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Questions About Insulating SCT's with Reflectix

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#201 yellobeard

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Posted 12 January 2019 - 11:58 AM

Of course, 'hard evidence' in many cases would be the most convincing. However, as much as many people can say that 'verbal testimonials' are not convincing enough, I can say that photographic testimonials are not convincing enough!

Many times, I had encounters with people who used photography to convince others (or themselves) about the image quality of their scopes. While in this time of 'manipulating data to get a better picture', its not so much the quality of the scope, but more the skills of the person behind the PC, who determines the quality of the picture!

So, I can post pictures of objects, taken through my 16" SCT, but you will immediately put them aside, as I absolutely do not have the astro photographic skills many others have!
As many others, I am a pure visual observer, and will never start photography only because I feel de need (or feel forced) to prove the quality of my scopes.

Using a hairdryer to 'clean' your schmidt corrector plate, is a very 'uncontrolled' way to warm it up in such way, that indeed you will see an effect in the image for some time!
People often have the tendency to somewhat overheat that corrector plate, to enjoy a clear image for longer, causing more aberrations just after heating..

I am not going into details anymore about what is the best way to enjoy that clear and sharpest image during the entire night, I already did that many, many times! So, beleve it, or don't beleve it.
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#202 Sarkikos

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Posted 12 January 2019 - 12:00 PM

 

What I can say is that using the hair-dryer method of removing dew/condensation on the outside of the C14 corrector - something we regularly do between imaging runs, which might be anything from 3 minutes up to 10 minutes, there is a noticeable degradation of the onscreen image whilst the corrector gives up this heat, usually around 3 to 4 minutes. (the 10 minutes is for Neptune, where a long dew-shield helps noticeably at keeping condensation at bay over this 10 minute period when the night is prone to said...)

 

In my opinion, having to use a hair-dryer to remove condensation from a corrector is a fail, especially if you have to do it every three to ten minutes.  There must be a better way. 

 

I put dew shields and warming strips on my Cats.  Very seldom do I experience any condensation on the corrector.  When I do, it's only after many hours.  It's a sign that the battery supplying power to the warming strip has finally died.  That's a failure of the battery, not the warming strip or the dew shield.  

 

As I said in the opening post,  I think dew prevention is more important than thermal prevention.  Of course, I'd like to do both. grin.gif

 

Mike


Edited by Sarkikos, 12 January 2019 - 12:04 PM.


#203 Ron359

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Posted 12 January 2019 - 01:50 PM

Also often overlooked:   Because you are at or below sea level in the Netherlands, how much differential drop per hour do you have of air temperature and increase in humidity when observing on a clear night?  

 

 

In my country, there is no 'stable' or reliable situation as it comes to changes in temperature and humidity during the night.
However, I think that many know that during 'clear sky' situations, the temperature significantly drops, and that dewpoint issues are reached easily, unless you live in a very dry area, like a dessert..

My point 'to readers' is that you live and observe in one extreme end of a whole spectrum of climate environments which will greatly change the response of wrapping a thin bit of insulation around a tube to supposedly separate it from the ambient conditions.  Since you don't provide 'data', what you tell us is 'not stable' is relative to you in your generalization.   So a house in Florida or southern Spain has to have say R-10 worth of insulation to keep warmth in during colder months.  While a house in Canada or northern US has to have much greater insulation thickness of R-60 to keep a stable temp. inside and a heat source replacing lost heat despite all the insulation.  Where your little 1/2" of foil may work to slow radiation cooling to ambient and slow convection, a telescope in the continental interiors far from moderation of oceans may require 6" or 12" or who knows what thickness to achieve that - since many reject 'theory' and principles of thermodynamics as "too hard",  required to scientifically design the thickness.  Which of course also varies with the cube of the volume - diameter and length and design of the particular type of telescope.  Thats probably why telescope makers who have to make real telescopes for real money, for millions of people have never bothered to go beyond fans to circulate air in and out to reach and keep close to local ambient temps rather than figure out an insulating blanket for every range of climate on the planet where their scopes are used.  

 

You can tell people to just believe me and try it. But then I could tell you its obvious the earth is flat cause I can see the horizon out my window, or that the sun rises every morning so must go around the earth.  And my friends over the horizon in another state think I'm a fool for not believing what science has demonstrated day after day since Galileo.  

 

 To the vast majority of observers, living well above sea level, far from huge oceans of water, their environment is 'relatively far less stable' than you live in, to use a broad arm-waving generalization.  The principle overlooked is called "Thermal Inertia".  Since you and others don't like 'theory', here is a simple explanation:    https://www.youtube....h?v=Ndzc4sAv0qs


Edited by Ron359, 12 January 2019 - 02:23 PM.


#204 choward94002

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Posted 12 January 2019 - 02:41 PM

Quite correct that different climates will have different thresholds for dew and different amounts of dew, so as with shoes one size doesn't fit all ... as a good guideline, compare the lowest dewpoint temperature for the evening against the lowest temperature for the evening ...

 

- if DP is lower than LP then you're going to get dew, period.  Plan to either blast it with a hair dryer or have a dew heater running all night

- if DP is 5C lower than LP then you MIGHT get dew depending on if you have a dewshield.  Plan to use one

- if DP is 10C lower than LP then you're unlikely to get dew

 

As to amounts, look to the average RH for the evening ...

 

- if it's more than 80% (like next to the coast) then you're going to get drenched if you get dew.  Plan accordingly

- if it's 50% to 80% then you'll get some droplets

- if it's less than 50% then you'll get a fine mist/ fog

 

I have some dewpoint graphs I posted in my "acclimatization" thread that show this relationship for a site next to a coast, one in the high mountains and one at a semi-desert location in Australia ... 


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#205 yellobeard

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Posted 12 January 2019 - 06:23 PM

Dear Ron, you are quite right, but you forget that we sometimes have eastern winter winds that give us very cold temperatures.

And:

Its not about R-10 or R-60 of insulation, because if you go that far into comparing a telescope to a house, then you are losing track on reality!
You forget that that "little 1/2" of foil" on a 12" SCT, already is compareble to R-60 of insulation on a house..

I think that my contribution to these matters already has given many happy faces, and that is enough for me.
I now am going to put my time in my new 24" Flex-SCT project, properly insulated of course!
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#206 Kokatha man

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Posted 12 January 2019 - 07:47 PM

Of course, 'hard evidence' in many cases would be the most convincing. However, as much as many people can say that 'verbal testimonials' are not convincing enough, I can say that photographic testimonials are not convincing enough!

Many times, I had encounters with people who used photography to convince others (or themselves) about the image quality of their scopes. While in this time of 'manipulating data to get a better picture', its not so much the quality of the scope, but more the skills of the person behind the PC, who determines the quality of the picture!

 

This is completely encompassed within Ron 359's comments earlier in this thread: <"Another to me -unbelievable 'myth' I've seen posted in this SCT forum is that some think those great planetary images you and others get, are essentially faked by photoshop type processing adding details that are not really there in the raw images!">

 

I guess that means no point in discussing anything based upon anything other than hearsay..."optical specialists" included! lol.gif

 

In my opinion, having to use a hair-dryer to remove condensation from a corrector is a fail, especially if you have to do it every three to ten minutes.  There must be a better way. 

 

I put dew shields and warming strips on my Cats.  Very seldom do I experience any condensation on the corrector.  When I do, it's only after many hours.  It's a sign that the battery supplying power to the warming strip has finally died.  That's a failure of the battery, not the warming strip or the dew shield.  

 

As I said in the opening post,  I think dew prevention is more important than thermal prevention.  Of course, I'd like to do both. grin.gif

 

Mike

My goodness - all I can say is that it's a good thing for us that our pass/fail criteria are vastly different Mike..! rofl2.gif

 

Aside from reinforcing the silliness of a lot of this "Reflectix" devotion to me, I'll repeat once more what I said in my last post: regardless of whatever any single person's interest is in high-resolution imaging at high magnification, I'd like to hear of anyone who successfully employs aforesaid approach to achieve their results - but then of course they'd be most likely manipulating their data to achieve their results, just like us! lol.gif

 

Although as I said before, you must also have extra-sensory perception to be able to fabricate images that display hitherto undiscovered detail or otherwise uncirculated information - such as the following from arguably the most difficult as well as most distant planet to image:

 

September 2015: Pat & myself resolving: <"One storm spot had not been picked up in any images except those taken with large professional telescopes…in fact the HST (Hubble Space Telescope) imaged Neptune around the same time as the images to the left & below & confirmed our own images’ accuracies almost “point-by-point” in comparison to the HST as one professional astronomer worded it at the following year's Washington conference.">

 

June 2016: Pat & I sent images off to a professional organisation in Europe that we collaborate with & got a very quick response back telling us that these 2 spots were indeed storms on Neptune. They had been imaged by the Hubble orbiting telescope as well as a large professional scope in the Canary Islands not long before we captured these images – we were told that the reason why they had not sent out any “alerts” to amateur imagers about them was because they considered they were too difficult for amateurs to image so early in the apparition: we were of course very flattered to realise we had done so - & confounded their expectations of what amateurs were capable of..!

 

July 10th 2017: Picking up the hitherto unknown existence of storms in Neptune's Equatorial Zone, confirmed a few weeks later by the Keck in Hawaii.

 

As a further comment on the nonsense seemingly intimated in yellobeard's post that I've quoted from above, take a look at the RAW (unprocessed stacks) of Neptune as well as the processed ones of this feature taken on July 14th here, where no sensible person can maintain such ridiculous assertions! http://momilika.net/...4_IR610-FIN.png



#207 Ron359

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Posted 13 January 2019 - 06:45 PM


You forget that that "little 1/2" of foil" on a 12" SCT, already is compareble to R-60 of insulation on a house..

 

Thanks. That tells us all we need to know about your advice.  rolleyes.gif     coldday.gif


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#208 Sarkikos

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Posted 13 January 2019 - 07:09 PM

 

 

Sarkikos, on 12 Jan 2019 - 12:00 PM, said:

In my opinion, having to use a hair-dryer to remove condensation from a corrector is a fail, especially if you have to do it every three to ten minutes.  There must be a better way.

I put dew shields and warming strips on my Cats.  Very seldom do I experience any condensation on the corrector.  When I do, it's only after many hours.  It's a sign that the battery supplying power to the warming strip has finally died.  That's a failure of the battery, not the warming strip or the dew shield. 

As I said in the opening post,  I think dew prevention is more important than thermal prevention.  Of course, I'd like to do both.

