March 2, 2012 at 2:43 am #2580
So, Ravnostic pretty much hit the nail on the head the other day when he retorted to my last picked at kickball comment with watching from the sidelines. Because that’s what I did in Elementary school. But, it was okay because I had my own cool nerd things to do. Only now, I’ve been sitting back watching you guys do all the cool nerd things while I’m over there playing kickball and feeling left out. Especially with all the new toys and whatnot and everyone gearing up for what might be the biggest astronomical year in a while.
So, I blew off my incredibly long list of things I need/should be doing, and I blew off my family input of “you don’t have time to worry about the space shit now,” and I went out to the garage to find out exactly what I had.
I started at the mount:
Best I can figure (correct me if I’m wrong), is that I point it at geologic north using the z-axis, then use the bolt atop the center body to adjust to the angle of my longitude, such that the axis of the main shaft points at true stellar north. Then I’ll set angle and ascension with the main shaft axis and the cross axis and lock those in.
The screws to lock the main axis to the bull gear are allen screws. Would it be unwise to replace them with large-knob thumbscrews to avoid “hurry up and clamp it, saturn’s moving!” situations?
I plugged it in and ran a test. With the bull gear locked, over the course of an hour, it was pretty much spot-on with sidereal motion. Exactly 15 degrees in 60 minutes.
Then I moved to the optical end. Much like other aspects of my life, it turns out I’ve been exaggerating the size a bit. The tube is just shy of 80 inches long, and 16 inches diameter. The eyepiece mount is inch and a quarter, which means that all the eyepieces, hardware, and filters from my 5.1 inch will work fine. Which brings up the next question. The focus adjust on this one is too smooth/easy and there’s no way to lock it in place. If I were planning on shooting prime focus, is there a way to lock this, or would I need to order an eyepiece mount designed for locking/supporting an SLR?
(Not pictured) The tube also has guide/tracking rings and a 2.5-inch piggyback mount.
And then there was glass. Only 12.5 inches, not the massive 18-inch light sponge I thought I had.
It’s also 2 1/8 inches thick, and inscribed with “75.4,” which, best I can figure, is the weight in pounds.
I probably violated some cardinal rule, but using a soft rag and a bit of saliva, I cleaned a small part of the mirror surface to see how bad it was under all that gunk. It’s fricking silk.
So, is there any right way to go about cleaning the whole thing? Mild detergent and water? Windex? I’ll break out the google-fu, but I was curious if anyone else had a good method or advice?
I used two different methods of calculating out the focal length and got two different answers. Using the diameter-drop method, I get 39 inches and change, or roughly 1000mm at f/3.3 using half diffraction length, I get 78 inches, or roughly 2000mm at f/6.6. I might have my second technique wrong, so if it’s supposed to be quarter diffraction length, then the number match up. Either way, I’m stoked. Either I’ve got a great ratio for deep-sky or I’ve got a good start for planetary stacking with a webcam.
I also found a manufacturer’s mark on the mount structure for the mirror.
Quick googlage led me to an obituary and a bunch of discussion forums with people asking things like “hey, this guy made awesome shit. Where is he now?”
Kenneth F. Novak, 63, Ladysmith, died Aug. 5, 2004, at home.
He was born on May 29, 1941, at Ladysmith, the son of Frank and Margaret Novak.
He lived in Chicago from 1960-1971, and graduated from DePaul University, Chicago, Ill.
He was not married. He came to Rusk County in 1971.
While in Chicago, Ken developed a keen interest in astronomy which led him to develop his own business as a manufacturer of telescope parts. He was proud of his yard and enjoyed planting trees and flowers. He was an avid photographer and loved the outdoors as his main focus.
He belonged to Our Lady of Sorrows Catholic Church.
Survivors include a brother Tom (Merrilee) of Waterville, Minn., a sister, Susan (Dick) Nerbun of Cumberland; a nephew, Andrew (Vanessa) Nerbun of Shorewood, Wis., and nieces, Cindy Nerbun of Houston, Texas, and Karen Nerbun of Rochester, Minn.
Funeral services will be at 1:30 p.m. on Friday, Aug. 13, at the Our Lady of Sorrows Catholic Church with Dick Brockbank officiating and burial will be in Riverside Cemetery. Visitation will be from 11 a.m. to 1:15 p.m. Friday at the Nash-Jackan Funeral Home.
So yeah. I think this weekend I’m going to try to dig out the 5.1 newt and just “get to know” the both of them over the next month or two.March 2, 2012 at 2:53 am #45078
Oh. And it has a square spider going to the secondary. So I won;t have to cheat to get the four-point stars so verbally craved by others.March 2, 2012 at 4:22 am #45079
Jesus. Just when I thought we had you beat 😉
You better follow up on this, that mount looks promising.
And damn, be careful with that primary!
