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First Light On My 20" f/3 Lockwood/JP Astrocraft

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#176 Bob S.

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Posted 08 February 2013 - 02:26 PM

I talked with John Pratte this morning who is at the Winter Star Party in the Florida Keys with his 25" f/4 Lockwood/JP Astrocraft telescope and his newly installed CBLMS (Comprehensive Boundary Layer Mitigation System). He advises that so far, he has not seen any appreciable additive features of the CBLMS in the very steady temperatures. He said with the front fan blowing onto the primary and the rear fan sucking in the enclosed mirror box, the CBLMS does not degrade the image but is not currently additive.

This is a very interesting piece of the puzzle that we are piecing together. When he gets the scope back to Illinois, it will be intersting to see how much difference is made. We already know that on my 20", when we only had the rear enclosed sucking fan going that the images immediately cleaned up on a warm mirror but eventually led to an overcorrection situation because we were running it on high speed for several hours not having had any experience with it to that point, and no front blowing fan to equilibrate the mirror uniformily at that point in time.

Here in North Florida, with this rather temperate Winter we have been having, the CBLMS has so far been effective and additive with every single use. It may turn out that when the temperature differential falls to a certain point that it will not longer be effective? Only time and continued experimentation will tell the story. Bob

#177 Bob S.

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Posted 23 February 2013 - 11:05 PM

It was gratifying to see an astrobud's setup today where he adopted part of the CBLMS for his 12.5" RCOS Classical Cassegrain imaging telescope. He mounted 4 very tiny MagLev fans on each of the short truss poles with vibration isolation blowing toward the center of his primary and says that he runs the fans 24/7. He has found that the blowing fans on the primary keep his scope closer to ambient than he has ever gotten. He has an SBIG 11000 attached to the scope on a AP1200 mount and plans to take pictures with and without the front boundary layer fans running and then evaluating the spot sizes of the photos. I can't wait to see the results of this experiment. The scope has the integrated rear sucking fans that are used for cooling the primary. Hopefully, at some point, I will try and convince him to put a control on the rear fans and bring them down to a slow speed to see if the comprehensive boundary layer mitigation system concept enhances his photos. He was mentioning that he can start and run the very tiny MagLev fans at 2.3 volts. My buddy Joe has taken many published deepsky photos and it will be interesting to see what tricks lie ahead for his advanced setup. Bob

#178 Bob S.

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Posted 26 April 2013 - 05:15 AM

Life has a way of distracting you from the things that really matter. I had a fellow named Josh Balsam who had built me a portable Bahtinov mask for my 20" JPA to get critical focus with my Mallincams or DSLR's to consider making me an apodizing mask. Carl Wright, an observer at CAV has extolled the benefits of apodizing masks for years and I decided that it was time to have my own. Josh utilized the scheme presented by one of the club members of the Colorado astronomical society and it arrived a few days ago. Last night with an almost full moon and Saturn close by was the perfect time to test out the apodizing mask. I did at least x6 A/B comparisons of the planet with and without the apodizing mask in place. 5/6 times, the image of the planet was sharper with the prismatic/psychedelic apodizing mask in place. I used my Leica ASPH zoom to get just the right amount of magnification to get the sharpest images when doing the comparisons for the slightly varying seeing conditions. I was also using the Comprehensive Boundary Layer Mitigation System with both front blowing and rear sucking fans working at their lowest speed to increase the sharpness of the image. The results were very pleasing and I can't wait to try it out on double stars. Suiter and others discuss the benefits of apodization. It appears to need at least 10" of aperture or greater to accomodate the reduction of light to the primary. Great fun and Saturn was showing very sharp ring detail but more interesting planet atmospheric detail/color than I am accustomed to seeing. Bob

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#179 Project Galileo

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Posted 26 April 2013 - 09:54 AM

This threat keeps getting better and better. :gotpopcorn:

#180 Bob S.

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Posted 27 April 2013 - 05:23 AM

Galileo, I suspect you meant thread but in a sense, this telescope is a "threat" to those unidentified tiny points of light far far away.

