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Messages - grafpievimel

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Reflectors Telescopes Forum / Re: Mirror substrate material
« on: February 09, 2018, 05:39:49 AM »

About what aperture do you think this becomes more important?

The thickness of the mirror is more relevant than the aperture when it comes to cooling (different sized mirrors with the same thickness will cool more similarly than you think, because the surface area to mass ratio is similar). IE - I'd be more concerned with cooling a 2" thick 12" mirror than a 1.3" thick 20" mirror.  Spend your $$ on a thin mirror and good mirror cell before you spend it on an expensive material. If you are already going with a thin mirror, and the question isjust about the material, I wouldn't spend more than a 20% premium for the quartz. I'd probably say a 10-15% premium is worth it. 
Zambuto doesn't charge extra for quartz. See his website.

Reflectors Telescopes Forum / Re: Thin mirrors - nothing to be afraid of
« on: February 09, 2018, 01:20:19 AM »
I think the main benefit of a fan is to mix and even out heat plumes on the front of a mirror. Why cool the back, when a warm mirror does not dew?
Making my base design 2", taller adds 1/2 pound. I suspect the change in fulcrum could balance everything out. A higher up fulcrum also means the tube is higher above the ground and eyepiece height changes less.

Reflectors Telescopes Forum / Re: Dobs on EQ Platforms
« on: February 04, 2018, 12:31:25 PM »
One aspect of my Equatorial platform that I did not expect is its "twitchiness". Bumping the scope while it is on the platform results lots of vibration in the scope that takes a while to settle down. Even touching the focused sets it off. In hindsight I should have expected that due to the nature of platforms.Has as anyone found a means to dampen the vibrations?
That sounds to me like primarily an issue with the scope being oversized/overweight for the platform.I have one of the cheap ones (Atomic I believe) I bought locally for $100 under my 12.5" (it is a very heavily built scope) and it is prone to exactly what you describe. The all aluminum crossbow made by Gregg Blandin that I use with my 20" exhibits none of that. There is almost no difference between with or without the Crossbow.

Eyepieces Questions & Recommendations / Re: My new 14mm ES82
« on: February 03, 2018, 12:59:46 AM »
Hmmm... so eyepieces have variable quality, just like telescope mirrors and binoculars.

Used buyers beware? The used ones I bought were very good. One guy sold him his 24mm because he saw a speck in there, which I did not see. Another sold me his Meade 8.8 because the eye relief was short. But it is not a problem at night.

ATM, Optics and DIY Forum / Re: Sawdust as Flocking?
« on: February 02, 2018, 11:33:11 PM »
My suspicion is that if sawdust were used, a relatively coarse "grit" of sawdust would be best, as it would tend to fill with paint and level less than fine sawdust.I imagine very fine sawdust would tend to lie flatter, almost like the flakes in metallic paint.I'm thinking of the wide range of particle sizes I get in my shop--from the coarsest from my hand rip saws and my coarsest bandsaw blades, to the finest dust that I get with a router or a power sander fitted with fine grit sandpaper.

I also suspect that sawdust from hardwoods would work better than from softwoods, since the chips would be less likely to crumble or lay as flat as those from fir or pine.

Does anyone have any experience to report with choices of sawdust?

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.

Not sure this is true. See the original posting for this thread (below). It doesn't say anything about trips, it is talking about observing sessions being planned based on Nothing is said about taking a trip. I can answer your question directly in that I used to plan my observing sessions based on clear dark sky predictions. I am not talking about what is happening this afternoon, I am talking about whether or not I will observe tomorrow, or next week. For this sort of predictive information, I find clear dark sky less than helpful in my area.

Part two of the answer to your question is that I used to base whether or not I was going to observe on the projected seeing conditions. Again, I am not talking about a trip, but rather whether or not it is worth setting up my scope tonight. If the prediction was for bad or poor seeing, I would rationalize and say "not worth the effort". Again, through experience I now realize that I was missing out on opportunities by basing my actions on Clear Dark Sky.

I suspect that I am not alone and that others are basing local plans on weather predictions. Obviously, the planning is not in terms of a few hours (for cloudy conditions), but rather planning for tomorrow or a couple of days from now.


