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Portaball Users - Sing Their Praises

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#76 Don W

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Posted 06 March 2019 - 12:48 PM

Dave is around to provide support for Portaballs out there now, but I don't think he'll be building many new ones if any.



#77 areyoukiddingme

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Posted 06 March 2019 - 01:57 PM

Turbulent air is not the main issue - though it can cause problems.   The primary concern is the mirror is a heat sink and there is a temperature differential between the air that hangs very close to the surface of the mirror compared with the rest of the air in the sphere.  This temperature delta creates a boundary between the different air masses inside the sphere.  In the Portaball, the fan mixes the air up so that the starlight is traversing a homogeneous air mass.   IMO, the slight turbulence caused by the fan is less damaging to the image then having the light path traverse two distinct air masses, twice. 

 

Thanks for your response. . . I realize that the purpose is to have a small boundary layer fan to remove that from the surface of the mirror. My concern is that even a small fan is going to send air across the mirror, hit the walls on the opposite side of the sphere, and then send turbulent eddies throughout the tube. I'm a bit skeptical that you get a "homogenous air mass" by using such a system. In theory, that would be exactly what you want, but in practice I'd think it difficult to achieve.

 

If that's true, it seems that it's a question of picking your poison--if the extra turbulence is less than the effect of the boundary layer, then I guess you come out ahead?

 

A potentiometer on a boundary layer fan would seem to be a good idea for experimentation. . . 



#78 peleuba

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Posted 06 March 2019 - 04:10 PM

I think you might be missing the point on temperature deltas as that diff in temps of the air is what harms the seeing.  Movement of air that is of equal temperature provides superior image steadiness then two air masses of differing temperatures in very close proximity to the surface of your glass.  

 

I can only tell you what my experiments have shown to me.  I encourage you to try your own.  Nevertheless, I was the person who suggested to Dave to design the boundary layer scrubbing fan.  In my climate, the fan is too small, so I installed a larger one.   In Florida, there have been good results with the small fan where the temp deltas are not as great.


Edited by peleuba, 06 March 2019 - 05:07 PM.

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#79 GeneT

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Posted 06 March 2019 - 09:44 PM

Thought everyone would enjoy this  picture. This image was from a jealous club member who wished he was a Pball owner! LOL

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#80 The Ardent

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Posted 06 March 2019 - 09:49 PM

I’d like to see them back in production.

#81 areyoukiddingme

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Posted 07 March 2019 - 12:53 PM

I think you might be missing the point on temperature deltas as that diff in temps of the air is what harms the seeing.  Movement of air that is of equal temperature provides superior image steadiness then two air masses of differing temperatures in very close proximity to the surface of your glass.  

 

I can only tell you what my experiments have shown to me.  I encourage you to try your own.  Nevertheless, I was the person who suggested to Dave to design the boundary layer scrubbing fan.  In my climate, the fan is too small, so I installed a larger one.   In Florida, there have been good results with the small fan where the temp deltas are not as great.

 

 

I believe we are on the same page with the sources of poor mirror performance because of temperature deltas. I realize that removing the boundary layer is a good strategy, as is extended equilibration with a fan or fans on the back of the mirror.

 

It's the extent to which having turbulent air in the sphere of a Portaball is helpful vs. harmful where I have questions.I don't know the answer, so I'm glad to hear you have been experimenting and had good results.

 

I am assuming--perhaps quite wrongly--that we would hope for boundary layer fans to produce a laminar flow of air across the mirror surface, and then out of the path of the mirror face to be optimal. But it sounds like you have found that a relatively large fan is better than a small one in your Portaball.

 

My guess is that achieving good results with removing the boundary layer in a Portaball sphere is relatively difficult compared with a more open, traditional Dob structure with an open back.

 

Anyway, sorry to nag you on this . . . this is something I have been thinking of doing for quite a while and I'm keen to hear opinions and results of boundary fans.



#82 ltha

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Posted 07 March 2019 - 02:21 PM

Realizing there probably aren't that many Portaball's relative to other dobs, I'd loved to hear from those who own them.

 

What do you like?

 

What don't you like?

 

Discuss some of the features they have to offer.

 

Thank you in advance,

john

To more directly answer the OP's questions:

 

What do you like?

 

The beauty of the Portaball for a visual observer is that is it is so intuitive to use and reaches any part of the sky with equal ease. Peter built them to the height of the owner (assuming you purchased new) which eliminated any issues with eyepiece height even at zenith. I have always found collimation easy and quick, and it holds collimation very well. Mine came with the older (not the lightweight) Feathertouch which spoiled me for any other focuser. It was built to reach focus with the eyepieces I owned and used most at the time I placed the order and balanced for them as well. When I added additional eyepieces Peter fabricated a recessed 2" to 1.25" adapter that allowed for greater in-focus and I was able to use them too. The optics are excellent and I have had little issue with cooling. Well, maybe I should say that in So Cal where I lived at the time I ordered the scope I had no problem with cooling, that may change here in Central Oregon.

