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Messages - reapriavoland

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I frequently read that but having recently compared the 30mm ES 82 Degree with the 31mm Nagler, it was clear to me that ES 30mm is not the eyepiece that the 31mm Nagler is. For what one pays, the ES isa good eyepiece but it certainly is not as well corrected at the 31mm Nagler in a fast scope.Jon
Jon, I never used the ES 30-82, but having recently compared extensively Ethos 21, Nag 31, Pan 41 and ES 30-100 on 175 f/8 apo, I can say the following:Ethos 21, Pan 41 and ES 30-100 are sharp to the edge, and have zero field curvature.Nagler 31 has poor edge performance, either on stars or daytime. It is never sharp even if we focus at the edge. Moreover Nag 31 has field curvature.Nagler 31 and ES 30-100 share two issues: ring of fire and abrupt magnification increase at the edge.Pan 41 has a slight vignetting at the outer 5-10%.I also found the Nagler 31 the less confortable to use of these 4 eyepieces, when trying the see the full field, looking at the center.So, the ES30-100 at the edge is much sharper than Nag31 at the edge. If we compare ES30-100 at 80 deg with Nag 31 at 80 deg, the difference is abysmal. So ES30-100 is not only 18 more degrees, it is a much better eyepiece than Nagler 31. Ethos (my favorite) is another story...Now I am talking f/6 and f/8, don't know about f/4, but at f/4 we don't need a 30mm eyepiece...Tests were done with and without a APM-Riccardi 0.75x flattener (so f/6) in straight-through mode to eliminate field curvature, taking care to not move flattener from correct focus position.Field curvature test of the 3" is not final as it was done not yet with a flattener, but by sliding the eyepiece off-axis, in a not very solid setup. In time I will test it with flattener too.I am also hoping flat field will take ES30-100 to top level, as scope field curvature is more visible on such a large field.Pedro

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Beginners Forum / Re: Light pollution filters work?
« on: February 08, 2018, 06:22:46 PM »
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I just bought a used orion-ultra block filter for viewing of nebula from my red zone neighborhood.
I have only used it on one item so far, the ring nebula, using a 10" dob and 8mm eyepiece. I did use averted vision but I was not fully dark adapted, as the skyglow around here prevents me from getting fully adapted. I have not gone the eyepatch route yet.  The neighbors think I am somewhat scary already. :-)

The filter made a subtle difference in the contrast of the ring.  Not knock your socks off difference. I assume the more expensive filters work better than the orion, but I figure I am getting 80% of the others at half the price. I don't think I would buy these new because of the high cost, and marginal gain. At least I can sell mine for about what I paid, if I grow tired of it.

In this thread thread I have seen references to moon and skyglow filter. I will try one of those next, I also would like to try a broad band filter.

My next target will be the dumbell nebula when the skies clear up and the moon is not up.

That you saw any effect at all is impressive.
1) Use the filter at large exit pupils, i.e. low powers. It's effectiveness diminishes as the power goes up.
2) Dark adapt first. Don't expect anything until you've been outside, away from lights, for at least 30 minutes.
3) Shield yourself from all local lighting. There must be no lights visible to your direct vision. Panels, tarps, blankets, even a cloth over the head.
4) Of all the nebulae in the sky, the one probably least affected by nebula filters is M57, the Ring Nebula. The filter's effects will be far more impressive on virtually
every other nebula.
5) Don't expect any results with the Moon in the sky. Wait until the Moon goes down to view nebulae.

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Beginners Forum / Re: Binos advice (first pair)
« on: February 08, 2018, 06:10:10 PM »
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Make sure to get Porro Prism binoculars. Roof prism binoculars have a narrower field of view. Also, waterproof binoculars are heavier than regular ones. All the binoculars you mentioned are good. But, I'd recommend getting a 2nd cheap beater pair of binoculars to go with them. There are some situations where your high quality binoculars could get dropped, damaged or 'borrowed' and never returned. I have a pair of Bushnell Falcon 7x35 binoculars for this reason. I paid under $25 for these brand new on Amazon. They're not perfect, but the view is much better than I expected for the price. I won't cry if these get damaged, and they will help protect my 'good' binoculars from abuse.

Narrower? not always so, a high quality roof design can have a bigger FOV that a lower porro, D

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ATM, Optics and DIY Forum / Re: Crayford style but using linear bearing
« on: February 03, 2018, 11:28:00 AM »
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Concerns about the precision causing slop or tightness... How much actual experience do you have designing, fabricating and using instruments and devices that rely on linear bearings? In my years of design, overseeing fabrication and use, as long as the tolerances are maintained, I have never experienced a sloppy linear bearing.. Generally, these are just things you buy, these are a mature technology, the R&D had been done, the tolerances are well characterized, you buy them, they work.


In the limit, rolling bearings work because of elastic deflection in the structure, in the same way your chair analogy works because the chair deforms under load, if the error in the leg length is sufficiently small.

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Light Pollution Topics / Re: *&%)#*&%$^ Streetlights
« on: February 03, 2018, 04:36:29 AM »
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<p class="citation">QuoteIn a smaller town, calling the city hall might get some reaction....in a city like Denver, what's one more streetlight.......back yard had little to no view anyways, entire lot is bordered by tall trees (the street lights tower above these though too, at least 15-20 foot higher then the streetlights they are replacing).  Oh, and I noticed they are NOT led's, looks more like a halogen bulb in them (the ones they will be replacing have that nice orangeish bright light).  Believe these will be the bluish light more focused downward......right into my back yard.

I called the Police Dept in Virginia Beach to get three different nuisance cars towed away. You may think they ignore you but believe it or not they actually listen. Just be polite and explain how the light is giving you insomnia. Also politely mention that you never requested it and you also don't want to pay taxes to light it up at night. If I can get three cars towed then you can get a light removed. They may direct you towards paperwork to fill out. It may take a month or three but have faith.

obin    [/quote]

As far as towing goes, it usually goes like this:

Dispatch informs the patrol cop in that area who (when he/she has time) checks the car out.  If it is to be towed, dispatch will call a towing company under contract with the city, who will come out and tow the car.

the owner is then responsible paying the towing company charges as well as any parking fines before the car is returned to them.  Towing a nuisance car has virtually no impact on city resources and expenses. They may even make a few bucks if a parking ticket is issued.

Quite unlike having to pay a crew to come out and remove a street light (that they have already purchased AND paid a crew to put in).

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With my 8" f/3.9I used the MPCC MKIII and had great results, never used the others so can't comment on them. If you are using the Orion flavor of the scope,I replaced my focuser pretty much on arrival.

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Beginners Forum / Re: Someone added me as a friend
« on: February 02, 2018, 06:51:00 PM »
On other forums it just means they liked something that was posted and want to follow that person because they respect their opinion and think they could learn from that person.

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Beginners Forum / Re: Help needed buying Omni XLT 150 OTA
« on: February 02, 2018, 05:30:22 PM »
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Foxtrot,

Copy and paste this link on your browser:

http://www.opticspla...cope-31057.html

I too, prefer this combo over the 6" F/8 Dobfor reasons of portability. I can pack both OTA and EQtripod in one of the excellent Orion soft carry bags slung over my shoulder to bring to a dark sky site. Not possible with the ultra heavy 6" F/8 OTA and Dob mount.

Besides, I can use the Omni CG-4 EQ mount (15 lbs. weight load capacity) for my other small/medium-sized scopes.

Wow awesome deal tnakazon, I might order this tonight.

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ATM, Optics and DIY Forum / Re: A Star Test Intepretation
« on: February 02, 2018, 02:30:38 PM »
That makes two of us, Frank!

I do remember Essential Optics and they had basic but very affordable scopes. Nothing fancy like Cave, but the price was right.

And I certainly recall John Diebel with Meade back in those days! He answered the phone and took orders himself. I think I helped keep them afloat when they first started. Nice man too. One of the best scopes I had was their 6”, f8 Newt OTA on a HD Edmund mount! That scope was nice. Best views of Jupiter I can remember and solid with a fiberglass tube and nice R&amp;P focuser.

I spent all my free time and money at the Edmund Scientific Outlet store. All kinds of surplus goodies to find there. Their 8” Newt on the super heavy mount was a monster you were in awe of seeing it in person!

