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Equipment Discussions >> Cats & Casses

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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: R L Harris]
      #5829215 - 04/28/13 09:59 PM

Quote:

I have seen some fantastic views in newtonians in my life time!
I started out in astronomy when I was 14 years old 1972!
ground my first telescope lense when I was 16-1974!
Worked for Celestron !978-1980 as optical Assembler Mainly
worked on C-14!
And have used and built many scopes in my life time!




I'm not knocking the virtues of Newtonians with well-figured mirrors. I'm simply suggesting that an AP 10" f/14.6 Mak-Cass will outperform a more conventional 10" f/5 Newt on lunar and planetary views for several reasons.


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R L Harris
member


Reged: 01/31/13

Loc: Independence,MO
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: JJK]
      #5829262 - 04/28/13 10:28 PM

I agree with that even SC would work a little better on
Planetary but mak are awesome scopes for it -
but expensive lol!


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iluxo
sage


Reged: 09/23/08

Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: R L Harris]
      #5829547 - 04/29/13 04:46 AM

I'm not disputing the possible qualities of a 10" f/5 primary mirror.

What does concern me - after 40 years experience - is the performance of eyepieces, especially short ones. If you regularly observe at x1 or more per mm of aperture a long focal ratio scope coupled with a quite modest medium f.l. eyepiece is a far more appropriate solution than any f/5 scope no matter how perfect the primary, and any eyepiece combination your can come up with.

One of the major drawbacks at the eyepiece end - especially with very short f.l. eyepieces - is the scattering, losses and general image degradation arising from the number of air-glass surfaces and the scattering within the eyepiece. Adding a Barlow or PowerCorr only makes it worse.


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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: iluxo]
      #5829613 - 04/29/13 07:13 AM

Quote:


What does concern me - after 40 years experience - is the performance of eyepieces, especially short ones. If you regularly observe at x1 or more per mm of aperture a long focal ratio scope coupled with a quite modest medium f.l. eyepiece is a far more appropriate solution than any f/5 scope no matter how perfect the primary, and any eyepiece combination your can come up with.




I think Texereau said it best:

"It is not usually made clear, that these elements, objective and eyepiece, are by no means comparable in importance. The astronomer's hopes are almost wholly tied to the size and quality of the objectve. The objective of even the smallest telescope, because of its larger dimensions, the severe optical requirements it must meet, and the difficulty of its construction, completely overshadows the eyepiece."

- "How to Make a Telescope," by Jean Texereau, Page 1, Paragraph 2.

When it comes to planetary viewing, the most important factor is the seeing, then comes the scope, the size, the quality and thermal state.

Jon


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azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Jon Isaacs]
      #5830931 - 04/29/13 07:09 PM

Quote:

Quote:

Quote:

You're all missing something - you need eyepieces to see anything. It isn't just about CO and MTF.

On the planets I'd much rather use an f/15 Mak with a 10mm eyepiece than struggle with an f/5 Newtonian with any 3.5mm eyepiece you can name (to achieve roughly the same magnification).

Barlows/Powermates etc don't help either.




No they dont. Barlows are cosmetic attachments to make low power oculars feel mighty.

P.




As someone who actually uses F/5 Newtonians for Planetary viewing, Barlows can be an effective tool. It's probably easier to fabricate a high quality Barlow than a high quality 5x magnifying mirror...

Jon




I was jesting. I love barlows.

Pete


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iluxo
sage


Reged: 09/23/08

Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5831472 - 04/30/13 01:33 AM

Well ... I know many will still shake their heads in disbelief but all I can say is go try it, as I did 2 nights ago.

... a direct practical test on Saturn which at the moment is near the zenith here - my 7" f/15 Mak vs a very good 10" f/5 dob 2 nights ago.

The 10" dob gave a brighter image, no question, but the 7" Mak showed more details on Saturn.

The eyepieces used in both scopes were my set of Vixen LVW's; 13mm in the 7" Mak gave almost identical magnification as 5mm in the 10" dob. The owner of the dob was quite interested in the side-by-side comparison.

A good 10" f/15 Mak will easily SLAY a 10" f/5 newtonian on the planets, for resolution of fine detail.



Edited by iluxo (04/30/13 01:35 AM)


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azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: iluxo]
      #5831661 - 04/30/13 07:13 AM

See that's my finds with my 8" versus the 10" reflector - its big and bright but not as detailed. As I've mentioned (ad naus.) an f/7 is a different kind of 10" though.

Pete


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GeneT
Ely Kid
*****

Reged: 11/07/08

Loc: South Texas
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5833181 - 04/30/13 08:42 PM

Quote:

10" f/14.6 Mak 23% co
10" f/5 newt 26% co




For a 10 inch F5 Newt, 26 percent CO seems a little high. There are models that are in the 20-22 percent range. However, I don't think a few percent extra CO will be all that noticeable if the optics are of high quality.


