What is the point of a 5*Barlow?

[Stargazing Glaswegian Gaza]

HI again,

I have a *2barlow and is wondering what the point of the 5* Barlow is if used with most eyepieces as it's will exceed the practical power of use on most telescopes if not all, any ideas on that?

Regards,

Mr Gaza.

[houston]

I have a 40mm eyepiece which would make it a 8mm but i guess the eye relieve would be terrible. Pointless but i bet someone buys them.

[fredster]

Its a planetary imaging thing really. Not so much for visual. That said it would turn my 18mm Ortho into a 3.6mm, which in the ED80 would give 167x with good eye relief.

[Stargazing Glaswegian Gaza]

how do you edit posts?

[jason.p]

My Tal2 came with a x4 Barlow to go with the 8, 15, 25 and 42mm plossls, giving me what seems to be a reasonable range of mags. Agreed x600 with the 8mm is, for practical purposes, beyond the capability of the scope but the others seem Ok. Now I've added a 32mm I think I've got it covered.

Sent from my GT-P5110 using Tapatalk HD

[rory]

how do you edit posts?

after x amount of posts you get an edit option . cant recall how many posts though ,

[fredster]

how do you edit posts?

There is an edit button at the bottom right of the message. Bit it goes when someone else posts a reply to your message.

[skir]

Over 250 posts.

Sent from my Nexus 7 using Tapatalk 2

[Stargazing Glaswegian Gaza]

It might just me but bit it seams a bit impractical to put for example a 40mm into a 5* Barlow considering the size or length it will be sticking out the eyepiece for one thing. And would you not loose some of the image quality as well, like its sharpness and the size of the image you are viewing than the purity from gust the 400mm Plossl?

[fredster]

It might just me but bit it seams a bit impractical to put for example a 40mm into a 5* Barlow considering the size or length it will be sticking out the eyepiece for one thing. And would you not loose some of the image quality as well, like its sharpness and the size of the image you are viewing than the purity from gust the 400mm Plossl?

If its a poor quality barlow you will lose image quality. But there are some cracking barlows around these days that will not diminish the view by any detectable amount.

And one reason for using a barlow on a low power eyepiece is to retain some of the qualities of that eyepiece, such as comfortable eye relief. It's quite common for people to prefer using say a 12mm Ortho with a good 2x barlow instead of a 6mm Ortho because the 12mm is a far nicer eyepiece to use and those benefits get carried over by the barlow.

Btw the 40mm becomes an 8mm with the 5x barlow. But that would not be a good example as the 40mm is hampered by a small apparent field.

[rwilkey]

No point in 5x Barlow for visual, I believe it is mostly used for astro-photography.

[scoobee]

after x amount of posts you get an edit option . cant recall how many posts though ,

After 250 posts

[Stargazing Glaswegian Gaza]

Hmmmm,

Would it be worth while having a *4 if you already have a *2?

REgards,

Mr Gaza

[rwilkey]

Hmmmm,

Would it be worth while having a *4 if you already have a *2?

REgards,

Mr Gaza

Hi Mr Gaza, in a word 'No'. Not good for visual in my opinion, and will put magnification beyond the capability of the scope probably. The other thing I find is that you soon lose the object you are viewing when you try to magnify too much too soon, I find this with ep's too.

[trev27]

They are very very useful for solar system imaging. Particularly useful for HA imaging of the Sun.

[Stargazing Glaswegian Gaza]

Hi Mr Gaza, in a word 'No'. Not good for visual in my opinion, and will put magnification beyond the capability of the scope probably. The other thing I find is that you soon lose the object you are viewing when you try to magnify too much too soon, I find this with ep's too.

I notice this when viewing with my 15mm to then go down to my 6.4. I thought it was something too do with the eyepiece. Especially when viewing (what I assume at the time to be an asteroid) must be a comet as it has been in the atmosphere for at least 1 or 1&1/2 months now at least and is still about but getting fainter by the week.

At first i thought it was the asteroid as it came in view about 2 or 3 week before the asteroid peaked its nearness on 15 feb. I remembered saying to me self I never new asteroids had small tails!

Is that a common newbie mistake?

regards,

MrGaza

[rwilkey]

Loosing objects when trying to magnify is quite common I think amongst amateur astronomers.

[Stargazer_00]

Just thinking about this - would adding a barlow, to extend the focal length of a newtonian, make for more accurate collimation with a lazer collimator? I dont know exactly how the barlow lens works. Just to save me crunching some of my own brain cells reading up I just thought i'd throw it out there. I dont use a barlow to collimate at the moment, although I do wind the focuser right out.

[michael.h.f.wilkinson]

A 5x barlow can be used to turn an F/4 to F/5 newtonian into F/20 to F/25 which matches the pixel size of the DMK21/SPC900/QH5 chips optimally for planetary imaging. With my slow C8, I tend to stick to 2x, 2.5x and 3x TeleXtenders and Powermates.

[Stargazing Glaswegian Gaza]

Interesting, never thought i would generate a debate as much as this when first posted the subject matter!