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

Focus on the Sun

  • Please log in to reply
5 replies to this topic

#1 coralaholic

coralaholic

    Vostok 1

  • -----
  • topic starter
  • Posts: 174
  • Joined: 05 May 2019

Posted 05 July 2020 - 01:23 AM

How to accurately focus on the Sun through a baader solar filter?  

If I can focus it properly and follow with the normal lucky imaging/ processing, is it possible to retrieve some details of the structure of the solar disk or just a complete white disk should be expected? 

The focal length of the scope is 450mm.

 

Clear skies.


Edited by coralaholic, 05 July 2020 - 01:30 AM.


#2 Tom Glenn

Tom Glenn

    Mercury-Atlas

  • -----
  • Posts: 2,953
  • Joined: 07 Feb 2018
  • Loc: San Diego, CA

Posted 05 July 2020 - 01:46 AM

There is a separate forum for solar imaging specifically, so you may find more help there (it's tricky to find because it's listed under "observing forums"....go figure).  But in general, the easiest way to focus on the Sun with a standard filter is to use sunspots.  Unfortunately, those are at a minimum these days.  If no spots are present, you can use the limb, and try and get it as sharp as possible.  Some details can be imaged in white light, although at 450mm it will mostly be a featureless disk with a hint of texture if there are no sunspots.  This is why most serious solar folks image in H-alpha, because it is much more interesting.  



#3 sg6

sg6

    Cosmos

  • *****
  • Posts: 9,264
  • Joined: 14 Feb 2010
  • Loc: Norfolk, UK.

Posted 05 July 2020 - 03:21 AM

Either difficult or impossible.

The sun is a big ball of gas, well plasma, easier to think of gas.

The edges are soft so no well defined edge to focus on. The Baader is white light so no surface detail to focus on.

So you cannt use the edge and you cannot use the central surface.

 

Could wait for a convenient sunspot and if big enough use that. Otherwise it is as good as you can manage.



#4 Tom Glenn

Tom Glenn

    Mercury-Atlas

  • -----
  • Posts: 2,953
  • Joined: 07 Feb 2018
  • Loc: San Diego, CA

Posted 05 July 2020 - 03:39 AM

Either difficult or impossible.

The sun is a big ball of gas, well plasma, easier to think of gas.

The edges are soft so no well defined edge to focus on. The Baader is white light so no surface detail to focus on.

So you cannt use the edge and you cannot use the central surface.

 

Could wait for a convenient sunspot and if big enough use that. Otherwise it is as good as you can manage.

I disagree with your statements.  I've used the limb of the Sun on several occasions to focus in the complete absence of sunspots, in order to image ISS transits.  See below.  

 

https://flic.kr/p/25YXevC

https://flic.kr/p/H9KKzk



#5 freddie

freddie

    Vostok 1

  • -----
  • Posts: 139
  • Joined: 26 Oct 2010

Posted 05 July 2020 - 04:47 AM

Either difficult or impossible.

The sun is a big ball of gas, well plasma, easier to think of gas.

The edges are soft so no well defined edge to focus on. The Baader is white light so no surface detail to focus on.

So you cannt use the edge and you cannot use the central surface.

 

Could wait for a convenient sunspot and if big enough use that. Otherwise it is as good as you can manage.

I too disagree with a lot you say. Have you done any WL solar imaging?

It is not the case that because it is WL there are no surface details, you can see/image granulation which can be used to focus. 



#6 Great Attractor

Great Attractor

    Vendor - ImPPG Imaging Software

  • -----
  • Vendors
  • Posts: 354
  • Joined: 23 Oct 2012
  • Loc: Poland/Germany

Posted 05 July 2020 - 05:30 AM

Either difficult or impossible.
The sun is a big ball of gas, well plasma, easier to think of gas.
The edges are soft so no well defined edge to focus on.

Actually the photosphere (which is partially transparent to visible light) is only a few hundred kilometers thick — compared to the 1.4 million km diameter of the Sun, this gives a perfectly defined, sharp edge at typical image scales used by amateurs.
 

The Baader is white light so no surface detail to focus on.
So you cannt use the edge and you cannot use the central surface.

One can use the granulation, which is always present (except at unusably bad seeing conditions). A 50 mm refractor + mono camera is enough to image it.


Edited by Great Attractor, 05 July 2020 - 05:31 AM.



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