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Visual observing: big APO refractor VS. big Dobson

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#176 Jon Isaacs

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Posted 04 December 2020 - 05:46 PM

Undoubtedly for straight visual observation of deep sky objects such as clusters, the large Dob will outperform a smaller refractor.  But the refractors are much better at dealing with poor seeing conditions, are far easier to transport, can be put on equatorial mounts, and will in general give sharper views, which is important for planets.

 

So there I am with my $240 used on Astromart 10 inch Dob splitting doubles beyond the reach of a 175 mm apo...

 

Which one is sharper?

 

Which one is easier to setup on an Equatorial mount?

 

6344666-10 inch Dob on EQ platform.jpg

 

Do you choose a scope because it's better under crappy conditions or do buy a scope because it's better under good to excellent conditions? 

 

Refractor are great because they are handy and require little effort on my part to make them perform their best. Dobs/reflectors are great because with some effort, they can really perform..

 

There's a place for both in my harem. But it's probably 3 hours Dob per 1 hour refractor, even more under dark skies.

 

Jon


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#177 stargazer32864

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Posted 05 December 2020 - 12:49 AM

Me??? I can't make up my mind on which scope to get so I'm just going to start buying them all. I started with a 10" Dob and then I'm going to work my way to a refractor, and then...I can't make up my mind between a SCT or Mak-Cass.

 

~Robin


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#178 Praise.M42

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Posted 05 December 2020 - 06:46 AM

I have a 16 inch truss dobsonian, which I call 'big dob'. I know very well its qualities and limits, but I couldn't comment anything on topic 'cause I didn't have the occasion to observe with a refractor, at least for a considerable time.

 

Until now. 

 

Meet my new APM 152 ED, my first ever refractor. I found a incredible deal and I couldn't skip the opportunity. I'm SO happy grin.gif .

 

 

 

In the next weeks I'll be able to compare the 16" to the apm: it's my first time comparing a big dob and a decent sized refractor. Both instruments represent a mid-to-high quality and price range, with the exception of the dob mirrors which aren't so great... 

 

With the appropriate tweaks and attention to both instruments I'll be able to compare them in their best form.

 

 

 

Based on the opinions on this thread and some basics physics, I don't expect one to be better that the other. They're complementary instruments, both shining in what they do best. I think that trying to find the best overall design is a bit of a meaningless challenge. Nonetheless, this thread can be massively helpful to understand the different characteristics and peculiarities of two of the most important and relevant optical design in visual astronomy, especially for beginners. 

 

 

 

I'll keep you updated, and clear skies grin.gif

 

PraiseM42

Well, here I am!

 

I took some time to thoroughly evaluate my APM 152 and, long story short... I love it!

But let's remain on topic and confront my previous reflectors (10 inch and 16 inch commercial dobs with GSO optics, 300$ used and 1500$ used respectively) with the refractor rig (APM + neq6 rowan belt mod, 2800$ used)

 

Disclaimer: I'm no optic expert, and not very experienced with star testing neither. But I'm relatively young (with very good eyesight) and totally new and unbiased in the world of refractor. So it could be interesting. Hope it helps!

So here we go:

 

Mechanics:

The APM wins hands down. The tube, the dew shield, the paint, the rings and handle, the focuser... All are excellent, with a very very high perceived quality and smooth movements. It's also surprisingly light for a 6 inch refractor.

 

The 10 inch Gso commercial structure was a bit rough, but it had a decent 2 inch focuser and good stability. Couldn't expect more for 300$. The base was sooo heavy tho.

 

The 16 inch had GSO optics but a well thought structure made by the Italian Rp-Astro. I suggest you read my thread "Saying goodbye to the big dob" for more info. It was surely good and innovative, with smooth movements, but not on par with the APM quality.

 

Acclimatation time:

Fall and winter temperature is surely not so mild here were I live: during the day it settles down around 6-10 °C, dropping to 0-2 °C during the night. My telescopes are stored inside so they have to adapt to a decent thermal jump.

 

The APM 152 takes 30 minutes to be acceptable to look through, and a full hour to be perfect for high res work.

 

The 10 inch dob (with the stock rear fan on) took no more than 15 minutes to be acceptable to look through, and 30 minutes circa to be ready for high res work.

 

The 16 inch dob (with the stock rear fan on) took about 20 minutes to be acceptable to look through, and a full 40-to-60 minutes to be ready for high res.

 

A clear win for the simple tube 10 inch dob.

 

Star test:

Seeing is not so good for the very majority of fall nights here... But some nights it turns out surprisingly good, and these are the nights to star test my optics. Always use Polaris.

