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Messages - turtnaneade

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1
I would just want to be somewhere in the san juan mountains. I love that range of mountains. I've seen a video of the train ride, and it looks great. Im also very active in action sports, and Durango offers a lot of different recreation. I can eventually adapt to the cold. I've looked at pagosa springs which is and hour east of Durango, but it's a bit to small. Utah is more of a desert state than a mountain state. Wyoming, and Montanais just to cold. Some of my family just moved up to Billings, Montana, and they have snow up to their waste. And, to be honest I want to be close to all the good starparties in the west. I also cant be to far from home either. That's why I think Durango is in the perfect location.

2
Mounts Questions & Expirience / Re: Issues with Losmandy Titan
« on: February 08, 2018, 07:28:22 PM »
Why not wait until the battery arrives, then install and then retest. Low batteries can cause all kinds of issues.

3
Yeah. I think I'm going to save the lazy Susan and try to find some laminate. Wife brought home a few samples. Thought about calling wilsonart and request several sample if I knew what to ask for.

4
I have finally retired this wonderful scope in the background. Aircraft struts on the secondary, titanium sheet on the secondary, roller coaster wheels for altitude bearings, 6" tapered roller bearing for the az, guts from a surface placement machine for a rocker box. Wonderful project for my brother and I. We actually made two of them, everything but the optics and focuser from scrap.

5
Eyepieces Questions & Recommendations / Re: Sterling Plossl 30mm
« on: February 04, 2018, 01:25:05 PM »
Quote
I have a few; the 12.5, the 6, and the 4. They seem pretty good, although I don't find them to be noticeably better than other decent plossls.


All Plossls are fairly similar. Just not much one can do when keeping the base design. The 5-element varietals, like the Ultrascopics and Ultimas or even the Meade 4000 5-elements, are good as well, especially in the longer focal lengths or 20mm and longer. But shorter than that and not so hot IMO, especially with image brightness and sharpness as always seemed veiled to me, compared to say a typical-good Abbe. The Sterlings are of course distinctive in their larger AFOV and better corrected off-axis within the 50 degree boundary due to the concave design. As far as the 30mm, it puts up a much better view than generic 30mm Plossls or the Ultrascopic. Ergonomics of the 2" sizing also very nice. Cool thing about it too is that it's field stop is about 27mm so works without vignetting if you use a 2" to 1.25" step down adapter. Hope to one day get a custom barrel on mine so it is permanently 1.25" format. It's a great performer with good, clean, bright, and sharp views with a strong build. About as good as a Plossl can get...and that is the beauty of it as the price is very reasonable and even premiums have nothing they can really tout comparatively. But in the end, it is a Plossl and it reaches about as far as the design can be taken.

6
Light Pollution Topics / Re: This is not good
« on: February 04, 2018, 11:58:51 AM »
Quote
All lights pointed down, lighting only the roadway. You can't see the lights themselves until you approach them. No blaring ugly yellow light bleeding into the adjoining neighborhoods ... If this is our future for lighting, using the same style or type of fixtures,  then for now I'm all for it...
+1

7
Why do vendors/dealers sell telescopes with a mediocre mount and tripod. Buyers should be given an ota only option. Without an ota option, buyers are forced to buy used. Buying used is a risk, that a lot of people don't want to take. Thanks to you all.

8
Beginners Forum / Re: Realistic Expectations?
« on: February 03, 2018, 06:22:00 AM »
Quote
Hello Everyone,

I am a Newbie in every sense of the word. In fact, at this point,I'm not even sure about what questions to be asking. So let's start with this. What can I expect to see from a $600 telescope? I have my choices narrowed down to a Celestron 5 se or an Orion Starblast 6i. Both have pros and cons and I'll be asking about them in another post. Having never even looked through a telescope that cost more then $80 I'm not sure what to expect.

Assuming I have a clear night and a reasonably dark site, will I be able to see the rings of Saturn in detail or will I just be able to tell that Saturn has a ring? Will I be able to see a spiral galaxy or will it look like a fuzzy cluster of stars? Great red spot on Jupiter?

I am eager to see anything really. I have been curious about Astronomy for a long time and am diving in regardless of what your answers may be. I am also hoping my 11 yr old son joins me in this, as he has expressed interest on more than one occasion. I have an App on my phone and we go outside sometimes and try to pick things out, which has been fun.

Thanks for participating in sucha great site. I have learned so much fromlooking around on Cloudy Nights.


