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Messages - renjaysunsdis

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1
Beginners Forum / Re: An update to Burnham's? Whaddaya say?
« on: February 09, 2018, 10:46:32 AM »
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Although his work is somewhat dated, and as noted, behind the times regarding type fonts and photography, I still enjoy using Burnham's, because it is a classic, and because it still is a very useful work.

Since I expect the photography was state of the art when it was printed, I value the comparison with the photos I make in my own backyard with a 4" scope and a DSLR.

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Reflectors Telescopes Forum / Re: A visit with John Pratte
« on: February 09, 2018, 04:38:44 AM »
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Danny, John Pratte has been an optician for about 50 years along with being a professionalengineer, World Champion factory-sponsoredNHRArace car builder (in his spare time while being a full-time engineer), telescope maker, etc. He recently completed a 20" mirror that I think was about a 1/15 wave IIRC. He said he has no problems making mirrors without turned edges. He and his longtime optician buddy Dick Wessling of Cincinnati have produced many mirrors in their lifetimes. Sadly, Dick passed away some years ago. I had an 18" f/4.5 Wesslingthat was aspectacular performer. John, just recently got a special flat and will be doing some null testing in his own lab. John would be too modest to share all of his skills in a public forum. He also happens to be a very, very nice person in real life and I am honored to be called his friend.
This is a great thread... My friend John B. knew Dick Wessling well and purchased one of Dick's personal telescopes from his wife, after his passing.  Its yellow, as were many of Dick's telescopes.

I finally got my first look at a John Pratte/Mike Lockwood big aperture telescope earlier in the Summer at Cherry Springs. What a fantastic coupling of great optics with a wonderful structure.

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I have the very same "issue" since I acquired the Leica zoom. I'm using it for close to 90% of my viewing. But every time I pick up the ES 14/100, once I have enjoyed the view, the next thought is; "there's no way I'm selling this thing"!

Having said that, I have gone nights with just the Leica, a 27 pan, and the 2" Denk OCS as a barlow. Once I get to a dark site and haven't brought all the other eyepieces, I have not missed them. Much.


My dark site eyepieces are the Leica, Baader Zoom and 31 T5. I bring the other eyepieces but hardly touch them. Another reason why I did sell my ES 100's.

Mike

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I got my new 10" Dob yesterday and assembled it last night after getting the kiddos to bed. It came with a laser collimator, so I needed to collimate that before using it to line things up in the scope. I came up with a super-simple setup.
1. Drill a 2" hole in a 2x6 (I'm sure a 2x4 would work fine; I just had the 2x6 already laying around).
2. Place the lumber in a vise or build little legs on it. I like the vise because it doesn't move or slide around.
3. Place a 2" extender tube in the hole. Mine happened to fit nice and tight; but if it didn't, you could probably wrap a strip of paper or something around the tube to keep it tight in the hole.
4. Place a 1.25" adapter in the extender.
5. Place the collimator in the adapter.
6. Aim the laser at a piece of paper on a far wall (mine happened to be abut 25' away) and mark the spot. Turn the laser a quarter turn and mark the spot. Do this until you have four spots. Just be sure your parts are all flush and tight, especially each time you turn the collimator. Otherwise, accuracy will suffer.
7. Draw a spot equidistant to the four spots (I put some cross hairs on the new center spot to make it a little easier to see).
8. Adjust your collimator's screws until it's centered on the new spot.
Quick, easy, cheap, and effective!

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General Astronomy & Observing / Re: Infinite Space
« on: February 04, 2018, 01:01:52 PM »
"In the beginning there was nothing which exploded." Terry Pratchett

Just because we can have no knowledge of an epoch before the BB, we need not assume it was acausal. However, such a cause would presumably be external to this universe - which means is we are forever causally disconnected. If we choose to speculate about a trigger event, the consequences must remain consistent with what we observe.\

On the other hand, perhaps the Universe' nett energy is zero and a quantum flicker triggered the expansion of a hyperspatial region. This might release the energy that drives it onward. Is the monotonic increase in entropy related to the accelerating expansion of space? (I suspect these are essentially the same thing.)

What bugs me is its uniformity. The Copernican principle suggests that either the universe is infinite or that it is finite but unbounded. The first - which I prefer - causes me to wonder what expansion of an infinite space really means. Derek Muller touches on the idea near the end of this video. I just don't see how a single flicker can produce an instantaneously infinite effect.

The alternative has us playing an intergalactic game of Asteroids while remaining oblivious of the bubble and froth.

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Beginners Forum / Re: My first real viewing
« on: February 04, 2018, 10:54:30 AM »
The goto argument can go both ways. I started a year ago with a goto 4 inch refractor. I feel like it was instrumental it teaching me where things were and what to reasonably expect them to look like. I had started looking for objects "freehand" at first. With no luck. When I finally figured out how to use the handset and found M-57 I realized I had probably overlooked it a dozen times looking for that big beautiful ring from the pictures. (Still one of my favorites though)
By fall I was using the goto feature to try to learn "where" things were so I could find them myself the next time. (sort of my first "baby steps" toward star-hopping)
Still waiting for a clear night for first light with my new dob, but really looking forward to "hunting" with it.