Mike

 

 

My goodness - all I can say is that it's a good thing for us that our pass/fail criteria are vastly different Mike..! rofl2.gif

 

 

My attitude probably matches that of most observers.  I don't think most amateur astronomers really want to bother with ice and salt bags, and the inconvenience of removing condensation from correctors with a hair dryer every three to ten minutes.  Time spent blasting the corrector with a hair dryer is time I'll never get back for actually observing at the telescope.

 

We want some reasonable compromise that will give us freedom from condensation as well as show us a decent image.  Personally, I only do visual.  I've never done AP and I never will.  So I'm looking for some protocol that will provide decent visual images without a burdensome outlay of time and effort.  I'll leave the pursuit of perfection for the APers.

 

Mike


Edited by Sarkikos, 13 January 2019 - 07:14 PM.

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#209 Kokatha man

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Posted 13 January 2019 - 09:36 PM

My attitude probably matches that of most observers.  I don't think most amateur astronomers really want to bother with ice and salt bags, and the inconvenience of removing condensation from correctors with a hair dryer every three to ten minutes.  Time spent blasting the corrector with a hair dryer is time I'll never get back for actually observing at the telescope.

 

We want some reasonable compromise that will give us freedom from condensation as well as show us a decent image.  Personally, I only do visual.  I've never done AP and I never will.  So I'm looking for some protocol that will provide decent visual images without a burdensome outlay of time and effort.  I'll leave the pursuit of perfection for the APers.

 

Mike

I won't claim to be privy to any <"I don't think most..."> attitudes Mike lol.gif...time spent playing with Reflectix, dew heaters & the plethora of (for me!) "Emperor's New Clothes" etc notions is a waste of time: even (maybe) the time spent considering such as per your Post #166 time...many weighty tomes indeed! smile.gif

 

Someone replied to me in this or a similar thread (not saying it was you Mike! wink.gif ) that everything was "anecdotal" when I suggested that this was far more descriptive for insulative benefits as opposed to the evidence of imagers - this is nonsense of course...very much in the vein of yellobeard's assertions about imagers "creating" imagery.

 

As to any suggestions of a differentiation between "best practises" for visual as opposed to imaging...well, good luck with that notion mate! waytogo.gif  

 

For some reason I'm reminded of Etienne Trouvelot & his rationale for the superiority of hand-drawn images a bit...

 

Just to clarify for the last time - it is after all your thread where you've stated <"I have no settled opinions about it.  I just want to find out as much as I can about the general subject of this thread - Insulating SCT's with Reflectix - before experimenting with Reflectix myself."> (please anybody!) I would like to see at least a couple of instances of hi-res images taken using the insulative approach, regardless of what preferences either you or I favour.....but it does seem strange to me that none seems to be found on that score..!

 

Give me these examples & I might recant my beliefs! wink.gif

 

However, I certainly give the award for the most amount of noise to the Reflectix folks..! waytogo.gif

 

 



#210 Peter Besenbruch

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Posted 14 January 2019 - 01:45 AM

My goodness - all I can say is that it's a good thing for us that our pass/fail criteria are vastly different Mike..! rofl2.gif

I'm with Mike on this one. If you have to use a hair dryer every 3-10 minutes, there is something wrong in your management protocol.


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#211 Kokatha man

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Posted 14 January 2019 - 04:31 AM

I'm with Mike on this one. If you have to use a hair dryer every 3-10 minutes, there is something wrong in your management protocol.

Good on you Peter..! waytogo.gif

 

I've always found affinity with "your" Will Rogers - an American First Nations' descendant, just as I am an Australian First Nations' descendant...his exhortation to "always drink upstream from the herd" has a fine resonance for me...& of course I can't help but paraphrase one of his other sayings, which seems apposite here & very much an essence of healthy black humour - "I've joked about every crackpot idea in my time, but I never met a man I didn't like." (on a one-on-one basis, that is smile.gif )

 

Please don't take offence, but like the few Native Americans I've met & shared time with, many of our own mob also laugh when we hear about "management protocols." smile.gif



#212 rik ter horst

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Posted 14 January 2019 - 07:33 AM

 

 

Just to clarify for the last time - it is after all your thread where you've stated <"I have no settled opinions about it.  I just want to find out as much as I can about the general subject of this thread - Insulating SCT's with Reflectix - before experimenting with Reflectix myself."> (please anybody!) I would like to see at least a couple of instances of hi-res images taken using the insulative approach, regardless of what preferences either you or I favour.....but it does seem strange to me that none seems to be found on that score..!

 

Give me these examples & I might recant my beliefs! wink.gif

 

 

It must have been around 2004 when I insulated my 200 mm F/25 SCT. I noticed a significant inprovement in image quality, mainly because of reduced thermal gradients in the optical path. No doubt, a fully cooled telescope is the best option if you want to make high-res images. But here in the Netherlands, by the time the scope has cooled down, the sky will be gray again....

Insulating the tube is my personal best option, as it gives me the opportunity to start observing immediately.

 

The image below is made using this insulated 200 mm F/25 SCT back in 2014. Just an example ;-)

 

conv_Jup_050314_190552_g4_b3_ap37PS.jpg


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#213 Freezout

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Posted 14 January 2019 - 08:52 AM

But here in the Netherlands, by the time the scope has cooled down, the sky will be gray again....

Insulating the tube is my personal best option, as it gives me the opportunity to start observing immediately.

 

Living also in the same region of the Netherlands (in fact in one of the coldest place of the country!), I can confirm that clear nights can be very cold, with a serious temperature difference with inside my house.

