298 replies to this topic

[woodsman]

Ken,
I'm not trying to score any points. The funny thing to me is that when fellows like yourself post, ignoring the flaws of some designs, it seems to irritate you that someone points out the unsubstantiated statements that you make, such as this:

Based purely on optical quality and the image provided, SCTs come in last when comparing equal sized telescopes

So says you. Point being that on pure optical quality, YOU may think that Newts provide a better image, but I don't. I don't want to see diffraction spikes. Both have coma, the Newt more severe, and the SCT can be corrected for said coma. How do you correct for Coma in a Newtonian? If you feel that Newts have an advantage over SCTs, good for you. It means that you don't mind the optical abberations as much as another may. The optical quality on scopes is subjective to many, so your blanket statement is faulty IMO.

Nothing more, nothing less...

[94bamf]

Ken,
I'm not trying to score any points. The funny thing to me is that when fellows like yourself post, ignoring the flaws of some designs, it seems to irritate you that someone points out the unsubstantiated statements that you make, such as this:

Based purely on optical quality and the image provided, SCTs come in last when comparing equal sized telescopes

So says you. Point being that on pure optical quality, YOU may think that Newts provide a better image, but I don't. I don't want to see diffraction spikes. Both have coma, the Newt more severe, and the SCT can be corrected for said coma. How do you correct for Coma in a Newtonian? If you feel that Newts have an advantage over SCTs, good for you. It means that you don't mind the optical abberations as much as another may. The optical quality on scopes is subjective to many, so your blanket statement is faulty IMO.

Nothing more, nothing less...

Rich, I wasn't ignoring the flaws of other designs. I didn't feel the need to list the flaws of every design, it has been covered ad nauseum in this very thread over and over. They ALL have flaws, I freely admit that. I can also assure you I am not irritated either.. You say you are not trying to score points, yet it seems you want to counterpoint every negative listed for a SCT, like it is some competition that we can add a score up for at the end. Optically a SCT is the most compromised design. That is fact, not subjective opinion. We could go through every point one by one, actually we don't need to, Eddgie already did that. Some how you can't seem to accept that fact. Somehow you seem to think admiting it is the most compromised design optically, is the same thing as calling it a bad design or a bad telescope. They are not the same thing. You seem to be convinced that anybody who mentions the flaws in a SCT design has some axe to grind with them. I didn't wake up today and say "Man, lets go bash some SCTs in the SCT forum". Anyway, this is becoming a circular argument. Enjoy your SCT, I will enjoy mine..

Ken

[Joe Bergeron]

The use of the Barlow lens to increase the apparent FL of a Newtonian has eluded you, and apparently you haven't heard of the Paracorr either (the way to correct coma in Newtonians, if needed).

The smaller secondary obstruction of most Newtonians is enough to produce superior performance all by itself.

[rdl800]

I never imagined it would be this good...

[bobhen]

Because you don’t want to cart around a large Newtonian does not mean others will not. They will be sacrificing portability for better performance. Just like some who have purchased very large Apos have sacrificed cost for performance.
Bob

are we supposed to size the car to the scope? Or the scope to the car? In my case the 10" f/6 Newt is as big as I can go and still remain Corolla compatible.

If the criterion is GEM + fits in car, actually, the C14 is the biggest aperture I can carry. And it might be at the limit of what I can carry in a truss dob.

Anyhow for GEM users the maximum usable Newt for any given size mount is probably in the range of 60% of the aperture of the SCT that would ride comfortably on the same mount.

regards
Greg N

If your main goal is to cram as much scope into a Corolla as possible, then within your very specific and limited situation, you are indeed exploiting the main attribute of the SCT – compact aperture.

But, if your main goal is traveling to a dark site to visually observe deep-sky objects, then why not consider going slightly outside of those limited parameters and add a small trailer that would hold a 16-inch or even larger lightweight, truss Dob on a tracking platform. Lots of people use that solution. And if the scope was to be used only as a dark-sky “road scope” you could just leave it in the trailer – very convenient. And you will have achieved the goal of better deep-sky performance. And you would also have room to take someone with you.

I’m also not sure about the 60% figure you mention as Orion UK sells a 16-inch solid tube f4 Newtonian (this would only be 4 inches or so longer than your current 10-inch F6) and at around 65 pounds or so should ride “reasonably” well on your AP 900 (with a low profile tripod) and deliver more deep-sky performance than the C14. Might even be able to cram that OTA into the Corolla as well.

