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Let's Hear It for CZ Quartz Mirrors and BL Fans.

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#1 Jeff B

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Posted 11 July 2018 - 03:49 PM

Basically what the topic title says.  I reinstalled my Parallax/CZ 11" F7.3 Newtonian on the AP 1200 the other day to measure the system up for another Telegizmos 365 cover and take advantage of the extended bout of good weather we are having here locally (with sometimes excellent seeing too...for around here anyway).  It had been parked and covered in my basement for a couple of years.

 

Well the system ROCKS.  Period.  

 

I carefully collimated the system and the views of Jupiter and Saturn have been just flat out great.  The mirror is quartz so it holds its figure pretty good during cooling but I can still get thermal plumes off the face.  So I use the boundary layer fan to blow it off.  And it works wonderfully.  Sans fan on, I can see small pluming coming off the mirror with in/out of focus star images (basically a V shaped bites out of the rings) but the viewing is very nice with sharp detail on Jupiter and Saturn  However, turning the fan on just seems to make the image "cleaner" with more "pop", especially at high power.  It's quite repeatable too.  

 

Before I did any collimation tweaking though, I was struck by the sharp detail on Jupiter but noticed the moons, while distinct disks, were showing a little flaring to one side during moments of unsteady seeing.  Sure enough, a star test show a collimation issue and my Glatter tools showed the secondary was fine but the primary was off a bit using the barlow (the center of the shadow of the mirror's triangular center marker was ~3/8" off).  This was easily corrected in less than a few minutes tweaking on push-pull screw set.   What I found interesting was that the effect of the improved image collimation on the image of Jupiter was rather small and similar to the effect of the boundary layer fan.  The effect was more noticeable on high power star images like the double double which now showed a nice airy disk and a good first ring that jumped around a bit but the dancing was now evenly distributed instead of bunched up on one side (the seeing actually let me see a distinct airy disk for extended periods, which for me is around 5 or more seconds at a time).  So, I now really do appreciate the user friendliness of slower newtonian optics.  

 

And boy, CZ makes some great mirrors and Joe at Parallax a very nice and sturdy OTA.  Well done gentlemen!

 

Jeff

Attached Thumbnails

  • Parallax Zambuto F7 B.jpg

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#2 Darren Drake

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Posted 11 July 2018 - 04:28 PM

What ever happened to the 16 inch f7 Dan Joyce mirror you used to have at your site?



#3 bvillebob

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Posted 11 July 2018 - 05:24 PM

This winter I got my 12.5" f/5.5 Zambuto 0.8" quartz mirror and I've been amazed at the views of Jupiter and Saturn, as well as the Moon of course.

 

What's struck me is how much my "seeing" has improved, meaning that much of my problems in the past have simply been thermal issues within my scope as I live in an area where the temperature drops like a rock after dusk.  With the new mirror my views have improved greatly.  On a decent night Jupiter now looks like a photograph with a layer of fine detail all over the surface that I've never seen before. 

 

It's been an expensive few years, adding bits of kit a little at a time, but the new mirror, combined with a Binotron and a pair of 18mm Delite eyepieces means I'm no longer cruising the classified as I don't know what I can improve from here.  Most of my viewing is planetary / lunar and I feel like I've achieved my dream setup, plus it's giving me all I'd hoped from it.


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#4 SandyHouTex

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Posted 14 July 2018 - 08:51 AM

I have a 16 inch Zambuto and it’s as perfect as it gets.  Great views.  However it isn’t Quartz, but that’s okay.


Edited by SandyHouTex, 14 July 2018 - 08:52 AM.


#5 Jeff B

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Posted 16 July 2018 - 09:42 AM

What ever happened to the 16 inch f7 Dan Joyce mirror you used to have at your site?

Darren, I believe you are confusing me with someone else.  But if there is a 16" F7 close by, I'd like to know that.  grin.gif



#6 TG

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Posted 16 July 2018 - 01:33 PM

I don't know what a "BL" fan is but here's a Zambuto quartz with a fan :grin:

 

Ju0Yex9l.jpg


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#7 Jeff B

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Posted 16 July 2018 - 01:56 PM

I don't know what a "BL" fan is but here's a Zambuto quartz with a fan grin.gif

 

Ju0Yex9l.jpg

Sorry but BL is short for Boundary Layer.  The fan blows over the front surface of the mirror to disrupt the boundary layer heat film that can form over the front face of the mirror during cooling/heating.

