8in dobsonian vs 90-100mm refractor for beginner

[shaneh2487]

Hi, I'm new to stargazing but am looking for some advice. I am in the navy's nuclear program and unfortunately do not have much free time; hour to an hour and a half tops at night. I have been using binos for a while now and have decided on getting a telescope. I probably will not have much time to set up a telescope however am leaning toward the dopsonian. Is this type of scope hard to setup and require much time? I would like something somewhat hassle free due to my time restrictions but really like the light gathering ability of the dobsonian. If time to setup before viewing is too great I may have to go refractor. Any help would be greatly appreciated. Also, what are some good models of scopes for both routes? Thanks.

shane

[shaneh2487]

Actually just to be safe, say 45 min a night for viewing time.

[Helen]

Hi and welcome to SGL!

A mirror will take longer to cool than a small refractor, but unless you keep it in a really warm place then you can still start observing fairly quickly - but leave the more critical observing eg planets until a bit later in your session.

A dob is easy to set up - carry out, (ideally leave to coll for a short while, but see above), pop in an eyepiece, and you're away. A refractor is simialr though.

A refractor is lower maintenance, no colimation, but aperture will show more. Its also cheaper to get a good quality mirror than a good quality refractor. So if you're on a budget you'll certainly get more for your money. If you choose a refractor be sure you get a steady mount or it'll end in frustration through wobbly views. If you travel a lot the refractor might win on portability.

If you were to get a good quality refractor and a solid mount, then personally I don't think there is a wrong answer between them. Just choose one and enjoy the views :-)

Helen

[shaneh2487]

Thanks. Yeah I'm looking to spend around 500 and possible up to 600. Will just depend on the route I go.

[nightfisher]

A dob will be quicker to set up than a reasonable refractor, as the frac will require an equatorial mount, unless you went for the AZ4 mount, the dob will need collimating but once you get your head round this task, will only take a few minutes

[sunshine185]

For ease of use, a dob all the way.

[cs1cjc]

When travelling, a refractor on an AZ mount will go with you.

[VigdisVZ]

For that budget I'd get the SW 250p dob for pure visuals. It'll give you a superb view. It's a bit cumbersome, you might want to look at the flextube version if you plan on taking it to a dark site.

It really is a cumbersome scope, but I wouldn't upgrade in increments, you're already bitten by the hobby, so go for something that'll last you.

[Eastridge]

I've had a Dob and a scope on a tripod mount & agree that the Dob is easier to set up and get viewing with.

Cumbersome depends on your strength etc. I am a 5 4 weak woman and I can't carry our SW250 (10") far alone but my 5 10 strong hubby finds it no issue.

Also if you want to transport it what car you have, it's no issue at all in the back of our Galaxy but if you have a small hatchback it would be & so Carl is right to say to consider the Flextube. Or go for the 8" 200P which is more compact and a very popular scope.

I think you need to try and find some in a showroom so you can see for yourself.

I'd caution more that the 250 is a fast scope and so unforiving on cheaper EP's, with the 200P a litle better in that regard.

[jimmyjamjoejoe]

I found no difference between dob and eq mount setup times. Maybe 1 minute tops.

Any dob bigger than 200mm and you'l be moving the base seperately, plonk it down then go get the tube... Same for a tripod, plonk it down and got get the tube. I cant see how anyone would think that pointing it roughly north should take any more than literally a few second.

As for the choice - it depends where you'l keep it. The dob will need to cool down, and i mean REALLY cool down. Even coming from a VERY cold house, mine takes about 40 minutes, with a fan running. I used to think about 40 minutes was enough without the fan, since the views improved a lot, but after 40mins with it running, the views are in a different league, and it became apparent that my scope had never been truly cooled in the past, even after a couple of hours with no fan.

I'd go with a quality refractor unless you can store a dob somewhere at ambient temperature, like a shed/garage.

That's not to say refractors dont need to cool, they just dont take nearly as long, and arent as badly affected by heat since the light only travels through the turbulent air once.

A dob will definitely give you more aperture and bang for buck, but you pay for it with longer cooling times.

[shaneh2487]

I do have a brick shed which locks. It gets fairly close to ambient temp so I think the cool down will be reasonable for me. I really appreciate all the advice. Like I said, I am new to this endeavor so I need all the help I can get. Thanks again

[Matt Scunthorpe]

In terms of mirror cooling, i always heard 5mins/inch of mirror. So for an 8 inch, its about 40mins. HOWEVER, i just start viewing straight away, can't give time for those clouds to roll in while its cooling, and hey, means the views can only get better right?

[rwilkey]

There's a good article on scope sizes by Astro-Baby here:

[ismangil]

How is your sky?

If it's dark you can get away with smaller refractors.

I decided on aperture so went 8" dob. Yes, it takes two trip, base and then tube.

[brantuk]

"Actually just to be safe, say 45 min a night for viewing time."

Crickey! I can spend that long looking at just one object - surely you get some annual vacation or shift days off? Anyway - the dob is your best bet for speed of set up - but as mentioned the scope won't have long to cool down before you're packing away again. Honestly I feel you may be better sticking with the bins - or maybe get some larger ones until you have more time for astronomy - that said, an 8" dob is a very nice instrument.