Last night, the seeing was predicted to be good and I wanted to further explore the benefits of my new apodizing mask with Saturn as the target. I rolled the scope out onto the mat it sits on to prevent thermals from the driveway after having stored it in the cool garage all day. I collimated it to perfection, turned on the CBLMS and then tuned the Starlight Instruments Paracorr System (SIPS) using my 17mm Ethos with the focuser backed out from the bottom 1/2 fine focuser turn and then rotated the SIPS until the stars were hard points of light. This particular procedure turns out to be easier than the manufacturers suggested procedure because I developed it after talking with Fast Mike who has a 28" f/2.75 with the SIPS and after following their procedures for setting the SIPS and found where the 17mm Ethos comes to focus. Sort of a reverse engineering technique which works well and does not require use of cellophane tape and supplied tube, etc. to tune the built-in Paracorr system. I then did my two-star alignment using Pollux and Arcturus and then viewed a couple of galaxies before Saturn and the Moon came up. I then pointed the scope at Saturn which was low and found that the views were mediocre. I had used my Leica ASPH variable zoom 8.9mm-17.8mm to align the scope and had it in about the 10mm position. I did an align on Saturn and went in for about an hour and watched some TV and napped a bit. When I came back out, the scope still had Saturn in the FOV. Did I mention that I love the ServoCat and performance of the JP Astrocraft telescope for the great precision and orthogonality?

I viewed until 1 a.m. EDT and the seeing appeared to get to 8.5/10 or better. I kept the apodizing mask on constantly while viewing Saturn to get the most possible contrast I could get. The ASPH ran out of magnification so I added a 2" 2x TV Powermate and placed the ASPH in it so I now had mag from 4.5mm-8.9mm. This translated to 1753mm of focal length with the 1.15x magnification factor of the SIPS device and mags of 197-394x in the range of the zoom ep. In the last hour of viewing, I was primarily using about 350-394x and with the apodizing mask, the contrast features on Saturn were pretty spectacular. I had studied Christopher Go's recent images of Saturn from the Phillipines and was trying to tease out visually as much as I could knowing what features Christopher had captured with his camera. The views were intoxicating.

During this time, I also got to wondering how my other eyepieces would stack up against the Leica ASPH with the apodizing mask in place. I used a TV 4.7mm Ethos, UO 7mm Ortho and 5mm Pentax XW in my 2x Powermate. If you reverse the order of listed ep's, you will note that in my very fast f/3 telescope, the Ethos put up the poorest image of Saturn with the colors rather muddled and poor resolving capability followed by better views but not great with my 7mm UO Ortho in the Powermate. The 5mm Pentax XW showed the second brightest image and the amount of detail was the best of the "also rans". The Leica ASPH was so absolutely superior for light throughput, neutral color and resolving ability in the Powermate that it was not even a contest. I was very surprised at how poorly the 4.7mm Ethos compared with all the variables in place to all of the other ep's. I love that ep for widefield stellar views as one of my favorites but on this night with my fast scope, relatively newly operated on eyes with crystal clear lenses in place following cataract surgery, the Ethos really did not perform up to any of the other ep's?

Well, I was absolutely delighted to spend the better part of the last hour going between 350x-394x with the Leica ASPH and my new apodizing mask. It was intoxicating and I really did not want to go to bed but have a busy day planned and so had to balance play with other pursuits.

The fast Lockwood mirrors and all of the supporting systems provided the best views of Saturn that I have experienced with this new scope. I am really hooked on the use of Josh Balsam's superb apodizing mask that was patterned after the Colorado groups build instructions. What a wonderful contrast booster! Bob

#181 Bob S.

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Posted 18 June 2013 - 05:15 AM

The 20" f/3 Lockwood/JP Astrocraft continues to follow on its journey's through space now via computer control. I recently installed Software Bisque's Sky X Pro planetarium software and this morning at 3:30 a.m. EDT was able to successfully slew to objects displayed on my 12" notebook computer via the Sky X program that is nicely tucked into the hooded control stalk that is located on the opposite side of the focuser. I first looked at M57, then M22, followed by Neptune and then M27. The Veil Nebula was up in Dobson's hole and the scope's limits would not allow slews to this area. I disengaged the drives but continued to use the Sky X to navigate to the Veil via the computer and hand movement of the scope and then hand tracked all around with a 31mm Nagler with an OIII filter in a Paracorr II. The views were beautiful!

