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Which acclimates faster, a 150 mak or an 8” SCT

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#1 Dave Ponder

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Posted 09 June 2021 - 09:32 AM

Just curious which one would thermally stabilize first when taken from inside the house and set up outside.  What do you think?



#2 KTAZ

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Posted 09 June 2021 - 09:39 AM

Well, since you are asking for an opinion, I doubt there would be a great deal of difference. To my knowledge, the corrector in the Mak is thicker than that of the SCT, therefore even with the smaller aperture, it might not cool as quickly as you expect.


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#3 wrvond

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Posted 09 June 2021 - 09:40 AM

While the Mak has a thicker corrector plate than the Schmidt, both the corrector glass and the mirror are about 2" smaller in diameter. Because of the smaller mass of glass overall, I'd imagine the Mak would stabilize sooner.



#4 pyrasanth

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Posted 09 June 2021 - 09:40 AM

My guess would be the SCT as its not just about mirror area but the amount of glass- the MAC has a very thick meniscus which can take time to thermally settle- I believe thicker than the SCT corrector plate.



#5 pyrasanth

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Posted 09 June 2021 - 09:41 AM

Do we get a prize if we guess correctly?


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#6 Dave Ponder

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Posted 09 June 2021 - 09:44 AM

Do we get a prize if we guess correctly?

Lol!  I don’t know the correct answer...I am thinking it may be a toss up...



#7 Sarkikos

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Posted 09 June 2021 - 09:54 AM

Just curious which one would thermally stabilize first when taken from inside the house and set up outside.  What do you think?

I have a 150mm Mak and an EdgeHD 8" SCT.  In my experience, the EdgeHD 8" SCT acclimates faster, even with the additional optics in the rear port.  The 150mm Mak is also heavier!

 

Mike


Edited by Sarkikos, 09 June 2021 - 09:55 AM.

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#8 jeremiah2229

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Posted 09 June 2021 - 10:02 AM

The 150 Mak settles faster, I use both here. No contest, the 150 will take 30 minutes for example going from a 68 degree house out to 45-50 degree air. The C8 is in the 60-90 minute range. This is when no plumes present. In warmer summer air the C8 has the propensity to dew over much quicker. I use dew shields only, no heaters.

 

 

Peace...


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#9 Old Speckled Hen

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Posted 09 June 2021 - 10:34 AM

  Is somebody buys me a 150 mak I'll do a comparison, insulated and uninsulated 'natch.... meditation.gif


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#10 Traveler

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Posted 09 June 2021 - 10:42 AM

Faster? Less slow.


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#11 junomike

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Posted 09 June 2021 - 11:15 AM

It can depend on the specific Mak or SCT.

An Intense 6" Mak is built like a tank and will take longer than an Orion Mak of the same size.

 

Same for an SCT as the older one's had a thicker housing.

 

All in all however It's a wash.The difference shouldn't be enough to really matter


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#12 Sarkikos

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Posted 09 June 2021 - 11:30 AM

It can depend on the specific Mak or SCT.

An Intense 6" Mak is built like a tank and will take longer than an Orion Mak of the same size.

 

Same for an SCT as the older one's had a thicker housing.

 

All in all however It's a wash.The difference shouldn't be enough to really matter

My 6" Mak is a Bosma Rumak.  Yes, thick, heavy and built like a tank.  By comparison, the EdgeHD 8" appears to have a relatively thin body.  As I said, my 6" Mak is actually heavier than the EdgeHD 8".

 

The 6" Bosma Rumak definitely takes longer to acclimate than the EdgeHD 8".  

 

Neither OTA has the Reflectix insulation installed.  I have no idea what difference insulation would make in the comparison.

 

Mike



#13 Sarkikos

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Posted 09 June 2021 - 11:31 AM

The 150 Mak settles faster, I use both here. No contest, the 150 will take 30 minutes for example going from a 68 degree house out to 45-50 degree air. The C8 is in the 60-90 minute range. This is when no plumes present. In warmer summer air the C8 has the propensity to dew over much quicker. I use dew shields only, no heaters.

