Ha Solar imaging Newtons rings woes

[Davey-T]

10 hours ago, tich said:

My focuser is part of the blocking filter & to achieve focus you twist the top of it where you'd put the eyepiece, I did get a reply back from rowan astronomy about the tilt adapter & they reckon it adds another 22mm to the optical train which probably isn't going to do me any favours either.

Time to get the hacksaw out then 

Dave

[Macavity]

We (at least I) seem to be repeating ourselves on various threads? lol. But e.g. Army Air Force's
post re. introducing a significant (5 deg?) dog-leg into the optical path is what some folk use! 
I am fairly convinced (someone else's maths) the CHIP TILT remained within focus tolerances...

I ended up (independently) using exactly the same way of adding a BARLOW into the system!

To me, there are TWO separate issues. Addressing any asymmetry in the "Sweet-Spot"? For me
achieved via "clocking" (rotating diagonal) - OR  (maybe) MINOR tilting?  Removing Newton's
Rings, by MAJOR (custom made?) Tilting seemed to be a different issue - Maybe not for me.  

But that's also a personal "aesthetic" thing too? Good to hear these issues being discussed... 

[tich]

4 hours ago, Davey-T said:

Time to get the hacksaw out then 

Dave

Sounds like it lol.

 

[Davey-T]

The LS50 seems to be doable but the LS35 seems more of a problem ?

Dave

[StarlightKnight]

You could also try Forensic filtering

https://dl.dropboxusercontent.com/u/6795661/4N6site/improc/fftplugin/howto.htm

I've had some success on certain images as you will see below.

The worse the rings the better the removal !

 

Don

 

 

[tich]

9 hours ago, Davey-T said:

The LS50 seems to be doable but the LS35 seems more of a problem ?

Dave

Trust me to get an awkward scope!!!

 

[tich]

Just got set up & got clouded out this morning but did get a few captures, I thought I'd experiment with my old Philips webcam but never really got a chance to use all the settings properly in sharpcap. No Newton's rings but the detail I were getting was pretty poor even though I was shooting it in B&W & getting 60fps which isn't bad for an old webcam. So it looks like I might have to look for a camera with a CCD chip like the Philips SPC but mono if there is asuch a thing, maybe a DMK21 would be better?
 

[Davey-T]

Just wondering if it would be possible to fit this with a bit of fettling.

Dave

https://www.firstlightoptics.com/borg-helical/borg-helical-focuser-s-7315.html

[tich]

I did look at something similar to this but I don't think it will make much difference to the inward focusing issue I'm having so looks like a 2X Barlow onto the nosepiece is the only way for me to image in Ha, I did think about getting a PGR flea2 camera earlier as it has the Sony chip which don't suffer with the Newtons rings & there's a few folk that image with them, I nearly hit the buy it button but it's a Firewire camera, ok it should work on this old laptop I guess but when I eventually upgrade I've had it.

[Joseki]

Hi, I've got the asi120mm, Lunt35 and a Rowan astronomy tilt adapter. Sadly though I haven't actually had any time to even properly test it (2016 is looking like it could be a busy summer and my HEQ5 needs fixing anyway).  However I did check a few things - with the Lunt focuser attached you can't reach focus with that setup (using the tilt adapter).  However I was able to with a standard 2x barlow.  Unfortunately the barlow made the NR problem worse & on my first attempt of using the tilt adapter I was unable to tilt it enough to fix that.  To try and get it to focus without the barlow I unscrewed the Lunt  focuser from the diagonal.  The tilt adapter screwed on to the diagonal fine.  Focusing is then only possible by sliding the diagonal in and out of the OTA (no way in 'heck' am I going to chop bits off the tube )... the only problem was then there was not enough out focus (!).  Theoretically I've solved this with a 26mm T extension tube (I got from astroboot) .. but haven't actually tested that other than screwing everything together. - without the ability to fine tune focus properly I'm not sure if it's going to be worth the effort.

 

From online reading I may just get myself a dmk camera (21AU04.AS Mono), which come up 100-150 ish used and are less prone to NRs.  I reckon my best chance of getting decent results with this scope is with the DMK, tilt adapter, a good 2x barlow and upgrading the focuser to a non-rotating one (365 astronomy stock one I think may fit). http://www.365astronomy.com/1.25-Non-rotating-Helical-Micro-Focuser-with-T-thread-and-0.05mm-Scale.html

 

 

[tich]

I'm thinking about getting a DMK or PGR camera as from what I've hear they don't seem to suffer to much with Newtons rings although I don't think I'll be buying one any time soon at the minute.

[Davey-T]

 

38 minutes ago, tich said:

I'm thinking about getting a DMK or PGR camera as from what I've hear they don't seem to suffer to much with Newtons rings although I don't think I'll be buying one any time soon at the minute.

I get NRs with PGR Blackfly.

