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Portaball - new owner with questions

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#26 areyoukiddingme

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Posted 13 October 2020 - 06:32 PM

I would quibble with the new cell being worth it, as it does not have side supports.

 

I have that cell--it's an aluminum plate with 6 supports that are meant to be siliconed in place.

 

Having tried it on mine, 12.5" and 1.625" thickness, I found it induced astigmatism when I tipped the scope at an angle. It may be possible to get this to work without side supports if you are careful with the initial siliconing, but I have found the Mk2 (thanks!) wooden cell with 6 side support does a better job.

 

When I got my primary re-coated I looked for advice on the reinstall here on CN. The advice I got was to suspend the primary over mirror supports a little while the silicone cured. That way the metal supports would not be in direct contact with the primary.

 

But that did not work so well for me. It is difficult to find a way to support the primary so that a gap remains between the supports and mirror. So I think I may have induced some astigmatism there--once the silicone cured, removing those supports induced some small forces.

 

So, it may be better to place the primary directly on the supports while the silicone cures without anything inducing any deformation to the primary. But keep in mind that if you need to get those supports off later, it can be VERY difficult.

 

Maybe the newer cell will work with the full thickness mirrors as it will be less likely to warp. In any case, I'd be trying the original cell before considering upgrades or tinkering (extra side supports might be installed).



#27 mjgillen

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Posted 13 October 2020 - 08:53 PM

I would like some information and advice on the secondary mirror, holder, and spider for this telescope.

 

The current setup is a four vane metal spider with Phillips head screws to hold it in place (no adjustment knobs). The secondary holder has three hex head screws for collimation adjustment and the "regular" mirror holder. The mirror seems OK, kind of dirty nothing terrible.

 

So my questions are:

 

1) What are the dimensions of the secondary mirror?

 

2) Does anyone know where to get knobs that can replace the Philips head screws on the spider?

 

3) Should I keep the spider, holder, and secondary mirror or upgrade? Right now there is nothing obviously wrong with the secondary mirror and its holder or spider.

 

Thanks guys!

Michael



#28 peleuba

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Posted 14 October 2020 - 09:43 AM

I would like some information and advice on the secondary mirror, holder, and spider for this telescope.

 

Post a picture of the secondary/holder/spider.  It will be easier to assist.

 

 

 

 

 

1) What are the dimensions of the secondary mirror?

 

2) Does anyone know where to get knobs that can replace the Philips head screws on the spider?

 

3) Should I keep the spider, holder, and secondary mirror or upgrade? Right now there is nothing obviously wrong with the secondary mirror and its holder or spider.

 

 

(1)  You'll have to tell us as you have the mirror.  Though, I am pretty sure its 2.14" but check to make sure its not larger - there is a chance it will be 2.60".   Typically, secondaries are sized by minor axis which is the smaller, side-to-side measurement.

 

 

(2)  I am not sure what you are describing.  The secondary adjustment/collimation screws are not part  of the spider.  Rather, they push against a plate on the secondary holder.  A picture here would be best.  If its the secondary adjustment screws I described in the previous sentence, then I would advise against thumb knobs.  Its much easier to get a more precise, minute adjustment with a tool.   Though I would absolutely replace the screws with Hex Head Set Screws.  See the photo below.   They can be found at any good hardware store.  But my favorite place to purchase is Boltdepot.com 

 

 

(3)  Yes, keep the spider.   Now, I am not recommending you do this, but I had custom secondary holders manufactured to my specs by PreciseParts for my Portaballs.  I wanted something that was all metal and anodized.  This was quite expensive to do and I do not recommend it for the average user.  Moreover, I probably would not do it again.  However, I would take the opportunity to put a new secondary mirror into the scope.  You can get very accurate flats now.  See here:  https://www.antareso...m/SEMirrors.php

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  • screws.jpg

Edited by peleuba, 14 October 2020 - 09:44 AM.


#29 mjgillen

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Posted 14 October 2020 - 10:25 AM

Hello Paul thanks for the reply. I measured the secondary and it is 2.60"

 

Also, the adjustment screws for the spider are going to have to do for now as its very tight getting the UTA into the ball so not a lot of room for extra protrusions.