 

 

Peace...

Which 150 Mak?

 

Mike


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#14 Bean614

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Posted 09 June 2021 - 03:57 PM

With Insulation,  the times would be identical, as both could be used immediately, with no thermals,  and perfect views.

The last time I  owned both of these scopes at the same time,  and without insulation,  was in 2016, and I  actually DID do a thorough comparison,  right down to cooling time. It was in the Fall, in New England,  70F inside / 55 outside, when I set them out at Sunset.

One hour later, it was 45F outside, and each required another 20---30 minutes to be sufficiently cooled to ambient.  


Edited by Bean614, 09 June 2021 - 04:05 PM.


#15 Old Speckled Hen

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Posted 09 June 2021 - 04:22 PM

My 6" Mak is a Bosma Rumak.  Yes, thick, heavy and built like a tank.  By comparison, the EdgeHD 8" appears to have a relatively thin body.  As I said, my 6" Mak is actually heavier than the EdgeHD 8".

 

The 6" Bosma Rumak definitely takes longer to acclimate than the EdgeHD 8".  

 

Neither OTA has the Reflectix insulation installed.  I have no idea what difference insulation would make in the comparison.

 

Mike

Now that's an interesting point; would the greater mass of the mak have a different rate of cool down, preferably slower, than the featherweight sct if both are insulated. 

 

That's a VERY interesting ..challenge.  sct.png sct2.png


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#16 Asbytec

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Posted 09 June 2021 - 04:56 PM

Interesting exercise in understanding (or not understanding) how a scope cools. Allow me to embarrass myself by guessing. I guess it depends on the surface area and conductivity of the tube, the mass of the primary mirror and it's assembly, and even the type of glass used in the mirror and correctors. 

 

The tube and corrector cool by radiating to the sky. Some of the air along the tube conducts heat the the tube. It begins to fall through the OTA as warmer air rises causing some thermal instability and differences in air density. This is why insulation is effective, it largely slows the radiation cooling to the sky inhibiting thermals from forming within the tube. Air, to my understanding, is not a very good conductor. So the greater volume of air in a larger tube should take a little longer to reach equilibrium, possibly offset some by the larger surface area of the tube exposed to the sky. The MCT tube may be more massive, but it's also exposed to the sky and is a conductor.

 

The enclosed primary mirror and assembly does not have the luxury of radiating to the sky. I believe it primarily conducts heat as the tube cools, both to the inside air (non conductor) and the tube (a conductor). So, a more massive mirror assembly may cool more slowly. In my experience, the thicker meniscus does seem to retain some heat as evidenced by less dew problems, in my experience and climate, relative to the thin Schmidt corrector. That's a good thing. I have not really noticed any ill effects from a slightly warm meniscus. Not compared to the damage internal thermal instability causing the heat plume primarily emanating from the massive primary assembly. 

 

My guess is the less massive MCT should cool a little faster. My out is to caveat that by saying, YMMV. smile.gif


Edited by Asbytec, 09 June 2021 - 05:00 PM.

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#17 Dave Ponder

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Posted 09 June 2021 - 07:31 PM

Thanks guys for your input.  There seems to be no definitive answer so far.  I have both a 150 mak ota and a Celestron 8 inch SCT ota.  Was thinking of selling the one that takes the longest to acclimate since both have really good optics.  I only recently acquired a second mount, but have not had a good night to compare one to the other.  Tough call....



#18 jeremiah2229

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Posted 09 June 2021 - 08:49 PM

Which 150 Mak?

 

Mike

Orion.



#19 speedster

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Posted 09 June 2021 - 10:00 PM

Too many variables to answer but, when has that stopped anyone?  The heaviest will take longer as specific heat is a function of mass.


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#20 Sarkikos

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Posted 10 June 2021 - 05:16 AM

With Insulation,  the times would be identical, as both could be used immediately, with no thermals,  and perfect views.

