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Insulating my SW 180 Mak.

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#1 GUS.K

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Posted 26 August 2018 - 06:17 AM

Spent today making an insulating jacket for my SW 180 Mak, got the insulation from a builder friend and purchased some velcro, all told about an hours work. Hopefully get to try it out in the next couple of days(cloudy at the moment).Here are a few pics of it suited up.

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#2 elwaine

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Posted 26 August 2018 - 07:06 AM

Looks good. I’ve used an insulation jacket and it certainly did the trick: no need to wait for cool down, and no dew on the meniscus in spite of high humidity. 

 

Looking forward to learning about your own results. 


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#3 Traveler

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Posted 26 August 2018 - 07:15 AM

If your insulation works with your sw180 Mak, then for me the biggest factor against these Mak's is solved (imo).

Yep,also looking forward to your results!

 

(edit typo)


Edited by Traveler, 26 August 2018 - 07:16 AM.

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#4 dweller25

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Posted 26 August 2018 - 02:59 PM

It’s worked with my C6

Look forward to your results .......
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#5 yellobeard

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Posted 26 August 2018 - 04:24 PM

Looks very very good Gus!

It also works great on my C6... And My C8, my two C11's, C90, C14, and of course on my 16" SCT..
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#6 GUS.K

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Posted 26 August 2018 - 04:47 PM

Thanks for the comments guys, Usually I set the Mak up a few hours before I observe to let it acclimatise, but with the unpredictable weather we are having at the moment I’m hoping this will allow me to be able to set up and use the setup straight away. 



#7 dweller25

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Posted 26 August 2018 - 07:38 PM

Thanks for the comments guys, Usually I set the Mak up a few hours before I observe to let it acclimatise, but with the unpredictable weather we are having at the moment I’m hoping this will allow me to be able to set up and use the setup straight away.


That is exactly what I found - and an added benefit is the corrector stays dew free much longer
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#8 GUS.K

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Posted 28 August 2018 - 09:22 AM

So, got a chance tonight to try it out, and it worked perfectly, used it on Saturn and Mars, and a little while later on the moon once it cleared some distant trees. I was surprised how good the view was straight off, and stayed that way for the next 3 and a half hours, with no dewing of the meniscus. Normally I can see the heat plume from the internal baffle if I defocus but it was absent tonight. So this does work, and the small outlay for the material is worth it to be able to set up the scope and use it straight away, especially for short sessions.
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#9 bobhen

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Posted 28 August 2018 - 09:39 AM

So, got a chance tonight to try it out, and it worked perfectly, used it on Saturn and Mars, and a little while later on the moon once it cleared some distant trees. I was surprised how good the view was straight off, and stayed that way for the next 3 and a half hours, with no dewing of the meniscus. Normally I can see the heat plume from the internal baffle if I defocus but it was absent tonight. So this does work, and the small outlay for the material is worth it to be able to set up the scope and use it straight away, especially for short sessions.

Can you tell us what the temperature difference was between inside and outside?

 

Thanks.

 

Bob


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#10 Usquebae

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Posted 28 August 2018 - 12:41 PM

Can you tell us what the temperature difference was between inside and outside?

 

Thanks.

 

Bob

I'm interested also to know people's experience with this.  Throughout my long winter the differential is typically 50 degrees F or more, sometimes 70+ degrees.  Even insulated I may need to keep the OTA in a bin in the garage.


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#11 GUS.K

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Posted 28 August 2018 - 03:35 PM

Indoor temp was 20 degrees C(68deg F)( heating unit thermostat reading) and outside temp was -2 degrees C (28 degrees F)(local weather forecast).


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#12 Joe1950

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Posted 28 August 2018 - 04:01 PM

Great information, Gus! I have all the materials and just have to make the overcoat!


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#13 Rock22

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Posted 28 August 2018 - 04:11 PM

I'm interested also to know people's experience with this. Throughout my long winter the differential is typically 50 degrees F or more, sometimes 70+ degrees. Even insulated I may need to keep the OTA in a bin in the garage.

My 180mm mak and dew shield are insulated with two layers (except for the rear cell), and I have had no problems this summer or last winter, when temperature differentials were 30-40 degrees Fahrenheit between indoor and outdoors. The outer layer on the main tube is removable, so I can use one layer. This helps with mounting. The dew shield is one long piece rolled onto itself to make two layers, so that stays as is in all observing sessions for me.

Insulation is the best low-cost fix I’ve ever come across. Thanks, yellobeard!

And good job on the insulation, Gus.K!

Edited by Rock22, 28 August 2018 - 04:14 PM.

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#14 Bean614

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Posted 28 August 2018 - 10:35 PM

"Even insulated I may need to keep the OTA in a bin in the garage.".  Wrong!

It appears that you are still thinking in terms of "equalizing" temps, or 'acclimating' to outside temps, reaching 'ambient' temperature.  Forget (!!!) all those terms, and forget the word ''Cooling'.  The whole idea with Insualtion is to KEEP in the heat the tube had when it was inside your warm home!  And, with the insulation on the tube, the tube when outside cools, but VERY, VERY slowly, thus NOT creating internal air currents, which are what cause the issues in the first place (when you take a 72-degree tube and bring it out into 20-degree air, and the tube RAPIDLY cools, causing air currents).

   Here in New England we regularly see Delta's of 50, 60, and 70 degrees.  And NO problems when the tube has been insulated with Reflectix BEFORE bringing outside.


Edited by Bean614, 29 August 2018 - 05:12 AM.

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#15 Traveler

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Posted 28 August 2018 - 11:09 PM

Indoor temp was 20 degrees C(68deg F)( heating unit thermostat reading) and outside temp was -2 degrees C (28 degrees F)(local weather forecast).

That looks very very promising...


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#16 astrobeast

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Posted 29 August 2018 - 08:37 AM

"Even insulated I may need to keep the OTA in a bin in the garage.".  Wrong!

It appears that you are still thinking in terms of "equalizing" temps, or 'acclimating' to outside temps, reaching 'ambient' temperature.  Forget (!!!) all those terms, and forget the word ''Cooling'.  The whole idea with Insualtion is to KEEP in the heat the tube had when it was inside your warm home!  And, with the insulation on the tube, the tube when outside cools, but VERY, VERY slowly, thus NOT creating internal air currents, which are what cause the issues in the first place (when you take a 72-degree tube and bring it out into 20-degree air, and the tube RAPIDLY cools, causing air currents).

   Here in New England we regularly see Delta's of 50, 60, and 70 degrees.  And NO problems when the tube has been insulated with Reflectix BEFORE bringing outside.

This is a really interesting thread! Let me offer a few thoughts of my own on what I believe are the processes in play.

 

I don’t think there is anything inherently advantageous to having the tube start at the warm room-temp air of the house. More generally, what we desire is to keep a thermally stable tube from being exposed to cooler temperatures at the tube boundary which sets up internal currents. This is what the insulation is doing. If the insulation was perfect, the telescope would come back into the house with the same internal temp it went out with. But of course, it will in fact slowly cool at a rate that is determined by two things; 1) the temp difference between either side of the insulation and 2) the thermal conductivity of the insulation. I would argue then that a telescope that is thermally stable with a temperature closer to the expected outside ambient would be more ideal as the lower temperature gradient across the insulation will mean the differential cooling will be even less. Why “stress” the insulation by having a very large temperature differential across the boundary.

 

To summarize, I think what you want to start with is a thermally uniform telescope (material and internal air) that is wrapped in insulation. When you take this into a cooler environment, the insulation prevents cooling at the tube boundary. I think the physics argues that it if the insulation was perfect, it doesn’t really matter what the difference between the telescope and external air.  But given it is not, the closer the temp of the telescope is to the cooler outdoor air, it would seem inherently the better off you are. Additionally, it would seem be extension that you are in a better position to deal with falling outdoor temperatures which work to increase the temperature differential across the thermal boundary.

