Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Video and Electronically Assisted Astronomy

Pages: 1
Dragon Man
Carpal Tunnel
*****

Reged: 03/07/06

Loc: Snake Valley, Australia
HOW TO: make your own Video suitable Focal Reducer new
      #6336043 - 01/26/14 04:54 AM

A nice easy project to have a play with.
It's cheap, so if it doesn't suit your use, then you haven't lost much

I made this Video Tutorial of how to make your own Focal Reducer for a 2" Focuser using a Binocular lens and a 1.25" to 2" EP Adaptor.

For the Video Tutorial CLICK HERE

Note: If you decide to attempt using a 50mm Binocular lens be aware that 50mm Binocs may actually in some cases have 52mm diameter Primary lenses and can't be used.

Attempt to use a max of 48mm Binocs, they should have a 50mm lens. Any Binocs betweem 32mm and 48mm should be fine.
Also Note that I do state 'Astronomical' Binocs, not those brightly coloured Anti-Glare Horse-racing & nature Binocs.


Post Extras: Print Post   Remind Me!   Notify Moderator  
ccs_hello
Postmaster
*****

Reged: 07/03/04

Re: HOW TO: make your own Video suitable Focal Reducer new [Re: Dragon Man]
      #6336451 - 01/26/14 11:28 AM

Ken,

Great video tutorial.
Just a comment, I do not recommend to use superglue inside the optical system because of the fume. (Remember high school lab or TV CSI shows using superglue fume to lift the finger print ) Or let it dry thoroughly.
For mounting lenses, I'd recommend using an adhesive which is more appropriate for optical use.

Clear Skies!

ccs_hello


Post Extras: Print Post   Remind Me!   Notify Moderator  
ccs_hello
Postmaster
*****

Reged: 07/03/04

Re: HOW TO: make your own Video suitable Focal Reducer new [Re: Dragon Man]
      #6336461 - 01/26/14 11:30 AM

Ken,

Also if you don't mind, I'd like to share this old DIY thread with some pictures.

Clear Skies!

ccs_hello


Post Extras: Print Post   Remind Me!   Notify Moderator  
mclewis1
Thread Killer
*****

Reged: 02/25/06

Loc: New Brunswick, Canada
Re: HOW TO: make your own Video suitable Focal Reducer new [Re: ccs_hello]
      #6337429 - 01/26/14 07:24 PM

Ah the old pill bottle mounting setup ... thanks CCS.

Ken, great video. Now I'm looking around at my and my friend's old binoculars in a whole different way.


Post Extras: Print Post   Remind Me!   Notify Moderator  
GlennLeDrew
Postmaster
*****

Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: HOW TO: make your own Video suitable Focal Reducer new [Re: mclewis1]
      #6337456 - 01/26/14 07:44 PM

You'd be surprised to learn how many commercial reducers use what are the very same doublets found in binos. For example, the Lumicon Easy Guider and Giant Easy Guider used 50mm and 80mm bino objectives, respectively. Just to name two specific, relatively 'high end' units. The ubiquitous 1.25", so-called 0.5X reducers use 25mm f/4 bino objectives.

Post Extras: Print Post   Remind Me!   Notify Moderator  
tadpoletoo
super member
*****

Reged: 04/18/11

Loc: NW Michigan
Re: HOW TO: make your own Video suitable Focal Reducer new [Re: GlennLeDrew]
      #6342714 - 01/29/14 10:06 AM

Thanks guys! this is the kind of stuff that keeps me coming back. Dave

Post Extras: Print Post   Remind Me!   Notify Moderator  
JimT
sage
*****

Reged: 08/13/05

Loc: Milky Way Galaxy
Re: HOW TO: make your own Video suitable Focal Reducer new [Re: tadpoletoo]
      #6344610 - 01/30/14 07:24 AM

Ken

Nice work.





Edited by JimT (01/30/14 07:25 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
ccs_hello
Postmaster
*****

Reged: 07/03/04

Re: HOW TO: make your own Video suitable Focal Reducer [Re: ccs_hello]
      #6346094 - 01/30/14 09:42 PM

Just like to add an important information:

High focal reduction has a steep light cone. To fully illuminate an image sensor, you'd like the objective lens (e.g., donated from a 7x35 bino) as large as possible.
You might find I try to use a larger lens (to avoid optical vignetting), then the medicine bottle (in the shape of reducing profile gradually) to avoid physical vignetting.