Disclaimer: I have no astropictures to support my claim, and I have no pretention to make anything else than an empirical statement about my single situation. Since I insulated my telescope, I can observe directly after installation. And I never had dew anymore.  I use industrial pipe insulation, a layer of thermal insulation foil, a dew cap and a dew heater at very low setting (to compensate the little loss of heat and have an OTA at constant temperature). 



#214 Sarkikos

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Posted 14 January 2019 - 10:05 AM

I won't claim to be privy to any <"I don't think most..."> attitudes Mike lol.gif...time spent playing with Reflectix, dew heaters & the plethora of (for me!) "Emperor's New Clothes" etc notions is a waste of time: even (maybe) the time spent considering such as per your Post #166 time...many weighty tomes indeed! smile.gif

 

Someone replied to me in this or a similar thread (not saying it was you Mike! wink.gif ) that everything was "anecdotal" when I suggested that this was far more descriptive for insulative benefits as opposed to the evidence of imagers - this is nonsense of course...very much in the vein of yellobeard's assertions about imagers "creating" imagery.

 

As to any suggestions of a differentiation between "best practises" for visual as opposed to imaging...well, good luck with that notion mate! waytogo.gif  

 

For some reason I'm reminded of Etienne Trouvelot & his rationale for the superiority of hand-drawn images a bit...

 

Just to clarify for the last time - it is after all your thread where you've stated <"I have no settled opinions about it.  I just want to find out as much as I can about the general subject of this thread - Insulating SCT's with Reflectix - before experimenting with Reflectix myself."> (please anybody!) I would like to see at least a couple of instances of hi-res images taken using the insulative approach, regardless of what preferences either you or I favour.....but it does seem strange to me that none seems to be found on that score..!

 

Give me these examples & I might recant my beliefs! wink.gif

 

However, I certainly give the award for the most amount of noise to the Reflectix folks..! waytogo.gif

 

Here is my Opening Post:

 

I observe in areas that are prone to prolonged heavy dew/frost.  If there is no dew/frost, that would be the exception.  Unless I put the dew shield on the scope, and wrap warming strips around the OTA behind the corrector, around the eyepiece, on the Telrad and around the finderscope objective and eyepiece, turn on the batteries and keep them on, dew/frost will form on the optics, guaranteed.  It's not really a question of if dew/frost will form, but when it will form:  sooner or later.  The warming strips DO prevent dew/frost.

So if I wrap the OTA in Reflectix, will I still need the warming strips to prevent dew/frost?  If there is a choice between no thermals and no dew/frost, I'd rather do without the dew/frost.  The effect of dew/frost on the corrector is a lot worse for observing than thermals in the tube.  Mike

 

I am the Topic Starter.  I'm pretty sure that means I get to determine what the Topic should be about.  Notice I used the phrase "I observe" at the very beginning of the Opening Post.  Also notice that I used the word "eyepiece" twice.  These should indicate to the reader of this thread that I am a visual amateur astronomer.  I have absolutely no interest in AP. I have never done AP.  I don't do AP.  I never intend to do AP.  So any posts which are about how to produce perfect images for AP have no interest for me unless they are applicable to visual astronomy.

 

Also notice my priorities.  In the Opening Post I distinctly stated that I consider condensation more of a problem for observing than tube thermals.  Given dew control as a higher priority, I obviously would consider having to blast off condensation every three minutes with a hair dryer to be a major failure for an observing session. 

 

Please keep the above points in mind when posting and when responding to my posts and the posts of others here. 

 

I am not interested in AP.  I am not interested in anything which is not applicable to visual astronomy.  I do not want to waste my time battling dew with a hair dryer.  In my opinion and in my experience, that would be a step backwards.  I do not want to put a bag of brine on the OTA every time before I observe.  The perfect can be the enemy of the good.  KISS.

 

So how about some ideas that would be good enough for the average Joe or Jane visual amateur astronomer who just wants a dew free observing session with decent visual images? 

 

Mike


Edited by Sarkikos, 14 January 2019 - 10:16 AM.

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#215 jhayes_tucson

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Posted 14 January 2019 - 10:44 AM

Here is my Opening Post:

 

 

I am the Topic Starter.  I'm pretty sure that means I get to determine what the Topic should be about.  Notice I used the phrase "I observe" at the very beginning of the Opening Post.  Also notice that I used the word "eyepiece" twice.  These should indicate to the reader of this thread that I am a visual amateur astronomer.  I have absolutely no interest in AP. I have never done AP.  I don't do AP.  I never intend to do AP.  So any posts which are about how to produce perfect images for AP have no interest for me unless they are applicable to visual astronomy.

 

Also notice my priorities.  In the Opening Post I distinctly stated that I consider condensation more of a problem for observing than tube thermals.  Given dew control as a higher priority, I obviously would consider having to blast off condensation every three minutes with a hair dryer to be a major failure for an observing session. 

 

Please keep the above points in mind when posting and when responding to my posts and the posts of others here. 

 

I am not interested in AP.  I am not interested in anything which is not applicable to visual astronomy.  I do not want to waste my time battling dew with a hair dryer.  In my opinion and in my experience, that would be a step backwards.  I do not want to put a bag of brine on the OTA every time before I observe.  The perfect can be the enemy of the good.  KISS.

 

So how about some ideas that would be good enough for the average Joe or Jane visual amateur astronomer who just wants a dew free observing session with decent visual images? 