I miss those days Frank

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Don't confuse rating for the ability to operate past those values. Most temperature rating only mean that is the temperature it was tested to. It may well work outside of those values but of course there is some risk.

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Reflectors Telescopes Forum / Re: Collimation/star test question
« on: January 31, 2018, 12:38:04 PM »
Thanks for all the input guys! Extremely helpful. So, lots to try next time I'm in front of the scope.

A) Make sure secondary is centered under the focuser and looks perfectly round. It sounds like this is possible with just a collimation cap but more accurate with a sight tube? These things are pretty expensive, how much difference does it make at the EP?

B) Dim the laser for better visibility when adjusting secondary tilt.

C) Remove aperture mask from laser when adjusting primary.

D) Ensure that alignment holds whether scope is pointed horizontally or at zenith.

I'm curious about "autocollimators", how do these fit with the above? Again, they are quite expensive, how much difference does it make at the EP in a 12" f/4.9?

Getting back to my OP, does any of this explain what I was seeing in the star test? Basically with a defocused star image on one side of focus there appeared to be a gross misalignment, but on the other it looked fairly good? I saw an image in a Backyard Astronomy article on star testing that showed something similar for tube currents, is it possible that was all that was going on?

I'll post an update when I have a chance to play around with the scope.Thanks again!

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Beginners Forum / Re: Is there a scope that I can REALLY see the planets?
« on: January 31, 2018, 03:43:33 AM »
When I first started I had an 80 mm refractor and was disappointed that the andromeda galaxy was just a gray smudge in the sky from my very light polluted suburban NYC sky.  And when Mars was at opposition I was using an 8" scope and still could only see hints of shadings on the best nights.

So, what limits what we see?

Transparency and Seeing - Note that atmospheric conditions, rather than your telescope, will often be the limiting factor on practical magnification and detail for any given observing session. When the atmosphere is turbulent, poor “seeing” conditions, you may find that the image breaks down too much above a certain magnification regardless of the size of your telescope. Transparency is also a factor that can be affected by humidity, air pollution and thin clouds that you may not be able to see. My 8”/203 mm often tops out around 180X due to “seeing” and transparency issues. However, under exceptional conditions I have been able to go 300X or higher.

Light Pollution - Much of what we see is based on contrast and if the sky glow is high the contrast can be low.  Planets are less sensitive to this but nebula and galaxies are very impacted by light pollution.

Ground light - If you have house and street lights all around you your eyes never fully dark adapt.  Even in the eyepiece of a telescope, what you see depends on how dark adapted your eyes are.Location of the planets - As we move around the Sun we can be closer or farther from any given planet and that has a major impact on what we see.

Mars and Neptune are about 1/3 of the way around the Sun.

Mars will be at opposition, closest point, in July but, from New York, it is going to be low in the sky so, again, I will be looking through a lot of atmosphere.

Right now, Mars and Jupiter should be visible just before sunrise but very close to the horizon. Very bad position.  The lower in the sky the more atmosphere you are looking through and the worse the image.

Venus and Saturn are on the other side of the Sun.

Mercury is relatively near but is always near the sun so you can only catch it near sunrise right now, maybe.

Uranus is in relatively good position.

https://in-the-sky.org/solarsystem.php

https://theskylive.com/When you observe the planets, their relative position to the Sun and their height in the sky makes a HUGE difference.

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Light Pollution Topics / Re: Introducing DarkSiteFinder.com
« on: January 31, 2018, 03:22:58 AM »
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<p class="citation">Quote
The Wikipedia entry for "Bortle Scale" is now fixed.

Wow, that's pretty drastic! I did add a caveat to that article, but I'm reluctant to remove information even if it's only approximately correct. [/quote]

Given John Bortle's own statements that he was *not* involved, and that there would be considerable differences between the two, and that the Bortle Dark Sky Scale is intended for use for on-site evaluation, not for use in creating maps (and your own respected expression of deep regret), it seems perfectly appropriate to me.

It's a simple matter of respecting John Bortle's wishes. I think you said it was a shame it had happened, but could not be undone. I am willing to undo it where possible; it's a small effort made to show some respect and remove some of the confusion that we see often here on CN.

