Jump to content

NLCbanner2024.jpg.2478be509670e60c2d6efd04834b8b47.jpg

The long & short of Barlows?

The Warthog

Recommended Posts

The Warthog

The Warthog

Posted
Posted

I believe I have heard that long 2x Barlows give better results, visually, than short Barlows. However, most of the Barlows I see advertised are shorties. I also hear that long Barlows and diagonals don't mix. Can someone shed some light on this topic, and who makes a good, long 2x Barlow? :?

This question was inspired by fmeireso's post in Best and Worst.

Link to comment
Share on other sites
bern

bern

Posted
Posted

A short Barlow needs to use a shorter (negative) focal length lens, which is more likely to show aberrations. The Celestron Ultima gets away with it because it uses three elements, the new Celestron 2x X-Cel is short and uses ED glass.

It's similar in a way to refractors ie the good old ones were very long because they used standard glasses, nowadays they're short and use special glasses and or more elements.

bern

Link to comment
Share on other sites
fmeireso

fmeireso

Posted
Posted

I would like to buy a Barlow lens for use with my Orion Optics 8" F6 tube. Should I buy a short or long? I seem to have problems with focusing my 'scope as there is not enough travel outwards with the focuser.

It depens. On a newt i would advice a longer barlow, because you don't need a short one because you don't use diagonals on newts. It is my belief that longer barlows are most of the time a bit better then short barlows, ...law of optics. High end barlows like TV, Takahashi, TMB are of the longer kind.

However, this said i don't believe there are bad barlows. Most of them , not to say all them provide good views. Differences are subtle only noticable after carely observing and good seeing.

The Tal 2X is very short and is not as sharp as the TV on planets but is very good on deepsky and very affordable.

The Orion shorty plus 2X/Ultima, very good on planets, but looses a bit contrast compared to the TV2, a bit of a drawback on deepsky objects.

The Chinese BT2 skywatcher Synta barlow is a tad sharper then the Tal but less contrast...;

But all of them provided good views....

These are some of the onces i compared..

I still like the TV the most, even the owner of the Ultima/shorty plus barlow admitted that too after some comparison.

The choice you'll have to make by yourself...

Your focussing (outward travel) problem can be solved by using an extension tube, seems a bit common the the OO scopes.

Link to comment
Share on other sites
John

John

Posted
Posted

I have tried a number of short and long barlows including the TAL 2x, Tele Vue 2x and 2.5x, Orion Shorty Plus 2x and the Celestron Ultima 2x. All those listed IMHO performed well but the best were the Tele Vue 2x and the Celestron Ultima (despite the fact that the Orion is supposed to be the same piece of equipment as the Celestron Ultima). I went for the Celestron in the end because it's short format made it easier to use (ie: no removal of the diagonal needed in the dark - I'm a refractor user) and it's performance was, at least to me, the same as the Tele Vue. BTW the Celestron Ultima seems to me to be nearer a 2.2x barlow.

John.

Link to comment
Share on other sites
lunator

lunator

Posted
Posted

I would like to buy a Barlow lens for use with my Orion Optics 8" F6 tube. Should I buy a short or long? I seem to have problems with focusing my 'scope as there is not enough travel outwards with the focuser.

Blinky

I have a 8" f6 OO scope.

I have the Antares apo barlow as my main Barlow. It has worked well.

The only point to be aware of is that the 3 element design does reduce the limiting magnitude slightly so if you are looking for really faint it could be an issue.

Cheers

Ian

Link to comment
Share on other sites
The Warthog

The Warthog

Posted
  • Author
Posted

The Ultima/Shorty Plus/Antares Elite can't be unscrewed. Just a heads up if that was the plan. The cheapy barlows are no problem if you are looking for a cheap extension tube.

Russ

Interesting. My Celestron Barlow is one number off from the Ultima. It is 95306, I think, while the Ultima is #95307. At any rate, the Ultima ends in 6 or 7, and mine is 7 or 6. Anyway, it unscrews quite handily. I have used it for an extension tube.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.