Posts Made By: Hinrich Eylers

I have one, and I like it a lot. No, it doesn't quite replace the very final touchup of getting the Airy Disk just right at 600x, but much more often than not, the seeing doesn't allow for that anyways in my Nexstar 11. However, it does get you very very close to "perfect" collimation very quickly (in minutes even if way off) and painlessly, especially when combined with collimation screw replacements like Bob's Knobs.

It also works as a great tool for initial aligment of the scope when used as a fancy crosshair.

Oh good, another APO vs. SCT discussion

Here's my take:

For the same money, APOs can't hold water to an SCT (or any reflecting scope, really) for visual deepsky, period. You get almost 10x the light per $$. IMHO, aperture always rules. They way you're asking the question and if you're into deeksky, the last thing you want is an APO if that's your only scope unless money is absolutely no object.

IMHO, again considering the price of a really good APO, it may be justified only if you do exclusively planetary work, and even then many argue that the same money will buy an SCT/dob/Mak that will perform equally well or better in most cases. I yet have to see the APO that will outdo a 10-12" SCT/dob/mak even for planetary work, except maybe some 6-incher way into the 5-digit $$ range. Less than perfect seeing - sometimes I suppose if the conditions are just right, and darker background - sure, at a lot less light the background will be darker . So will the image. (OK, they do have slightly better contrast)

Refractors (at least short focal length ones) are also great for wide field viewing, but at 20x mag it doesn't necessarily have to be an APO and/or a dob can do the same job for less money.

But then again, these discussion we had plenty on this board already. It's nearly a religious issue for some.

I think it's you, not your scope's aperture. The 15" minimum aperture thing is a myth. Some people just don't seem to get enough added image processing power from the brain to make up for the light loss per eye, and so they see more with one eye than with two. Sometimes, someone has one very dominant eye already so that adding the second one is detrimental. I feel sorry for you that you don't get to enjoy the sky with two eyes , but just like everything else, binoviewing isn't for everyone. I, for one, will never look cyclops again where I can avoid it.

Do you alternate between both eyes for cyclops observing, or always use the same one?

Or: How long have you been observing? Maybe it may just take some getting used to, retraining you observing mode so to speak.

Hinrich

I don't think we ever answered your question ... how about this:
"For the human eye, the response to light obeys a power law, not a logarithmic one as was once thought. As a result, perceived stellar brightness is proportional to the 0.4 power of actual brightness. Thus an actual brightness increase of one-hundredfold is only perceived as an increase of 6.3 times, and an increase of a thousandfold is only perceived as an increase of 15.8 times." from http://www.geocities.com/michaelcapobianco/PhotometryStarlight.htm - a very interesting article btw re. the capabilities of the eye..

So "twice as bright" will require about six times the light, or 2.5 times the aperture. Instead of 4", you need 10".

But - does it matter? The fact is that the eye is very sensitive to relative changes in brightness, so that it takes a heck of a lot less to make a visible difference!

Keep you 1.25" eyepieces. 2" eyepieces really only are needed when the field stop gets too large for a 1.25" barrel (larger than 24mm Panoptic, 40mm Plossl, etc), plus you can't use them as well in a binoviewer if you decide on one of those. Keep your 1.25" and maybe buy one wide field eyepiece (like a TV55mm Plossl or a 31mm Nagler ). If you can get an eyepiece in either 1.25" or 2", get the 1.25", the only difference is price and weight.

Yes, that is correct. The further away the eyepiece is from the barlow lens, the larger the magnification. Also, the more likely that you won't reach focus.
If you are using a dob, you probably will not see much of a change from a few mm shift as 1) generally the rule of thumb is that a 2x barlow after the diagonal gets you about 3x before the diagonal (and you don't use one) and 2) you likely run out of focus travel before much change happens.
You'll just have to try what reaches focus and what the difference is. Did you look at, say, the moon and try it out?

1) There are camps with strong preferences out there. Some opinions based on a reality, some on a reality 10 years ago, some not at all. You may ask for general advice, but get recommendations based on experience with scopes way outside your price range and for specialized use.
2) Consider what you're interested in. Just the planets and the moon? Everything? Don't know? Don't let your initial choice be driving what you can see.
3) Consider not just the scope, but also what it's mounted on. The mount need to be stable. And, do you want to spend your time looking FOR objects or looking AT objects? If you decide you want to focus on looking AT objects, not practice finding them, the field is narrowed down a lot in the sub-$1000 price range. Consider that many beginners soon give up astronomy in frustration because with only the help of the 50 stars visible in their light polluted backyard, they can't find anything to look at even though their scope still are capable of showing them interesting things once found.
4) Go to a star party and see what's out there (OK, that is point #1)
5) When you narrowed it down to the must-haves for the scope, get the largest aperture yet still easily portable scope in you price range.

You're at a crossroads right now! Before you decide to go and start spending money on what could be rather pricey 2" eyepieces, consider going binoview as well .. depending of course how far you'll go with the 2" selection, there have been people that have financed their binoviewer and several sets of not so expensive eyepieces by selling their 2" eyepiece collection
See http://www.astromart.com/messages.asp?message_id=65321&page= for what is a common sentiment.
Binoviewing is not quite for everyone, but I'd suggest you think about it also.

1) Depends on your mount more than the scope. There are binoviewers on Prontos.

2) The standard viewer with the 2" nosepiece and (unless you have a lot of infocus travel and can reach focus with the viewer by itself) the 2" OCS.

And,later, pairs of not-necessarily-expensive eyepieces.

I had a Celestron LPR filter and I didn't think it did any good on anything. However, performance does depend on the type and proximity of light to you observing location, for me it was apparently not the right match. You can always buy one used, they come up a lot on Astromart, and sell it if it didn't help