/me drools, that’s some sweet aperture…March 2, 2012 at 4:42 am #45080
oh… diffraction spikes… love/hate here. They’re artifacts of the hardware, and I’m planning on curved vanes for my secondary mount. Yes, they’re pretty, to some of us, but they’re flaws in the imaging train… They’re a hallmark of the reflector/refractor war.March 2, 2012 at 5:37 am #45081
My guess (without looking it up) is it’s a f/6.3–but that’s just a hunch. Be careful with that mirror–it’s surface coated!! I’d recommend mild, non-corrosive detergent and a nice soak, followed by a gentle rinse of water, and a ‘dusting’ off using some completely non-abrasive, virgin cloth material, and very little pressure on the mirror. You do not have to be perfect here–at those f/stops, you aren’t going to see the little specks of dust in the final product.
I look forward to your project. I’d recommend finding a way to stablize that focus mechanism–fine tuning focus requires a delicate touch in adjustments and plenty of stability for holding that focus.March 2, 2012 at 5:50 am #45082
I might be wrong here but the 75.4 might be FL and not weight.
“Kenneth Novak & Co Generally regarded as one of, if not the, best makers of mirror cells, spiders, and other mechanical parts.”
The (aluminum?) frame under the primary is called the “cell”.
This (Novak’s cell) and marking the FL on the mirror to 0.1″ leads me to believe you
could have a nice setup indeed. I don’t think Novak made mirrors but whoever
built the scope did not scrimp on the cell so maybe the mirror is of high quality also.
Mirror cleaning. This is a first surface mirror, likely aluminum and maybe
some additional clear overcoats.
Try to get as much off without actually touching it, warm soap and water
soaking for several hours if needed, windex is ok also.
There’s a guy (I can look it up if you want it later) who recoated my 16″ f4.5 for less than $100, I think he’s in CA.
The mount looks like something from the ’60 to ’70 time frame. Meade made some
that were similar (http://nofearofthefuture.blogspot.com/2008/07/way-down-telescope-way-pt-3.html)
but some of your details don’t match (truss type on the legs, bearing housing style).
Large gems are pretty unusual and I could swear I’ve seen your mount somewhere
but can’t recall. This will bug me now.
Not the 18″ (man that would have been awesome, >$2000 just for the mirror) but still
a lot of aperture and a great flea market find.
I knew I’d seen it:
(good general reference: http://www.telescopebluebook.com/)
Cave made some good stuff, and the legs matchup with yours. You might want
to do some other comparisons and research.March 2, 2012 at 6:35 am #45083March 2, 2012 at 6:46 am #45084
Depending on the age of the mirror, the coat may be straight aluminum electroplate. Clean with a mild detergent and a minimum (preferably none) of physical abrasion. Don’t use any oxidizers, the film is thin and will suffer for it.
Plus side: if the coat is oxidized or otherwise damaged, it can be recoated, with aluminum plus high-transmission overcoats for less than the replacement cost of the mirror. If the mirror is hand-ground (which is likely given the plate on it) it may be of a higher quality than newer mass-produced mirrors. Sorry Meade/Celestron/Orion owners, Synta optics just don’t cut it. Hand-figured glass just can’t be beat in the parabolic primary arena, and this maker was proud enough to put his name on it… but still no guarantee until the light gets measured thru it.
Recoating can be done by most any company who does that, as the quality is dictated by the precision of the glass…just use a reputable coater.March 2, 2012 at 8:19 am #45085
Fluffy– 16″ ?!?
I have size envy…March 2, 2012 at 6:18 pm #45086
Fluffy– 16″ ?!?
I have size envy…
Eh, your envy is based on incomplete information. The 16″ is just a mirror
set at this point. My plan is to weld together an aluminum truss type OTA
with some of my own design elements. This of course means time, and
lately I have been all terrestrial with my interests. So like Orionid, I’m on
the sidelines watching all you guys play.
That C11 (correct?) of yours is a very nice scope.
It doesn’t help my motivation on the 16″ that I also have complete and
functional scopes that I normally use (C8 Ultima and ST120 GEM). Even those
don’t see as much use as they should. It does make my mouth water to see
ya’ll ramping up though.March 3, 2012 at 12:06 am #45087
Jesus. Just when I thought we had you beat 😉
You still do….. Skies. The sky here is half of what it was when I moved down in 96. That year, we had to do a project in science class that was demonstrative of sample size and sampling errors by using a paper towel tube at specified intervals to count stars and calculate the number of visible stars in the sky. We were still commuting back to PA on the weekends to take care of the house that hadn’t sold yet, so I got permission to do my count up there. Most everyone in my class got numbers between 800 and 2500. I got over 10,000 (it helped that I had plieades in one of my samples, but still).
Responses in general to the ?ther, rather than quoting everybody:
I think you’re right about the 75.4 being focal length. The numbers work. It also works with the length of the tube. That’s still like 1850 mm at f/6. Sweet Jeebus.
