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Questions About Insulating SCT's with Reflectix

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#326 Rustler46

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Posted 29 July 2019 - 12:06 AM

Last night I was able to perform a test (of sorts) of the effectiveness of the insulation wrap in preventing dew formation. The "of sorts" came about when shortly into the observing session, power to the DewBuster controller was interrupted by my PowerPole extension cord failing. This was due to one of my crimp connections pulling loose from the PowerPole connector. This was easily remedied by crimping some new terminals on the extension cord. I highly recommend getting a PowerPole crimper - it will save much work and frustration. Crimping is actually better than soldering the connections. It is the best $40 you'll spend.

 

But the results of my unplanned for test is that over the course of the next two hours, the insulated (but unheated) Celestron-11 had nary a trace of dew formed on the corrector. In contrast my folding table holding eyepieces, iPad and WO binoviewer had quite a bit of dew. 

 

One of my goals for the evening was to check and adjust collimation if necessary. Seeing was good early on. When I looked at a slightly out of focus star image, there was a single ring with the Poisson spot exactly centered. So no adjustment was needed. That was the best collimation I've had on the C-11 for quite some time. It allowed  for interesting views of Jupiter and Saturn. I also employed the ZWO ADC (Atmospheric Dispersion Corrector) to re-familiarize myself with its operation. When adjusted to best effect, the color fringes on Jupiter were gone, and I was able to see the shadow of Ganymede just finishing its transit of the disc.

 

So now I'm ready to move on re-entering the field of lunary/planetary imaging. This will be with use of the C-11, ADC, ZWO ASI290MC camera, and FireCapture Software. I'll post my progress on the Solar System Imaging forum.

Another test of the insulated Celestron-11.

 

The faulty PowerPole cord was repaired and functioned properly. The problem with the previous attempt was that I had not used the best size connector. They come in 15- 30- and 45-amp versions. The difference between these three is only in the size of wire that the crimp connection accepts. I had used the 45-amp version which accepts 10-gauge wire. The actual wire in the cord was only 14 gauge. So when I fashioned the replacement cord it was crimped into the more appropriate 15-amp terminals. This makes for the tightest crimp on that small gauge wire. For all three amperage versions the actual rating for the disconnect/reconnect contacts is 45 amps. To reiterate - only the size of the wire crimp connection varies between the three.

 

These power Pole connectors are highly recommended and used in Ham radio, most all fire, ambulance and other emergency organizations. While there is provision for plus and minus (red or black) receptacles, these connectors are genderless - that is there are no male or female connectors.  In contrast the ubiquitous cigarette lighter plugs have male and female connectors. They are acceptable for less than 5 amps. The spring-loaded tip works to push the plug out of its receptacle. 'Nuf said about the superiority of PowerPoles.

 

As for use of the dew control system, the DewBuster temperature differential (OTA to ambient) was set at 3°F rather than the previous 5-7°F for the uninsulated tube. After over 2 hours of use there wasn't any trace of dew on the corrector when I packed everything away for the evening. Heat was being applied to both OTA and metal dew shield. The duty cycle was low, with the heaters being mostly off. Early on the seeing wasn't particularly good. But for the last hour, I found Saturn to be very crisp. Seeing was then much better. And I was able to use powers of 310X to good effect. So I would surmise that tube currents on either side of the corrector were minimal. Collimation looks to be as perfect as In could get.

 

In summary, the insulated SCT OTA is a big improvement over the uninsulated one. This is true both for dew prevention and minimizing tube currents. So am moving on to lunar/planetary imaging. Thanks to everyone for the comments, tips, enlightenment provided by the discussion.


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#327 WadeH237

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Posted 29 July 2019 - 11:25 AM

I just thought that I'd post to this thread on my latest observation using my C14 with a single layer of Reflectix.

 

I'm set up at the Oregon Star Party site, and have the C14 under a TG365 cover during the day.  Normally, I add the Reflectix blanket when I uncover the scope in the evening.  But the other night, I wanted to do some star testing and collimation tweak, which is really difficult to do with the dew shield and Reflectix in place (unless you are 9 feet tall...)

 

Normally, with the Reflectix, I don't see any tube current plumes, even a few minutes after starting to observe.  The other night, without the Reflectix, it took about 3 hours for the plume to clear up - and this was with the scope starting out from already being outside under the TG cover.

