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Posts Made By: John Holt

October 30, 2005 10:33 PM Forum: Equipment Talk

Finderscopes

Posted By John Holt
"Hi everyone, Is there available a straight through finderscope with a corrected image. about 9x50.Cheers, John"

==========================

One option is the 1/2 binocular finder.

November 13, 2005 05:16 PM Forum: Reflectors

off-axis mask

Posted By John Holt
With full aperture, a very large part of the signal to the eye is coming in from the outer portion of the mirror. In addition to removing the central obstruction and defraction from the spider, the off axis mask reverses the signal to noise ratio of the mirror. Only a tiny portion of the signal is comming in at a fast focal ratio. The over whelming majority is now slower, with less coma and astimatism at the ep.

So the mask removes that part of the mirror that can give the most problems, nips off most of the coma, cleans up the image in ep's with regard to astigmatism, cuts the image brightness, removes the central obstruction and spider defraction spikes.

All at a huge loss in resolution.


Another consideration is to try masking off the very outer fraction of an inch of the mirror (turn down edge issues) and use active cooling.


November 21, 2005 03:25 AM Forum: Eyepieces

Newbie EP assistance

Posted By John Holt
Excellent choice for a scope!
That's a great combination of aperture, stable mount, portability, focal ratio and simplicity. Keep that scope in the family. Even if you aquire a more-better one at some future time.


F/8 allows you to get good results from affordable wide field eps. You can shop price, yet stay above the bottom price range for better fit and finish.

You have already determined to get perhaps the most recommended barlow around. Therefore consider an eyepiece/barlow combination that will get you near 200x for a basic upper magnification limit. Something close to 14mm. Your focal ratio allows any number of the affordable four element wide fields to work well. Naglers not required. Really, really nice, but not required.

For a lowest power ep consider one of Paul Rini's long focal length ep's(he is one of our sponsors here). Ask him!

November 21, 2005 04:52 AM Forum: A Day in the Life of the Administrator

Just charge $1 per ad

Posted By John Holt
"... people who really use this site a lot, and really need a way to buy and sell used gear, so its obviously worth it to many to have this site stay viable, and the only way I see that happening is with money."

=========================

Not dissagreeing, but folks will just move the buying and selling to eeek-bay. It's where the whiners and hooligans who violate here take their business now.

I do relatively little buying or selling. But I support Astromart. I also promote it to others not familiar with it.

The modest retail purchases I have made recently have been, and will continue to be, with Anacortes exclusively.

November 30, 2005 11:42 AM Forum: Reflectors

Celestron StarHopper 8" Assistance

Posted By John Holt
Thats a good price for complete 8" telescope. I'd go for it.

If at some point in the future you find that you don't like the secondary support, then you can change it. Use it until that day.

December 17, 2005 04:28 AM Forum: Eyepieces

5mm eyepiece

Posted By John Holt
Siebert Optics has a new line of ep's that includes a 5mm. This isn't a recommendation. They just look interesting.

December 21, 2005 06:16 AM Forum: Eyepieces

Nagler vs. ?? for f/11 SCT

Posted By John Holt
Cheaper wide fields will perform well. Not necessarily "just as well". But you will have more price options for focal lengths you don't have that you find you want.

December 23, 2005 07:03 AM Forum: Eyepieces

Planetary eyepieces??????? 2nd posting

Posted By John Holt
"...what are the best planetary eyepieces on the market? I have a F/6 Mak- Newt. and a F/5 refractor."

========================

Perhaps a Klee.

January 7, 2006 06:27 PM Forum: Beginning Astronomy?

OIII filter

Posted By John Holt
Here is a link with some more info:
http://pages.sbcglobal.net/raycash/filters.htm

I've found my UHC Lumicon to be a bit better combo with my small(+/- 4") scopes on more targets. It lets through more light. The OIII clearly has a more dramatic impact for me in combo with more aperture. Check the classifieds. They do show up, but go fast.

If I understand correctly, the transmission varies somewhat between different brands. I think the Lumicon OIII is more restrictive (darker) than some of the other brands? But I've no real first hand experience with others.

January 7, 2006 07:16 PM Forum: Beginning Astronomy?

I got $500.00 and NEED to get something

Posted By John Holt
Keep the funds, to use toward:

A tracking platform. Large enough for your 10", and next likely size upgrade.

Deeper field atlases, observing guides.

Funding darker sky excursions, to public land and/or star parties.

Funding Member

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