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Messages - Adam Washington

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ATM, Optics and DIY Forum / Re: Dimensions for 8" f6 reflector
« on: February 09, 2018, 09:10:36 AM »
I made just one attempt or experiment at using curved spider.
One recommendention I remember from ''Gleanigs for ATM'' articles by Cox in ''Sky&Telescope'' is to keep the thickness of the arms at 1/50 of primary mirror diameter.
In my experiment that mean a tickness of 1.44mm so I made the blades 1.5mm thick.
What I obtained is something I don't like : the light from the spikes is spread across the whole visual field like the haze produced by the spherical abberation of a not parabolized mirror.

 bbcodeImage-js (do not remove or edit this tag)
Before , the secondary was hold by a 4mm thick arm made from a piece of welding electrode.
I'm seriously considering to go back to the one arm : it produced one spike but it was dim and it disturbed me less than the ''haze'' I reported.

Ziridava


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Perseus double cluster
Pleiades
Andromeda
fav EP for this 17mm Nagler type4
Frames things nicely And all-round good preformer
35-Pan was cool in darksky setting

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I have several of the Meade Series 4000 Plossls, and they were my only eyepieces for many years. I never felt I had anything to complain about. As someone who is just getting started in astronomy, I think you are wise to try to start out simply, conserve your budget, learn about your telescope and the sky. There will be plenty of time in the future to upgrade if you wish.

Astronomics, the company that hosts the Cloudy Nights forum, has Meade and Celestron Plossls at very affordable prices. FWIW, mine are the 9.7mm, 26mm, 40mm, and an 18mm wide field, which give a pretty nice range. I do have a Barlow, but I just personally don't use it much. On the Astronomics site, if you're looking at eyepieces and you click on the tab "Tech Details," it will give you info such as eye relief, if that is a concern due to the eyeglasses.

Many people like the zooms, and I just recently bought one myself, but if you've never seen one before, be forewarned, they are gigantic, at least the one I got is. I've only had a chance to use it a couple times, and it seems very nice, but it's going to take some getting used to.

I totally understand your brain burn-out. It can be paralyzing. I know it's easier said than done, but try not to over-think it. A few Plossls will get you started very nicely.

I found a Meade Series 4000 8-24mm zoom for $70. Would that plus a 2x Barlow be a good starter set?

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With the right low-profile focuser, I can easily see how someone can get well under a 25% C.O. for an 8" f/5-ish scope......if they don't use a Paracorr.  Once that gets thrown in, the diagonal-to-focal-plane distance must increase to accommodate the offset between the Paracorr lens and the optimal focal plane position for the eyepiece.Clear Skies,Phil

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Mounts Questions & Expirience / Re: Defective Celestron AVX Mount
« on: February 08, 2018, 07:31:56 PM »
"As for the rest of the mount, mine is working great. It would be even better if there wasn't an idiot at the controls."



But we Idjits can learnt to run our mounts.
But we kan't fix stupid from the faktory.

I do hope the lucky ones stay lucky and happy!

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Who looks at a weather site for backyard observing?
We're only talking about taking trips to an observing site far from home.
There would be nothing worse than driving two hours to get to a site to discover it isn't clear, or worse, because you'd unload everything,
it's clear for 2 hours and then cloudy.


While most of my checks involve planning for away from home observing, sometimes it can impact what I choose to do that evening even if at home (e.g. when the moon is up!) If the forecast is clear but windy, then I'm not going to consider taking the time to set up the big Dob in the backyard...or even the medium Dob. If it turns out still/slight breeze and the seeing ends up being decent then I have missed an opportunity.

And if it is supposed to be partly cloudy or overcast then I'm going to plan something else for the evening rather than try to catch sucker holes. Of course this assumes I believe the forecasts...and sometimes I take a look at the sky and what is in the next day's forecast and decide it will be clear or cloudy counter to the forecast. I getthe majorityof those calls right. The trickiest ones are the transitions occurring near sunset, where the forecasts are assuming a big change. The forecaststend to get these bass ackwards with the "cloudy" night being clear, and the "clear" night being cloudy.The models don't account for atmosphericinertia and continuing trends all that well.

The worst is as you say, carrying gear out to a dark site, setting up, then having clouds roll in. Had that repeatedly in early winter this year. Between driving, packing, loading/unloading, setting up etc. I've got at least 4 hours tied up in it. When I only get an hour of real observing in I am not happy.

When it comes to seeing forecasts though, backyard observing is the primary reason to check. Windy is nearly always poor/very poor/oh-my-god-it-is-awfulseeing. In other places I have lived, the other major factor was overhead Jetstream speeds. Here...I don't know.The disturbance from the coastal range across the valley, or the layer in the valley,highnight/day deltaT/low humidity,or the diurnal impact of the slope of the Sierra range nearby seem to keep the seeing consistentlychurned more than anywhere else I have lived...by a long shot.

Another posted the following:
<p class="citation">QuoteI'm going to stick up for the Clear Sky Chart, too. I have a CSC for my observatory and because I sponsor it I get priority on updates over non-sponsored CSC's. Yesterday, my noon CSC forecast clouds all night (in agreement with the NWS) but when it was updated at 11:00 PM, it showed clear skies from 1:00 AM to 8:00 AM. And that's exactly what happened. [/quote]

Unfortunately this is a good example of a completely useless "forecast." An update at 11 PM for 1 to 8 AM doesn't allow any planning.If I am already observing at 11 PM then I will continue regardless ofany forecast because I won't need it anyway. If the update was at 3 PM or even 5 PM it had some value. But at 11PM I can tell what is going to happen in 2 hours nine times out of ten. I don't need any updates, nor will I even see them. The decision about whether or not to go to the dark site is made before sunset. An update at 11 PM telling me it will be clear from 1 AM on is far too late to have any value on the critical decision.

If a forecast is wrong when I am packing the vehicle to leave, or prevents me from packing the vehicle to leave, then it is wrong the whole night. Doesn't matter if it is updated and100% correct an hour later. It was 100% wrong when it mattered. The decision has already been made, based on the forecast and/or my own read of what the weather is likely to do that night...which has a better track record.

And this is why I never try to go to the dark site after 10PM or so. The likelihood of haze over, fog, or cloud in the AM is usually greater here and the ability to forecast it is even less. When most of the sessions in a season are shutdown by haze over in the AM (or earlier), trying to catch an observing window only in the AM is a really low probability play. The only time I specifically set up in the morning is when I am trying to catch an event in the backyard.

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Beginners Forum / Re: Alternatives to Orion StarBlast 4.5 reflector?
« on: February 04, 2018, 12:50:07 PM »
I'm in the process of configuring a StarBlast for a neighbor with a couple of grade-schoolers. I found a stout little patio table for $15 that works great! I'm also keeping my eye open for a 3-legged stool to use as a base. I had it out last night for a star-hop around Lyra. Wonderful little scope.

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ATM, Optics and DIY Forum / Re: Photo setup to support testing
« on: February 04, 2018, 11:33:59 AM »
It makes straight lines appear bowed. You may be looking at a null thinking you're either over or undercorrected. Also if you have bowed lines you can't tell what is real and what may be an artifact of the lens.

Mladen

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General Astronomy & Observing / Re: Why so many telescopes?
« on: February 03, 2018, 12:56:40 PM »
Heh, heh, wellll, before I bought my first scope I built 24 of 'em with mirrors from 4.25" to 16.5". I have no idea how many I presently own, but it always seems to be one shy of too many.

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Reflectors Telescopes Forum / Re: Newton 10" f5 vs SCT 10" f8
« on: February 02, 2018, 04:29:02 PM »
I have a couple of homebuilt 10" Newtonians; an f/6.7 and an f/5.6. I also have a 10" f/4 Schmidt-Newtonian. For comparison I have a couple of deforked 10" SCTs that I use on a GEM, a classic f/10 and a wide field f/6.3 (native). I also have a 10" f/10 SCT still on its forks. The Newtonians are lightweight, simple, and very easy to use, but for purely visual I love how compact and comfortable the SCTs are. For something quick I'll usually break out one of my Newtonians, but if I'm going to settle in for a relaxing evening of star-hopping I'll opt for one of the SCTs, and more often than not the one that is still on its forks (which is why it ended up back on its forks).

It is nice to have options.

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Light Pollution Topics / Re: This is not good
« on: February 02, 2018, 02:26:14 PM »
I think one of the big questions about LEDs is going to be, are they kept shielded and pointed down, or simply splattered all over the place like current lighting.Someone posted a link that showed pictures of Los Angeles before and after LED lights were installed. If what is shown in the pictures is accurate, then LED lights will be an improvement for light pollution. If the pictures are not accurate, then there really is a dilemma.

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if blowing the back of the mirror would be sufficient
its always best to have an envelope of moving air surrounding all of the surfaces.

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General Astronomy & Observing / Re: Anybody remember Jack Horkeimer?
« on: January 31, 2018, 11:27:39 AM »
I remember Jack Horkeimer before sign off. Always fun to watch.

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ATM, Optics and DIY Forum / Re: Combinations of Telescope design.
« on: January 31, 2018, 11:11:38 AM »
The name was Clyde Bone, who displayed his Mersenne telescope at the Texas Star Party.

I have built two telescopes combining a refractor with a Newtonian. The purpose is to eliminate the ladder when using a large Newtonian. In place of the usual Newtonian eyepiece, the light hits another diagonal mirror which directs it downward outside the tube. Then it passes through a positive lens to make the light rays parallel. At the bottom is a small refractor that re-focuses the light. In effect it's a two-stage telescope. I call the device a periscope and it really works!

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