Barlow issue..need advise

[Vali x]

hey guys. last night i used for the 1st time my 3X barlow to view the moon. previous i had a 5x, but i exchange it with 3x b/c i didnt had enough focuser length to have a crisp image ! now, with 3x, it seems to have the same issue. my question to you guys is if i use 3x on DSO or other planets, witch are further away comparing to the moon, i should have the same issue? in my head i have the idea that if the object is further away, i will have enough focuser length to see a good image ! i didnt had a chance to test my idea last night, but like i said: that's in my head for now. need some advise here (tonight i wanna use 3x on Jupiter to see if i am right, but the confusing is killing me !). please let me know

[acey]

A Barlow is a negative lens that gets placed a certain distance below the eyepiece by a tube. How much the Barlow increases magnification depends on how long the tube is. If the tube is too long then you're not going to reach focus on any object that is effectively at infinity (i.e. Moon, planets, stars, galaxies etc). You could replace the tube by a shorter one (which will change the amount by which the Barlow increases magnification) or get a different Barlow, or try using different eyepieces. Given that you can't reach focus with x5 or x3, it sounds like maybe what you need is x2.

[yeti monster]

Perhaps moving your primary mirror up the tube a few mm may bring your focal point within reach of your barlow?

edit: Or down, as the case may be.

[iamjulian]

If you are focused on the moon, you are focused on the planets.

The terms is "hyperfocal distance" if you want to read more about the concept. Hope that helps.

[Vali x]

well, still confused, sorry. i used different EP- i have a Meade 8-24mm- and all gave me the same fussy white image. i could replace it with 2x, but i really wanna push the limit of my scope. we are talking about 150x magnification difference ! is obvious that i dont wanna mess up by playing with the mirrors. tonight will be the final test on planets. it could major impact if i will get a short tube for barlow? mine has a quite long tube -Antares 3x

[Nova]

Is it outward focus travel or inward that you dont have enough of? If its the former then you could add an extension tube

[JamesF]

With an 8mm eyepiece and a 2x barlow you're at 300x magnification already, aren't you? If your seeing is good enough to stand more than that then perhaps a 6mm or 4mm ep combined with the 2x barlow would work.

If you're trying to get 450x magnification though you may well just be asking too much without moving to a mountain in Hawaii.

James

[Vali x]

i dont have enough outward focus...give me more details on that extension tube Steve !

[Vali x]

James, you'r right: 8mm allow me a 150x basic+ a 3x barlow i should go to 450x. i thought about getting myself a 3-6 mm EP, but i have to "smooth" the wife to increase the budget (already increased several times ! )

[John]

....If you're trying to get 450x magnification though you may well just be asking too much without moving to a mountain in Hawaii......

My thoughts exactly James !.

I rarely use more than 250x with my 10" scope, even under excellent viewing conditions.

[Vali x]

ok, i got the point. i will start looking for an extension tube. thanks guys

[Vali x]

well, i found the solution for my issue: last night i was trying to see if i can stop at a certain point the barlow from going all in..and it worked! now i have enough focus length to use it ! )

[Nova]

ta daa!

looks like your problem is sorted but in answer to your question here

http://www.jimsmobile.com/images/adpt_std_ext.jpg are examples of focuser extension tubes. just google it and you will find loads!