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Equipment Discussions >> Reflectors

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Scanning4Comets
Markus
*****

Reged: 12/26/04

Loc: Ontario, Canada
Re: Mega-mod thread for Zhumell dobs new [Re: poodle]
      #4441745 - 03/11/11 06:57 AM Attachment (154 downloads)

Nice mods !!!

I know Mike has wanted to see this pic I have added for a while. It is an apodizing screen to boost the contrast on the planets I put on my 12" reflector in 2005...and yes , it really does work !!!....I no longer have the 12" tho.


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Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Mega-mod thread for Zhumell dobs new [Re: Scanning4Comets]
      #4441801 - 03/11/11 08:17 AM

Markus,

Thanks for posting that pic. Looks good. Where did you get the ratios to construct the screens? Did you give the apodizing mask to the buyer?

I'm working on an apodizing mask for my Z8 now. This time I went to the trouble of going to Harold Suiter's website, downloading his spreadsheet, and using that to calculate the aperture percentages for the three screens. For my 10", I just copied the ratios from another observer who had virtually the same telescope, so I also got the same level of good results that he did.

For the Z8 mask, I cut the two retaining rings out of black foam core. The rim is the diameter of the OTA, the inner edge is the diameter of the primary mirror minus the bevel. The mask will rest on the rim of the OTA, and will be snugly held in place by the dew/light shield. That way, I won't have to push the mask down inside the OTA.

I cut ring templates out of white poster cardboard for the three screens. Then for each ring, I placed a square of charcoal aluminum screen on a piece of corrugated cardboard and set the template over the screen, keeping the edges in place with metal weights. I went around the template with an Xacto knife, carefully punching down on the screen until I hear each wire pop. Afterwards, I took regular household scissors and cut around and inside the wire ring to free it from the screen, trimming or repositioning loose ends as necessary.

Next I took the two foam core rings and the three aluminum rings up to the attic to paint them with flat black spray paint. It was raining, so I should not paint outside, and I do not have a basement. I positioned the items in a big box and sprayed them there. I was careful to spray the wire rings with quick movements back and forth, never letting my arm stop while spraying, and keeping the spray can at least a foot above the screens. The paint did not clog the holes in the wire screens.

Today I'll use Gorilla Glue or something similar to glue the screen rings between the foam core rings. I'll use a clear protractor to position the screen rings at 30 degrees from each other. Finally I'll brush matte sealant on the surfaces and outer edge of the foam core rings to protect them from dew.

Mike


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Scanning4Comets
Markus
*****

Reged: 12/26/04

Loc: Ontario, Canada
Re: Mega-mod thread for Zhumell dobs new [Re: Sarkikos]
      #4443045 - 03/11/11 07:40 PM Attachment (106 downloads)

Mike,

I still have the screen put away in case I ever get a 12" reflector again !!! I always say I won't but a 12" on deep sky shows quite a bit. I got the plans for it in a book at the library, or online.

As you can see in the pic in my previous post above, there is a huge difference between the flocked part and the grey paint inside the tube. I ended up flocking the entire scope from top to bottom eventually. All three screens are different size and turned certain degrees from each other.

Here are a few pics of the screen, the 12" mirror, and a quick shot of the moon through the 12" reflector I had.


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Scanning4Comets
Markus
*****

Reged: 12/26/04

Loc: Ontario, Canada
Re: Mega-mod thread for Zhumell dobs new [Re: Scanning4Comets]
      #4443066 - 03/11/11 07:52 PM Attachment (107 downloads)

12" mirror...I eventually loosened the clips so the mirror wasn't getting "pinched".

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Scanning4Comets
Markus
*****

Reged: 12/26/04

Loc: Ontario, Canada
Re: Mega-mod thread for Zhumell dobs new [Re: Scanning4Comets]
      #4443069 - 03/11/11 07:53 PM Attachment (139 downloads)

finally...the moon through the 12" scope!

