24 replies to this topic

[saemark30]

I am interested in a planetary observations and the scope that I am interested is the SW 180mm F/15 Maks but I have not looked thru one. 

I find my long focus 6" Newtonian with small secondary will outdo a 6" Intes Mak but I am looking for even more detail on Jupiter and Mars.

 

Would a SW 7" Mak be much better on planetary detail/sharpness?

 

And what about comparison to the new  SW 150mm F/8 ED refractor? 

I have read good reports that they are well made thought chromatic aberration would limit the performance.

 

In theory a larger Newtonian/dob should equal or surpass the 7" Mak or SW 6" ED refractor.

If I was to make a dob should it be 8" or 10" aperture?

[areyoukiddingme]

Having tried a 6" apo (the Explore Scientific), I can say that while they are nice, you will see more in a 10" reflector for sure, unless there are significant optical defects or the cooling/collimationg are bad (both fixable, at least).

 

If an 8" reflector is optimized, it's going to be hard to find a 6" refractor that will beat it on the planets. For 10", no competition.

[siriusandthepup]

 

If an 8" reflector is optimized, it's going to be hard to find a 6" refractor that will beat it on the planets. For 10", no competition.

True words.

 

At a star party I attended, two friends had their scopes set up side by side. Seeing was decent and both scopes were pointed almost straight up at Jupiter. One scope was a 6" f/15 Jaegers achromat and the view was very nice and crisp. I saw nothing to fault the view. Nice! The other scope was an 8" f/6 Starfinder Dob. This scope had been "tuned up" with a high spec replacement secondary, minor tweaks and the original primary. Case closed - no need to run back and forth - the view was better in the Dob. Better brightness (expected), but more detail too. Beautiful!

 

From my own perspective, I once owned an 8" F/12 achromat and it gave nice planetary views. Side by side with my 10" f/5, plate glass primary Dob - no contest - 10" wins over the 8".

 

All the scopes in these comparisons had good optics - there weren't any dogs in the race.

 

You want to kill Mars? Better hurry up, it's coming! Build yourself a 10" Dob with great optics.

 

Here is one (if still available) from our own CN classifieds. Royce 10" f6 with Moonlight focuser diagonal rings

 

Bargain for what's included.

[SteveG]

A well built 10" Newt with good optics simply cannot be beat.

[astroneil]

Having tried a 6" apo (the Explore Scientific), I can say that while they are nice, you will see more in a 10" reflector for sure, unless there are significant optical defects or the cooling/collimationg are bad (both fixable, at least).

 

If an 8" reflector is optimized, it's going to be hard to find a 6" refractor that will beat it on the planets. For 10", no competition.

Yep, that's generally been my experience as well. 

[astroneil]

True words.

 

At a star party I attended, two friends had their scopes set up side by side. Seeing was decent and both scopes were pointed almost straight up at Jupiter. One scope was a 6" f/15 Jaegers achromat and the view was very nice and crisp. I saw nothing to fault the view. Nice! The other scope was an 8" f/6 Starfinder Dob. This scope had been "tuned up" with a high spec replacement secondary, minor tweaks and the original primary. Case closed - no need to run back and forth - the view was better in the Dob. Better brightness (expected), but more detail too. Beautiful!

 

From my own perspective, I once owned an 8" F/12 achromat and it gave nice planetary views. Side by side with my 10" f/5, plate glass primary Dob - no contest - 10" wins over the 8".

 

All the scopes in these comparisons had good optics - there weren't any dogs in the race.

 

You want to kill Mars? Better hurry up, it's coming! Build yourself a 10" Dob with great optics.

 

Here is one (if still available) from our own CN classifieds. Royce 10" f6 with Moonlight focuser diagonal rings

 

Bargain for what's included.

Spot on!!

[Arief M.]

A well built 10" Newt with good optics simply cannot be beat.

Spot on!

[Jon Isaacs]

My two cents:

 

How good is your seeing?  Is your climate a mild one or are the indoor-outdoor temperature differentials significant?

 

Refractors have fewer thermal issues than Newtonians.  A good 10 inch Newtonian should show more detail than a 6 inch ED doublet but the assumptions are that the reflector has stabilized thermally, not necessarily as easy as it sounds, and that the seeing supports the 10 inch.  

 

Jon

[saemark30]

The climate in the summer is relatively mild. By July the temp range average is highs 70's F to low around 50's.

