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Equipment Discussions >> Reflectors

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Scanning4Comets
Markus
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Loc: Ontario, Canada
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5635178 - 01/21/13 03:12 PM

Awesome Bob!

Cheers,


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Scanning4Comets]
      #5635377 - 01/21/13 05:14 PM Attachment (103 downloads)

Markus,
I realized that the photos of the JPA control center were not very good and were taken at a time during the construction phase. Here is a current picture showing the control center in relationship to the entire telescope (the focuser and other controls are exactly on the opposite side of the telescope). The control center fabrication was a pretty involved process that took Pratte about three days to construct. You can also see one of the two powered-groundboard connection points below the rocker box and there is another connector on the other side of the scope in a foot so dependending on where I plan to spend most of the night viewing, I can keep the power cord well out of the way. One of my main criteria was to minimize any dangling wires.

Edited by Bob S. (01/21/13 07:21 PM)


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5635387 - 01/21/13 05:17 PM Attachment (87 downloads)

Here is a close-up of the quick disconnect plugs that allow the control center to be de-mated from the telescope in less than 5 minutes. It is supported by two attachment points and is relatively stable/sturdy. All of the connections are either color coded or have specific sized plugs that cannot be inadvertently interchanged. The connector on the side of the mirror box is where the S-video output is if I want to relay the image to a larger external monitor. I have been thinking about installing a transmitter coming off the S-video output plug and then simply have to hang the receiver on whatever viewing source I want the signal to be displayed on. What is also very cool is that John Pratte rigged up a set of wheelbarrow handles that can attach to the scope utilizing the wheels and also attach with the control center in place. There was not much left to chance thanks to his forward thinking on each component and how it was going to be integrated into the scope. You can see where the captive bolts on the wheelbarrow handles attach to the rearward part of the rockerbox. Bob

Edited by Bob S. (01/21/13 06:29 PM)


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Starman81
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5635454 - 01/21/13 05:59 PM

A true DREAM MACHINE!!

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PureHeaven
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Reged: 01/20/08

Loc: Los Angeles, CA
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Starman81]
      #5636061 - 01/22/13 12:58 AM

All those exposed wires and components make me nervous- I'd probably kick it or get tangled in it somehow- ever think of creating some kind of small protective cover? Might get in the way of the bearing...

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: PureHeaven]
      #5636314 - 01/22/13 07:10 AM

Quote:

All those exposed wires and components make me nervous- I'd probably kick it or get tangled in it somehow- ever think of creating some kind of small protective cover? Might get in the way of the bearing...




Frank, It does look like an electrical grid and when I first saw it, I had to have John Pratte explain each and every wire to me so that I knew what was going on. The nice thing about the location of the wires and the control center is that it was designed to be used standing. With the height of the hood and clearance away from the scope I don't think it will suffer much, if any punishment. Pratte even made a slight tilt in an aluminum drip channel on the rear of the hood at my suggestion that directs any condensation away from any of the electronics and falls harmlessly to the ground on only one side of the channel. The other side of the drip channel is blocked off to prevent any moisture from dripping onto the electronics. As is with any of our telescopes, the electrical systems are pretty much hardened and selected to function in a pretty wet (dew) environments which we definetly have in Florida many months of the year. My current challenge is to have AstroSystems make a custom cover so that the scope can stay out in the daylight during those times that I have it deployed in the field for numerous days under our hot Florida sunshine. Bob

Edited by Bob S. (01/22/13 08:47 AM)


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5644896 - 01/26/13 06:47 PM Attachment (66 downloads)

I have been asked what we used for a sucking fan on the rear portion of the mirror box. It is a Sunon Mag Lev fan that is about 4.5x4.5" and says that it has a minimum 127CFM. The fan is only about $22 mail order. I am not sure if that CFM rating applies when I turn down the potentiometer to it lowest setting before the fan stalls which is how I have it set when viewing. Of course I have it up at full sucking speed along with the front blowing fan when in the equilibration mode of the scope. I do not generally view with both fans blowing/sucking at full speed although the images still seem better than if the mirror is hot and radiating thermal plumes. This suggests to me that the fans system coupled with the annulus is not producing turbulence to such a degree that the images are being terribly perturbed and I keep the AstroSystems shroud up a couple of inches from the mirror box during this phase of active mirror cooling. Here is a picture of the fan. I will then show a detailed view of the rear of the mirror box.

