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Messages - szenawahle

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Mounts Questions & Expirience / Re: Mount Payload / Capacity Table
« on: February 08, 2018, 11:22:02 PM »
The AVX payload should have a 90% reduction to about 3 lbs.

Oh... Ha... Ha...

Care to show your images?

I'll show you mine first.

Put up, or shut up.

Beginners Forum / Re: Simple scope for micro-resort
« on: February 08, 2018, 07:46:23 PM »
I can't imagine a reflector in this situation. Guests would mess with collimation, drop things into it, whatever. I can't imagine how much they'd mess up an EQ mount either.

I have a feeling if you have multiple eyepieces, they'd get dropped or lost. So a zoom would make sense. Non-astro people would be confused by reversed images.

So something weatherproof, not needing collimation, with an erect image. In other words, a spotting scope. Maybe 20-60 zoom, on an alt-az. They could use it terrestrially, as well as get a taste of astronomy. Something like a Celestron Ultima and a Twilight 1.

Well, I'm not a GoTo fan, but find EQs a pain for visual, just don't like weight lifting either. I miss the old fork mounted SCTs

ATM, Optics and DIY Forum / Re: Star tests and Ronchi
« on: February 04, 2018, 11:33:15 AM »
Not saying it's wrong but the shadows on thatFoucault simulation seem surprisingly contrasty for a 6" f/13 with only 1/4 wave error.
Just saying....


Do you have a better example? Have you tested a 6-inch f/13.333 sphere at its prime focus with a kniofe-edge? You can stop down an 8-ich f/10 sphere to 6 inches. The software used is a powerful code-driven professional program. Limited engineering licese is US$3500 and a full license is US$5000. THis does not include annual maintainenace licese.


PS The test setting is at the best focus, 1/18 wave RMS, not 1/4 wave PVW.

General Astronomy & Observing / Re: Question about galaxies coming together
« on: February 03, 2018, 04:34:51 AM »
Someone smarter than me once explained that stars in galaxies are so far apart that when galaxies "collide" the stars pass each other slowly with a considerable distance between them. Galaxies are not solid and so do not smash into each other but rather pass through each other.

Beginners Forum / Re: Which telescope to choose?
« on: February 02, 2018, 01:49:58 PM »
So my wonderful wife bought 2 telescopes for me for xmas and is going to send one back after I choose. Both are Celestrons. The Powerseeker 127EQ and the Inspire 90AZ with smartphone adapter. I want to be able to take pictures of the moon. Any advice would be helpful in making my choice.

She even suggested I return both and put in whatever extra money I needed to to get a scope that would be a more effective use of the money. So this opens up to suggestions for scopes for a beginner that could be used for photography of the moon specifically with an additional investment of say $200 over the cost of the more expensive of the 2 above scopes.

I looked these up. With the 127EQ you might be able to try some manually driven piggyback photo with a DSLR and 50mm lens.

I probably would not like the 90AZ, unless it didn't cost much.

A 6-inch Dob will work better than either.

ATM, Optics and DIY Forum / Re: Swayze mirror?
« on: January 31, 2018, 11:50:49 AM »
Mine took about 6 months. 5 months being refigured and 1 month at the coaters.

I'm very happy with the mirror and am a satisfied customer but it did take 4 months longer than estimated.

It seems that you need to have lots of patience when dealing with any telescope related stuff. Whether it's refiguring, recoating or even waiting for the clouds to clear up!

That's the rub. If it's going to take a year, just tell me the truth. Then I can go from there. Telling someone you can do a job in a couple of weeks when you know you can't and then it takes a year is just plain @#%$#.

Light Pollution Topics / Re: New Global Light Pollution Atlas
« on: January 31, 2018, 06:37:11 AM »

From my own experience with an Skywatcher ED80 imaging scope F7.5 @ 600mm, and an Orion SSAG with a 9x50mm finder scope - I have never had flexure be an issue normally at these focal lengths. That said, I agree that mounting on a metal plate is a good start.

Have you used the calculator to get your guiding settings? The correct focal length for my 9x50 guide scope is 162mm - do you have something similar?

I find even on my tuned EQ6 - it performs better with 80-90% aggression and a refresh rate of 2-4 seconds with the SSAG , depending on my OTA. (MN190 or ED80).

Anyway, just a couple of ideas.

I have to regularly check the mesh on the gears with this mount - it's no Astro Physics Mach 1, that's for sure.

