Jump to content


Photo

Mega-mod thread for Zhumell dobs

  • Please log in to reply
530 replies to this topic

#451 petrus45

petrus45

    Mariner 2

  • *****
  • Posts: 239
  • Joined: 31 Jan 2011
  • Loc: SW Ohio / N Ky.

Posted 27 January 2014 - 09:35 AM

Here is a new topic I believe:
The focuser on my Z12 does not mate flush with the OTA. The focuser base is curved for a smaller tube probably because they are more popular. There is a gap where light, dust, spiders, whatever can get inside.

To make matters worse, I needed to shim the focuser to square it to the OTA to get it properly collimated.

Now I have an even bigger gap and I'm wondering how to seal it. :shrug:

I suspect a caulking gun is not the way to go......any ideas out there?
Thanks, Dave Y


I'm all for cheaper solutions, but you might consider just unscrewing the hex nuts in the base, and replacing it with a 12" base, which you might be able to get from Agena or somewhere else - but you'd have to make sure the new base will fit your focuser. For something giving you that much trouble, seems like it would be worth it.

#452 csrlice12

csrlice12

    Voyager 1

  • *****
  • Posts: 11229
  • Joined: 22 May 2012
  • Loc: Denver, CO

Posted 27 January 2014 - 09:53 AM

Agree with Petrus, this is a hobby where mm count, and jerry-rigging a focuser is probably not the best idea. How will it perform with a paracorr and a heavy eyepiece? Will it "flex" in the opening? Best to get the proper mounting plate or replace the entire focuser.

#453 Sarkikos

Sarkikos

    Hubble

  • *****
  • Posts: 17139
  • Joined: 18 Dec 2007
  • Loc: Per sylvam ad astra

Posted 27 January 2014 - 10:17 AM

Good points.

Mike

#454 Tristan

Tristan

    Ranger 4

  • -----
  • Posts: 312
  • Joined: 07 Jun 2011
  • Loc: NC

Posted 27 January 2014 - 12:03 PM

I used black adhesive foam window/door insulation for mine from Home Depot. Comes in 1/4" wide strips, peel the backing off, stick it to the focuser and screw it back on the tube. The foam compresses and does not appear to interfere with the mounting of the focuser and is good and rigid.

#455 sslcm56

sslcm56

    Vostok 1

  • -----
  • Posts: 191
  • Joined: 20 Jul 2012
  • Loc: Montgomery, Al.

Posted 27 January 2014 - 12:33 PM

After reading 2 very long threads on thermal management I defocused on a brite star and could see the thermals boiling of the primary. Jupiter was very mushy. I have had some great views of it in this scope so I decided on some thermal management.

I got some black foam core and cut it to the size of the ID of the very back hole in the cell. This way I didn't have to make a lot of cut outs for the collimation and locking screws.

I cut a hole for the fan which I always thought was an exhaust fan but was actually blowing. It was so close to the primary that I couldn't tell. It went from a low rumble to sounding like hurricane Opal when it came through here. I can now remove the plug from the focuser and feel the air 1.5 feet back.

If it works out well I will get some silicone sealer and make it more permanent and seal up all the little leaks. I will post pictures if I keep it this way.

It MUST be a good thing I did because it went from clear to a forecast of 2" of snow tomorrow.

#456 kfiscus

kfiscus

    Vanguard

  • *****
  • Posts: 2241
  • Joined: 09 Jul 2012
  • Loc: Albert Lea, MN, USA

Posted 27 January 2014 - 12:38 PM

"Jerry-rigging" (jury-rigging?) seems a bit strong. It didn't sound like the OP's focuser is flopping around or anything. Just filling the side gaps to keep light, dust, and critters out should be a cheap & easy fix- not requiring an expensive new focuser base.

#457 petrus45

petrus45

    Mariner 2

  • *****
  • Posts: 239
  • Joined: 31 Jan 2011
  • Loc: SW Ohio / N Ky.