 

Mike

 

 

Mike,

If all you are doing is visual, then it's pretty simple.

 

A)  Get a dew shield.  The optimum length is about 1.5x the aperture.  Get an aluminum shield.  AstroZap has a nice selection. 

 

B)  Get a dew heater controller and run two straps.  Put one on the OTA about 1/3 of the way from the front of the scope to the rear and put a second one on dew shield--about in the middle.  Run both at the minimum temperature to prevent dew.  With the dew shield, the low power setting should work under almost all conditions without creating any significant thermals.  You can get a decent controller and good heater straps from AstroZap.

 

C)  If your scope can accommodate them, I highly recommend using Tempest fans as well.  These fans move only a small amount of air but they are very effective for eliminating the central baffle plume--and that makes for a significant improvement in image quality.  As I recall, the fans are not cheap; but, in my experience, they are well worth it.

 

If you do these three things, I believe that you'll be very satisfied with the results.  The dew shield + heaters will solve your dew problems and the fans will go a long way toward improving image quality as your scope cools down.

 

John


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#216 choward94002

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Posted 14 January 2019 - 10:52 AM

... various ...

 

I am not interested in AP.  I am not interested in anything which is not applicable to visual astronomy.  I do not want to waste my time battling dew with a hair dryer.  In my opinion and in my experience, that would be a step backwards.  I do not want to put a bag of brine on the OTA every time before I observe.  The perfect can be the enemy of the good.  KISS.

 

So how about some ideas that would be good enough for the average Joe or Jane visual amateur astronomer who just wants a dew free observing session with decent visual images? 

 

Mike

Solar observing comes to mind, will definitely be dew free and will give nice visual images ...

 

Not trying to be pendantic, but you've made two statements here that are completely at odds with each other and that once you understand that you'll understand the answers that people are trying to share ...

 

You said "decent visual images" ... and, you said "dew free observing session" ...

 

The only way you're not going to get dew at some point is during the day ... that's just physics and meteorology.  If you absolutely don't want to have to deal with dew, observe during the day.

 

By "decent visual images" it's implied that you don't want to look at a churning, writhing smudged blob of something ... which means you don't want tube thermals.  The only way you won't get tube thermals is if the tube is in total thermal stability, which is only going to happen during the day.

 

If you don't want to do solar, then you're going to be dealing with dew, period.  The only way to prevent dew is by stopping the corrector plate from getting cold enough to trigger condensation, which is typically done by either retarding cooling by using dew shields/ insulation/ etc. or by adding heat to the system by dew heaters.  Note that I didn't say you could stop dew by getting the scope into thermal stability because the scope will continue to cool by a variety of methods until it's cold enough to get dew.

 

If you add heat to the system, you're going to be dealing with tube thermals, period.  The only way to prevent tube thermals is by getting the scope into thermal stability with everything the same temperature.

 

A simple search on CN for your name and "thermal" shows you've been asking this same basic question for over five years now, about every six months or so ... and the laws of thermodynamics haven't changed very much over that period of time which means you've been getting the same answers every single time you bring up this topic over the last five years.  That means you are either trolling (which can be quite entertaining, I agree) or you just don't get it ...

 

The only way you can get decent visual images without dew and without using all of the various methods folks have been telling you about for over five years now is by observing solar.  Go buy a Lunt, you will get very nice images and will never see a lick of dew again ...

 

Have I made things more clear?  Again, sorry for being a bit pedantic but again, you've been asking this same question for the last five years now ...


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#217 Sarkikos

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Posted 14 January 2019 - 01:09 PM

Solar observing comes to mind, will definitely be dew free and will give nice visual images ...

 

Not trying to be pendantic, but you've made two statements here that are completely at odds with each other and that once you understand that you'll understand the answers that people are trying to share ...

 

You said "decent visual images" ... and, you said "dew free observing session" ...

 

The only way you're not going to get dew at some point is during the day ... that's just physics and meteorology.  If you absolutely don't want to have to deal with dew, observe during the day.

 

By "decent visual images" it's implied that you don't want to look at a churning, writhing smudged blob of something ... which means you don't want tube thermals.  The only way you won't get tube thermals is if the tube is in total thermal stability, which is only going to happen during the day.

 

If you don't want to do solar, then you're going to be dealing with dew, period.  The only way to prevent dew is by stopping the corrector plate from getting cold enough to trigger condensation, which is typically done by either retarding cooling by using dew shields/ insulation/ etc. or by adding heat to the system by dew heaters.  Note that I didn't say you could stop dew by getting the scope into thermal stability because the scope will continue to cool by a variety of methods until it's cold enough to get dew.

 

If you add heat to the system, you're going to be dealing with tube thermals, period.  The only way to prevent tube thermals is by getting the scope into thermal stability with everything the same temperature.

 

A simple search on CN for your name and "thermal" shows you've been asking this same basic question for over five years now, about every six months or so ... and the laws of thermodynamics haven't changed very much over that period of time which means you've been getting the same answers every single time you bring up this topic over the last five years.  That means you are either trolling (which can be quite entertaining, I agree) or you just don't get it ...

 

The only way you can get decent visual images without dew and without using all of the various methods folks have been telling you about for over five years now is by observing solar.  Go buy a Lunt, you will get very nice images and will never see a lick of dew again ...

 

Have I made things more clear?  Again, sorry for being a bit pedantic but again, you've been asking this same question for the last five years now ...