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Scanning4Comets
Markus
*****

Reged: 12/26/04

Loc: Ontario, Canada
Re: Mega-mod thread for Zhumell dobs new [Re: Scanning4Comets]
      #4443079 - 03/11/11 07:55 PM Attachment (136 downloads)

ok...last pic, I promise.

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Sarkikos
Postmaster
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Mega-mod thread for Zhumell dobs new [Re: Scanning4Comets]
      #4443234 - 03/11/11 09:27 PM

Nice pics, especially along the terminator in the second one.

By the way, I have seen pics of planets shot through telescopes which had apodizing masks. The "before" and "after" pics really show the contrast increase AND increase in detail using the mask. That is a true proof of concept. Apodizing masks do work!

Mike


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Jaxdialation
Post Laureate
*****

Reged: 04/01/07

Loc: Northeast, FL
Re: Mega-mod thread for Zhumell dobs new [Re: Sarkikos]
      #4443475 - 03/11/11 11:35 PM

Wow guys, this thread kicks butt.

I'm the guy who did the original Zhumell Mega Mod thread a few years back.

Tim got this thread waaayy further. Funny how that works.
CN is packed with talent, and this thread proves it!

I almost feel like I need to get another Z10 as kind of a statement lol

Do you EVER see threads like this on Orion reflectors?
Know why? They suck too bad to try to get them fixed up

Proceed with your tweaksmanship guys!

Tim --->> <----


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Norm42
super member
*****

Reged: 10/17/08

Loc: Webster, NY
Re: Mega-mod thread for Zhumell dobs new [Re: Jaxdialation]
      #4444126 - 03/12/11 10:05 AM

Not necessarily a mod to the scope, but a low cost way to carry the OTA.

CN Link to Post


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Tim L
Carpal Tunnel
*****

Reged: 12/17/08

Loc: Missouri
Re: Mega-mod thread for Zhumell dobs new [Re: Jaxdialation]
      #4447175 - 03/13/11 04:47 PM

John (Jaxdialation),

Thank you for your kind words!

My Z's had to be in storage so long, I know the "wow" factor will be there all over again when I can put it back into service.

And now, I've got a lot more mods to try thanks to everyone else adding to this thread!


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Twilight
scholastic sledgehammer


Reged: 06/03/10

Loc: Englewood Tennessee
Re: Mega-mod thread for Zhumell dobs new [Re: Tim L]
      #4669496 - 07/02/11 04:11 AM

Quote:

Here's another for new Z owners:

Several have posted having problems bringing their 30mm eyepiece that comes with the scope into proper focus. The common complaint is that there is not enough "out-focus" travel. This is most often heard about the Z8 model.

There's a simple fix for this. On the front of the focuser are two thumbscrews. The upper screw controls tension for the crayford focuser. But the lower screw is a focus lock, useful for astrophotography, but not much needed on a dob used for visual.

The problem is, that lower screw keeps the focuser drawtube from extending all the way. The solution is to loosen the screw several turns (or remove it if you wish), which will let your focuser extend an additional 1/4" and bring your 2" eyepiece to focus.

Clear skies!




Just an update to Tims information. I just checked the back focus/out focus on my Z12" which I purchased in December of 2010 and was having a problem with obtaining enough out focus on several of my eyepieces. After removing the focuser locking screw I am able to obtain 0.27" more out focus. Also the draw tube does not come completely out of the focuser which I was concerned about after reading Tims post. So there is no danger of you expensive eyepieces hitting the ground. Thank you Tim for this recomendation.
Phil


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MrJones
Pooh-Bah
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Reged: 09/15/10

Loc: Indiana
Re: Mega-mod thread for Zhumell dobs new [Re: Twilight]
      #4779922 - 08/31/11 11:48 AM

This is a great thread, here's my feedback and contributions after 2 weeks with my Z12.

1) Laser collimator collimation. It's easy to check and adjust. I used a book wedged in a pot rather than making a v-block to rotate the tube in. I found 20' to be plenty of distance - adjusting at 60' made no difference. I taped a piece of paper to the wall and marked 3 positions, with each of the adjustment screws pointing up. This made it easy to figure out which screw(s) to turn.

2) Laser aperture stop. My beam was elliptical as per others' posts. Apparently you can actually go in and properly seat the lens to fix this but I just added an aperture stop as per the OP. The easiest way to do this IMO is cut a small piece of business card and tape it to the back of the diagonal insert. I used a pin then small nail for the hole in the center, it is slightly smaller than 1mm.

3) Primary holder springs. I replaced mine with stiffer springs cut to the same length (1/2") from a hardware store. Google "#98 wire coil springs". I had to use a Dremel cutting wheel to cut them. I really do believe they help hold collimation better but I would rate this as a low priority mod - the original springs are ok. I also do not quite fully tighten the lock knobs with the new springs.

4) Secondary collimation screws. Rather than buy Bob's Knobs I got replacement screws 5mm longer than the stock (I think original is 35mmx4mm and mine are 40mm) put nylon wingnuts on them (not metric but could be screwed on) then a nut to hold the wing nut. Works great.

5) Counterweight. I got a 4' adjustable nylon strap from Walmart for about $4, wrapped it around the bottom and I hang a 2 lb velcro wrist weight from it with the weight opposite the focuser. This has worked pretty well. I do need to slide the strap some but the weight hanging rather than being tight against the tube seems to help with the zenith balance issue.

Still to go:

Milk jug washers for at least the secondary.
Shower cap for bottom.
Guide knob and either carrying handles or straps for OTA.


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bob irvin
sage


Reged: 03/22/11

Loc: Greater Los Angeles, CA
Re: Mega-mod thread for Zhumell dobs new [Re: Tim L]
      #4780291 - 08/31/11 02:38 PM

Great Thread Tim, thanks.

One thing I did was add two horizontal handles on each side of the base. This lets me lift up my Z10 OTA and base and move it around for short distances. You wouldn't want to carry it very far this way but for a few feet it's great. If you do this mod make sure you use through bolts to hold on the handles. I wouldn't trust wood screws to hold in the particle board.

bob

Edited by bob irvin (08/31/11 02:41 PM)


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Tim L
Carpal Tunnel
*****

Reged: 12/17/08

Loc: Missouri
Re: Mega-mod thread for Zhumell dobs new [Re: MrJones]
      #4781195 - 08/31/11 10:57 PM

Quote:

1) Laser collimator collimation. It's easy to check and adjust....I taped a piece of paper to the wall and marked 3 positions, with each of the adjustment screws pointing up. This made it easy to figure out which screw(s) to turn.




MrJones,

I like this idea a lot--seems easier than the four-position method I described earlier in the thread. I'll give it a shot next time I change batteries in the laser.

Thanks!


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MrJones
Pooh-Bah
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Reged: 09/15/10

Loc: Indiana
Re: Mega-mod thread for Zhumell dobs new [Re: Tim L]
      #4798869 - 09/09/11 07:58 PM Attachment (94 downloads)

Thought I'd document my primary cell changes too.

So glad I took my mirror out to send it for refiguring. I found a lot of problems and I recommend just taking it apart to fix things!

- The screws holding the cell to the OTA were loose.
- The mirror clips were loose.
- The collimation screws had rough bottoms and directly press on metal supports of the cell (like the secondary) - grinding into the support.
- The float support triangles were not aligned.
- There were double sided tape pads on the float triangles and some of the top paper covers had come off so I had to cut the mirror free with a razor. (!)
- The triangles were floppy. Turns out the nylon balls they pivot on had loose screws that would not stay tight.

Attached is a photo of what I started with before removing triangle float supports.


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MrJones
Pooh-Bah
****

Reged: 09/15/10

Loc: Indiana
Re: Mega-mod thread for Zhumell dobs new [Re: MrJones]
      #4798886 - 09/09/11 08:07 PM Attachment (95 downloads)

This is the new "top" of the cell. I left one nylon (might be HDPE) pivot ball exposed so you can see it. Even screwed all the way down they would not stay tight. After removing them (one piece with screw sticking out the bottom) I put a drop of glue on each and screwed them back in to hold them tight.

The old float pads were stripped off with a razor and paint thinner and replaced with glued HDPE (milk jug) pads. I was very impressed with how easily the redone triangles slide across my granite kitchen counter - I think they'll be fine.

CN'er sixela also suggested drilling holes in the triangles and inserting dowels through the triangles on either side of the supports so that the triangles can't rotate out of position (ie with a point facing the center). Still thinking about that one but note that the triangles do already have holes in them.


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MrJones
Pooh-Bah
****

Reged: 09/15/10

Loc: Indiana
Re: Mega-mod thread for Zhumell dobs new [Re: MrJones]
      #4798894 - 09/09/11 08:13 PM Attachment (93 downloads)

Finally I put 2 layers of HDPE milk jug pads where the collimation screws contact the cell. You can see through the pads where the collimation screws have worn nice divots in the supports after just a few weeks of use. I also smoothed and flattened the ends of the collimation screws on a grinder.

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Tim L
Carpal Tunnel
*****

Reged: 12/17/08

Loc: Missouri
Re: Mega-mod thread for Zhumell dobs new [Re: MrJones]
      #4799152 - 09/09/11 11:10 PM

Hey MrJones,

Nice pics! The Z12 mirror cell is a lot different than the Z10. Thanks for adding your upgrades and improvements.

I have a question about the last photo you posted. It looks to me like the spokes at 12, 4, and 8 o'clock have screw holes in them at the rim--is that where the collimation screws go? If so, then I would guess the ones with the milk jug plastic are for the locking screws, and I don't know if it's necessary to tighten those down hard. I usually just set mine to add a slight pressure while keeping an eye on the laser collimator.

Clear skies!


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MrJones
Pooh-Bah
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Reged: 09/15/10

Loc: Indiana
Re: Mega-mod thread for Zhumell dobs new [Re: Tim L]
      #4799169 - 09/09/11 11:24 PM

You can see the scratch marks from installing replacement springs on those spokes around the holes for the lock screws. Still deciding if I want to do something about that. The collimation screws are threaded into the other piece. And strange that the Z10 cells are a lot different!

Edit: Obviously backwards - sorry. The pads are for the locking screws which I do use.


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ernie bogusch
journeyman


Reged: 03/01/11

Re: Mega-mod thread for Zhumell dobs new [Re: skizoid]
      #4800935 - 09/10/11 11:44 PM

Quote:


Gave the Dub Dob (I like that) it's first field test tonite. 8F ... perfect viewing weather! Clear sky anyway. Gives new meaning to the phrase "crisp air". Set it up about an hour before sunset, then went out to play. Jupiter was an easy target, so I used that to align the finders with the OTA. That Telrad is sweet for quick 'n dirty! I could see Uranus, but wasn't getting any decent detail, so I'm gonna have another go at fine tuning the mirrors. Wasn't too long after sunset, so I still had quite a bit of heat distortion to deal with. I'm happy enough that I could see anything at all first time out. Speaking of first time out ...








Skizoid,
I realize this thread is old, but I just got my Z8 and I will be making some to the mods you suggested.

Some questions.

1) You placed the handles on both sides. Wouldn't one handle in the top center make carrying the OTA, and placing the OTA into the base much easier?

2) I like the backup plate in the inside of the OTA. Is one handle strong enough to carry the OTA without stressing the steel tube? Is you backup plate steel or aluminum?

3) Why didn't you mount the Telrad closer to the edge of the scope? The optical finder would not be in the way and it seems more convenient to use in that position.

Thanks,
Ernie


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