The last time I  owned both of these scopes at the same time,  and without insulation,  was in 2016, and I  actually DID do a thorough comparison,  right down to cooling time. It was in the Fall, in New England,  70F inside / 55 outside, when I set them out at Sunset.

One hour later, it was 45F outside, and each required another 20---30 minutes to be sufficiently cooled to ambient.  

Which 150 Mak?  Which 8" SCT?

 

Mike



#21 Sarkikos

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Posted 10 June 2021 - 05:17 AM

Orion.

Case in point.  I bet if the 150 Mak had been a Bosma - like mine - or one of the Russian models, it would have acclimated more slowly than the 8" SCT.

 

Mike



#22 Sarkikos

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Posted 10 June 2021 - 05:20 AM

Interesting exercise in understanding (or not understanding) how a scope cools. Allow me to embarrass myself by guessing. I guess it depends on the surface area and conductivity of the tube, the mass of the primary mirror and it's assembly, and even the type of glass used in the mirror and correctors. 

 

The tube and corrector cool by radiating to the sky. Some of the air along the tube conducts heat the the tube. It begins to fall through the OTA as warmer air rises causing some thermal instability and differences in air density. This is why insulation is effective, it largely slows the radiation cooling to the sky inhibiting thermals from forming within the tube. Air, to my understanding, is not a very good conductor. So the greater volume of air in a larger tube should take a little longer to reach equilibrium, possibly offset some by the larger surface area of the tube exposed to the sky. The MCT tube may be more massive, but it's also exposed to the sky and is a conductor.

 

The enclosed primary mirror and assembly does not have the luxury of radiating to the sky. I believe it primarily conducts heat as the tube cools, both to the inside air (non conductor) and the tube (a conductor). So, a more massive mirror assembly may cool more slowly. In my experience, the thicker meniscus does seem to retain some heat as evidenced by less dew problems, in my experience and climate, relative to the thin Schmidt corrector. That's a good thing. I have not really noticed any ill effects from a slightly warm meniscus. Not compared to the damage internal thermal instability causing the heat plume primarily emanating from the massive primary assembly. 

 

My guess is the less massive MCT should cool a little faster. My out is to caveat that by saying, YMMV. smile.gif

Yes, if the specific MCT is actually less massive.

 

Mike



#23 Bean614

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Posted 10 June 2021 - 05:23 AM

The Orion 6" Mak (Synta) from 2016, (with the 'standard' SCT Threads on the Rear Cell); and the Celestron (Synta) 'Evolution' 8-Inch SCT OTA (identical, as I'm sure you MUST know, to the Celestron SE, CPC, AVX, etc.,   'Labelled' 8-inch SCT's from Celestron/Synta, with XLT Coatings.  Need more info????


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#24 Sarkikos

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Posted 10 June 2021 - 05:27 AM

The Evolution 8" is an EdgeHD 8" on an Evolution mount.  It irks me when the companies name their scopes by the mounts they ride on, rather than by the OTA.  fingertap.gif

 

Mike



#25 Bean614

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Posted 10 June 2021 - 07:12 AM

The Evolution 8" is an EdgeHD 8" on an Evolution mount.  It irks me when the companies name their scopes by the mounts they ride on, rather than by the OTA.  fingertap.gif

 

Mike

Mike, the Evolution 8" on the Evo Mount comes in BOTH the 'Standard' SCT configuration AND the EDGE configuration.  I have had BOTH, and had them several times over.  I am VERY familiar with them.  The 'standard' Evo-8 OTA is simply a 'standard' C8, same as all the others.  The only difference is the StarBright/XLT Coatings which came standard on all  models produced after 2005, (and a few before that, notably some of the NexStar GPS models) as opposed to just the Starbright coatings.  Of course, if you wish, we can go back to the 70's, when there was no mention of a type of coating, save for the 'Special Coatings', which were a purchased option.  Anything else?




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