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Equipment Discussions >> Reflectors

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skizoid
member


Reged: 01/12/11

Loc: 43.223N / -85.551W
Re: Mega-mod thread for Zhumell dobs new [Re: skizoid]
      #4327781 - 01/20/11 03:52 PM

Feet.

Those silly little feet they put on the rocker box are just south of useless. Did some digging and came up with these ...



Four inches, and they turn out another 1¼". That should keep the base above the mud 'n the blood 'n the beer and provide for more than enough leveling for the average viewing location.

Here's the source for the legs. They do NOT come with any mounting hardware. The barrel is metal, and the foot is nylon so grass and gravel shouldn't hurt it. $10 each, but hey, I'm worth it.

Camar Adjustable Legs from Closet Masters

PS - just came in the mail today, so I haven't mounted them yet. I do plan to tear the rocker box down to where I can bolt them thru the bottom board. Don't trust surface mount in particle board. I already managed to knock the eyepiece holder a couple times and work that loose. That was easy enough to fix - I'll have to recess the heads on the foot hardware so they don't interfere with the bearing. Those large square mounting plates should make for a sturdy platform when done.

Also didn't much care for all the raw edges on the rocker box (a common complaint I understand), so I did some serious sealing before assembly. I used a pipe cleaner to get paint into all the holes, primed all the edges, put a couple coats of gravel guard automotive paint for texture, then added a layer of black silicone to all the mating surfaces. Wiped the excess, then once that set, a couple coats of gloss fabric paint. That stands up to dents and dings a lot better than your average bug bomb.


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skizoid
member


Reged: 01/12/11

Loc: 43.223N / -85.551W
Re: Mega-mod thread for Zhumell dobs new [Re: skizoid]
      #4327796 - 01/20/11 03:59 PM

(Better sneak this one in before the pixel police cut me off)



Still need to do the bottom plate and damper for the fan, add a carrier for the battery pack, update to the 5 degree setting circle, and maybe a flame job for the OTA ... but ... I'm gettin' there!


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Fimpster
Carpal Tunnel
*****

Reged: 09/24/09

Loc: Aprox. 1 AU from Sun
Re: Mega-mod thread for Zhumell dobs new [Re: skizoid]
      #4328071 - 01/20/11 06:00 PM

Keep going skizoid! This is quite the show you're putting on. I cant wait to see what this thing will look like when your done. Will you ever be done?

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dwright
sage


Reged: 12/12/09

Loc: Sonoran Desert
Re: Mega-mod thread for Zhumell dobs new [Re: skizoid]
      #4328107 - 01/20/11 06:20 PM

Quote:

(Better sneak this one in before the pixel police cut me off)



Still need to do the bottom plate and damper for the fan, add a carrier for the battery pack, update to the 5 degree setting circle, and maybe a flame job for the OTA ... but ... I'm gettin' there!



Cool... a Dub Dob...


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skizoid
member


Reged: 01/12/11

Loc: 43.223N / -85.551W
Re: Mega-mod thread for Zhumell dobs new [Re: dwright]
      #4328429 - 01/20/11 08:16 PM

The People's Telescope - Fahrvergnugen!!

Now that I've "borrowed" the logo, I'm thinking of asking VW if I can borrow Helga for a while to do a video on collimation. Betcha that'd get some hits on YouToob ...

So far this has been more fun than a bunch of monkeys shooting paintballs on a roller coaster ...

I did pick up on a 2x Barlow (mounted on the previous pic). One free with every two VW ornaments ... <G>

If anyone is interested, you can either buy the emblems from VW for $40 each, or ...

Here's where I got mine - $2.99

The Zhumell barlow has a longer barrel than the 2" adapter that comes with the Z8. The barlow lens is standard thread, so you can screw that off and replace it with a 2" filter AND run the focuser all the way in without banging the lens. Kewl ... be interesting to see what effects combining filters has. I understand two polarizers can be pretty spectacular.

Image removed by moderator. We do not allow reproducing images from other web sites on CN. Please do not do it.

Edited by Don W (01/20/11 08:18 PM)


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sawacs
sage


Reged: 03/15/06

Loc: KOKC Area
Re: Mega-mod thread for Zhumell dobs new [Re: skizoid]
      #4330613 - 01/21/11 07:58 PM

Small tip..

You can easily reduce your secondary mirror size by using another brand secondary holder but you have to be willing to drill your 4 vane hub out

Using a drill press, I successfully "wollered" the hole out enough to accommodate the 2.14" Protostar secondary mirror and mount. In fact, the aftermarket collimation screws many of us use for our Orion and Zhumell scopes fit perfectly in the Protostar dimples on the secondary.

