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#176 pstarr

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Posted 16 December 2011 - 08:19 PM

Not so simple. the seeing changes every few seconds unless it's an exceptional night. One scope may have caught a better moment of seeing than another one. All would have to use the same number of frames or only one frame. Taken with the same camera and use the same software to process them. IMO a visual comparison would make more sense than imaging.

#177 Mitchell Duke

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Posted 16 December 2011 - 08:32 PM

Paul that's not totally correct, and this is assuming the scopes are imaging at the same time. Visual will always be subjected to false perception, and will never be true readings. Imaging will show the facts for everyone to see. All that's needed is the same setup at the same magnification at the same time. Besides I don't think the visual people are looking through both scopes at the same time??

#178 azure1961p

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Posted 16 December 2011 - 10:03 PM

Uncle Rod,

Not my experience at all. A wonderful six inch refractor is still a six inch and simply cannot defeat five extra inches of aperture. If nothing else, the way superior light gathering power means you will see more on the planets--light is NOT just important on the deep sky.

A 6-inch refractor can produce a very aesthetically pleasing image, especially under poor seeing. Show as much detail? Uh-uh. Nosir buddy. ;)


I've viewed Jupiter through an 8" f/15 Alvan Clark refractor and was not impressed by the detail. Of course, it wasn't an APO ... but f/15! I could see just as much through my 8" f/6 Newt and much more through my 10" f/4.8 Newt. The seeing was good, 4/5, during the evening with the 8" refractor.

I just don't buy the buzz about 6" refractors - even APOs - being a superior planetary scope in comparison to a good Newt or Cat of larger aperture.

FWIW, my 70mm f/12.9 achro shows a very pleasing image of Jupiter and the Moon, but for fine detail, I'll take out the 6" Mak or a bigger Newt.

Mike


Nice post Mike!

Pete

#179 JJK

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Posted 16 December 2011 - 10:53 PM

Very nice suggestion Duke. And if one were to take that project on, and could do it side by side on the same mount simultaneously, they would be viewing through exactly the same air column, with the same ancillary equipment and at the same time, which would remove all doubt about variances entering in. No excuses or doubt would remain.


Why is this a black and white issue? It should be obvious that each type of instrument has it's strengths and weaknesses, and that the strengths may depend on factors beyond one's control.

Many of you insist that under identical conditions any C11 would always provide a better planetary image compared to a top-end APO. Is it really that hard to believe that seeing conditions, OTA thermal issues, and/or the optical quality of a particular C11 (it must vary, by how much, I'm not sure) could favor the apo on any given night? I've seen 6.1" apos outperform C11s visually (the criteria I use are the greatest magnification that a scope can use productively, the contrast a scope can provide on a target like Jupiter, and the fraction of time the views look good). That doesn't mean this scenario will always be the case, but where I live, it's the norm.

My AP 10" Mak-Cass will surely always outperform a C11 (that's been my experience over the past decade). That doesn't mean the latter has no virtue.

I have a wide range of telescopes in terms of aperture (80mm to 25") as well as types (many apos, a few Mak-Cass OTAs, a Dall-Kirkham, a big Dob-Newt, and Solar H-alpha) and appreciate each of them for their specific capabilities. I also hope to get a C14 someday. Imagine that.

#180 JJK

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Posted 16 December 2011 - 11:27 PM

Paul that's not totally correct, and this is assuming the scopes are imaging at the same time. Visual will always be subjected to false perception, and will never be true readings. Imaging will show the facts for everyone to see. All that's needed is the same setup at the same magnification at the same time. Besides I don't think the visual people are looking through both scopes at the same time??


You raise a valid point in rhe sense that one can't have the same eye in two or more telescopes at a time. However, you neglect the fact that visual observing and imaging are two completely different techniques for at least a couple of reasons. First, the spectral sensivity of a human eye doesn't match that of a CCD detector, and a CCD camera/computer/image/processing combination can overcome mediocre seeing and provide an image we can all see as long as we want, unlike any one of us staring into an EP for tens of minutes to catch a glimpse through a rare parcel of steady air.