 

Anyway, hope this is clear and look forward to any comments. Again, great thread as this really seems to the “too good to be true” answer, which actually isn’t!

Rick


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#17 astrobeast

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Posted 29 August 2018 - 09:00 AM

This is a really interesting thread! Let me offer a few thoughts of my own on what I believe are the processes in play.

 

I don’t think there is anything inherently advantageous to having the tube start at the warm room-temp air of the house. More generally, what we desire is to keep a thermally stable tube from being exposed to cooler temperatures at the tube boundary which sets up internal currents. This is what the insulation is doing. If the insulation was perfect, the telescope would come back into the house with the same internal temp it went out with. But of course, 

Just a quick note. I offered this discussion not to refuting anything anyone has said. If peoples experience is that the insulation is effective even with 70 deg temperature differentials, than great!, there is no need to try to stabilize it at a temp closer to outdoor. I wrote this mainly as an exercise for me (and others) to see if I had a grasp on the physics at play.

 

Again, this just seems so much simpler than all the fans and hoops that people have had to jump through to solve this issue. If it is really as simple as this, this is really nothing short of revolutionary and will completely change the experience of users of SCT and MCT type scopes in climates with large temperature issues.

 

Rick


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#18 Usquebae

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Posted 29 August 2018 - 09:06 AM

"Even insulated I may need to keep the OTA in a bin in the garage.".  Wrong!

It appears that you are still thinking in terms of "equalizing" temps, or 'acclimating' to outside temps, reaching 'ambient' temperature.  Forget (!!!) all those terms, and forget the word ''Cooling'.  The whole idea with Insualtion is to KEEP in the heat the tube had when it was inside your warm home!  And, with the insulation on the tube, the tube when outside cools, but VERY, VERY slowly, thus NOT creating internal air currents, which are what cause the issues in the first place (when you take a 72-degree tube and bring it out into 20-degree air, and the tube RAPIDLY cools, causing air currents).

   Here in New England we regularly see Delta's of 50, 60, and 70 degrees.  And NO problems when the tube has been insulated with Reflectix BEFORE bringing outside.

I am not thinking of equalizing temp, I'm thinking just what astrobeast has articulated very well:  that heat transfer, even with insulation, may be more aggressive the greater the differential.  Therefore, perhaps bringing the insulated scope out from my semi-warm garage rather than my very-warm home would be preferable.  But if your experience is that a couple wraps of reflectix works fine with 50-70 degree differentials then I should be fine keeping the scope in the house.  However, isn't the mount and tripod going to give off heat plumes in front of the scope for a bit if it is also brought straight out of the house?

 

To address one aspect of astrobeast's post...  I think there is at least one advantage to a very warm scope (vast differential) as opposed to a scope close to ambient:  greater dew resistance for corrector.  This is of interest to me because I do not use active dew prevention.


Edited by Usquebae, 29 August 2018 - 09:08 AM.


#19 Bean614

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Posted 29 August 2018 - 09:10 AM

"Anyway, hope this is clear and look forward to any comments. Again, great thread as this really seems to the “too good to be true” answer, which actually isn’t!
Rick"

  Actually, if you read the various posts, from the Hundreds of CN Members who have tried it, and now wouldn't think of not using it, I don't see why you would say “too good to be true” answer, which actually isn’t!".  Why isn't it?  Reflectix is VERY cheap ($20--$25 per roll) so why not try it yourself, instead of speculating on what the results MIGHT be?



#20 astrobeast

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Posted 29 August 2018 - 10:33 AM

"Anyway, hope this is clear and look forward to any comments. Again, great thread as this really seems to the “too good to be true” answer, which actually isn’t!
Rick"

  Actually, if you read the various posts, from the Hundreds of CN Members who have tried it, and now wouldn't think of not using it, I don't see why you would say “too good to be true” answer, which actually isn’t!".  Why isn't it?  Reflectix is VERY cheap ($20--$25 per roll) so why not try it yourself, instead of speculating on what the results MIGHT be?

