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Equipment Discussions >> Electronically Assisted Astronomy

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GlennLeDrew
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: nytecam]
      #5780200 - 04/05/13 05:23 PM

Maurice,
My comments on Wall's Hypo design were based on both the data and images supplied by Jon himself. He clarified that the aberrations limited it to a lowest power visual instrument.

Why make up a long refractor whose light collector is an f/40 singlet, followed by binocular objective acting as a focal reducer, delivering only an f/3 image plagued by wicked lateral color and still-significant longitudinal color?

FAR better optically, readily available, and much more compact; a cheap f/4 Newt with a $30 0.5-0.7X reducer. Or an inexpensive f/5 achromat with the same reducer at 0.5X.


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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: GlennLeDrew]
      #5799883 - 04/15/13 04:53 AM

Quote:

Chris,
If embellishment, adornment or even fakery is intended, then it's a *lot* simpler to substitute an image taken with even a rather different rig but which has the image scale of the intended 'simulated' view...

Matt,
If you wish not to have such speculation continue, then at least let us know if you're indeed developing (or helping to develop) something which eventually will be available commercially. To drop a 'teaser' and then clam up with the "not for the public domain" brush-off is not consistent with a 'Skunk Works' project for which you have not oversight or signing authority. And so it stands to reason that you're the one answerable, and can only do yourself a favor by providing even a smidgen of supportable clarification.

And what about the state of the camera you also 'teased' us with a little while back? Is it to be considered in the same category?




Any of the group experts or anyone from this group for that matter, if you happen to be in or travel to south east Florida, I'd be happy to meet and demonstrate one evening the reducer and camera.
Otherwise I'll let you know when production starts and more info will then be available .


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GlennLeDrew
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: mattflastro]
      #5801073 - 04/15/13 05:32 PM

If you're willing to demo in person, then why not a *little* detail here, sufficient to allay doubts yet not compromise any proprietary aspects?

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Lorence
scholastic sledgehammer


Reged: 09/15/08

Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: mattflastro]
      #5802855 - 04/16/13 02:25 PM

Quote:

Any of the group experts or anyone from this group for that matter, if you happen to be in or travel to south east Florida, I'd be happy to meet and demonstrate one evening the reducer and camera. Otherwise I'll let you know when production starts and more info will then be available .




As I'm not expert enough to speculate about equipment, I'll just buy it. You win some and you loose some but at least you end up knowing. That beats the alternative and I don't have to spend all day on the forums.

I would like to preorder one of your cameras and focal reducers. I used the term "like" simply because you haven't quite achieved Rock's reputation in the astro video camera business yet.

I already have a pile of cheap cameras for Lunar and planetary so I'm sure you can understand I am only in the market for high end products.

If your camera is in the Mallincam Xtreme or Universe class my order stands. Otherwise I wish you the best of luck with this camera, hopefully you will be successful enough with it to move on to bigger and better cameras. If it is a low end class camera just keep the price down. It seems that is the main criteria for camera selection by many.


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GlennLeDrew
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: Lorence]
      #5803756 - 04/16/13 11:59 PM

I would be hard pressed to refrain from countering the nay-saying of 'forum experts' (like myself ) if I had found a way to achieve the Holy Grail of taking an f/10 system down to f/1.5 with a back-end focal reducer.

That a hobbyist can cobble up from existing lenses such an astounding optical wonder which seems to be beyond the capability of professional designers to offer (at anything like a non-astronomical price, if achievable) would be cause to rightfully crow to high heaven and bask in the ensuing avalanche of plaudits and laurels.

My feeling is that it might well be the case that the *image scale* reduction is occurring, but virtually certainly not at full system aperture. For example, a 10" SCT might be working at nearer to 6" aperture. This notwithstanding, the lack of apparent vignetting and any notable off-axis aberration, for such aggressive reduction, raises a big red flag.

I wonder if the device is actually an afocal imaging system, which would employ a fast, somewhat short focal length lens on the camera, shooting into an eyepiece...


