Jump to content


Photo

DS vs TS images

  • Please log in to reply
15 replies to this topic

#1 Jesus Munoz

Jesus Munoz

    Ranger 4

  • -----
  • Posts: 365
  • Joined: 09 Mar 2007
  • Loc: Querétaro, México

Posted 14 November 2012 - 10:05 AM

Hi,

Last Sunday I was working with my Lunt 60 scope and I took some images with a PGR Chameleon and a FR working at around 375mm for getting a full solar disk.

This is a comparison of placing one etalon for double-stacking and two etalons for triple-stacking. Obviously the capturing parameters changed drastically because I got less light with the TS setup.

Thanks for your comments

Attached Files



#2 Jesus Munoz

Jesus Munoz

    Ranger 4

  • -----
  • Posts: 365
  • Joined: 09 Mar 2007
  • Loc: Querétaro, México

Posted 14 November 2012 - 10:08 AM

And this image is the triple stack sample.

Thanks for your comments

Attached Files



#3 ValeryD

ValeryD

    Vendor (Aries)

  • *****
  • Vendors
  • Posts: 1134
  • Joined: 26 Nov 2005
  • Loc: Kherson, Ukraine.

Posted 14 November 2012 - 11:22 AM

The difference is quite small and TS for photography has no real advantage. One can record a longer movie and stack more frames - to increase the S/N and then rise the contrast higher and finally the pictures will be almost identical.
Better to invest in larger aperture than in TS.

#4 Andy Devey

Andy Devey

    Mercury-Atlas

  • -----
  • Posts: 2775
  • Joined: 06 May 2011

Posted 15 November 2012 - 05:12 AM

Hi Jesus

I triple stack my SM90 and it really comes into its own at long focal lengths and especially on the limb. I have found that with TS detail can be seen right up to the edge where as with DS the photosphere has leaked through and the chromosphere appears much fainter around the edge.

Mostly TS movies

Regards

Andy

#5 Matt Wastell

Matt Wastell

    Vanguard

  • -----
  • Posts: 2293
  • Joined: 05 Jul 2009
  • Loc: Paddington, Brisbane, Australia

Posted 15 November 2012 - 05:57 AM

Hello Jesus,
Both are great images - these is a bit more pop in the TS.

#6 Jesus Munoz

Jesus Munoz

    Ranger 4

  • -----
  • Posts: 365
  • Joined: 09 Mar 2007
  • Loc: Querétaro, México

Posted 16 November 2012 - 10:10 AM

Thank you Valery, Andy and Matt for your comments. I think there is more contrast in the TS and it deserves the extra effort for using 3 etalons.

Great videos as always Andy! TS and long focal lenght, incredible.

#7 BYoesle

BYoesle

    Aurora

  • *****
  • Posts: 4900
  • Joined: 12 Jun 2004
  • Loc: Goldendale, Washington USA

Posted 17 November 2012 - 12:21 PM

Wonderful images Jesus! :bow:

I have found that with TS detail can be seen right up to the edge where as with DS the photosphere has leaked through and the chromosphere appears much fainter around the edge.


Hi Andy. Do you have any comparison images you could post?

#8 Andy Devey

Andy Devey

    Mercury-Atlas

  • -----
  • Posts: 2775
  • Joined: 06 May 2011

Posted 18 November 2012 - 06:50 AM

Hi Bob

Here are a couple of typical images but they were not taken at the same time - it was one of your comments on an earlier post that got me to experiment on the limb and TS is great for prominences and filament-prominence features

This is a DS limb photo

Attached Files



#9 Andy Devey

Andy Devey

    Mercury-Atlas

  • -----
  • Posts: 2775
  • Joined: 06 May 2011

Posted 18 November 2012 - 06:53 AM

Here is a TS limb photo

Attached Files



#10 Andy Devey

Andy Devey

    Mercury-Atlas

  • -----
  • Posts: 2775
  • Joined: 06 May 2011

Posted 18 November 2012 - 07:21 AM

Hi Jesus

I downloaded your two stunning full disc shots and if you switch from one to the other continuously the difference id detail is massive!

Regards

Andy

#11 mbucky

mbucky

    Gemini

  • -----
  • Posts: 3218
  • Joined: 21 Oct 2007
  • Loc: San Diego

Posted 18 November 2012 - 09:08 AM

nice stuff man, TS seems to deliver some good results by cutting back on stray light

#12 BYoesle

BYoesle

    Aurora

  • *****
  • Posts: 4900
  • Joined: 12 Jun 2004
  • Loc: Goldendale, Washington USA

Posted 19 November 2012 - 11:36 AM

Hi Andy -

This is curious, as I do not see any hint of a “double limb” with photospheric leakage with double stacking my two front mounted SM90's (image below)... rather it looks almost identical to your triple stacking image: The DS view you have above looks more like a typical 0.7 A FWHM image, and the TS looks more like a >0.5 A FWHM image.

You may want to experiment in getting your DS tilts and rotations optimized link (for instance using a auxiliary refractor telescope), and then do the triple stack. The only other issue that might be involved is that if your DS mode uses an internal etalon, where the bandpass (and therefore contrast uniformity) can vary across the field of view/ image due to increased field angles, you may not be getting all the benefits of DSing in all parts of the image plane...

Attached Files



#13 BYoesle

BYoesle

    Aurora

  • *****
  • Posts: 4900
  • Joined: 12 Jun 2004
  • Loc: Goldendale, Washington USA

Posted 19 November 2012 - 11:39 AM

Identical processing: Single stack @ 0.7 A FWHM left, double stack @ >0.5 A FWHM right:

Attached Files



#14 Jesus Munoz

Jesus Munoz

    Ranger 4

  • -----
  • Posts: 365
  • Joined: 09 Mar 2007
  • Loc: Querétaro, México

Posted 19 November 2012 - 11:11 PM

Very interesting points Bob and Andy. Here I present a comparison of TS-DS-SS in the same region of the Sun taken last Sunday. I think the TS shows a little better the solar limb, but marginally. None shows double image :jump:

Regards

Attached Files



#15 BYoesle

BYoesle

    Aurora

  • *****
  • Posts: 4900
  • Joined: 12 Jun 2004
  • Loc: Goldendale, Washington USA

Posted 20 November 2012 - 02:22 AM

Great comparison images Jesus! :bow:

But your image of a single stacked (SS) does indeed show the “double limb” phenomena quite well. I have cropped and enlarged your image, and placed the tip of the arrow on the “inner limb,” which is actually the edge of the photosphere showing through at 0.7 A FWHM. This parasitic light reduces the contrast of the chomospheric details, giving the edge of the chromosphere a fainter-translucent appearance as noted by Andy, and makes getting exposures and processing of the prominences with disk detail more difficult. With double stacking (DS), the FWHM of the filter system is >0.5 A, and photospheric leakage/contamination is eliminated, which significantly improves contrast and prominence detail. Triple stacking (~0.3 A FWHM) appears to have less effect, if at all - at least in these images.

Attached Files



#16 BYoesle

BYoesle

    Aurora

  • *****
  • Posts: 4900
  • Joined: 12 Jun 2004
  • Loc: Goldendale, Washington USA

Posted 20 November 2012 - 02:27 AM

Triple vs Double Stacked (I actually prefer the DS image over the TS - but it may just be the processing):

Attached Files








Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics