187 replies to this topic

[TareqPhoto]

My best planet views ever were with two 14.5" Zambuto and a 15" OMI all faster than F/5.  I had no problem using 500 to 800x and on the best nites over 1000x.  While i have had many great scopes nothing came close to the views with the smaller scopes as you run out light using very high powers.

 

Inch for inch nothing beats a refractor for the highest power cleaner views. My SW150ED and a super good 8" F/6 Newt are about dead even, but the ED shows Jupiters moons just a tad cleaner and sharper.

Yes, true, but how much is that 8" refractor or 14" refractor with quality optics?

 

Also, don't forget it is not only visual, maybe OP is asking for visual, but the title can be general and can add imaging too, so with imaging other factors may affect to or some thing can be forgiving, i doub't i will use for example TEC140 or SW150ED if i have over 10"-12" Newtonian for planetary imaging, and i am really thinking to add Zambuto mirror to my upcoming large Dobsonian so i can have the best i can have at that size, so how can i afford or find brand new that 20" refractor then to match or surpass my 20" mirror or even 10" refr?

[Richard Whalen]

Yes, true, but how much is that 8" refractor or 14" refractor with quality optics?

 

Also, don't forget it is not only visual, maybe OP is asking for visual, but the title can be general and can add imaging too, so with imaging other factors may affect to or some thing can be forgiving, i doub't i will use for example TEC140 or SW150ED if i have over 10"-12" Newtonian for planetary imaging, and i am really thinking to add Zambuto mirror to my upcoming large Dobsonian so i can have the best i can have at that size, so how can i afford or find brand new that 20" refractor then to match or surpass my 20" mirror or even 10" refr?

Planetary imaging with a 20" Newtonian does not make much sense for so many reasons. Unless you live in an area with incredible seeing all the time its going to be an exercise in frustration. Most locations never get below .25 arc seconds even in fleeting moments. Also a 20" mirror can take a long time to reach thermal equilibrium and until it does you wont be getting good data. I could go on and on.... There is a reason 11" to 14" scopes are popular for planetary imaging. I would recommend a large SCT or a large CFF classical cass no more than 16". 

 

Only way I would consider a 20" would be if I had a temperature controled observatory to house it at over 10000' elevation in excellent seeing conditions on a large custom mount. No dobs need apply.

[TareqPhoto]

Planetary imaging with a 20" Newtonian does not make much sense for so many reasons. Unless you live in an area with incredible seeing all the time its going to be an exercise in frustration. Most locations never get below .25 arc seconds even in fleeting moments. Also a 20" mirror can take a long time to reach thermal equilibrium and until it does you wont be getting good data. I could go on and on.... There is a reason 11" to 14" scopes are popular for planetary imaging. I would recommend a large SCT or a large CFF classical cass no more than 16". 

 

Only way I would consider a 20" would be if I had a temperature controled observatory to house it at over 10000' elevation in excellent seeing conditions on a large custom mount. No dobs need apply.

Elaborate your last lines, because i feel like going larger isn't gaining anything until you have controlled environment or issues are managed/sorted out.

Don't forget the visual part, so because i will use it for planetary imaging as main it doesn't mean i will never use it for visual, and when we talk about visual i hear or read that dobsonians are the best choice and going larger is better, frustration can happen with all astrophotography setup anyway, for DSO i have much more frustration to be honest, and i mentioned before that it doesn't have to be very incredible seeing to justify larger scopes, i see many members in another threads here showing off larger and larger dobs although they live in not optimal conditions, so what makes them to go larger than visual? 20" is still a good aperture, not so much than 16" yes, but it has slightly more, it is no logic to say that 14" has advantage over 10" but 20" hasn't over 16", i know the curve slope after 14" isn't going higher, but it is still increasing, so if the difference could be like %40 between 14" and 10" then it is maybe 10% between 20" and 16", for me that is enough.

 

I live in a steady seeing area, for me that giving me confidence to have good results and visual, in fact planets mainly Jupiter and Saturn and Venus are very clear, the moon is clearest, so i really don't know how the seeing you have over there, i am happy with the seeing here, and 20" if it won't give me more than 16" then it won't be less than 16" anyway.

