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Can't focus my telescope with a barlow lense, what should I do?


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Just now, Lotinsh said:

Thanks, you mean make a new post about 130p telesope and barlow?

had a ganders on FLO and this offered to work with your scope https://www.firstlightoptics.com/barlow-eyepieces/astro-essentials-125-2x-barlow-with-t-thread.html 

https://www.firstlightoptics.com/heritage/skywatcher-heritage-130p-flextube.html

As per the title of this post don't think you change it so no harm in creating a new post specific for your scope 

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May I suggest you leave the tube ~1cm from fully extended, when using the barlow. You might achieve focus then.

Try it using 25mm barlowed.

 

Rune

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3 minutes ago, Lotinsh said:

@Pondus Maybe that will work, I'll try that, but the problem is it doesn't go inwards enough, not outwards, maybe it will help, not sure though as I cant get it to screw in more

Doing this should give you some "extra" inward travel...

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Hi your missing the point if you remove the lens section of the Barlow then put this aside you don't need it at the moment now use the rest of the Barlow which is the tube part as an extension to see if you can focus the eyepieces if you can then you do need an extension

Edited by Neil H
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On 13/04/2021 at 19:48, Pondus said:

May I suggest you leave the tube ~1cm from fully extended, when using the barlow. You might achieve focus then.

Try it using 25mm barlowed.

 

Rune

I think this advice may have been misunderstood. The advice in this post is that as the Heritage 130p is a collapsible dobsonian. the telescope itself can be shortened by about 1cm when the barlow is going to be used. 

On 14/04/2021 at 03:01, Neil H said:

Hi your missing the point if you remove the lens section of the Barlow then put this aside you don't need it at the moment now use the rest of the Barlow which is the tube part as an extension to see if you can focus the eyepieces if you can then you do need an extension

Sorry, Neil, but it is actually you who is missing the point. The eyepieces focus when placed directly into the focuser. Putting an extension tube between eyepiece and focuser is completely unnecessary and will do nothing but push the eyepieces out too far so that they cannot be focused.

@Lotinsh: What you need to do is to send this barlow back as it does not work with your telescope and look for one in which the upper section is physically shorter as this should mean that the lenses in the nose don't have to be pushed as far beneath the focal plane, or as advised earlier, get advice from other owners of this telescope about barlows which definitely work with it. However, given that you only have the starter eyepieces supplied with the telescope, my first upgrade choice would be to replace those (or at least the 10mm) with something better first.

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@Ricochet Thanks for the advice, I already made a thread about barlows that work with my telescope, so far got 1 response and I can't find that barlow in Europe, the link was US, could you maybe recommend me an barlow lens that would work? Also how much would better 10mm eyepiece would be?

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@Ricochet Did what you told me, shortened telescope's tube by 1 cm and could easily could get focus on everything! So, should I still return my barlow and get one that fits my telescope or just not pull out my telescope fully?

 

Today was a clear night finally, looked at the moon and the view was amazing! Wish I could have sat there for the whole night, but I have school tomorrow.

Here's a picture I took today trough my telescope:

IMG_20210418_235044.thumb.jpg.dd1b04b09a5fa025be39eed15be617bb.jpg

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On 18/04/2021 at 17:31, Lotinsh said:

@Ricochet Thanks for the advice, I already made a thread about barlows that work with my telescope, so far got 1 response and I can't find that barlow in Europe, the link was US, could you maybe recommend me an barlow lens that would work? Also how much would better 10mm eyepiece would be?

The thread that I can see has links to the sponsor of this forum, FLO, which is a UK supplier who will deliver to Europe.

Of the two barlows suggested in that thread one is a generic barlow sold under the astro essentials brand. If you search on eBay for a 2x barlow you will find many listings for the exact same barlow shipped directly from China to whichever country you live in. 

The second suggested barlow is sold by Baader. Searching for Baader products on the websites of more local European suppliers should allow you to find it. 

With regards to eyepieces it is possible that almost any eyepiece would be an improvement. The cheapest option would be a decent Plossl eyepiece, but at 10mm the eye relief will be getting a bit tight so the slightly more expensive generic eyepieces sold as "Planetary" eyepieces would be better. Beyond this, it depends how much you are willing/able to spend on an upgrade. My suggestions for an upgrade would be one of: 

  • 8/12mm BST Starguider (sold under different names outside of the UK)
  • 10mm Baader Classic Ortho
  • 9mm Vixen SLV
  • 8.8mm Explore Scientific 82°
  • 9mm Baader Morpheus
On 19/04/2021 at 00:24, Lotinsh said:

@Ricochet Did what you told me, shortened telescope's tube by 1 cm and could easily could get focus on everything! So, should I still return my barlow and get one that fits my telescope or just not pull out my telescope fully?

Routinely changing the extension of the telescope during a session will become tiresome quite quickly. My choice would be to find a barlow that comes to focus without the need to change the extension of the telescope. 

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