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ATM, Optics and DIY Forum / Re: What tolerance describe 'smooth'
« on: February 03, 2018, 04:23:21 AM »
Sorry about my optic's hardhead Mark !

I heard about the problems whit IF that can cost 200K that can't make it up, from what can be tested in a bathroom at home for 75 bucks better.
-But what is the tolerance/describe namesin a IF tester that would show this magical ( and needed ) 'smothness' ?

Why would Aersospace/pro 2016 in high-end optics use a kind of a useless method, Very strange indeed.

Why can't amature-pro-dob-world just tell what numbers needed for max 'smotthness' etc and high output aplication ( max magX at 2000 meters vs DSO's ) straight out.

If I need help look at it, ( sort it out ) will some one help me here ?
We need samples.

Please fill in examples of testing optics so we can go over what smothness is and should be.

-I guess more than I has the question.
Need it to be a ridle ? ;-)
No shadows over Rohr but if one charge 75 Euros and a high-end Zygo test can cost 1-2.00K in US, I'll just need to ask myself , as in my experiance you always get what you pay for.

8
Beginners Forum / Re: Debating on getting new telescope!
« on: February 02, 2018, 08:19:09 PM »
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Thank you for all your replies! Made me realise perhaps portability is a bigger issue than I have imagined as I am seriously considering bringing them overseas (since Singapore's light pollution is severely problematic). Only seldom, but I guess would be an issue. I have not ruled out the prior 6 inch dobs, but now I am also considering the Skywatcher Heritage 130p. Thank to Hesiod for the suggestion! Anyone else can provide a review of the experience? Thanks so much!!!!!

Many of us have a primary scope and a travel scope. I do.  And, of course I have binoculars too.

So, if you rarely travel with the scope I would leave the travel consideration out for now. Get the scope that will serve you at home, where you will use it most of the time.  Then save up for a smaller travel scope.  Otherwise you restrict your main scope to accommodate the possible travel factor.

I don't know what is available to you but you can pick up a 100 mm table top Dobsonian for $100 in the USA.  They get good reports and are more than adequate for a travel scope.  You can put them in a carryon bag or pack them in their original box as checked luggage.  If they are lost or damaged beyond repair they represent a fairly small investment, about the price of an eyepiece. Zhumell Z100 100 mm Tabletop reflector – About 6 pounds
Includes two eyepieces and a red dot finderhttps://www.telescop...ector-telescope
Discussion and reviewhttp://www.cloudynig...m-f4-newtonian/Orion SkyScanner 100mm TableTop Reflector Telescope - 6.2 pounds
gets a lot of good reports. Includes 2 eyepieces and a finder scope.http://www.telescope...25/p/102007.uts
Videohttps://www.youtube....h?v=-BEzRibaMdshttps://www.youtube....h?v=NihZIw8f1-o
My main scope is an 8" Dobsonian - I can put it in the car for a trip to a local darker site but I would not take it on vacation nor take it on a plane. To big and inconvenient.I have an 80 mm refractor and a 127 Mak, either of which is small enough to be a vacation/travel scope. Either will fit in a carry on bag.At home the main scope is the 8". It gets about 75% of my observing.  The other 25% is divided between the two smaller scopes and binoculars.

9
To make things interesting, the 10Micron mounts use AC servos instead of the DC servos used in the inexpensive mounts. I don't know if the other premium mounts use AC or DC servos.

As far as the reliability of cheap servo motors in Chinese mounts go (the motor often being manufactured in India), I have never seen a dead motor. What I always see are dead encoders and the manufacturers do not sell those separately. I have see a few stripped teeth in the gearboxes but that is by design.

I don't have a real problem with steppers except for the fact that the mount drivers assume that a stepper has made the number of steps (or microsteps or whatever) that it has been make with no way to confirm that. It's fairly easy to make the steppers in these mounts skip at which point the system is essentially lost. Steppers with encoders would be far better but clearly more expensive and none of the manufacturers have gone that way to my knowledge. The servo motor with an encoder at least knows that the motor shaft has actually turned the number of times that it has been told to turn. Between the Atlas and the CGEM, which are essentially same mount except the motors, I consider the servo-based CGEM to be a little more smart and accurate than the stepper-based Atlas. But the difference isn't huge at this lever since there are so many other things going on that the difference between the two is generally going to be lost in the background noise.

10
General Astronomy & Observing / Re: Daylight saving ends!
« on: February 02, 2018, 05:48:16 PM »
The debate is between people who want it to get dark as early as possible so they can do astronomy and people who want it to stay light as late as possible so they can do non-astronomy things. My vote is for standard time all year round. The only thing I do outdoors in the evening is astronomy. All daylight savings accomplishes is to force me to stay up an extra hour.