Edited by Bob S. (01/27/13 03:01 AM)


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5644905 - 01/26/13 06:52 PM Attachment (67 downloads)

Here is the Sunon Mag Lev fan encased in the Sorbothane and surrounded by a solid metal backing plate than encloses the entire mirror box to create the necessary suction and increase the efficacy of the annulus in front of the primary. The reason we used the magnetic levitation fans was that they have an excellent reputation for having very low vibration and have long-life endurance. On the right upper portion of the picture is the potentiometer and just to the right of that is a little red switch that turns the fan on and off. The two bright screws in the upper portion of the mirror cell frame are the built-in contact points that power the rear fan unit when the enclosed mirror cell is installed. I used the switch to test the efficacy of the rear sucking and front blowing fan of the Comprehensive Boundary Layer Mitigation System (CBLMS) running seperately and combined. To date, the scope has shown more detail visually on Jupiter with both fans running at their lowest speeds than either one fan (front or back) or no fans running.

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5645570 - 01/27/13 07:46 AM Attachment (66 downloads)

I was asked about collimation of the scope with the front boundary layer blowing fan. The blowing fan is a Sunon MagLev KDE1207PHV1 which measures 2.75" x 2.75" The entire front fan ring that rides on 4 Sorbothane pads can be removed by turning two keeper tabs and disconnecting the RCA plug from the power source on the top of the mirror box. Alternatively, the scope can be slightly tilted and the front boundary layer fan can be lifted up and tilted out of the way to collimate the scope. As previously mentioned, the fan is run on high with the potentiometer for cooling or when the mirror is warm and then is run at its slowest speed when the primary is equilibrated.

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5645575 - 01/27/13 07:55 AM Attachment (81 downloads)

And finally, the requester wanted to see the relationship of the front fan to the primary and the annulus. The front fan is approximately 9" above the primary. The annulus surrounding the primary is approximately 1/2" larger in diameter than the 20" 1.25" thick Lockwood primary and approximately 1" above the primary and appears to be effectively creating a venturi effect that Mara Da Lio discussed. We chose to have the annulus closer to the primary than Da Lio had articulated because we have the front blowing fan. In tandem with the rear fan, the mirror appears to uniformily equilibrate. As some of you will remember, when we used the rear sucking fan and the annulus only, the mirror tended to become overcorrected due to the excessive cooling of the outer portion of the thin mirror according to Mike Lockwood as he inspected the initial performance in the field under the stars. The front fan blowing on the front of the mirror appears to gently scrub the boundary layer surface and the rear exhaust fan appears to laminarly remove the air rather than it being trapped inside the mirror box in the front of the primary mirror surface. We coined the term Comprehensive Boundary Layer Mitigation System or CBLMS which is a pretty ambitious moniker but seems to be living up to its billing. John Pratte is retrofitting his 25" f/4 Lockwood/JP Astrocraft and may have it completed in time for the 2013 Winter Star Party in the Florida Keys. If you get a chance, check out the scope's performance if you happen to make it there this year. The front fan is in the shadow of the 5" secondary and the support wires are oriented identically to the secondary spider to reduce any further diffraction spiking. You can also see that the primary mirror lower edge supports on the right side of the picture have teflon roller ends which allow the primary mirror to move freely in all positions without the risk of binding.