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ccs_hello
Postmaster
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Reged: 07/03/04

Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: GlennLeDrew]
      #5803813 - 04/17/13 12:58 AM

Indeed, placing a lens "before" the primary focal plane is the preferred way to modify an existing optical system's parameters. E.g., (per definition,) placing a negative lens inside focal plane, it is a Barlow; placing a positive lens inside focal plane, it is a Focal Reducer.

Placing a lens "after" the primary focal plane is afocal method. Placing a positive lens (or even a common magnifier), e.g., using an eyepiece, is an eyepiece projection (similar to Barlow effect.)
On the same token, replacing that positive lens with a negative lens will reduce the image scale.

Do an experiment, place a Barlow lens in between a piece of newspaper and your eye, you'll find the text looks tinier.

Clear Skies!

ccs_hello


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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: ccs_hello]
      #5867978 - 05/17/13 07:30 PM Attachment (25 downloads)

Here are the first 3 prototypes of my focal reducer.
Why 3? Due to lack of enough planning .
I started by making focal reducer #1 to be compatible with my C-mount cam #1.
Then I made focal reducer #2 as a cleaner version ( #1 has a lot of rework and modifications due to experimenting) .
Then I decided to make camera #2 with Peltier cooling and T-mount .
Then I had to redo focal reducer #1 and modify it to work with both the T-mount and the C-mount .
So then I made reducer #3 that works from the beginning with both C and T mounts . I also made it fit any 2" focuser instead of just the MEade 3.25" threads.


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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: mattflastro]
      #5867981 - 05/17/13 07:33 PM Attachment (26 downloads)

Another pic below.
I need to mention that these focal reducers that bring an 8 to 12" F/10 SCT down to F/1.85 are NOT a simple doublet or triplet. They are multielement reducers with an ED glass element and were optimised in Oslo before being tested .
The #3 is close to a final version, except for finishing which is still a rough prototype. Final version will get all the normal treatments, blackened lens edges, hard anodizing etc.


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Atl
professor emeritus
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Reged: 04/13/12

Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: mattflastro]
      #5868513 - 05/18/13 12:05 AM

Very cool.

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nytecam
Postmaster


Reged: 08/20/05

Loc: London UK
Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: Atl]
      #5868704 - 05/18/13 03:02 AM

Looks very interesting - thanks for posting

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GlennLeDrew
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: nytecam]
      #5868737 - 05/18/13 03:56 AM

Are these adaptations of existing camera lenses? The barrels and lens coatings give the appearance of surplus stuff from the '70s or '80s.

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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: GlennLeDrew]
      #5869802 - 05/18/13 05:47 PM

Quote:

Are these adaptations of existing camera lenses? The barrels and lens coatings give the appearance of surplus stuff from the '70s or '80s.



Sorry but barrels are not 70's or 80's surplus.
I thought you wouldn't have trouble recognising the stuff that happened to BE recycled.
For the #1 and #2 , they are simply reworked MEade and Celestron T-mount adapters of current production (the Celestron is the HD T-mount adapter).


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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: GlennLeDrew]
      #5869816 - 05/18/13 05:53 PM

Quote:

Are these adaptations of existing camera lenses? The barrels and lens coatings give the appearance of surplus stuff from the '70s or '80s.



Also, the aged aspect of #1 is due to being banged around in numerous trips between machine shop and field tests . Anodizing and paint weren't that great to begin with , and when you assemble and disassemble then clamp a piece and turn it or mill it then go back and repeat the cycle , after a while it starts looking like war surplus.


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JoseBorrero
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Reged: 09/04/09

Loc: Puerto Rico Island
Re: Focal Reducer for Video SCT SCopes down to F/1.5 *DELETED* new [Re: GlennLeDrew]
      #5882943 - 05/24/13 07:15 PM

Post deleted by JoseBorrero

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budman1961
Pooh-Bah
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Reged: 02/25/11

Loc: Springfield, MO
Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: JoseBorrero]
      #5882973 - 05/24/13 07:29 PM

Per his site Jose....

