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Benefits of a 102mm Achromat refractor over a 127mm MAK?

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#26 sojourneyer

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Posted 02 August 2021 - 02:45 PM

I certainly understand Barbie.

For that reason my scopes are all under 6 lbs and with the exception of my Twilight 1 my other mount is also about 5 lbs

 

I do recall when I had the orion mak 90 that I could carry the entire unit in one hand and my bag of EPs, etc across my shoulder.. Those were the good old days!


Edited by sojourneyer, 02 August 2021 - 04:55 PM.

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#27 barbie

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Posted 02 August 2021 - 03:28 PM

Thanks Sojourneyer!! There is definitely a lot to be said in favor of lightweight and easy portability!!!
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#28 Echolight

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Posted 02 August 2021 - 04:57 PM

I really would not think a 90mm Mak would have any major cooling down issues given their small size.   But you can not enjoy DSOs like you do with your 80ED

Agreed. I didn’t say they could do everything the ED80 does. But it is fun to use a tiny scope that’s still 3.5 inches.



#29 sojourneyer

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Posted 02 August 2021 - 05:18 PM

I had a Celestron 127 for a while a few years back. On my Porta II it was a nice, compact package that was easy to pick up and move around anywhere on the deck or in the yard. I thought it would be the epitome of convenience. Dew and stray light were easy to manage with a homemade dew shield, but it had thermal issues that were far worse than the C5, and Meade 6 that I had at the time; even worse than either of the C8 SCTs that I had before and after. I gave up dealing with it in about a year and sold it. You could literally sense the heat plumes rising off the primary and pulsating through the air in the tube. It ruined detailed planetary view for me. I’ve never seen anything like that in my Questar 3.5”; it’s ready for viewing almost immediately after setup. Same with an old C90 Mak I had. Those two acted just like refractors of the same aperture. The 127mm Synta Mak was different for sure! It still wasn’t ready after an hour, and would sometimes have issues all evening. That’s what cured me of a desire for larger Maks.

I had the same feeling as you. I could never get detailed planetary viewing from my 3 127 Synta Maks.  And I had the rascally units prepped from 1.5- 2 hrs before viewing.  Also as you said the views from the little 90 were just as good or even better. That always bewildered me.

So frustrating.  Thanks for sharing.

 

 

 

 


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#30 treadmarks

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Posted 02 August 2021 - 05:40 PM

I had a Celestron 127 for a while a few years back. On my Porta II it was a nice, compact package that was easy to pick up and move around anywhere on the deck or in the yard. I thought it would be the epitome of convenience. Dew and stray light were easy to manage with a homemade dew shield, but it had thermal issues that were far worse than the C5, and Meade 6 that I had at the time; even worse than either of the C8 SCTs that I had before and after. I gave up dealing with it in about a year and sold it. You could literally sense the heat plumes rising off the primary and pulsating through the air in the tube. It ruined detailed planetary view for me. I’ve never seen anything like that in my Questar 3.5”; it’s ready for viewing almost immediately after setup. Same with an old C90 Mak I had. Those two acted just like refractors of the same aperture. The 127mm Synta Mak was different for sure! It still wasn’t ready after an hour, and would sometimes have issues all evening. That’s what cured me of a desire for larger Maks.

Yeah, this is what scares me off of 5" Maks. This, and their extra weight makes them worse on a tripod. Nowadays we have the insulation idea. For what it's worth, I don't really notice these issues with my 4" Mak.

 

To relate this to a 102mm achromat, I'd say this: every scope needs a cooldown period. I once took my 4" refractor straight out into a cold night and pointed it at Saturn. It looked like it was underwater. So unless it's an insulated Cassegrain, every scope needs to be cooled first for optimal high power usage.


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#31 barbie

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Posted 02 August 2021 - 06:16 PM

I agree with all of those points!!



#32 sojourneyer

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Posted 02 August 2021 - 07:59 PM

Yeah, this is what scares me off of 5" Maks. This, and their extra weight makes them worse on a tripod. Nowadays we have the insulation idea. For what it's worth, I don't really notice these issues with my 4" Mak.

 

To relate this to a 102mm achromat, I'd say this: every scope needs a cooldown period. I once took my 4" refractor straight out into a cold night and pointed it at Saturn. It looked like it was underwater. So unless it's an insulated Cassegrain, every scope needs to be cooled first for optimal high power usage.

what temps were you dealing with? 



#33 treadmarks

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Posted 02 August 2021 - 10:04 PM

what temps were you dealing with? 

Oh it was around 25 F and 4 AM, so it had some bite to it. I did not want to wait around for the scope to cool down.



#34 vtornado

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Posted 02 August 2021 - 10:52 PM

In lunar and planetary viewing I have this following sharpness experience.

 

5 inch mak = 4 inch ED refractor > 5 inch newt > 5 inch SCT > 4 inch f/10 achro.  YMMV

 

however .. the difference is close, and

 

I have a sample size of one for each scope.

Due to a range of focal lengths from 1500 - 650 I cannot use the same eyepiece.

The newt does not use a diagonal.

The 5 inch newt and 4 inch achro tubes can be bought for $100 - $150 used.

I live in the midwest with frequent bad seeing and seeing that can change quickly.


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