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5664587 - 02/06/13 02:16 AM

It appears that partial implementations of the CBLMS are bearing fruit for others. JohhnyHa said this on another thread yesterday: "Update: Last night using my new exhaust system on my mirror box, I had the best views of Jupiter ever in my lifetime. So it certainly isn't hurting to switch to the exhaust fan. I was able to go over 250X for the first time in months and months, with a perfectly stable, sharp image. I have never seen such detail on the disc, it was simply amazing. I was truly gobsmacked, I did not think my scope was capable of such incredible views from my backyard in Los Angeles. I recently switched to a thinner 14.5" Zambuto mirror and Protostar quartz secondary, and that combined with this new exhaust fan system has delivered the goods - finally - a beautiful, thermally stable image.

This is a simple 3 speed exhaust fan with a closed back, I don't have a di Lio baffle or any boundary fans installed at this point. I also had my 12V box fan about 8 feet from the scope creating a light breeze blowing my body heat away.

--------------------
Johnny

FS152
15" Obsession Classic"

It is good to see others experimenting and developing additional empirical evidence for the concepts of a comprehensive boundary layer mitigation system's (CBLMS) potential efficacy. I hope Johhny, if he implements a front blowing fan, will have it suspended over the face of the mirror and be able to set the fans speed very low to not create unnecessary turbulence. The Mauro Di Lio annulus will likely also be a very helpful addition to Johnny's 15" Obsession. Also, imbedded in Johhny's report is that fact that he was using a very small fan to blow his body heat away from the Newtonian. Daniel Mounsey for many years has extolled the benefits of this procedure and it too is likely an additive factor in Johhny getting the best views he has ever had. John Pratte, owner of JP Astrocraft is currently down in the Florida Keys with his 25"f/4 Lockwood/JPA and is experimenting with a complete CBLMS on his scope this week. I asked him to do all of the switching on and off of the front boundary layer blowing fan as well as the rear enclosed mirrorbox sucking fan to ascertain how the CBLMS works in very stable temperature conditions and what kinds of performance changes are noticed? Bob

Edited by Bob S. (02/06/13 06:07 AM)


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johnnyha
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5664728 - 02/06/13 07:13 AM Attachment (67 downloads)

Thanks Bob, this thread has definitely inspired me to try out some new thermal solutions. Yours is a work of art!

On my 15" - I think the baffle on the top of the Obsession box acts somewhat as a di Lio baffle, at least in the sense that I feel it is creating a very laminar air flow around the mirror. It's about 9" above the mirror but I think it helps. The important variable that I have recently changed is the flow of the fan, from blowing on the back of the mirror to exhausting air from the box. I have also coupled this with closing up the back of my mirror box with Protostar flockboard, a kydex-like material.

The Flockboard is also flexible and (very important!) I have formed it into a scoop top and bottom (see photo) which helps pulls air from around the mirror.

The theory here is that an exhaust fan can gently pull the air from around the mirror, whereas a blowing fan cools the mirror faster but just creates turbulence in the box.

A small scrub fan placed above the mirror like yours Bob, is the obvious next step, along with a di Lio baffle - but meanwhile with the results I had last night I'll wait -...

Truss dob exhaust fans, unite!


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: johnnyha]
      #5665059 - 02/06/13 11:45 AM

Quote:

Thanks Bob, this thread has definitely inspired me to try out some new thermal solutions. Yours is a work of art!

On my 15" - I think the baffle on the top of the Obsession box acts somewhat as a di Lio baffle, at least in the sense that I feel it is creating a very laminar air flow around the mirror. It's about 9" above the mirror but I think it helps. The important variable that I have recently changed is the flow of the fan, from blowing on the back of the mirror to exhausting air from the box. I have also coupled this with closing up the back of my mirror box with Protostar flockboard, a kydex-like material.

The Flockboard is also flexible and (very important!) I have formed it into a scoop top and bottom (see photo) which helps pulls air from around the mirror.

The theory here is that an exhaust fan can gently pull the air from around the mirror, whereas a blowing fan cools the mirror faster but just creates turbulence in the box.