 

The APM 152 has a very good star test. Very little chromatic aberration intra and out focus, with perfect visual correction in focus. No astigmatism at all, and no zonal errors. There's a bit of spherical aberration: I can't tell you how much, but surely no more than 1/6 wave. Not a textbook-magical-takahashi-perfect star test, but I'm very satisfied.

 

The 10 inch GSO tube dob turned out a surprisingly good star test. A small bit of spherical, but no turned edge, no astigmatism, no zonal errors, and also surprisingly smooth optics. When properly collimated it was a killer scope.

The 16 inch truss dob with GSO optics... Was surely not good. Considerable amount of spherical (1/4 wave at least), a bit of turned edge and also a bit of astigmatism. At least not so rough surfaces. Not unacceptable optics, but surely not so good...

 

What I learned: a good refractor with good reputation and manifacturing has a very good chance to have excellent optics. A small commercial mirror can be very good, and it's not so infrequent considering the big amount of food reviews here on CN. with a big commercial mirror... It's a bit of a gamble. You either win or lose, with a good chance of being somewhere in the middle.

 

Large and medium DSOs (emission and reflection nebulae, open clusters and galaxies):

These are my favorite targets to look at from a dark sky. I am so fascinated by them, I always find them beautiful. This also means this is the category I'm more experienced with.

 

The APM 152 is soooo good in relation to its aperture. I didn't expected it to be this good, but I'm surely happy! Light throughput is comparable to a 7-to-8 inch reflector. The large fields and clarity of the view render spectacular open clusters observation. I'm not gonna feed the "diamonds on black velvet" myth, but it's surely good. Nebulas are very defined and contrasty, with a pleasant appearance and good stars, surely not so extended tho. Galaxies are very etched on the background sky, but not so extended and resolved again. In conclusion: very good clarity and contrast in relation to its aperture, pleasant views, but it surely lacks a bit in aperture and resolution.

 

The 10 inch GSO was very good and balanced. Stars were tight and views very good. I couldn't get the extremely large fields I get with the refractor because of the secondary shadow, but it was very good on open clusters: richer fields for sure. Nebulas are more extended and stars very good, with comparable contrast to the APM. Galaxies are surely better than the APM regarding resolution and extension, but they're not easier to identify in the sky. In conclusion: surely better than the APM regarding resolution and extension, but the views are equally pleasant in both, maybe a bit "easier" in the refractor. I'd choose the APM for its larger possible fields without secondary shadow. But let's not forget that I payed 300$ for the dob, more than 9 (9!) times less than the refractor. I got a bit lucky with the 10 inch optics, but the point remains.

 

Here's were the 16 inch dob shines. It's MARVELOUS. It hasn't the very large fields of the refractor but they are so rich that you forget. The double cluster is an explosion of stars. Nebulas are so extended and detailed: despite the not so good optics they're excellent. Galaxies views are a dream. I'll invite you to read my thread on M51 to see how I think the 16 is on galaxies.

 

Small DSOs (globulars and planetary):

The APM has very good contrast and the views are pleasant, but it surely lacks in resolution. Globulars are not magnificent like the ones in the bigger reflectors, despite being good.

 

The 10 inch GSO is very good, with both a good resolution and clarity. Main globulars are resolved at least halfway through, and planetaries start to have easy details.

 

The 16 inch flexes its light gathering capabilities again, with very resolved globulars and planetaries. The not so good optics starts to give "mushy" views at high mah tho, despite not being so noticeable on DSOs.

 

High res (double stars and planets):

The APM has a classic clean view on double stars, with a very pleasant and "surgical" appearance. It hasn't the resolving power larger apertures have, but the stars which can be splitted are marvelous to look at. I can also push high mags with good orthos

 

The 10 inch GSO was also very good, but the prominent diffraction spikes were an obstacles a few times. Despite that, it had clean views, maybe a bit less "surgical" than the refractor ones.

 

The 16 inch had a special secondary spider which rendered 6 very thin spikes, but the optics couldn't keep up with the high mag.

 

I won't say anything regarding planet observation, because planets are very very low here in Italy this year. Maybe I can say that the 10 inch and the APM were good, and the 16 inch surely not, but the atmospheric diffraction was a big obstacle. Based on star tests and double star observation, I think it would be a tie between the 10 inch and the APM, with the APM surely rendering a more pleasant view with my seeing.

