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Posts Made By: John Holt

March 13, 2010 08:39 PM Forum: Eyepieces

Eye Relief

Posted By John Holt
Any of the eyepieces built with the kinda sorta standard 20mm eye relief for eyeglasses, I've found to work well.
They're not all exactly on perhaps, but if the maker is trying for close to that, then they usually work better the those ep's with just a large eye lens.

April 5, 2010 12:08 AM Forum: Deep Sky Observing

Marking up a star atlas

Posted By John Holt
I'm not sure.
Have you seen the the BSA, with it's tables adjoining the charts?
Here's a link, were you can enlarge the pages to see what they show.

http://www.willbell.com/atlas/atlas1.htm


The Millenium Star Atlas shows primary magnitude, separation, position angle and several variable types by the symbols used for the star's, right on the pages of the charts. Very nice!



April 9, 2010 06:36 AM Forum: Reflectors

dew on primary...help

Posted By John Holt
I've gotten dew on my primary only twice when out with a scope. Each time turning on a blower on the primary and moving air around or across the mirror surface solved it.

If you are referring to dew forming on the primary after bringing the scope indoors from a cold night, then that a blow drier will work to fix that kind of dew.

April 12, 2010 04:21 PM Forum: Deep Sky Observing

Dark skies VS Aperture???

Posted By John Holt
An 8" will do very well under the darker sky.
In truth the 12" will do significantly better there. Though I realize that wasn't the question.

I often bring an 8" out to rural sky. The more remote the place the better the results of course.
When there with the 8" I frequently wish I'd brought my 13".

So for what it's worth, I'd bring the 12" to the Catskills.



June 8, 2010 01:49 AM Forum: Guns and Hunting Optics

Armed while observing at dark sites

Posted By John Holt
For personal protection against serious predatory threat it makes some sense.

Just to protect gear....never.
A judge has no reason to care about astro gear.


June 24, 2010 04:45 PM Forum: Equipment Talk

Collimation tool for Netwonian

Posted By John Holt
It seems like this gentleman could help too:

http://www.rfroyce.com/

June 27, 2010 02:47 PM Forum: Telescope Making

Who has made a mirror for binoculars?

Posted By John Holt
This gentleman's :

http://www.homebuiltastronomy.com/downbino/index.html

September 6, 2010 02:38 PM Forum: Beginning Astronomy?

Alternatives to right angle finder

Posted By John Holt
Ad a unit power finder. for basic straight down the scope pointing, to work with the right angle powered finder.
Start with an affordable red dot finder, that is light and small.
There are lots of options, they all work.
Telrads are very cool, but powered finders can be more helpful under light pollution.
Laser pointer finders are very cool, but can have battery power issues in colder weather, which is coming.
You could even make a simple peep sight or open pin sight for your scope. No battery required at all.

January 27, 2011 10:54 PM Forum: Telescope Making

University optics cell

Posted By John Holt
Mark Shelton said:

Hi,
does anyone have experience with University optics 13.1 Cell. I am thinking about getting one to make a new Dob. I have an old coulter mirror.

Mark

It is my experience that their 9 point cell with the support points in three rows of three, radially down the spokes of the mirror cell, will not support a 1" thick 13.1" mirror properly. This configuration of support points is wrong for this thin of a mirror, and yields astigmatism.

February 12, 2011 05:38 PM Forum: Eyepieces

Eyepiece Dew

Posted By John Holt
As long as they don't dew up from being brought into the warm, from the cold.

FWIW, I store the ep's at ambient, bottled and in a closed case with some small desiccant packets tossed in (with other astro stuff too).
But when at the focuser I keep them in specific eyepiece only pockets on me.
Body heat keeps them dew free, and will un-dew those that have been in the focuser long enough to dew (or frost).
I have -astro only- warm and cold weather pocketed outer wear.
Some folks use photograghers vests or fishing vests to success.

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