Bob

[woodsman]

Ken,
I'm not trying to score any points. The funny thing to me is that when fellows like yourself post, ignoring the flaws of some designs, it seems to irritate you that someone points out the unsubstantiated statements that you make, such as this:

Based purely on optical quality and the image provided, SCTs come in last when comparing equal sized telescopes

So says you. Point being that on pure optical quality, YOU may think that Newts provide a better image, but I don't. I don't want to see diffraction spikes. Both have coma, the Newt more severe, and the SCT can be corrected for said coma. How do you correct for Coma in a Newtonian? If you feel that Newts have an advantage over SCTs, good for you. It means that you don't mind the optical abberations as much as another may. The optical quality on scopes is subjective to many, so your blanket statement is faulty IMO.

Nothing more, nothing less...

Rich, I wasn't ignoring the flaws of other designs. I didn't feel the need to list the flaws of every design, it has been covered ad nauseum in this very thread over and over. They ALL have flaws, I freely admit that. I can also assure you I am not irritated either.. You say you are not trying to score points, yet it seems you want to counterpoint every negative listed for a SCT, like it is some competition that we can add a score up for at the end. Optically a SCT is the most compromised design. That is fact, not subjective opinion. We could go through every point one by one, actually we don't need to, Eddgie already did that. Some how you can't seem to accept that fact. Somehow you seem to think admiting it is the most compromised design optically, is the same thing as calling it a bad design or a bad telescope. They are not the same thing. You seem to be convinced that anybody who mentions the flaws in a SCT design has some axe to grind with them. I didn't wake up today and say "Man, lets go bash some SCTs in the SCT forum". Anyway, this is becoming a circular argument. Enjoy your SCT, I will enjoy mine..

Ken

I see Ken, so if YOU state something with emphasis over and over, ignoring the flaws of other designs, you're not trying to score points, but if I point out certain aspects of Newtonians and don't concede what you FEEL about the design, that they are better I'M therefore being obstinate? Hmm, that's interesting.

I noticed that a poster following yours now says that the Newtonian's design having coma can be CORRECTED using a Parracorr. Ok, so tell me Ken or other poster, how is it that a Newtonian NEEDS correcting for Coma, but that isn't a design compromise, is it? Maybe the severity of the compromise is in the eye of the beholder?

Ken, I'm not countering any of the flaws of the SCT. I believe I stated that they have coma, although not as severe as in the standard Newt design, you know, the ones that can be corrected with a Parracorr?

I've simply pointed out the fact that Newts are cumbersome, bulky, not easily transportable, and heavy compared to similar sized SCTs. Is that untrue? I challenge you Ken to show me where I am in denial about the design flaws of the SCT. Which SCT problem have I denied? It seems to me that you might just be the one who is in denial.

Perhaps you can answer a few simple questions Ken. Is a 14 inch Classic Newt as easily transportable as an SCT? Would a 14 inch Newtonian have more coma than an SCT? That was basically all that I stated. I haven't denied the theoretical design flaws in the SCT, I simply said they didn't cause issues for me. There is coma in an SCT. Mine has so very little, its hard for me to see. I also know for a fact and haven't denied that the contrast isn't as good in an SCT as other designs. I think I stated in another post SO What? Therefore no issue really for me. How is that being in denial Ken??

[woodsman]

Post deleted by woodsman

[woodsman]

Because you don’t want to cart around a large Newtonian does not mean others will not. They will be sacrificing portability for better performance. Just like some who have purchased very large Apos have sacrificed cost for performance.
Bob

are we supposed to size the car to the scope? Or the scope to the car? In my case the 10" f/6 Newt is as big as I can go and still remain Corolla compatible.

If the criterion is GEM + fits in car, actually, the C14 is the biggest aperture I can carry. And it might be at the limit of what I can carry in a truss dob.

Anyhow for GEM users the maximum usable Newt for any given size mount is probably in the range of 60% of the aperture of the SCT that would ride comfortably on the same mount.

regards
Greg N

If your main goal is to cram as much scope into a Corolla as possible, then within your very specific and limited situation, you are indeed exploiting the main attribute of the SCT – compact aperture.