WARNING! THESE FOCAL REDUCERS ARE DESIGNED STRICTLY FOR THE LNTECH CAMERAS, MODEL LN300 AND FOR OUR COOLED T-MOUNT CAMERAS. THEY WILL NOT WORK WITH ANY OTHER CAMERA WITHOUT MODIFICATION. THESE REDUCERS EMPLOY THE MOST AGGRESSIVE, HIGHEST REDUCTION FACTOR THAT IS POSSIBLE GIVEN THE TELESCOPE CHARACTERISTICS, CCD SIZE AND REDUCER TO SENSOR CORRECT SPACING. IT MAY BE POSSIBLE TO MODIFY THE FOCAL REDUCERS TO WORK WITH OTHER 1/3" CCD CAMERAS. CONTACT US FOR MORE DETAILS. WE WILL NEED TO MEASURE YOUR CAMERA MOUNT-FLANGE TO SENSOR DISTANCE TO ANALYZE IF A SPACER COULD BE MODIFIED TO ACCOMODATE THE REDUCER REQUIREMENTS.


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GlennLeDrew
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: budman1961]
      #5882989 - 05/24/13 07:37 PM

Some questions...

What is the sensor depth requirement?

How many lens elements/groups comprise the reducer?

What is the reducer's focal length?

Does this reducer utilize the full aperture of the entrance pupil?

Considering the assembled length, does this result in the primary mirror having to be moved toward the secondary sufficiently far to result in aperture reduction due to clipping by one or both baffles?

What is the diameter of the small-ish aperture at the rear of the unit?

On the "technology" page of the site--where no more technology than found on the main page is discussed--an image clearly taken with other than a 1/3" camera is used to illustrate field coverage. Will actual images obtained via this reducer onto a 1/3" camera be added?

Furthermore, will comparison images be provided so as to illustrate the speed differential? Such as 60s @ f/10 and 2s @ f/1.8 (other settings remaining the same)?


A photo or two looking down the front end of the scope through the assembled system, when set to infinity focus, and with the CCD illuminated, would be instructive. Or just a view straight into just the reducer while attached to a camera.

Edited by GlennLeDrew (05/25/13 04:25 PM)


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GlennLeDrew
Postmaster
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: GlennLeDrew]
      #5884343 - 05/25/13 04:56 PM

Bumped because of added questions to the above post...

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a__l
professor emeritus


Reged: 11/24/07

Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: mattflastro]
      #5896827 - 06/01/13 09:36 PM

Quote:

Hyperstar is an option that gets down to F/2 .
Meade .33x gets down to F/3.3 .
I am not aware of any other options that could be used , which should not involve disassembling the corrector and buying $1000 worth of mechanical+optical parts .
The image below is shot with my home made reducer and my Meade 10 inch F/10 SCT .
The result is F/1.55 apparently (I might be off by a little, actual range based on transit time is 1.5 to 1.6 ) .
Is there anything like this available commercially ?
Please note that my reducer can NOT work with cameras that have a CCD any larger than 1/3" ( 6mm diagonal).




Interesting info (in Russian) and schedule.
The sensitivity of ICX-413AQ and F/D. web page
At very fast reducer, you will lose in the sensitivity matrix.


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ccs_hello
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Reged: 07/03/04

Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: a__l]
      #5897069 - 06/02/13 12:00 AM

This light cone steepness impact to digital image sensor is well known. Some mfgs' marketing department specifically made that point stating their lenses are resigned as "digital lens" as opposed to film SLR lenses.

The underlying reason is the image sensor's microlens design. Later sensors made a little bit of improvement on sensor's optical path.

The "special designed" digital lens' rear group attempts to realign the light beam to be as perpendicular to the sensor plane as possible. Naturally it's not the case on a telescope OTA with a F.R. "modifier".

My take: since there is nothing we can do to fix the sensor design, why not just keep on shooting. (E.g., at f/1.8, ICX413's microlens' efficiency only drops 18%.

Clear Skies!

ccs_hello


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a__l
professor emeritus


Reged: 11/24/07

Re: Focal Reducer for Video SCT SCopes down to F/1.5 new [Re: ccs_hello]
      #5897084 - 06/02/13 12:13 AM

at f/1.5, ICX413's microlens efficiency drops about 40%

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