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Equipment Discussions >> Refractors

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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Achro Vs Apo new [Re: stanislas-jean]
      #5754507 - 03/24/13 05:18 PM

Quote:

Just do tests and compare them on situations, obviously actual.
Reason why I found the long achro interresting in use with more.




There is on thing about a long achro... it is long, that is one thing I have discovered in comparing achromats to apos. An 80mm F/15 achromat might provide similar planetary views to a 80mm F/7 apochromat but one is handy and easy to use, the other is by comparison, unwieldy.

Jon


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Eddgie
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Reged: 02/01/06

Re: Achro Vs Apo new [Re: stanislas-jean]
      #5754748 - 03/24/13 07:02 PM

Once again, I did not say that that a 6" SCT would blow away a 6" achromat in any way shape or form..

Why do you insist on putting words in my mouth?

I said that by the time you factor in the damage done by CA in a 6" f/10 achromat, you won't be doing that much better than you would with a C6. This is soooooo much diffent than what you are implying that I said.

Quote:

At 6", and f/10, you would do almost as well with a C6.





That sir, is a very far stretch from saying that I said a 6" SCT would "Blow away" a 6" f/10 achromat.

Never thought it, never said it, and won't defend something I did not say. I can only defend what I do say and I said that you would not be all that much better off with a 6" f/10 achroamt than with a 6" SCT.


Please please please address things I said and not debate things I didn't say.

I can't defend myself if you change what I said. My tiny sword would be getting needlessly all chipped up.

Edited by Eddgie (03/24/13 07:10 PM)


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Sean Puett
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Reged: 09/06/10

Loc: always cloudy, washington
Re: Achro Vs Apo new [Re: stanislas-jean]
      #5754787 - 03/24/13 07:28 PM

Quote:

Frankly it is not matter to be lover in apo achro reflector.
Just do tests and compare them on situations, obviously actual.
Reason why I found the long achro interresting in use with more.
I have also a 305 which is used deeply only 2 or 3 nights a year. Never more sothat a 6" stays always very profitable when the seeing (tube and local) is minimised.
Think global not on paper only, with a money bag for getting usually the more details we can.
Stanislas-Jean



That was the point of saying to try all the different types of scopes and then choosing what YOU like. It really makes no difference to a long achro lover that I think a short apo is better or a large newt is best. My opinion affects what I buy only. We all explain our reasons for choosing certain designs over others but, the only thing that ultimately matters is YOUR opinion when you decide what to buy.
To me talking about long big achros without mentioning the mount requirements is setting someone up for disappointment. Just like talking about dobs without mentioning mirror care and collimation and sometimes paracorr requirements is not acceptable to me. I also mention the need for higher priced eyepieces in fast dobs because that is another potentially bad surprise.
Try before you buy.


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buddyjesus
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Reged: 07/07/10

Loc: Davison, Michigan
Re: Achro Vs Apo new [Re: Sean Puett]
      #5755027 - 03/24/13 09:37 PM

has anyone said aperture rules yet and to get a dob instead? haha

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KWB
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Reged: 09/30/06

Loc: Westminster,Co Elev.5400 feet
Re: Achro Vs Apo new [Re: buddyjesus]
      #5755162 - 03/24/13 10:58 PM

Quote:

has anyone said aperture rules yet and to get a dob instead? haha



I've got a good idea,let's don't,and then say we did.

Let's just stay on topic and please,let us all keep the personalities out of this excellent thread. Difference of opinion makes the world go round when done in a respectful manner.


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Jeff B
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Reged: 12/30/06

Re: Achro Vs Apo new [Re: buddyjesus]
      #5755252 - 03/24/13 11:54 PM

Quote:

has anyone said aperture rules yet and to get a dob instead? haha




Yup, third post after the OP's first. Never fails.


