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biggest field stop usable on Baader maxbrights

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#1 Alex Gastélum

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Posted 08 February 2013 - 12:51 PM

I just got the Baader maxbright binoviewer and want to know which eyepieces will work best on low power, I do not like the mushy field stop that my 24 panoptic or 32 TV plossl shows near the field stop.
I think the prism aperture on the unit is 22mm, the TV eyepieces I have have field stops of 27mm.
I want to know which low power eyepieces you have tried on the Baader maxbrights that show a sharp field stop.

Thank you all in advance.

#2 GlennLeDrew

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Posted 08 February 2013 - 01:28 PM

Just for background info, the degree to which a field stop can be larger than the rear prism aperture depends upon:

- The distance between the prism aperture and focus (field stop). The farther back the focus lies, the larger can be the field stop, due to the prism aperture being thrown even farther out of focus.

- The focal ratio of the light cone passing through the binoviewer. As seen from the focus, an angularly larger entrance pupil makes for a blurrier shadow of the rear prism aperture, thus allowing a slightly larger field stop.

These effects are certainly not like night and day, but they can make a difference amounting to a couple or few millimeters for any given prism aperture.

#3 Mark9473

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Posted 08 February 2013 - 02:20 PM

My favourite low-power pair, that work exquisitely in the Maxbright, are the 25 mm volcano-top orthos giving 28x in my APM 107.

#4 Alex Gastélum

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Posted 08 February 2013 - 08:12 PM

Thank you both.
I was wondering if the 32mm BCO will work.
I am considering the volcano top orthos 25mm or TV plossl 25mm.
My 28mm Rke's show just a little light cut off on the very field stop.

#5 Eddgie

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Posted 08 February 2013 - 11:39 PM

I used the following eyepeices with the Maxbrights.

22mm Panoptics... Showed vignetting.

19mm Panoptics... Crisp field stop (21.3mm field stop)

19mm Orion Flat Field... Crisp field stop

20mm Expore Scientific 68 degree AFOVs. Mostly crisp, but with a slight cutoff on part of the field. I think that one of the prisms may have had one edge right at the rear aperture.

The Orion Flat Fields have a field stop that is right at 22mm or 23mm, so that seems to me to be about the maximum that can be used that will result in a crisp edge of field.

In fact, the Orion Flat Fields worked quite well in my SCTs. They are only 65 degree AFOV, but I think that they actually gave as good a performance as the Hyperions.

If you want a bit bigger exit pupil though, I think some 25mm Plossls would be great. The field stop of the Televue 25mms is 21.2mm, and based on the eyepecies I have used, in the Maxbright, I would think that 25mm Plossls would be an excellent choice.

#6 Mark9473

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Posted 09 February 2013 - 07:25 AM

I was wondering if the 32mm BCO will work.
I am considering the volcano top orthos 25mm or TV plossl 25mm.


I would expect the new Baader 32mm Plössl (it's not an ortho) to work just like the TV 32mm Plössl that you already tried.
The TV 25mm Plössl has a 21.2mm field stop so that will work perfectly, like Eddgie said.

#7 Mark9473

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Posted 10 February 2013 - 02:41 PM

19mm Panoptics... Crisp field stop (21.3mm field stop)

19mm Orion Flat Field... Crisp field stop

The Orion Flat Fields have a field stop that is right at 22mm or 23mm, so that seems to me to be about the maximum that can be used that will result in a crisp edge of field.


The Orion spec for the 19mm Edge-On Flat Field's field stop diameter is 21.3 mm just like the Panoptic. I wonder if there's something a bit longer having a 22-23 mm field stop.

#8 Alex Gastélum

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Posted 11 February 2013 - 12:44 PM

the Hyperion 21mm has a 22.5 field stop

#9 Mark9473

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Posted 11 February 2013 - 04:36 PM

Thanks; have you by chance used a pair in the Maxbrights?

#10 Alex Gastélum

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Posted 11 February 2013 - 08:53 PM

no, I saw that on the hyperion data sheet

#11 Alex Gastélum

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Posted 12 February 2013 - 12:58 AM

any of you enjoy the 24 panopitics on the maxbrights?, is the mushy field stop a problem?






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