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Posts Made By: Duane Jacobson

December 19, 2002 02:03 PM Forum: Maksutovs

mn56 cooldown

Posted By Duane Jacobson


I'm looking to buy/build a modestly sized and priced scope, and the MN56 is one I'm strongly considering. Could anyone who has used this scope make some comments on the cooldown time? I will be able to store this scope in an unheated garage, but will still be looking at temperature drops of around 20 degrees F between setup and observing. Can I hope put the MN56 (or for that matter, even the MN66) to good use in these conditions after 30 minutes outside to stabalize?

Thanks,

Duane

April 17, 2003 11:51 AM Forum: Deep Sky Observing

Observing in Austin

Posted By Duane Jacobson

Hi,

Wasn't sure what group to post this in, but here goes. I'm moving to Austin, TX and would like to pick the brains of anyone who lives there with respect to (1) observing sites, either official or unofficial, and (2) new things I should be aware of when moving from a drier, colder climate (Denver) to Austin. I'd imagine dew is something I'll have to learn to deal with... it's pretty much a non-issue here.

I'll probably be living in the north suburbs and will mainly be interested in sites within a short drive (hopefully no more than 30-45 minutes). I visited the Austin Astro Society website, and it looks like there may be an official site in the Lake Buchannan area.

Thanks for any pointers,

Duane

April 17, 2003 12:13 PM Forum: Equipment Talk

equipment for school star parties

Posted By Duane Jacobson

I'm looking for ideas on rigs that can be used for school star parties. The main requirements are that the scope be driven in RA, not cost a whole lot, and be usable with inexpensive eyepieces.

I want to be able to just set these up, pointed at the moon, Jupiter, etc, and then not worry about them. If I'm feeling ambitious on a particular evening I might also bring a nicer scope that I can babysit personally.

I'm thinking two rigs at a total cost of $600-$1000.

Thanks,

Duane

January 23, 2004 05:34 PM Forum: Telescope Making

Folding DOB

Posted By Duane Jacobson

I've been thinking about building a long-focus DOB, something on the order of a 10" f/7. I don't have a beast of a vehicle to haul a tube that long, so it seemed I would have to build a truss DOB.

However, the design shown in ad #242561 under "Telescopes - Reflectors" seems like a neat way to avoid the expense and effort (both building and assembling) associated with a truss structure. I don't really care if this thing packs up into the smallest possible package. I just want it to fit in an ordinary sedan and be easy to set up. I'd guess that making the balance work out is the trickiest part of the deal with a longer tube up top (tube weighs more than a truss, I'd guess). Can anyone else think of problems to watch out for on a project like this?

I can only fit a tube of about 50" in the back seat of my current vehicle. I already own a 6" f/8 tube dob that's in that category, and it can be awkward to use. I like straight-through zero-power finders such as the Telrad, and finding things near the zenith can hurt the neck. I find longer DOBs more comfortable to use (plus they have the added benefit of being more forgiving when collimating).

Thanks for your thoughts.

Duane Jacobson

April 23, 2004 09:43 PM Forum: Telescope Making

Conical mirrors

Posted By Duane Jacobson


RF Royce has been offering conical-shaped mirrors for a while now. He recently posted a note on his website (www.rfroyce.com) saying that even 8" and 10" versions will be available soon. He claims that no mirror cell is required with such a mirror... only that it be bolted to the bottom of a mirror box or other substrate. So, even though the mirrors are more expensive (~300 dollars extra for a 12.5" model), the total extra cost wouldn't be a lot more if you factor in the savings of a good mirror cell.

It seems there could be substantial improvement in cooldown time with such a mirror, which is the main consideration that piques my interest in such a product.

Anybody have experience with (or opioions on!!) such a mirror?

Thanks,

Duane

May 11, 2004 09:02 PM Forum: Equipment Talk

Question about 2"->1.25" adaptor

Posted By Duane Jacobson


I'm parting out a TV85 setup, selling a 2" diagonal and OTA separately. I also have a 2"->1.25" adaptor. Is this piece presumed to be standard equipment with either the OTA or the diagonal, or is it a separate accessory generally purchased on it's own.

Thanks for any guidance.

Duane

July 13, 2004 01:43 PM Forum: Equipment Talk

vehicle for dob

Posted By Duane Jacobson


At some point I'd like to upgrade to a bigger (16"-18") dob. Right now I drive a Honda Accord, and I doubt any scope of this size will fit into an Accord.

I'd rather not buy an SUV. I prefer sedans and would like to stick with something similar. I'm guessing a hatchback or wagon of some sort would be the ticket. Any suggestions???

Thanks,

Duane

February 3, 2005 06:41 PM Forum: Telescope Making

assembling a compound scope?

Posted By Duane Jacobson

I'd like to build an 8"-10" OTA for high-power visual observing that I can mount on a GEM (G-11 or similar). I don't have a place for a permanent setup, so it needs to be reasonably portable. The G-11 head and tripod are each less than 40 pounds, and I don't want to go much heavier than that.

One option would be a Newtonian OTA. I don't want to tax the mount too much, so I'm thinking an 8" f/6 or f/7 would be about the largest Newtonian for this mount(?).

An alternative would be an 8" or 10" compound scope. I prefer open-tube scopes for faster thermal equilibriation, so I'm looking at either a Classical Cass or Dall-Kirkham here. Tak Mewlon is one option, althought the 10" is out of my price range. Also, I'd prefer something more optimized for planetary viewing, longer than f/12 and with a smaller secondary. Robert Royce is offering D-K optics sets, but I have no experience assembling or even collimating this sort of scope (been a Newtonian and small refractor guy).

Can anyone describe the difficulty of assembling a compound scope OTA, in comparison to assembling a Newtonian OTA? Does the compound scope need to be more rigid (guessing it's more critical to maintain collimation)? What sort of tubing, mirror holders, and rear end cap would be needed? Can this be done with only some basic tools, or does one need a machine shop for this project?

Thanks,

Duane

March 29, 2006 03:03 PM Forum: Telescope Making

mount for conical mirror

Posted By Duane Jacobson

Any tips on where to buy a lightweight mirror mount that's compatible with the Royce conical mirrors (8" model)?

My most-used scope is a 10" f/5.2 dob. It's nice, but I'd like something a little smaller, that's easier to carry outside and allows seated viewing. It looks like I could make an 8" f/6 ota at about 10 pounds, which I think would be pretty convienent.

Thanks,

Duane

May 18, 2009 09:55 PM Forum: Eyepieces

Finder eyepiece for a TV85

Posted By Duane Jacobson

Hi,

I'll soon be accepting delivery of a TV85, and I'm shopping for a 2" eyepiece to use with it. I'm hoping to use the scope as its own finder with this eyepiece, since after all the TV85 has the potential for a 4.4-degree TFOV. Oh sure, this eyepiece will get used for observing as well, but the primary use will be for finding.

My main criteria are (1) weight, (2) forgiving with respect to eye position, and (3) TFOV at or close to max with the TV85. Cost... shooting for around $200 or less, although meeting the three stated criteria is more important than absolutely staying under $200. I realize I won't find anything that's "sharp to the edge", given these restrictions.

Weight is important because I don't want the scope to be super unbalanced everytime I use this eyepiece to find a new object. I realize there are probably no half-pound eyepieces in this class, but I'm hoping to keep it to around one pound.

Forgiveness with respect to eye position is important, because I'll be moving the scope a lot searching for objects with this eyepiece. Don't want it to black out everytime I make a slight adjustment.

---

Just looking through the Anacortes website, I see two possibilities. The Stellarvue 42mm FMC Widefield, and Orion's 38mm Q70 Superwide. There are also some Plossl offerings at 55-56mm... it seems a bit of a waste to have an 8mm exit pupil, but if they're the best at meeting my three criteria I'll certainly consider them.

Comments, other alternatives???

Duane