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De Lorme
professor emeritus
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Reged: 12/30/08

Re: Achro Vs Apo new [Re: KWB]
      #5755256 - 03/24/13 11:57 PM

That's right Sean. They all have weakness. But which of them have fewer? When I look in the classifieds I see a lot of big dobs a few small apo's and a fewer still large{8"}achros.Why is this? Because over a period of time,as we grow older,body starts to give way, CONVIENCE really becomes reality. A 8" achro will allow you to sit,take you as far as a 14" dob,with no collimation issues and no waiting time for it to cool down. This why D&G,Istar are still in buisness.
There are good scopes below 14"dobs &8"refractors but they
can only take you to 10-12 Mag. This is Part of the learning curve. By the time people can afford
what ever they want people know the convience factor.
They buy large refractors and put them in a rool off roof.
This is my goal to. Right now I have a CR6" on a CGEM in a rool off roof. Hoping to put a 8"f/9 on a CGEM-DX but
mabey a 8"f/6 the CGEM. De Lorme


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jrbarnett
Eyepiece Hooligan
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Reged: 02/28/06

Loc: Petaluma, CA
Re: Achro Vs Apo new [Re: hottr6]
      #5755270 - 03/25/13 12:07 AM

That's just it. I have an inkling that one thing that keeps truly large refractors (whether labeled "achromat" or "apochromat") from being more popular is the mounting requirement. Even if you could get a truly large refractor for a low price (i.e., a 7" for $2500), you won't be putting such a scope on a $1500 mount. Mounts capable of carrying such a payload are in the $5000 range to start.

Regards,

Jim


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jrbarnett
Eyepiece Hooligan
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Reged: 02/28/06

Loc: Petaluma, CA
Re: Achro Vs Apo new [Re: orion69]
      #5755273 - 03/25/13 12:09 AM

I'd say that it largely depends of the figure quality of the Istar. A 1/3 wave 10" refractor wouldn't be blowing away a top quality 4-incher much less a TOA on planets.

- Jim


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galaxyman
Vendor - Have a Stellar Birthday
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Reged: 04/04/05

Loc: Limerick, Pa
Re: Achro Vs Apo new [Re: Eddgie]
      #5755334 - 03/25/13 12:52 AM

Quote:



Why do people think large achrmats are so great?







Well maybe because they have actually had great views with them? Unless you think they are all full of it?

I don't mask any of my achros (don't need to with my observing). Have you actually seen through say a 6", 7" or even a 8" achro of high quality in the DSO realm?

I've seen many DSO views side by side of equal or close to equal aperture of various types of scopes, including a 6" quality achro and 6" APO. The views were very close in the APO's favor as it should.

I've seen a 7.1" high quality achro next to a 6" f/9 APO, and the achro was most definitely the superior DSO scope.

What I have seen in many of of these larger achros is no doubt variable optical quality of fair to quite good, but also the collimation way off, and in some cases really bad.

Don't get me wrong I'll take your 6" APO over my 6" achro in a heart beat (not the 8" though ), but I've seen these 6" achros go very deep per it's aperture in DSO observing.


Karl
E.O.H.


Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Galaxy Log Blog - http://galaxylog.blogspot.com/
HASB - http://www.haveastellarbirthday.com
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos


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Sean Puett
Carpal Tunnel
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Reged: 09/06/10

Loc: always cloudy, washington
Re: Achro Vs Apo new [Re: De Lorme]
      #5755340 - 03/25/13 01:00 AM

Quote:

That's right Sean. They all have weakness. But which of them have fewer? When I look in the classifieds I see a lot of big dobs a few small apo's and a fewer still large{8"}achros.Why is this? Because over a period of time,as we grow older,body starts to give way, CONVIENCE really becomes reality. A 8" achro will allow you to sit,take you as far as a 14" dob,with no collimation issues and no waiting time for it to cool down. This why D&G,Istar are still in buisness.
There are good scopes below 14"dobs &8"refractors but they
can only take you to 10-12 Mag. This is Part of the learning curve. By the time people can afford
what ever they want people know the convience factor.
They buy large refractors and put them in a rool off roof.
This is my goal to. Right now I have a CR6" on a CGEM in a rool off roof. Hoping to put a 8"f/9 on a CGEM-DX but
mabey a 8"f/6 the CGEM. De Lorme



See what you just posted proves my point. I have no desire to have a stationary observatory. You do. That is great. It is opinion and nothing more. I would rather have an np127 than an 8" f6 achro. Is that good or bad? No it just is. I would still enjoy looking through your scope but, I would prefer something else. It shouldn't matter that I prefer a smaller apo, right? My refractor doesn't have perfect color correction but, it is good enough for me. I can coax out false color by using high mag on Jupiter and especially Venus. Someone at a star party actually said he could see false color at 19x mag on dim stars. I just let him make his statement laughed to myself later and went on. Maybe he has super eyes, it doesn't mean my scope is any less to me.

There are normally 3x as many refractors on the used market as newts. This site may be different since the ads never expire but, if you check Astromart at nearly any time there will be 55-70 refractors for sale and 20-30 newts.
Jim is spot on with the mount requirements being an issue for large achro sales. If you have to spend 5000 on a mount, why not buy an apo? You could get a used FS152 flourite doublet for that amount or a bit more. Or a TEC 140.


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timps
sage


Reged: 02/24/13

Re: Achro Vs Apo new [Re: Sean Puett]
      #5755366 - 03/25/13 01:20 AM

Maybe I should go down the Newtonian reflector path?
Long FL with high quality optics and it would be on par with a large aperture Apo for a fraction of the cost.


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De Lorme
professor emeritus
*****

Reged: 12/30/08

Re: Achro Vs Apo new [Re: Sean Puett]
      #5755385 - 03/25/13 01:39 AM

Sean, in theory I agree with you it does not matter. But
Convience is not a theory. When you have rool off roof
it's just so much easier. No wasted time. No limitations
on which scope to buy or set up. I've seen mabey 2 large refractors {8"}and 1 8" lens up for sale in the last 5 years. I look every day.D&G and Istar are still in buisness.
Karl, I'm thinking a 8"F/6 would ride fine on my CGEM.
1.Tub weights 10.75lbs. ,2. lens 10.25klbs. 4.rings weight aprox. 10lbs 4. lenght is no longer than a AT 10" reflector{which rode well on top of my CGEM} and smaller in diameter.
I"ve never looked through a 8" so being an fast f/6 would I be able to use enough power to bring in and thus resolve
gobular clusters? What do you think? De Lorme


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stanislas-jean
Carpal Tunnel


Reged: 10/22/08

Re: Achro Vs Apo new [Re: Sean Puett]
      #5755461 - 03/25/13 02:57 AM

After a comparison on long term placed on a site, mine, I found the long achro getting the best efficiency over a year.
Not matter of love, an OTA is just a tool.
Stanislas-Jean


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mark8888
Carpal Tunnel


Reged: 09/24/10

Re: Achro Vs Apo new [Re: stanislas-jean]
      #5755482 - 03/25/13 03:58 AM

Quote:

Maybe I should go down the Newtonian reflector path?
Long FL with high quality optics and it would be on par with a large aperture Apo for a fraction of the cost.




Not to derail this thread at all, but responding to the following quote above: "on par with a large aperture Apo". I am wondering the same thing, as I read this thread and the other recent interesting thread concerned with large refractors... speaking about visual only, in moderate to very good seeing, is there any advantage in getting a large APO as opposed to a reflector (of any size)? A large APO, say 7 inches and above, costs in the neighborhood of 20K+ , plus the sizable mount as has been remarked above in the thread. High quality reflectors of greater/much greater aperture cost significantly less. Yet many people buy the large APOs and profess to be visual only. Why? It has often been said that if you get a high quality reflector of a couple of inches or more greater than the size of an APO refractor, all the visual advantages of the refractor disappear vs. the reflector, and thus there is no point in getting the large refractor for visual (besides the wider field). In people's experience here, is that true, or is there something else special about the view through a 175mm + refractor that makes it unique? Why might one prefer the view through the large high quality APO refractor as opposed to a larger, much cheaper high quality reflector?


