Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Green in comets is not CN, cyanogen

  • Please log in to reply
86 replies to this topic

#76 JoRy

JoRy

    Lift Off

  • -----
  • Posts: 5
  • Joined: 03 Jul 2018
  • Loc: Finland, Helsinki, 60N

Posted 24 January 2019 - 05:04 PM

Yes, my 12"f/4 Newton uses "Boren-Simon"/TS2Korrr 0.75x coma corrector/reducer which give an effective focal ratio f/2.9. Also I use bin2 with QSI690, which again about quadruples sensitivity. All these parameters together with ICX814 chip QE being almost ~60% at 387nm are perhaps the key elements to get enough UV photons, but still signal-to-noise ratio is bit too low when imaging most medium/low brightness comets.

 

Here is a link to my 21P/G-Z CN filter observation from September 2018 https://www.taivaanv...ions/show/77387, SN is quite low but CN jets can be seen.

 

Jorma


  • Tonk and Ron359 like this

#77 Tonk

Tonk

    Cosmos

  • *****
  • Posts: 9,745
  • Joined: 19 Aug 2004
  • Loc: Leeds, UK, 54N

Posted 25 January 2019 - 09:41 AM

Nice results Jorma!

I have just in the last week got my first clear skies since getting my Semrock filter set (C2, CO+ and CN) at the end of 2018. I was only able to test autofocus in SGPro with each filter and obtain a set of 2 x 10 minute test exposures with each filter of 46P imaging at F5.5 with a 130mm APO. The C2 and CN signals were strong at10 minutes in 46P but CO+ was effectively absent - just a little reflected light around the pseudo nucleus @427nm. I'm very pleased with these tests so far.

Next month the gear is being moved to southern Spain. The average of just a couple of nights clear skies in 3/4 months in UK winter has driven me south lol


  • JoRy likes this

#78 freestar8n

freestar8n

    Vendor - MetaGuide

  • *****
  • Vendors
  • topic starter
  • Posts: 11,896
  • Joined: 12 Oct 2007
  • Loc: Melbourne, Australia

Posted 25 January 2019 - 05:37 PM

Hi everyone!

 

I hadn't realized this thread had been re-opened.  It's great to see all the progress in trying to image in the CN band.  That takes things way beyond the basic idea that CN isn't green.

 

I recently revisited CN imaging with Wirtanen because I was hoping to capture rotation or a spiral pattern in the CN band - but the signal appears to be extremely faint using the filter that I started using years ago for that purpose.

 

The thread and image is here:

 

https://www.cloudyni...tation-evident/

 

I really thought that some amateur would be able to capture rotation or spiral structure - but I guess it didn't happen.  I haven't seen any details on how the rotation image had been captured - but it appears to be very wide field.

 

My earlier CN images were with a 300mm f/4 Canon lens - but my current attempt was at f/7 with EdgeHD11.  The guiding was very good, using OAG combined with MetaGuide shift-guiding - but alas there just wasn't much signal.

 

I'd be interested to hear what other options there are nowadays for CN imaging.

 

Thanks for all the contributions and activity in this thread!

 

Frank


  • Tonk and JoRy like this

#79 Ron359

Ron359

    Surveyor 1

  • *****
  • Posts: 1,881
  • Joined: 21 Apr 2008

Posted 25 January 2019 - 06:28 PM

Hi everyone!

 

I hadn't realized this thread had been re-opened.  It's great to see all the progress in trying to image in the CN band.  That takes things way beyond the basic idea that CN isn't green.

 

I recently revisited CN imaging with Wirtanen because I was hoping to capture rotation or a spiral pattern in the CN band - but the signal appears to be extremely faint using the filter that I started using years ago for that purpose.

 

The thread and image is here:

 

https://www.cloudyni...tation-evident/

 

I really thought that some amateur would be able to capture rotation or spiral structure - but I guess it didn't happen.  I haven't seen any details on how the rotation image had been captured - but it appears to be very wide field.

 

My earlier CN images were with a 300mm f/4 Canon lens - but my current attempt was at f/7 with EdgeHD11.  The guiding was very good, using OAG combined with MetaGuide shift-guiding - but alas there just wasn't much signal.

 

I'd be interested to hear what other options there are nowadays for CN imaging.

 

Thanks for all the contributions and activity in this thread!

 

Frank

Aren't you losing significant CN signal to the glass corrector plate + reducer and correctors in the HD and in the telephoto lens elements?


Edited by Ron359, 25 January 2019 - 10:04 PM.


#80 freestar8n

freestar8n

    Vendor - MetaGuide

  • *****
  • Vendors
  • topic starter
  • Posts: 11,896
  • Joined: 12 Oct 2007
  • Loc: Melbourne, Australia

Posted 26 January 2019 - 02:00 AM

Aren't you losing significant CN signal to the glass corrector plate + reducer and correctors in the HD and in the telephoto lens elements?

Hi-

 

Yes there are significant losses throughout - but it just means longer exposure time.  And since I am guiding on the comet motion the exposure time matters less.

 

Celestron has plots of system transmission that still show decent response a bit below 400nm - and the camera QE also is reduced but still has response.

 

A key indication of signal is that I can still image faint stars with short-ish exposures.  As long as the filter isn't leaking in the IR or something - it means I am recording actual photons in the CN band that the filter passes.

