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[novalab]

This is a great forum, probably the best on the web, and I finally decided to join after running into your articles on numerous occasions (Google).

I live in Southern NH, under fairly descent (compared to Chichago) Mag20+ skies. I am an electrical engineer, and a physicist by profession. I have been pass time astronomer for many years, and greatly enjoy observing, and even more building new equipment and modifying the old. Some of Joe’s articles on C11 came in very handy to develop my own ideas.

I have 2 backyard domed observatories, which are totally automated and I mostly observe remotely while watching the re-runs of Hawaii 5-O on Netflix (I have to keep XYL happy too). My main scopes are CDK 17” (homemade except for the optics), and C11, both with a cluster of smaller refractors which I all use for specific observing programs. I do a lot of photometry work (AAVSO), as well as deep sky imaging. I mostly find things interesting if they are billions of LY away. The furthest I got so far was 11gly, after many hours of imaging.

I look forward to sharing some of my past projects with the group, and I hope it will be useful to you all.

Clear Skies!

[Chicago Astronomer - Astro Joe]

Novalab....

Welcome to the Chicago Astronomer!

Thank you for the kind words and enthusiasm in astronomy. The internet is wonderful gift and pleased to see that our activities are reaching out beyond the immediate Chicago Area.

Two observatories - no waiting....I dig that. Very cool.

And also cool is "while watching the re-runs of Hawaii 5-O on Netflix"

(The old show is very slick and this new one should be called something else, cause it ain't no 5-0, just punks running around.)

Please do share your work here with us and glad you found us....! ;D

[novalab]

Thanks Joe,

I wholeheartedly agree with your 5-0 comment. This also tells me that we are likely in the same age group.

I will be posting interesting stuff as I run across it, and also some work I did in the past, similar to the articles you did on the C11. I found them to be very informative, and I got few ideas from them.

Chris

[Paulie pchris00]

Again, welcome Chris. I'm glad you found the forum, and look forward to reading your work. (Just be ready for a lot of questions. You seem to be working at quite an advanced level).

[novalab]

It will be my pleasure to help whenever I can. I am actually just modifying another C11 to a CF tube, adding 4 fans, mirror locks, internal tube temp sensors, tube and barrel flocking etc. This time, I am taking lots of pics, so I can do a nice article on the project.

[Chicago Astronomer - Astro Joe]

Chris....

All worthy mods.

I was doubtful on flocking before I did it on the C11, but the returns are great and helps with the damned light pollution nicely. The temp sensors are nice too. I have found the in/out temps do not vary much - at most a couple of degrees - tops. I like the idea of the mirror stops.

Fans are good, but I have read that they can cause more trouble and turbulence than original.

I am anticipating your project.

[novalab]

Hi Joe,

The reason for flocking is the issues I am having with the IR from the sky glow. It appears that there are serious reflections from the baffle tube, and only give me trouble in the IR. Basically, I can see it as a faint ring in the image when I do the flats, and if the sky is bright like when low on the horizon. This is not surprising, as anodized Al is a pretty good reflector of IR. While I’m at it, I will also do the main tube, mainly to cover the wires. The secondary baffle too.

The sensors are mainly used for the focus correction. The tube will be held by the Parallax rings, and I only expect to see the contribution due to the CF tube, which is about 5X less than the Al. However, the CF is a bad conductor and has low heat capacity, so I am mounting some SO-8 package surface mount sensors on the inside, directly bonded to the OTA using conductive epoxy. They will be also insulated from the internal air, so that I only sense the CF temperature. On the Al, mounting the sensor on the outside, is OK, but still I found that having some foam to insulate from the air is important. I use an absolute worm driven focuser (Clement), and have found that in CF I basically never, ever need to refocus, once I am calibrated. Yes, even at the session beginning. BTW, these are all fixed scopes.

Fans… I am in two minds about those. CF + the flocking is a very good insulator. At the very least, I can turn them on while the system is stabilizing, which is more of an issue during the hot months. If things look good, I may leave them running, so let’s see. I am using very small fans, probably not more than 20CFM thru the 45PPM filters. I will admit that am not crazy about blowing the air (fine dust) dust into the scope. Pollen particles are very small, so I may use it sparingly.

I also bought some very small blowers, about 5mm thick that I am contemplating placing flat on the inside of the CF tube, between the primary and the corrector. The idea being they will help mix the air in that region. They are tiny, and only blow about 2CFM each. I’m still thinking about putting 4 of those inside. They all have separate connections on the8 pin mini-DIN, so I can turn them off if they cause issues. All the fans are remotely controlled anyway. What do you think of this idea?

[Chicago Astronomer - Astro Joe]

Chris,

On the C11, I flocked all light paths and it will help to knock off your IR issue nicely. It also darkens the FOV.

With introduction of the fans, even filtered....I think a more frequent cleaning regiment would be required - forcefully introducing outside air into the tube. Not a deal breaker, just a potential maintenance one. Here in Chicago, a film lays on the outside of the Corrector plate. This after cleaning thoroughly before the observing season. The airborne pollutants settle on the glass soon afterwards.

[novalab]

I know the film you are talking about… I am close enough to Boston to get this here too, but it takes few months. Same with the filters. Still, I am not too crazy about having to clean primary, or the secondary. As is my scopes are hermetically closed, the correctors sealing the other end. I am planning to mount the fans on the inside of the OTA (due to clearances to a large focuser), and am toying with the idea of not opening up the holes in the back at all. Just space the fan few mm from the back plate. The idea being that it will transfer the heat between the mirror and the rear Al plate. Not ideal, but I improved from nothing. I mean, I already have the OTA open… What do you think?

BTW, all my scopes have been modified as to be able to open them without taking out the corrector plate. I have 12 of 1” long about ¼” thick small Al plates, with the arc machined into them glued to the inside of the OTA. They act as the fixed nut, so you just unscrew the outside fasteners and lift whichever end you want – or both ends. I often lift the tube with the corrector still attached, just to service the primary. Upon closing, it often does not need any re-collimation. I already have this on couple of C11s, and couple of C8s, and works like a charm. Will describe it with some pics when I get finished with this scope.