But, if your main goal is traveling to a dark site to visually observe deep-sky objects, then why not consider going slightly outside of those limited parameters and add a small trailer that would hold a 16-inch or even larger lightweight, truss Dob on a tracking platform. Lots of people use that solution. And if the scope was to be used only as a dark-sky “road scope” you could just leave it in the trailer – very convenient. And you will have achieved the goal of better deep-sky performance. And you would also have room to take someone with you.

I’m also not sure about the 60% figure you mention as Orion UK sells a 16-inch solid tube f4 Newtonian (this would only be 4 inches or so longer than your current 10-inch F6) and at around 65 pounds or so should ride “reasonably” well on your AP 900 (with a low profile tripod) and deliver more deep-sky performance than the C14. Might even be able to cram that OTA into the Corolla as well.

Bob

LOL!!
So now instead of just saying that the SCT has an advantage over the Newt or Dob in size, your suggestion is to buy a Trailer?? Whatever you do, don't concede that someone might actually prefer an SCT because of its compact design, instead suggest that someone now should simply ADD a TRAILER to their car so that they can Cart around a giant Newtonian????? Really, that is your answer?? Hilarious! Should the person also buy a portable engine hoist to move the behemoth??

And you Dob and Newt fans say that we SCT guys can't concede anything?

[woodsman]

The use of the Barlow lens to increase the apparent FL of a Newtonian has eluded you, and apparently you haven't heard of the Paracorr either (the way to correct coma in Newtonians, if needed).

The smaller secondary obstruction of most Newtonians is enough to produce superior performance all by itself.

Actually, I don't know what a Parracorr is, but thanks for at least admitting that Newts have so much coma that they need correcting using one of these devices.

And no, the idea of a Barlow hasn't eluded me. I have several. The fact is that with the same size mirror, a typical SCT has a longer FL than a Newt, therefore higher magnification. And guess what? The SCT can achieve a higher magnification because it can use the same Barlow.. Did that little tidbit elude you??

[94bamf]

Ken,
I'm not trying to score any points. The funny thing to me is that when fellows like yourself post, ignoring the flaws of some designs, it seems to irritate you that someone points out the unsubstantiated statements that you make, such as this:

Based purely on optical quality and the image provided, SCTs come in last when comparing equal sized telescopes

So says you. Point being that on pure optical quality, YOU may think that Newts provide a better image, but I don't. I don't want to see diffraction spikes. Both have coma, the Newt more severe, and the SCT can be corrected for said coma. How do you correct for Coma in a Newtonian? If you feel that Newts have an advantage over SCTs, good for you. It means that you don't mind the optical abberations as much as another may. The optical quality on scopes is subjective to many, so your blanket statement is faulty IMO.

Nothing more, nothing less...

Rich, I wasn't ignoring the flaws of other designs. I didn't feel the need to list the flaws of every design, it has been covered ad nauseum in this very thread over and over. They ALL have flaws, I freely admit that. I can also assure you I am not irritated either.. You say you are not trying to score points, yet it seems you want to counterpoint every negative listed for a SCT, like it is some competition that we can add a score up for at the end. Optically a SCT is the most compromised design. That is fact, not subjective opinion. We could go through every point one by one, actually we don't need to, Eddgie already did that. Some how you can't seem to accept that fact. Somehow you seem to think admiting it is the most compromised design optically, is the same thing as calling it a bad design or a bad telescope. They are not the same thing. You seem to be convinced that anybody who mentions the flaws in a SCT design has some axe to grind with them. I didn't wake up today and say "Man, lets go bash some SCTs in the SCT forum". Anyway, this is becoming a circular argument. Enjoy your SCT, I will enjoy mine..

Ken

I see Ken, so if YOU state something with emphasis over and over, ignoring the flaws of other designs, you're not trying to score points, but if I point out certain aspects of Newtonians and don't concede what you FEEL about the design, that they are better I'M therefore being obstinate? Hmm, that's interesting.

I noticed that a poster following yours now says that the Newtonian's design having coma can be CORRECTED using a Parracorr. Ok, so tell me Ken or other poster, how is it that a Newtonian NEEDS correcting for Coma, but that isn't a design compromise, is it? Maybe the severity of the compromise is in the eye of the beholder?

Ken, I'm not countering any of the flaws of the SCT. I believe I stated that they have coma, although not as severe as in the standard Newt design, you know, the ones that can be corrected with a Parracorr?

I've simply pointed out the fact that Newts are cumbersome, bulky, not easily transportable, and heavy compared to similar sized SCTs. Is that untrue? I challenge you Ken to show me where I am in denial about the design flaws of the SCT. Which SCT problem have I denied? It seems to me that you might just be the one who is in denial.

