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Posts Made By: John Holt

January 27, 2008 04:13 AM Forum: Deep Sky Observing

Bright NGC Objects this winter

Posted By John Holt
Here are a couple best of type lists:

http://www.seds.org/messier/xtra/similar/rasc-ngc.html

http://www.astronomyboy.com/saa/saa100.html


In addition, one can observe near the meridian at what ever hour out with the scope, with an atlas at hand. Those atlases with data/tables on a page right next to the charts pages work very well for bright target tours near the meridian IMHO.

February 27, 2008 10:49 AM Forum: Equipment Talk

polaris alt-az vs. giro et al

Posted By John Holt
>>>Part of me (the cheap part) looks at $450 for an alt-az rig and thinks, "I could maybe pick up a nice vixen GP here used..."--then another part (the one with the sore back) thinks "GEM? no way..."<<<



Here are some other, non-commercial alternatives:

http://www.astromart.com/forums/viewpost.asp?forum_post_id=247898&poll_id=&news_id=&page=

http://members.leapmail.net/%7Eericj/refractordobmounts.html

This one just recently shared in our beginners forum by Harry Sarber who built it:
http://homepage.ct.metrocast.net/%7Ehfs/Projects/Dobfractor/dfmount.htm

While I do not have any refractors this size, my experiences with teflon on counter top laminate with my newts leave me no doubt of how this works. Berry type refractor mounts have been around for years.

I have been using a pipe mount for a few years now, after seeing one of David Simons posts here on Astromart, and later these mounts in atm literature and on the web. It is pretty amazing how something so simple and screwy can work so well. Originally one would lap the threads to smooth out the movement. But it's possible to simply match parts at the hardware store for smooth fit, and then just add a wrap of teflon tape. As needed. You can pick up a roll for a buck or so and toss it in the astro kit.

March 7, 2008 05:28 PM Forum: Reflectors

12" Lightbridge & Pararcorr

Posted By John Holt
Scott Anderson said:

Hey,

Would there be a big diffrence using a Pararcoor on a 12" LightBridge, visual use only?

Thanks as always,

Scott


Look through someones' scope of close or equal focal ratio, with and without their Paracorr. The difference is there to be seen. Then decide.

March 16, 2008 02:25 AM Forum: Beginning Astronomy?

Easy to use Star Maps for Beginners

Posted By John Holt
Seasonal Star Charts are still my favorite for beginers.

Bright Star Atlas a close second.

March 16, 2008 02:34 AM Forum: Telescope Making

The Long Road To My First Light (thank you!)

Posted By John Holt
Good reading, very cool scope.
Good going sir! Thankyou for sharing.

March 16, 2008 02:56 AM Forum: Solar System Observing

The moons of Jupiter and Saturn

Posted By John Holt
Enrique Barrio said:

Mars can be a frustrating planet to observe. It is small and distant, and the local dust storms can mask most of the surface features, leaving only a subtile hint of detail in most small scopes. But, even so, you can begin to see the disk of the planet with even a pair of astronomical binoculars; which is to say at 20-30x.

Understandably, the Jovian system is about 3 times as far from us, and even its largest moons are but 2/3 the size of Mars. But, 30x300%x3/2=135x, and even on a calm clear day when I can crank my 8 and 10 inch scopes up to around 500x the moons resolve to mere star-like points of light. Is it possible to resolve the moons around these systems a bit more clearly; and, if so, what does it actually take to get to resolve to at least a nice round disk for these objects?


Hmmm...
It seems to me they should reveal as disc's already. Cooling, collimation, atmospheric seeing and the eye's own astigmatism are things to take countermeasures for. But Jove's largest should show diameter, albeit small.

March 22, 2008 09:48 PM Forum: Telescope Making

kydex

Posted By John Holt
bill west said:

anybody know what distributor will sell me a sheet of kydex. I live in south jersey. Even a 1/4 sheet would do 2x4. I'm making a truss scope and I would rather use kydex because of the weight and durability.


http://www.meridiantelescopes.com/ebonystar.htm

April 1, 2008 10:18 AM Forum: Equipment Talk

Starblast 6

Posted By John Holt
I have 6" f/5 for a grab-n-go, with a 1.25" focuser. It has replaced my 4" f/4 for that purpose.

Some experiences:
The 6 yields a 2* field in view.
6" vs 4"...is clearly a significant advantage in resolution. On any target.
Table top scopes are really, really limited by their mount. Not a good way to go.
F/5 is friendlier on the field of view than f/4, and f/4.5 focal ratios.
A 6 will benefit significantly from active cooling.
A 6 will benefit even more from a good, stable, free standing mount.
One can barlow the 6 up to 200x pretty easily, with decent results.
6" f/5 newt ota's come up fairly often in the classifieds here. They are not too heavy, and have a short moment arm. They are easy to mount on an alt-az tripod.

April 6, 2008 08:34 PM Forum: Beginning Astronomy?

Mystery Object?

Posted By John Holt
http://www.astropix.com/HTML/C_SPRING/BIGDIP.HTM

April 10, 2008 04:18 PM Forum: Eyepieces

GSO-Guan Sheng Optics

Posted By John Holt
http://www.gs-telescope.com/#

It is my experience that their plossls work well. Their wide fields will be best suited for slower focal ratios.

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