 

Lunar:

The APM is very good, with a very balanced white tone and good details. It can be pushed to very high mags and it performs spectaculary, with clinical views and details. Rimae and small craters are easy to discern with good seeing.

The 10 inch is marvelous: the intrinsically very high contrast of the moon mitigates the effects of obstruction and the 10 inch aperture, when there's good seeing, renders spectacular details. I think this is the best instrument I had for lunar observation, despite the APM being very good.

The 16 inch was so bright it forced me to use a filter. The details at low mag was incredibly high, but when I pushed the magnification it all became mushy and less defined. Optics play a very important role in high nag lunar observing.

 

Ease of use:

The APM is not so easy to set up, but when it's all ready it's surely the best regarding ease of use. Goto is a MASSIVE help for me here in a light polluted city, and tracking is so sweet: when you try it you can't go back. With a good chair you can observe for hours.

 

The 10 inch GSO was the easiest to set up: drop the tube in the base and done. It took about 20 seconds. The movements were not so good tho: very sticky friction on both direction, despite a good clean to the bearings, and the focuser was sub-par compared to the APM and even the 16 inch. Also, no tracking and no goto. For 300$ you couldn't expect more tho.

 

The 16 inch was a NIGHTMARE to set up. The mirror box weighs 65lbs, not so good for my back, and the truss process took at least 20 minutes. The movements were good tho, and there was zero flexure and consequently zero miscollimation. The focuser was a simple dual speed crayford but it did a decent job. No goto and no tracking as the 10 inch.

 

CONCLUSION:

Reading the entire review you can easily discern I globally liked the 10 inch and the APM more: the two instruments trade blows on everything, with the APM slightly pulling ahead on optical quality but the 10 inch doing the same on light gathering. It's a very good news for everyone: a fantastic instrument can be obtained for a very appealing price! It's the same old story: to obtain the last 10% optical greatness you have to pay big money. The 16 inch was a fantastic performer on DSO and light gathering work, but it was a one trick pony: you surely have to be lucky, or pay more, to have an all around capable 16 inch.

 

But... Let's bust some false myths (with a bit of irony):

 

"Comparable quality reflectors are 10 times cheaper than refractors, you are so d*mb to think buying a refractor is good". Optically? If you're lucky, it can be true. But you have to be lucky, or you have to be prepared to spend more for a premium mirror. Basic reflectors also lack tracking and goto. If you want that, you either have to use a eq-platform and dsc or something like Servocat. The first option is cheaper (but good eq platform are not so cheap), the second more capable but pricier. There's also the option to eq-mount a newt, but not all people find that manageable without rotating rings and a good mount. Summing up: a reflector is surely cheaper, by if you want all the feature that good refractors and mount have, you have to pay more than what you think, unless being lucky on the used market.

"your puny refractor can't se mag 200000 galaxies and you can't see colors in nebulae. It's useless". It's totally true, but it's not all of the story. I learned that with the 16 inch: to have an all around big reflector you have to pay considerably higher than what you think, especially if you don't want to use a ladder. It's true: at a given price, a reflector will be surely better regarding resolution and light gathering, with maybe comparable optical quality, but it will lack in certain compartments (very large fov for example). It's not always all about "who wins". They're different instruments for different needs.

"Refractor are the best. You can have your mushy and grey view. I always have diamond-on-black-velvet views and you gonna have the clarity of a dusted plastic lens". This is also entirely not true. Refractor are not magical, they won't magically gather more light at a given aperture, and a well thought reflector can easily outperform them, even at a lower price. They're fantastic instrument, but they lack in some compartments. 

 

In conclusion: I love my refractor. It a fantastic instrument, easily the best I've ever had. But I had to pay hard cash for it, that's for sure. A good reflector, with good mechanics and good optics, will outperforms it in many compartments at a given price, or even less, but it would lack other characteristic qualities that refractor have. This is a hobby for the majority of us: we can search for new objects and study variable stars, but we don't have to. We can choose the views and objects we like the most and buy a instrument accordingly. Nowadays we have thousands of instruments to choose from, and in every category there's a fantastic performer for a good price: big 6 inch ED refractors, good mirrors at a lower price, the famous 180 maksutovs, celestron and Meade quality higher than ever, and a myriad of other optical designs. I like newts and refractors the most, but I love the wide choice there's nowadays. It's the right thing to advise someone on the right instrument for their needs, but let's remember there's no magical one. And if we love the sky in its entire mess, we can have more than one scope without breaking the bank. Isn't that beautiful? 

