ED80 Issues (Help!)

[sross58]

Hi,


I have purchased a secondhand SW ED80, i am having issues, i dont think its focusing issues, although it does look like it, i fear a collimation issue but hoping for something less serious.

I took it out for a test the other night and pointed at ETA Carina Nebula and again tonight to confirm that it wasnt dew the first time. I posted the issue on another page to which people replied its dew, it is 100% not dew.

It only seems to occur on the brighter stars, as you can see in the pics below.

I have also taken a shot of Sirius for comparison.


Image details:
ETA Carina single shots x 2, 25 sec, ISO 1600.
Sirius Single shots x 3, 1 sec, ISO 400

Gear:
Skywatcher Pro Series ED80 (Gold)
Canon 60D (Not-Modified)
Skywatcher EQ5 Pro Mount

Pic 1: ETA Carina 2 nights ago (Focused)
Pic 2: ETA Carina tonight (Focused)
Pic 3: Sirius (Focused)
Pic 4: Sirius (Unfocused)
Pic 5: ETA Carina (Same focus as pic 4)
Pic 6: Sirius (Out of focus the other way)
Pic 7: Acrux double star to show its in focus


Any help would be much appreciated


Regards

[Merlin66]

I have and use three different ED80 scopes.
What I see looks like pinched optics ( the notches visible at the edges)
I fixed one (an older York ED80) which had similar, by easing the collimation screws...but the SW 80 - I honestly don't know - I've never had to adjust the collimation.
May be some other user can comment.

[sross58]

Thanks for the reply Merlin,

I cleaned the lens today and noticed that there are finger prints inside on the outer edges of the glass, so someone has had it open i guess.


Does the (Pinched optics) cause that halo around the stars though?

[astronobob]

Have Pm'd you Ross :thumbsup:

[astronobob]

https://www.telescopenerd.com/telescope-astronomy-articles/ed-glass-and-telescopes.htm

[Merlin66]

Sam,
Dr Google doesn't have much to say about collimating the SW ED80...
The nearest I could find was the CN discussion:
https://www.cloudynights.com/topic/40828-help-me-with-collimation-of-my-80ed/


This infers the front cell is just screwed onto the tube with no other adjustment.
I just unscrewed the cell from my ED80 and I can't see any collimating screws within the cell.
The spacers - do they intrude much into the lens???


No, collimation would not cause those halos. Did you have any optical elements - filters etc in the optical train when you imaged?


If not, then to me it feels like the objective is not assembled correctly....

[sross58]

Hi Merlin,


Have spoken to the previous owner and its possible the objectives weren't assembled correctly after cleaning.

So, perhaps the front objective is in back to front.


A bit apprehensive about opening it up, i cant find anything online to direct me.


Will give it a go though, should be fun.



Regards

[Merlin66]

Sam,
PM sent.....

[Nikolas]

unscrew the front end

[sross58]

This ring Bob?

[astronobob]

Yes, If that was not between the 2 lens's then try it between the lens's ?

Here a pic of how the lens configuration is when in scope -
Light enters from the left , so its important the outside lens surface is ConVex as in the pic

[astronobob]

Have been communicating, & we now have sharp Focus :thumbsup:

Rgrds

[Nikolas]

So what was the fix guys?

[astronobob]

Yes, Nik, The Double Convex objective was in back-to-front. I assume the convex's are of a different curve radius ?

There is still a slight fogging issue, tho seems like either very high humidity in Melb recently & currently I see its still averaging 90%; 'Or' maybe a slight possibility of a very thin smear/film left from cleaning ?

Rgrds

[Nikolas]

thanks :)