11
Reflectors Telescopes Forum / Re: Using a Skywatcher goto Dob Manually?
« on: January 31, 2018, 12:50:39 PM »
Doug,

A quick question if you do not mind, why would you get a 10" skywatcher if you already have a custom build 11" Teeter scope? You already have a premium scope in the same range of what you got.

12
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I was observing 1st quarter moon yesterday in my 4" F/10 refractor using ES 8.8 mm EP.

At 113X magnification and 82 degree AFOV on the EP I was supposed to be getting TFOV 0.72 degrees which should have been plenty enough to fit the Moon. However I was surprised to see that the moon disc was almost touching the edges. I could see the whole disc with very little space left around the edges.

With 6.7mm EP I should have been getting 0.55 degrees TFOV but in that case the moon did not fit at all in the EP. I was seeing probably 80% of the disc.

Am I doing something wrong or is it the case that most EPs never really have the advertised FOV.

That should have given you 42.6' field with the 8.8mm, assuming a 1000mm focal length.
The Moon was 30.6' on June 1, leaving a space of 6' on either side.
That's a decent sized gap.
So, either ES' field stop size of 12.4mm is wrong (possible, but not that likely, as it corresponds to 81° at that focal length) or the focal length of your scope may be longer than 1000mm (likely).
The true field could be a bit smaller if we assume your scope might have a focal length of 1050mm (2.9% longer than nominal) = 12.4/1050 x 57.296 = 40.6m, leaving a space of 5' on either side.

I assume you don't wear glasses, or you could never see the entire field.

The 6.7mm has a field stop of 9.5mm = (maybe) 9.5/1050*57.296 = 31.1', still larger than the moon

ES would have to be wrong on 2 different field stop dimensions, and both correspond to a calculated 81° with no distortion.
Add even a trace of AMD (<1%), and 82° sounds rational for both eyepieces.

So IF you were actually close enough to the eyepiece to see the field stop, then your f/10 scope might be a bit longer.
However, it's unlikely to be f/11, so the longer focal length still doesn't explain what you saw. Even at f/11, you'd have had 3.7' on either side.

So, Ed's mention of pincushion distortion (large in these eyepieces) enlarging the Moon in the field seems highly likely.
In a low power one of these eyepieces, the Moon stretches radially near the edge, and if the moon nearly filled the field, it would stretch uniformly and still appear round.
To stretch 5' on each side would imply an edge distortion of 5/15.3 = 32.6% That seems high, but perhaps a combination of factors could reduce that a bit:
--focal length a bit longer than a perfect f/10
--underestimating the clearance on the side
--radial stretching by pincushion (positive rectilinear) distortion.
And all would combine to yield what you saw quite easily.
In essence, you were seeing the Moon a bit larger than its subtended size.

13
Mounts Questions & Expirience / Re: Cheap Counterweights for AP 1200
« on: January 31, 2018, 07:51:57 AM »
David, I hope your plan works. I have a couple of concerns, though. I don't think those collars are intended to support weights vertically. I think they are intended to keep plates from sliding off a barbell if the bar is tipped a bit when it's lifted. The clamp may not be "grippy" enough to hold sixty pounds on your counter weight shaft.

As Chris E. said, even slight of the counter weightsmovement would ruin an image. But, it's not like your mount will be moving quickly, so perhaps the risk here is small. If you have any concern, it might be fairly simple to drill a hole radially between two of your new weights' spokes toward the hub, tap it, and thread a set screw in there like a standard counter weight to hold it in place.

Since I didn't do this myself, I'll give you this advice: double check that the bar bell weights don't hit your mount's pier. I thought I was being really smart pouring an oversized concrete pier for my observatory until my counterweights almost hit it when I installed and polar aligned my mount. I got lucky and my weights just cleared my pier. Whew!

If everything works, patent it, then let us know.

14
ATM, Optics and DIY Forum / Re: Low profile 'Collapsible focuser'
« on: January 31, 2018, 06:02:33 AM »
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Look similar to the focuser I have on my 5".

That focuser is a beauty..!
Own design..?

Yes my own design patent no. 6,260,428 http://patft.uspto.g...8&RS=PN/6260428

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General Astronomy & Observing / Re: Winter is coming!
« on: January 31, 2018, 01:33:03 AM »
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In evil sarcastic tone (think of Igor voice), yes , yes winter for you but clear skies for me... in Guam. Muwhaha! It has been raining here since June. Everyday... it should clear up by December.
Sent from my iPhone using Tapatalk

Throw in some evil laughs from us Floridians too. Now that we’re starting to get a bit of clear weather from cold fronts, it’s time to break out the scope again.
Florida has had beautiful skies for most of the week. The forecast for next week is looking good, too. Unfortunately, for International Observe the Moon Night tonight it's.[/quote]
Florida has become a cloud... A very big cloud. Apparently, someone must have received a new scope or AP equipment.[/quote]
Agree. Somebody got nice new equipment. The Florida-covering cloud is a cold front meeting Tropical Storm Philippe. The good news is that the whole mess is supposed to move out by noon Sunday - at least for north Florida.

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