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Posts Made By: dan hilts

March 19, 2006 05:53 PM Forum: AstroMart FAQ

Auction question

Posted By dan hilts

I know some die-hard bidders who use a bidding engine to monitor auctions. Essentially a software that places marginally higher bids in the last seconds of an auction. If you add 10 minutes, you take the engines out of the game.

have fun,
dan

March 31, 2006 08:45 AM Forum: Beginning Astronomy?

Refractors vs Reflectors?

Posted By dan hilts

Stu,

Some of your points are valid but not absolute. Cooldown can be an issue with any scope but a small reflector is more likely than a small refractor to have problems. Viewing angle and eyepiece position are not a problem with a refractor if you use a good mount.

However, the biggest attraction the refractor has is the very wide fields of view with little or no edge distortion. All Newts suffer from coma by design and the amount of coma is dependant of F ratio, not aperature. Add to that the need to collimate a Newt to get even a small distortion free field and the refractor wins. Plus lenses last forever if not abused. Mirrors need recoating.

I have both types of scopes. I prefer the refractor in smaller sizes.

clear skies,
dan

April 17, 2006 09:23 AM Forum: Reflectors

What can I see with.....

Posted By dan hilts

If you do an internet search on 'Messier Sketches' you will find a number of interesting sites where there are hand sketched views by various amateurs. Here is a link to one site where the author has used a 10" SCT. There lots of others that may help you find what you are looking for.

have fun,
dan

http://www.ghg.net/cbr/logs/

May 31, 2006 09:17 AM Forum: Beginning Astronomy?

star test images

Posted By dan hilts

Itz,

Here's a link to a bunch of star test images. Some are good, some not so good but comments are provided.

http://aberrator.astronomy.net/scopetest/html/refractor100_8.html

clear skies,
dan

June 22, 2006 08:22 AM Forum: Eyepieces

1.25" Low Power Eyepiece

Posted By dan hilts

In the 1.25" format, the field of view that you can see is limited by the barrel of the eyepiece. Somewhere around 30-32mm is the maximum focal length needed to reach the limit. So a 40mm eyepiece will not show any more field than a 30-32mm eyepiece in the 1.25" size. To take advantage of the wider field the 40mm can cover, you need to go to the 2" format.

If you are stuck with the 1.25" size, you may find that you would like the higher power of the 32mm eyepiece over the 40mm.

clear skies,
dan

July 5, 2006 10:24 AM Forum: Solar System Observing

Urban heat island effect on planetary observations

Posted By dan hilts

Dan,

You may want to read this recent post from the Equipment Forum:

http://www.astromart.com/forums/viewpost.asp?forum_post_id=453732&poll_id=&news_id=&page=

clear skies,
dan

August 5, 2006 04:23 PM Forum: Beginning Astronomy?

Measuring Degrees with a dobsonian?

Posted By dan hilts

Hi Casey,

To get an estimate of your field of view you can look at the moon which is very nearly a half degree. You can then determine how far it is across the view in the eyepiece. You will need a bit of time for your eye to adjust back to normal after looking at the moon. If you can identifiy a pair of stars on a chart and get their distance you can use them to estimate your field of view.

Many of the objects discussed in recent threads will be easily seen in binos from dark skies including M51, 81, 82, 31, 13, 3, 4, and a whole bunch of others around the teapot. If you look with binos, you will see them even without a map. But...

The moon is big right now and until it is out of the sky, some of these targets are pretty tough even with a big scope. Last night we could see M51 in a 14" but it wasn't as good a view as a 4.5" will give under dark conditions.

M103 in Cass stands out in binos at dark skies but gets lost in the background stars when using a scope. I never found 103 to be very impressive and I never found it at all until I used binos at the cottage. Too many stars in the neighborhood. Use low power for the best view.

The companions to M31 can be seen in a low power view but dark skies are needed to see all three objects. I couldn't see them all until the moon went down last night and then it was easy. M31 from dark skies is a naked eye object for most folks.

Most messier objects can be seen in binos and I think many are easiest found this way. Some targets, like M57 are bright enough to be seen but just too dang small to be identified.

Being stuck in suburbia is like being stuck with a big moon. It doesn't lend itself to finding DSOs.

good luck and clear dark skies!
dan

August 6, 2006 11:21 AM Forum: Eyepieces

GSO 2" Barlow

Posted By dan hilts

You can also remove the lens element from the GSO barlow and screw it directly into a number of 2" eyepieces. I have tried it with the RPD 30mm 80 degree eyepiece and others. It doesn't work so well if you are using a refractor with a diagonal but it worked great on a Newt.

clear skies,
dan

August 24, 2006 05:20 PM Forum: Equipment Talk

Dumb question? (optics and dew: physics?)

Posted By dan hilts

Not such a dumb question. I asked exactly the same thing about 18 months ago. As Jim stated, the answer lies in the fact that all bodies radiate heat to the sky in the form of infrared radiation. When the sky is really clear you can loose a lot of heat to outer space. So much heat in fact, that surfaces can easily get colder than the ambient air and then condensation occurs.

Some surfaces are better radiators than others, that's why some things dew up faster.

dan

September 2, 2006 11:30 AM Forum: Telescope Making

mirror grinding and polishing machine

Posted By dan hilts

Making a machine is a realistic goal. However, it may not be practical for a samll number of mirrors.

Wlliam-Bell carries a book, it is dated but still has some useful info. You may be able to find a copy on AM if you put out an ad. I am sure there are others. Maybe someone else will suggest something different.

"Advanced Telescope Making Techniques, Volume 2"

good luck.
dan