You also assume that visual tests are unvalid. There is nothing wrong with judging telescopes with your own eyes, especially if that's how you intend to observe. I trust my own judgment and know that I can be objective about what I see. Even if one scope outperforms another on a given night (based on criteria that relate to how I derive pleasure from this hobby), I understand that result might change under different circumstances.

If a given SCT consistently outperformed my Zeiss and AP apos visually on all the objects I like to look at, and in the time I need the scope to equilibrate, I'd sell my refractors. My experience suggests that isn't going to happen. However, I can easily imagine enjoying the use of a commercial SCT for what it does best.

#181 Sarkikos

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Posted 16 December 2011 - 11:30 PM

whduke,

There is only one way to truely solve this on going issue. Someone with a 6" or 7", and a 11" or 14" SCT needs to image Jupiter on the same night. This side by side comparison will show which scope works best. If anyone has not noticed yet look at the solar system imaging forum. There has to be some reason why everyone is imaging with a Newtonian, or a SCT. Sorry guys sometimes the truth hurts :nonono:


I'm strictly visual, no AP experience. But from what I've read on CN and elsewhere, seen in the imaging forum, and seen with my own eyes through various telescopes, a comparison of digital images will not tell you which will be the better telescope for visual observation of planets. For visual, the individual will just have to go by the experience of other visual observers or better yet, see for themselves.

But, yes, it does seem that the best planetary AP is being done by "moderately-sized" Newts and SCTs.

I'm not certain, but I got the impression that the OP was interested in visual observation, not AP. Personally, my best - meaning most detailed - views of planets have been through moderate-sized Newts, 8" through around 15" or so.

Mike

#182 turtle86

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Posted 16 December 2011 - 11:36 PM

I've viewed Jupiter through an 8" f/15 Alvan Clark refractor and was not impressed by the detail. Of course, it wasn't an APO ... but f/15! I could see just as much through my 8" f/6 Newt and much more through my 10" f/4.8 Newt. The seeing was good, 4/5, during the evening with the 8" refractor.

I just don't buy the buzz about 6" refractors - even APOs - being a superior planetary scope in comparison to a good Newt or Cat of larger aperture.

FWIW, my 70mm f/12.9 achro shows a very pleasing image of Jupiter and the Moon, but for fine detail, I'll take out the 6" Mak or a bigger Newt.

Mike



I don't buy the buzz either. Planetary views are very, very pleasing in premium APO's. But as much as I like the way Saturn looks in an AP APO, I've never been able to convince myself that I actually see more detail in an APO than an SCT of slightly larger aperture--when the seeing is good, my humble 8" SCT does a fine job on planets. So, when I had a chance to buy an AP Gran Turismo APO a couple of years ago, I just couldn't quite bring myself to pull the trigger, even though I had been on the AP notification list for something like 8-10 years.

#183 t.r.

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Posted 17 December 2011 - 08:49 AM

But the 130 Gran Turismo would have made a fine compliment to your larger reflector. I get the impression that people think that these scopes must compete on par, rather than accepting them for what they are and realizing the benefits of having both.

#184 JJK

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Posted 17 December 2011 - 10:07 AM

I've viewed Jupiter through an 8" f/15 Alvan Clark refractor and was not impressed by the detail. Of course, it wasn't an APO ... but f/15! I could see just as much through my 8" f/6 Newt and much more through my 10" f/4.8 Newt. The seeing was good, 4/5, during the evening with the 8" refractor.

I just don't buy the buzz about 6" refractors - even APOs - being a superior planetary scope in comparison to a good Newt or Cat of larger aperture.

FWIW, my 70mm f/12.9 achro shows a very pleasing image of Jupiter and the Moon, but for fine detail, I'll take out the 6" Mak or a bigger Newt.

