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Equipment Discussions >> Classic Telescopes

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Ducky62
professor emeritus


Reged: 10/31/10

Loc: The ATL
Re: Vixen 3720 36.4mm to 1.25" diagonal new [Re: strdst]
      #5672948 - 02/10/13 07:47 PM

8 pages of instructions for a Barlow? What could it possibly say? You ought to scan and send the file to Robert Provin.

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strdst
Post Laureate
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Reged: 03/23/08

Loc: Oregon Territory
Re: 36.4mm to 1.25" diagonal to 6" Dynascope new [Re: Ducky62]
      #5673153 - 02/10/13 09:59 PM

Quote:

8 pages of instructions for a Barlow? What could it possibly say?




Oh pretty much everything!


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strdst
Post Laureate
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Reged: 03/23/08

Loc: Oregon Territory
Re: 36.4mm to 1.25" diagonal to 6" Dynascope new [Re: strdst]
      #5673206 - 02/10/13 10:30 PM Attachment (14 downloads)

I took ol' Dyna up to the lake today for an outing. Had the weather been better a picnic would have been nice... Here are a few more pictures...Being a refractor kinda guy I'm still puzzled where Dyna's good side might be. lol.

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strdst
Post Laureate
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Reged: 03/23/08

Loc: Oregon Territory
Re: 36.4mm to 1.25" diagonal to 6" Dynascope new [Re: strdst]
      #5673227 - 02/10/13 10:43 PM Attachment (9 downloads)

OK, lake is a stretch this time of year. A flood control dam thoroughly drawn down ready for the next wet weather event. Next June through September it will be full of water and boats again. First and only time I observed Mercury was from up here on the dam face. And the Leonid shower in 2000 or 2001 was absolutely crazy up here with a horizon to horizon view.

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strdst
Post Laureate
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Reged: 03/23/08

Loc: Oregon Territory
Re: 36.4mm to 1.25" diagonal to 6" Dynascope new [Re: strdst]
      #5673230 - 02/10/13 10:45 PM Attachment (12 downloads)

Some detail...

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strdst
Post Laureate
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Reged: 03/23/08

Loc: Oregon Territory
Re: 36.4mm to 1.25" diagonal to 6" Dynascope new [Re: strdst]
      #5673236 - 02/10/13 10:47 PM Attachment (8 downloads)

and smaller detail...

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strdst
Post Laureate
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Reged: 03/23/08

Loc: Oregon Territory
Re: 36.4mm to 1.25" diagonal to 6" Dynascope new [Re: strdst]
      #5673254 - 02/10/13 10:57 PM Attachment (12 downloads)

And a question. I had the owner/seller hold my Maglite to the mirror end as I looked for light coming through the coating. He mentioned that there was a part attached that if removed would allow for better air circulation in the OTA. So much for the mirror test. My question is this... can I undo this piece without messing up the mirror collimation? I'm pretty intimidated by the collimation process.

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actionhac
Post Laureate
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Reged: 08/09/08

Loc: Seattle
Re: 36.4mm to 1.25" diagonal to 6" Dynascope new [Re: strdst]
      #5673461 - 02/11/13 03:46 AM Attachment (9 downloads)

That's very nice Keith. That is pure 1950's.
I wonder if the previous owner meant removing the chrome cap in the center for better air circulation.
I'm still experimenting with newt thermal management. Sometimes I can't decide if I should allow air to move through the tube or not, or just seal it off behind the primary. You can try it both ways. I'd say generally its better to let air move through the tube, sometimes forcing it with a fan. Especially to cool the tube and mirror to ambient.
Here's some info. Scroll down the page for collimation, collimation tools and tube currents, thermal management:
http://www.garyseronik.com/?q=taxonomy/term/3
Some more:
http://www.fpi-protostar.com/bgreer/index.htm

This is a cell similar to the Criterion. I don't know why Criterion went to all the trouble to blank off the free area with that black wrinkle plate. And the chrome plug must be for allowing some air movement, but why so little.
Obviously Criterion had different thoughts on airflow with the Dynascope and I wonder if a owners manual might shed some light.

Edited by actionhac (02/11/13 11:02 AM)


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Grava T
Pooh-Bah
*****

Reged: 06/18/08

Loc: Quebec, Canada
Re: 36.4mm to 1.25" diagonal to 6" Dynascope new [Re: actionhac]
      #5673557 - 02/11/13 07:13 AM

Beautiful newt Keith. For a refractor guy, as least you got the eyepiece in the right position. Nice observing spot!

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actionhac
Post Laureate
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Reged: 08/09/08

Loc: Seattle
Re: 36.4mm to 1.25" diagonal to 6" Dynascope new [Re: Grava T]
      #5673970 - 02/11/13 12:29 PM

Here is a 1958 sales brochure from Robert's site:
http://geogdata.csun.edu/~voltaire/classics/criterion/dyna1960.pdf
In the brochure it states:
"Mirror is housed in a ventilated cell".
And this statement:
Ventilation has been carefully computed to allow least thermal interference".

A description of the picture Rear of the Dynascope calls the chrome plug a "ventilation plug".
An owners manual may explain when and why you would "pull the plug" and also if you can remove the black wrinkle painted plate for a open tube end.

Robert


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strdst
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Reged: 03/23/08

Loc: Oregon Territory
Re: 36.4mm to 1.25" diagonal to 6" Dynascope new [Re: Grava T]
      #5674801 - 02/11/13 09:05 PM

Quote:

Beautiful newt Keith. For a refractor guy, as least you got the eyepiece in the right position. Nice observing spot!




Thanks Michael. It's the "fully rotating tube assembly". Makes keeping the eyepiece well placed, a snap.


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strdst
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Reged: 03/23/08

Loc: Oregon Territory
Re: 36.4mm to 1.25" diagonal to 6" Dynascope new [Re: actionhac]
      #5674823 - 02/11/13 09:18 PM

Robert, thanks.

So just the chrome round you think. I was anticipating removing everything down to the aluminum cell like other scopes look. The plug makes more sense, maybe not in a faster thermal equilibrium way but it looks nice.

You didn't mention Trixie in the Barlow photo. I found her in the park. Might be one of Glowy's old buds


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actionhac
Post Laureate
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Reged: 08/09/08

Loc: Seattle
Re: 36.4mm to 1.25" diagonal to 6" Dynascope [Re: strdst]
      #5675130 - 02/12/13 01:25 AM Attachment (9 downloads)

I think you may have a good idea Keith removing the whole plate with plug so its like the RV-6.
Still I wonder why Criterion went to all that trouble to fill in the back of the cell and only having a small port with a removable plug. They obviously were on to something we are not familiar with.
I would start by trying out the removable plug. With it removed and in place under various conditions. In focus and defocused stars should help tell you if the mirror is not equalized or if tube currents are the problem or atmospheric seeing is spoiling the view, if you do have any problems.
Its tough trying to figure out which of all the possibles is causing the problem. Once you know where the problem is coming from and can correct it then the newt is fabulous. I have a long ways to go although I'm better then I was.

I did see Trixie she's darling. Does she have the powers to glow, looks like she might. Here Glowy's being silly again as usual:


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tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: 36.4mm to 1.25" diagonal to 6" Dynascope [Re: actionhac]
      #5675548 - 02/12/13 10:29 AM Attachment (7 downloads)

Me? I've got Rodney to certify my scopes:

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rguasto
scholastic sledgehammer
*****

Reged: 11/18/10

Loc: Long Island, NY
Re: 36.4mm to 1.25" diagonal to 6" Dynascope [Re: strdst]
      #5675570 - 02/12/13 10:44 AM

I added a fan to the rear of my 8" dynascope. Works extremely well and stays on all the time with no vibration detectable during observing. It's and 80mm USB fan with an 80mm to 60mm (reducer) blowing onto rear primary.
Pictures are in classic scope photo gallery. Also posted in yahoo group under "8" deluxe dob"

http://www.cloudynights.com/photopost/data/508/159290resize1-thumb.JPG

http://www.cloudynights.com/photopost/showphoto.php?photo=23091&password=...


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strdst
Post Laureate
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Reged: 03/23/08

Loc: Oregon Territory
Re: 36.4mm to 1.25" diagonal to 6" Dynascope [Re: rguasto]
      #5688207 - 02/19/13 02:04 AM Attachment (4 downloads)

I actually got two good observing nights last week. One ended in dew/ice accumulating pretty quickly. The other in fog off the river in the backyard. But the air was still and I had some nice targets long enough to appreciate...

The Vixen adapter to use my new "old" Edmund 1.25" diagonal is fantastic! And the Dynascope even being out of collimation was very impressive. I know the previous/only owner never touched the adjustments. He was quite proud of that

I just want to get a bit of advice before anything goes south. The three secondary mirror collimating screws are reluctant to turn. They seem to be brass (soft) and I don't want to bugger them up right off. I'm wondering if removing the spider (?) (what is this style secondary holder called?) from the tube is wise while loosening things up. And what do you loosen first and second and third. Here are a few pics. This guy is pretty cool!


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strdst
Post Laureate
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Reged: 03/23/08

Loc: Oregon Territory
Re: 36.4mm to 1.25" diagonal to 6" Dynascope [Re: strdst]
      #5688210 - 02/19/13 02:08 AM Attachment (4 downloads)

I don't have a laser collimator, but a neighbor gave me this to use...

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strdst
Post Laureate
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Reged: 03/23/08

Loc: Oregon Territory
Re: 36.4mm to 1.25" diagonal to 6" Dynascope [Re: strdst]
      #5688213 - 02/19/13 02:10 AM Attachment (5 downloads)

And this is what I see looking through that tiny hole...

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actionhac
Post Laureate
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Reged: 08/09/08

Loc: Seattle
Re: 36.4mm to 1.25" diagonal to 6" Dynascope [Re: strdst]
      #5688683 - 02/19/13 11:17 AM

Keith if what your camera is seeing through the hole is the same as what your eye is seeing try just grabbing hold of the spider and give it a slight turn to centralize things.
I don't remember the Criterion holder but the 3 brass screws are all pushing against the diagonal holder if I remember correctly so if you loosen one a hair all 3 should loosen slightly but this will change collimation. It may also be possible to slacken off the center stud to relieve pressure on the 3 screws. I wish I had one in front of me, I can't remember how it works.
Try moving the spider first before touching the 3 screws.
The spider is attached to the tube with one screw, rotate the spider on that pivotal screw and see if the primary is centered in the diagonal when looking through the small hole in the cap.
You don't need a laser. The cap with a hole is fine at f8 focal ratio. I think the Dynascope may be f8.5.
As a final touch up defocus a star like Polaris and see if the rings are concentric.
Polaris is good because it doesn't move.
Don't defocus too far, just 3 or 4 rings and work through from low to high powers.
I use one of these:
http://www.scopestuff.com/ss_coll2.htm

Robert


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strdst
Post Laureate
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Reged: 03/23/08

Loc: Oregon Territory
Re: 36.4mm to 1.25" diagonal to 6" Dynascope [Re: actionhac]
      #5690126 - 02/20/13 02:17 AM

Thanks Robert,

I got home late tonight. Cloudy and cold. I'll start with the Twist as you recommend. Nearly same vintage after all If the twist doesn't collimate the secondary, maybe the Jerk will. I hope I don't need to
escalate to the Funky Chicken....Not a pretty sight


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