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MAK Insulation

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#26 k5apl

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Posted 17 November 2018 - 10:39 PM

I had my Mak6 out for two nights at Eldorado Star Party with no tube current problems that I could see.  The comments I received after aligning my mount were "the stars look like refractor pin points"  and  "this is like looking through a refractor".  Comments were from seasoned observers.  Just a temperature swing, no dew.  This confirms to me that it works.  Thanks to Elwaine.


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#27 Paradoxdb3

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Posted 19 November 2018 - 12:47 PM

I definitely need to try this, as I live in apartment building, so no outside storage, and it gets to -30°C and even colder during the winter. From 22 to -30 is a big bummer!
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#28 Conaxian

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Posted 19 November 2018 - 03:08 PM

Fellows my mind is swimming from reading that long thread that got closed.  I have two questions about all this.. I intend to wrap my 5" Mak with reflectix over the tube, only.  I will be using a commercial dewcap that has black felt inside made of some sort of plastic.  The dewcap has 2" wide rubber where it meets the corrector cell, so I will count that as insulation for that cell. This leaves me with a simple job of wrapping just the tube and making cutouts for the dovetail and finder bracket.

Here's the first question- Around here the winter temp delta is from 35 to 45* F.  Do I need two layers of reflectix or would one do the job? My typical outing is no longer than two hours. 

The second question- Do I really need to wrap the dewcap? It would seem that it would cool very quickly to ambient anyway since it is open on the end.

Thanks in advance for any advice!



#29 Axunator

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Posted 19 November 2018 - 03:51 PM

Fellows my mind is swimming from reading that long thread that got closed. I have two questions about all this.. I intend to wrap my 5" Mak with reflectix over the tube, only. I will be using a commercial dewcap that has black felt inside made of some sort of plastic. The dewcap has 2" wide rubber where it meets the corrector cell, so I will count that as insulation for that cell. This leaves me with a simple job of wrapping just the tube and making cutouts for the dovetail and finder bracket.
Here's the first question- Around here the winter temp delta is from 35 to 45* F. Do I need two layers of reflectix or would one do the job? My typical outing is no longer than two hours.
The second question- Do I really need to wrap the dewcap? It would seem that it would cool very quickly to ambient anyway since it is open on the end.
Thanks in advance for any advice!


My answer to both of your questions: Try it out yourself and see. Even better: after experimenting, tell us here what you found.

And I’m not being sarcastic or unhelpful. These experiments are neither expensive nor difficult. Heck, they could even be fun.

If I were in your shoes, I’d start by adding a single layer on the OTA and use the existing plastic dewcap as it is. If you still have thermal problems, increase the insulation step by step, observe and see what happens.

It’s also likely that the amount needed varies depending on conditions on a given night. And 5” is not a big scope, so thermals are likely tamed more easily than for larger ones.
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#30 carolinaskies

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Posted 19 November 2018 - 04:27 PM

When those temperatures not that's not particularly cold so one layer likely will be enough. I would suggest first using the insulation as the dew shield extending it about 4-6 inches beyond the tube. not even worrying about your current dew shield that way you don't have to make any unnecessary modifications as you may find that it does the entire job.

Remember the concept here is to slow down any cooling and that can include the dew shield.
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#31 Conaxian

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Posted 19 November 2018 - 05:03 PM

I was going to try just one layer first and add more if it wasn't enough.  I was originally going to use the reflectix for a dewcap, but the need to darken it inside, and the problem of my small storage/carrying bag would not allow a floppy long reflectix dew cap to remain un-rumpled caused me to buy the commercial dewcap. (It's one of those Zap things).  It has a rubber ring for the cell and is already lined with felt (can't beat that for stray light protection).

I had good performance with one for the old 6" Mak I sold off.

Anyway, thanks guys. Now I have a plan.  I don't do anything without a plan first.

Thanks to both of you that replied, and to anyone else that has input for me.

wink.gif



#32 dweller25

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Posted 20 November 2018 - 05:21 AM

@conaxian

 

I tried one layer of reflectix on my C6 and it did not work - two did though waytogo.gif


Edited by dweller25, 20 November 2018 - 05:21 AM.

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#33 Paradoxdb3

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Posted 20 November 2018 - 02:35 PM

I threw on two layers, as I was using a 4"x25' roll, meaning there are four seams along the OTA. The second layer overlapped these seams, covering up any gaps. I also covered the rear cell with one layer of reflectix.
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#34 Conaxian

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Posted 20 November 2018 - 04:24 PM

Due to my sloven and lazy nature I will just go ahead and do two wraps for a clean job. The roll I have my eye on is 16" by 25' so it will be easy as pie to go round twice and call her done. 

The scope is stored at 70*F, winter nights are usually 0 to 35*F around here. Two wraps are probably for the best.

I think this is a great idea for closed tube scopes. I bet some manufacturer is already planning tubes with insulation either inside or out.

I appreciate all the advice. This is the best astronomer's forum I've found. Thanks for letting me in!



#35 Bean614

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Posted 20 November 2018 - 10:10 PM

@conaxian

 

I tried one layer of reflectix on my C6 and it did not work - two did though waytogo.gif

A 6" SCT, no matter where on the Planet it is being used, should not need more than one layer of Reflectix.  

   Are you wrapping it INDOORS, before you take it out?  Even with a Delta of 60f (70f inside, and 10f outside) you should have sharp views immediately.  Like wearing your own winter coat, you put it on inside, BEFORE you go out.  And there is no need to set it out early, as you're trying NOT to cool it!  Good luck!


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#36 dweller25

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Posted 21 November 2018 - 05:05 AM

A 6" SCT, no matter where on the Planet it is being used, should not need more than one layer of Reflectix.  

   Are you wrapping it INDOORS, before you take it out?  Even with a Delta of 60f (70f inside, and 10f outside) you should have sharp views immediately.  Like wearing your own winter coat, you put it on inside, BEFORE you go out.  And there is no need to set it out early, as you're trying NOT to cool it!  Good luck!

Thanks for that but as I said two layers works for me in my conditions.

 

I'm assuming you have tried the Reflectix on a C6 ? so your conditions may be different to mine.

 

But whether it's one layer or two the difference is probably less than a dollar in cost and you have to buy more than you need anyway - so there is nothing to lose

 

I have never suggested that the scope should be set out early to cool - that is counter intuitive - the whole point is that the OTA maintains internal thermal equilibrium when exposed to the cooler outside air.

 

A second plus point is that because the internal temperature in the OTA is higher then the external temperature, it takes much longer for the corrector to dew up.


Edited by dweller25, 21 November 2018 - 05:12 AM.

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#37 Bean614

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Posted 21 November 2018 - 05:17 AM

"I'm assuming you have tried the Reflectix on a C6 ?"

 

Yes, quite a few actually.  And, including Maks & SCT's of all sizes, I've used Reflectix on approximately 22 scopes.



#38 dweller25

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Posted 21 November 2018 - 06:50 AM

"I'm assuming you have tried the Reflectix on a C6 ?"

 

Yes, quite a few actually.  And, including Maks & SCT's of all sizes, I've used Reflectix on approximately 22 scopes.

Excellent waytogo.gif



#39 Steve D.

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Posted 21 November 2018 - 08:36 PM

Just to add to the growing evidence of the effectiveness of this approach, I took my C8 from the 71 degree house to an outside temperature of 43 degrees and couldn't see any thermals then or 40 minutes later.   I was immediately able to see the Airy disk of Polaris and could crank up the power to 300X on the moon.  This stayed consistent the entire time I was out there.   The temp dropped another 1/2 degree while I was outside.

 

I have two layers on the tube and one layer on the dew shield as well.


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#40 Conaxian

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Posted 23 November 2018 - 02:13 AM

Mine now has one layer on the tube- (and nothing else). First chance I get I'll take it out and see how it does. I'll use my new AstroZap dewcap also.  If it needs more it will be easy to add, no sweat.

It was easier for me than wrapping Christmas presents.



#41 pferendzo

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Posted 23 November 2018 - 06:16 AM

I have a 150mm Orion MCT that never seemed to live up to my expectations... collimation is good, but the environment in the St Louis metro makes observing challenging. Reading the posts on insulating the OTA vs. temperature equilibrium has convinced me to give the 150mm another try... Guess I'll also replace the attached dovetail with rings while I'm at it. 



#42 Conaxian

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Posted 25 November 2018 - 01:10 AM

The sky tonight is full of water vapor, ice particles higher up, and some high, thin clouds.

Since it wasn't clouded over (rare) I took it out for a little bit. From 70F inside to 40F outside. The haze lit up by the moon was like pale soup. But I did get a look at a couple of stars. The faint ones were fairly sharp and tiny, nearly lost in the glare.  The brighter ones were blobbish.  I checked for currents and didn't see any plumes.  After I brought it in I tried to gauge the temp of the scope.  The rear cell was noticably warmer than the finder bracket.  I think it will be enough insulation for my short looks outside in winter. 

The little mak didn't get a chance to strut its stuff with all the soup and glare. I checked the moon, the detail along the narrow terminator showed well, some low contrast, small craterlets were easily seen, low (39x) to medium power (100x) was ok. I didn't push it at all. 


Edited by Conaxian, 25 November 2018 - 01:18 AM.


#43 yellobeard

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Posted 25 November 2018 - 03:25 AM

That will depend on your climate. Some folks have reported having no dew problems with just the OTA covered. IIRC, Yellobeard, the fellow who started this topic a while back, lives in Norway(?) and insulates the dew shield.



Uhh almost right... He lives in the Netherlands!
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#44 elwaine

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Posted 25 November 2018 - 01:58 PM

Uhh almost right... He lives in the Netherlands!

Apologies, Yellobeard. (At least I got the first letter right. smile.gif ) But regardless of country of origin, you started a trend that many of us thank you for!


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#45 dscarpa

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Posted 27 November 2018 - 07:40 PM

 If I do that with my IM715D I'm making a matching hat. David



#46 Moe24

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Posted 03 December 2018 - 12:52 PM

There is a beauty in practicality that transcends the superficial.

I have used my Just-Cheney dew shield on my Mak66 for 17 years! Dew what’s that?



#47 Jaimo!

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Posted 03 December 2018 - 07:24 PM

I have used my Just-Cheney dew shield on my Mak66 for 17 years! Dew what’s that?

Tell me more of this Just-Cheney dew shield and where can I get one, or what size, for my MK67?

 

Thanks,

Jaimo!



#48 Moe24

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Posted 04 December 2018 - 04:17 PM

Tell me more of this Just-Cheney dew shield and where can I get one, or what size, for my MK67?

 

Thanks,

Jaimo!

 

Jaime  the Just-Cheney dew shield is no longer produced . You can find one like it at Anacortes Telescope under name of Dew MASTER! Hope this helps



#49 Jaimo!

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Posted 04 December 2018 - 05:56 PM

That's unfortunate, I don't usually buy from Anacortes.

 

Jaimo!



#50 Reid W

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Posted 04 December 2018 - 07:06 PM

That's unfortunate, I don't usually buy from Anacortes.

 

Jaimo!

 

Wow. Why is it unfortunate?  

 

It think that is is great that the item is still available.  In the small niche market I would assume that not all enterprises even if successful,  can last. 




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