 

My secondary holder has hex nuts like you show so I'm OK there too...

 

Will likely get a new secondary mirror... any advange getting a 2.14" vs a 2.60"?

 

Michael

 

 

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#30 peleuba

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Posted 14 October 2020 - 11:15 AM

Hello Paul thanks for the reply. I measured the secondary and it is 2.60"

 

 

Great Photo!   

 

OK - so the scope was made with a 2.60" secondary - I would keep it that size.  You will, most likely, be cutting off light from the primary mirror if you go any smaller.  This would, in essence, act as an aperture mask - which you do not want.

 

Keep the spider.  I would upgrade the secondary holder to one from AstroSystems.  See here:  https://astrosystems.biz/sechold.htm

 

You purchase the 2.60 size to match your secondary mirror.

 

These AstroSystem holders are 4 screw instead of the existing 3.  Some of the AstroSystem holders come stock with thumb screws - the 2.60" size does.

 

While the secondary mirror and holder are out of the scope, take this opportunity to spray a coat of flat black on the interior of the upper cage and spider.


Edited by peleuba, 14 October 2020 - 01:39 PM.

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#31 mjgillen

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Posted 17 October 2020 - 07:52 PM

Going to rethink the focuser.


Edited by mjgillen, 18 October 2020 - 09:40 AM.


#32 Don H

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Posted 18 October 2020 - 03:47 PM

Going to rethink the focuser.

Congratulations on your new to you PB scope! I have always admired the PB design ever since I first saw Peter Smitka with them at AstroFest. If I could have afforded one at some point, I think the 12.5" is the size I would have liked best. The Feather Touch screw pattern is the same as the JMI, 2.75". I think you would want to get their lightweight version, which is only an ounce or 2 heavier than the JMI, but even more expensive. Once you add a curved base, you are looking a $700. Even so, it is still less than a 21mm Ethos eyepiece. I have JMI focusers on my 12.5" f/5.9 and 10" f/6.3 and they still work very nicely. I made a 14.3" f/4.7 and a 13.1" f/5.3 that both had FT focusers. Each time I turned the FT focuser knob, it made me smile. But back when I purchased those, they were almost half the price they are now. That is currently keeping me from getting another one for the 10 or 12.5". Your 12.5" f/4.8 might benefit from a 2 speed, and not having to drill any new holes is a plus. If you intend to use heavier eyepieces and coma correctors, the FT will manage the load better. But then you will also most likely need to add more ballast in the ball, which can cause cooling issues and other concerns. If I had it, I would probably be happy to keep the JMI and use a lightweight 30-32mm 2" eyepiece for wide field views, then switch to a 24mm Pantoptic for a bit more power and darker sky background. After that, maybe a couple of T6 Naglers and possibly one or two DeLites for high power planetary views. 

 

I think the secondary holder and spider may be early versions of Astrosystems. They might be able to provide 3 replacement thumbscrews if you want to adjust the diagonal without tools. Otherwise, you could take one to a hardware store and just replace them with cap screws that are a bit longer. 



#33 GeneT

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Posted 18 October 2020 - 04:24 PM

Myself, I would clean it the normal way with it in place and just make sure everything dries out.  I would remove the electronics box.  

 

I use this technique:

 

https://youtu.be/9Y8xFnXFVGQ

 

Jon

Peter Schmitka became a friend of mine as a result of me buying a 12.5 inch Portable from him. He spent a day and night with me in San Antonio on his way to the Texas Star Party a few years before he died. To the issue of cleaning the mirror. Peter recommend leaving the mirror in its place in the telescope,  putting cloths all around the mirror, and base to catch the water. That is what I did and it worked fine. Regarding using larger and heavier eyepieces, I bought some ankle weights that strap on. I cut them in pieces and placed them around the base inside the sphere. I tried different weight combinations until I found the right balance. The weights did not have to be adjusted for the lighter eyepieces. Get the balance correct for the heavier eyepieces and the lighter ones will be fine. Stiction might be an issue. Go slow on how much Turtle wax you put on the sphere. You can always add more, but it is a challenge taking it off. I reccomend calling Dave at Mag 1 and buying his new standard mount for your 12.5 incher. You will have no stiction problems with his new mount. I also own the aluminium sphere. You don't have to baby it, but be careful on how hard you set it down, and banging into things.

