Strange artifact on PST image ?? Any suggestions ??

[Craney]

Evening all,

With all the clear nights recently I have rather neglected the processing of  my Sun and PST data . I had a few  AVIs that needed looking at.

As I was recording them in the afternoon Sun,  I was aware that there was an artifact  on the Solar disc image which did not seem to shift or change no matter how I turned the rubber ring  on the PST barrel (the Etalon I believe ??)  or tilted the camera  ( PG Flea mono) in the eyepiece holder.   It appears as a bright chevron shaped band across the frame as below.

At first I thought it was Newton's rings due to the banding nature of the pattern, but tilting the camera  (  as in what a tilt adjuster would do)  had no effect. 

Would I expect to see the pattern change if I did this ??

I moved off the Solar disc and de-focused on some bright sky nearby wondering if I could get a 'flat' which I might use to help process the offending stripe off the image.

Here is that one.     I must have rotated the camera a bit as the pattern has shifted around. But it is still there.   Is there light leakage ??

 

Anybody got any ideas as to what might be causing this ??

Any easy solutions ??

Looking at my archived solar images with the PST ( which aren't very good), there is a hint of it being there, but nowhere near as obvious as this.

Thanks in advance for any help.

 

Cheers,

 

Sean.

 

 

Edited April 26, 2020 by Craney

[Merlin66]

Sean,

Still thinking about your problem......

It may be worthwhile unscrewing the eyepiece holder from the "black box" and checking the condition of the ITF filter (located at the bottom of the eyepiece holder tube)

Any sign of "rattling" when you shake the PST (gently!)

I've seen the collimation lens on the etalon assembly come loose......

 

[Craney]

Thanks @Merlin66

I will give it a go this morning.

[Craney]

Got the PST out this morning...( shhhushh... I'm meant to be working from home....)

Here are some pics.  BTW  the PST is horizontal and not actually aimed at the Sun apart from the last pic to get the colour of the objective coating.

 

 

There was a suggestion of a slight rattle as I (gently) shook the eyepiece holder.   Not a 'loose' item rattle, more of a component not quite seated rattle.

First Picture.......That black  serrated 'edge'  on the bottom side of the  circular aperture  seems to have the same profile as my artifact....hmmmm ??   

Looks like something has de-laminated and flaked off the coating on that component.

Is that the dreaded 'Rust' in the second pic ??   (that's a picture of the telescope end of the eyepiece holder...upturned).

Hope this helps.

 

Sean.

Edited April 27, 2020 by Craney

[Merlin66]

Sean,

The ITF in the bottom of the eyepiece holder is definitely gone to meet it's maker.....effectively dead!

You can get a drop-in replacement from Maier Photonics in the US about $110.

Could be the source of your problems......

 

[Craney]

Thanks @Merlin66     

I have just ordered one from the States.  Was listed at  $75, hope it's the right one.

https://maierphotonics.com/656bandpassfilter-1.aspx

Probably get clobbered by some form of import duty, but hey-ho!    

I'll let you know how I get on.

 

Cheers,

Sean.

[Merlin66]

Sean,

Yes, that's the replacement filter you need.

 

[Craney]

## STOP PRESS ##               UPDATE.

Filter arrived from the States.... all in, about  £90.00   with postal /import taxes and the like.

Fitting was actually quite easy once I had located a website with some clear instructions of how to do it...... which was surprisingly hard to find considering the wealth of astro-DIY

information out there.

First light was a bit tense, but everything looked good and bright on the laptop screen.  Managed to get a greasy finger mark on the surface during fitting that gave me a bit 

of  concern that the initial problem was still lurking.....

So then, the big reveal... both pics  PST with PG Flea mono ( 1000 frames... best 25% ) with a bit of a difference in processing as I was accentuating the artifact in the top one.

before

after

 

Very happy with that.   Thanks to @Merlin66   for advice on the ITF.   That artifact must have been caused by something internal  within the ITF..... may be a de-lamination ??

Now I just needs some surface Solar action.   

 

Sean.

P.S.    managed to get myself a DS unit for the PST.    yay !!!.... that makes sorting the problem out above even more sweeter.

[Merlin66]

All's well that ends well.

I'll send you a PM.

Ken

 

[tooth_dr]

Great result Sean. Looking forward to more pictures from you. 
 

Adam.