But typically very windy just east of the Rockies.

In October the temperature range average highs in 50's to low of low 30's.

 

How can I determine if seeing supports a 10" Newtonian? I am not in Florida or by the Pacific, more northern midwest and 2/3 mile high. 

[Jon Isaacs]

The climate in the summer is relatively mild. By July the temp range average is highs 70's F to low around 50's.

But typically very windy just east of the Rockies.

In October the temperature range average highs in 50's to low of low 30's.

 

How can I determine if seeing supports a 10" Newtonian? I am not in Florida or by the Pacific, more northern midwest and 2/3 mile high. 

 

Seeing is so local that it has to be evaluated in person to have an idea.  

 

But being on the leeward side of a mountain range with frequent winds does not make for good seeing.  

 

With your current scope, do you spend much time on double stars?  

 

Jon

[Eric63]

My two cents:

How good is your seeing? Is your climate a mild one or are the indoor-outdoor temperature differentials significant?

Refractors have fewer thermal issues than Newtonians. A good 10 inch Newtonian should show more detail than a 6 inch ED doublet but the assumptions are that the reflector has stabilized thermally, not necessarily as easy as it sounds, and that the seeing supports the 10 inch.

Jon

For high power viewing, seeing conditions are everything. Where I live, I find 6" is the max for my typical conditions unless I want to sit for an extended period and catch those fleeting moments of great seeing.

[saemark30]

I am more west of the mountains in the great plains. Lots of grassland.

Not much into double stars. Just common ones like the double-double, Polaris, Rigel.

No luck with Sirius.

I expect July and August to be the best if only months with good weather/seeing though.

[saemark30]

Would a 7" ED doublet refractor be better than a 10" Newtonian or would it be seeing limited as well.

From what you are saying I think I should cross out a Mak 180mm. The night time temperature varies by a couple degrees per hour.

This isn't California.

[areyoukiddingme]

Would a 7" ED doublet refractor be better than a 10" Newtonian or would it be seeing limited as well.

From what you are saying I think I should cross out a Mak 180mm. The night time temperature varies by a couple degrees per hour.

This isn't California.

This thread has put me in mind of a very old but relevant thread (one of my all time favorites):

 

https://www.cloudyni...r-vs-reflector/

 

And btw. viewing in California mountain tops, we can start in the 80s and be in the 30s and below in space of a few hours.

[Illinois]

I have SW150ED and LOVE it! I used 10 inch dobsonian and sold it about 8 years ago. I like refractor better because of sharper pinpoint stars and tight double stars. brighter clear view. That's for me! 10 inch is great and little better for deep sky objects as faint galaxies or faint small nebula than 8 inch and SW150ED. I used to have ES 127 APO and its good until I got my SW150 then I sold ES 127 APO. 10 inch Dobsonian is cheaper, good telescope but need collimation almost every time to make sure that view is sharp. SW150 is big telescope if you don't mind that. I have 180mm Mak Cass and its great for high power. 10mm eyepiece for 270 power but need long time cooling time and not good for quickly grab and go! I put my 180mm MakCass outside two hours before sunset to get ready to look at Jupiter or Saturn at night. Its not good for early morning to get up and take 180 makcass to look at planet right away. I did and view was terrible. No perfect telescopes but good to have two or three telescopes like golf clubs or several fishing poles.

Edited by Illinois, 10 May 2020 - 06:31 AM.

[saemark30]

What about your Meade 16" dob Illinois, do you ever use it for planet viewing?

I really found the thread on Refractors VS Reflectors educational. Perhaps the most important thread ever.

[saemark30]

Seems to me a 16" dob will show more on planets even if the seeing might not be great. There are fleeting moments when seeing should allow it to outperform a 6" F/8 ED APO.

 

From what I have read the SW 6" ED has some color on the moon's terminator and craters. This suggests to me it is on par with an old Meade 6" F/9 ED doublet which used FK01/KF3 glass. This is much better than an achromat but I think it still should have some color looking critically at Jupiter's festoons and white spots and Saturn's ring system. 

[Illinois]

What about your Meade 16" dob Illinois, do you ever use it for planet viewing?
I really found the thread on Refractors VS Reflectors educational. Perhaps the most important thread ever.

Planet viewing in my 16 inch is great during rare good night but super for faint deep sky objects and galaxies! SW150 is great for planetary for most night!