 

I have owned more than a dozen telescopes. My 12.5 inch Portaball was my forever telescope. I kept it on my side of the closet. That avoided all kinds of issues. Peter told me that he wanted to build the largest telescope that was at the same time portable. He succeeded--outstandingly!


Edited by GeneT, 18 October 2020 - 06:29 PM.

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#34 mjgillen

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Posted 18 October 2020 - 10:50 PM

Don_H thank you for the info. I'm going to try the JMI for a while before I decide if I need to replace it. I haven't used the scope much due to cloudy and very very very wet nights lately plus I was waiting on some collimation tools so it sat idle for almost a week then the bad weather. I want to get some time in using what I have as a "baseline" and also get to know it better before I send the mirror off to be recoated. I solved my initial focuser issues with the all metal screws by replacing the 2" screws with some nylon ones and I found a 2"->1.25" adapter that allows me to attain focus in everything but my 31 Nagler grenade. I have a Tele View "flat top" on order and hopefully that will lower it enough for the hand grenade to attain focus. I had a 2-speed on my old Meade LightBridge and loved it. I hear very good things about the Feather Touch however $700 is almost half the cost of the telescope... but I know it'll be worth it in the long haul and I'll love using it and smile every time... just like I do now when I use my Tele Vue eyepieces. I ramble...



#35 mjgillen

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Posted 18 October 2020 - 10:52 PM

GeneT so far no balancing issue with my ball. Even with the 31mm Nagler. My mirror is 2" thick... that seems to be enough ballast...


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#36 JoshUrban

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Posted 19 October 2020 - 07:55 AM

I've got a 12.5" from '99 (fiberglass sphere), and absolutely love it.  Mine has a dew heater on the secondary.  If you're modding things anyway, you might want to add one of these.  I use mine fairly often.  

 

  Like GeneT mentioned, cleaning the mirror while mounted worked fine for me.  Some dew from the truss supports fell onto the primary on Saturday night, so that's what I'll be doing next.  (AND using the shroud during Autumn observing, too!)  

 

  Another awesome accessory with these:  binoviewers.  The sphere on mine isn't super slick at the moment, so it can actually balance them.  When it's fully waxed, though - forget it!  But wow, excellent planetary views (and even some deep space stuff) with stereo vision!  DISCLAIMER:  This is really tricky to get to actually balance with the design, and for some reason, the surface of mine is letting me do this right now . But generally, and obviously, light eyepieces are preferred over big clunky things.  


Edited by JoshUrban, 19 October 2020 - 08:21 AM.


#37 peleuba

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Posted 20 October 2020 - 10:13 AM

I think the secondary holder and spider may be early versions of Astrosystems. They might be able to provide 3 replacement thumbscrews if you want to adjust the diagonal without tools. Otherwise, you could take one to a hardware store and just replace them with cap screws that are a bit longer. 

 

I don't think they are AstroSystems.  Rather, I think its a Novak secondary holder.  Could be wrong on this, but looks like Novak to me.

 

In either case, kepp the the 4 Vane Spider and add a new 4 screw secondary holder from AstroSystems.  This will make collimation easier.   Once you precisely place the secondary under the focuser, then adjust its tilt and rotation, you only ever have to adjust the 2 screws that are in-line with the focuser. 


Edited by peleuba, 20 October 2020 - 10:15 AM.


#38 peleuba

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Posted 20 October 2020 - 11:15 AM

Don_H thank you for the info. I'm going to try the JMI for a while before I decide if I need to replace it. 

 

I know that we've have been trading emails back and forth, but I wanted to mention something about the focuser here on CN.

 

You mentioned to me the existing JMI has the same bolt pattern as the current FeatherTouch.  I was involved in the preliminary design and testing of the 2" Lightweight FT focuser made by Starlight Instruments.  The idea for a lightweight FT came out of a discussion that I had with Wayne Schroeder and Jon Joseph of Starlight Instruments while I was representing Mag1 at NEAF.  The primary interest was a FT specifically for the 8" and 10" Portaballs.