 

I just now did a search for "Sarkikos thermal site:cloudynights.com" and came up with some false dates for threads.  For instance, Bing shows the current thread, "Questions About Insulating SCTS with Reflectix," as going back to 12-5-2012.  But my Opening Post wasn't until 11-26-2018!   So don't believe everything you see when searching the internet.  

 

My interest in solving thermal and dew problems does go back for years.  But the idea of using Reflectix has flown below my radar until recently.  I did hear about ice packs for SCTs and Maks a few years ago.  (Tap water packs, not salty ones.)  However, I was interested in controlling thermals for Newts long before I was concerned about it for Cats.

 

In fact, I never heard about you until the last few months.  You also flew below my radar.  

 

No, I'm not a troll.  I'm also not an engineer.  And I'm certainly not an AP fanatic.  I try not to be a fanatic about anything in astronomy … or in anything else, for that matter.  

 

I'm just a visual amateur astronomer who wants to be free from dew and have decent images for visual astronomy.  I didn't say perfect images.  Decent means better, not necessarily perfect.  

 

For a visual amateur astronomer, zapping the corrector with a hair dryer every three minutes means a failed observing session.  It is something a newbie would do.  A more experienced observer would be sure to have both passive and active dew prevention in place:  a dew shield and warming strips.  Clearing the dew over and over again after the fact just doesn't cut it for serious visual astronomy.

 

Having dew appear anywhere on the optics anytime during the observing session is at least a partial fail.  

 

In any case, as yellobeard pointed out, won't a hair dryer blasting the corrector every three minutes add heat to the optical system and produce thermals that will show an effect in the image for some time?  

 

Prepping the scope with a bag of brine is an inconvenience.   Probably most observers would want to avoid it.  But at least it's not something we'd have to do every three minutes.

 

I don't think I am an outlier in this hobby.  It'd be difficult for me to believe that there aren't many others who share my attitudes and opinions about controlling dew for visual astronomy. 

 

Mike


Edited by Sarkikos, 14 January 2019 - 01:33 PM.


#218 choward94002

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Posted 14 January 2019 - 01:56 PM

I just now did a search for "Sarkikos thermal site:cloudynights.com" and came up with some false dates for threads.  For instance, Bing shows the current thread, "Questions About Insulating SCTS with Reflectix," as going back to 12-5-2012.  But my Opening Post wasn't until 11-26-2018!   So don't believe everything you see when searching the internet.  

 

Apparently you're not looking in the right spots, I'm just using the CN "advanced search" to skim forum posts (remember to check for archived content too) ... back in 2010 you were answering questions about dew shields here [https://www.cloudyni...k/#entry3859150], in 2015 there was a Reflectix thread itself you participated in [https://www.cloudynights.com/topic/509486-reflectix-dew-shield/#entry6748207] and later that year you discussed having a shiny interior on dew shields [https://www.cloudynights.com/topic/507462-dewsmaster-dew-shield/#entry6715671]

 

My interest in solving thermal and dew problems does go back for years.  But the idea of using Reflectix has flown below my radar until recently.  I did hear about ice packs for SCTs and Maks a few years ago.  (Tap water packs, not salty ones.)  However, I was interested in controlling thermals for Newts long before I was concerned about it for Cats.

 

True on your interest, that goes back eight plus years to 2010 ... but recall you were talking Reflectix in 2015, that's not quite "recently" ...

 

...

 

I'm just a visual amateur astronomer who wants to be free from dew and have decent images for visual astronomy.  I didn't say perfect images.  Decent means better, not necessarily perfect.  

 

For a visual amateur astronomer, zapping the corrector with a hair dryer every three minutes means a failed observing session.  It is something a newbie would do.  A more experienced observer would be sure to have both passive and active dew prevention in place:  a dew shield and warming strips.  Clearing the dew over and over again after the fact just doesn't cut it for serious visual astronomy.

 

Excellent, that is the answer you've gotten and been giving folks since late 2010 about every six months or so, the one that John Hayes said a little bit ago and which will still be true decades from now ... dew shield as directed, dew heater as directed, done.  If you never want to see dew then put 40W of heater power to work like I do or get a Lunt and go solar, you will NEVER see dew ...

 

Having dew appear anywhere on the optics anytime during the observing session is at least a partial fail.  

 

In any case, as yellobeard pointed out, won't a hair dryer blasting the corrector every three minutes add heat to the optical system and produce thermals that will show an effect in the image for some time?

 

The answer is a qualified no ... the fellows talking about using the hair dryer do it at the first sign of dew when the glass is maybe .1C below dewpoint and they are only heating the outside skin of the glass above that, not the entire sheet.  But you already know that, you talked about just this solution in a post two years ago [https://www.cloudyni.../#entry7201991]

 

Prepping the scope with a bag of brine is an inconvenience.   Probably most observers would want to avoid it.  But at least it's not something we'd have to do every three minutes.

 

Kokatha and Asbytec both prep once at the beginning, and as i mentioned in my Crash Cooling thread you only need to do it at the beginning of the night and then you're done ... certainly not every three minutes.  But you already know this from a long thread by them about cooling that you participated in 2015 with [https://www.cloudyni...7#entry6867809]

 

I don't think I am an outlier in this hobby.  It'd be difficult for me to believe that there aren't many others who share my attitudes and opinions about controlling dew for visual astronomy. 