From the original post ^^^^^ ...... This^^^^^^^^

It has been my observation that amateur astronomy has something for everybody.... from the very basic to the very technical... and Cloudy Nights covers them all... sometimes you may need to dig down to find the diamond, but it's there....

You may carry on now...

Still searching for... and finding... diamonds....

CB

9
Mounts Questions & Expirience / Re: FL-EXOS2GT
« on: February 03, 2018, 05:47:47 AM »
←  Mounts
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Breeder eos 2 equatorial goto mount
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Ebrown1963's PhotoEbrown1963
Yesterday, 11:08 PM
I'm having a problem slewing the scope and getting a loop problem. I do polar alignment and select Sirius for one star alignment.
The scope moves close to Sirius and I must complete alignment by centering star. As I get close to centering, the motor on declination mostly, will go back in forth very small movements each directions.
This will continue until I stop alignment process. I called Edmund Scientific and they suspected the hand control. So they sent another one to me and same problem.
Now they sent me a replacement mount head, that they said was tested and new controller.
Still have the same problem where it will loop back and forth. I did everything, latitude adjust, level tripod, proper location, date time and aligned to Polaris.
Has anyone heard of this problem?
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jdjetson's Photojdjetson
Yesterday, 11:24 PM
Check out this thread in "mounts"
FL-EXOS2GT
lots of information you may find helpful
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10
Beginners Forum / Re: Image size based on aperture
« on: February 02, 2018, 11:55:54 PM »
"I have seen several posts where the poster states that image size is somehow related to aperture and I don't understand this. Let me share my understanding and you tell me where I have gone wrong."

Your first question had to do with aperature and image size. Then you gave two examples of scopes.
Aperature just like in cameras DOES affect image size AND wide angle.
The term aperature can combine the ratio lens/mirror diameter to focal length (f) ratio OR it can just refer to lens/mirror diameter ie: 80mm lens, 10inch mirror.
Just like in a camera, a "fast" lens will be bigger in diameter and will have a shorter focal length and be wider angle. Same applies to telescope optics.
However, in telescopes, refractors seldom are "fast" ie: (f) ratio less than (f 8) whereas reflectors are often "fast" ie: (f) ratios often down to (f 4).

Your question about image size refers to which:
1) actual size of an observable image magnification OR
2) size of viewable amount of sky (width of view) measured in degrees.

1) image size is affected by magnification ie: focal length of lens/mirror and eyepiece used 4mm to 40mm
2) image width (wide angle) is affected by (f) ratio F4 to F15 of lens/mirror and viewing angle of eyepiece 42 degrees to 100 degrees.

Todays large 16" diameter Dobsonian scopes referred to as light buckets means that the scope has a huge mirror which gathers huge amounts of light with a short focal length of about F4 and can "see" a wide angle of sky.

Todays 80mm Dia. by 400mm FL refractors may have a F8 to F12 lens which can't gather near as much light as the huge reflector but may have near the same useful magnification 200X but won't have the wide angle view of the sky.

Theoretically those 16" light buckets have a wider field of view compared to refractors.
The actual image size has everything to do with, focal length of lens or mirror and the eyepiece, with or without a barlow lens.

11
Mounts Questions & Expirience / Re: AVX belt drive mod
« on: February 02, 2018, 10:58:32 PM »
Quote
I took a chance and did exactly that and it worked perfectly. Thanks again for the post Apollo.
Quote

Thanks for posting that Apollo!
i really appreciate it.
So just to clarify, I should switch the pink with the purple and the blue with the red but leave the green and yellow alone. Correct?
i assume it would be the same for both RA and Dec. right?

Dan

What are your impressions with the belt drive?

12
Eyepieces Questions & Recommendations / Re: Paragon 40mm
« on: February 02, 2018, 10:55:27 PM »
Magnus,
Maxvision is saidto berebranded Meade SWA and UWA, APM and ES Europe in Germany have some of them in stock.
Is there a 18mm ES 68? I've only seen 16/20/24 in 1.25" size.

13
I compared my Meade 9.7mm MIJ Plossl with my Pentax xw10mm on Jupiter last night and it held up well in regards to sharpness and contrast, not up to the Pentax standard but not far behind. Where it falls behind is in eye relief, my eye lashes were brushing the housing which was annoying and lens flaring on bright objects. But over all very good considering this eyepiece was only one quarter of the price of the Pentax.