 

Someone mentioned about quartz thin mirror, says it has better thermal equilibrium, so confirm that, and i visual planets with my Mak even up to 600x with nice view, really from the clarity of planets mainly Jupiter i even stopped looking at them, got bored of them, but i know my seeing will never match some areas, i don't care, i want to have whatever i can to use that seeing we have here, and don't forget, the moon is still my favorite target, and i saw images from 20" scopes of the moon, amazing, so my point is telling me that 20" is pointless and it won't give anything good is like telling me a Ferrari is useless in racing because the field isn't good or speed will never go high than another car, but i have to tell you that if i live in a poor seeing condition then even 8" will be like the most i can use, if it is average then 12" can be likely the limit and 14" will be very squeezing, but if it is good to excellent then i swear that even 18" can be mind blowing, so 20" isn't too much far, why i limit myself to 20" if the conditions or environment can help, i said because i got some evidence that seeing in my country can help to go up to 18" without issues, so i want to gamble with 20".

 

For this topic, ideal planetary scope sounds an answer with some conditions, not a straight forward, OP is living in Ohio, i don't know how is the seeing there, but i assume it just be good for mostly 12"-14", so that going with 10"-12" as he mentioned is just right, but my seeing is better than Ohio, if he is fine with 10"-14" there then i can be fine with 14"-18" here, i will not say we have super clear amazing seeing full year, but definitely many nights, maybe i am too much exaggerated, but i saw people using for example 14" under non ideal conditions with very very nice results, and i also saw images from 16" under good seeing will not say excellent also with nice results, but here it is, i also saw images from 20" that is no less than 14" or 16", not too much better, but not less then mind blowing, i saw crap bad images from all those scopes or even from 1 meter, this is not a standard, the standard is what a 10" capable or or 20" or 30" capable of in different seeing conditions, i am thinking to talk with a prince if he can give me a land on a high altitude Hill in the state of my country, it is not high but the area is almost less civilized, less light pollution than my city, so maybe that area will put the scope in use, i will trust or believe someone in my country told me that they were able to see Uranus in details or at best with 18" Dob, i did read someone has 18" Dob in UAE, i am sure he is smart enough to go with that size if it is pointless.

[TareqPhoto]

I was really thinking about adding 12" reflector [Newt or Dob] after that 20", it is a nice size, i saw planetary images from 12" surprisingly very good similar to 14" SCT, but i won't stop that 20" plan, by the way, Newt or Dob of 20" i am thinking to go with F4 version, i think this is enough to make things better, there is F3.5-F3.8 versions i think, but F4 is like a good focal ratio of 20" for both visual and imaging, bright enough and fast enough, if i will go with 10" or 12" then i will choose F5, but i see some using F6 or F8 ones too with good news, but i will use Powermate 5x and maybe adding 4x later, so i have to make sure i have fast enough scope/mirror so it won't over [or under?] sample with 4x/5x too much.

[Redbetter]

I had an opportunity to get a look through a Takahashi 130/1000 last year.  The owner also had his 20" Obsession f/5 set up next to it, so it was interesting to compare notes.  The Tak was sharp and on a solid high end mount.  I found no faults with the image of Saturn through it.  The seeing was okay, but not great.  He was using more magnification than I would have for conditions, 286x as memory serves, I would have been happier at about 250x, but the image was quite good.

 

I asked the owner how he felt the two scopes compared on planets.  His response was that while he really liked the images through the Tak, it was "still only a 5-inch scope" and the 20" revealed a lot more.  My visual impression was that the contrast around the planet was obviously quite good; quality baffling, etc. matters.   I definitely wouldn't turn one down, but if I was going to 5" and a beefy mount, it would most likely be a backyard scope rather than a traveling scope...the latter role is occupied by the 20" and DSO observing.  And if I was going to shell out the substantial investment for a high end 5" refractor and mount to be used in the backyard, I would likely skip 5" and go right to 6" because resolution and image brightness counts a lot for planetary.  