If you like, we can add a short summary of the other main LP measurement systems / night sky evaluation methods there and point to Wiki pages on them. That might be even more helpful - to remove the false connection, but to show the way to additional information. There is already a question in "talk", unanswered, about the relationship between the Bortle Scale and SQM readings.

Does that sound worthwhile to develop?

Lee

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Mounts Questions & Expirience / Re: Mount overkill?
« on: January 31, 2018, 03:21:56 AM »
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A differing opinion--if you're strictly a visual guy, you can do as well with much less expensive mounts. I do assume that money is of *some* importance, otherwise you'd probably just buy new.
There's no benefit to a Mach1 for carrying such a small scope for visual. A GM8 would do you just fine (assuming you want to remain lightweight. An AZ-EQ6 would do the same thing but weigh more. Even a CGEM would be good enough.
The benefit of quality mounts is for astrophotography, where tracking steadiness is all-important. For visual, you want good GoTo's and ease of setup.
You are right,hence the post about if it is an overkill. I looked at GM8 before posting here &amp; seems like Gemini is a disaster. I just don't want to deal with that. I want something that works out of the box &amp; then every time.
I have had skywatcher mount for couple of years sold that  &amp; bought my current setup. What a joy to use &amp; setup, esp Rob Miller tripod.
I will look at CGEM though I don't know if I can use it with Rob Miller tripod.

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Reflectors Telescopes Forum / Re: Newtonian vs RC?
« on: January 31, 2018, 02:10:35 AM »
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RCs are chosen by some rather than large Newts because they're more compact. Among other things that's easier on the mount, sheer length and bulk matters. They can be hard to collimate. There's a difference between the low end RCs and the expensive premium ones in this regard. The very precise high quality mechanical components of the premium versions make a large difference. But any RC will be harder to collimate than a Newtonian or SCT.

Another advantage of the RC for imaging is generally longer backfocus, for things like off axis guiders and filter wheels.

Visual and AP of DSOs are completely different because of the "sensors". Your short exposure eyes need a lot of aperture to gather light really fast, but are forgiving of errors like tracking and aberrations. .005mm pixels gathering light for some time are extremely unforgiving. Most people who do both have different scopes for each. Generally RCs are used for imaging, Newtonians for visual.

Planetary is more like visual (short exposures), imaging DSOs is a unique thing. Long exposures change everything.

RCs have a large central obstruction which reduces contrast. An issue for visual, easily dealt with in processing for imaging DSOs. If you want to image with a Newt, you'll need a coma corrector. With an RC a field flattener can be useful.

This is not a question of which is technically "better". More a matter of personal needs and personal taste.

I was looking at the Astro-Tech Truss Tube 14" RC for about $5,800... not sure if that one is considered high quality or low-end... as you can get some RC's for $400 and others for $25,000... it seems to sit (price-wise) kind of in the middle? Although a little on the lower-side... It's hard tofind any reviews so I appreciate your comments. If it is considered a not very well made one, I'd rather buy a well-made Newtonian than a cheaply made RC...
I think the new version of the AstroTech truss RC scopes are good for the money, however a DK from Planewave or iDK from AGO would be considered top of the line.

As for newts, the TS is not what I would consider near top of the line. The ASA is considered to be up there, along with the UK orion optics AG scopes.  My AGO newt was the first production 12.5" that he made, and it turned out to be more difficult that he thought. Ended up learning a lot, we both did, after the first one had some issues. He ended up making me a completely new scope with improvements he thought was needed. The new scope is absolutely great, but cost him much more to make. He only sold about 4 of the 12" and maybe 4 of the 10" I think and had removed them from his standard product line up as they are expensive to make, and a limited market. And tricky to collimate for large chips, just like most astrographs really. I use 8300 chips that are considered small in todays standards so I do not have any problems collimating either of my scopes.

Again just my opinion, and worth that you paid

Dean
Hi, Dean.

I guess that the one from Orion UK that you are referring to is the following:

http://www.teleskop-...-corrector.html

I'm not an expert but to my mind it seems to be a high-end telescope.

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