[Bomber Bob]

Seems to me a 16" dob will show more on planets even if the seeing might not be great. There are fleeting moments when seeing should allow it to outperform a 6" F/8 ED APO.

 

From what I have read the SW 6" ED has some color on the moon's terminator and craters. This suggests to me it is on par with an old Meade 6" F/9 ED doublet which used FK01/KF3 glass. This is much better than an achromat but I think it still should have some color looking critically at Jupiter's festoons and white spots and Saturn's ring system. 

My APM 152ED shows no false color on the Moon or planets (except crescent Venus).  It also cost more than the SW150ED.  I'm a Refractor Fan, but...

 

If I were you, I'd get myself the best-quality 8" or 10" Newtonian (+ mount as applicable) that I could afford.  It'll be money well spent, and the views won't disappoint.

[siriusandthepup]

 

My APM 152ED shows no false color on the Moon or planets (except crescent Venus).  It also cost more than the SW150ED.  I'm a Refractor Fan, but...

 

If I were you, I'd get myself the best-quality 8" or 10" Newtonian (+ mount as applicable) that I could afford.  It'll be money well spent, and the views won't disappoint.

That said, and despite what I said in the above post, consider this: A good 6" refractor does much better on deep sky than most give it credit for.

 

I my experience, A 6" APO/ED will do almost as well as a 10" Newt on Deep Sky. Why? Contrast.

 

The point is, that if you own a 6" ED you are not terribly handicapped. Enjoy the pin-pointy stars and micro dust!

 

The 10" Newt will show more on Mars come opposition time - but only when seeing allows and when the mirror is cooled down. Get the Newt - keep the refractor. The refractor will provide many more satisfying observing sessions in variable seeing conditions.

Edited by siriusandthepup, 15 May 2020 - 01:11 PM.

[Bomber Bob]

I am interested in a planetary observations and the scope that I am interested is the SW 180mm F/15 Maks but I have not looked thru one. 

I find my long focus 6" Newtonian with small secondary will outdo a 6" Intes Mak but I am looking for even more detail on Jupiter and Mars.

 

Would a SW 7" Mak be much better on planetary detail/sharpness?

 

And what about comparison to the new  SW 150mm F/8 ED refractor? 

I have read good reports that they are well made thought chromatic aberration would limit the performance.

 

In theory a larger Newtonian/dob should equal or surpass the 7" Mak or SW 6" ED refractor.

If I was to make a dob should it be 8" or 10" aperture?

You're looking for an upgrade from a 6" Newtonian, right?  Primarily for planetary observing?

 

I don't know about the SW 150 F8 ED, but my APM 152 F8 ED has no visible CA -- except possibly on Venus.

 

If your night-time temps aren't too much for it, the SW 180 F15 MCT should be an excellent planetary scope.

 

A well-made 10" Newtonian is about the most cost-effective option in your post.

[25585]

10" F6 refractor, solid tube. Collimation easy. Not too back breaking to move around in 2 pieces, mount & tube.

 

Small MCTs & SCTs restrict you to using 1.25" eyepieces. They also have much narrower fields of view. Their benefit is smaller mounts, a 6" refractor needs a bigger heavier mount.

 

Choosing a GOTO or equatorial tracking platform Dobsonian for planets would be my choice.

[saemark30]

I haven't seen any planetary images taken with the APM 152 F8 ED.

Perhaps a good Jupiter shot would say more than 10000 words.

 

Newtonians are great. Just a matter of if the area will provide good seeing. Based on the typical windy conditions I think it would have to be a solid tube and a fan might not be needed!

[saemark30]

Not much time to build a 10" scope.

How about getting a typical C9.25" or Meade 10" SCT with mirror lock? I would probably get a different answer in the Cass and refractor forums!

 

I think a 6" refractor would gain in less than perfect seeing over a 6" long Newtonian and those China ED scopes are not as well figured. I already use a very high quality Antares diagonal and it takes up to 375x on Jupiter.

A double ED still have some spherochromatism error even if not visible. 

[saemark30]

I found a 10" F5.5 pyrex mirror, how would I find out if it be suitable ?

And same thing for the secondary mirror?

Due to current isolation I am without ability to build an interferometer or Foucault tester or even get a Ronchi screen.

Edited by saemark30, 24 May 2020 - 06:55 PM.