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Focal Reducers for vid cameras

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#1 RightWill

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Posted 17 August 2014 - 10:03 PM

Hi all,

 

 I'm doing my research for purchasing a video camera for a C9.25 or C8 scope. I'm in between a Mallincam Jr. Pro and the AVS APU-1. I'm leaning towards the Mallincam just for the reputation. However I'm confused at the focal reducer I will need to purchase to be able to achieve a good FOV for video images. I couldn't understand the Mallincam website on the accessories tab. Can anyone who owns the Jr. Pro give me an idea the focal reducers available and the cost. Thanks. The APU-1 can use a variable modular reducer that seems real nice but it only fits either a 1/3 or 1/4 chip, and I believe the Jr Pro is a 1/2. Thanks



#2 GlennLeDrew

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Posted 17 August 2014 - 10:47 PM

What degree of reduction do you desire? For maximal reduction with SCTs, perhaps the best choice  is the Meade f/3.3 (0.33X) reducer, as it corrects both coma and field curvature, and introduces minimal  vignetting. I gather the Japanese version is better than the later Chinese unit. Or the Optec 0.33X reducer could be a viable option. The Mallincam MFR-5 is a two-lens reducer which is 'natively' 0.5X, but with spacers can be configured to get down to around 0.3X.


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#3 CA Curtis 17

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Posted 17 August 2014 - 10:49 PM

Rick,

 

I have owned a MC Xtreme for 4 years and use it regularly with my C9.25.  If you get the Mallincam, get the MFR5-II focal reducer along with a 5mm spacer to stick between the two halves of the reducer.  It is expensive (OA-10 MFR-5 II focal reducer, 0.33x $249.95 USD) but gives me a focal ratio of approximately f/4.5 which is great for most DSOs.  The Celestron f/6.3 focal reducer is nice and much less expensive, but there is a big difference in image scale and length of exposure required with the shorter focal length of the MFR5-II.  Please note, you will need some additional spacers with the C9.25 (likely the 8 as well) to achieve focus.  The Televue SCT2" adaptor (itemTE-ACC-0003 from OPT) along with the Televue 2" to 1.25" High Hat Adapter (item TE-ACR-2125 from OPT).  You don't have to buy the Televue, you can get any adapter which gives you the same spacing.  This replaces your SCT Visual Back.   Same applies to MC Jr Pro as for the Xtreme.

 

Now I haven't yet tried Matt's cameras (Astro-Video Systems) so I cannot comment on those from personal experience, but people who have them seem to be happy.  He does have an f/1.8 focal reducer which I will soon get to try with my 9.25" and 14" SCTs.

 

Hope this helped.  Good luck.

 

Best Regards,

Curtis


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#4 RightWill

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Posted 17 August 2014 - 10:51 PM

Glenn, I have no idea at what focal ratio I will need for a new video setup. I want to do DSO video mainly but would also like to be able to display planetary images also. The MFR5 sounds like the answer. I saw it on the Mallincam website but could make out if it fit SCTs. Thanks for the help.



#5 RightWill

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Posted 17 August 2014 - 10:56 PM

Rick,

 

I have owned a MC Xtreme for 4 years and use it regularly with my C9.25.  If you get the Mallincam, get the MFR5-II focal reducer along with a 5mm spacer to stick between the two halves of the reducer.  It is expensive (OA-10 MFR-5 II focal reducer, 0.33x $249.95 USD) but gives me a focal ratio of approximately f/4.5 which is great for most DSOs.  The Celestron f/6.3 focal reducer is nice and much less expensive, but there is a big difference in image scale and length of exposure required with the shorter focal length of the MFR5-II.  Please note, you will need some additional spacers with the C9.25 (likely the 8 as well) to achieve focus.  The Televue SCT2" adaptor (itemTE-ACC-0003 from OPT) along with the Televue 2" to 1.25" High Hat Adapter (item TE-ACR-2125 from OPT).  You don't have to buy the Televue, you can get any adapter which gives you the same spacing.  This replaces your SCT Visual Back.   Same applies to MC Jr Pro as for the Xtreme.

 

Now I haven't yet tried Matt's cameras (Astro-Video Systems) so I cannot comment on those from personal experience, but people who have them seem to be happy.  He does have an f/1.8 focal reducer which I will soon get to try with my 9.25" and 14" SCTs.

 

Hope this helped.  Good luck.

 

Best Regards,

Curtis

 

Thanks Curtis,

 

 understand I need a reducer but I will also need additional spacers to be able to get a good display? Sounds like I need to take into consideration additional cost when buying a video camera.



#6 Dom543

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Posted 17 August 2014 - 11:04 PM

RightWill,

 

One of the advantages of the small sensor cameras used in camera assisted observations is that they take a high amount of focal reduction. Most people operate in the f3-f4 range. Focal reducers are simple optics, they are not camera specific. You can use a Meade reducer with a Mallincam or a Mallincam reducer with an AVS camera without any negative side effect.