Perhaps you can answer a few simple questions Ken. Is a 14 inch Classic Newt as easily transportable as an SCT? Would a 14 inch Newtonian have more coma than an SCT? That was basically all that I stated. I haven't denied the theoretical design flaws in the SCT, I simply said they didn't cause issues for me. There is coma in an SCT. Mine has so very little, its hard for me to see. I also know for a fact and haven't denied that the contrast isn't as good in an SCT as other designs. I think I stated in another post SO What? Therefore no issue really for me. How is that being in denial Ken??

Exactly!

Ken

[Joe Bergeron]

I did say "if needed". But you seem to have a problem with selective reading comprehension.

[woodsman]

Ok. So we are in agreement...... you were wrong.

[woodsman]

I did say "if needed". But you seem to have a problem with selective reading comprehension.

Actually I read and comprehend just fine, so perhaps you can explain, is there a typical Newtonian with a parabola shaped mirror that doesn't exhibit comatic problems?? If not then which ones don't "need" corrected?

[94bamf]

The use of the Barlow lens to increase the apparent FL of a Newtonian has eluded you, and apparently you haven't heard of the Paracorr either (the way to correct coma in Newtonians, if needed).

The smaller secondary obstruction of most Newtonians is enough to produce superior performance all by itself.

Actually, I don't know what a Parracorr is, but thanks for at least admitting that Newts have so much coma that they need correcting using one of these devices.

And no, the idea of a Barlow hasn't eluded me. I have several. The fact is that with the same size mirror, a typical SCT has a longer FL than a Newt, therefore higher magnification. And guess what? The SCT can achieve a higher magnification because it can use the same Barlow.. Did that little tidbit elude you??

When did it become a competition to see who can achieve the most magnification? Why would you even think that was an important factor? With my current eyepieces, I can achieve 400x with my XX14i without barlows, which is more magnification than my seeing conditions can support on most nights. How is it an advantage to have more magnification than you could ever use? On the other end of the scale though, the shorter focal length means I can achieve a much wider TFOV and much lower magnification than I could if my scope was F/10.


Ken

[Patrick]

Based purely on optical quality and the image provided, SCTs come in last when comparing equal sized telescopes

Optically a SCT is the most compromised design.

If you haven't guessed by now, the typical SCT owner is perhaps a little sensitized to comments like the above. As I said before somewhere way up in this thread, the optical differences between these scope designs are mostly exaggerated. The seeing conditions are by far the limiting factor in optical instruments and the SCT is no exception. I know what my C11 is capable of in excellent seeing conditions, and I also know most of the time it's seeing limited.

The SCT is one of the most popular telescope designs ever created precisely because of the compromises it makes. The compromises give it versatility and utility over every other design I know of at an affordable price point. The one major negative, which is a large central obstruction, can be overcome with aperture. And it just so happens that aperture is one of it's advantages. It's a win...win!

So, I celebrate the SCT's 'compromises'. Everything is a compromise in life, and the SCT does a good job of bringing it all together. Aperture, portability, excellent views, easy mounting, etc.

Clear skies! Let's keep it friendly!

Patrick

[94bamf]

Ok. So we are in agreement...... you were wrong.

Wrong, no.

Sometimes you have to know when, to say when.

Ken

[woodsman]

The use of the Barlow lens to increase the apparent FL of a Newtonian has eluded you, and apparently you haven't heard of the Paracorr either (the way to correct coma in Newtonians, if needed).

The smaller secondary obstruction of most Newtonians is enough to produce superior performance all by itself.

Actually, I don't know what a Parracorr is, but thanks for at least admitting that Newts have so much coma that they need correcting using one of these devices.

And no, the idea of a Barlow hasn't eluded me. I have several. The fact is that with the same size mirror, a typical SCT has a longer FL than a Newt, therefore higher magnification. And guess what? The SCT can achieve a higher magnification because it can use the same Barlow.. Did that little tidbit elude you??

When did it become a competition to see who can achieve the most magnification? Why would you even think that was an important factor? With my current eyepieces, I can achieve 400x with my XX14i without barlows, which is more magnification than my seeing conditions can support on most nights. How is it an advantage to have more magnification than you could ever use? On the other end of the scale though, the shorter focal length means I can achieve a much wider TFOV and much lower magnification than I could if my scope was F/10.