Getting control of this instrument with a planetarium program was part of the initial build parameters and this goal has finally been achieved. My next adventure will be to not only control the scope with the Sky X but also toggle the computer screen to also control my Mallincam Xtreme astrovideo camera that outputs to a Watec screen on the UTA at the same time. The whole concept of fully integrating many different complex systems into one complete package is becomming a reality. Bob Schilling

#182 astrocrafter

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Posted 17 July 2013 - 04:53 PM

After Bob's enthusiasm over his CBLMS fan system on the 20" I built him, I had to modify my 25" f/4 Lockwood with a similar front/rear fan system.
I first tried the new arrangement at the WSP but couldn't tell much of a difference with or without the fans. I suspect the constant breeze and relatively constant temperature prevented much of a boundary layer from forming.

#183 astrocrafter

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Posted 17 July 2013 - 05:01 PM

My second trial was over this last weekend. I used antares as a target and compared how much of the time I could get a clean split with no fans, front fan only, or both fans. It appeared to give the best results with both fans running but it was nothing dramatic. The seeing overwhelmed the boundary layer effects. Again the nightime temperature drop was minimal. I'll continue to test and refine the system and report the results. There's a lot of variables to consider. I'd like to see how the system reacts to dropping temperatures.
John Pratte

#184 auriga

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Posted 17 July 2013 - 08:48 PM

Hi, John Pratte,
Well, as you know I have the mini version, the Sweet Sixteen 16"f/4, which in my case has Sky Commander and a fan and a Paracorr but no automatic drive. I love this scope and recommend it highly to anyone considering a 16" scope, the views are great and the scope works beautifully.

I am big fan of short focal length scopes that can be used sitting down. I saw a drawing of one, many years ago in the frontispiece of the three volume Amateur Telescope Making, and was hooked immediately; that drawing appeared to be about a 10" f4 or so. It made sense to me immediately, much more attractive than long Newtonians or refractors.

And the book, Telescopes for Skygazing, by Dr. Henry Paul, had some photos of his friend George Keene's 12" f/4.3, which was considered very radical indeed in those days when focal ratios shorter than f/7 were derided. I was envious, never dreaming that thanks to John Dobson, much larger reflectors could be made portable.

The combination of Mike Lockwood's great fast mirrors and your fabulous telescopes has been revolutionary. it took courage on both your parts to do this. Innovation isn't easy though it can be fun.

Credit must also go to Al Nagler, whose Paracorrs made short Dobs feasible. In some sense a Paracorr-equipped scope is a compound scope.

And in this instance, credit also to Bob Schilling for having the courage to try new things.

John, you and I and the prize-winning telescope maker Ross Sackett, and the late mirror maker and telescope maker Dick Wessling, constitute a small band of devotees of integral wheels.

I am glad to see that Bob Schilling has joined us in this enthusiasm. I have found it hard to convince people of the merits of integral wheels, but I am greatly enjoying them on the Sweet Sixteen; just tilt and roll.

Looking at the photo of the 25" on your web site I realized for the first time that integral wheels and the wheelbarrow system can easily be used on the same scope, one for tilting and rolling in and out of a garage, and one for wheeling up ramps into a van.

Once again, thanks for a beautiful scope, so easy to use. The views of the summer objects at Stonelick State Park last weekend were glorious.

Best regards,
Bill

#185 Bob S.

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Posted 18 July 2013 - 07:57 AM

Bill, I have assuredly joins the ranks of believers that integral wheels on a telescope make all the difference in terms of easy deployment. John Pratte very cleverly devised a system on my 20" where there are two sliding bolts on the rear, an articulating turnbuckle on the front of the scope to lock in the altitude movements and a drop in bolt that stabilizes azimuth movement. This all works in concert to just tip the scope over after grabbing the UTA and rolling it out to its observing position.

The extra cleverness employed by John was that the wheels can also be mounted on the axles of a pair of wheelbarrow handles that John crafted to roll the scope up a ramp as you had mentioned.

As recently as last night, I wanted to get some quick looks at Saturn. I rolled out my 20" f/3 Lockwood/JP Astrocraft and also rolled out my AP130 EDT that is mounted on a rolling G11 tripod with a DM-6 alt/az head attached. The views of Saturn were exquisite with the AP130 but there was so much more detail available with the 20" Newt where a higher number of Saturnian moons were observed.

I am so hooked on the ease of rolling equipment that my AP900 mount that is used with my 6" Lunt solar scope is also on wheels so I never have to lift a thing.

When you get scopes that are designed for ease of use, they simply seem to get more use :jump: At least, that is what I have experienced.