14
Sag is an issue but a much worse issue is torsional stiffness. For imaging, this tube (we are talking a single tube here I think??) needs to deflect less than one arc second as a result of any sort of disturbance, because that deflection is immediately seen as tracking error (as oscillation or guide errors in the ra axis). For a hollow tube, the torsional stiffness is going to increase with the cube of the diameter. I agree with the concept of the posters above to make it a box structure with closed (shear loaded) sides. Tapering helps to 'de-tune' the frequencies that it can vibrate at. A straight tube makes an excellent torsional spring. You might get away with 8" square section tube 1/4" wall thickness. "If my calculations are correct" an 8" steel pipe 1/4" wall thickness and 2m long will deflect about 0.8 arc seconds with a disturbing moment of 2 N-m, but a 6" tube will deflect about 2 arc seconds. 2 newton-meters is a 2 newton force (about the same as 6 oz of weight) of load at a radial distance of 1m, such as from a wind gust. So I would take the 8" x 1/4" structural steel tube as about a minimum and square would be better and probably more convenient than round. A500 HSS structural steel comes in sizes like this I think and you might be able to find a "short" from a dealer at a reasonable price.

Then the next part is to calculate the resonant frequency with the mass and moments of inertia of the various 'scopes and their counterweights attached. Once you know the torsional stiffness (from above) you can just use the mass and radius to then calculate the resonant frequency in torsion and you want to keep that up well above 10Hz or so I am told.

Then again I'm an electrical engineer. I only dabble in things mechanical.

What sort of drive mechanism is going to run this beastie? I am not really clear in my mind on the mechanical arrangement.

15
Reflectors Telescopes Forum / Re: Scope for visual
« on: January 31, 2018, 09:49:55 AM »
Quote
I've decided to hold off on spending $$$ (I was thinking of buying one of the new TS 130mm f/7 FPL53 triplets some time back).

So I've been converting my 8" f/4 imaging newtonian into a dob. So far so good... pretty large secondary so at low power there's a huge blob.

It currently has the stock GSO mirror, if I replace the mirror with a Royce and the secondary with a smaller Protostar, will it be meaningfully better than say a SW 120ED? a used SW 120ED is about $1000-$1100 which is the same amount of cash out if I got a Royce.

I know there's the whole obstructed vs un-obstructed but there's a big difference between 4.7" and 8" (and yes I do have a Paracorr).

There is more than just the contrast on the target to consider.  The eye's contrast sensitivity is aided by the image brightness and for high power planetary observing, you want the image to be bright enough to avoid using very small exit pupils.

Neither of these scopes would (in my opinion) be ideal for a high resolution planetary telescope.

The 120ED does not have enough aperture to be used at high powers, and the f/4 telescope would not be ideal either because you start to run into problems when you try to make the secondary very small.

If you want a truly exceptional planetary scope, look elsewhere.

I would recommend that you invest in a Craigslist 10" dob and put a high Sthrel mirror in it. No smaller scope at 10 times the price will do as well.

I learned this from Roland Christen. I had complained about the very long wait for a 155EDF.
Roland asked me why I wanted a 1555 EDF and I said for planets.

Roland said that if I was not going to image, then I would do better with a 10" Newt with custom mirrors.

I think he was right. Having since owned a 6" Astro-Physics Apo and a variety of larger dobs with high quality mirrors, I would say that it is no contest.

For planets, it is all about the clear aperture of the scope, the quality of the optics, and seeing.

All money spent should be focused on getting the best possible telescope for the task, and for seeing more detail on planets, it will be impossible for most people to afford something that will give better views than a highly optimized 8" or 10" reflector, and considering you can get a custom mirror in a cheap OTA for $1200, in my own mind, it would be a mis-direction to do anything else.

Don't spend money on fancy eyepieces or fancy secondary (Curved vane) spiders or anything else.

Put 100% of the money you would spend on these diversions towards the telescope. For planetary it is all about the clear aperture, optical quality, and seeing.

Anyone that has ever looked at Mars though a 10" Portaball with Zambuto optics with a 6" Apo next to it will tell you that it is hard to beat a high quality 10" mirror on planets.

Anyway, I would not be spending the money on a Royce mirror for your current scope when for the same money, you could get a new 8" f/6 mirror and slap it in any old junk Newt tube and have a much better planetary scope, or reach a little and go to a 10" premium mirror in a cheap CL Newt and blow your mind.

I have used Apos up to 6" and none have bested the 10" Zambuto mirror on planets.

It is silly cheap (in comparison to an Apo) to build a fantastic planetary scope using an old dob and custom mirror. Don't get diverted by anything else if getting the best possible views of planets.

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