 

Jeff



#8 TG

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Posted 16 July 2018 - 05:09 PM

Sorry but BL is short for Boundary Layer.  The fan blows over the front surface of the mirror to disrupt the boundary layer heat film that can form over the front face of the mirror during cooling/heating.

 

Jeff

Yes, of course. I was thinking of installing one, suspended by wires in the shadow of the secondary, before I got the thinner mirror. 



#9 Jeff B

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Posted 18 July 2018 - 01:02 PM

Yes, of course. I was thinking of installing one, suspended by wires in the shadow of the secondary, before I got the thinner mirror. 

Actually mine fires in from the side, across the mirror face with a slight angle for impingement of the air and exhausts out another hole on the opposite side. 

 

Jeff 

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  • fan close up.jpg
  • Aft Cell.jpg

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#10 Pinbout

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Posted 18 July 2018 - 01:08 PM

 

a slight angle for impingement of the air and exhausts out another hole on the opposite side.

if you don't want any pressure developing and limiting the fan your soppose to open the other side to 2x area.



#11 MakeTT

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Posted 18 July 2018 - 01:21 PM

Thanks Jeff for the pics! At the very bottom of the tube i see black bars, is the mirror cell then attached direct to the reinforcing ring?

 

How about adding second fan for sucking exhausting air, would it be for vain?

 

Does Parallax Inst include an air filter for the fan and exhaust hole?

 

I am questioning because seriously interested in ordering the OTA of my future 10”f7 from PI.


Edited by MakeTT, 18 July 2018 - 01:23 PM.


#12 TG

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Posted 18 July 2018 - 01:24 PM

Actually mine fires in from the side, across the mirror face with a slight angle for impingement of the air and exhausts out another hole on the opposite side. 

 

Jeff 

Yes, this is how my MN66 has it. Don't want to cut holes in my nice StarStructure aluminium dob so I thought a suspended fan would work better.



#13 Jeff B

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Posted 19 July 2018 - 12:35 PM

Thanks Jeff for the pics! At the very bottom of the tube i see black bars, is the mirror cell then attached direct to the reinforcing ring?

 

How about adding second fan for sucking exhausting air, would it be for vain?

 

Does Parallax Inst include an air filter for the fan and exhaust hole?

 

I am questioning because seriously interested in ordering the OTA of my future 10”f7 from PI.

Yes, that is the mirror cell and it doe attache directly to the reinforcing end ring.  Very simple and tidy but it does stick out a bit.  I've attached a picture.

 

I've considered a second exhaust fan but it just plain works right now so I'm not inclined to spoil good with better and there is no filter on the BL fan so I will have to clean the primary from time to time.  I leave the BL fan running too.  However, I may install a fan to blow on the back of the primary even though it just does not seem to need one, but it would be an easy, no-cut, reversible mod.

 

Here is a picture of the scope in its new, poor man's observatory.  smile.gif   A Telegizmos 365 cover.  Actually, there are three covers involved, two of which are stock regular covers, which slide over and seal the front and back of the OTA.  It will be interesting to see how well the interior of the OTA and the mirror surfaces hold up.   The TEC 200ED has been bagged and tagged for almost four years now and it and the mount have held up very well with the only real issues being Asian lady bugs and stink bugs getting under the cover and into any opening in the mount they can find, which I've sealed up with good old duct tape.

 

As the scope is easy to un-bag and use, I'll be making more comparisons with the 200ED but for now, I'm really just enjoying it with Jupiter and Saturn right now.  Last week I saw Titan as a light pink-ish disk and dark/light smudging on Ganymede.  Not too shabby.

 

Jeff

Attached Thumbnails

  • Mirror Cell.jpg
  • Newtonian Bagged and Tagged.jpg


#14 Starman1

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Posted 20 July 2018 - 03:31 PM

A quartz mirror with the BL blown away will perform like a fully-cooled mirror.

A borosilicate mirror will still undergo figure changes until it cools, even if the BL is blown away.

 

However, if the mirror is thin enough (my 12/5" is 1.25" thick), BL fans and a rear fan can cool the mirror to ambient in about 30 minutes,

so if I start the fans in twilight, by the time it's dark, the mirror is at ambient.



#15 TG

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Posted 28 July 2018 - 04:42 PM

Looks like I may have had a BL fan without knowing it.

https://www.cloudyni...ndary-layer-fan


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