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Roland's 10" Mak versus a 10" f/5 reflector

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#51 JJK

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Posted 19 May 2013 - 06:49 AM


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).

#52 charles genovese

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Posted 19 May 2013 - 11:49 AM

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

#53 charles genovese

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Posted 19 May 2013 - 11:57 AM

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.

#54 issdaol

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Posted 19 May 2013 - 05:40 PM


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??

#55 JJK

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Posted 19 May 2013 - 09:46 PM


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.

#56 JJK

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Posted 19 May 2013 - 09:49 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


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

#57 azure1961p

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Posted 19 May 2013 - 10:02 PM

Nice post and points Charles.

Pete

#58 issdaol

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Posted 20 May 2013 - 01:02 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??

#59 charles genovese

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Posted 20 May 2013 - 08:59 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!)

#60 azure1961p

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Posted 20 May 2013 - 06:06 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

#61 JJK

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Posted 20 May 2013 - 07:21 PM

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!)


Ok, thanks. I don't mind criticism, as long as it's accurate and constructive.

Roland's 10" Mak-Cass was "only" $10K new (I shudder at what it might fetch now). Are top-notch 10" f/5 Newtonians selling for less than $1K new? That'd be a lot of bang for the buck.

I've used C8s, C9.25s, and C11s. IMO, they're incredible bargains (and some day, I'd love to get a cherry-picked C14). However, none of them were as well made (optically & mechanically) as the AP, they didn't perform as well on lunar/planetary views, and are not as versatile (the AP can be used visually at much higher magnification).

With the AP Mak-Cass, I've seen extremely fine lunar features (e.g., the entire length of Rima Marius, not just the part drawn in Rukl's atlas). There's no way any SCT I've ever used could have performed that well (FWIW, an AP155 f/7 EDF failed to show the finest part of the Rima that night). I wish I had the Tak Mewlon 300CR back them. It would have been a very interesting and critical comparison.

#62 JJK

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Posted 20 May 2013 - 07:25 PM

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??


I think the Tak Mewlon 300CR performs extremely well. I'd recommend one to anyone whose seeing can support it, even if only occasionally.

#63 charles genovese

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Posted 21 May 2013 - 07:35 PM

Minor correction- I pulled out the calculations and the field of 100% illumination for the 10" f/4.5 with th 2.6" diagonal and the focal plane 12" from the optical axis (6" from the tube or 4" of back focus from the focuser) is about .6" or 15mm, (not 5 as I wrote).






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