30 replies to this topic

[Peter Natscher]

I am still on the fence in choosing my next smaller telescope for observing the Moon and planets from my home with NELM 5 and Bortle 5 skies.  I want a easy set up and fast cool down time for this telescope.  My current decision now is between a premium 5" f/6 APO refractor or a 8" f/5.5 Zambuto Newtonian.  Which telescope would provide better lunar/planetary views at 200-250X?  I want to see shadow transits on Jupiter, detail on Mars, and possibly Enceladus next to Saturn.  I am more interested in moderate-to-high-power observing vs. low-power wide field.

 

Thanks,

Peter

[Scott in NC]

My current decision now is between a premium 5" f/6 APO refractor or a 8" f/5.5 Zambuto Newtonian. 

 

Do any premium 5" f/6 apo refractors exist besides the AP130?  I'm sure I'm probably forgetting something at the moment, but nothing else comes to mind right now.

[Peter Natscher]

 

My current decision now is between a premium 5" f/6 APO refractor or a 8" f/5.5 Zambuto Newtonian. 

 

Do any premium 5" f/6 apo refractors exist besides the AP130?  I'm sure I'm probably forgetting something at the moment, but nothing else comes to mind right now.

 

Too clarify things, I am considering a 130EDF (2003) vs. a new 8" f/5.5 Zambuto Portaball for observing only.   The ergonomics are quite different between these two but I am considering only the final planetary view at mid-to-high-powers. The 130EDF on a small GEM will allow use of my Zeiss binos and the 8" Portaball will not -- the bino won't balance on the Portaball, to heavy a load.  My eyes have a different sharpness now so the use of a bino keeps the view sharp. The 8" Portaball would be quicker to set up and at a much lower price compared to the 2X cost of the 130EDF alone and still would require a mount at an additional expence.

Edited by Peter Natscher, 01 October 2015 - 09:12 PM.

[Tony~M]

Hello Peter,

 

Hope you are well.

 

An 8 inch Portaball with a Zambuto mirror on a tracking platform is going to show you much more than a 130mm telescope, even a Starfire 130EDF.  Both of these will be sit down and observe telescopes.  If you were not going to get a tracking platform, I would go the refractor route.  You will want tracking for dedicated planetary or lunar observing.  Shoot, you could roll the dice and get a Sky-Watcher 8" f/6 collapsible Go-To dobsonian.  I have the non motorized version and it has a great mirror, however, your mileage may vary on the chinese mirrors.

 

Later,

 

Tony

[Tom and Beth]

Both Roland and Carl are artists when it comes to a smooth well corrected optic. With your criteria of Planetary viewing and "moderate-to-high-power observing vs. low-power wide field" I would choose aperture.

There's a lot to be said about the ergonomics of observing with an 8 inch F5.5 scope, while you are bundled up in a lawn chair on a clear dark night, too.

Edited by Tom and Beth, 01 October 2015 - 08:17 PM.

[dr.who]

This is a tough call. The APO will cool faster and you can easily push it up to 250x with decent seeing. But the Portaball has the aperture advantage by far. However it comes with a steeper cool down penalty.

 

You may be able to use your BV's with the Baader 1.7x GPC by the way. If it won't work and based on your comment regarding your preference for using your BV's then it seems the APO would be the better choice.c

[Peter Natscher]

This is a tough call. The APO will cool faster and you can easily push it up to 250x with decent seeing. But the Portaball has the aperture advantage by far. However it comes with a steeper cool down penalty.

 

You may be able to use your BV's with the Baader 1.7x GPC by the way. If it won't work and based on your comment regarding your preference for using your BV's then it seems the APO would be the better choice.c

The 130EDF f/6 with Zeiss bino and 2.6X GPC equals over 2,000mm focal length. That's enougth for a good sharp planetary magnification, but the planet will be dimmer and lacking the color that a 8" will show more easily. The 130EDF mounted higher will be less affected by surrounding air conditions, especially the warmer air rising off of the ground into the night.  I know this from using my Dobs.  The Dob's nemesis is the warmer ground near the primary mirror.

