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Messages - James Gruber

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Light Pollution Topics / Re: LP Map (new to us)
« on: February 08, 2018, 09:49:06 PM »
Hootie Hoo! I have a public access black zone 15 miles away! Even in the backyard I'm only gray and see 6+ mag skies. I'll count myself as fortunate. On the Dark Sky Finder the same sites are yellow and green.

Reflectors Telescopes Forum / Re: Springs vs. Knobs
« on: February 08, 2018, 05:33:52 PM »

It really shouldn't be necessary to adjust the tension. If the bearings are clean the altitude axis tracks nicely.

In general, with most any Dob, it's the azimuth axis that can be a problem. A while back, I discovered that applying good old fashioned bar soap to the azimuth laminate is a game changer. The action is smooth and without the stiction that causes jerkiness and overshoot. Last night the seeing was very good. I was using my 10 inch, Saturn was crisp and clean at 411x, I was using 575x and 821x on a couple of double stars. When a scope can be tracked manually at those magnifications, you don't have to ask questions, you know it's plenty good.

As far as the GSO finder goes, it should fit the Orion dovetail but there is some variation in the various dovetails, a little filing maybe needed. They spec the GSO finder at 5.4 degrees, the Orion is spec'd at 5 degrees. That's not a lot of difference. I have both finders, I think the Orion has slightly better optics but either one is fine. In your situation, I buy a used finder, I see them for around $50..


Eyepieces Questions & Recommendations / Re: What's This Eyepiece
« on: February 08, 2018, 12:34:10 AM »
Thanks WRose for your very informative response.
You are right Starman 1. Some Plossl are not Plossl, some Plossl are named Orthoscopic, some Erfle are named Plossl...
Orthoscopic is a generic name for an eyepiece that give straight lines. Any design can give that when you limit the FOV.

ATM, Optics and DIY Forum / Re: new PLOP user guide by Martin Lewis
« on: February 03, 2018, 01:04:08 PM »
Hi Guys,
The link to the PLOP users guide may not work after some revamping of my website so here is a new link; http://www.skyinspec.../#!/use-of-plop


Hey, Martin (or any PLOP user) -- Two detailed questions:

1) What are PLOP's units for Young's modulus (i.e. elastic modulus) of the glass?

For example, Schott gives Young’s modulus of Zerodur as 90.3 GPa. This value converts as follows (unless I'm making stupid mistakes):
9.03 X 10^10 N/m^2 (Pa)
9.03 X 10^4 N/mm^2 (MPa)
9.03 X 10^11 dyne/cm^2
9.21 X 10^5 kgf/cm^2
9.21 X 10^6 gf/mm^2
PLOP, in contrast, gives this parameter as "9100." What units are these and how is the conversion making sense?

2) What coordinate system does PLOP use for positions (i.e., {X,Y}) and angles (i.e., {r,theta}) in which the part locations (triangle corners, etc.) are specified?

One might guess the usual rectilinear and polar coordinate systems, but this does not appear to be correct, especially regarding the origin and positive direction of theta.

Thanks much for any clarification on these matters. -- jclarkw

Beginners Forum / Re: Celestron Firstscope Newtonian
« on: February 03, 2018, 11:38:15 AM »
Congratulations on getting new eyepieces. They will serve you well.

That is great news about joining the local Astronomy club. That is the best thing you can do to get hands on help in showing you how to collimate your scope and to get the most out of the scope and eyepieces you have now

Most club members are very happy to help, especially a newbie, so don't be afraid to ask for help

Don't forget that you have a virtual club here on these forums as well to help and learn

I need my space.

I was looking at this too, I recommend you call or email Kris Park at DragonPlate. He is quite helpful.

He told me that the uni/twill roll wrapped will be close in stiffness to aluminum - modulus about 8-10 msi. He told me that if I was concerned with stiffness to use the high modulus or ultra-high modulus tubes. Those run 13-17 msi (high) or 30 msi (ultra).

The Ultra's are pretty pricey (about $275 per tube) but you could probably jump down a size in OD.

Thats disappointing.

Makes me want to look at thin tube stainless steel.

Light Pollution Topics / Re: Closest dark skies to Orange County CA
« on: January 31, 2018, 12:30:06 PM »
"Your safety cannot be guaranteed" is a great warning -- applicable to every time and place on Earth or off it.

In practice, I bet that rattlesnakes are a bigger risk than cougars. And as always, road accidents are a much bigger risk than either of those.

If I am not mistaken, a mountain biker was killed by a cougar not so long ago riding somewhere in Orange County.


Beginners Forum / Re: First Telescope? - Celestron Nexstar 8 Telescope
« on: January 31, 2018, 11:19:44 AM »
Thank you, I will follow you advice.

Some links for self:

Light Pollution Topics / Re: San Jose to switch to LED streetlights!
« on: January 31, 2018, 09:19:09 AM »
LED street lights don't necessarily mean less light pollution. The city PTB may look at it as "Wow, now we can get twice the number of lumens for the same amount of power!". I agree with other posts above, if the new LED billboards I've seen are any guide, an "LED future" is going to be bright, garish, and broad spectrum.

Mount Wizard runs on python which is available on Machttps://www.python.o...nloads/mac-osx/

It works with the sky x pro

The sky x pro has a Mac version.

I see no reason why you couldn't do automated modeling using this approach.

Edit: The only thing I am not sure about is how mount wizard connects to the mount. I know there is an INDI driver for 10Micron mounts but I have not messed with it.

Eyepieces Questions & Recommendations / Re: Lumicon Oxygen III filter ?
« on: January 31, 2018, 01:38:04 AM »
Depends on the object. An O-III is never better than a UHC on M8, and a UHC is never better than an O-III on NGC2359.
But if you restricted yourself to one filter, I wouldn't make it an O-III filter. Would you?

Light Pollution Topics / Re: LP from fracking: Is the end in sight?
« on: January 30, 2018, 11:11:25 PM »
It is impossible to seperate politics from anything.
Excessive,poorly designed and placed lighting is just a visible example of bad politics reducing quality of life.

ATM, Optics and DIY Forum / Re: Sawdust as Flocking?
« on: January 26, 2018, 06:59:09 AM »
I've always thought that as a substitute for sawdust, a finely ground coffee ground powder sprinkled onto a sticky substance, and then sprayed with a dull black coating would be best.
Have you tried that?

If you try to do the pleadies in anything less than a Meade/ES SWA68, or 30mm 82deg heavy nagler wannabe, you will be disappointed by the astigmatic stars in the outer 20-30% of the field. Save up, or be patient about finding a good priced Meade 5000 SWA or 30mm 82deg older version or maybe a beat up Meade or celestron version. The 34mm Meade is probably easier to find for $100.
it is similar field stop to the 1rpd 30mm, closer to 62degs AFOV

If the AFOV of the moonfish is indeed 80º (or close to it) I think I'd be fine with astigmatic stars in the outer 20% to 30% of the FOV.

If it's AFOV turns out to be "closer to 62º" then I'd be very disappointed with an outer 20% astigmatic FOV.I foundthispost about the Moonfish:

I also have the GSO 42mm and GSO 30mm Superview 2" eyepieces. The 42mm has a field of 55 degrees, and the 30mm 65 I think. I like both and use them a lot in my f6 Dob and f7 TV85. I had calculated that the 30mm Moonfish would give the magnification of the 30SV and the True Field of the 42SV.

So I took all three out tonight with the 8" f6 Dob, and guess what- it was true! I compared the views of the Pleiades, M36, 37 and 38 in Auriga, and a couple of clusters that I hadn't viewed before and don't know the names of.

The eyepiece gave sharp views, and the edge correction was much better than I expected. It was way better than the 30mm Superview, with good starpoints out to about 85% of the field, as opposed to about 75% in the Superview. But of course the field is that much wider as well, so even better! The true field was indeed the same or slightly larger than in the 42mm Superview, and the higher magnification made the nebulosity in M45, or stars at the edge of clusters, stand out quite a bit more easily.

¿Would you say it matches your experience with the 1rpd? Since you mentioned that "it is similar field stop to the 1rpd 30mm, closer to 62degs AFOV"perhaps the 1rpd and the moonfish are not the same eyepiece after all.

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