Ken

Yeah Ken,
I suppose the 15 seconds it takes for me to install that focal reducer is a killer. Then my C14 goes from f/11 to f/7 and my C8 goes from f/10 to f6.3. A dilemma for sure!

[94bamf]

Based purely on optical quality and the image provided, SCTs come in last when comparing equal sized telescopes

Optically a SCT is the most compromised design.

If you haven't guessed by now, the typical SCT owner is perhaps a little sensitized to comments like the above. As I said before somewhere way up in this thread, the optical differences between these scope designs are mostly exaggerated. The seeing conditions are by far the limiting factor in optical instruments and the SCT is no exception. I know what my C11 is capable of in excellent seeing conditions, and I also know most of the time it's seeing limited.

The SCT is one of the most popular telescope designs ever created precisely because of the compromises it makes. The compromises give it versatility and utility over every other design I know of at an affordable price point. The one major negative, which is a large central obstruction, can be overcome with aperture. And it just so happens that aperture is one of it's advantages. It's a win...win!

So, I celebrate the SCT's 'compromises'. Everything is a compromise in life, and the SCT does a good job of bringing it all together. Aperture, portability, excellent views, easy mounting, etc.

Clear skies! Let's keep it friendly!

Patrick

I agree with this post 100 percent..

Ken

[woodsman]

By the way Ken, does that barlow make your scope f/11?? Just curious..

[94bamf]

The use of the Barlow lens to increase the apparent FL of a Newtonian has eluded you, and apparently you haven't heard of the Paracorr either (the way to correct coma in Newtonians, if needed).

The smaller secondary obstruction of most Newtonians is enough to produce superior performance all by itself.

Actually, I don't know what a Parracorr is, but thanks for at least admitting that Newts have so much coma that they need correcting using one of these devices.

And no, the idea of a Barlow hasn't eluded me. I have several. The fact is that with the same size mirror, a typical SCT has a longer FL than a Newt, therefore higher magnification. And guess what? The SCT can achieve a higher magnification because it can use the same Barlow.. Did that little tidbit elude you??

When did it become a competition to see who can achieve the most magnification? Why would you even think that was an important factor? With my current eyepieces, I can achieve 400x with my XX14i without barlows, which is more magnification than my seeing conditions can support on most nights. How is it an advantage to have more magnification than you could ever use? On the other end of the scale though, the shorter focal length means I can achieve a much wider TFOV and much lower magnification than I could if my scope was F/10.


Ken

Yeah Ken,
I suppose the 15 seconds it takes for me to install that focal reducer is a killer. Then my C14 goes from f/11 to f/7 and my C8 goes from f/10 to f6.3. A dilemma for sure!

Not sure what that has to do with my post, but ok..

Ken

[94bamf]

By the way Ken, does that barlow make your scope f/11?? Just curious..

Why would I want or need my scope to be F/11?

Ken

[woodsman]

Based purely on optical quality and the image provided, SCTs come in last when comparing equal sized telescopes

Optically a SCT is the most compromised design.

If you haven't guessed by now, the typical SCT owner is perhaps a little sensitized to comments like the above. As I said before somewhere way up in this thread, the optical differences between these scope designs are mostly exaggerated. The seeing conditions are by far the limiting factor in optical instruments and the SCT is no exception. I know what my C11 is capable of in excellent seeing conditions, and I also know most of the time it's seeing limited.

The SCT is one of the most popular telescope designs ever created precisely because of the compromises it makes. The compromises give it versatility and utility over every other design I know of at an affordable price point. The one major negative, which is a large central obstruction, can be overcome with aperture. And it just so happens that aperture is one of it's advantages. It's a win...win!

So, I celebrate the SCT's 'compromises'. Everything is a compromise in life, and the SCT does a good job of bringing it all together. Aperture, portability, excellent views, easy mounting, etc.

Clear skies! Let's keep it friendly!

Patrick

For me, its all in good fun.

[jrcrilly]

...enforcing a cooling-off period...

[Joe Bergeron]

Is this buffoon act of yours deliberate, or does it just come naturally?

A fast Newt of f/5 or faster has enough coma that it can benefit from the use of a Paracorr. An f/6 has about the same amount of coma as a normal SCT, or so I understand. Anything longer has less.

Do you realize that I can stack Barlows in an f/20 Mak and attain magnifications even more absurd and useless than yours?