Mike



I don't buy the buzz either. Planetary views are very, very pleasing in premium APO's. But as much as I like the way Saturn looks in an AP APO, I've never been able to convince myself that I actually see more detail in an APO than an SCT of slightly larger aperture--when the seeing is good, my humble 8" SCT does a fine job on planets. So, when I had a chance to buy an AP Gran Turismo APO a couple of years ago, I just couldn't quite bring myself to pull the trigger, even though I had been on the AP notification list for something like 8-10 years.


I had an A-P130GT and can recommend it if one wants that size scope (I had too many scopes in that size to keep it). I've had a C8 (sold it) and looked through many of them. They simply do not perform as well as an A-P155 or Zeiss 150 APQ for planetary visual work. The apos in that size class consistently can be used at greater magnification.

#185 turtle86

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Posted 17 December 2011 - 10:59 AM

But the 130 Gran Turismo would have made a fine compliment to your larger reflector. I get the impression that people think that these scopes must compete on par, rather than accepting them for what they are and realizing the benefits of having both.


I really did give it some thought as the Gran Turismo is a great, great scope. If I was still imaging, I probably would've pulled the trigger.

#186 Sarkikos

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Posted 17 December 2011 - 11:20 AM

t.r,

But the 130 Gran Turismo would have made a fine compliment to your larger reflector. I get the impression that people think that these scopes must compete on par, rather than accepting them for what they are and realizing the benefits of having both.


My ST80 is not in the same league as a 130 Gran Turismo, but it can also serve as a compliment to my 10" Newt at a dark site. The little scope - especially since I've upgraded it with a 2" Crayford and collimated it closely - can show nice rich field views of the Veil, M45, North America Nebula, Milky Way star fields and the like. APers have used the ST80 for wide field photography to good effect.

If I had to choose between the ST80 and the 10" Newt, of course, the ST80 would have to go. But since they are complementary, that is beside the point.

On the other hand, for planets, I would tend to choose the larger aperture over smaller, below about 15" or so, at any rate.

Mike

#187 Sarkikos

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Posted 17 December 2011 - 11:43 AM

t.r.,

In addition, I have found that binoviewing is really where an SCT can shine. Call it what you want but used at normal magnification (<300x), the views it provides are better than monoviewing in a way that is different than just using two eyes would normally suggest...for me, it seems to perform better in this mode than one would expect it to.My C11XLT has shown planetary details my refractors NEVER did.


Substitute "Newt" for "SCT," and "C10NGT" for "CllXLT," and our experiences are identical.

Also, in my experience, a larger aperture - in this case 10" or 11" vs 5" or 6", lets say - does not need higher than "normal" magnification to see finer detail. I agree with Texereau that a 0.8mm exit pupil is about ideal for planets. For a 10" scope, 300x puts it right at 0.8mm exit pupil. What a coincidence!

To see finer detail, it's better to train the eye than to increase the magnification.

:grin:
Mike

#188 JJK

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Posted 17 December 2011 - 12:00 PM

But the 130 Gran Turismo would have made a fine compliment to your larger reflector. I get the impression that people think that these scopes must compete on par, rather than accepting them for what they are and realizing the benefits of having both.


I really did give it some thought as the Gran Turismo is a great, great scope. If I was still imaging, I probably would've pulled the trigger.


It is indeed. When I had the AP130GT, I occasionally used it on a Half-Hitch mount, which made it a highly capable portable visual system.

I was going to use the funds from the AP130GT sale to get a 50th Anniversary Questar, which I understand probably doesn't outperform a C11 :grin:, but a Tak Mewlon 300 beckoned.

#189 JJK

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Posted 17 December 2011 - 12:12 PM

t.r.,

In addition, I have found that binoviewing is really where an SCT can shine. Call it what you want but used at normal magnification (<300x), the views it provides are better than monoviewing in a way that is different than just using two eyes would normally suggest...for me, it seems to perform better in this mode than one would expect it to.My C11XLT has shown planetary details my refractors NEVER did.