In terms of John using the Comprehensive Boundary Layer Mitigation System (CBLMS), I ALWAYS observe with the 20" with both the blowing front fan onto the primary and rear sucking fan with its annulus around the primary and enclosed back of the mirror box to scrub the boundary layer off of the primary. As John has found, the benefits in steadier temperature conditions seem to be less but they always seem to be better than not having both sets of fans running at the same time in any conditions. As John stated, the variables of front and rear fan speeds are still an unfolding story for him as well as myself.

Bob

#186 Bob S.

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Posted 27 September 2013 - 09:40 PM

Astro Buds, It has been a really rainy summer in North Florida. However, there is a dry mass of air coming in overhead and I got out the trusty 20" f/3 JP Astrocraft tonight. I was initially looking up with a Leica ASPH 8.9-17.8mm zoom that I used with the scope at 5:30 a.m. Eastern to look at Jupiter and the Moon early this morning. The seeing was so-so this morning. It is a little better tonight but not spectacular. Since I have a Mallincam Hyper astrovideo camera with focal reducer resident in the scope's holster and a 3.5" color LCD Watec monitor also permanently mounted on the scope, I decided that it was time to see some old friends in living color. The Mallincam turns my 20" f/3 into something like a 100-150" telescope in terms of what can be seen in detail and color. The "Pillars of Creation" (M16 - Eagle Nebula) were spectacular at 14-28 second integrations of the camera. More than that and the image was blown out because I am effectively operating the scope at about f/1.8 which really reduces the need for long exposures.

M17, M20 and M8 were all beautiful! I especially like seeing both the pinkinsh/red emission portion of the Trifid and the striking blue portion of the reflection part of the nebula. M57 was pretty unimpressive with an eyepiece but the two central stars, the "ears" and the two stars in the ring with pinks, greens, and whites are beautiful with the internal zoom of the camera on.
The advantages I am experiencing with a scope that is designed for both visual and astrovideo with little pain in terms of setup really seem to be paying dividends tonight. This has been an interesting 15 hours today because I was fortunate enough to spend about 30 minutes mid-day with my Lunt 152 solar scope and the views showed a lot of activity on our closest star. Other than about 5 glorious days last New Moon period, it has been a tough Summer for clear skies here in North Florida. Glad that Fall is just around the corner with better skies to come. Bob Schilling

#187 Relativist

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Posted 27 September 2013 - 10:37 PM

That's awesome, do you plan on broadcasting on NSN?

#188 Bob S.

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Posted 27 September 2013 - 10:43 PM

That's awesome, do you plan on broadcasting on NSN?


Curtis, Probably not at this time. It would seem to add a bit too much overhead to my workload. However, I have a laptop computer integrated into the telescope that resides in the computer/Argo/control hood that will talk with both my Mallincam Xtreme that I have as well as the Argo Navis/Servocat system through Sky X. As you can imagine, for me, all of these "dodads" seem a bit daunting and I am going to have to work my way into seamlessly using all of the components and then adding broadcasting. Seems very doable and I suspect in this coming year it will happen even though I am getting a bit long in the tooth to be trying to integrate so many activities into a session :help:

#189 Relativist

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Posted 28 September 2013 - 01:08 PM

I suggest if your wanted to broadcast you could get help from the experienced people over on the VEAA forum and on NSN. I am working on getting set up to broadcast as well, but my motivation is low as I have access to only a sliver of sky from my balcony at home. It sound like your very close to having all the elements there, since the main difference would be that instead of sending the mallincam output only to the monitor you would also send it through a video converter into the computer.

#190 Bob S.

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Posted 09 December 2013 - 09:07 AM

Well, the saga of the 20" f/3 1.25" thick Lockwood/JPA continues. I brought it to my darker site this past month for different nights of viewing. As many of you will remember, I have maglev fans on potentiometers both blowing on the front boundary layer and a rear fan with an annulus around the primary sucking air out of the back of an enclosed mirror box. What is very interesting about these experiments is that the results remain equivocal. On some nights, the fan systems are additive, on other nights the rear fan can be subtractive in terms of the scope's performance. On one particular night with the primary equilibrated, turning on the rear fan while the front fan was not blowing on the primary caused a noticeable darkening of background contrast while looking at the double cluster in Perseus. On other nights, the effect was not noticed.