Just to be clear, I meant no offense, and I do intend to try it! Nor did it seem to me that I was doubting the efficacy of the approach. Just trying to work out my own understanding of what was going on.

 

I think what was responding to are the still long threads and endless hours that many users still seem to be expending on dealing with tube currents. People are still buying cat coolers, tempest fans, and there are still a lot of posts on combating this issue. Granted that many of these are dealing with reflectors which is a whole different kettle of fish, but just from my cruising this site, it seems this approach is still aways from really wide spread use. Again, my last statement was one of endorsement, not a disparagement. Maybe just didn't come across that way. If so, my apologies.

 

Rick



#21 astrobeast

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Posted 29 August 2018 - 10:35 AM

"Anyway, hope this is clear and look forward to any comments. Again, great thread as this really seems to the “too good to be true” answer, which actually isn’t!
Rick"

  Actually, if you read the various posts, from the Hundreds of CN Members who have tried it, and now wouldn't think of not using it, I don't see why you would say “too good to be true” answer, which actually isn’t!".  Why isn't it?  Reflectix is VERY cheap ($20--$25 per roll) so why not try it yourself, instead of speculating on what the results MIGHT be?

Actually, in rereading my statement, I think there is a not well executed double negative, so I can see where you are coming from. What I meant to imply is that it 'is not too good to be true". Sorry for the confusion.



#22 astrobeast

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Posted 29 August 2018 - 10:36 AM

Actually, in rereading my statement, I think there is a not well executed double negative, so I can see where you are coming from. What I meant to imply is that it 'is not too good to be true". Sorry for the confusion.

Arggg, it's still not coming out right , lol. Just for the record, I was agreeing that it is in fact true and a great approach.

 

R


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#23 Joe1950

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Posted 29 August 2018 - 11:03 AM

We're good, Rick!  waytogo.gif



#24 astrobeast

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Posted 29 August 2018 - 11:12 AM

We're good, Rick!  waytogo.gif

 

Thanks Joe!

 

But back to one comment I made, is it my imagination that this approach is not as widely practiced as one would expect given how successful (not to mention simple and cheap) it is? Obviously, the word is spreading, so is it just a matter of the level of users awareness of this remedy?

 

Like this is just sooooooo much easier than fans, coolers, taking the outside hours before, storing in the garage, etc. Just curious.

R


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#25 Usquebae

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Posted 29 August 2018 - 12:12 PM

But back to one comment I made, is it my imagination that this approach is not as widely practiced as one would expect given how successful (not to mention simple and cheap) it is? Obviously, the word is spreading, so is it just a matter of the level of users awareness of this remedy?

 

Like this is just sooooooo much easier than fans, coolers, taking the outside hours before, storing in the garage, etc. Just curious.

R

My impression is that insulation has not been widely practiced among active CNers, as you suggest, but the word is spreading - largely due to a long thread by yellobeard (the Socrates of SCTs) explaining how well it works and why.  Nevertheless, I still see regular posts about CAT coolers and fans.  I think a recent thread pitted one opinion standard SCTs having a cooling advantage because you can use a CAT cooler, while others were claiming Edge scopes have an advantage because of their vents.  I've been reading a lot lately about the C9.25 (planning a purchase) and can't certainly separate the recent from the 5-10 year old info, but I am sure that I've seen almost no comments about insulation.  There doesn't appear to be anything related to insulation pinned to the top of the SCT forum or in the "best of links."  Maybe that needs to change!

 

In my current location I can conveniently sit my dobs out in the garage or under a 2nd floor porch while I'm at work, so cooling isn't a major hassle.  But I do expect that having my 98 degree body just a few inches from the front of the telescope during the frigid winter is impacting my views.  So I'm excited about the prospect of having dew resistant, thermally steady 9" scope that I can sit behind.




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