 

Praise.M42


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#179 Echolight

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Posted 05 December 2020 - 10:35 AM

Me??? I can't make up my mind on which scope to get so I'm just going to start buying them all. I started with a 10" Dob and then I'm going to work my way to a refractor, and then...I can't make up my mind between a SCT or Mak-Cass.

 

~Robin

That's the spirit!

 

I'm considering my third refractor, an ST120. And am hoping a decent size used dob comes along some day through the local classifieds.



#180 weis14

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Posted 05 December 2020 - 02:24 PM

Looks sturdy and very much to the point. There doesn't seem to be a provision for encoders, which I do use on my alt-az (not every time, but often).

I actually do deep sky with my refractors, even the small ones, the computer is a boon.

Greg N


Astro Devices makes an encoder kit for the M2C, which I have on mine. The encoders fit inside the housing.

#181 stargazer32864

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Posted 05 December 2020 - 03:33 PM

That's the spirit!

 

I'm considering my third refractor, an ST120. And am hoping a decent size used dob comes along some day through the local classifieds.

After I get my nephew's scope paid for, I'm going to start saving for the new refractor that Astronomics put out. It sounds like a good buy.

 

~Robin



#182 Tyson M

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Posted 05 December 2020 - 04:49 PM

I'm jealous of your temperature swings, mine can be a lot more than 0-2C haha.

The APM 152 seems like a fantastic bargain relatively speaking when one talks about a 6" refractor.

Same can be said about a 10" dob. Especially a preowned one can be picked up for a song.

#183 BillP

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Posted 05 December 2020 - 07:01 PM

These discussions are always so humorous with it running the range from a scope is better if it can see dimmer things (mirrors) to what makes it best of versatility from wide fields to planetary (refractors).  In truth, as far as I'm concerned is that none of that makes a good instrument or a best instrument.  Indeed, what really make an instrument best is the one that you find you take out the most, is most intuitive for you, is not a hassle to get ready but more like a friend in the field.  So basically, it is the scope that you personally like to be with more than any other scope.  That can be a 60mm achromat or a 30" fast Dob.  So for the person who enjoys the night sky with a little 60mm, then that aperture is better in every way than the 30" cow.  Conversely, if for the person who enjoys the night sky with a mammoth 30" cannon, then that aperture is better in every way than a 60mm pea shooter.  So aperture means nothing, the observer's personal likes means everything.

 

ps - Nothing better than my 4" Apo grin.gif  Nothing!


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#184 CHASLX200

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Posted 05 December 2020 - 07:09 PM

So there I am with my $240 used on Astromart 10 inch Dob splitting doubles beyond the reach of a 175 mm apo...

 

Which one is sharper?

 

Which one is easier to setup on an Equatorial mount?

 

 

 

Do you choose a scope because it's better under crappy conditions or do buy a scope because it's better under good to excellent conditions? 

 

Refractor are great because they are handy and require little effort on my part to make them perform their best. Dobs/reflectors are great because with some effort, they can really perform..

 

There's a place for both in my harem. But it's probably 3 hours Dob per 1 hour refractor, even more under dark skies.

 

Jon

The Newts beats the APO in every way if it has Zambuto like optics. The Newt is 30 times cheaper and 5 times lighter. Once you go 7" or more for a APO you are talking 20k and up and big money for a mount. I would much rather have a 8" F/8 Newt over a 8" APO even for free. Since setting up a APO that big would be a 6 to 7 trips scope to set up.  While i can leave a old EQ mount outside and just throw the Newt OTA on the mount and be viewing in 3 mins time.


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#185 tom_fowler

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Posted 05 December 2020 - 08:25 PM

Regarding Jon's post, I agree that a large Newt or Dob will outperform a smaller APO under the right conditions.  But for many of us, the "right conditions" aren't available in our backyard.  The ease of transporting a modest size APO (152mm or less) to a dark sky site is a significant factor--I personally don't like to lift more than 20 lbs.  On top of that, let me say that a premium APO (TEC, LZOS, etc.) is in a whole different class with respect to capability than the cheap Chinese models currently flooding the market--I know, I've compared them, like the difference between a BMW and a Kio Rio.  Expensive-yes, but after 60 or so years of observing, I think that they're worth it.  Plus, with an inexpensive EAA setup (DSLR, tablet, autoguiding), the "small" APO will give DSO images far superior to anything you can see in even a large Newt or Dob.  So you can reasonably trade time for aperture.  Here's an example taken with a 115mm APM/LZOS.

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#186 Jon Isaacs

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Posted 05 December 2020 - 08:37 PM

And if we love the sky in its entire mess, we can have more than one scope without breaking the bank. Isn't that beautiful?