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azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: GeneT]
      #5833272 - 04/30/13 09:42 PM

Thanks Gene. Others have mentioned that too . I can attest my 10" f/5 was that.

Pete


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issdaol
member


Reged: 01/01/10

Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Eddgie]
      #5870135 - 05/18/13 08:30 PM

Quote:


There was a thread a while back that pitted a 250 Mewlon against the 10" AP and I picked the 10" AP on that one.

For that one, the Mewlon had a meaningfully bigger CO, but more importantly, the bench tests I have seen on Mewlons have led me to believe that they are not made to the same high level of perfection that you would get from either the AP or a custom mirror Dob.






Would appreciate if you can point us to these bench tests??

There are quite a few interested people including me that would find this helpful as comparison for future purchases.


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: issdaol]
      #5870837 - 05/19/13 07:49 AM

Quote:

Quote:


There was a thread a while back that pitted a 250 Mewlon against the 10" AP and I picked the 10" AP on that one.

For that one, the Mewlon had a meaningfully bigger CO, but more importantly, the bench tests I have seen on Mewlons have led me to believe that they are not made to the same high level of perfection that you would get from either the AP or a custom mirror Dob.






Would appreciate if you can point us to these bench tests??

There are quite a few interested people including me that would find this helpful as comparison for future purchases.




Even a bit more off-topic, I have both a AP 10" f/14.6 Mak-Cass and a Tak Mewlon 300CR. If I couldn't get the former, I'd be quite pleased with the latter. They're both wonderful visual instruments for lunar, planetary, globular, and relatively bright DSOs (my 25" Newt is obviously better for viewing the fainter fuzzies).


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charles genovese
professor emeritus
*****

Reged: 02/04/06

Loc: Madisonville Louisiana
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: JJK]
      #5871317 - 05/19/13 12:49 PM

U guys r silly. A newt can equal any other design. I have esentilly perfect optics in both of my 10" newts -f/4.5 and f/6- and il put both up against th mak. They hav all th tricks and essentially perfect optics. There is no single secondary size for a newt. It depends on th field illumination u want and the distance prime focus is out. Both can have th mirror slide back or foreward 3" to give 1/2 " back focus for visual or planetary imaging and 3-4" out for deepsky imaging. The secondary is easily interchangable (same for my 16"f/4.5) and i have 1.8, 2.1, 2.6,3.1, 3.5, and 4" ers. For the 10"f/6 1/2 " back focus 1.8 " secondary gives 1/2 " of 100% illumination- usual setup. If i wanted to image deep sky i would move th primary foreward 3" and change to a 2.6 " secondary giving about 35mm of 100% illumination- gives roo
For a coma corrector and off axis guider. For the 10" f/4.5 the typical setup is 3" backfocus and a 2.6" secondary and it has about -5 mm of 100% illumination. For serious widefield imaging i would move th primary foreward another 1/2 inch and increase the secondary to 3.1.
Also whoever said something about th spider was wrong. The effect is insignificant. Btw a curved spider eliminates difraction spikes if it bothers u.
A subaperature corrector (coma corrector) is a lot easier to make than a full aperature mak corrector! And barlows are an integral part of all widefield short focal length eyepieces.
Sorry if aNy typos- out on my boat fishing lol


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charles genovese
professor emeritus
*****

Reged: 02/04/06

Loc: Madisonville Louisiana
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: charles genovese]
      #5871331 - 05/19/13 12:57 PM

Also - perfect optics for a newt is a LOT cheaper than a mak!
I also have fans , vent holes , flock , (btw baffles are unnecessary with modern flock).
There are a few other considerations- newts r more sensative to ground radiation- grass is best but if u cool cement slabs with water before observing its bettr.


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issdaol
member


Reged: 01/01/10

Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: JJK]
      #5872188 - 05/19/13 06:40 PM

Quote:

Quote:

Quote:


There was a thread a while back that pitted a 250 Mewlon against the 10" AP and I picked the 10" AP on that one.

For that one, the Mewlon had a meaningfully bigger CO, but more importantly, the bench tests I have seen on Mewlons have led me to believe that they are not made to the same high level of perfection that you would get from either the AP or a custom mirror Dob.






Would appreciate if you can point us to these bench tests??

There are quite a few interested people including me that would find this helpful as comparison for future purchases.




Even a bit more off-topic, I have both a AP 10" f/14.6 Mak-Cass and a Tak Mewlon 300CR. If I couldn't get the former, I'd be quite pleased with the latter. They're both wonderful visual instruments for lunar, planetary, globular, and relatively bright DSOs (my 25" Newt is obviously better for viewing the fainter fuzzies).




