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

Binoculars and filters

  • Please log in to reply
8 replies to this topic

#1 j_863

j_863

    Lift Off

  • -----
  • topic starter
  • Posts: 3
  • Joined: 07 Aug 2020

Posted 17 October 2020 - 11:37 AM

A couple nights ago was the clearest nights in Florida in what it seems like weeks. I was trying out my oberwerk 25x100's. I was going to see how many messier objects I could view in 1 session. The dew started setting in about 45 minutes in. So my session was cut short. I am going to try some foam aheets as dew sheilds. Hoping that the dew shields will allow at least a 2 hour session next time.
Back on the topic. Before packing up to drive 35 minutes home I took one last look at Jupiter with completely fogged up lenses. I could barely see the 4 moons. But I noticed something I've never seen aa well. The gas bands. It seemed like with fogged up lenses the gas bands were easier to see. It made me think about filters.
1. Are the oberwerk 25x100's filter compatible?
2. If so, what type of filters should I look into?
3. Were my eyes just playing tricks on me or was the "filtered" light making it easier to see the bands?
  • j.gardavsky likes this

#2 j.gardavsky

j.gardavsky

    Surveyor 1

  • *****
  • Posts: 1,933
  • Joined: 18 Sep 2019
  • Loc: Germany

Posted 17 October 2020 - 12:11 PM

1. Dew shields for the binoculars

My binoculars have dew and stray light shields cut from foam to slow down the heat exchange to prevent the fogging, and to protect the optics from the stray light,

 

https://www.cloudyni...for-binoculars/

 

2. Filters on the binculars

Either the binoculars have filter threads on the eye lenses of their eyepieces, or I fasten the 1.25" filters into the eye guards,

 

https://www.cloudyni...-on-binoculars/

 

Hoping this helps,

JG


  • Pinac likes this

#3 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 88,192
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 17 October 2020 - 01:40 PM

Just a comment:

 

Nebula filters are interference filters. This means the band pass is dependent on the angle of the light passing through the filter. Since the light from the outer field of view is passing through the filter at an angle of half the field angle, filters placed over the eyepiece are effective in the center of the field but are decreasingly effective moving away from the center.

 

Jon


  • Pinac likes this

#4 C.Hay

C.Hay

    Vostok 1

  • -----
  • Posts: 184
  • Joined: 07 Jan 2015
  • Loc: Germany

Posted 18 October 2020 - 06:32 AM

My practical experience with filters placed on the eyepieces of binoculars contradicts the often-read proposition that it doesn't work well. I have had some very pleasing observations this way, even with narrowband H-Beta and OIII filters. Sure, putting the filters over the objectives is probably better, but as soon as objective diameter moves beyond 45mm (which is the max. clear diameter of 2-inch filters), we just don't have the option. I'm sure Jiri will agree.

 

The OP asked about the proper types of filters. For Jupiter and now Mars, I'd recommend Baader Neodymium. Baader Contrast Booster may also be worth a try, particularly for an achromat like that used by the OP.

 

On Mars and particularly on Venus I've had very good results with linear polarization filters.

 

A special game of mine is to try and see the phase of Venus with 15x45 binoculars: for this task, high-quality yellow filters (placed over the objectives, in this case) have yielded remarkable results. A couple of weeks ago I estimated the phase of Venus at 60% - without prior knowledge, as I hadn't visited that planet for quite a while. This may scarcely seem plausible, given that the planet's disc was only 17" in diameter. But properly selected filters can do great things to enhance contrast and allow observations that would otherwise be impossible.

 

CS, Christopher


Edited by C.Hay, 18 October 2020 - 06:33 AM.

  • Pinac, Enkidu and j.gardavsky like this

#5 C.Hay

C.Hay

    Vostok 1

  • -----
  • Posts: 184
  • Joined: 07 Jan 2015
  • Loc: Germany

Posted 18 October 2020 - 11:50 AM

And an answer to the OP's question 3: Yes, definitely! Your binoculars have an exit pupil of 4mm, which is a bit too much for Jupiter. The glare obliterates the bands. I've been able to see the bands quite well with a 20x50, but it gets hard with a non-apochromatic 20x100.

 

Sometimes a bit of fog or thin cloud helps in the same way to reduce image brightness to the ideal level for the brightest planets. So if you can find a way to handle your dew problem, while attaching e.g. linear polarization filters to the eyepieces, you can control the results without waiting for a bank of fog smile.gif

 

CS, Christopher


Edited by C.Hay, 18 October 2020 - 11:52 AM.

  • j.gardavsky likes this

#6 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 88,192
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 18 October 2020 - 03:51 PM

Well..

 

Narrowband, nebula filters make sense for fixed magnification binoculars.  The exit pupils are large, magnications are low. 

 

Viewing the planet's, magnifications should be high, exit pupils should be small..  its an exercise in futility with fixed magnification binos.. 

 

Jon



#7 KennyJ

KennyJ

    The British Flash

  • *****
  • Posts: 37,798
  • Joined: 27 Apr 2003
  • Loc: Lancashire UK

Posted 18 October 2020 - 04:05 PM

I find it surprising how often the simple option of temporarily fitting aperture masks is overlooked.



#8 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 88,192
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 19 October 2020 - 01:16 AM

I find it surprising how often the simple option of temporarily fitting aperture masks is overlooked.

 

I mess around with aperture masks.  But for the planets and the moon, if one has any sort of a telescope, it's more capable. The best way to reduce the exit pupil is to increase the magnification.

 

Jon



#9 KennyJ

KennyJ

    The British Flash

  • *****
  • Posts: 37,798
  • Joined: 27 Apr 2003
  • Loc: Lancashire UK

Posted 19 October 2020 - 12:44 PM

Oops -- Sorry, Jon,

 

I thought this thread was supposed to be about filters and Binoculars ( particularly those with fixed magnification )

 

Kenny




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