 

Praise M42:

 

An excellent review/comparison that is very much in agreement with my experiences excepting maybe my larger Dobs may have better optics. 

 

Also, Dobs require more attention if one wants to them to perform their best.

 

Jon


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#187 Jon Isaacs

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Posted 05 December 2020 - 09:03 PM

Regarding Jon's post, I agree that a large Newt or Dob will outperform a smaller APO under the right conditions.  But for many of us, the "right conditions" aren't available in our backyard.  The ease of transporting a modest size APO (152mm or less) to a dark sky site is a significant factor--I personally don't like to lift more than 20 lbs.  On top of that, let me say that a premium APO (TEC, LZOS, etc.) is in a whole different class with respect to capability than the cheap Chinese models currently flooding the market--I know, I've compared them, like the difference between a BMW and a Kio Rio.  Expensive-yes, but after 60 or so years of observing, I think that they're worth it.  Plus, with an inexpensive EAA setup (DSLR, tablet, autoguiding), the "small" APO will give DSO images far superior to anything you can see in even a large Newt or Dob.  So you can reasonably trade time for aperture.  Here's an example taken with a 115mm APM/LZOS.

 

A few thoughts:

 

-  I have to admit I'm fortunate. The seeing from my backyard is often very good so I'm able to exploit the advantages of a large aperture telescope. And too, I'm 72 years old but lifting a 50 lb mirror box and hoisting it 5 feet into the motor home's over head bunk is doable. And most of the time I do my dark sky observing from our place in the high desert. Setting up the 22 inch means removing the cover, attaching the wheel barrow handles and wheeling it out.. its a 5 minute job. This year, despite the smoke, it's looking like another 180 nights of observing. Thats probably above average.

 

- Capability..  I have some experience with a variety of refractors.  Todays Chinese refractors are competent, they'll split Dawes limit doubles. They're all limited primarily by their apertures. Its not a Kia versus a BMW.. It might be a Ford versus a Toyota. ((Toyota's are better built than BMWs)

 

- DSO images are available on the internet. I am out there to see the light from the object in the eyepiece.. 

 

Jon


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#188 bobhen

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Posted 06 December 2020 - 07:46 AM

 Todays Chinese refractors are competent, they'll split Dawes limit doubles. They're all limited primarily by their apertures. Its not a Kia versus a BMW.. It might be a Ford versus a Toyota. ((Toyota's are better built than BMWs)

 

- DSO images are available on the internet. I am out there to see the light from the object in the eyepiece.. 

 

Jon

True, images are available on the Internet. But they are not YOUR images.

 

If you travel to the Grand Canyon do you not take pictures because there are pictures of the Grand Canyon on the Internet? Would you put Internet images of your trip to the Grand Canyon in a family photo album?

 

The images that one records of the Canyon or of the sky are not just images they are personal reminders of the experience and the emotional reward/impact of that experience.

 

In addition, real-time Night Vision observing with an intensifier or very short exposure EAA imaging will surpass the detail that is seen in larger aperture telescopes. And those images/observations will be different than the long exposure images on the Internet and they will be your images and your observations.

 

Today (it is 2020 not 1985), if one seeks more light gathering and the corresponding detail in deep sky objects that more light gathering delivers; there are alternatives to bulky, large mirror telescopes that require dark skies.

 

PS: It is interesting to note that when Toyota wanted to produce a high-end sports car like the Supra they went to BMW for the engine, drivetrain and most of the internal components right down to the door chimes. Build quality between Toyota and BMW “might” be arguable but performance is not – and the same with refractors. As an owner of both BMW and Toyota and of a few high-end and value-priced refractors that is my experience anyway.

 

Bob


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#189 Echolight

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Posted 06 December 2020 - 10:27 AM

For now, I'll take the natural to my eye blues, blacks, grays, and whites of the sky (along with the colored stars and planets) to the unnaturally brighter greens.


Edited by Echolight, 06 December 2020 - 10:30 AM.

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#190 tom_fowler

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Posted 06 December 2020 - 10:52 AM

Sounds like this discussion is more about individual preferences than instrument capabilities!  If you want the best experience at the eyepiece, especially for DSOs, then clearly a big Dob or Newt is the ticket, though the laws of optics and the size of the human eye will limit what can be seen regardless of scope size (see my book "The View Through Your Telescope" for a detailed discussion).  For good imaging, in general a GEM is going to be needed, and that will imply a smaller scope.  High-end APOs sell and have long waiting lists because they can do many things well, and really do punch above their size in many respects, though they can't overcome the laws of physics.  As many have noted, if space and resources permit, one of both is a good solution. 