Substitute "Newt" for "SCT," and "C10NGT" for "CllXLT," and our experiences are identical.

Also, in my experience, a larger aperture - in this case 10" or 11" vs 5" or 6", lets say - does not need higher than "normal" magnification to see finer detail. I agree with Texereau that a 0.8mm exit pupil is about ideal for planets. For a 10" scope, 300x puts it right at 0.8mm exit pupil. What a coincidence!

To see finer detail, it's better to train the eye than to increase the magnification.

:grin:
Mike


Mike, I'm a pretty skilled observer (I've been doing this for a long time, have had many scopes of varying quality, and I've read a great deal on the subject) and I know what my eyes need. I use a wide range of magnification to my advantage. I find that I often need more than 250x, which many C11s generally can't handle here.

I've also pushed my AP10" Mak-Cass pretty high for specific purposes. Jupiter looks phenomenal in that instrument at around 380x, but at 760x (with decent seeing), the large image is imposing, and greatly adds to one's enjoyment. I've even cranked up the mag on that scope to around 1000x in order to see the central star in M57. One does what's needed to solve a specific observing challenge.

#190 Eddgie

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Posted 17 December 2011 - 01:53 PM

There are no details to observe on double stars (other than their separation). There are on planets.



This strikes at the heart of the matter.

Angular Resolution is not meaninful in terms of describing visual performance in extended objects.

Theory (and I know that is a dirty word for many people but it is hard to have a meaningful dialog without it) says that an extended image is composed of an infinite number of overlapping DIFFRACTION PATTERNS. Note, theory does not say it is composed of overlapping AIRY DISK.

At the border where two details meet, the diffraction patters from the edge of one detail extend INTO the area of the adjacent detail

The light that DOESN'T go into the Airy Disk is distrubuted among the rings of the DIFFRACTION PATTERN.

The more light that goes into these rings, the more contrast of the adjacent detail is being reduced. The light from one side of the detail boundry extends into the adjacent detail area, and vice versa.

A perfect aperture puts about 83% of the light into the Airy Disk itself. 7% goes into the first diffraction ring, about 3% in the next ring, and less and less into each adjacent ring.

On a system with a central obstruction, depending on the percentage of size of the obstruction, far less light goes into the Airy Disk. While EVERYONE knows that the first ring is brightened, in fact, ALL of the rings past this are brightened too.

The effect is that the light being subtracted from the Airy Disk is present in sufficient quantity that even 5 or 6 rings out, there is far more light than in the perfect, unobstructed aperture.

So, if you put meaningful percentage of light out in the 4th or 5th diffraction ring, this means that for a detail 10 TIMES the diameter of the Airy Disk, contrast is being lowered.

Here is picture of a telescope with a large ccentral obstruction and so-so Optical Quality.

Imaging that this was from one of the INFINITE points along the border of a very pale oval on Jupiter. Now imagine that there was one RIGHT next to it, representing the edge of the adjacent detail, but a slightly different color.

The Diffraction Patterns would overlap for a diameter that is 9 times the diameter of the Airy Disks!

So, it this scope had an Airy Disk diameter of 1 arc second, detail 4 or 5 arc seconds away from teh EDGE of a feature would be getting light from THIS feature. This works both ways, with the light from the other side of the border of the two different details extending back into the first detail area. This acts to both soften the border itself, and blend the details into one another.

This is what lowers contrast when there is an obstruction or spherical abberation present. The more light that is comeing out of the Airy Disk means that the contrast is affected for larger and larger details.

One picture is worth a thousand words. Suppose this represts one point of light from the edge of taht pale oval, and there is another point RIGHT next to it representing the area AROUND the oval.

Does this help to understand how optical errors and central obstruction lower contrast on EXTENDED targets, by makeing the light from ALL details merge together?