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beanerds
sage


Reged: 07/15/08

Loc: Darwin Australia
Re: Achro Vs Apo new [Re: Jon Isaacs]
      #5755498 - 03/25/13 04:37 AM

Yep Jon I did mention that a few posts back , ' The Takahashi is way easier to drag out in one hand , tripod and all , plonk down and observe .
Nothing better , or easier , and in that respect it does get used the most out of all my scopes . .
Shes a little sweety .
Brian.
Quote:

Quote:

Just do tests and compare them on situations, obviously actual.
Reason why I found the long achro interresting in use with more.




There is on thing about a long achro... it is long, that is one thing I have discovered in comparing achromats to apos. An 80mm F/15 achromat might provide similar planetary views to a 80mm F/7 apochromat but one is handy and easy to use, the other is by comparison, unwieldy.

Jon




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De Lorme
professor emeritus
*****

Reged: 12/30/08

Re: Achro Vs Apo new [Re: mark8888]
      #5755507 - 03/25/13 04:50 AM

Because it's not primarily about just the view. Comfort and
ease of use are equally as important. A 8" F/8.8 achro refractor lens from Istar is about $1700. I would say a 16"
reflector mirror would be about a 1/3 more. The aproximate
total weight on putting a 8"F/6 on my CGEM is around 32lbs
with a length of 48" for about $2500. How much does a goto
trackimg system for a large reflector cost. About the same
or a little more than a CGEM-DX. But which one is more difficult to use. The reflector.
Reflectors you have to collimate accurately.
You have to install fans to get them to ambeint tempertures
You have to wait until cooled.
You have to stand on a stool or ladder to view.
Have to buy a coma corrector
Eyepieces cost considerably more
Large refractors take a lot more time to set up
Refractors have none of these problems.
One thing I will say though with Orion making large goto dobs cheaper than a large refractor that might make a differance initially. But I believe in the long run the extra cost to be able to sit and not have the other issues
will be worth it. People really do not consider convience
until they experience not having it. De Lorme


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beanerds
sage


Reged: 07/15/08

Loc: Darwin Australia
Re: Achro Vs Apo new [Re: timps]
      #5755517 - 03/25/13 05:03 AM

Yes you can Timps , and it's has has been said here a reflector is the bast 'Bang for Buck' out there . True words .

But you have to realise that any Newtonion no matter how good it is requires constant maintance to keep it at its best ,thats been mentioned here as well .
But here is the crux !!! ,,
At midnight would you rather be at least 1.5 meter's off the groung on a ladder or stool looking at say , Jupiter with an awsome 8-10 inch f9-10 newt ? they need to be at least this long (f9-10) to keep the secondary as small as possible to keep the 'Contrast of the view' at its best , or ,,,,,
Comfortably seated on an observing chair looking at jupiter in even a lowely 6-8 inch f8-10 Achromat refractor ?

My aswome 10 inch f10 has a 2500mm focal length and when observing the zenith ( where the best seeing is ) I am nearly 2 metre's up to see thru the eyepiece .
Some people are uncomfortable with that at night .

Just a reminder that , that it can be a problem showing , say your Mum or other person jupiter at 10 pm ?.
Brian.
Quote:

Maybe I should go down the Newtonian reflector path?
Long FL with high quality optics and it would be on par with a large aperture Apo for a fraction of the cost.




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timps
sage


Reged: 02/24/13

Re: Achro Vs Apo new [Re: beanerds]
      #5755535 - 03/25/13 05:50 AM

Deffinately food for thought.

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t.r.
Post Laureate
*****

Reged: 02/14/08

Loc: Upstate NY
Re: Achro Vs Apo [Re: timps]
      #5755649 - 03/25/13 08:19 AM

Quote:

In people's experience here, is that true, or is there something else special about the view through a 175mm + refractor that makes it unique? Why might one prefer the view through the large high quality APO refractor as opposed to a larger, much cheaper high quality reflector?



CONTRAST for its given aperture.


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