 

Over the years I have had the chance to compare the scope to many others - Newtonian/DOBs, APO refractors, achromats, Makes-Newts, etc and it consistently produces excellent images given good seeing. It handily matched/beat by a bit my 8" D&G refractor on planetary and lunar while presenting a more esthetically pleasing image (no color error). At 12.5" it is large enough to do a great job on globulars though the 18" Starmaster bests it there. But I cannot transport the SM anywhere as easily as the PB and around zenith there is no comparison in terms of scope movement.

 

What don't you like?

 

That I did not order the 18" Peter offered many years back. Some folks regret not being able to use digital setting circles, goto, etc but I enjoy knowing the sky and finding things so not a minus. At the time I placed the order for the 12.5" I also ordered a Roundtable tracking platform but have not really used it much. I far prefer seated observing and binoviewers for planetary viewing and the PB is not as easy to use in those areas. Peter would make a spare set of poles for a bino unit but I never ordered them, and in terms of seating I have an observing chair that gets me there at most positions other than zenith, but not as easily as the refractors do. However, I can take the PB anywhere and have it up and running pretty quickly while I am apprehensive about disassembling and reassembling the TEC200ED by myself. And the HGM-200 ( a superb mount!!) adds a lot of time and weight which challenges any concept of "portable" I have ever entertained. It can be moved, but the Portaball is, well, portable!


Edited by ltha, 07 March 2019 - 02:24 PM.

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#83 peleuba

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Posted 07 March 2019 - 04:39 PM

What don't you like?

 

<BIG SNIP>

 

That I did not order the 18" Peter offered many years back. 

 

This is an old thread and I don't think the OP is around any longer.  He posted this originally under a diff handle and changed it to the current one sometime ago.  He's not logged in to CN in quite awhile.

 

Nevertheless, its a good thing you never ordered the PB-18 because it never existed as a production telescope and none were ever delivered.  Dave Jukem refunded the money on all the orders for the 18 when he inherited the company.

 

Dave continued to work on it and below is a photo of the prototype of the PB-18 complete with Zambuto mirror at NEAF from 2010.  Dave is standing next to the PB and I took the photo.

Attached Thumbnails

  • PB18.jpg

Edited by peleuba, 07 March 2019 - 05:38 PM.

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#84 Bob S.

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Posted 07 March 2019 - 05:20 PM

I think you might be missing the point on temperature deltas as that diff in temps of the air is what harms the seeing.  Movement of air that is of equal temperature provides superior image steadiness then two air masses of differing temperatures in very close proximity to the surface of your glass.  

 

I can only tell you what my experiments have shown to me.  I encourage you to try your own.  Nevertheless, I was the person who suggested to Dave to design the boundary layer scrubbing fan.  In my climate, the fan is too small, so I installed a larger one.   In Florida, there have been good results with the small fan where the temp deltas are not as great.

I can fully back up Paul's reports that here in Florida, that tiny laterally movable 1" fan was surprisingly effective in scrubbing off just enough boundary layer that it was consistently additive in a late model Dave Jukem built 8" PB that I owned. Was it not for lack of DSC's, I would never, ever have parted with it. My personal observing frequently takes me beyond our solar system and looking at the same eye candy Messier's gets old for me.


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#85 peleuba

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Posted 07 March 2019 - 05:52 PM

 

Anyway, sorry to nag you on this . . . this is something I have been thinking of doing for quite a while and I'm keen to hear opinions and results of boundary fans.

 

Not nagging.  There are no absolutes when it comes to thermal management.  Sometimes things don't behave as you would expect.  You'll have to experiment with what works in your environment.

 

Last thing I will say is that I wish there was a 3" diameter hole in the sphere immediately below the mirror that exposed the cooling fan to the outside air.


Edited by peleuba, 07 March 2019 - 05:53 PM.


#86 GeneT

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Posted 09 March 2019 - 01:15 AM

Thought everyone would enjoy this  picture. This image was from a jealous club member who wished he was a Pball owner! LOL

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#87 mkothe

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Posted 09 March 2019 - 08:40 AM

I never met anyone who did not like the Portaball. The anit-dew (heated) QuickFinder was a great idea, and I don't know why it was never offered on the open market.


There was a heated Quickfinder? I never realized this. Mine just gets the power from the scope, but there is no heater.

#88 Pierre Lemay

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Posted 09 March 2019 - 11:02 PM

Nevertheless, its a good thing you never ordered the PB-18 because it never existed as a production telescope and none were ever delivered.  Dave Jukem refunded the money on all the orders for the 18 when he inherited the company.

 

Dave continued to work on it and below is a photo of the prototype of the PB-18 complete with Zambuto mirror at NEAF from 2010.  Dave is standing next to the PB and I took the photo.

Unfortunately the only way to own a large Portaball (or any ball scope), other than to find one second hand, is to make it.  I have built numerous ball scopes over the years.