A small scrub fan placed above the mirror like yours Bob, is the obvious next step, along with a di Lio baffle - but meanwhile with the results I had last night I'll wait -...

Truss dob exhaust fans, unite!




Johnny, The idea that you are using a rounded rear baffle is an interesting wrinkle to the experiments. John Pratte and I toyed with and are still considerig some kind of a kydex ring around some part of the rear portion of the primary mirror to enhance the sucking effects of the rear fan. I have such a strong fan that it may not be necssary and with the variable potentiometer, I can pretty well control the velocity but do not know how much CFM I am actually exhausting?

Keep up the good work. As you have now found, the "juice is worth the squeeze". I suspect that the trick for closed tube fans is to adopt our same strategy for the rear enclosed sucking fan but unlike our larger Newtonian that can have a front blowing fan on the center of the primary, people may want to adopt a neat little device that has shown some efficacy in my 10" Portaball or just build in a small Mauro Di Lio annulus to create a venturi effect from the sucking fan? Much more work needed on those issues I am sure.

In the new PB, they are now installing a very tiny boundary layer mixing fan that is on a swivel base that is just above the primary mirror's surface. When I turn on this tiny little fan, it seems to gently mix the air on the surface of the primary. The effects are not nearly as dramatic as the CBLMS. I think it might be adantageous to reverse my cooling fan on the PB and use it to suck air out of the back of the ball. I have not given that much thought at this point. Bob

Edited by Bob S. (02/06/13 04:45 PM)


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DuaneS
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5666674 - 02/07/13 09:10 AM

Bob - it looks like you got yourself one very nice scope!! Having a thin mirror has to help tremendously. My almost 2" thick mirror is often 6 degrees or more above ambient temperature, even when running a large fan on the back. iam working on an idea for a fan box that "may" help bring the temperature of the mirror down a little bit quicker. Again, very nice scope you have there!

Duane


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: DuaneS]
      #5667434 - 02/07/13 04:29 PM

Thanks for the kind words Duane. It was a fun labor of love on John Pratte's part as well as my own. Not to forget mentioning that Mike Lockwood said he nailed it on the 20". Of course, your 30" scope is a real performer and getting that large slab of beautifully figured glass to equilibrate has to be a challenge. I have gotten reports from John Pratte that Joe Wambo's 32" Lockwood/Webster is really smoking down at the WSP in the Florida Keys this week and he of course has the front fan in the shadow of the secondary which is very much like my front fan unit and was the prototype for my fan. Of course they are not experiencing more than about 6-8 degree temperature shifts in a 24 hour period which makes things easier. Look forward to hearing what you do to get that big mirror equilibrated. Whatever you do, I would consider a front fan. It seems to really help with the views in Wambo's big scope and really is additive in my 20". The CBLMS that we developed is also based on the contribution of Jimmy Lowery who is cooling his big 48" with an enclosed rear mirror box and ten mag lev fans sucking the warm out of the back of the telescope while cooling his large mirror and apparently helping to scrub his boundary layer because he reports that it is always better to just leave the fans on. He says that just that application of fans in an enclosed mirror box greatly improves his images and he leaves them on all of the time. You might want to get in touch with him and see what he might recommend for you. I suspect that if you incorporated a fan system like Pratte designed that you would likely overcome most of your thermal issues? Additionally, Mike Lockwood and Mike Zammit could give you further suggestions I am sure. Bob

Edited by Bob S. (02/07/13 05:25 PM)


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5669175 - 02/08/13 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

Edited by Bob S. (02/08/13 08:41 PM)


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5697533 - 02/23/13 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

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5823645 - 04/26/13 06:15 AM Attachment (45 downloads)

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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Project Galileo
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5824096 - 04/26/13 10:54 AM

This threat keeps getting better and better.

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Project Galileo]
      #5825733 - 04/27/13 06:23 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

Edited by Bob S. (04/27/13 06:35 AM)


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