The mount is labeled “Astrola.” So, yeah. Cave. I’ll stick with it for a while, but IF it ever becomes the limiting factor, I’ll sell a kidney for a losmandy. But that won’t be until after I’m fully qualified at work and start making stupid money. Maybe I’ll rent one at some point just to spoil myself with “goto.”
Likewise with recoating. I haven’t cleaned the full thing yet. I’m using it as motivation to get my cars sold so that I can put real effort into it. But what I’ve seen so far looks good, so I’ll run it as is until my skills catch up and I feel limited. Then I’ll get a fancy whamodyne modern job.June 19, 2012 at 11:31 pm #45088
Okay, here’s an update.
Mirrors are clean, everything is reassembled (ish), some hardware has been modernized (alan screw replace with thumscrew on focuser lock, etc). I still need to work out some hardware things, yet. Some of the 1/4-20 nuts are going to be replaced by wingnuts, some of the heavy-duty hardware needs replaced (missing), and there’s still one piece that I have no idea what the fark it does (photos soon). It looks like a motorized piggyback rig for a smaller scope, and has a 6-pin moly connector on it that doesn’t fit up with anything else.
I haven’t pointed it at dark skies, yet, as time and Appalachian haze have conspired against me, but I did some play-testing in the driveway. With my 24.5mm eyepiece (cheap plossl), it resolves detail in individual leaves on a tree 400 yards away, probably a FoV about 10 feet across. With my 8.7mm eyepiece (even cheaper plossl), it won’t get sharp. It “focuses,” but there’s no real detail. I think 1860mm/8.7mm is just too much magnification, maybe, for the cheapo eyepiece?
And now for the questions that prove I’m still just a n00b figuring out a cool toy:
My T-mount adapter is the cheap celestron universal 1.25″ ( http://www.adorama.com/CNTA1Q.html ). The thick part at the top of the barrel prevents it from focusing inward enough to prime focus my slr. I don’t want to buy a new focuser yet (until I’m ready to drop a healthy dollar on a 2″ motor-stepped job, which woont be until AFTER I figure out what the hell I’m doing and my “fun money” account grows several times over). I can’t seem to find a T adapter for 1.25″ that will let you sink it all the way in to the threads. Anybody know where I might find one?
Also, I’m familiar with digiscoping, but what’s eyepiece projection? I’m guessing using the eyepiece as a rear element to project the image of the scope onto the sensor? How much light is lost doing that over prime focus? How much better quality is it than digiscoping?June 19, 2012 at 11:53 pm #45089
Have a lookie:
Let me know if these do not work and I’ll dig through my bookmarks some more.June 20, 2012 at 2:00 am #45090
I got my current adapter from some random on-line shop at amazon. I have to say–it’s a lot better than what you get from Celestron. I have a Canon, but I bought a Nikon mount so others could enjoy; search for “Opteka T-Mount Adapter”; it’s like 20$ or so.
You won’t get a closer mount for a D/SLR, and it’s far better in regards to proper culmination (the screwing ‘feature’ on the Celestron rig is a joke). You should lose 1/2″ to 1″ of focal length, which should get you plenty of wiggle-room to get a clearer shot. If you’re using a right-angle viewer; remove it.June 20, 2012 at 7:15 am #45091
Thanks Fluffy and Rav.
Next payday, when my fun account recharges a bit, I may grab the owl kit with both the prime and projection hardware and the low-profile ring.
Also, tonight’s been incredibly slow, with a heat advisory for the area, and peak demand on the grid, we’re pretty much not allowed to do anything except emergent work. They even have engineers doing real-time flux calculations to squeeze every last watt out of the reactors right now. So I’ve been alternating back and forth between online training and google-fu. I found wome interesting stuff.
The glass is likely also Cave and seems to be highly regarded. I’ve seen several comparisons of a recoated Cave 12.5 out-shining a $4000 modern 20″ SCT. The hardware I have is pretty much Cave’s cadillac with all the options.
It’s got full electric controls for RA/Dec adjusts, but is missing the controller itself. Given the level of technology, I could probably fashion a new control with $15 in parts from Radio Shack or Mouser. The ugly thing I earlier thought was a crazy piggyback rig is actually an optional electric drift adjust. However, the strange “extra” brackets on the top/side of the tube clamps are for piggybacking an 8″ reflector (some of that hardware is missing, but I could probably fix/repair easily enough). The other two piggybacks mounted on the tube itself are for various power finder scopes.
On the down sides, I’m missing the counterweights, and there’s a lot of mentioning of the mount not being stable enough for AP. Apperently even with the behemoth of a mount that it is, the sheer size of the scope makes any breeze a big deal.
Now I wish I wasn’t working nights this week so I could actually play around a bit more. I think I’m going to have to use my incentive days at some point come early autumn to spend several consecutive nights “getting to know” it.
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