 

My 20 inch is the largest. You can find details on how to build one here (only for the adventurous!):

 

DSC01962.jpg

 

Another, more accessible project is building an 8 inch ball scope, which I describe here:

 

8 inch first light.jpg

 

All my ball scopes are mounted on a simple tracking platform I invented in the mid-90's, which adds no height to the eyepiece, nor weight to the instrument.

 

 


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#89 sedmondson

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Posted 10 March 2019 - 11:24 AM

There was a heated Quickfinder? I never realized this. Mine just gets the power from the scope, but there is no heater.

Has it ever dewed over? Pete mounted a resistor onto the glass surface of the QuickFinder that applies heat. That is why it is powered by the 12V system of the Portaball. Otherwise, the QuickFinder would only need a 2032 battery to power it. 


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#90 mkothe

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Posted 10 March 2019 - 07:16 PM

Has it ever dewed over? Pete mounted a resistor onto the glass surface of the QuickFinder that applies heat. That is why it is powered by the 12V system of the Portaball. Otherwise, the QuickFinder would only need a 2032 battery to power it.

Ooh, interesting, I never realized that! I thought the power was just so you didn’t have to worry about replacing batteries. I don’t recall seeing this feature mentioned in the manual or other descriptions. I stopped using the powered Rigel shortly after acquiring the scope second hand due to electrical issues. I just compared the powered Rigel with my regular backup, and the resistor is clearly visible but unobtrusive if one looks closely.

I have since made progress getting power back through the truss pole, but the wiring in the UTA still has issues. I added a mini-dew heater to power strips for my 9x50 finder and even bought a Rigel heater for my other unit.

Now I am motivated to get the original Rigel hooked up again! For this I would need a 3.5mm to RCA adapter. All the ones I can find have a split to 2 RCA jacks for audio, or are the mono version, which I assume is no good for my purposes? Does anyone have a lead for an adapter to connect a male 3.5 to a female RCA jack? Something like this, but with 2 phases?

FYL 2x 3.5mm Mono Female Jack to RCA Male Plug Audio Adapter Cable Converter Gold https://www.amazon.c...i_TxBHCbSZ3HKV6


Michael

Edited by mkothe, 10 March 2019 - 08:14 PM.


#91 sedmondson

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Posted 11 March 2019 - 11:09 AM

Ooh, interesting, I never realized that! I thought the power was just so you didn’t have to worry about replacing batteries. I don’t recall seeing this feature mentioned in the manual or other descriptions. I stopped using the powered Rigel shortly after acquiring the scope second hand due to electrical issues. I just compared the powered Rigel with my regular backup, and the resistor is clearly visible but unobtrusive if one looks closely.

I have since made progress getting power back through the truss pole, but the wiring in the UTA still has issues. I added a mini-dew heater to power strips for my 9x50 finder and even bought a Rigel heater for my other unit.

Now I am motivated to get the original Rigel hooked up again! For this I would need a 3.5mm to RCA adapter. All the ones I can find have a split to 2 RCA jacks for audio, or are the mono version, which I assume is no good for my purposes? Does anyone have a lead for an adapter to connect a male 3.5 to a female RCA jack? Something like this, but with 2 phases?

FYL 2x 3.5mm Mono Female Jack to RCA Male Plug Audio Adapter Cable Converter Gold https://www.amazon.c...i_TxBHCbSZ3HKV6


Michael

If you are bypassing the UTA wiring, then you will need an adapter. How about just cutting off one of the RCA connectors in the split RCA audio adapter you mention?

 

Pete used RCA connectors to bring power to the UTA and then a mini stereo connector for the Rigel. Don't know why unless he wanted to carry the power on the innermost section of the stereo plug to minimize chances for shorting out when plugging in/out.



#92 mkothe

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Posted 11 March 2019 - 03:45 PM

Thanks, that would be easy. Will a single wire be enough, though? I thought I need two to complete the circuit. I’m a bit challenged when it comes to wiring, but maybe either of the two RCA plugs from the splitter will contain two wires and function to power the finder?

I guess I could just try it, but don’t want to damage anything. :-)

Michael

#93 SkyRanger

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Posted 11 March 2019 - 08:37 PM

My 12.5 after upgrades from Dave Jukem:

 

 

GTG_2285.jpg

 

 

GG


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#94 sedmondson

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Posted 12 March 2019 - 01:15 PM

Thanks, that would be easy. Will a single wire be enough, though? I thought I need two to complete the circuit. I’m a bit challenged when it comes to wiring, but maybe either of the two RCA plugs from the splitter will contain two wires and function to power the finder?

I guess I could just try it, but don’t want to damage anything. :-)

Michael

It might be better just to make your own adapter. The center pole of the RCA (from the truss rod) should carry the 12V and the outer shield should be ground. The stereo plug has 3 contacts, and you will have to route the 12V and ground from the RCA to the proper stereo plug contact. Sorry but I don't know which ones you would want. Maybe someone who has customized or reworked their portaball could help you.

Anyone?




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