General Astronomy & Observing / Re: Astronomy Misconceptions Quiz
« on: January 31, 2018, 04:39:37 AM »
A lifetime of math has demonstrated to me that yes, math sucks.

My math professor hinted to the class one day that he thought that there is something fundamentally flawed about the mathematics that we use. He didn't elaborate.

Beginners Forum / Re: Motorized Scope for $500 or less?
« on: January 30, 2018, 11:57:05 PM »
But, Ed asks a very good question.  Does your friend want GoTo or just motorized?  Huge difference.
I'm not sure there's a big difference in practice. These days, Go To is often the cheapest possible route to achieve motorized tracking. It's certainly simpler than adding a motor to a low-end equatorial mount, and low-end equatorial mounts tend to work pretty poorly.
On the whole, for a beginner who wants motorized tracking at low cost, a Go To scope seems to me like the best solution. The fact that it has Go To capability is a nice free side-effect.

So true  other than the new Synta/Orion table top trackers.
With a goto you can just turn it on or depending on the model just do a one star alignment to activate tracking.

Do yourself a favor. Go equatorial. But spare yourself all the awkwardness of a GEM that bothers you and get an Avalon M Uno or M Zero. Easy as pie. With all the advantages.


Beginners Forum / Re: Planets through a 70mm Refractor?
« on: January 30, 2018, 12:08:42 AM »
Jupiter was way too bright, it looked like a white orb with absolutely no detail

My first telescope was a 114 mm reflector. The first time I looked at Jupiter I saw the same thing, a featureless circle. Then I learned that the included eyepieces that came with my telescope are not that great. Since I was on a budget, I purchased an orthoscopic eyepiece.

A few weeks later, I went to a star party and someone had a 12" reflector. They were commenting on how many cloud belts they were seeing on Jupiter. I asked if I could take a look, and if they didn't mind if I try my new eyepiece on their telescope. Sure enough, they were several bands visible, and yes, I could see them with my new eyepiece.

Knowing that I now had a decent eyepiece, I went back to my own telescope and put on my new eyepiece. After being able to get clear focus I was able to see a couple of bands on Jupiter. I was wondering why I was not able to see them before...

A few years later, I ordered and assembled a galileoscope. When I pointed it to Jupiter, I was able to see two bands, even though it is only 50mm in aperture.

Observing is an art, and it takes time to develop the skill.

Keep at it.

clear skies

Beginners Forum / Re: Dumb newbie question
« on: January 29, 2018, 10:37:02 PM »
All true, but the interesting thing is the OP stated his has a removable "center", which I take to mean it is centered over the central obstruction (i.e. secondary mirror). My Skywatcher dob has the same arrangement as in the link you provided above, in which the aperture stop is off-center, so it is not aligned with the central obstruction.
I did say center, and the cap is centered. This morning, I removed the center cap and took a look through the EP. The secondary mirror did not pose a problem. I didn't find that removing the center cap improved magnification over removing the entire tube cap (if that is the effect of increasing the focal ratio of the scope).

Thanks, all, for your answers.
Thinking some more on this, maybe it will work as an aperture mask with a center cap. After all, the goal is to reduce the aperture to some chosen area A.
So, if you want an area A then you could use an off-center hole of radius r such that pi*r<sup>2</sup>=A.

*Or* you could use a larger hole of larger radius r<sub>c</sub>&gt;r that is centered on the secondary obstruction. In this case the aperture will be pi*(r<sub>c</sub>)<sup>2</sup> of the larger hole minus whatever area is obstructed by the secondary mirror. Just pick r<sub>c</sub> so that this difference equals the target area A.

Edited to add: BTW, to add to Alex' post above, usually the reason to use an aperture mask to increase the focal ratio is that with an achromatic refractor, the larger focal ratio reduces chromatic aberration. I'm not sure of the benefits of larger focal ratio with a reflector, I think it may make it less sensitive to imperfections of the mirror for one thing, and of course will reduce the amount of light coming in which might be useful with a really bright object like the moon or Venus. Or it may have just been an opening for a solar filter as I think someone mentioned above.

ATM, Optics and DIY Forum / Re: 'Plumber's Scope' RFT
« on: January 26, 2018, 04:04:10 AM »
PVC is great stuff for TN's. Wish it had been available back when I made my first scopes, would have made things a good bit easier!

Best -- Terry

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