And what happens when one detail is pale white and the adjacent area is pale Gray? Well, what happens is that the detail, even if it is fairly large, loose enough contrast that it falls below the eye's contrast sensitivity threshold. The eye needs about 5 to 10% contrast to detect a detail, depending on the apparent angular size. So, a faily large detail that only starts with 10% contrast on a planet, that looses 50% of that detail because of the aperture, and another 30% because of the central obstruction, and another 10% because of spherical abberation suddenly becomes impossible to see visually.

A CCD camera might show it, but it will have lost too much contrast to be seen visually.

This is why the low and mid frequencey contrast on MTF charts is so important. It describes how much detail is being lost for a detail of a particular true angular size.

Here is the pick..

Would you think THIS scope would have SUPERB contrast with light WAY out in the 4th or 5th ring?

Attached Thumbnails

  • 4971106-C9 Light distribution.jpg


#191 Sarkikos

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Posted 17 December 2011 - 03:04 PM

John,

Mike, I'm a pretty skilled observer (I've been doing this for a long time, have had many scopes of varying quality, and I've read a great deal on the subject) and I know what my eyes need. I use a wide range of magnification to my advantage. I find that I often need more than 250x, which many C11s generally can't handle here.

I've also pushed my AP10" Mak-Cass pretty high for specific purposes. Jupiter looks phenomenal in that instrument at around 380x, but at 760x (with decent seeing), the large image is imposing, and greatly adds to one's enjoyment. I've even cranked up the mag on that scope to around 1000x in order to see the central star in M57. One does what's needed to solve a specific observing challenge.



Different objects need different magnifications. For myself, I push the power for double stars, Mars, planetaries, galaxies and star tests. But in my experience, even during excellent seeing, Jupiter - being an extended low-contrast bright object - tends to bloat and show no more detail at powers much higher than a 0.8mm or 0.7mm exit pupil. Mars can take more power to good effect.

Planetaries - such as M57 and even more so, smaller PN - and also galaxies, can benefit from higher magnification because the observer views them while the eye is more dark adapted. A dark adapted eye loses much of its visual acuity. Higher power can help make up for that.

On the other hand, bright planets bring the eye up through mesopic levels and closer to photopic adaptation, so theoretically the eye shouldn't need as much magnification to see fine detail. That agrees with my practical experience.

Also, different eyes have different preferences. For me, higher magnification used on bright objects makes my eye floaters much more obvious. In terms of what adds to my enjoyment, I really do not enjoy a big bloated dimmer image, especially when accompanied by a field of floating black blobs. Additionaly, my largest scopes do not have tracking. These are two major reasons I have tried to avoid ubergross power and tried to learn to see more at more moderate magnification. I know for a fact that the brain and eyes are capable of doing that.

But whatever works for the individual observer is what counts.

:grin:
Mike

#192 Mark Costello

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Posted 17 December 2011 - 03:08 PM

But the 130 Gran Turismo would have made a fine compliment to your larger reflector. I get the impression that people think that these scopes must compete on par, rather than accepting them for what they are and realizing the benefits of having both.


That'll be easy enough for me to do since my 5" is "just" an achro and not quite in the class of a Gran Turismo. :lol: My concern is to identify a scope, preferrably a Cassegrain type (SCT or MCT), that truly compliments it while still manageable as per my earlier post.

#193 Sarkikos

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Posted 17 December 2011 - 03:53 PM

Eddgie,

We are often told on these forums that the human eye can resolve a detail one arc minute is size (to our apparent field of vision, or to say this another way, one arc minute of Apparent Field of view in an eyepeice).

Well, this as it turns out is VERY VERY VERY incomplete information.

In fact, the human eye can only resolve something 1 arc minute is size if the contrast is very high, and the eye is in photopic mode.

