Sky Watcher 130PDS Collimation

[Ricochet]

7 hours ago, Jamgood said:

ike arrows. Starting from the outside, pointing inwards towards the centre. Like they are out of focus but the centre star is bang on

Sounds like coma, that's what the additional coma corrector is for. If they all point to the centre, your collimation is correct.

7 hours ago, Jamgood said:

Huge. Sticks out of the focus about 6" - I expected to be able to slide it in to the focuser but I don't have a correct fitting.

I use the FLO premium red cheshire for collimating my secondary. It slides in all the way up to the part where the top widens for the angled face. Seeing the edge of the secondary/primary will just depend on how far out the cheshire is. However, lining up the crosshairs with the doughnut is the important bit.

For primary collimation I use one of the short cheshires with the crosshairs removed as the angled face is brighter than using a collimation cap.

[alacant]

12 hours ago, Jamgood said:

This is how things look at the minute. It's hard to photograph down the Cheshire.

That's good enough. Well done.

Now stick in a coma corrector, point at a star field -anywhere in Cygnus is good ATM- and take  as long an exposure as you can without the stars trailing.

Now ask yourself if it's good enough;)

Cheers

 

Edited July 23, 2020 by alacant

[Jamgood]

I'll check it on Saturday night, weather permitting. It's supposedly going to be clear. 👍

[Jamgood]

A quick update. I got the collimation much closer to where it needs to be. Not perfect but much better than it was. I managed to get out and try it last night for the first time. 

I'm going to speak to someone at FLO next week and get a proper Collimtor Cap, a fitting to get the Cheshire right into the tube and a Coma Corrector. I'm confident enough now that if I can see what I'm doing, I'll be able to get it as near as dammit!

[RolandKol]

Hrrr,
I spent all night yesterday with that.... Ended up with perfect view via cam and Cheshire, but constantly failing to get a proper offset....

[RolandKol]

Hi again,

can you please advise, which offset I should go for?

AstroBaby's or Ocal World?
 

AstroB pic:

 

Ocal World:

[Pixies]

That second pic. Most modern Newts will have the vanes central but secondary offset.

As per the second pic, just get the green/red/blue circles concentric and doughnut/dot aligned. The offset should look after itself.

[RolandKol]

4 hours ago, Pixies said:

That second pic. Most modern Newts will have the vanes central but secondary offset.

As per the second pic, just get the green/red/blue circles concentric and doughnut/dot aligned. The offset should look after itself.

as per second pic, my 130PDS failed....

Edited October 6, 2022 by RolandKol

[alacant]

On 06/10/2022 at 20:59, RolandKol said:

my 130PDS failed

According to which criteria has it failed?

On 06/10/2022 at 15:23, RolandKol said:

which offset I should go for?

You don't/can't choose. The spider on a 130pds is central. Have you moved yours off centre?

Cheers

[RolandKol]

57 minutes ago, alacant said:

According to which criteria has it failed?

You don't/can't choose. The spider on a 130pds is central. Have you moved yours off centre?

Cheers

My spider vanes are central as per the second collimation picture (not astro baby's one).

as per failed criteria, - in the astro image, the reflection of the primary (the halo) is not concentric and creates a "funny" view.... And it stays like this during my multiple re-collimations...
if I do it central by adjusting primary mirror bolts, it becomes oval.

 

P.S. trying to target on the artificial star at the  moment... THATS A TASK!!!!

Edited October 8, 2022 by RolandKol

[alacant]

46 minutes ago, RolandKol said:

not concentric

Ah OK.

What glass is there between the secondary and the camera? Has the primary cell been brought up to the standard required for astrophotography? Has the edge of the secondary been painted black? Anything other than mirrors of a shiny nature looking down the tube and into the focuser?

Perhaps post a -link to- an unprocessed frame taken without the mirror clips so we can look further.

Cheers 

[RolandKol]

1 hour ago, alacant said:

Ah OK.

What glass is there between the secondary and the camera? Has the primary cell been brought up to the standard required for astrophotography? Has the edge of the secondary been painted black? Anything other than mirrors of a shiny nature looking down the tube and into the focuser?

Perhaps post a -link to- an unprocessed frame taken without the mirror clips so we can look further.

Cheers 

GPU or Skywatcher CC, - both give the same halo of the secondary, scope was flocked and flock material used on the secondary perimeter. 
As flock material increased the shadow of the secondary and I constantly had off-center halo of the primary, - I have removed the flock material to increase the accuracy of collimation, - so the secondary is "naked now", have not painted it. Result is the same. 
I am completely puzzled....

 

P.S. getting inside, will post some pics soon

Edited October 8, 2022 by RolandKol

[RolandKol]

The view via Cheshire (difficult to pic using mobile, but all 3 clips are visible once Cheshire is directly facing Top or turned by 90 degrees).

The 120sec raw from previous night

L__200_2022-10-06_01-40-39_T4.00_120.00s_0000.fits

 

[alacant]

2 hours ago, RolandKol said:

GPO or Skywatcher CC

Remove the cc and reshoot. The halo should be gone.