[dr.who]

Ah. I didn't know you had a 2.6x GPC. With that it should focus in the Dob too. I have a 2x Amplifier with my TV BV's and my UC15 which if f/4.2 comes to focus no problem with 24 Pan's and the BV. 

 

Very true about the ground heat gremlins. I usually lay a carpet or blanket down when I am using my Dob to combat this. It works for the most part. The other one I have to watch out for is my body heat impacting things because of the Truss design of the UC. I find this a problem when I am too lazy to put on the shroud.

[Otto Piechowski]

Peter, there is a guy in Ireland named Neil English who has both of the scopes you are considering; a 127mm achromat and an 8 inch newtonian.  He has written a great deal about his use of both.  You may find his comments, on this topic, interesting and perhaps useful.

 

Otto

 

neilenglish(dot)net

[Jon Isaacs]

Peter, there is a guy in Ireland named Neil English who has both of the scopes you are considering; a 127mm achromat and an 8 inch newtonian.  He has written a great deal about his use of both.  You may find his comments, on this topic, interesting and perhaps useful.

 

Otto

 

neilenglish(dot)net

 

I believe that Peter is looking at a 130mm apo and a rather serious 8 inch Newtonian.   The ironic thing about this thread: Peter has a lot of experience with scopes like these, if anyone should know which scope to choose, it would be Peter.  

 

My inclination would be the refractor, no wait for it to cool, no collimation issues.  Plenty good views.

 

Jon

[Peter Natscher]

 

Peter, there is a guy in Ireland named Neil English who has both of the scopes you are considering; a 127mm achromat and an 8 inch newtonian.  He has written a great deal about his use of both.  You may find his comments, on this topic, interesting and perhaps useful.

 

Otto

 

neilenglish(dot)net

 

I believe that Peter is looking at a 130mm apo and a rather serious 8 inch Newtonian.   The ironic thing about this thread: Peter has a lot of experience with scopes like these, if anyone should know which scope to choose, it would be Peter.  

 

My inclination would be the refractor, no wait for it to cool, no collimation issues.  Plenty good views.

 

Jon

 

I am always open to other's opnions.    Interesting that some would prefer the 130EDF and others the 8" Newtonian.

[stargazer193857]

I picked up the 8" again. In pieces it is not bad at all if you grab it in the right places. I do not count that as grab and go, but it certainly is not too big to move. If the bases are the same size, I would get the 10". Price is the main reason to get the 8" over the 10". 

[stargazer193857]

5" and 8" are complementary if the 5" is shorter. I would get both. My plan is 6" f5 and 10" f5. As for 14", price becomes an issue. But if you have to drive far, it could be worth it.

[davidmcgo]

I have an AP130EDT and an 8" f6 Newt built on a superb old Meade RG mirror that is optimized for lunar and planetary but in a solid Hastings tube with Protostar air spaced flocked liner, 1.5" quartz secondary, Blacknoise vibrationless cooling fan, low profile Feathertouch focuser.

 

I have had the AP since 1995 when I was in my 20s and used it a lot for lunar and planetary over the years and it did superbly well even in Colorado along the front range with rapid temperature drops and iffy seeing and gives very immediate views.  As I'm getting older however, I'm having more of a challenge with the 130 at 250x and up due to floaters and such in my eyes.  I don't use binoviewers personally, usually I find it hard enough to keep my dominant eye lined up with the eyepiece and I like the less glass approach.

 

I find the Newtonian more effective for me these days. It will let me use up to 400x or so on Mars and a given magnification is about 2x as bright and somewhat better resolution.  I typically use mine on a DM6 on a Stellarvue TSL6 as my 2 step "grunt and heave".  One trip for the mount, another for the OTA.  I included handles on the OTA at center of gravity for carrying and another couple to give leverage to rotate the tube if desired.  With the fan, it cools down within 30-40 minutes max and is inert thermally after that due to the air spaced liner killing any convection off the tube walls.  With the solid tube, I rarely need to tweak collimation and f6 is pretty forgiving with a pretty wide sweet spot.

 

I don't think the Portaball is going to work as well as what I built from a thermal or mechanical standpoint, the truss is open to air currents from you and the ground, the upper tube is extremely short and won't really handle anything heavy up top.  But if the price isn't that much more than a new mirror from Zambuto, you could always build a custom tube for it.

 

Dave

[areyoukiddingme]

I think it comes down to what scope you like the idea of . . . 

 

More important, I'm not buying the arguments! I don't think the arguments about the binoviewers, cool down or ground effects for the 8" Portaball are decisive. The 8" is not going to take long to cool (central CA right?), particularly if it's one of the newer thin mirrors. The scope has a built in fan, and you can speed things with a box fan. Also, the sphere is fiberglass (i.e., pretty well insulated), and you'll probably want to put it on a platform of some kind, so ground effects should be minimal.

 

As for the binoviewer thing, sure you can use them. You'll just need to add weight into the base to get balance, and add wax to the sphere for some increased static friction.

 

Having said all that, if I had a chance at an AP that'd be where I'd go :-)

[Tony Flanders]

Too clarify things, I am considering a 130EDF (2003) vs. a new 8" f/5.5 Zambuto Portaball for observing only.   The ergonomics are quite different between these two but I am considering only the final planetary view at mid-to-high-powers. The 130EDF on a small GEM will allow use of my Zeiss binos and the 8" Portaball will not -- the bino won't balance on the Portaball, to heavy a load.  My eyes have a different sharpness now so the use of a bino keeps the view sharp. The 8" Portaball would be quicker to set up and at a much lower price compared to the 2X cost of the 130EDF alone and still would require a mount at an additional expence.

I wonder if you couldn't get a Zambuto mirror (or equivalent) in some other design. The Portaball is a very cool design, absolutely wonderful for deep-sky browsing. But it seems all wrong for planetary observing. The freedom of motion and ability to track through the zenith would be irrelevant and wasted, and as you note, balance problems make it very hard to use binoviewers on a Portaball.

 

There's a lot to be said for old-fashioned equatorial mounts where planetary observing is concerned.

 

As for which is better -- in great seeing, with both scopes fully cooled down, I think the 8-inch reflector would produce a significant more detailed image. And, very important to my aging eyes, it would do that with a much bigger exit pupil -- no problems with floaters and the like, as when using a refractor at exit pupils less than 1 mm.

 

But in good-to-average seeing, I would probably prefer the refractor because it's so much less susceptible to thermal problems.

[Peter Natscher]

I have an AP130EDT and an 8" f6 Newt built on a superb old Meade RG mirror that is optimized for lunar and planetary but in a solid Hastings tube with Protostar air spaced flocked liner, 1.5" quartz secondary, Blacknoise vibrationless cooling fan, low profile Feathertouch focuser.

 

I have had the AP since 1995 when I was in my 20s and used it a lot for lunar and planetary over the years and it did superbly well even in Colorado along the front range with rapid temperature drops and iffy seeing and gives very immediate views.  As I'm getting older however, I'm having more of a challenge with the 130 at 250x and up due to floaters and such in my eyes.  I don't use binoviewers personally, usually I find it hard enough to keep my dominant eye lined up with the eyepiece and I like the less glass approach.

 

I find the Newtonian more effective for me these days. It will let me use up to 400x or so on Mars and a given magnification is about 2x as bright and somewhat better resolution.  I typically use mine on a DM6 on a Stellarvue TSL6 as my 2 step "grunt and heave".  One trip for the mount, another for the OTA.  I included handles on the OTA at center of gravity for carrying and another couple to give leverage to rotate the tube if desired.  With the fan, it cools down within 30-40 minutes max and is inert thermally after that due to the air spaced liner killing any convection off the tube walls.  With the solid tube, I rarely need to tweak collimation and f6 is pretty forgiving with a pretty wide sweet spot.