If the eye is in scotopic or mesoptic mode, the sensitivity falls pretty dramatically, to about 2 or 3 arc minutes, and this is when the detail is has somewhat high contarst. If the detail STARTS with low contrast, the eye will struggle to resolve a detail even of this size.


It might help to try to keep the adaptation closer to photopic levels by periodically stimulating the eye with bright white light. NOT by shining a white light directly into the eye, because that would produce an after image. But by looking at the reflection of white light on a sheet of white paper. In my experience, if this is done every ten minutes or so, the eye's ability to perceive contrast, detail and color range on Jupiter, for instance, will be appreciably improved.

The eye simply responds better to low contrast detail when it is MUCH larger than the one arc minute commonly quoted and being at the LIMIT of human vision.

So, how can an 8" APO provide a view that is similar to that of a C14 visuallly?

Because for the smallest, lowest contrast detail, if you magnify it enough to have ANGULAR size needed to resolve, it would loose luminance, and the eye would struggle to pick it out against the eye's own noise.


Additionally, you could try to keep the eye closer to photopic levels, so that it would have better perception of detail and contrast. Color discernment would also improve, which will in itself improve perception of contrast and detail.

I think this is the major reason why some observers say that images of planets look better at twilight. The eyes tend to be more photopic while there is still some light in the sky. That is what improves the view, not so much some contrast effect between the planet and the surrounding field.

Priming the eyes with bright white light is not a miracle enhancement for planet observation, but in my experience - as well as others' - it is another aid that can help.

Mike

#194 Vondragonnoggin

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Posted 17 December 2011 - 04:01 PM

But the 130 Gran Turismo would have made a fine compliment to your larger reflector. I get the impression that people think that these scopes must compete on par, rather than accepting them for what they are and realizing the benefits of having both.


That'll be easy enough for me to do since my 5" is "just" an achro and not quite in the class of a Gran Turismo. :lol: My concern is to identify a scope, preferrably a Cassegrain type (SCT or MCT), that truly compliments it while still manageable as per my earlier post.


Mark, I read your earlier post and thought you might want to look at these links:

Mirage 8" MCT

Orion 180mm

Santel 7"

Mirage 7"

I don't know if you are considering a 7" at all though, but the offerings of both Santel, and Mirage should be optically excellent with active cooling and not to heavy to manage. Of corse there is the Intes micro models too on that site. A bit more expensive, but also with active cooling. I figure the excellent baffling, smaller CO, and higher quality optics might make it so you can push the scope pretty good to some high mags, have good contrast, and make for a powerful combo with the low power widefield ability of your achro mounted on the other side of it.

I am doing the dual mount thing with a 6" mak cass and my achro. Not quite the difference that you are looking for, but all my budget allows.

#195 Mark Costello

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Posted 17 December 2011 - 06:17 PM

Hi Vondragonnoggin,

Actually, I have been "keeping the door open" on a 7" or maybe 8" MCT as a companion scope for my ES AR127 achro. Assuming that the "throughput" fraction of the MCT is the same as my refractor, the light gathering capacity of even a 7" MCT should be close to double that of my achro and MCTsdo have a good reputation for being good on planets and the moon. I should go over to your thread on your MCT and look it over, I was going to ask you how you settled on your 6" MCT. Also what mount are you using for the "dual mount thing?"

Take care and best regards,

#196 Vondragonnoggin

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Posted 17 December 2011 - 06:51 PM

Twilight II mount and I verified it will hold both OTA's. Maybe a little longer damping times, but I can get widefield low power on one side and some nice high power on the other without any false color.

Weight was a consideration. Both OTA's are similar.

Budget was a big consideration. The next step up to a 7" with 2" capability and no vignetting on large fieldstops eyepieces is a big jump in price.

I won't be missing too much if I decide to use one scope over the other on any given night and some nights I'll want a quick cool down. They really overlap on some areas but have enough difference to make it worthwhile to me.

The model I'm getting has some nice extras that usually are only offered in the more expensive models.

Good reputation on the reviews for the 6" and I believ because it has no false color and that longer focal length, will be a better high power scope despite the large CO. I also was deciding between this one and a 6" achro and asked a couple experienced observers if they were in my position, which would they choose. It solidified my choice I had already made.

Someday a 7" mak with the premium optics and active cooling if I really like this one, but for now I feel very good about the choice.

It's a fantastic deal for what you get.


Edit:

Besides all the great reviews and differences, weight, etc. one of the members here (Norme, aka Asbytec) sketches with a 150mm mak and the sketches I saw what a 6" was capable of in good seeing. Sketches give me a realistic picture of the capability if I hone my observing skills and have good conditions for viewing.

#197 Jan Owen

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Posted 17 December 2011 - 07:11 PM

I'm not sure this is what the OP intended, but this thread has evolved into something that would have made the old SAA proud...

I'm saying this from both a positive and negative perspective.

What's bad, is all the negative telescope-type bias is here (Refractors versus reflectors, etc.), but, on the other side, there's been a TON of GREAT responses on all sides of the issue, without some of the neck-biting Draculian behavior that tended to happen on SAA... I say that, even though there were still tinges of that present...

Still, BRAVO, to CN for a LONG, and yet mostly civil discourse on a potentially volatile topic...

Well done...

#198 JJK

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Posted 17 December 2011 - 09:55 PM

John,

Mike, I'm a pretty skilled observer (I've been doing this for a long time, have had many scopes of varying quality, and I've read a great deal on the subject) and I know what my eyes need. I use a wide range of magnification to my advantage. I find that I often need more than 250x, which many C11s generally can't handle here.

I've also pushed my AP10" Mak-Cass pretty high for specific purposes. Jupiter looks phenomenal in that instrument at around 380x, but at 760x (with decent seeing), the large image is imposing, and greatly adds to one's enjoyment. I've even cranked up the mag on that scope to around 1000x in order to see the central star in M57. One does what's needed to solve a specific observing challenge.



Different objects need different magnifications. For myself, I push the power for double stars, Mars, planetaries, galaxies and star tests. But in my experience, even during excellent seeing, Jupiter - being an extended low-contrast bright object - tends to bloat and show no more detail at powers much higher than a 0.8mm or 0.7mm exit pupil. Mars can take more power to good effect.

Planetaries - such as M57 and even more so, smaller PN - and also galaxies, can benefit from higher magnification because the observer views them while the eye is more dark adapted. A dark adapted eye loses much of its visual acuity. Higher power can help make up for that.

On the other hand, bright planets bring the eye up through mesopic levels and closer to photopic adaptation, so theoretically the eye shouldn't need as much magnification to see fine detail. That agrees with my practical experience.

Also, different eyes have different preferences. For me, higher magnification used on bright objects makes my eye floaters much more obvious. In terms of what adds to my enjoyment, I really do not enjoy a big bloated dimmer image, especially when accompanied by a field of floating black blobs. Additionaly, my largest scopes do not have tracking. These are two major reasons I have tried to avoid ubergross power and tried to learn to see more at more moderate magnification. I know for a fact that the brain and eyes are capable of doing that.

But whatever works for the individual observer is what counts.

:grin:
Mike


Sorry about the floaters. Also, the virtues of higher magnification are lost if the scope isn't tracking (I find it hard to keep my attention focused on a particular detail when the object moves quickly across the EP FOV). Really smooth optics with first-rate coatings in the 10" to 12" class help too. My eyes aren't getting any better with advancing age, so I don't mind dropping coin on the best optics I can get. When my eyes get worse to the point that the optics don't help at the EP, or with imaging that can be visualized well enough on a computer screen, I'll sell my premium OTAs.

I didn't use extremely high mag to view the nebulousity of M57. It was solely to see the central star.

