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

Images showing impact of bandshift with a 3nm filter

  • Please log in to reply
3 replies to this topic

#1 Gavster

Gavster

    Apollo

  • *****
  • topic starter
  • Posts: 1,238
  • Joined: 07 Mar 2014

Posted 09 January 2022 - 03:50 PM

In my observing session last night I took a few phone images of the area around Orion and Barnard’s Loop with my pvs-14 at 1x with my chroma 3nm ha filter. I thought it may be of interest to see just how significant the bandshift impact is with a 3nm filter at f1.2 - a lot!! But the contrast on the nebulae in the middle is amazing so that’s why I prefer to use a very narrowband filter despite the bandshift.

I also tried my chroma 5nm ha yesterday, but personally I preferred the 3nm views. All images shown are with the 3nm ha filter.

 

Attached Thumbnails

  • 846BD438-9B99-49BD-AB87-05A494193E30.jpeg
  • CAB260DA-2FFF-4887-AAFA-10DE3CC72F69.jpeg

Edited by Gavster, 09 January 2022 - 04:18 PM.

  • Jim4321, bobo99, Ray Cash and 1 other like this

#2 Gavster

Gavster

    Apollo

  • *****
  • topic starter
  • Posts: 1,238
  • Joined: 07 Mar 2014

Posted 09 January 2022 - 03:51 PM

Some more comparison images…

 

Attached Thumbnails

  • C4474746-22C7-4685-82EE-D49EFF58D4AC.jpeg
  • EF79647E-B7E7-4ECE-94F6-3AF0C44CE770.jpeg

  • Jim4321, bobo99, Ray Cash and 1 other like this

#3 chemisted

chemisted

    Viking 1

  • -----
  • Posts: 756
  • Joined: 24 Feb 2012

Posted 09 January 2022 - 04:06 PM

When Dennis di Cicco reviewed the TNVC-TeleVue PVS-14 in the June 2018 issue of Sky & Telescope (pages 58-61) he used a 3nm filter to provide an image that is identical to the top image in your first post.  He also had a similar shot of the Cygnus region to show the same effect.  Unfortunately, he did not show any other wide field nebula shots at higher image scale that is more representative of what those on this forum routinely see and I have always felt this was a major failure of the review. 


Edited by chemisted, 09 January 2022 - 04:08 PM.


#4 Mort H

Mort H

    Vostok 1

  • *****
  • Posts: 179
  • Joined: 04 Nov 2006
  • Loc: Grand Rapids, Michigan

Posted 09 January 2022 - 07:42 PM

I think you can reverse the situation and use an f/2 3.5nm or f/2 3nm filter and watch the nebula disappear at the center of the FOV instead of disappearing at the edge!  I had some fun with that...not at 1x but with my f/2 3.5nm filter located between the afocal EP and the NV device, which from the filter's point of view is geometrically the same thing as 1x (light from a point at the edge of the FOV is made from parallel rays hitting the filter at a 20 degree angle).

 

Your 3nm images are great, you put your subject in the center part of the FOV anyway, turns out great.  Nebulae are super bright (high contrast) in your finished images, thanks to the narrow 3nm passband!


Edited by Mort H, 10 January 2022 - 11:12 AM.

  • Gavster likes this


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