 

There are three focal reducers that can help you to reach the dream land of f3-f4.

- Meade 3,3 FR  for about $ 100  (no longer made but available second hand on Amart or CN).

- Mallincam MFR-5 for $200-250 (check the Mallincam site for the exact price and make sure that you also buy at least two additional spacers).

- AVS VarioReducer for $100.

 

Regarding cameras, there are two important differences between the Mallincam Jr Pro and the AVS APU-1.

1. The APU-1 is Peltier cooled, the Mallincam Jr Pro is not. The camera in the  Mallincam lineup that is Peltier cooled and hence more closely comparable to the APU-1 is the Xtreme.

2. The Mallincam Jr Pro is available for immediate delivery now. The APU-1 has a projected release date of August 31.

 

Clear Skies!

--Dom


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#7 RightWill

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Posted 17 August 2014 - 11:46 PM

Thanks Dom,

 

 I have done a little more research and have come to find the variable reducer made by AVS will not fit or cannot be used with a 1/2 sensor. So that would count out the Jr Pro with this reducer.

 

 Looks like I am between the Jr Pro with the MFR-5 and the APU-1 and the variable reducer. The AVS is cheaper and more versatile on focal range and it has the cooler but only a 1/3 sensor. If I can find the Meade reducer that would be ok for both cameras? I hope. Sounds like I need to call both companies and see what they suggest. 



#8 Dom543

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Posted 18 August 2014 - 12:19 AM

Rick,

 

The reducers that I listed are just the readily available off the shelf units. Most people put together their own two-stage focal reducers from various building blocks. One popular version is to combine the Meade or Celestron f6.3 reducer with a cheap 1.25"  x0.5 reducer from ScopeStuff or AgenaAstro. The spacing between the two reducers and between the x0.5 reducer and the sensor determine the ultimate reduction factor. You do some experimenting and you cannot go wrong. People also put together perfectly fine focal reducers from lenses bought from Surplus Shed. As said in the previous post, these small sensors take any focal reducers. If any sales person tells you about their "high quality" focal reducer, that means that they are trying to sell you some overpriced stuff.

 

--Dom


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#9 RightWill

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Posted 18 August 2014 - 04:00 AM

Thanks Dom that is very helpful.



#10 GlennLeDrew

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Posted 18 August 2014 - 02:11 PM

Rick,

The wide focusing range of SCTs usually permits the use of a wide array of accessories without requiring additional spacers to reach focus. Reducers for small-chip cameras like 1/3" and 1/2" video units are generally correspondingly small and of not overly large in-focus travel requirements, and so usually pose no problem for focusing, especially when attached directly, with no diagonal in between.

 

The f/1.8 reducer to be offered by AVS *seems to me* to be a bit of optical alchemy; I cannot see how such truly aggressive reduction of 0.18X can be performed without aperture reduction. The reducer itself would have to be of quite large aperture ratio, and almost certainly aspheric. The image scale is probably reduced as advertised, but I suspect the aperture could be reduced to something approaching 70%. Instead of a working f/1.8, it *might* be closer to f/2.8. But I would love to be proved wrong!



#11 Dwight J

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Posted 18 August 2014 - 08:13 PM

Be aware that aggressive focal reduction  causes vignetting, more reduction, more vignetting.  LPR filters help make it less noticable and reducing brightness helps until you start clipping the black.  mlight and light pollution really show itt at fast F ratios.  A variable reducer like the Mallincam MFR5 or an assortment of spacers with whatever one you choose will help you arrive at the best focal reduction for your scope and conditions.


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#12 KGoodwin

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Posted 24 August 2014 - 07:28 PM

RightWill,

Not sure if this is helpful, but I use the AVS Varioreducer with the Mallincam Xtreme successfully down to 0.38x, I think it could go lower with it, but I don't have the need for it.
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#13 RightWill

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Posted 24 August 2014 - 08:18 PM

RightWill,

Not sure if this is helpful, but I use the AVS Varioreducer with the Mallincam Xtreme successfully down to 0.38x, I think it could go lower with it, but I don't have the need for it.

Kyle, that is good news to know. It sure seems like the best product out there for the price. I'll assume this varioreducer will also work on the Jr Pro. I'm trying to see what my initial investment will be before I by a new rig for astro video.

 

 I wonder if someone out there has compared this AVS variable reducer to the Mallincam MFR-5?



#14 KGoodwin

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Posted 27 August 2014 - 07:11 AM

RightWill,

 

I think they're similar in intent, but different in execution.  The MFR-5 has two optics which you can vary reduction by spacing between them and between the final optic and the camera.  The Varioreducer uses a single optic and just varies the distance between it and the camera to change reduction factors.  I can't speak to the optical quality of the MFR-5 since I've never used one, but I have a feeling that given the fairly large reduction and image scale we tend to use for video (> 2 arcsec per pixel usually) minor optical differences are unlikely to impact the camera's image.  The main thing to watch out for would be the sort of large scale issues you encounter when using too much reduction: unacceptable vignetting, coma, field curvature, etc.  A comparison between the two reducers at various settings and 1/2" and 1/3" chip sizes that quantifies the effects of those induced aberrations would be a very useful comparison for someone who has both reducers to perform.  Those could certainly be different between the two, especially at the extreme end of the reduction adjustments.