 

This LW model will work on your PB12.5.  You just need to make sure that you order a curved base for it to attach to the curved upper cage. 

 

Back in the day, the focuser was a weak point of the Portaball.   In the early 2000's Peter started using a 1ΒΌ homegrown Helical focuser on the PB8 and a 2" homegrown Helical on the 12.5.  Both of these focusers were inadequate but were used because of cost and weight.  They were quite light, if not very precise.  Using one of these on an earlier iteration of the PB8 motivated me to search for a better solution.

 

Today, Dave Jukem sells the PB with the lightweight FT as the stock focuser.  

 

Pictures of the older Helical focuser are below.  

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  • Focuser2.jpg
  • Focuser3.jpg

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#39 mkothe

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Posted 20 October 2020 - 10:54 PM

(1) Improved Truss Tube Connectors for the sphere.


Can you explain how they are different and better? Does Dave sell them for the older truss poles? I have a ca. 2005 PB with what I believe are the old connectors. The only thing I notice is that they need to be retightened occasionally (but not usually in the same session), otherwise they seem to work well.

Thanks,
Michael

#40 mjgillen

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Posted 21 October 2020 - 08:56 AM

@peleuba Thanks for the nice history on the focusers. Always fun to hear how stuff develops.


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#41 peleuba

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Posted 21 October 2020 - 08:57 AM

Can you explain how they are different and better? Does Dave sell them for the older truss poles? I have a ca. 2005 PB with what I believe are the old connectors. 

 

I will post a photo of the new connectors this evening. 

 

Yes, orders of magnitude better then the originals.   Yes, should fit your 2005 perfectly.  Yes, purchased from Dave.  They are not cheap, but they are good.

 

Made from annodized aluminum and they are clamps rather then connectors.  They mount on the sphere and come in sets of 3.  You need one set of 3 for your telescope.  Each individual clamp holds two truss poles.  



#42 mkothe

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Posted 21 October 2020 - 11:57 AM

I found some pictures, so got an idea. How are they better? Easier to install the poles? More stable? Do you have to modify the poles, or do they use the same connectors on the pole side?

Thanks,
Michael

#43 peleuba

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Posted 21 October 2020 - 12:55 PM

I found some pictures, so got an idea. How are they better? Easier to install the poles? More stable? Do you have to modify the poles, or do they use the same connectors on the pole side?  

 

Would be great (and useful) in this part of the thread to post the photos you found for the rest of the folks reading .  waytogo.gif

 

Same connectors used on the poles which is the "ball" side of the ball and socket.

 

No easier to install, but no worse then original, just different.  A single now knob holds a pair of poles in place.  

 

Yes, more stable.

 

No modifications required for the poles, but you need to remove the original "socket" connectors.  I have circled these in red in the attached photo.  This can be a pain because you have get a wrench on the nut that secures the machine screw.  This is best done with the primary mirror removed.   I then used a small mirror so I could see what I was doing.  Its not hard, just a little tedious.  I have done several of them for myself and for a friend who owns both a 12.5 and an 8. 

Attached Thumbnails

  • PB1.jpg

Edited by peleuba, 21 October 2020 - 01:41 PM.


#44 mkothe

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Posted 21 October 2020 - 01:45 PM

Thanks!

 

Here are two posts with pictures:

 

https://www.cloudyni...opes/?p=9698418

 

https://www.cloudyni...ises/?p=9189295

 

Michael


Edited by mkothe, 21 October 2020 - 01:49 PM.


#45 peleuba

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Posted 21 October 2020 - 01:59 PM

Thanks!

 

Here are two posts with pictures:

 

https://www.cloudyni...opes/?p=9698418

 

https://www.cloudyni...ises/?p=9189295

 

Michael

 

Ahh yes.  I was active both threads.   I am a longtime "friend of the firm" so-to-speak as it pertains to Mag 1 Instruments.

 

Some of the photos are mine from these threads.  The one below - taken from a thread linked above) is from my friend Bob Schilling.  I have circled the new truss attachment points red.  You can compare the old (on the left) with the new on the right.    