So many times I've used to plan my observing sessions only to find out it was completely incorrect even looking at the site real time. There have been times that I've cancelled group observing sessions only to have great conditionsand other times where it's said it was going to be beautiful but then heading out I'm met with a sky full of clouds.

Do other have the same issues? Is there a better tool?


Jon, this has also been my experience ... completely incorrect forecasts.

Try viewing in Las Vegas, my second home town. A few years ago, we stepped out on a balcony on a hotel on the strip. We could see Jupiter--naked eye, and that was all. For visual viewing, you can try various filters, but I have found that about all one can see well are the planets, moon, some bright globulars and some double stars. You just have to get out to a dark sky site to enjoy this hobby. Mag 5+ skies will also show a lot. I have a Mag 5 sky about 22 miles from where I live. I have to drive about 90 miles from my home in San Antonio for better than Mag 6 skies. It is difficult for me to get out to the dark sites. I do not know if those new electronic eyepieces do better in light polluted skies.

Mounts Questions & Expirience / Re: TTS-160 Panther
« on: January 31, 2018, 12:40:32 PM »
Hi Tammy -
If you order the TTS-160 directly from trackthestars, Niels can accommodate many tripod top plate requests. For example, with the right adapter, the TTS 160 can be mounted on tripods/piers that employ a standard 3/8 16 stud.

The TTS works well on the Avalon Tpod tripods for example.


ATM, Optics and DIY Forum / Re: Secondary holder design
« on: January 31, 2018, 05:29:06 AM »
That's alright, maybe he will chime in.

Mounts Questions & Expirience / Re: Losmandy G11 Gemini 2 and Stellarium
« on: January 31, 2018, 04:20:32 AM »
You can even use a straight cat5/6 cable from your laptop the G2, that's what I do. It works as long as you have a laptop that is not too old. Not sure how old is too old though

Reflectors Telescopes Forum / Re: Why no 7" f/5 Newtonian?
« on: January 31, 2018, 03:36:54 AM »
"So where can I get a 7" f/5?" One way is to look (hard) for a very early Starmaster by Rick Singmaster but be prepared to pay more than you expect as they are very collectable. Its the model before the oak classics. Not sure how many were made. And NO, ours is not for sale ! Thanks. *BW*

Mounts Questions & Expirience / Re: Smallest, Lightest imaging mount...
« on: January 31, 2018, 02:26:09 AM »


The CEM25EC is a thought, if you absolutely must go unguided. At a price, of course.

There's relatively little experience I've seen with that mount.

The CEM25 looks really attractive. I am never going down the aperture fever rabbit hole, ever again. I want light, small, simple.

This reminds me of my bass playing days and the debates over bass cab design. Light, low or loud. Pick any two...but you can't have all three. I want all three in a mount. Light. Small. Stable. And I want it for some easy, simple AP work.

It's always about compromises. The one thing I'm willing to compromise on is not being able to image everything out there. If I'm stuck with fewer objects, oh well. This is for my amusement and enjoyment. If all I can image is the moon, planets and brighter DSO's only, I'm totally fine with that.

That almost sounded blasphemous.
What kind of set up will you be going to for planets? I would figure Lunar, Solar and larger DSO's...
Ooh, yes. The sun too. I forgot to mention that. Small aperture also saves on the cost of solar filters. Probably afocal or at least a Barlow with a video cam for planets. Although imaging the planets are the least of my interests.

And just for the record, most of my AP efforts are more to share with my non-equipped friends. As in, hey..."I was looking at this last night", or "Remember we were looking at this and it didn't look like much? Look at this photo of it."

Has anyone actually measured the field curvature in the ES 34mm?

This system is similar to an optically compensated zoom lens. One group has positive power, and one has negative power. The third group is positive and is mainly spaced to re-collimate the beam. The negative group can possibly be out of a Barlow. You just have to know the EFL's of each of these SS lenses, and model them as perfect lenses in OSLO to approximate the spacings. You also have to experiment with which way the lenses are oriented, as the SA from each group is a strong function of orientation.

Beginners Forum / Re: Star Party Dos and Don'ts
« on: January 31, 2018, 01:05:13 AM »
Do bring an umbrella cause most likely it will rain (or at least the ones I plan to attend)
However the weather for BFSP should be clear because I cannot make it this year.

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