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#191 hoof

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Posted 06 December 2020 - 12:31 PM

An APM 152 taking 30 minutes to acclimate? Take a page from the Cat folks and wrap that thing in Reflectix! Then zero acclimation time needed :)

My Intes MN66 is ready for high power view (assuming seeing is good) as soon as I put it on my altaz mount and put an eyepiece in it. Wrapping it a few years back turned it from once-in-a-blue-moon usage (due to cooling) to my main ‘scope, because of this elimination of wait time, with no degradation in image quality (best I can tell). If your APO has acclimation issues, wrapping the tube with reflectix should eliminate that :)

#192 Echolight

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Posted 06 December 2020 - 01:32 PM

Sounds like this discussion is more about individual preferences than instrument capabilities!  If you want the best experience at the eyepiece, especially for DSOs, then clearly a big Dob or Newt is the ticket, though the laws of optics and the size of the human eye will limit what can be seen regardless of scope size (see my book "The View Through Your Telescope" for a detailed discussion).  For good imaging, in general a GEM is going to be needed, and that will imply a smaller scope.  High-end APOs sell and have long waiting lists because they can do many things well, and really do punch above their size in many respects, though they can't overcome the laws of physics.  As many have noted, if space and resources permit, one of both is a good solution. 

Both? Genius!



#193 Astrojensen

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Posted 06 December 2020 - 01:58 PM

An APM 152 taking 30 minutes to acclimate? Take a page from the Cat folks and wrap that thing in Reflectix! Then zero acclimation time needed smile.gif

My Intes MN66 is ready for high power view (assuming seeing is good) as soon as I put it on my altaz mount and put an eyepiece in it. Wrapping it a few years back turned it from once-in-a-blue-moon usage (due to cooling) to my main ‘scope, because of this elimination of wait time, with no degradation in image quality (best I can tell). If your APO has acclimation issues, wrapping the tube with reflectix should eliminate that smile.gif

This is absolutely, fundamentally wrong. 

 

The problem with refractors is NOT tube currents or boundary layers, as it is in a reflector, the problem is that the front and rear lens(es) cool unequally and this introduces spherical aberration, spherochromatism and, to a small degree, chromatic aberration. 

 

These problems aren't alleviated by insulating the tube, but quite the contrary, because this will slow the cooling of the innermost lens element even more, relative to the front lens. The two (or three) lenses will need to be within a few degrees of each other or else the actual lens curve matching will deviate too much from the design. 

 

This is not a problem in an SCT or a maksutov, where the front corrector plate/lens has very weak optical power. Thus, what works beautifully on one scope can be an outright disaster on another. 

 

 

Clear skies!

Thomas, Denmark 


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#194 bobhen

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Posted 06 December 2020 - 02:19 PM

Sounds like this discussion is more about individual preferences than instrument capabilities!  If you want the best experience at the eyepiece, especially for DSOs, then clearly a big Dob or Newt is the ticket, though the laws of optics and the size of the human eye will limit what can be seen regardless of scope size (see my book "The View Through Your Telescope" for a detailed discussion).  For good imaging, in general a GEM is going to be needed, and that will imply a smaller scope.  High-end APOs sell and have long waiting lists because they can do many things well, and really do punch above their size in many respects, though they can't overcome the laws of physics.  As many have noted, if space and resources permit, one of both is a good solution. 

 

Sounds like this discussion is more about individual preferences than instrument capabilities!  If you want the best experience at the eyepiece, especially for DSOs, then clearly a big Dob or Newt is the ticket, though the laws of optics and the size of the human eye will limit what can be seen regardless of scope size (see my book "The View Through Your Telescope" for a detailed discussion).  For good imaging, in general a GEM is going to be needed, and that will imply a smaller scope.  High-end APOs sell and have long waiting lists because they can do many things well, and really do punch above their size in many respects, though they can't overcome the laws of physics.  As many have noted, if space and resources permit, one of both is a good solution. 

The best real-time, deep sky experiences I’ve had “at the eyepiece” is with 8” and smaller telescopes when used with an image intensifier – and before I purchased the intensifier, I used to have a 15” Dobsonian that I used visually with regular glass eyepieces.

 

If you want to count short exposure EAA, then the best experience at the telescope (but on a screen not an eyepiece) was with my C11 and astro-video camera.

 

Both of the above outperformed (by outperform I mean showed deep sky objects that were invisible or showed more detail in objects) then the 15” Dobsonian did when used visually – and by a lot.

 

There is, of course, nothing wrong with visual observing, but if the goal is to see detail in deep sky objects, then these other methods incorporating today’s newer technologies are the better alternative.

 

Those alternatives also eliminate the large Dobsonian’s advantage of light gathering capability, making the refractor the better all-round and more versatile choice – and eliminating the need for the two telescope solution.

 

Bob


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#195 bobhen

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Posted 06 December 2020 - 02:22 PM

For now, I'll take the natural to my eye blues, blacks, grays, and whites of the sky (along with the colored stars and planets) to the unnaturally brighter greens.

If by green you are talking about Night Vision observing, today there are intensifiers that do not have a green cast. Intensifiers are, of course, not for lunar and planetary observing.

 

Bob



#196 Jon Isaacs

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Posted 07 December 2020 - 06:43 AM

True, images are available on the Internet. But they are not YOUR images.

 

If you travel to the Grand Canyon do you not take pictures because there are pictures of the Grand Canyon on the Internet? Would you put Internet images of your trip to the Grand Canyon in a family photo album?

 

The images that one records of the Canyon or of the sky are not just images they are personal reminders of the experience and the emotional reward/impact of that experience.

 

I am so glad you mentioned the Grand Canyon.  It is really a great example.

 

My wife and I frequently travel to the dark skies of the Navajo reservation and with our senior passes, drive through the Grand Canyon on our way.  Sometimes we will camp there and then spend an entire day parked in our motor home at one of the overlooks and just spend the day watching the changes in the canyon throughout the day.

 

As we are observing the canyon, cars and buses loaded with tourist show up,typically spend about 15 minutes, mostly taking photos, most often of themselves with their friends and then they leave.  

 

Yes, those photos are their photos but they were never really there, they never really looked at the canyon, they never really observed the many facets of the canyon, they never really experienced the subtle colors and the wild life and the changes.  

 

When you are imaging you are not observing.  When you are using an image intensifier you are not experiencing the light, the darkness, the actual star colors.  

 

I am not saying one is better than the other, rather just saying they are different experiences.  And I will say that I much prefer the visual experience of looking through an eyepiece.  

 

Maybe someday, I will no longer be able to spend two weeks a month under dark skies observing the way I love observing.  At that point, I may find some sort of EAA is in the cards.  But for now, I think I have it pretty darn good.  I can have the 22 inch setup in about 5 minutes, be observing in 10 minutes.  It takes me longer to put my eyepieces away than it does the telescope.. 

 

Jon


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#197 BbasAlnitak

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Posted 07 December 2020 - 07:32 AM

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#198 BbasAlnitak

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Posted 07 December 2020 - 07:33 AM

I am so glad you mentioned the Grand Canyon.  It is really a great example.

 

My wife and I frequently travel to the dark skies of the Navajo reservation and with our senior passes, drive through the Grand Canyon on our way.  Sometimes we will camp there and then spend an entire day parked in our motor home at one of the overlooks and just spend the day watching the changes in the canyon throughout the day.

 

As we are observing the canyon, cars and buses loaded with tourist show up,typically spend about 15 minutes, mostly taking photos, most often of themselves with their friends and then they leave.  

 

Yes, those photos are their photos but they were never really there, they never really looked at the canyon, they never really observed the many facets of the canyon, they never really experienced the subtle colors and the wild life and the changes.  

 

When you are imaging you are not observing.  When you are using an image intensifier you are not experiencing the light, the darkness, the actual star colors.  

 

I am not saying one is better than the other, rather just saying they are different experiences.  And I will say that I much prefer the visual experience of looking through an eyepiece.  

 

Maybe someday, I will no longer be able to spend two weeks a month under dark skies observing the way I love observing.  At that point, I may find some sort of EAA is in the cards.  But for now, I think I have it pretty darn good.  I can have the 22 inch setup in about 5 minutes, be observing in 10 minutes.  It takes me longer to put my eyepieces away than it does the telescope.. 

 

Jon

 

Jon

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#199 bobhen

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Posted 07 December 2020 - 07:45 AM

I am so glad you mentioned the Grand Canyon.  It is really a great example.

 

My wife and I frequently travel to the dark skies of the Navajo reservation and with our senior passes, drive through the Grand Canyon on our way.  Sometimes we will camp there and then spend an entire day parked in our motor home at one of the overlooks and just spend the day watching the changes in the canyon throughout the day.

 

As we are observing the canyon, cars and buses loaded with tourist show up,typically spend about 15 minutes, mostly taking photos, most often of themselves with their friends and then they leave.  