Clear Skies!

ccs_hello


Post Extras: Print Post   Remind Me!   Notify Moderator  
rmollise
Postmaster
*****

Reged: 07/06/07

Re: HOW TO: make your own Video suitable Focal Reducer new [Re: ccs_hello]
      #6346616 - 01/31/14 07:38 AM

Quote:

Just like to add an important information:

High focal reduction has a steep light cone. To fully illuminate an image sensor, you'd like the objective lens (e.g., donated from a 7x35 bino) as large as possible.
You might find I try to use a larger lens (to avoid optical vignetting), then the medicine bottle (in the shape of reducing profile gradually) to avoid physical vignetting.

Clear Skies!

ccs_hello




True, but you would need a huge amount of vignetting before a 1/3-inch or 1/2-inch video chip is affected.


Post Extras: Print Post   Remind Me!   Notify Moderator  
ccs_hello
Postmaster
*****

Reged: 07/03/04

Re: HOW TO: make your own Video suitable Focal Reducer new [Re: rmollise]
      #6346699 - 01/31/14 08:44 AM Attachment (11 downloads)

Unk Rod,

Using a smaller focal reducer
with just 23.5mm lens diameter and a type-1/2" CCD, at 0.34x focal reducing ratio, the image sensor is just 10% fully illuminated <-- by on-axis light (cell B29.)

Clear Skies!

ccs_hello


Post Extras: Print Post   Remind Me!   Notify Moderator  
StarStuff1
Post Laureate
*****

Reged: 04/01/07

Loc: South of the Mason-Dixon Line
Re: HOW TO: make your own Video suitable Focal Reducer new [Re: ccs_hello]
      #6347458 - 01/31/14 03:42 PM

Good video, very Informative.

Years ago I bought a grab bag of small lenses from JerryC0 (American Science and Surplus). Using a couple of the achromats and some color filter housings I made both a .6 and a .5 focal reducers. Worked pretty well and I am still using them.


Post Extras: Print Post   Remind Me!   Notify Moderator  
GlennLeDrew
Postmaster
*****

Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: HOW TO: make your own Video suitable Focal Reducer new [Re: StarStuff1]
      #6347511 - 01/31/14 04:09 PM

The more aggressive the desired reduction, the faster must be the reducer. No matter how large the lens. For our little video chips, a 50mm f/4 bino objective is really no better than a 25mm f/4.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Dom543
member
*****

Reged: 10/24/11

Re: HOW TO: make your own Video suitable Focal Reducer new [Re: GlennLeDrew]
      #6347624 - 01/31/14 05:05 PM

css_hello,
Is your spreadsheet publicly available? I mean the worksheet with the formulas, not just the screen shot.

Glenn,
Why is that? Can't I make reduction more aggressive by increasing the distance between the reducer and the sensor?

Thank you,
--Dom


Post Extras: Print Post   Remind Me!   Notify Moderator  
ccs_hello
Postmaster
*****

Reged: 07/03/04

Re: HOW TO: make your own Video suitable Focal Reducer new [Re: Dom543]
      #6347836 - 01/31/14 06:41 PM

Dom,

The spreadsheet came from one of the Y! group and is not mine. I've asked the author in the past and I did not get approval. (I've also asked him to join CN.) May be in the next long holiday I'll re-write it. It is not difficult at all. The on-axis beam coverage is the special one but is not really difficult (get the new image circle size then divide by the sensor's image area.)

Clear Skies!

ccs_hello


Post Extras: Print Post   Remind Me!   Notify Moderator  
GlennLeDrew
Postmaster
*****

Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: HOW TO: make your own Video suitable Focal Reducer new [Re: Dom543]
      #6348293 - 01/31/14 11:46 PM

Quote:

css_hello,
Is your spreadsheet publicly available? I mean the worksheet with the formulas, not just the screen shot.

Glenn,
Why is that? Can't I make reduction more aggressive by increasing the distance between the reducer and the sensor?

Thank you,
--Dom




The increase in separation must be supported by the available reducer lens aperture. When moving the camera farther back, you are effectively pushing the reducer farther up into the light cone, where the beam is wider. The more reduction you demand, the faster must be the reducer if vignetting--or worse yet, aperture reduction--is to be avoided.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1


Extra information
6 registered and 5 anonymous users are browsing this forum.

Moderator:  csa/montana, JayinUT 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 720

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics