Another telescope question

[RedNyte]

Hi! I'm the new guy on the block.

I presently own a 70mm refractor and I'm looking to get something a little bit better. I have found a couple of scopes in my price range and was wondering if anyone has used any of them or has any advice.

The first is a Celestron C6-N Reflector, and the second is a Meade DS-2130LNT Reflector.

Unfortunatly there are no clubs around (atleast without driving 2hrs) to ask any questions, so I found this site in hopes to learn something new. Thanks for your help in advanced and hope to get into some good discussions.

[redshifter]

Either of those would be fine scopes, but for the same $ you can get an 8" dobsonian: http://www.telescope.com/shopping/product/detailmain.jsp?itemID=366&itemType=PRODUCT&iMainCat=4&iSubCat=9&iProductID=366 so for the same $ you get 2" more in aperature, which adds up to a significantly better light grasp that the 6" Celestron. At that price range, more aperature is the way to go for you IMO; better bang for the buck. A dobsonian is very easy to use, and I personally don't miss the goto, although that is an inexpensive option for dobs.

[RedNyte]

How portable are dobs anyways?

[redshifter]

I'd say they're a mixed bag as far as portability. An 8" dob's tube is about 48" long and around 10" in diameter, my 10" dob's tube fits in the back seat of my car (Subaru Legacy sedan). The mount fits in the front seat of my car, it would probably fit in the rear cargo area of a small station wagon as well. Total weight of tube and mount for the 8" dob I linked to is about 40 lbs. According to the specs on the telescope.com site, the 8" dob has a 44.5" tube length and the tube+mount weighs 41 lbs.

[Alleline]

What about staying on target? Whenever I change EPs on my EQ-mounted Newtonian, I need to fiddle with the fine-adjustment knobs to re-center the object. How do you do that with a Dob?

[redshifter]

Dobs are strictly manually tracking scopes (unless you invest big $ in an equatorial platform) by simply nudging the tube along while looking through the eyepeice. In practice, this is not at all difficult. Even at higher mags (>150X) I don't have too much trouble tracking objects. At lower mags, objects are in the eyepeice field for up to a few minutes at a time, tracking isn't a problem at all.

[glasspusher]

I have a XT 8 and it is a good scope. It can be moved in and out of the house in one piece. For hauling in a car I put tube assy. in its shipping box. In my case, the XT 8 is the most portable scope I own except for my P.S.T. My home made 12.5" Dob, handtruck works ok, or take it apart. Tracking for Dobs can be installed at a later date. I use Dob Driver II on the 12.5" and it works really good. It works even better on my 12.5" fork mounted truss tube Newtonian in E/Q mode.

[aurora]

If a Dob is working correctly, it moves with a very light touch (to aim it or to track something), it moves without "stiction" moving smoothly, and it stops when you stop pushing or pulling on it. The amount of effort it takes to move the scope in azimuth should roughly equal the amount of effort it takes to move the scope in altitude.

This has to do with the friction on the altitude bearings and the asimuth plate. Generally, Dobs use teflon pads running on "Ebony Star" formica (a brand name for bumpy formica). Also, to increase the friction, in addition to the weight of the tube some models have springs that attach to the altitude bearings. Also, some models have extra large altitude bearings which makes the motion smoother (although you can go too far and have bearings that are too large, as a home builder I speak from experience, having learned the hard way).

If a commercial Dob doesn't move to your satisfaction, the beauty of the simplistic design is that you can modify it yourself (unlike with a mount that might require machining of metal parts if you were to undertake such a thing).

[Fr. Wayne]

(forgive this outburst on a snowy evening in cloud land) I too prefer the dobs for how my one hand can manuever at any speed and any direction (to follow satellites, planes, etc.) to all models which "follow the sky" or require 2 knobs to adjust or even require a 90 degree eye-piece to look into. It's simplicity remains stellar. No computer image can record what I see, because I will always prefer to look upon my real-time universe with a world of pre-conceived ideas no one else has ever compiled before. Even Hubble photos, great science as they are, are Hollywood glamour to me. "Beauty is in the eye... " Yes, I'm sometimes jealous of CCD'ers and Digital-Wizards and Push-button Comet-Hunters, but I've seen with my 10" light bucket stars that spoke great Truths straight through my unfiltered sensories from times immemorial before language got in the way. And the more I do that, the more I learn.

[RedNyte]

Do they need much cleaning of the mirrors and lenses? If so how hard is it? The reason I ask these questions I have neices and there friends who are interested and I would love to keep them interested in astronomy and science. I was thinking of donating my 70mm refractor to the girl scouts troops in my area. I am frequently ask to show up and show them the night sky.

[Fr. Wayne]

Keep a cover over it. I use a hefty bag. And always let the scope adjust to temperature and humidity and never leave the scope open when the morning dew drops. In my 15 years of use, I've never had to touch the primary mirror to clean it. Why? Because I take good care of it even when travelling across country by car- it's as long as my back seat is wide but amazingly light. The base is another story. It at least has handles but must weigh about 50 lbs. (P.S. I do not recommend this scope for large party viewing as even the slightest touch can lose the view. Scopes with push-button coordinates are perfect for showing a lot of people a lot of cool sites in a hurry).

[glasspusher]

The mirrors are easy to clean, if done right. But they don't need cleaning very often. Just don't point a flashlight down the tube in the dark, even a very clean mirror will look dirty. The way the XT 8 is made it won't get much, if any, dust inside while in storage. If you buy that scope you won't be disappointed.

[aurora]

The mirror in a Newtonian telescope probably only needs to be cleaned every year or two or three, if you keep it covered when not in use, and if you do not observe next to salt water where there are waves putting moisture in the air, or next to a dusty gravel road that has a lot of traffic.

More commonly than cleaning, you will want to collimate the telescope. You can find websites or books that explain collimation. I'm sure links have been posted in this forum before.

As to cleaning lenses, you need to do that regardless of what kind of telescope you have.

[redshifter]

I've had my 10" dob 3 yrs, only cleaned the mirror once. Dust doesn't really affect the mirror's performance, a mirror with a layer of dust only on it should probably be left alone.

[Fr. Wayne]

Since a few of us "light bucket brigade" have assembled. I want to go on record that for suburban skies, my Uranometra 2000.0 (1989 version) has been the perfect chart for me as my scope matches it's maps to the smallest magnitude so well that I was able to set my scope on a similar latitude star, go inside, count off to the exact minute, return and see the exact new spot that my chart calculated. That was very cool.