Posted 27 January 2014 - 02:09 PM

Considering the cost of purchasing foam, adhesive, or other supplies needed, I'd be sure to comparison price a replacement 12" base. I found something similar to what you might need at
Crayford Base Plate and it's only $13. I would call and ask to make sure it's the right thing, but really how can you go wrong at $13?

#458 kfiscus

kfiscus

    Vanguard

  • *****
  • Posts: 2241
  • Joined: 09 Jul 2012
  • Loc: Albert Lea, MN, USA

Posted 27 January 2014 - 02:31 PM

$13 is a VERY affordable option.

#459 Cames

Cames

    Ranger 4

  • -----
  • Posts: 341
  • Joined: 04 Aug 2008

Posted 27 January 2014 - 02:44 PM

You're welcome, Petrus45

but really how can you go wrong at $13?


If you have eyepieces, like orthoscopics, that come into focus with the focuser tube almost all the way in, or if you plan on using a coma corrector with eyepieces that come into focus with the focuser tube almost all the way in, you have to be careful not to elevate your focuser away from the secondary mirror. Be sure that you know how much, if any, the base plate will elevate your focuser.

You don't want your new base plate to prevent your eyepieces from reaching focus.
-----
C

#460 csrlice12

csrlice12

    Voyager 1

  • *****
  • Posts: 11229
  • Joined: 22 May 2012
  • Loc: Denver, CO

Posted 27 January 2014 - 02:51 PM

....there's also the danger of over-tightening the current one, or someone grabbing the eyepiece to "slew" the scope, which could possibly dent the OTA where the focuser fits as the pressure points may exist. This could really mess up your scope. I'd spring for the correct mounting base.

#461 rowdy388

rowdy388

    Mariner 2

  • -----
  • Posts: 285
  • Joined: 09 Apr 2013
  • Loc: Saratoga County, NY

Posted 27 January 2014 - 08:05 PM

Hey, lots of great ideas here. Not sure which option I'll take but I'll let everyone know how my solution worked.
The focuser is very secure as is.....I used that monster 3+ pound Meade 30 UWA with a Paracorr to view M81 and M82 with supernova. Froze my butt off but worth it.
No issues with stability but now I'm asking myself if I'm pushing my luck!

I may still get the new base for a custom fit but I love that idea of using a window weatherstrip with sticky peeloff.

Thanks for all your great suggestions guys.
Dave Y

#462 Tristan

Tristan

    Ranger 4

  • -----
  • Posts: 312
  • Joined: 07 Jun 2011
  • Loc: NC

Posted 27 January 2014 - 08:26 PM

The replacement does not match the outside diameter of the tube. checking the Agena Astro web site it lists the curve diameter of the plate made for GSO 12" scopes as 11.93" The actual diameter of the tube is a bit beyond 14". I believe this is the problem those of us who own some of these newer models have run into. Not even the factory replacement fits correctly.

#463 rowdy388

rowdy388

    Mariner 2

  • -----
  • Posts: 285
  • Joined: 09 Apr 2013
  • Loc: Saratoga County, NY

Posted 27 January 2014 - 08:39 PM

Tristan,
I just saw that as well. Looks like your idea of a window sealing foam or Kens idea of Joanne felt fabric is the way I'm going to go. Thanks, Dave Y

#464 Pinbout

Pinbout

    Cosmos

  • *****
  • Posts: 8022
  • Joined: 22 Feb 2010
  • Loc: nj

Posted 27 January 2014 - 09:20 PM

The focuser on my Z12 does not mate flush with the OTA. The focuser base is curved for a smaller tube probably because they are more popular. There is a gap where light, dust, spiders, whatever can get inside.



really? your concerned about that? Oh Lawd! [lord with a southern accent]

don't ever use the older jmi focusers on a home build if that bothers you. let alone a kineoptic helical focuser. that has some many open cracks you'd think it was an addict. :foreheadslap:

never gave it any mind.

worried about spiders? at least you probably never had a frog in you scope.

:grin:

#465 kfiscus

kfiscus

    Vanguard

  • *****
  • Posts: 2241
  • Joined: 09 Jul 2012
  • Loc: Albert Lea, MN, USA

Posted 27 January 2014 - 09:57 PM

A frog?!? Do tell.

#466 rowdy388

rowdy388

    Mariner 2

  • -----
  • Posts: 285
  • Joined: 09 Apr 2013
  • Loc: Saratoga County, NY

Posted 27 January 2014 - 11:36 PM

Do you have one of those open truss mods where a cat can jump through it? :lol:
I'd like to hear your frog story as well...made me laugh!
Dave Y

#467 petrus45

petrus45

    Mariner 2

  • *****
  • Posts: 239
  • Joined: 31 Jan 2011
  • Loc: SW Ohio / N Ky.

Posted 28 January 2014 - 12:21 PM

The replacement does not match the outside diameter of the tube. checking the Agena Astro web site it lists the curve diameter of the plate made for GSO 12" scopes as 11.93" The actual diameter of the tube is a bit beyond 14". I believe this is the problem those of us who own some of these newer models have run into. Not even the factory replacement fits correctly.


Seems a shame the newer models would not be standard sized....

#468 David Castillo

David Castillo

    Surveyor 1

  • *****
  • Posts: 1883
  • Joined: 09 Sep 2006
  • Loc: Carmel Valley, Ca

Posted 29 January 2014 - 12:05 PM

Why fret over a tiny gap under the focuser? My veiwing is at night and there isn't much light after the sun goes down to illuminate the focuser. Besides, the drawtube of the focuser isn't transparent, so stray light is baffled by the tube.
------
Dave

#469 kfiscus

kfiscus

    Vanguard

  • *****
  • Posts: 2241
  • Joined: 09 Jul 2012
  • Loc: Albert Lea, MN, USA

Posted 24 February 2014 - 01:01 AM

Just to keep spiders out. I keep my scope in my unheated garage, sealed tight top and bottom to keep dust and critters out. Bottom cover is removed for mirror cooling and use.

Oh, yeah, this is a bump of my favorite thread, too.

#470 kfiscus

kfiscus

    Vanguard

  • *****
  • Posts: 2241
  • Joined: 09 Jul 2012
  • Loc: Albert Lea, MN, USA

Posted 31 March 2014 - 09:43 PM

Bump. Several new threads about Zhumells.

#471 Dennis_S253

Dennis_S253

    Surveyor 1

  • -----
  • Posts: 1729
  • Joined: 22 Nov 2011
  • Loc: West Central Florida

Posted 01 April 2014 - 08:47 PM

Wow I only got up to page 17 and this is great. More to learn. It's bed time though.

#472 Elroy

Elroy

    Lift Off

  • -----
  • Posts: 19
  • Joined: 22 Nov 2013

Posted 04 April 2014 - 09:00 PM

Addictive isn't it? I was leaning toward an 10", but after reading this I just couldn't help myself. And now after viewing M42 for the 1st time, I'm ready for my next step, Bob's knobs,new primary springs and more EPs and filters. :tomatodance:

#473 kfiscus

kfiscus

    Vanguard

  • *****
  • Posts: 2241
  • Joined: 09 Jul 2012
  • Loc: Albert Lea, MN, USA

Posted 19 April 2014 - 11:25 PM

Bump of the best thread.

#474 320mb

320mb

    Sputnik

  • -----
  • Posts: 31
  • Joined: 20 Jun 2013
  • Loc: Southern Arizona

Posted 24 April 2014 - 04:00 PM

Hi All, I'm about to join the "mod squad"..... Flockboard from Protostar has arrived, new secondary knobs and primary springs, and I ordered a template and small triangle from Catseye. I have to say the Flockboard material is dark, dark, dark. WOW :refractor: Will be back to comment on the image contrast when I have my Z10 put back together.

#475 kfiscus

kfiscus

    Vanguard

  • *****
  • Posts: 2241
  • Joined: 09 Jul 2012
  • Loc: Albert Lea, MN, USA

Posted 24 April 2014 - 09:57 PM

It's customary to ask for/demand pix after posts like yours- it happened to me when I did my flocking. Such a photo would be nearly impossible- the stuff is about as shiny as a black hole. Good luck with your installation.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics