Posts Made By: John Holt

Siebert Optics, one of our sponsors here, makes 1.5x barlows.

"...if I'm only buying one filter now, would I be better off with a Deep Sky Filter or O-III filter?"

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Neither IMHO.
Instead consider a UHC. It works well on a far greater number of objects. An O111 can yield more dramatic results, but on fewer targets, and best with more aperture.

"I have an F6 newtonian and I'm looking for ... an eyepiece in the 25mm range. I would like to keep it under $120."

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F6 gives you more options then those of us working faster scopes. Most of the just plain wide field ep's like Meade SWA, Televue Widefield, Siebert Ultra's are going to work well. Try a wanted ad.

And it looks like there is a UO 24mm Konig for $50 in the classifieds now. It's edge performance will not be equal to your Pentax's, or a Panoptic. But I'd bet you could recover your cost if you didn't like it.

IMHO, neither.
Because of your ep spread, either one duplicates(or near) something you already have.

"softcover version"

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I wonder if the paper and binding will be as sturdy. The hard cover set has lasted me for years in the field, holding up very well.

"...want to know if I would be better served (optically) with an 8" Dob as opposed to an inexpensive 4" refractor..."

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An 8" scope of any type will stomp a 4". The dobsonian version is stable, relatively portable, extremely easy to set up and inexpensive.

Regarding your AP, visit Eric Jamison's web page. Check out his Refractor mounts. The rest of his web page addresses how well they work! Just google his name.

"Any recommendations, plans, or abandoned mount in your garage ?
Preferably it would fold so as there would be place for the scope and mount in the trunk on back coutry trips."

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I've got a 6" f5 on a alt-az pipe mount. It works! It also breaks down flat for tiny car storage.
Haven't got a picture, but enter pipe mount into the Search Forums. There are a bunch of threads for different inexpensive/easy options. All can be tweeked as needed.

I mounted one 4 on the side of my 13". It vented out the top and bottom of the tube as I had an open cell. Vibration -is- an issue, and counter measures must be taken. Or high power observing is nixed.

Pretty much any air flow helps. I don't think 3" is too little. But you could certainly go more.

There is no optimum fan arrangement. There are just too many variables for that. The mass of the mirror and how much heat it can store, an open vs closed tube, the size of tube and volume of air to be displaced, the type of closed tube itself and how much heat it stores, pyrex vs plate glass, the type of mirror cell and how air flows around it, baffling for intrussive light,... etc.

I found that what worked best was to move a lot of air, first. Get rid of as much of the latent heat as possible, from the mirror, the cell and the tube. Then run just enough air across the mirror to optimize the image at the ep. At the eyepiece is where it counts. I concluded that each night was an experiment on how fast to run the blower after initial cooling.

The real advantage I see in the 10" SCT's is the mount. It tracks your target. And perhaps finds it as well.


The newt can be cooled quicker.
It can also be equatorially or equatorial plateform mounted if you want tracking. Or not. Ebonystar and furniture glides work!
At f/4.5 a Paracorr is really really nice.