I want a big telescope...

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I want a big telescope...

Postby Jerry » Fri May 06, 2011 6:32 pm

I got a real nice CCD camera from work the other day. This guy:

http://www.princetoninstruments.com/Uploads/Princeton/Documents/Datasheets/Princeton_Instruments_MEGAPLUS_EC11000_A1_1.pdf

We used these to film the movie Coraline. Didnt work so hot, software issues. And real expensive, somewhere between $15,000 and $20k per set. Not the perfect astronomical camera, but should be better than a dSLR. Now we use off the shelf software and sSLR's.

So, I want to build a telescope to use this guy with. I dont want to go all out like Evan has so I figure on something simpler. I may do a similar cell design though.

This is what I am thinking of using for a tube:

Image

Its a tube made from Garolite G-10 from a Nuclear Magnetic Resonance magnet. It has a 12.5" bore and right at 48" long and somewhere around 1/16-3/32 thick. The aluminum rings are epoxied. This puts it on the edge for the 8" and 10" kits on Coulter's Optics site (http://www.e-scopes.cc/). They have a F number of 6 and 5 respectively so the length of the scope will be pretty close whichever I choose. Its hard to be the prices there. $299 for a 8" parts kit.

I was also thinking of getting a piece of AR coated glass to use for a secondary support. This would eliminate the artifacts from the spider with a slight loss in light, but since it will be a mostly an imaging telescope I can get away with longer exposure times to compensate.

I think I will do a Alt/Az drive. I have a nice harmonic gear box with a DC servo that I can drive for azimuth, not sure for alt yet.

What software is out there for telescope control? I am hoping something I can just set up and do step/dir control.
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Re: I want a big telescope...

Postby johnf » Fri May 06, 2011 6:57 pm

Jerry
If you get your skates on you might get a pic of that asteroid thats due to come between moon and earth in November
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Re: I want a big telescope...

Postby Doug Coulter » Fri May 06, 2011 7:54 pm

I have a Meade 10" with computer controls and cameras and lenses and software available cheap to a good home. If that does you any good. I find it pretty amazing around here (good seeing), and you can virtually fly over the moon or jupe like a tie fighter with the controls -- at low altitude and fast (or stopped - and it has corrections for things that don't move like the stars re us). Moderately amazing. Add a really good camera (I have one real decent b/w and filters) and you can get some very sweet pix.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: I want a big telescope...

Postby Jerry » Sun May 15, 2011 12:06 am

I got my telescope to camera adaptors in the other day and had to try them out. This is with my little Astroscan. Picked it up from goodwill a few years ago. I am using a celestron barlow adapter on my Canon 60D.

Image
Astroscan hazy moon by macona, on Flickr

As you can see the photo is quite hazy from the light clouds. The weather has been terrible here. I think we have just about set the record for the wetted spring. The current forecast might give me a clear day next sunday. I have never ran my heater this late in the year as this one.
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Re: I want a big telescope...

Postby Jerry » Sun Jun 12, 2011 11:26 pm

I got the telescope from Doug last monday. Had to pick it up from the fedex location. The box is massive, almost takes up my entire back seat of my little Dodge Neon.

Did a couple little repairs. Meade used 25v tantalum electrolytics on the high side of the voltage regulators. Problem is the power pack is 18v unregulated. This tends to make them pop. So I replaced all the critical ones. The one on the main board had exploded, and the one in the hand control had cracked and two little blobs of solder were peaking out. Luckily I have a bag of tantalums.

Cleaned it all up, made an base to mount it to my big ole Bogen/Manfrotto tripod and waited... Finally last night I had a patch of clear sky. Took these shots. Not bad, not great. It was still pretty bright. One of the next things I need to get is a rear mounted focuser. It will allow me to fine focus without shifting the promary mirror and also removes the light bottle neck at the reducer on the visual back of the scope. The one I am looking at also has a carrier for the mead f6.3 field reducer.

http://www.focuser.com/cgi-bin/dman.cgi ... product=CS

I also got my new ccd camera from ebay. Its a Roper Scientific/Photometrics Quantix camera. Uses a Kodak KAF-6303E monochrome sensor. TEC cooled, it is rated to reach -35c with a water loop and -25c fan cooled, though it has no problems getting to -30c fan cooled. This thing is stupid sensitive. When I got it I thought something was wrong with it. Even at .001 sec exposure times it was totally overexposed in normal room light. Even putting my hand over the lens the camera was still showing light. Eventually after advise from the seller I put black tape between the back of the lens and the sensor and poked a tiny hole in the tape. Finally I could get an image, although that was overexposed too. The cameras also do not have mechanical shutters. Seems they were a custom version.

http://www.cloudynights.com/ubbthreads/ ... ll/fpart/1

A bunch of us over in the cloudynights.com forum bought these cameras. A couple have already gotten some preliminary shots. So the next thing is to add a shutter, and then filter wheels. Also the only interface between the camera and the computer is though a 68 pin cable to a PCI card. Not the most portable option. I have managed to get the card working on a 1GHz via C7 motherboard running XP. I can get a little case with a 12v input power supply to run it for about $100.