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  • PB3.jpg


#46 mjgillen

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Posted 21 October 2020 - 04:50 PM

Wow that photo of the "newer" Portaball has a lot of stuff going on. I like the older design - simple. I might add some dew control however I'm not sure I want a bunch of wires running around inside the ball and in the UTA. I'd rather keep it simple maybe just tap off the existing wiring to power a dew control panel... velcro that on the outside somewhere... mine has a switch for either "fan" or "LED" or OFF in the middle and I got the fan to work not sure what the LED is supposed to do or why? Illuminate the ball so I can mess around in there and "see" what I'm doing. Not sure about that if anyone knows...

 

Michael



#47 peleuba

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Posted 22 October 2020 - 08:34 AM

Wow that photo of the "newer" Portaball has a lot of stuff going on. I like the older design - simple. I might add some dew control however I'm not sure I want a bunch of wires running around inside the ball and in the UTA. I'd rather keep it simple maybe just tap off the existing wiring to power a dew control panel... velcro that on the outside somewhere... mine has a switch for either "fan" or "LED" or OFF in the middle and I got the fan to work not sure what the LED is supposed to do or why? Illuminate the ball so I can mess around in there and "see" what I'm doing. Not sure about that if anyone knows...

 

You are comparing your cavernous PB12 sphere to the the somewhat crowded sphere of a modern PB-8.  Yours has much more room in it and because of this looks less crowded.  Also, yours is a very basic design with only a single electrical circuit powering one fan and one LED.  The purpose of the LED is to illuminate the center spot on the mirror to make collimation easier using passive (non-lasing) tools.  It never quite worked as designed and was discarded in later iterations.

 

There are a lot of wires in the newer Portaballs, but that's by necessity.  The Achilles heal of the Smitka-era Portaballs was the electrical system.  No two were wired exactly alike and they were all wired in series - similar to Christmas lights.  Meaning the components are connected along a single conductive path, so the same current flows through all of the components to the next one in line.  When one stops working all of the downstream pieces also stop.  This was a headache to troubleshoot.  But for manufacturing purposes it was fast, simple and cheap to do.  So, Peter did it.

 

The newer Portaballs have more accessories requiring electrical current including: dew heater for secondary mirror; power to the Rigel for dew and to light the reticle; cooling fan on rear of primary; boundary layer fan in the sphere etc.  Dave Jukem has wired all of this in parallel using aircraft grade connectors and central junction points.  When one component fails, its easy to fix and does not take down all the other electric powered accessories.

 

I have gone a step further on my PB8 and added a second battery tray (for a second battery) and a larger boundary layer fan.  See photos.

 

My PB is the best visual scope I have ever used in its aperture class.  

Attached Thumbnails

  • IMG_1998 (Medium).JPG
  • IMG_1999 (Medium).JPG


#48 mjgillen

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Posted 22 October 2020 - 09:04 AM

Thank you Paul you continue to be a well of information on these Portaballs both old and new. I can see how the improvements on the wiring etc. on the new PBs is desirable however I am pretty happy with what I have. My needs will only be dew control for the secondary and eyepiece so probably not going to go crazy with any new wiring. When I send my mirror in to recoat I will likely replace all the wiring to match my simple needs.

 

Best,

Michael



#49 peleuba

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Posted 22 October 2020 - 09:07 AM

I can see how the improvements on the wiring etc. on the new PBs is desirable however I am pretty happy with what I have.

 

Understood.  Just letting you know there is method to the madness.



#50 Jon Isaacs

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Posted 22 October 2020 - 09:17 AM

I don't think they are AstroSystems.  Rather, I think its a Novak secondary holder.  Could be wrong on this, but looks like Novak to me.

 

In either case, kepp the the 4 Vane Spider and add a new 4 screw secondary holder from AstroSystems.  This will make collimation easier.   Once you precisely place the secondary under the focuser, then adjust its tilt and rotation, you only ever have to adjust the 2 screws that are in-line with the focuser. 

 

Another option would be to just drill and tap new holes in the existing plate or make a new plate and drill and tap 4 new holes. I have done this a time or two.

 

Regarding your focuser:

 

I think the JMI Next Generation 2 speed should be a direct swap for your focuser.  I like JMI focusers.. 

 

https://farpointastr...user-newtonian/

 

Jon




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