 

This is why I use the Reflectix.  I realize that I probably won't get optimal performance, but it is a huge improvement versus not having it.


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#328 elwaine

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Posted 29 July 2019 - 05:47 PM

I just thought that I'd post to this thread on my latest observation using my C14 with a single layer of Reflectix.

 

I'm set up at the Oregon Star Party site, and have the C14 under a TG365 cover during the day.  Normally, I add the Reflectix blanket when I uncover the scope in the evening.  But the other night, I wanted to do some star testing and collimation tweak, which is really difficult to do with the dew shield and Reflectix in place (unless you are 9 feet tall...)

 

Normally, with the Reflectix, I don't see any tube current plumes, even a few minutes after starting to observe.  The other night, without the Reflectix, it took about 3 hours for the plume to clear up - and this was with the scope starting out from already being outside under the TG cover.

 

This is why I use the Reflectix.  I realize that I probably won't get optimal performance, but it is a huge improvement versus not having it.

Wade, use a double wrap of Reflectix around the C14 and cool down time will be a thing of the past. (If you want less bulk and more insulation, use Prodex. It's 1/2 the thickness of Reflectix and has twice the R value... but it is expensive because they do not sell it in small quantities.)


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#329 Bean614

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Posted 29 July 2019 - 06:38 PM

Wade, use a double wrap of Reflectix around the C14 and cool down time will be a thing of the past. (If you want less bulk and more insulation, use Prodex. It's 1/2 the thickness of Reflectix and has twice the R value... but it is expensive because they do not sell it in small quantities.)

And, put on the Reflectix and leave it on.  When you "uncover" the scope it's ready!  My Reflectix stays on, whether my scopes are stored indoors or outdoors.


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#330 WadeH237

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Posted 29 July 2019 - 06:46 PM

And, put on the Reflectix and leave it on.  When you "uncover" the scope it's ready!  My Reflectix stays on, whether my scopes are stored indoors or outdoors.

I can't leave it on without leaving the scope (including the corrector) exposed during the day.  The blanket that I made is from a 48" roll of Reflectix and is long enough to reach from the back of the telescope, to just about 1/2" or so from the front of the dew shield, all in a single piece.



#331 Bean614

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Posted 29 July 2019 - 07:13 PM

Sure you can! You mentioned that it's under a TG-365 cover.  Exactly what I use on my Nexstar-11 GPS.,  Which is out on my deck ALL the time, in New England weather and storms, -20F to 104F.  No problems (knock on wood).



#332 davidc135

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Posted 30 July 2019 - 09:14 AM

My 8'' Meade is covered in two layers of Reflectix, including the back and dew shield and needs some cool down time, though not much. Views of Jupiter and Saturn were limited by seeing and the planets' 16 deg altitude last night and took 15 to 20 minutes to improve from bad to as good as they were going to get.  David



#333 Sarkikos

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Posted 30 July 2019 - 09:33 AM

Wade, use a double wrap of Reflectix around the C14 and cool down time will be a thing of the past. (If you want less bulk and more insulation, use Prodex. It's 1/2 the thickness of Reflectix and has twice the R value... but it is expensive because they do not sell it in small quantities.)

Maybe some savvy entrepreneur can buy a large quantity of Prodex and sell it in smaller quantities - with a reasonable markup - to interested amateur astronomers.  :thinking:

 

Mike



#334 elwaine

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Posted 30 July 2019 - 11:03 AM

I can't leave it on without leaving the scope (including the corrector) exposed during the day.  The blanket that I made is from a 48" roll of Reflectix and is long enough to reach from the back of the telescope, to just about 1/2" or so from the front of the dew shield, all in a single piece.

Wade, I made a two-piece jacket: one for the OTA and one for the dew shield. After attaching the dew shield to the OTA, I use a wide strip of Velcro at the join to make sure the dew shield stays on the OTA during slews, etc. When I've finished viewing, I release the Velcro, remove the dew shield, and attach the protective front lens cap. I never remove the insulation from the OTA or from the dew shield.

 

(Note, I wrapped an outer layer of white rubber foam over my "silver" insulation - in part for for aesthetic reasons - but I see no reason a two-piece jacket of Reflectix won't work on you C-14.)

 

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