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Douglas Rollain

M20 Trifid Nebula in LRGBHa

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Posts Made By: dan hilts

February 12, 2011 02:23 PM Forum: Eyepieces

Eyepiece Dew

Posted By dan hilts
I keep my eyepieces inside. They fog up too easily if they are icy cold. I select the ones I am going to use and carry them outside in a small thermal lunch bag. If I am driving to a remote site, I will throw a couple of the chemical type of hand warmers into the kit when I get there. No wires, no heavy batteries.

I have never experienced any distracting thermal effects from a warm eyepiece.

dan

March 15, 2011 01:23 PM Forum: Landscape Photography

Mud Volcanos - South Salton Sea, CA

Posted By dan hilts
Those photos are much more than just interesting. Very nice work, thanks for posting.


dan

April 5, 2011 03:14 PM Forum: Solar System Observing

Solar Projecting Viewer

Posted By dan hilts
Steve's concerns are very valid.

On axis, the sun's power may traverse the scope's optics without issue. If it gets off axis in an SCT it could cause significant damage to the secondary mounting or the baffle tubes and any optical surface adjacent. If it gets off axis in a Newt or refractor it can make an eyepiece too hot to touch and it can start a fire depending on the tube structure. There are lots of pics of sun damage from unattended Newts.

You can use a very long focus lens to project an image of the sun. The aperature and focal length can be chosen so the sun's image is the same diameter as the lens. In that way, there is never a point in the path where the optical energy is concentrated above what it is in the open sunshine.

dan

July 18, 2011 07:33 PM Forum: Sports

Anybody Watch the Women's World Cup Soccer Match?

Posted By dan hilts
I watched most of the game. Women's soccer doesn't attract a lot of attention in North America. About 5 years ago I saw a bit of a televised game, US versus Canada, played at the Rose Bowl. I doubt there were 3,000 in attendance. Similarily, I saw another game played in Edmonton, and there were even fewer in the audience. The sport is growing here but it doesn't have the speed and power that can show in the men's league.

I didn't get to see the end of the US women versus Japan. When I left, the US had scored in the first overtime period. I thought they had pretty much won it. The penalty kicks are such a poor way to end a game. At that point, the game is over and the outcome has a lot to do with luck. Both teams played well and should be congratulated. On another day, the outcome could have been totally different.

dan

July 29, 2011 01:00 PM Forum: Home Observatories

10" refractor in Gold Mtn Observatory

Posted By dan hilts
Looks serene but what's all that blue stuff in the sky. We don't get that around here!

Great looking scope. It dwarfs the observatory.

dan

September 7, 2011 01:51 PM Forum: Equipment Talk

Transporting an assembled large dob

Posted By dan hilts
Put transport locks/clamps on the primary mirror. This is a good idea whether the scope is assembled for moving or not. Don't forget to release the locks when observing.

Slip a bag over the secondary to keep it clean and secure the bag to the spider or better yet, remove the secondary holder and mirror from the spider and stow safely.

Cushion the scope in its resting place on the bed of the vehicle. If there is a need to secure it in place, use straps, not ropes. Bungy cords have their place but I never use them as the primary means of securing cargo. On a long haul, plan on checking the straps in the first half hour and at every stop thereafter.

Enjoy the ride!

dan

September 8, 2011 02:37 PM Forum: Landscape Photography

Spider webs!

Posted By dan hilts
And another. These things were drapped across the voids between the tree making the whole back yard look like Hallowe'en.

dan

September 30, 2011 08:14 PM Forum: Telescope Making

anybody ever use acrylic primary mirror ???

Posted By dan hilts
About a decade ago I came across a site for a company that made cast first surface mirrors up to 6" diameter. They claimed 1/4 wave accuracy. They were quite inexpensive as I recall. I don't know of anyone who ever made a scope from one of these but if they were still available, I think a large light wieght finder might be a good place to try one.

I searched for the manufacturer a while ago and couldn't find anything similar and until now, hadn't given it another thought.

dan

November 2, 2011 08:23 PM Forum: Equipment Talk

Resolving power - terrestrial / target shooting

Posted By dan hilts
A bullet hole 0.25" diameter at 500m is larger than 10 arc-secs. That's a pretty easy target for an 80mm ED. However, you will need some magnification to see the bullet holes well. The holes can probably be detected at 30X, more power will make it easier. Much depends on the contrast of the hole in the target. As mentioned, the mirage effect can be quite destructive to the views if the sun is shining. Viewing over grass will help.

dan

November 26, 2011 07:05 PM Forum: Beginning Astronomy?

A couple of amateur telescope makers in Nairobi

Posted By dan hilts
What a wonderful experience for you. Thanks for sharing!

dan

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