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Using my barlow


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Was out with my scope yesterday (startravel 80) was using tracking scope and 25mm eye piece to get the spots I wanted and then would change to my 10mm. But whenever I used my barlow I couldn't get a point of focus, was all just blurred! Whats the best way to use the barlow and when is best to use it? Any tips?

Jessica

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Hi Jessica,

That sounds unusual. I believe your scope has a focal length of 400mm, so the 10mm EP barlowed down to a 5mm (it is a 2x Barlow, I'm assuming?) yields a magnification of 80x, which should be perfectly acceptable in your telescope.

Can I ask how you were using the Barlow? Did you insert the eyepiece into the Barlow and then the Barlow into the scope? Also, what were you attempting to focus on?

Aaron

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The ST80 should go down to a 5mm eyepiece but being f/5 you likely need better then the supplied items, 10mm + barlow, to accomplish it. I would also say that an eyepiece that is less then 5mm or effectively less will not perform well.

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Hi Jessica,

That sounds unusual. I believe your scope has a focal length of 400mm, so the 10mm EP barlowed down to a 5mm (it is a 2x Barlow, I'm assuming?) yields a magnification of 80x, which should be perfectly acceptable in your telescope.

Can I ask how you were using the Barlow? Did you insert the eyepiece into the Barlow and then the Barlow into the scope? Also, what were you attempting to focus on?

Aaron

Yes you're right about the scope it's 400mm. So I'll talk you trough what I did and you may see what I did wrong. I've put my 90 degree diagonal on with my 25mm eye piece, used the tracking scope until I got Jupiter. Then changed to 10mm for better view. Then I took out the 10mm put my Barlow (2x) onto the diagonal then attached the 10mm to the Barlow. Just couldn't get it to focus! Did the same with the moon and still no focus... Do I perhaps have to take the diagonal off? I didn't think it would make any difference! Thanks for the advice

Jessica

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The ST80 should go down to a 5mm eyepiece but being f/5 you likely need better then the supplied items, 10mm + barlow, to accomplish it. I would also say that an eyepiece that is less then 5mm or effectively less will not perform well.

That's good to know, I don't mind buying some more eyepieces, if it gives me a better view!! :)

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Yes you're right about the scope it's 400mm. So I'll talk you trough what I did and you may see what I did wrong. I've put my 90 degree diagonal on with my 25mm eye piece, used the tracking scope until I got Jupiter. Then changed to 10mm for better view. Then I took out the 10mm put my Barlow (2x) onto the diagonal then attached the 10mm to the Barlow. Just couldn't get it to focus! Did the same with the moon and still no focus... Do I perhaps have to take the diagonal off? I didn't think it would make any difference! Thanks for the advice

Jessica

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That's strange. You're definitely putting everything where it needs to go. And nope, don't remove the diagonal... You'll have one heck of a sore neck in the morning if you observe without it! :)

When you tried on the moon, could you clearly see that you had it in the field of view (ie. was it definitely there but you couldn't get it to clear focus or could you just not see it at all?). If you could see it, but not get it clear, did you run through the entire travel of focus? If so, then it sounds like your focuser might not have enough back travel.

Also, have you tried using your Barlow with the 25mm eyepiece? And finally, you HAVE definitely taken the dust caps out of both ends of the Barlow, haven't you?? :)

Hope we can get it sorted for you.

Edited by Joves
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That's strange. You're definitely putting everything where it needs to go. And nope, don't remove the diagonal... You'll have one heck of a sore neck in the morning if you observe without it! :)

When you tried on the moon, could you clearly see that you had it in the field of view (ie. was it definitely there but you couldn't get it to clear focus or could you just not see it at all?). If you could see it, but not get it clear, did you run through the entire travel of focus? If so, then it sounds like your focuser might not have enough back travel.

Also, have you tied using your Barlow with the 25mm eyepiece? And finally, you HAVE definitely taken the dust caps out of both ends of the Barlow, haven't you?? :)

Hope we can get it sorted for you.

Oh yes definitely dust caps off! :D I tried the moon because it was so bright I new I had it, I could see a very bright disc so I tried the full range of focus but I just became a bigger or smaller bright disc... I think I just need to continue messing around with it, i suppose it could have been dewy on the lense... But when I swapped back to just the 10mm the view was great! Thank you for your clear advice, I just wanted to check I was using it correctly! I'm sure I'll get there, I may try buying a 5mm eye piece too see what happens :) I will also try with the 25mm because I didn't try that! Thanks again

Jessica :)

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Oh yes definitely dust caps off! :D I tried the moon because it was so bright I new I had it, I could see a very bright disc so I tried the full range of focus but I just became a bigger or smaller bright disc... I think I just need to continue messing around with it, i suppose it could have been dewy on the lense... But when I swapped back to just the 10mm the view was great! Thank you for your clear advice, I just wanted to check I was using it correctly! I'm sure I'll get there, I may try buying a 5mm eye piece too see what happens :) I will also try with the 25mm because I didn't try that! Thanks again

Jessica :)

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Sure, definitely try it with the 25mm EP to ensure there is no fault with the Barlow itself (which I couldn't see why there would be, but you never know). You don't want to spend money on a 5mm EP if it's pushing the limits of your scope (again, this shouldn't be the case... Your scope should handle that magnification ok).

Best of luck with it, Jessica. Look forward to hearing you've got things sorted!

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That I can't help you with, unfortunately! Doesn't matter how how hard I blow at the sky, I can't even get the clouds to move here in Sydney, so I'm thinking I definitely don't have enough puff in me to get rid of yours!! :)

Good stuff, let us know how you get on!

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Are you using the 45 degree diagonal supplied with the ST80 for daytime viewing? Or have you replaced it with a 90 degree diagonal for night time viewing? I'm just guessing right now - and in theory it shouldn't make a difference - but it could possibly be where the problem lies. :)

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Are you using the 45 degree diagonal supplied with the ST80 for daytime viewing? Or have you replaced it with a 90 degree diagonal for night time viewing? I'm just guessing right now - and in theory it shouldn't make a difference - but it could possibly be where the problem lies. :)

Thank you! I'm using the 90 so it should be fine... It could've been the atmosphere, it was pretty poor and not good seeing!

Jessica

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Good news, good news!! Went out tonight for another attempt with my Barlow and alas it worked! Used it on the moon for an easy target and it worked a treat! Saw the moon like I've never seen it before :) very chuffed, perfect way to start my Christmas holiday!

Jessica

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Good news :) The problem could have been dew related perhaps? Dew on any element can quickly end a night unless you have the 12v hairdryer handy :D

You could do a lot worse than to upgrade the 10mm standard EP still, sorry to tempt you with spending but those 10mm modified achro EP's arn't that great :( Someting like a 8mm or 12mm BST starguider seems to come recommended almost universally :)

hth

Chris

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Good news :) The problem could have been dew related perhaps? Dew on any element can quickly end a night unless you have the 12v hairdryer handy :D

You could do a lot worse than to upgrade the 10mm standard EP still, sorry to tempt you with spending but those 10mm modified achro EP's arn't that great :( Someting like a 8mm or 12mm BST starguider seems to come recommended almost universally :)

hth

Chris

Hello Chris,

It wasn't dew I'm sure of that, pretty sure it was atmospheric! Perhaps we shall never know... Probably me just being a ninny and impatient!! I would like to invest in some different EP's it's just cash flow as ever! Thanks for the recommendation, I will check it out :)

Jessica

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