Mike, I've seen no evidence for bloating of details in Jupiter in my AP 10" Mak-Cass at around 760x on nights with decent seeing. I wouldn't push the mag high if it wasn't useful. A Tak Mewlon 300 I recently purchased might be of like character (it seems to have smooth optics), but the seeing lately hasn't been good enough to exceed about 360x.

With the AP Mak-Cass, on nights with excellent seeing, I've even used higher mag to better discern details on Ganymede. The albedo features have structure, which I noted and subsequently found that another (but well-known) observer from the distant past reported the same shaped feature. Part of that structure was barely noticeable at mags below 400x. To be fair, I don't recall whether I could see that additional feature if I lowered the mag after realizing it was present. I'll check that out the next time the situation presents itself.

FWIW, I use Zeiss Abbé Ortho EPs (I have three sets and a Zeiss 2x Barlow), and they make a difference (in the positive sense) for me. I also use Baader and AP diagonals. For Jupiter, Saturn & Mars, Naglers don't work for me (no surprise), Radians give Jupiter's white regions a yellow cast (I don't use them when viewing planets). TeleVue Plössls aren't sharp enough (for this app). A-P SPLs, are excellent. I haven't tried TMBs yet. I'd also love to try out a Zeiss monocentric with excellent coatings.

One other thing I use high mag on (and only rarely) is to view the Moon with the RA tracking shut off. At around 1000x, I get the impression I'm in an Apollo Command Module in orbit waiting for the LEM to return. It's corny, but a lot of fun, nevertheless.

#199 Asbytec

Asbytec

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Posted 17 December 2011 - 10:49 PM

...one of the members here (Norme, aka Asbytec) sketches with a 150mm mak and the sketches I saw what a 6" was capable of in good seeing.


Makes me a little nervous being on the hook for this one. :lol: But, since I am, please let us know how you like it.

But, yea, the MCT has just floored me, really, especially in great tropical seeing when the scope is cooled. My jaw is still laying out in the back yard, it keeps falling off as I observe the planets, doubles, the moon, and even deep sky. I'd just leave it there, but a stray cat might carry it off. Dude, when foothills on the moon's limb can be seen in almost 3D, with one hill clearly descending in front of another...yea...just too beautiful.

One member of a local astro group put up some images through a 4" MCT, and they caused me to look at the MCT design. There was just something about his images that struck me, and it wasn't the wealth of detail of bigger scopes. So, I had the same influence from another MCT owner.

I am praying you're scope serves you well, and am pretty sure it will in your good seeing conditions. Illinois just got his 180 MCT and seems very pleased. Even if they don't offer refractor-like performance, as some argue, they do inspire refractor-like love for the design. Not unlike the love SCT owners exhibit, of course. My larger SCTs were almost exclusively trained on deep sky, but the smaller MCT has reawakened me to the planets and the moon and observing much more often. Having a renewed love for observing is quite thrilling in itself.

On experience observing planets, this year has been wonderful with Saturn's storm, Jupiter's musings, and even Mar's tiny disc. Spending hours observing...with a "CAT for planets"...has taught me a lot and renewed love for observing.

#200 Vondragonnoggin

Vondragonnoggin

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Posted 17 December 2011 - 11:03 PM

One of the great things about the sketching forums is being able to get a real feel for true eyepiece views for whatever scope the sketching artist is using. I think sketching is one of those artistic things that forces a person to utilize their patience and utmost observing skills. If I see some sketch done by an artist using a smaller scope than me and he is drawing things I don't see, then I know I need to study the object better or wait for a better night and study the object better. Much better than photos.

I love the photos too, but a bit unrealistic to what my eyes can record.

I need to take up sketching. Every time I have been out observing with someone else, they have remarked on how well my eyes pick up things quickly. I have astigmatism too and wear glasses sometimes, but not all the time while observing. I think I am meant to be a sketcher for my eyeballs alone. I'm a rather mediocre artist though.

:)


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