 

While there is much claimed about 10" and larger scopes only revealing more in good or great seeing, I have not found that to be true.   It takes rather poor seeing to undo the advantages of aperture with decent optics.  And when the seeing is that poor there is not much point in observing planets anyway because the 80 & 100mm class scopes are suffering to some degree as well.  When I am finding that I am stuck at  a miserable looking 156x with the 20", a quick survey through other scopes reveals they are also stuck in the 150x or less range because of the seeing.  The flip side is that if I am observing with the 110 frac or 127 Mak and things are sharpening enough that they are near topping out, then I really want to get the 10" or 20" pointed at the planet.

 

Last June in good but not great seeing I noticed I was catching the polar storm on Saturn with the 20".  This happened on more than one night during DSO sessions, with different orientations and impressions of the shape.  Images from the period confirmed that I wasn't imagining things.  I hadn't expected it to be a visual object with the seeing level and had not been looking for it--partly because I had no idea when it would be favorably oriented.  Yet, there it was, subtle, but I couldn't shake it.

[Don H]

My 10" f/6.3 and 12.5" f/5.9 scopes were designed as an attempt to provide good planetary views from my suburban patio, but also to be capable for good DSO performance when I could drive to dark sites. Making the mirrors involved extended polishing times and attention to Foucault test measurements to be as good or better than any other mirror I had made so far. At the time I purchased secondaries that were guaranteed to better than 1/10th wave, but in recent years I upgraded the 10" diagonal to a 1/30th wave from Antares. Both scopes exceeded my expectations for planet views when seeing permits, and they are routinely able to provide wonderful details on DSOs too. I feel like they are able to work well in both regards, which is good for me, since I am not sure I could store another scope of a much longer focal ratio. I also do not want to use a ladder anymore, and these fit the bill on that, too.

 

Back in 1975, I had a Honda 350 that was billed as a good road bike and a scrambler. But I always felt like the design made it not so good for either application. Fortunately, my 2 scopes give me the opposite feeling.

 

The 10 inch is always set up in the family room a few feet from the patio door. Lately it has been getting a lot of time on Jupiter and monitoring the GRS. I like to look for GRS transit times that correspond closely to when the planet is near the meridian. There have been several nights in recent weeks where the image was good at 250x, and even held up nicely at 400. Usually a chance to get out between 9:30p and 1am will find my outside temps very close to the inside temp, around 78 degrees or so. I can take the scope out in 2 trips and view with the eyepiece at a perfect height for seated observations. By the time Jupiter has moved too far to the West, Saturn has risen well in the South and provides a fine nightcap. 

 

There have been times when the 10 and 12.5 have been set up side by side and the 12.5 usually has a slight edge on detail, although it is often very close and they both are putting up quite a bit to enjoy. However, the 12.5 is a bit much to carry out assembled and I opt for the 10 almost all the time these days. So I guess for me the 10 inch f/6.3 is currently my ideal planet scope.

 

 

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[Jeff B]

This 11" F7.2 Newt with a CZ thin quartz primary, 1.75" secondary, 2" FT focuser with OTA by Parallax has proven to be an outstanding planetary scope for here in SW Ohio.  The last several nights have offered up a very rare treat of skies steady enough to show a stable, well defined airy disk.  The views of the Moon , Saturn and Jupiter have been stunning.  Maxing out an 8" aperture is more typical around here so it's a real treat to use this scope any where near its full capacity. 

 

There are several things I look for in a "planetary" newt:

 

1. Decent aperture.  For around here that's 10-12" max

2. Slower focal ratio.  I like F7.  Seems optimum for a smaller secondary, reduced coma and easy to collimate but that's easy only if..

3. The scope has a robust, stable structure that supports both mirrors well with ease of adjustments that stay put no matter where in the sky its pointed.

4. Thinner quartz substrate with at least boundary layer cooling.

5. A driven mount.  When everything is working (collimation, cooling and seeing), I don't want to take my eyes off the image and I want it to stay put.

6. Rotating rings if its riding on a GEM.

7. Excellent control of stray light with flocking, even if it's not really necessary with a planetary scope.  I just like it.

8. A stable focuser and attachment to the OTA that does not sag or flex with a bino-viewer assembly...basically, it stay put and collimated (!)