 

I don't think the Portaball is going to work as well as what I built from a thermal or mechanical standpoint, the truss is open to air currents from you and the ground, the upper tube is extremely short and won't really handle anything heavy up top.  But if the price isn't that much more than a new mirror from Zambuto, you could always build a custom tube for it.

 

Dave

I am concerned with how small the exit pupil is at planetary pawers on the 130EDF f/6.  Larger aperture keeps the exit pupil larger at 250X and above.

[areyoukiddingme]

 

Too clarify things, I am considering a 130EDF (2003) vs. a new 8" f/5.5 Zambuto Portaball for observing only.   The ergonomics are quite different between these two but I am considering only the final planetary view at mid-to-high-powers. The 130EDF on a small GEM will allow use of my Zeiss binos and the 8" Portaball will not -- the bino won't balance on the Portaball, to heavy a load.  My eyes have a different sharpness now so the use of a bino keeps the view sharp. The 8" Portaball would be quicker to set up and at a much lower price compared to the 2X cost of the 130EDF alone and still would require a mount at an additional expence.

I wonder if you couldn't get a Zambuto mirror (or equivalent) in some other design. The Portaball is a very cool design, absolutely wonderful for deep-sky browsing. But it seems all wrong for planetary observing. The freedom of motion and ability to track through the zenith would be irrelevant and wasted, and as you note, balance problems make it very hard to use binoviewers on a Portaball.

 

There's a lot to be said for old-fashioned equatorial mounts where planetary observing is concerned.

 

As for which is better -- in great seeing, with both scopes fully cooled down, I think the 8-inch reflector would produce a significant more detailed image. And, very important to my aging eyes, it would do that with a much bigger exit pupil -- no problems with floaters and the like, as when using a refractor at exit pupils less than 1 mm.

 

But in good-to-average seeing, I would probably prefer the refractor because it's so much less susceptible to thermal problems.

 

 

Just to be clear, using binoviewers on a Portaball is no more difficult than other designs. Weight and stiction solve that.

 

In fact, I'd go further. The PB design is not wasted for planetary; quite the contrary. The ability to rotate the eyepiece to any position that takes your fancy is an advantage of the design. That means you can easily get comfortably seated while tracking a planet.

[Jon Isaacs]

 

 

Too clarify things, I am considering a 130EDF (2003) vs. a new 8" f/5.5 Zambuto Portaball for observing only.   The ergonomics are quite different between these two but I am considering only the final planetary view at mid-to-high-powers. The 130EDF on a small GEM will allow use of my Zeiss binos and the 8" Portaball will not -- the bino won't balance on the Portaball, to heavy a load.  My eyes have a different sharpness now so the use of a bino keeps the view sharp. The 8" Portaball would be quicker to set up and at a much lower price compared to the 2X cost of the 130EDF alone and still would require a mount at an additional expence.

I wonder if you couldn't get a Zambuto mirror (or equivalent) in some other design. The Portaball is a very cool design, absolutely wonderful for deep-sky browsing. But it seems all wrong for planetary observing. The freedom of motion and ability to track through the zenith would be irrelevant and wasted, and as you note, balance problems make it very hard to use binoviewers on a Portaball.

 

There's a lot to be said for old-fashioned equatorial mounts where planetary observing is concerned.

 

As for which is better -- in great seeing, with both scopes fully cooled down, I think the 8-inch reflector would produce a significant more detailed image. And, very important to my aging eyes, it would do that with a much bigger exit pupil -- no problems with floaters and the like, as when using a refractor at exit pupils less than 1 mm.

 

But in good-to-average seeing, I would probably prefer the refractor because it's so much less susceptible to thermal problems.

 

 

Just to be clear, using binoviewers on a Portaball is no more difficult than other designs. Weight and stiction solve that.

 

In fact, I'd go further. The PB design is not wasted for planetary; quite the contrary. The ability to rotate the eyepiece to any position that takes your fancy is an advantage of the design. That means you can easily get comfortably seated while tracking a planet.