Although I do have the 3 vane spider from Protostar, I tried this out just for kicks:)

Cheers,

Shawn


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Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Nyctophobia, Maryland, USA
Re: Mega-mod thread for Zhumell dobs new [Re: sawacs]
      #4330929 - 01/21/11 10:44 PM

I have a Z8. The secondary is oversized, at least for planetary/lunar observing. The 50mm ma yields a 25% central obstruction. I recently replaced mine with the 36mm secondary and diagonal hub made for a 5" Newt I have, which will reduce the CO to 18%.

I removed the Z8's diagonal and hub from its spider vanes. When the Z8's diagonal vanes are attached to the OTA, they are a little too short to reach the smaller diagonal's hub. I went to Lowe's Hardware and found small, black rubber gaskets and longer screws to take up the slack between the hub and the spider vanes. It would be better to have longer spider vanes or longer bolts to attach the vanes to the OTA, but finding either is easier said than done. The gaskets and rubber screws do work for now. At this point, I don't want to buy a new, complete secondary mount.

Now for a break in this cold, windy, snowy and icy weather so I can test the Z8 to see how it performs on Jupiter or Saturn. I hate winter astronomy! But at least it gives me plenty of time to work on scope modifications.

Mike


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Jason D
Postmaster
*****

Reged: 10/21/06

Loc: California
Re: Mega-mod thread for Zhumell dobs new [Re: Sarkikos]
      #4330949 - 01/21/11 10:53 PM

Quote:

I have a Z8. The secondary is oversized, at least for planetary/lunar observing. The 50mm ma yields a 25% central obstruction. I recently replaced mine with the 36mm secondary and diagonal hub made for a 5" Newt I have, which will reduce the CO to 18%.



Rack the focuser's drawtube 1/2 way then insert a collimation cap or a cheshire. Can you see all primary mirror clips simultaneously? If no, your secondary mirror is too small.
Jason


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sawacs
sage


Reged: 03/15/06

Loc: KOKC Area
Re: Mega-mod thread for Zhumell dobs new [Re: Jason D]
      #4330960 - 01/21/11 10:57 PM

Jason,

Wouldn't the fact than you can or cannot see the mirror clips be solely determined by what type of observing you do?

For instance, a purely planetary observer would not mind light falloff with a smaller secondary?

Just curious:)


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skizoid
member


Reged: 01/12/11

Loc: 43.223N / -85.551W
Re: Mega-mod thread for Zhumell dobs new [Re: sawacs]
      #4330973 - 01/21/11 11:02 PM

I've think I've already proven my willingness to drill, cut, hack, and otherwise hopefully not mangle beyond hope most anything ... <G>

That said ... smaller secondary. Hmmmmm. I gooooogled it (yeah - I feel dirty) and I found some interesting stuff about maybe reducing chromatics and increasing contrast for planetary viewing? More light - more might kinda thing. I also saw some cautions about not undersizing the secondary, as that can cause light reflected from the primary to miss the corner, in effect making for a "smaller" scope. Wondering how you narrowed your choices down to the Protostar? Also wondering if anyone knows if all the Zee Dubs use the same secondary?

The three vanes is an interesting idea and would be easy enough to do. I can see where that could definitely allow more light into the tube under certain conditions. Hadn't thought of that - I <almost> was going to try flocking the vanes on mine with some leftovers, but increasing the thickness, in retrospect, would have been a bad thing.

(Hey! I thought my mod list was supposed to be getting shorter!!)

Long as we're on the subject of light, I'm also having second thoughts about a flock shield I stuck around the focuser inside the OTA.



Thumbs up or thumbs down? The 2x Barlow (minus lens) is completely retracted into the tube in this pic. With the lens mounted, the shield is even with the end ...


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sawacs
sage


Reged: 03/15/06

Loc: KOKC Area
Re: Mega-mod thread for Zhumell dobs new [Re: skizoid]
      #4331029 - 01/21/11 11:34 PM

Quote:

I've think I've already proven my willingness to drill, cut, hack, and otherwise hopefully not mangle beyond hope most anything ... <G>

That said ... smaller secondary. Hmmmmm. I gooooogled it (yeah - I feel dirty) and I found some interesting stuff about maybe reducing chromatics and increasing contrast for planetary viewing? More light - more might kinda thing. I also saw some cautions about not undersizing the secondary, as that can cause light reflected from the primary to miss the corner, in effect making for a "smaller" scope. Wondering how you narrowed your choices down to the Protostar?

The three vanes is an interesting idea and would be easy enough to do. I can see where that could definitely allow more light into the tube. Hadn't thought of that - I <almost> was going to try flocking the vanes on mine with some leftovers, but increasing the thickness, in retrospect, would have been a bad thing.

(Hey! I thought my mod list was supposed to be getting shorter!!)

Long as we're on the subject of light, I'm also having second thoughts about a flock shield I stuck around the focuser inside the OTA.



Thumbs up or thumbs down? At the very least I'm thinking I should shorten it up a bit ...





Zkizoid,

Regarding the secondary, you can go too small and a 2.14" on an 10" F5 mirror is about the smallest "I" would try and go.

My mirror came back, from OWL right at F5 which means I could actually go to a 1.83" mirror but would be restricted to using 18mm eyepieces and under to retain full field illumination if my kakalations are correct:) The original specs on the Z10 were F/4.92, if I am not mistaken.

My kind of observing is mainly planetary, moon and double stars with the Z10 scope so the smaller secondary is not a concern.

The three vane vs four is always a hot topic which I will not dare get into. However, I much more prefer six dimmer spikes over four brighter spikes but this is just personal preference:)

I would not try and flock the spider vanes but rather put a nice coat of flat black paint on them. The focuser flocking is a great idea so long as it does not intrude into the light path!

My current Z10 is basically a prototype. Zhumell sent me two Z10's for the price of one due to some quality control issues. Once this scope is configured exactly, I plan on taking the second Z10 and drilling only one set of holes

Regarding the Protostar decision, they looked like a good alternative to the four vane system and I decided to give it a try. I am not completely happy due to some randomness in the collimation system due to the plastic shaft but I am still working that issue:) When everything is in collimation and ya don't bump the scope, it works!

Respectfully,

Shawn


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Jason D
Postmaster
*****

Reged: 10/21/06

Loc: California
Re: Mega-mod thread for Zhumell dobs new [Re: sawacs]
      #4331040 - 01/21/11 11:39 PM

Quote:

Jason,

Wouldn't the fact than you can or cannot see the mirror clips be solely determined by what type of observing you do?

For instance, a purely planetary observer would not mind light falloff with a smaller secondary?

Just curious:)




Shawn,
If you can't see all primary mirror clips simultaneously from the focal plane, it means:
1- You are not utilizing the whole aperture of your primary mirror. For example, if you can only see 90% of the diameter of your 10” mirror, then you have effectively 9” mirror – a 20% aperture area loss.
2- Light cones touching the center of your FOV are reflecting off areas close to your secondary mirror edge – not the most ideal area of your secondary mirror.
3- Your CO% calculation will have to be based on your effective aperture – not real aperture. Back to our example, do not calculate CO% as 2.14”/10” = 21.4% but rather as 2.14”/9”=23.8%. But wait, assuming the stock mirror was 2.5”, the original CO% was 25% -- not much different.
Jason


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sawacs
sage


Reged: 03/15/06

Loc: KOKC Area
Re: Mega-mod thread for Zhumell dobs new [Re: Jason D]
      #4331047 - 01/21/11 11:42 PM

Jason,

I get it!

Howly cow moo moo!

Finally, the light bulb came on and is shining brightly..

Thanks for the explanation sir..

Respectfully,

Shawn


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Jason D
Postmaster
*****

Reged: 10/21/06

Loc: California
Re: Mega-mod thread for Zhumell dobs new [Re: sawacs]
      #4331078 - 01/22/11 12:03 AM

Shawn, when I upgraded my secodary mirror to Protostar quartz, I ordered the 2.6" mirror. The stock mirror size was 2.48". I felt the 2.14" was too small and too risky.

By the way, anyone can use a temporary front-end aperture mask placed at the OTA/UTA opening to increase their CO% (OK, aperture will be lowered) to see if they can discern a difference.

Jason


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sawacs
sage


Reged: 03/15/06

Loc: KOKC Area
Re: Mega-mod thread for Zhumell dobs new [Re: Jason D]
      #4331109 - 01/22/11 12:22 AM

Copy all Jason..

I went with the 2.14" from Protostar and have never been happier!

Now, you do have me thinking on this mirror clips thing..

When I take the CatsEye Teletube and place it in the focuser in the correct position for a F5 scope, I do see the clips. However, if I back it off to where the actual eyepiece would be, I do not see the clips? Am I confused?

Even though I do not see the "ears" of the primary at the eyepiece height, I should still be getting all of the primary light in the center of the eyepiece correct?

I feel myself becoming more discombobulated and I thought I had it figured out


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skizoid
member


Reged: 01/12/11

Loc: 43.223N / -85.551W
Re: Mega-mod thread for Zhumell dobs new [Re: sawacs]
      #4331111 - 01/22/11 12:23 AM

The focuser flocking is a great idea so long as it does not intrude into the light path!

Heckfire ... the entire telescope intrudes into the light path, don't it? Kinda the objective, ok - capturing some celestial object's soul and all. Seems like it'd be more of a concern on the bounceback. Anyway, the shield just pops in and out of the hole, so I can experiment with it to see if there's any noticable difference with or without.

Found some interesting reading on the subject.

Sizing Up the Newtonian Secondary

Interestinger and interestinger ...

If I'm reading it right, seems that consensus of experts (yah - like THAT could happen) is that anything over 20% ratio, secondary to primary, can degrade the image. The Z8 (roughly 2") comes in at 25%, which leads me to believe they use the same secondary as the Z10 as a cost savings measure OR that they just have a different opinion on the subject. Theoretically, 1.6" would be ideal? Kinda simplistic - looks I'm going to have to do some math here to get the ideal size. Mirror size, focal length, pi (mmmmmmm ... pi!) ...

PS - who's come up with a super duper easy and least destructive as possible way to clean the primary on these things? I was thinking a swiffer duster (modded of course) on an extension handle would be pretty slick for quickie cleanups ...


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Rob E
Village......clown
*****

Reged: 05/20/09

Loc: Where Independence Was Won
Re: Mega-mod thread for Zhumell dobs [Re: skizoid]
      #4331129 - 01/22/11 12:32 AM

Quote:

PS - who's come up with a super duper easy and least destructive as possible way to clean the primary on these things? I was thinking a swiffer duster (modded of course) on an extension handle would be pretty slick for quickie cleanups ...




Don't do it or you'll regret it forever..


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sawacs
sage


Reged: 03/15/06

Loc: KOKC Area
Re: Mega-mod thread for Zhumell dobs [Re: skizoid]
      #4331133 - 01/22/11 12:38 AM

My best view ever of a planet was through and old Meade 6" Starfinder which I paid 100 bucks for back in 1991. To this day, I have not been able to produce that type of contrast and detail in the planets period! However, all of my scopes have become bigger than the 6"er.

I had a chance to look at Jupiter through and 18" Obsession a while back and let me tell ya..... The planet was big but the details were not. It was simply too bright and washed everything out..

There is a reason why folks build 10" f/6 scopes or 8" f/7 scopes and that is for the clarity they offer on the planets.

Okay, where did the above statements come from...

Regarding primary mirror cleaning, clean only as a last resort. One little handy device I found from the camera department is something called a "rocket blower". It looks just like a rocket and works great for taking dust of your eyepieces and or mirror. If you absolutely have to clean, do a search on the forums and you will come up with a wealth of information.

Cheers,

Shawn


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skizoid
member


Reged: 01/12/11

Loc: 43.223N / -85.551W
Re: Mega-mod thread for Zhumell dobs [Re: Rob E]
      #4331144 - 01/22/11 12:44 AM

Shhhhhhhh ... was that the "voice of doom"?

OK - so chrome polish and an orbital buffer are definitely out of the picture. Gotcha.

I understand the LESS you clean one of these things, the better. My problem right now is construction dust. Canned air maybe? I was thinking, tap a hole in the OTA above the mirror surface, add an o-ring, heat the plastic straw from a can so it angles down towards the mirror, then just give it a blast when needed ...

I did find this ...

Cleaning your telescope's mirrors


<EDIT>

On the canned air bit, I was just reading the contents on one. There's some strange stuff in those cans! Maybe not. I do like the straw thru the OTA thing tho - betcha you could mod a camera lens duster to do the same thing. One of those eye 'n ear spritzer bulbs should do the job nicely too.

* Anybody know how to get earwax off a primary? <G>


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sawacs
sage


Reged: 03/15/06

Loc: KOKC Area
Re: Mega-mod thread for Zhumell dobs [Re: skizoid]
      #4331161 - 01/22/11 12:57 AM

Quote:

Shhhhhhhh ... was that the "voice of doom"?

OK - so chrome polish and an orbital buffer are definitely out of the picture. Gotcha.

I understand the LESS you clean one of these things, the better. My problem right now is construction dust. Canned air maybe?

I did find this ...

Cleaning your telescope's mirrors




What you found will probably work great, when the time comes

I am about the pickiest, most perfectionist kind of person you would ever want to meet when it comes to my scopes. However, after battling dust "grannies" over the years, I have relaxed. Don't sweat the small stuff and simply observe.

If your constructing stuff, place the mirror aside, construct, then place it back in. It takes a lots and lots of buildup before you will ever notice image degradation.

Earlier today, I was placing my Z10 mirror cell back into the scope and noticed a "splotch" on the mirror which I thought was coating failure. I literally could not stand it so I placed a drop of "ROR" on a Q-tip and rolled it onto the blob. Lo and behold, it came off with no ill effects along with a lowered blood pressure on my end:)

Btw, if your gonna polish with an orbital polisher, make sure you use 80 grit and nothing more: it will polish much faster!

Cheers, Shawn


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