 

Yes, those photos are their photos but they were never really there, they never really looked at the canyon, they never really observed the many facets of the canyon, they never really experienced the subtle colors and the wild life and the changes.  

 

When you are imaging you are not observing.  When you are using an image intensifier you are not experiencing the light, the darkness, the actual star colors.  

 

I am not saying one is better than the other, rather just saying they are different experiences.  And I will say that I much prefer the visual experience of looking through an eyepiece.  

 

Maybe someday, I will no longer be able to spend two weeks a month under dark skies observing the way I love observing.  At that point, I may find some sort of EAA is in the cards.  But for now, I think I have it pretty darn good.  I can have the 22 inch setup in about 5 minutes, be observing in 10 minutes.  It takes me longer to put my eyepieces away than it does the telescope.. 

 

Jon

 

Jon

Comparing snapshot tourists or bad photographers to your experience is a false argument.

 

I believe that a National Geographic photographer or someone like Ansel Adams had an excellent feel for the location and a deep knowledge and understanding of the landscape and spent many days and nights in a location before capturing the perfect image.

 

It is true that using an monochromatic intensifier you do sacrifice star colors but it is also true that using a mirror, even a large mirror, you are sacrificing seeing many deep sky objects or sacrificing seeing more details in those deep sky objects. I’ll take that tradeoff any day.

 

One needs to ask what is better a perfectly natural view of the stars in the field and nothing else or now, in the exact same field but using an intensifier, the Horsehead Nebula now becomes easily observed. And not as just as a hard to see notch but with the Horsehead outline and the background nebula so extensive that it extends out of the field of view. And that observation can be accomplished with telescopes as small as from around 100mm – 120mm and in real-time and in light pollution.

 

Different experiences do not mean equal experiences. I would argue that the advantages offered by today’s technology FAR outweigh the advantages of yesteryear. One can still photograph using film and some might still find that experience enjoyable but the overwhelming majority of photographers now use digital technology because of the many advantages that technology offers. I’m guessing that you do not use film or have a dial phone or a typewriter. Using a large mirror to gather light also falls in that category. Sure, it can still be enjoyable, but if the goal is to see more (which is why many have large mirrors in the first place) then there are better, not just different but better, alternatives.

 

Bob


Edited by bobhen, 07 December 2020 - 07:49 AM.

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#200 Jon Isaacs

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Posted 07 December 2020 - 08:39 AM

Different experiences do not mean equal experiences..

 

 

Bob:

 

Exactly.  What experience are you looking for, what are your priorities?  What is the experience I am looking for, what are my priorities? 

 

This is hobby, something I do because I enjoy it.  I get it that you live in Pennsylvania without easy access to dark skies and clear nights. 

 

I am in a much different situation.  I am doing this thing the way I want to. As a friend said, "You are living the dream." It's not about counting objects seen..  That's not what it's about. 

 

I go for a bicycle ride.  I enjoy it.  There's a hill ahead, it's a challenge, I crest the hill and I have met that challenge.  Now I could put a motor on my bicycle but that would have been a very different experience.  I would not have experienced the hill in the same way as I did climbing it on my bicycle. 

 

I do think the Grand Canyon tourists are very relevant.  They are experiencing the canyon through digital cameras and not really taking the time to observe.  They want it quick and easy.  

 

In my work in a research lab, I used a high speed framing camera that was based on image intensifying technology.  It cost approximately $300,000 and at the time, it was the fastest single shot camera in the world.  It was capable of taking 16 images, one every 5 nano-seconds with "shutter speed" of 5 nanoseconds.  To realize just how fast that is, a beam of light travels 1.5 meters in 5 nanoseconds.  

 

We were not imaging at that speed, usually somewhere around 1 microsecond per image with maybe 50-100 nanoseconds exposures.  You need a lot of light and image intensification was the only way to get it.  This was research, we were taking images of ballistic events that was on the leading edge that led to new understandings.  That was my job.. We took some amazing videos/images.  

 

This is my hobby.  It's fun, satisfying, it touches something deep inside. Looking through a 22 inch or a 16 inch 5 inch or a 3 inch telescope, it's an amazing experience, I can't get enough of it. This year, I will have spent something like 180 nights observing, probably 500-600 hours at the eyepiece. It's not just the deep sky, it's the planets, double stars, comets, the whole shebang.  There's magic there.      

Others might be bored or disappointed with what they see through the eyepiece but I am not.  I am thrilled.  

 

Jon


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