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#15 mclewis1

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Posted 27 August 2014 - 09:39 AM

It would certainly be interesting to see a good side by side comparison of the AVS Varioreducer, Optec NGM, and perhaps a good (Japan) model Meade 3.3 focal reducers. I include the now discontinued Meade reducer only because it was effectively the standard for aggressive focal reduction with video cameras. It would be valuable to also include the MFR-5 but it's not quite as aggressive in reduction as those others and this makes effective comparisons a bit more complex. 

 

The MFR-5 is a .5x reducer in it's original configuration when used with most cameras today. You have to watch for out for earlier descriptions of this product ... as with all focal reducers the spacing back to the sensor is a major determining factor and Mallincam 1/2" video cameras have varied in their construction over the years. Early on they had as much as 17.8mm of spacing (sensor to C/CS mounting surface), then it was the C mount 15.8mm, and now most are built to the CS specification - 12.5mm. The result was MFR-5 reducers used on the earlier cameras delivered more than .5x and advertised as such.

 

As Kyle mentioned with the MFR-5 you have two options for changing the characteristics of the reducer - a C spacer(s) between the two sets of optics and C spacer(s) between the rear optic and the sensor in the camera. You could have a whole discussion just on the effect of those variables.

 

There would be similar variables if we also included the popular stacked reducer setup (SCT f6.3 plus the 1.25" .5x reducer) in the comparison.



#16 A. Viegas

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Posted 27 August 2014 - 01:32 PM

Given that you are just starting in video astronomy perhaps the best advice is just keep it low cost to start. You can buy a scopestuff or agena 0.5x 1.25" reducer for like $50 and you can buy a used c6.3 reducer from the classifieds here or on Amart for like $50-75 also. Together these would get you to under F4 and you can always remove the 0.5x when you want bigger image scale...

As for your camera choices well maybe you can start lower cost with the AVS DSO which is just $99 and avaPilable now. You can buy power and video cables on amazon for $20 and you are in business fOr under $200...

Then in 3-9 months you can always upgrade to a better camera and you have the old one for a guide camera or video finder.

Just my 2c

Al
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#17 GlennLeDrew

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Posted 27 August 2014 - 02:54 PM

I've compared the basic, single-lens 0.5X reducer with the 2-lens MFR-5. At the same reduction factor the MFR-5 introduces less spherical aberration because the 'work' is being done by two achromats, not one.


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#18 DonBoy

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Posted 27 August 2014 - 03:16 PM

Glenn,

 

Which .5x reducer?

 



#19 Relativist

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Posted 27 August 2014 - 08:04 PM

I'd also consider the new revised/improved MFR-5. Since I'm on a reflector I'm waiting for the revised MFR-3 before I jump on board.


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#20 GlennLeDrew

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Posted 27 August 2014 - 11:34 PM

Don,

It was an Antares 1.25" 0.5X reducer. Others of similar form are essentially identical, in that they are simply 25mm f/4-ish achromats just like small binocular objectives. They are off-the-shelf lenses designed to work at an infinite/one focal length set of conjugates. Even if perfectly made, the spherical surfaces will induce spherical aberration because the system entrance pupil is very much nearer than infinity. Moreover, the more aggressive the reduction factor--achieved by increasing the separation between reducer and final focus--the worse the spherical aberration.

 

Note that here I'm restricting to the axial image, and not even touching upon the off-axis aberrations, which include coma, astigmatism and field curvature.

 

A two-lens reducer induces a bit less spherical aberration because each component is individually redirecting the image-forming light less strongly. An analogy could be drawn from a comparison of few-lens vs many-lens eyepieces in handling steeper light cones.


Edited by GlennLeDrew, 27 August 2014 - 11:41 PM.

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#21 jonstarrysky

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Posted 29 August 2014 - 06:23 PM

Guys can I come in with a question about reducers for fast Newtonians ? So if the scope is already f/4 and spare in-focus isn't a major limitation, how much reduction can be achieved before image quality starts to look ugly, eg coma, vignetting ?  Would the aim be to achieve modest focal reduction and call it a day at f/3 ??

 

I have the Mallincam 2" Focuser DOB Adapter that allows a camera to effectively sit just inside the focusser opening. This should allow more aggressive focal reduction.

 

I heard someone (an experienced source) comment that they found it is easier to reduce f/5 to f/3 and avoid ugly aberrations than starting closer at f/4 and to take that down to f/3...

 

And would coma not be seen from a fast newt on a video camera (I have stellacam) ? Visual use with an eyepiece this would indeed be evident.








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