 

You absolutely aren't, but again the laws of physics haven't changed that much since 2010 when you were talking about dew shields, since 2015 when you were chatting about Reflectix and cooling ... if you want to ask the question "what has changed since the last time I pinged about this topic" that's one thing, but again not much has changed since 2010 or 2015 ... 

 

Mike


Edited by choward94002, 14 January 2019 - 01:56 PM.


#219 Sarkikos

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Posted 14 January 2019 - 02:08 PM

 

 

My interest in solving thermal and dew problems does go back for years.  But the idea of using Reflectix has flown below my radar until recently.  I did hear about ice packs for SCTs and Maks a few years ago.  (Tap water packs, not salty ones.)  However, I was interested in controlling thermals for Newts long before I was concerned about it for Cats.

True on your interest, that goes back eight plus years to 2010 ... but recall you were talking Reflectix in 2015, that's not quite "recently" …

 

When you're 62, three or four years ago is very recent!

 

:grin:

Mike


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#220 Kokatha man

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Posted 14 January 2019 - 10:19 PM

When you're 62, three or four years ago is very recent!

 

grin.gif

Mike

Hi again fellas - when you're older still (yep, I'm a 49'er) - 3 or 4 years ago can seem like a lifetime! lol.gif

 

But please! - let's not get into trolling or being outrightly antagonistic towards any viewpoints - my Will Rogers quote was meant to give some indication of how I generally feel about people & debate, unless it delves into personally derogatory comment - although it won't stop me calling a spade a spade! smile.gif

 

It must have been around 2004 when I insulated my 200 mm F/25 SCT. I noticed a significant inprovement in image quality, mainly because of reduced thermal gradients in the optical path. No doubt, a fully cooled telescope is the best option if you want to make high-res images. But here in the Netherlands, by the time the scope has cooled down, the sky will be gray again....

Insulating the tube is my personal best option, as it gives me the opportunity to start observing immediately.

 

The image below is made using this insulated 200 mm F/25 SCT back in 2014. Just an example ;-)

 

attachicon.gif conv_Jup_050314_190552_g4_b3_ap37PS.jpg

Hi Rik - well, I asked for examples & you've provided onewaytogo.gif - in fact it is a quite decent Jovian image tbh, but without wanting to "shift the goal posts" I'd be happier to see more. wink.gif

 

For anyone who doesn't know, I have great respect for Rik as an optician & telescope builder & at one stage sounded him out about making me a custom scope - alas, his schedule, my age & other constraints didn't allow that idea to get any traction..! frown.gif

 

My word of warning is that there are many factors involved in operating a scope at maximum capabilities, & that like any other evidence-based "research" or "experimentation" it is the consistency of results that determine the validity of any approach.

 

Consider this example from 2009 when our C11 had no cooling (nor acclimatisation period) & what we knew about collimation was zip, zero, nix. (it was still the same as when we received it second-hand from freight by someone halfway across the continent months (or was that a year) earlier...bigshock.gif

 

There are numerous other similar images, but for me at least a consistency across years has refined our approach to "best practise."

 

Nonetheless I accept Rik's observation about insulation, although I would like to hear what else he might have tried...

 

 

ScreenHunter_801 Jan. 15 12.55.jpg

 

 

I'm just a visual amateur astronomer who wants to be free from dew and have decent images for visual astronomy.  I didn't say perfect images.  Decent means better, not necessarily perfect.  

 

For a visual amateur astronomer, zapping the corrector with a hair dryer every three minutes means a failed observing session.  It is something a newbie would do.  A more experienced observer would be sure to have both passive and active dew prevention in place:  a dew shield and warming strips.  Clearing the dew over and over again after the fact just doesn't cut it for serious visual astronomy.

 

Having dew appear anywhere on the optics anytime during the observing session is at least a partial fail.  

 

In any case, as yellobeard pointed out, won't a hair dryer blasting the corrector every three minutes add heat to the optical system and produce thermals that will show an effect in the image for some time?  

 

Prepping the scope with a bag of brine is an inconvenience.   Probably most observers would want to avoid it.  But at least it's not something we'd have to do every three minutes.

 

I don't think I am an outlier in this hobby.  It'd be difficult for me to believe that there aren't many others who share my attitudes and opinions about controlling dew for visual astronomy. 

 

Mike

Mike, someone's already addressed your 2nd-last sentence in the quote above, although I suspect it is merely syntax - & you were not suggesting the "bag of brine" is applied every 3 minutes! rofl2.gif

 

I'd also ask that in any discussion directed towards my own comments that you make up your mind as to whether I'm a "newbie" or a "perfectionist."  Perhaps I'm a "newbie perfectionist" or vice-versa!

 

But for the sake of clarity let's clear up a couple of points: my (Post #200) <"What I can say is that using the hair-dryer method of removing dew/condensation on the outside of the C14 corrector - something we regularly do between imaging runs, which might be anything from 3 minutes up to 10 minutes..."> was not intended to be read as something we do every run, nor all the time...I also obviously wasn't as careful as I needed to be in wording that for some folks...when dew isn't an issue (which it isn't a lot of the time!) I'm not in the habit of blasting the corrector just for the sake of it..!!!

 

Mind you, when you do a very long session that might last up to 7 or 8 hours, getting up & down regularly is a godsend in that my back & legs would pack up completely sitting at the outside table staring at the laptop indefinitely!