Dave

[tich]

Won't be getting one of them then lol

[Davey-T]

I think NRs are just a fact of imaging life whatever camera you have 

Dave

 

[tich]

On 23/05/2016 at 07:22, Joseki said:

Hi, I've got the asi120mm, Lunt35 and a Rowan astronomy tilt adapter. I did check a few things - with the Lunt focuser attached you can't reach focus with that setup (using the tilt adapter).  However I was able to with a standard 2x barlow.  Unfortunately the barlow made the NR problem worse & on my first attempt of using the tilt adapter I was unable to tilt it enough to fix that.  To try and get it to focus without the barlow I unscrewed the Lunt  focuser from the diagonal.  The tilt adapter screwed on to the diagonal fine.  Focusing is then only possible by sliding the diagonal in and out of the OTA (no way in 'heck' am I going to chop bits off the tube )... the only problem was then there was not enough out focus (!).  Theoretically I've solved this with a 26mm T extension tube (I got from astroboot) .. but haven't actually tested that other than screwing everything together. - without the ability to fine tune focus properly I'm not sure if it's going to be worth the effort.

 

From online reading I may just get myself a dmk camera (21AU04.AS Mono), which come up 100-150 ish used and are less prone to NRs.  I reckon my best chance of getting decent results with this scope is with the DMK, tilt adapter, a good 2x barlow and upgrading the focuser to a non-rotating one (365 astronomy stock one I think may fit). http://www.365astronomy.com/1.25-Non-rotating-Helical-Micro-Focuser-with-T-thread-and-0.05mm-Scale.html

 

 

That's good to know I can still get focus using the tilt adapter & 2X Barlow so that's a move in the right direction, I will email 365 Astronomy about the focuser they have advertised as if it fits it does have some features better than the standard one, like keeping the camera in the same position when focusing plus it has a brass ring to lock onto the camera or eyepiece unlike the standard one which I feel is a bit cheap anyway.
As for the ASI camera I have read it needs about 6 degrees tilt to get rid of the rings so I'll try it out first before considering changing for another camera. The only reason why i consdered changing it as I tried using my old Philips SPC Webcam, yeah I know it's colour so not the best camera for Ha but on the screen there was no Newtons rings showing at all so thought it was due to it having an older CCD sensor rather than CMOS.

Edit; I just had another look at that focuser on 365 Astronomy & it looks like it screws onto the diagonal/blocking filter differently as I just removed my focuser & the blocking filter has a thread to screw onto & the picture looks like it has a thread that screws into a tube or whatever if any of my ramblings have made any sense..
Although the picture of it isn't the best.



 

[Macavity]

While I'd got everything set up today, I thought I try a comparison between
the (original USB2.0) ASI120MC (colour) and ASI120MM (mono) cameras.

(In theory) I have processed both in the same way. (Colour as Mono etc.)
and applied the same wavelets. The colour image was adjusted via "levels"
to bring it to the same level of brightness as the mono (estimated) by eye! 

My impression that the colour Cam didn't give Newtons Rings was correct
apparently! But the mono Cam is rather sharper... but has Newtons Rings!

(The result to be take [removed word] grana salis of course.... But I think it is correct.

First MONO:

Second COLOUR:

[ChrisLX200]

I had awful problems with Newton Rings when I first tried my Altair GPCAM and Quark but a simple (home made) tilt adapter cured it completely. However, the larger the sensor then the more difficult it is to use a tilt adapter and still retain focus across the whole FOV. There is only a limited depth of field within which lies the critical focus position, a small sensor can stay within that narrow range even when tilted but tilting a large sensor can take the edges outside of that. I replaced the GPCAM with an ASI178MM (which has a larger sensor) but without thinking I just plonked it into the tilt adapter when swapping cameras, but I can't say I've noticed a degradation of edge focus. Still more tests to do anyway.

ChrisH

[VilleM]

ASI120MM and Coronado PST was my headache at the beginning. Flats only didnt work because newton's rings shift over time.
Ive solved the problem by dithering my video manually with Synscan handset and also use flats to remove dust. Seems to work well, even is flats are not perfect dithering averages out pretty much anything thats left.

Bakery paper is good for flats, atleast works for me. Exposure time is quite long with Ha scope (0,5-1s) and hot pixels appear on the flats. Instead of taking darks I just run dust and scratches filter in Photoshop to get rid of them.

[Joseki]

On 24/05/2016 at 18:44, tich said:

That's good to know I can still get focus using the tilt adapter & 2X Barlow so that's a move in the right direction, I will email 365 Astronomy about the focuser they have advertised as if it fits it does have some features better than the standard one, like keeping the camera in the same position when focusing plus it has a brass ring to lock onto the camera or eyepiece unlike the standard one which I feel is a bit cheap anyway.
As for the ASI camera I have read it needs about 6 degrees tilt to get rid of the rings so I'll try it out first before considering changing for another camera. The only reason why i consdered changing it as I tried using my old Philips SPC Webcam, yeah I know it's colour so not the best camera for Ha but on the screen there was no Newtons rings showing at all so thought it was due to it having an older CCD sensor rather than CMOS.

Edit; I just had another look at that focuser on 365 Astronomy & it looks like it screws onto the diagonal/blocking filter differently as I just removed my focuser & the blocking filter has a thread to screw onto & the picture looks like it has a thread that screws into a tube or whatever if any of my ramblings have made any sense..
Although the picture of it isn't the best.



 

Just got my focuser (ordered from china via ebay ). It seems to screw on ok, though not exactly how I expected it to. Focus range is similar to the original.

[Joseki]

A better photo