Sounds like a big investment there :-) How would you compare the views, build and optical quality of the Tak 300 against the AP and other top end scopes??


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: issdaol]
      #5872739 - 05/19/13 10:46 PM

Quote:

Quote:

Quote:

Quote:


There was a thread a while back that pitted a 250 Mewlon against the 10" AP and I picked the 10" AP on that one.

For that one, the Mewlon had a meaningfully bigger CO, but more importantly, the bench tests I have seen on Mewlons have led me to believe that they are not made to the same high level of perfection that you would get from either the AP or a custom mirror Dob.






Would appreciate if you can point us to these bench tests??

There are quite a few interested people including me that would find this helpful as comparison for future purchases.




Even a bit more off-topic, I have both a AP 10" f/14.6 Mak-Cass and a Tak Mewlon 300CR. If I couldn't get the former, I'd be quite pleased with the latter. They're both wonderful visual instruments for lunar, planetary, globular, and relatively bright DSOs (my 25" Newt is obviously better for viewing the fainter fuzzies).




Sounds like a big investment there :-) How would you compare the views, build and optical quality of the Tak 300 against the AP and other top end scopes??




It's hard to say. I don't often have them out together, but they're both excellent instruments. The AP Mak-Cass is lighter, looks sleeker, and has excellent thermal design. The Mewlon 300CR should have more reach, but I haven't critically tested them to see which one performs better visually with faint fuzzies. IMO, previously owned Mewlon 300 OTAs are bargains.

I also have an AP 175 f/8 apo (used to have an AP 180 f/9 EDT, but regrettably had to sell it, per the current CFO's orders). I'll be comparing the 175 and the AP Mak-Cass this Summer.


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: charles genovese]
      #5872748 - 05/19/13 10:49 PM

Quote:

U guys r silly. A newt can equal any other design. I have esentilly perfect optics in both of my 10" newts -f/4.5 and f/6- and il put both up against th mak. They hav all th tricks and essentially perfect optics. There is no single secondary size for a newt. It depends on th field illumination u want and the distance prime focus is out. Both can have th mirror slide back or foreward 3" to give 1/2 " back focus for visual or planetary imaging and 3-4" out for deepsky imaging. The secondary is easily interchangable (same for my 16"f/4.5) and i have 1.8, 2.1, 2.6,3.1, 3.5, and 4" ers. For the 10"f/6 1/2 " back focus 1.8 " secondary gives 1/2 " of 100% illumination- usual setup. If i wanted to image deep sky i would move th primary foreward 3" and change to a 2.6 " secondary giving about 35mm of 100% illumination- gives roo
For a coma corrector and off axis guider. For the 10" f/4.5 the typical setup is 3" backfocus and a 2.6" secondary and it has about -5 mm of 100% illumination. For serious widefield imaging i would move th primary foreward another 1/2 inch and increase the secondary to 3.1.
Also whoever said something about th spider was wrong. The effect is insignificant. Btw a curved spider eliminates difraction spikes if it bothers u.
A subaperature corrector (coma corrector) is a lot easier to make than a full aperature mak corrector! And barlows are an integral part of all widefield short focal length eyepieces.
Sorry if aNy typos- out on my boat fishing lol




I don't know why you replied to my post. I didn't knock Newtonians.


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azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: charles genovese]
      #5872777 - 05/19/13 11:02 PM

Nice post and points Charles.

Pete


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issdaol
member


Reged: 01/01/10

Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5872997 - 05/20/13 02:02 AM

Hi JJK,

Good to hear favorable comparisons from someone that actually owns and uses both AP and Tak scopes.

It seems like a lot of people put one or the other down without ever having owned both referring to vague tests and statements that are never validated or produced.

So based on the OP topic the Mewlon would stand up well against the AP Mak even though it is not f5??


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charles genovese
professor emeritus
*****

Reged: 02/04/06

Loc: Madisonville Louisiana
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: issdaol]
      #5873361 - 05/20/13 09:59 AM

Hi JJK- wasn't knocking you- just responded based on some things that were said. Rollands Mak is a spectacular instrument I'm sure, but for 1/10 (or less) one could have a comperable Newt. BTW, my most used scope is a C8 with excellent optics (that has vent holes-note the large amount of ventillation on the AP Mak!)

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azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: charles genovese]
      #5874460 - 05/20/13 07:06 PM

You know Charles its interesting that you have several secondary sizes and it would seem like the way it ought to be for everyone with fast newts. Like I said in the previous post you've made a lot of good points. Its easy enough just to switch it out based on the call of the evening. Had an f/5 been my instrument and long focus didn't exist Id have a number of secondaries.

And they are so relatively cheap!

Pete


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