of the secondary corrected-, the images will always be tilted . You may want to replace the blind adjusters with some screws to help with the secondary, so obviating the use of Allen Keys. Nearly there:)

[iapa]

53 minutes ago, alacant said:

Hi. Unfortunately, until this is concentric -with the tilt and rotation of the secondary corrected-, the images will always be tilted . You may want to replace the blind adjusters with some screws to help with the secondary, so obviating the use of Allen Keys. Nearly there:)

Yeah

I've replacement bolts on order too

just lots of little tweaks

i always knew this would be more challenging than my others.

 

[spillage]

I know these can be a struggle and it is always one of those scopes I have kept going back to look at just for the fact that I would love the chance to set on up.

I would strip it down, centre the focuser first, fully flock it and then rebuild it.

I always set up my secondary when they are sloppy so I can look down the cheshire whilst you can move the mirror up down and rotate it freely to get a feel for where it needs to sit. This is probably completely wrong but its my way.

keep with it as I cannot wait to see the images its produces.

spill.

[alacant]

59 minutes ago, iapa said:

replacement bolts

Simple m4 bolts with a nut tightened to the head is all you need.

15 minutes ago, spillage said:

cannot wait to see the images its produces

+1. Should be amazing.

1 hour ago, iapa said:

more challenging than my others

That's what I thought, but in fact you perform exactly the same steps as any other Newtonian. I found that there is so much negative hype about the impossibility of collimating anything faster than f5 that in the end, you begin to believe it! Perfect it doesn't need to be; close, yes. Even closer now...

 

[spillage]

Came across this so not sure if you have seen it. Dion gives a full mods and tweeks guide in astronomyshed.

[iapa]

1 hour ago, alacant said:

Simple m4 bolts with a nut tightened to the head is all you need.

+1. Should be amazing.

That's what I thought, but in fact you perform exactly the same steps as any other Newtonian. I found that there is so much negative hype about the impossibility of collimating anything faster than f5 that in the end, you begin to believe it! Perfect it doesn't need to be; close, yes. Even closer now...

 

I’ve no worries about getting it there

it 60mm M4 knurled hex head and a bag of nuts thats on order

And then that last little.... damn, it’s miles off again

LOL

[iapa]

Stripped right down

centred vanes, still around 0.5mm off?

measured and marked centre point t opposite focusser using a silver gel fine tip pen.

adjuated focusster using Cheshire, difficult to get image through Cheshire but I think you can see it’s close.

checked  laser, which seems to match Cheshire, so, I’ll take it the laser collimating is good (I rotated it gently and spot stayed in centre of cross) The silver gel mark shows nicely here.

 

 

 

[spillage]

It might be my eyes but the secondary vanes look central to me. Getting closer to seeing light though.

[iapa]

2 hours ago, spillage said:

It might be my eyes but the secondary vanes look central to me. Getting closer to seeing light though.

If you zoom in, the 1st (left to centre) is 134mm to the bolt hole edge. The 2nd (tight to center) is about 133.5mm

that's probably “close enough” for the time being.

away to a spa for next 2 days so no updates until weekend everyone will be pleased to know ?

[spillage]

 Spa..Now that sounds like a nice idea.

I was looking at the outside edge as they both seemed to show 121mm.

spill.

[iapa]

1 hour ago, spillage said:

 Spa..Now that sounds like a nice idea.

Yup, SWMBO suggested it - outdoor jacuzzi too. Was tempted to take a smaller rig, for the evenings, but decided against.

some wine in a warm jacuzzi just looking at the stars won out

 

1 hour ago, spillage said:

I was looking at the outside edge as they both seemed to show 121mm

I was looking at inner edges as they’re closer to the central adjust/mount bolt

anyway, thanks for the positive assertion