Yesterdays efforts

[simmo39]

Rushed home from work yesterday to set up as the sun was out. I only took a few vids as the heat was not good but when i started looking at the data i seem to have alot of verticl lines as well as the dreaded newton rings! Anyway here are the results taken with my Daystar Solar Scope and a ASI 120mm. Hint tips and pointers most welcome.

thanks for looking.

[Davey-T]

Apart from the seeing being flipping awful all week which hasn't helped, for the NRs you could try a cheap .5x focal reducer just to move the focal point a bit, I found it helped with my setup and,  a bit more expensive, a tilter which can also help.

Dave

Edited August 1, 2020 by Davey-T

[Macavity]

The ASI120MM seems to have something of a propensity towards producing Newtons Rings? 🙄
Oddly the "MC" did not. But, as noted, slight changes to the optics can sometimes work wonders.
Sometimes patterning is a Moire-like effect. Can be helped (worsened!) by resizing an image? 😛

[simmo39]

27 minutes ago, Davey-T said:

Apart from the seeing being flipping awful all week which hasn't helped, for the NRs you could try a cheap .5x focal reducer just to move the focal point a bit, I found it helped with my setup and,  a bit more expensive, a tilter which can also help.

Dave

Hi Dave, I have been looking into another reducer I have got one fitted that I found  but Im not sure if its 0.5 or 0.75 lol. I have a tilt adapter fitted and have tried it at loads of tilt angles an  it doesnt seem to make a lot of differance. Ill keep plugging at it though.

12 minutes ago, Macavity said:

The ASI120MM seems to have something of a propensity towards producing Newtons Rings? 🙄
Oddly the "MC" did not. But, as noted, slight changes to the optics can sometimes work wonders.
Sometimes patterning is a Moire-like effect. Can be helped (worsened!) by resizing an image? 😛

H, saving a few pennys for a new camera at the moment ( need to sneak it in past the wife! lol ) Im look at either ASI 178mm  or  ASI  290mm. I have asked in another forum as to which would be better.

[Davey-T]

16 minutes ago, simmo39 said:

Im look at either ASI 178mm 

I use the ZWO ASI178MM on my Lunt LS60 and don't get NRs but no idea about the Daystar, nice camera though with small pixels.

Dave

[xtreemchaos]

great shots mate, what a lovely prom. charl.

[tooth_dr]

Very nice Simon. I have a tilter and in my experience I also cannot get rid of the N rings that my 120MM produces no matter what angle I try. The 290MM i bought did give NRs but these were completely resolved by the tilter.  

[Rusted]

Could the protective filter glass be the cause of the MM's Newton's Rings?

Slightly wedged? Or not wedged enough? Not sitting flat?

Easily removed for a test without it. Just be careful replacing it.

 

[Merlin66]

Rusted, et al,

The Newton Rings are caused by the sensor chip cover plate, the exterior coating (AR), thickness and material all have a part to play. This “cover” is an integral part of the chip and is not removable.

I think you be thinking of the protective “window” added to most (all?) the current cameras - these can be removed for cleaning.

Some chips are more prone to NR than others. The only “solution “ is to change the effective thickness of the cover by tilting.

[Rusted]

Thanks. I was referring to the removable window.

EDIT: I should have added that monochromatic light is the standard method for checking optical surfaces using Newton's Rings.

H-alpha will reinforce the intensity of the rings compared to white light.

Edited August 2, 2020 by Rusted

[Merlin66]

Ok.

But the front window has nothing to do with the NR

 

[grimble_cornet]

I gave up trying to solve the Newton's rings problem with the ASI120MM years ago having tried tilting (needed almost 5 degrees and even that didn't work with Barlows or Powermates), flats and even Fourier transforms. Eventually bought a Point Grey Grasshopper CCD camera which has given me great results for over 5 years. I bought an ASI290MM a couple of weeks ago for EAA use but decided to try it out with my Lunt 100Ha on the large prom. Yep.......... the Newton's rings are there but not as bad as with the 120MM. I managed some prom images without any correction and the much faster frame rate (compared to the Grasshopper) could be a real advantage.

[simmo39]

3 hours ago, grimble_cornet said:

I gave up trying to solve the Newton's rings problem with the ASI120MM years ago having tried tilting (needed almost 5 degrees and even that didn't work with Barlows or Powermates), flats and even Fourier transforms. Eventually bought a Point Grey Grasshopper CCD camera which has given me great results for over 5 years. I bought an ASI290MM a couple of weeks ago for EAA use but decided to try it out with my Lunt 100Ha on the large prom. Yep.......... the Newton's rings are there but not as bad as with the 120MM. I managed some prom images without any correction and the much faster frame rate (compared to the Grasshopper) could be a real advantage.

Hi, thanks for the info, BTW  great vid!

[grimble_cornet]

These are the results I used to get with the ASI120MM in Ha - I even got them in CaK if I used the dreaded x2.5  Powermate which is famous for exacerbating the problem!

The tilt adapter image came from an article I read at the time - sorry I can't remember who I 'borrowed' it from - but it reflects my own experiences. I bought an early, commercial tilt adapter but had to fit longer bolts to get enough tilt. Without a Barlow or Powermate I could just about get rid of the Newton's rings by tilting and using flats but it was hard to maintain focus across the fov.

Incidently, just reinforce Merlin's comment - my very early ASI120MM did not have a 'window' and produced the most extreme Newton's rings of any camera I have tried.

 

Mike

 

[skybadger]

  I find it unrealistic to think that the Sony chip assembly process cannot repeatedly place the cover glass to a high degree of alignment. How do other cameras of the same chip compare ?Maybe it was intentional to avoid white light fringing in consumer optics. 

It's also interesting that the telecentric power mate is being blamed for  making it worse, is that because of the telecentric nature of the optic keeping the wavefront flatter than others, effectively reducing introduced wedge and keeping ring contrast high ? 

Finally, there must be an impact of the front glass, it's equally an optical cavity , both between the two glasses and internally to itself, so in total there are three potential sources of these rings, chip to cover glass, cover glass internal, window internal, all about the same distance and therefore width and contrast of rings. 

I use the ASI120 and power mate on the quark and have just these problems.I also tried the tilter, but the degree of tilt suggested would really throw out focus.

I haven't a solution yet but it's worth me trying my other ASI. 

 

[Merlin66]

I understand your concern, but the NR can only arise between very closely spaced surfaces. The cover plate on the chip I’m sure is 100% designed for the normal camera application, not for narrowband Ha solar imaging. The spacing of the coverplate to the silicon  is restricted, likewise the thickness of the coverplate.

The front window is to far from the chip to generate NR.

Note, NR May be generated in Ha wavelengths, but not an issue when Imaging in CaK.

[Macavity]

I found "personal salvation" with an old style (CCD!) Chameleon / FLIR camera.
But previously, I had battled considerably with NRs! But "monochromatic" light
provides quite a severe test for (any) optical system? 🙄

Randomly: I did actually make an "artificial star" and TESTed my ST102... It gave
[IMO] *splendid* diffraction patterns with the Baader "solar continuum" filter. 😎
ST refractors are (anecdotally?) "a bit rubbish" with white light, but...

To some extent "in the lap of the gods"... But I do pay attention to concensus.
Aside: Not quite sure what particular "magic" is inherent to CCD over CMOS? 🤔

Edited August 3, 2020 by Macavity