Image
IMG_0499 by macona, on Flickr

Image
IMG_0504_DxO by macona, on Flickr

Image
IMG_0512 by macona, on Flickr

Image
IMG_0515 by macona, on Flickr
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Re: I want a big telescope...

Postby Doug Coulter » Mon Jun 13, 2011 10:25 am

Jerry -- glad it made it there OK. The mirror was badly out of collimation when I put it in the box, and wouldn't have gotten better being shaken up - you'll need to set that up according to any of the ways in the books to get real good pix - the moon should be razor sharp even at far higher magnification than that, almost like being there in a plane flying at low level. I used the laser pointer method. It makes a huge difference in the quality to have all the contributions from the various parts of the main mirror in focus at the same time. You should be able to use the flip box and filters I sent for pix (those are some nice filters), and once set up, you can put an eyepiece in one of the flip box ports and check focus that way -- takes a little tweaking to get it so the eyepiece focus is par-focal with the camera, but it's worth it (I made a clamp for the camera to set the seating depth for that so it was easy to get it right every time in the dark).

From what I see in that picture, you can expect at least 20x or more better once you get the optics pointed at each other straight...you'll see the rings in Saturn a whole lot better too, at least when the seeing is good - I was able to see the bands easy when things were right. A long exposure on fluttery seeing can mess that up, which is why I was fooling with the video camera -- I could then break the video up into frames and then only sum up the non-smeared ones for much better results (and with vids taken with all three filters, recombine for color too). If I find that software I used I'll send it along. There's probably better stuff out there now, but it did the job if you did the work.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: I want a big telescope...

Postby Jerry » Mon Jun 13, 2011 7:50 pm

I had an opening of about 2 hours to get to play with it before the clouds came in and I dont think the scope ever really cooled down to ambient. Looks like I might get some clearing tomorrow night and then I can tweak it. I might also try to make an artificial star to collimate at any time.
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Re: I want a big telescope...

Postby Doug Coulter » Tue Jun 14, 2011 9:31 am

I forget what they tell you to do there, but I recall a piece of cardboard and a laser pointer. I found the slick trick outside the Meade book, someplace on the 'net -- there are a couple of ways and you can use one to check the other. At any rate, it's going to be a real pleasant surprise how much better it gets if you really get that right -- be real picky and take time on the adjustment. I didn't notice real huge errors from not being at ambient, other than if the scope is hot and the night cold, then you see "mirage" ripples from the convection currents off it. They seem to have used the right tempco stuff such that the scope stays in alignment OK over temperature. But banging it around will mess it up. I used to get it set up in the afternoon, (all that gps stuff and leveling and so on) and toss a tarp over it till it was out of the direct sun, take it off, then when it gets really dark, go for it. Never had a temp drift problem doing that. You might have more issues with dew than I had because of where you are -- I mostly had that when bringing it back indoors cold.

But yeah, getting the mirrors pointed right at one another is a really big deal, and your contrast will go way up along with better focus when you do. It will show you how much better the human eye is than *any* existing camera too. They're getting good, but once you're at the point of enough light for the eye to see things, the eye has so much more dyn range than a camera it's not funny.

You don't have a vignetting problem unless you are using a longer FL objective for wide field even with the normal eyepiece adapter (for that you want a 2" diameter 40mm eyepiece, which I never managed to acquire). If you can fit your camera to the flip box, it makes an OK shutter for manual type shutter speeds -- just flip the mirror to and fro.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: I want a big telescope...

Postby Jerry » Tue Jun 14, 2011 3:39 pm

I took it out last night and did some adjusting between the clouds. Saturn and the moon look better. But seeing was not great.

I am probably going to get this focuser made by moonlight.

http://www.focuser.com/cgi-bin/dman.cgi ... category=5

It attaches directly to the 3-1/4" threads on the back of the telescope and eliminates a lot of light bottleneck at the adapter that would be even present with most 2" optics. It also will hold the f6.3 or f3.3 field reducers while minimizing the extension of the light path.
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