Good morning all,
Just got myself a 2x gso barlow.
What I notice is that the image can't seem to get focus and brightness suffer abit.
On 20mm ep still ok but once on 10mm ep the brightness and focus become poorer.
What can I do to improve it? Pls advise. TIA.
greeting from 2nd days newbie.
- cloud_cover
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Re: greeting from 2nd days newbie.
Congrats on the purchase!
Unless the barlow is severely defective, its unlikely to be the Barlow per se.
The 2 issues you raised are brightness and poor image. With regards to brightness, this is only to be expected because by doubling the magnification, you are also halving the exit pupil. Hence the image must get darker. Generally, the brightness of your barlowed 20mm should be equal to your "naked" 10mm. The barlowed 10mm, of course, will be even darker.
With regards to image quality, a few things are possible. Firstly, you are using an f/10 scope which means that the exit pupil is right at 0.5mm, the minimum recommended size before floaters and irregularities in your own eye become significant. Secondly, at 5mm you are pushing 50x per inch aperture, which is the max recommended for good quality optics. Finally, at 227x significant atmospheric effects can cone into.play, particularly if your target is lower in the sky.
If you want to find out if its the Barlow causing issues or your scope/atmospherics, simply borrow a 5mm eyepiece and see if the image is any different
Unless the barlow is severely defective, its unlikely to be the Barlow per se.
The 2 issues you raised are brightness and poor image. With regards to brightness, this is only to be expected because by doubling the magnification, you are also halving the exit pupil. Hence the image must get darker. Generally, the brightness of your barlowed 20mm should be equal to your "naked" 10mm. The barlowed 10mm, of course, will be even darker.
With regards to image quality, a few things are possible. Firstly, you are using an f/10 scope which means that the exit pupil is right at 0.5mm, the minimum recommended size before floaters and irregularities in your own eye become significant. Secondly, at 5mm you are pushing 50x per inch aperture, which is the max recommended for good quality optics. Finally, at 227x significant atmospheric effects can cone into.play, particularly if your target is lower in the sky.
If you want to find out if its the Barlow causing issues or your scope/atmospherics, simply borrow a 5mm eyepiece and see if the image is any different
DON'T PANIC
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Re: greeting from 2nd days newbie.
cloud_cover wrote:Congrats on the purchase!
Unless the barlow is severely defective, its unlikely to be the Barlow per se.
The 2 issues you raised are brightness and poor image. With regards to brightness, this is only to be expected because by doubling the magnification, you are also halving the exit pupil. Hence the image must get darker. Generally, the brightness of your barlowed 20mm should be equal to your "naked" 10mm. The barlowed 10mm, of course, will be even darker.
With regards to image quality, a few things are possible. Firstly, you are using an f/10 scope which means that the exit pupil is right at 0.5mm, the minimum recommended size before floaters and irregularities in your own eye become significant. Secondly, at 5mm you are pushing 50x per inch aperture, which is the max recommended for good quality optics. Finally, at 227x significant atmospheric effects can cone into.play, particularly if your target is lower in the sky.
If you want to find out if its the Barlow causing issues or your scope/atmospherics, simply borrow a 5mm eyepiece and see if the image is any different
Thanks message well note.
- weixing
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Re: greeting from 2nd days newbie.
Hi,
Have a nice day.
The magnification for the 10mm with 2x barlow is too high for your scope especially for an uncollimated newtonian.bern wrote:Good morning all,
Just got myself a 2x gso barlow.
What I notice is that the image can't seem to get focus and brightness suffer abit.
On 20mm ep still ok but once on 10mm ep the brightness and focus become poorer.
What can I do to improve it? Pls advise. TIA.
Have a nice day.
Yang Weixing
"The universe is composed mainly of hydrogen and ignorance."
"The universe is composed mainly of hydrogen and ignorance."
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Re: greeting from 2nd days newbie.
talk about collimate, think I need to have it done. my 10mm don't seem to be as shape as my 20mm.weixing wrote:Hi,The magnification for the 10mm with 2x barlow is too high for your scope especially for an uncollimated newtonian.bern wrote:Good morning all,
Just got myself a 2x gso barlow.
What I notice is that the image can't seem to get focus and brightness suffer abit.
On 20mm ep still ok but once on 10mm ep the brightness and focus become poorer.
What can I do to improve it? Pls advise. TIA.
Have a nice day.
how should I go about with this collimating thing? my scope is only 2 weeks old, should I send it back to Astro Scientific centre to let them have a check?
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Re: greeting from 2nd days newbie.
Need some help here.
I had send my telescopes into astro scientific to do collimation. but just now I bring down to look at saturn the focus totally worse than before. where else can I go to for collimate my scope?
TIA
I had send my telescopes into astro scientific to do collimation. but just now I bring down to look at saturn the focus totally worse than before. where else can I go to for collimate my scope?
TIA
- cloud_cover
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Re: greeting from 2nd days newbie.
Hi Bern,
If you had it recollimated at AstroSci, perhaps you might want to bring it back and get them to re do it as well as do an on the spot test?
If not, you can try to ask some of the dob owner for help.
If you had it recollimated at AstroSci, perhaps you might want to bring it back and get them to re do it as well as do an on the spot test?
If not, you can try to ask some of the dob owner for help.
DON'T PANIC
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Re: greeting from 2nd days newbie.
Ok tomorrow I'll go down and see how again, thankscloud_cover wrote:Hi Bern,
If you had it recollimated at AstroSci, perhaps you might want to bring it back and get them to re do it as well as do an on the spot test?
If not, you can try to ask some of the dob owner for help.
- shirox
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Re: greeting from 2nd days newbie.
They will probably ask you to do it yourself. Have a search thru the net and you should find yourself with loads of informationbern wrote:talk about collimate, think I need to have it done. my 10mm don't seem to be as shape as my 20mm.weixing wrote:Hi,The magnification for the 10mm with 2x barlow is too high for your scope especially for an uncollimated newtonian.bern wrote:Good morning all,
Just got myself a 2x gso barlow.
What I notice is that the image can't seem to get focus and brightness suffer abit.
On 20mm ep still ok but once on 10mm ep the brightness and focus become poorer.
What can I do to improve it? Pls advise. TIA.
Have a nice day.
how should I go about with this collimating thing? my scope is only 2 weeks old, should I send it back to Astro Scientific centre to let them have a check?
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Re: greeting from 2nd days newbie.
I had send my telescopes back to astro scientific this morning. hope they do a good job this round.
but I don't have the proper tools to do the job myself.
but I don't have the proper tools to do the job myself.