 

In this case I was going for high res. to capture any detail that might be rotating - and at that scale I just don't think there was much CN signal to get.  But yes - different optics and different sensor would probably do better.

 

Frank


  • Ron359 and JoRy like this

#81 Ron359

Ron359

    Surveyor 1

  • *****
  • Posts: 1,881
  • Joined: 21 Apr 2008

Posted 26 January 2019 - 02:13 PM

Hi-

 

Yes there are significant losses throughout - but it just means longer exposure time.  And since I am guiding on the comet motion the exposure time matters less.

 

Celestron has plots of system transmission that still show decent response a bit below 400nm - and the camera QE also is reduced but still has response.

 

A key indication of signal is that I can still image faint stars with short-ish exposures.  As long as the filter isn't leaking in the IR or something - it means I am recording actual photons in the CN band that the filter passes.

 

In this case I was going for high res. to capture any detail that might be rotating - and at that scale I just don't think there was much CN signal to get.  But yes - different optics and different sensor would probably do better.

 

Frank

Thanks,  I was just wondering why your results seem so diff from Jorma's in showing rotation and jets of CN.   Would seem to be the Semrock filter is just that much better for the CN band, as it should be t I guess.    



#82 freestar8n

freestar8n

    Vendor - MetaGuide

  • *****
  • Vendors
  • topic starter
  • Posts: 11,896
  • Joined: 12 Oct 2007
  • Loc: Melbourne, Australia

Posted 27 January 2019 - 05:42 PM

Thanks,  I was just wondering why your results seem so diff from Jorma's in showing rotation and jets of CN.   Would seem to be the Semrock filter is just that much better for the CN band, as it should be t I guess.    

I'm not sure how big a factor it is.  The Edmund filter claims > 40% transmission, and it is centered at 390nm, which is near the 388 of CN.  So the big factor may be my small pixels and f/7 vs. his larger ccd pixels and f/2.9.  

 

I'm not sure if his setup includes a coma corrector - but if so then his Newtonian plus coma corrector has 2 mirrors and several lenses - which isn't too different from an EdgeHD setup with reducer.  But I would have several more lenses involved.

 

In terms of signal in each pixel, if I am f/7 vs. f/2.9, and my pixels are 3.8um vs perhaps 6um for his - that is a factor of about 14x higher signal for his setup.  But mine would have benefited from higher res and detail - if in fact the rotation was mainly happening in the very center of the coma - which apparently it is not.

 

Frank



#83 Tonk

Tonk

    Cosmos

  • *****
  • Posts: 9,745
  • Joined: 19 Aug 2004
  • Loc: Leeds, UK, 54N

Posted 07 October 2019 - 04:16 PM

My stuff was set up in Spain in February - then there was a long period of nothing but exceedingly dim comets until C/2018 W2 (Africano)

Here is my first remote controlled test images using my Semrock filters showing the C2 (513/10nm) and CN (387/11nm) coma and the overall luminance signal taken 27/09/2019.

ux54ZEUOaMpZ_1824x0_wmhqkGbg.jpg

 


Edited by Tonk, 07 October 2019 - 04:18 PM.

  • Dave Mitsky, Special Ed, freestar8n and 2 others like this

#84 freestar8n

freestar8n

    Vendor - MetaGuide

  • *****
  • Vendors
  • topic starter
  • Posts: 11,896
  • Joined: 12 Oct 2007
  • Loc: Melbourne, Australia

Posted 08 October 2019 - 03:57 AM

Very nice.  Good to see more regular views in this important band.

 

Frank



#85 Tonk

Tonk

    Cosmos

  • *****
  • Posts: 9,745
  • Joined: 19 Aug 2004
  • Loc: Leeds, UK, 54N

Posted 14 October 2019 - 04:38 AM

Whoever wrote this page "Astromolecule of the Month" back in June 2008 was on the ball. They must be a chemist first and an astronomer second in their role as an astro-chemist. We correctly get CN named as the cyano radical (and *not* cyanogen). Top marks smile.gif

http://www.astrochym...amotm_0806.html

 

 

 

(For completeness the dicarbon species that gives rise to the green Swan emission bands in a comet coma was astromolecule of the month in May 2013.

http://www.astrochym...amotm_1305.html )


Edited by Tonk, 14 October 2019 - 04:49 AM.


#86 Ron359

Ron359

    Surveyor 1

  • *****
  • Posts: 1,881
  • Joined: 21 Apr 2008

Posted 14 October 2019 - 09:00 PM

My stuff was set up in Spain in February - then there was a long period of nothing but exceedingly dim comets until C/2018 W2 (Africano)

Here is my first remote controlled test images using my Semrock filters showing the C2 (513/10nm) and CN (387/11nm) coma and the overall luminance signal taken 27/09/2019.

ux54ZEUOaMpZ_1824x0_wmhqkGbg.jpg

 

Nice to see your images with Semrock filters.  I wondered if you'd gotten your remote scope up and going with them.   What scope and camera did you use?  



#87 Tonk

Tonk

    Cosmos

  • *****
  • Posts: 9,745
  • Joined: 19 Aug 2004
  • Loc: Leeds, UK, 54N

Posted 15 October 2019 - 09:17 AM

What scope and camera did you use?


QSI 863 on a Tak TOA130. QE for the 513nm filter is 60% and for the 387nm is 40%

Its the bottom scope in this rig

n2lIvyLho8h6_620x0_wmhqkGbg.jpg

 


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics