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Messages - frenafverbi

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Oops, I accidentally erased it, as I was going to add a simulated igram.

Okay, what is the observed (photographed) interference pattern nulled against? in an actual test you're looking at a deviation relative to a sphere, with such deviation being the smallest when the reference sphere corresponds to the radius of curvature of the 71% zone.

Your null is a set of numerical values expected from a surface with the desired conic constant. Or is it?

At any rate, the number of fringes required for a working igram still looks huge evenw ith the art. null on.

PS and this is not really a working igram...

Back in the 1960s-70s:
Several 4", 8.75", 12" & 16" mirrors
Several 8.75" optical flats.
A 5" f/15 and several smaller achromats.
Several 60° dense flint prisms.
And lots of simple lenses.
Had I worked by hand instead of on my own machine:
I might have made many more.
And smoked far less.

Beginners Forum / Re: Overwhelmed
« on: February 03, 2018, 06:28:44 AM »
Wendy, you've been given a lot to take in here, but let me echo binoculars and 'Left Turn at Orion', the book, as a good starting point. Baby steps at this point. Baby steps. I'd also highly recommend that you save aeajr's posting. Print it, save it to your computer, whatever. Just save it. I firmly believe that when the time comes for you to buy a scope, this posting should be your guide. Be patient, purchase one thing at a time. Getting binocs will also give you a chance to build up your piggy bank again for next year. Good luck on your return to our world!


Mounts Questions & Expirience / Re: Losmandy G11 with Gemini 2 on the way!
« on: February 03, 2018, 01:21:14 AM »

From memory (again) they can and it is not expensive. It is a mounting bracket swap out. I believe that some day will come quicker than you imagine once you have a near miss or two with the motor's in their present configuration. This will happen even with the case you have for it. Here is a thread here on the subject from back in Jan-March of this year...https://www.cloudyni...-gm8/?p=7669345

Carson, do you recall when they started placing the tucked-in motors on the G11? I looked on the Losmandy site, but couldn't find that info. The one I'm buying was purchased new in March 2015. It's got the one-piece worm block, which I believe is now standard on the G11.

Thanks for posting that link, Carson, as it just gave me the answer to my question (early 2017). The G11 that I've ordered already has the RA extension, which should also help provide a little extra clearance.
Not to butt in but the tucked in motor upgrade became available about mid 2017 for the first time. I'd recommend using your mount the way it comes (except I agree about getting the clutch knobs and tripod knobs) and then if you feel the need for the upgrade you can contact Losmandy about getting the tucked in motor upgrade.

By the way, you can also upgrade your mount to the G11GT which adds a Losmandy Titan RA and increases the capacity to 75lbs from the 60 your G11 has.

Mounts Questions & Expirience / Re: CGEM DX teardown help
« on: February 03, 2018, 12:58:17 AM »
You can either try to retap those holes up to a 1/4-20 thread or use some short Helicoils (e.g., 5mm) since the metal isn't very thick..

Beginners Forum / Re: Understanding the effects of Magnification
« on: February 02, 2018, 10:44:03 PM »
Don, thank you for the advice.

Beginners Forum / Re: Side effects of dark skies... "Now I understand"
« on: February 02, 2018, 08:03:32 PM »
It is important to remember that observing from your backyard gives you experience with observing and allows you to evaluate, test and improve your equipment so that you will be ready to take as full advantage as you can of dark skies when you get to see them.

There are still interesting DSOs, even nebula and galaxies, to be seen under ugly skies.

If dark skies have jaded you, perhaps that is on you, not anyone else.

I've suspected that slight overcorrection during cooldown is because the edge loses heat and contracts faster, creating a broad TDE.
It's generally not a smooth overcorrection as seen in a good star test.

So does a cell that insulates the edge gain us anything?


Yes, a mirror that never cools down. Air flow around the edge is essential to quick cooling.

Beginners Forum / Re: North American Nebula - Am I just blind?
« on: February 02, 2018, 01:29:36 PM »
aeajr, don't worry about distracting from the conversation...I find your comments very helpful and the discussion is for benefit of all.

Curious, do you ever attend star parties on building tops there in NYC? I imagine that would be a unique experience.

I am not actually in NYC. I am 25 miles east of Manhattan in Nassau County but the glow of Manhattan, Brooklyn, Queens and the Bronx spill over into my skies combined with the air polution and the Long Island humidity.  So my air is never really transparent. It can look good to the eye but when I get an eyepiece on a bright object you can see the glow around it from the atmosphere.

My other gauge is that people with the same scopes as I have report seeing far more detail on Mars, Saturn and Jupiter than I see.  Well, it can't be the scope so it must be the air.

It is what it is.  I am still enjoying seeing what I can see.


I would like to hear from Nagler and Ethos users if they can see any kind of image deterioration when they start placing their observing eye away from the optical axis of their scope (in other words turning their heads!), my guess being that eye sweeping in a fixed postion is not practical beyond 70°... coma and field curvature not being considered here.
I will soon be using an undriven 12" dobs, being able to clearly see without eye (or neck) strain at 300x is my goal.


You're asking two questions.

The first question is edge performance. My guess is that every Ethos owner (myself included) almost immediately wants to evaluate edge performance the first night out. Not to worry, it is very, very good. Star images stay pretty tight. I would not do that for planetary observing (on-axis is where you always get best performance), but for star fields it's solid performance. I have never heard anyone criticize it.

The second question is more ergonomics, and this is where you see opinions diverge based on personal preference. Some people are fine with it, others don't like it. After a couple of years, I sold my Ethos years ago due to the unusual neck and eye movements. A preference.

Since your second question is a "preference" question, the only way you can answer this question is to try it yourself.

If your primary motivation is drift time (vs. visual effect), you owe it to yourself to investigate tracking solutions - an equatorial platform or a ServoCAT. Tracking time is effectively infinite. Very relaxing.
Before Ethos I used to think 82-84 degree AFOV was cheaper than tracking (especially with large dobsonians).
However with the high cost of 100-120 AFOV, I now believe tracking would be cheaper; however I would still love the wide 100-120 AFOV and their corresponding wide TFOV for their magnification.

P.S. If I were to get a new telescope, it most likely would have tracking and have go to (or push to) to minimize the time to find and confirm objects.

That's probably true.

It's instructive to note that the EM-200 is a design that dates from 1989.


The AP600 is from the mid-90's (probably 1996 time frame). Synta didn't clone the Mach1 to make the EQ6 because the Mach1 came out in 2006.

The big factor with the EM-200 (vs the Mach1and G11) is that it is <strong class="bbc">cast[/b], non CNC. Lends itself to cheaper manufacturing. That said Takahashi casting is a world away in quality compared to the EQ6 or CGEM.

Isn't the A-P 600E an EM-200 clone also?

Never did get a 4mm

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Beginners Forum / Re: Zhumell 8 or 10 dob
« on: January 31, 2018, 01:43:13 AM »
Scopes are like boats. No matter how big you go, you always wish it was bigger.

Beginners Forum / Re: Eyepieces worth the extra $$$?
« on: January 31, 2018, 12:19:34 AM »
So my first question is, Isan expensive eyepiece really that much better? (Is a $250 eyepiece 5x better then a $50 eyepiece?)

Know thy self.

"Better" can mean different things to different people.

As a wide field addict, 'better 'for me means very wide &amp; sharp FOV for better macro views of the heavens.
I started with Plossls and 80s Meade Orthos but after looking through a Pronto c/w a 2" focuser &amp; 31 Nagler T5
I was totally blown away by the 60 % light gain , 82 degree FOV and field sharpness...still am over a decade later. It was the view I had dreamed of and a defining experience... much like looking out a space ship window since the human eye is a 50 degree FOV. I have been hooked on wide field viewing ever since.
As my buddy said " It's like standing on the bridge of the Enterprise - NCC 1701.

Once the wider FOVs were in my brain it was hard to return to Plossls etc. the same way it's hard to return to VHS after CDs.The 55 mm TV Plossl has collected dust since and I bought some premier short FL EPs that , while pricey, also collect dust because I'm much less a DSO man than I thought when I bought them.

So for me , leaning to a wide field genre, the extra cash is easily worth it but I'll stay with older 82 degreeT 4-6 Naglers and pass on the newer , pricier super WFOVs.

Know yourself and your sweet spots and buy accordingly.

Reflectors Telescopes Forum / Re: Z12 zhummel vs Meade 12 lightbridge
« on: January 29, 2018, 10:08:42 PM »
Only 1500 with shroud gps unit dc adapter 3 eyepieces a dolley carrying cases and a cover for the whole.scope in storage.

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