Telescopes - bang for the buck

Last Edited By Krjb Donovan
Last Updated: Mar 11, 2014 07:56 PM GMT

Question

QUESTION: My ventures into dobs & cats have proved unsatisfactory, due almost entirely to back surgery & insufficient storage space. Have settled on refractors now, but my interests still remain divergent - planetary, DSOs, even solar. I can't seem to get any comprehensive input about which refractors are best for all. My best guess is to get a lage diameter achro (no, some CA doesn't bother me too much). What I desire is the best compromise for contrast, FOV, sharp images - whatever I can get in a smaller (but not too small) package. Also, it must be in a package with a motorized GOTO mount. Why do almost all refractors come with OTA only? Any help is appreciated. Followup to cover subjects for which there was insufficient character space. Thank you.

ANSWER: HI Tom

I think you have already beaten this question around a bit. As you know, all telescopes are compromises, and there is never one right answer--only a few scopes that get close to the ideal. I have to say that I am surprised when you want bang for the buck, and then suggest a refractor. Refractors offer smaller aperture per buck, and are usually heavier than most reflectors of the same size. So when you tell me you want bang for the buck, and you have back problems, I don't think a refractor is what I would suggest to you!

I have a 4.5 inch dob reflector that I originally bulit as a finder scope for my 17.5" dob, and it weighs almost nothing. I have taken it camping, even backpacking on a short trip. And it gives me 4.5 inches of aperture, and cost me less than $100. Is that bang for the buck?

If you have back problems, then a large aperture refractor will weigh a ton...and will cost another ton. Sure, a Takahashi will give you stunning views, expecially if you don't mind a tiny bit of purple haze around the brightest images. But add that to a GOTO mount, and you are talking about something that will weight 100 pounds. I don't suggest backpacking with that!

I understand that Goto ideal...but aperture for aperture, a simple newtonian with GOto will cost less, weigh less, and give you great images. Better than a refractor? Yes, on some objects. And will you use it more because it weights less and is easy to move? Absolutely. It may not perform quite so well on the planets...but if you want DSOs, then aperture is the ONLY thing that matters. You can get a really decent 6" reflector with GOTO for under $400 that weighs under 35 pounds. Get the longer f/l version for higher contrast, fit it with a smaller diagonal, and you have a terrific scope for all seasons. A similar refractor will cost you over $1000 and weigh 75 pounds...and won't give you appreciably better views of anything except maybe the planets on a perfect night.

What am I missing?

Paul Wagner

---------- FOLLOW-UP ----------

QUESTION: Pau,

You have both answered my questin & confused me a bit. I'm glad to finally have somebody to talk turkey! I alsayw 'heard' that although refractors were limited in aperture, the image sharpness was laughably far above any mirrored scope. Apparently that's not entirely correct. I've been told straight out that a 4" refractor is way superior to a 4" reflector, even if it's just an achromat. And achros are not that pricey vis a vis the apos (whose popularity I will never understand, I guess, without seeing one).

I'm really a decent guy & no hardnose. Can you suggest a scope of any kind that separates into parts of less than 40 lbs. each and stores in a closet? How about a 4" Mak? Will it be as good as a nice 4" achro? Yeah, I know - heavy mirror. But I can do 35-40 lbs. And why are refractors so popular? Taks are way out of my range, but lots of folks buy them.

Thank you VERY much for the data! I hope I'm not too much trouble.


Answer

Hi Tom

Refractors, really good refractors, do probably give an image that might be 5% better than similar sized reflectors. And refractors don't require the same kind of collimation that reflectors do. But if I wanted a scope like you are describing, I would pick up a nice dobsonian reflector that is big enough to show me some really good DSOs, and I could still stop it down to observe the planets. Remember that the biggest single defect in reflectors is that central diagonal mirror. An 8 inch long f/l reflector with collect 8 times the light of a 4" refractor, and will cost and weigh less. And if you create a mask to leave a 3 3/4 inch clear aperture for planetary observations, it will perform like a refractor without the CA.

Just my two cents--but I have owned about ten scopes, and only two of them were refractors, both disappointing compared to slightly larger reflectors.

Paul Wagner

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