 

This OTA by Parallax has proven to be entirely up to all of the above tasks.  Yeah it's heavy but it's been outside now, under cover for almost a year and I've only tweaked the primary collimation once with one push/pull screw set a fraction of a turn.  It behaves very much like a good refractor OTA in that way.   Just does its job without need for any special TLC or constant tweaking.  I un-bag it and use it...then bag it back up.

 

Jeff

 

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[CHASLX200]

This 11" F7.2 Newt with a CZ thin quartz primary, 1.75" secondary, 2" FT focuser with OTA by Parallax has proven to be an outstanding planetary scope for here in SW Ohio.  The last several nights have offered up a very rare treat of skies steady enough to show a stable, well defined airy disk.  The views of the Moon , Saturn and Jupiter have been stunning.  Maxing out an 8" aperture is more typical around here so it's a real treat to use this scope any where near its full capacity. 

 

There are several things I look for in a "planetary" newt:

 

1. Decent aperture.  For around here that's 10-12" max

2. Slower focal ratio.  I like F7.  Seems optimum for a smaller secondary, reduced coma and easy to collimate but that's easy only if..

3. The scope has a robust, stable structure that supports both mirrors well with ease of adjustments that stay put no matter where in the sky its pointed.

4. Thinner quartz substrate with at least boundary layer cooling.

5. A driven mount.  When everything is working (collimation, cooling and seeing), I don't want to take my eyes off the image and I want it to stay put.

6. Rotating rings if its riding on a GEM.

7. Excellent control of stray light with flocking, even if it's not really necessary with a planetary scope.  I just like it.

8. A stable focuser and attachment to the OTA that does not sag or flex with a bino-viewer assembly...basically, it stay put and collimated (!)

 

This OTA by Parallax has proven to be entirely up to all of the above tasks.  Yeah it's heavy but it's been outside now, under cover for almost a year and I've only tweaked the primary collimation once with one push/pull screw set a fraction of a turn.  It behaves very much like a good refractor OTA in that way.   Just does its job without need for any special TLC or constant tweaking.  I un-bag it and use it...then bag it back up.

 

Jeff

You would in heaven in my skies with that scope. But it would be ruined within a year left outside where i live.

[TareqPhoto]

You would in heaven in my skies with that scope. But it would be ruined within a year left outside where i live.

Exactly the case here too

[Jeff B]

Yeah, I hear you guys, but does stuff rust or corrode inside your house?  

 

What I'm saying is that if the enclosure that I find acceptable in my environment may not be acceptable in yours, then a different enclosure, suitable to your local conditions, is what you need.  The reference to your house interior shows that such internal conditions are indeed possible where you all live.  Just need to figure out how to make those interior conditions happen on a much smaller, but still workable, scale.  Workable meaning easy of deploy and stow with a "reasonable" cost (and, of course, that's highly subjective).  But I'm sure it's entirely possible.

 

Jeff

[scooke]

Best planetary performance I've ever seen were from my 18"F3.75 with a Stabilite mirror figured by Pegasys, my 14.5"F4.3 Zambuto, and a friend's 16"F5, all Starmasters.  Used 1800x one special night on the 18 and Saturn's rings were like looking at a vinyl record, there were so many fine divisions.  Details on Ganymede were easy that night.  If you have the seeing, thermally controlled-perfectly collimated-quality aperture is everything.

[scooke]

Off topic but another item to view a super high power when you can is observing nebulae inside M33.  It's amazing.

[CHASLX200]

Yeah, I hear you guys, but does stuff rust or corrode inside your house?  

 

What I'm saying is that if the enclosure that I find acceptable in my environment may not be acceptable in yours, then a different enclosure, suitable to your local conditions, is what you need.  The reference to your house interior shows that such internal conditions are indeed possible where you all live.  Just need to figure out how to make those interior conditions happen on a much smaller, but still workable, scale.  Workable meaning easy of deploy and stow with a "reasonable" cost (and, of course, that's highly subjective).  But I'm sure it's entirely possible.

 

Jeff

My tools do anywhere i put them.