 

 

The 12.5 inch Portaball I saw had serious problems with just a finder and a filter slide. I know Gene T. is not able to use a Paracorr due to balance issues.  Looking at the design, the balance ratio seems very high, a lot of weight required to offset weight added to the upper cage. The other problem would seem to be the the weight needs to be balanced in 3 axes, a normal Dob only 2...

 

How much weight is required to balance your binoviewers, where did that weight go and how did it affect the cool down?

 

Jon

[Steve D.]

Peter, have you seen Teeter's premium solid tube dob?   http://www.teeterste....com/#!sts/cq3r

 

Balance issues and eyepiece position wouldn't be a problem if you decided you wanted to use binos. 

[Bomber Bob]

"With your criteria of Planetary viewing and "moderate-to-high-power observing vs. low-power wide field" I would choose aperture."

 

For strictly at home observing, I'd put together the best 8" reflector & GEM combo that I could find & afford.  I'd use the savings vice a 5" APO on accessories.

[Peter Natscher]

Peter, have you seen Teeter's premium solid tube dob?   http://www.teeterste....com/#!sts/cq3r

 

Balance issues and eyepiece position wouldn't be a problem if you decided you wanted to use binos. 

I've taken a look at Teeter's 11" solid tube Dob.  That could be a winner with a CZ mirror. Fairly easy setup and focuser could be located on the left side of tube -- a focuser location I use with my 16" JP AstroCraft.

[Peter Natscher]

"With your criteria of Planetary viewing and "moderate-to-high-power observing vs. low-power wide field" I would choose aperture."

 

For strictly at home observing, I'd put together the best 8" reflector & GEM combo that I could find & afford.  I'd use the savings vice a 5" APO on accessories.

The AP 130EDF ends up costing nearly $10k with GEM and accessories -- not a pretty picture.  I'd be paying for its astrograph capabilities that I'm not using.

[areyoukiddingme]

 

 

The 12.5 inch Portaball I saw had serious problems with just a finder and a filter slide. I know Gene T. is not able to use a Paracorr due to balance issues.  Looking at the design, the balance ratio seems very high, a lot of weight required to offset weight added to the upper cage. The other problem would seem to be the the weight needs to be balanced in 3 axes, a normal Dob only 2...

 

How much weight is required to balance your binoviewers, where did that weight go and how did it affect the cool down?

 

Jon

 

 

The PBs must be different based on the needs of the buyers who specified how much weight they intended to place at the top end. I bought my 12.5" used, and it was obviously a heavy loader. I have no issues with P2 and 21 Ethos once I had turtle waxed the sphere. Before that it would drop if it was at 30 degrees or so. Now I find that I can set up with Denk binotrons with no issue for balance. Just needs a new coat every 6 months or so keep the stiction right.

 

I know Gene has trouble with heavy loads on his PB, but I don't know why he hasn't added some weight.

 

As for cooling, my understanding is that there are lead sheets installed in the sphere. My 12.5 cools far faster and more efficiently than my 11" cat and 16" Lightbridge. There are holes in the sphere for ventilation. Using a portable 12 volt fan plus the internal fan for cooling and I'm typically able to get fantastic planetary views in central CA (an hour or two south of Peter) after a 30 minute blast. The sky conditions are typically by far my limiting factor.

 

IMO the only problem with the design is the inability to install encoders. Otherwise, Zambuto optics, incredibly smooth and easy motions to most any point in the sky makes it a winner for planetary viewing.

 

Perhaps Daniel Mounsey will chime in. I recall that he was gifted an 8" Portaball not so long ago. . .

[dr.who]

Odd question but... If we are in the 12.5" Portable range of scopes it weighs in at about 5 lbs more than the Obsession Telescopes Ultra Compact 15". And the UC 15 is at least 1" shorter than the Portaball. Perhaps the UC15 may be a better option as it's more aperture? Alternately there is the Litescope from Germany. Also high end optics but at a super light weight and able to literally fit into a suitcase with room to spare. the 14" is less than the APO for sure, gives more aperture by a long shot, is about the same size and weight as the 8", can take encoders, and comes with a premium mirror...