 

In your Post #166 you posited the question: <"How do the requirements for decent visual compare to imaging?"> I note your opening comments there, as well as other comments you've made elsewhere "might" be interpreted as dismissive or perhaps even disdain for imaging per se...perhaps along the lines of someone else's views here: naturally I'd refute any opinion that imagers are some weird breed whose output & practises are strange, concocted or irrelevant.

 

Any possible suggestion that I (or anyone else) is some sort of "fanatic" because we aspire to our best in what we do could be reasonably interpreted as cheap, pejorative comment. "AP" has nothing special in that respect to any visual observing apropos optimising possibilities.

 

The tenets for successful imaging or observing are one & the same for all intents & purposes...the questioning of this really being in the "newbie" domain imho - but if you retract any intimations I've read I'll definitely declare that I don't think you're acting like a newbie yourself!

 

I first came "onboard" this thread in Post #162 where I related my own experiences with insulation: I am not a frequent visitor to "cats & cases" in comparison to other sections of CN...but I do see views espoused from time to time here that can be quite misleading...or at the least invite an alternative viewpoint, mainly from practical perspectives as is fitting from my background & wont.

 

I have no problems with folks rejecting "crash cooling" (choward's term) from an impractical aspect, even though it is far simpler than some of your comments suggest, just as the hair-dryer is not an inconvenience whatsoever when it is required: in my 70th year, with numerous back etc issues I quite simply find it a doddle to incorporate into our schedule...& the 5 minutes to put the ice & salt in the bag & plonk it on the scope hardly merits any concern about "impracticality" whatsoever..!

 

But it is true that my main concern is the lack of any evidence-based support for the Reflectix approach: Rik's comments gives me reason to pause in my (previous) condemnation although I still would like to see/hear more from people like him...& still wonder whether other approaches might yield better performance/results if they have not been tried - we don't always use the "bag of brine" as you so dispassionately describe lol.gif it but as Rik himself acknowledges, <"No doubt, a fully cooled telescope is the best option if you want to make high-res images">

 

That's it from me unless someone directs a question at my own comments - or to use Oz vernacular, appears to "slag off" at me or my postings..!?! wink.gif  


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#221 GlendaleGuy

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Posted 15 January 2019 - 08:51 AM

   After seeing a few conversations about the Reflectix telescope jacket, I decided to try for myself on the old C8 as it wasn't all that expensive. I made a fitted cover for the telescope and dew shield, using Velcro for holding it in place sticking it to itself in the overlap. That way it's easily removed or installed. I don't have any empirical data, but without the jacket I looked at a de-focused star and saw a heat plum coming from the center baffle. I then put the jacket in place and saw the heat plume slowly fade away. That was enough for me to keep using it. The separate dew shield cover allows me to take the dew shield off when I want to use a Batinov mask for focusing.

 

   In general what I do is take the telescope out a couple hours before dark without the jacket and let it sit. Then a bit before setting up to observe I put the jacket on it. It seems to help, or I'm just being superstitious!

Attached Thumbnails

  • Telescope Jacket s.jpg
  • Telescope Ready for the Cold s.jpg

Edited by GlendaleGuy, 15 January 2019 - 08:57 AM.

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#222 yellobeard

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Posted 15 January 2019 - 10:36 AM

Great work GlendaleGuy !!! These are the things that make me return to this thread..

The only thing is, those very nice (even nostalgic?) orange Celestrons are the only scopes that make me hesitate to insulate them like this, beautiful as they are!



#223 GlendaleGuy

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Posted 17 January 2019 - 01:29 PM

Great work GlendaleGuy !!! These are the things that make me return to this thread..

The only thing is, those very nice (even nostalgic?) orange Celestrons are the only scopes that make me hesitate to insulate them like this, beautiful as they are!

   I have to agree with you on that. Another reason why the jackets use Velcro and come off and on fast and easy. When I'm using it, it doesn't bother me so much that it's covered as you can't see much in the way of color after dark. It's nearly all looking through, than at!


Edited by GlendaleGuy, 17 January 2019 - 01:30 PM.

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#224 1074j

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Posted 17 January 2019 - 04:18 PM

My attitude probably matches that of most observers.  I don't think most amateur astronomers really want to bother with ice and salt bags, and the inconvenience of removing condensation from correctors with a hair dryer every three to ten minutes.  Time spent blasting the corrector with a hair dryer is time I'll never get back for actually observing at the telescope.

 

We want some reasonable compromise that will give us freedom from condensation as well as show us a decent image.  Personally, I only do visual.  I've never done AP and I never will.  So I'm looking for some protocol that will provide decent visual images without a burdensome outlay of time and effort.  I'll leave the pursuit of perfection for the APers.

 

Mike

My solution is to pre-cool my C11 in a chest freezer using an external thermostat that I can set to somewhere around the expected ambient temperature later in the evening.  Plus, the freezer acts as a nice dust free case.  I use Reflectix to keep the heat out during the first part of the evening.  (this is a Reflectix threat, right?)  I got this idea from a long-ago tour of the Kitt Peak 4m scope-it was freezing in there during the day!  


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#225 choward94002

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Posted 17 January 2019 - 04:39 PM

@1072j ... yep, you're basically doing what Kokatha and Asbytec are doing, precooling the OTA to the expected low prior to use ... you're using a chest freezer, Kokatha uses a bag of ice, Asbytec uses frozen gel packs ... same idea, same great result!


Edited by choward94002, 17 January 2019 - 04:40 PM.



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