My money is on reflection being caused by the glass surface(s) of the cc. We've seen this before when the telescope facing element has not seated correctly or when a filter is cross threaded and so not sitting perpendicular to the optical axis.

A quick way to align the outermost element is to loosen the retaining ring until upon shaking the whole cc rattling can be heated. Retighten whilst moving the cc rapidly on a horizontal surface until the rattle just disappears.

No mention of the primary cell, so I assume that's been addressed.

Cheers.

Edited October 8, 2022 by alacant

[RolandKol]

12 minutes ago, alacant said:

Remove the cc and reshoot. The halo should be gone.

My money is on reflection being caused by the glass surface(s) of the cc. We've seen this before when the telescope facing element has not seated correctly or when a filter is cross threaded and so not sitting perpendicular to the optical axis.

A quick way to align the outermost element is to loosen the retaining ring until upon shaking the whole cc rattling can be heated. Retighten whilst moving the cc rapidly on a horizontal surface until the rattle just disappears.

No mention of the primary cell, so I assume that's been addressed.

Cheers.

Primary cell is not shadowed to see the clips during colimation, racked Out (away from focuser to the very end), GPU CC does not like primary to be closer due to focus point.
And I doubt it is CC issue, as both GPU and SW CC behaves the same!

But I have not tried without cc at all.. probably the last thing to test
 

Edited October 8, 2022 by RolandKol

[alacant]

11 minutes ago, RolandKol said:

both GPU and SW CC behaves the same

Of course, both will give halos on bright stars, but the halos will be of different shapes.

A shot without either will confirm.

The star is not central -causing two reflections- and there is tilt. Make certain that after collimation, the primary cannot slide around in its cell. Out of the box, they do.
Do you still have the rubber o rings in the focuser?

Cheers

 

 

Edited October 8, 2022 by alacant

[RolandKol]

20 minutes ago, alacant said:

Of course, both will give halos on bright stars, but the halos will be of different shapes.

A shot without either will confirm.

The star is not central -causing two reflections- and there is tilt. Make certain that after collimation, the primary cannot slide around in its cell. Out of the box, they do.
Do you still have the rubber o rings in the focuser?

Cheers

 

 

Yes, managed to save these tiny b.... still in place.
as per primary sliding, - not sure... it is quite firmly clipped and rotated scope does not show difference in collimation at least via Cheshire... Had thoughts to put on the silicone without the clips at all, but it will expand and etc during the night also.
Focuser... is another headache... ASI1600 + EWF is most likely a bit too much for it...
Just noticed, GPU spacing was off by 5mm.... Not sure what I was thinking, - but probably it is not the cause...

[alacant]

9 minutes ago, RolandKol said:

put on the silicone

It allows for thermal expansion and contraction of the glass whilst at the same time retaining the mirror in the same place relative to the cell. 

[alacant]

27 minutes ago, RolandKol said:

managed to save these tiny b.... still in place.

Flexible focusers? Not a good idea.

Looking forward to when the new sw150 f4 quattro takes off. That really should be fun!

Edited October 8, 2022 by alacant

[RolandKol]

6 minutes ago, alacant said:

Flexible focusers? Not a good idea.

Looking forward to when the new sw150 f4 quattro takes off. That really should be fun!

Do you mean, it is better to remove them?
I kinda, used them to tightened the drawtube to the limit as constantly afraid my camera will slip out.

[RolandKol]

No CC, using much lighter set up (ASI224MC)... 

sadly, no guiding and no proper PA, - but the pattern is the same... Halo is off... so CC is out of the issue.

autosave_stacked - Copy.fit

 

[alacant]

17 minutes ago, RolandKol said:

(ASI224MC)

So we can eliminate the camera too.

Ah well... 

Dunno. Borrow a mirror set of known performance? Try the secondary to begin with. You have now blackened the edges of the same, yes? 

Or just accept it? It's not often you'll have a star bright enough to cause reflection after all.

Otherwise, out of ideas:(

Edited October 8, 2022 by alacant

[RolandKol]

12 hours ago, alacant said:

So we can eliminate the camera too.

Ah well... 

Dunno. Borrow a mirror set of known performance? Try the secondary to begin with. You have now blackened the edges of the same, yes? 

Or just accept it? It's not often you'll have a star bright enough to cause reflection after all.

Otherwise, out of ideas:(

It is 130PDS, my GPU CC is more expensive than the scope itself  
Will go for a upgrade and forget it.

Thanks for help, at least I have stopped banging my head into the wall...

[yopero]

On 20/07/2020 at 20:14, Pixies said:

OK - that secondary needs to be moved, I'm sure. Do others agree?

I'll happily talk you through it. I'm just feeding the kids, so back shortly.

have a read of these two in the meantime:

http://www.astro-baby.com/astrobaby/help/collimation-guide-newtonian-reflector/

https://garyseronik.com/a-beginners-guide-to-collimation/

 

The next thing will be the coloured sheets of thick paper. Do you have any?

Thanks for the links! I found them useful.