Another astro-bud and I surmised that the reason that there is so much controversy about fan use in open tube Newtonians is that there appear to be a lot of variables that must be interacting to make the fan systems sometimes additive, sometimes neutral and sometimes subtractive in the performance of the telescope. I hope at some time to figure out what these variables may be but for the time being, I just have to experiment each night to ascertain what works best for the particular circumstances I am dealing with on a given night. The bottom line is that I am very glad that I have these fans systems in place and generally find that at least the front fan that is hidden in the shadow of the secondary gently blowing away the surface boundary layer seems to be consistently additive or at worst neutral in the performance of the fast Newtonian. Bob

#191 Cotts

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Posted 09 December 2013 - 11:22 AM

I am inspired by this thread to look into installing a suspended front fan in my 16" Teeter/Zambuto. The even cooling of my mirror is a big issue here in the Great Lakes area on most evenings. The Teeter design has a small fan blowing on the back of the mirror but it is not variable rate. I think I could turn it around to 'suck' air from the back while the new front fan blows on the front. (would simply reversing the wiring reverse the fan?) The trick for me will be to find a fan small enough to 'hide' in the shadow of my 3.1" secondary mirror....

This will be a nice winter project....

Dave

#192 Pinbout

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Posted 09 December 2013 - 11:29 AM

do you think this will be small enough

http://www.mpja.com/...tinfo/30321%...

#193 Cotts

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Posted 09 December 2013 - 12:31 PM

Danny, that's a tiny one for sure, maybe too tiny. My diagonal is 3.1" diameter so a fan with a housing diagonal of 3" or less would do... A bit of trig gives 3.00"/1.414 = 2.12" maximum side length for a square housing.

I've just been looking for the MagLev fans which are virtually zero vibration.

Do you know of a source?

Dave

#194 mark cowan

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Posted 09 December 2013 - 02:37 PM

There are easily available low noise fans for computer cooling that use magnetic suspension bearings - but they're not called "maglev". Off hand no I don't know which they are.

Best,
Mark

#195 Cotts

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Posted 09 December 2013 - 03:41 PM

Here are the maglev fans. clicky thingy

I have found distributers here in Canada for these. "Maglev" is a brand name, though, from SUNON,, a Chinese manufacturer.

Dave

#196 Achernar

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Posted 10 December 2013 - 05:46 PM

I agree, at the Deep South Regional Stargaze I was reminded of that climbing an aluminum ladder to peer through a 25-inch F/4 truss-tube Dob. This and the fact there is no way I could keep a bigger telescope in the house and still get it through the door was why I opted to build my 15-inch F/4.5. It's still a work in progress, I am upgrading the secondary mirror from a 2.6" to a 3.1" minor axis diagonal to get better edge illumination with my low power eyepieces. The eyepiece height is perfect, no ladders needed and I like sitting in a chair while looking through it. I can only imagine just how much better the views would be through that 20-inch F/3...... :drool5:

Taras

#197 astrocrafter

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Posted 10 December 2013 - 06:43 PM

Dave,
if you want to stay within the secondary shadow with the fan it has to be smaller than your 2.12" as the shadow of the secondary is converging after reflection.
John

#198 GeneT

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Posted 10 December 2013 - 08:53 PM

I am not jealous, I am not jealous, I am not jealous. . . . :bawling:

#199 Cotts

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Posted 10 December 2013 - 10:10 PM

Dave,
if you want to stay within the secondary shadow with the fan it has to be smaller than your 2.12" as the shadow of the secondary is converging after reflection.
John


The light cone converges after reflection from the primary, that's for sure, and continues to converge after hitting the secondary and exits the tube sideways.. The 3.1 "secondary 'eclipses' the incoming light which is arriving parallel to the scope axis. There is no convergence of this shadow. It is the shadow that we see when the scope is out of focus. You can hide anything you like behind this shadow as it contains no light.

Dave

#200 Howie Glatter

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Posted 11 December 2013 - 07:04 AM

You guys are making me think before my coffee, but I have to agree with John.

"There is no convergence of this shadow."

That's right, but we don't want to observe the details of the shadow, it's the sky we are interested in. The marginal rays that graze the edge of the secondary on the way in converge after reflection from the primary on the way back up to the secondary, so you need a smaller fan to avoid blocking the smaller circle of converged marginal rays.






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