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MrGold

Question regarding seeming lack of focus.

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Hello. New member here. Recently I acquired a second hand skywatcher explorer 130p and I took it out last night and saw Jupiter and some other stuff. However, Jupiter seemed way brighter than I remember being almost white and when I used the 10mm eyepiece with a 2.25x Barlow (roughly 150x mag) I had trouble focusing it since the focus window was quite small. Mind you the moons were points and I could see 2 bands and the South Pole but it just felt too bright. Now I checked for collimation and it seems to be alright so before I go checking my laser collimator and the size of the spider legs to make sure they are all perfectly aligned I was just wondering if the trouble focusing could be due to the atmosphere or light pollution?

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From your description it sounds like you were correctly in focus but at 150x I'm surprised that Jupiter would appear too bright in a 130mm aperture. I doubt that your collimation has much to do with it. Welcome to this forum.

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Sounds like it's working ok to me...bright is good. Jupiter is almost white, the colours are there but subtle. 

What were you using last time you looked?

If you can focus the moons down to points that's good. You're seeing the right level of detail for the scope under average conditions. Mag of *150 is right at the top end for a 130P, I think that model has a spherical mirror rather than a paraboloid. 

I'd star test it first ..try a high bright star...before messing with the collimation!

 

Regards, RL

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49 minutes ago, rl said:

Mag of *150 is right at the top end for a 130P, I think that model has a spherical mirror rather than a paraboloid. 

The various 130P scopes share an excellent parabolic mirror - the clue is the 'P' 🙂

 

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Sorry..my mistake!

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I suspect it was probably the seeing conditions being unsuitable for the magnification you were using, washing out the detail of the dark regions and giving the optical illusion that it was brighter. 

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If the moons are pinpricks, your focus is right. Lack of detail on the planet is most likely down to seeing conditions. The cure is to reduce the magnification. A small distinct image is always much better than a big indistinct one.

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Posted (edited)

 

8 hours ago, Demonperformer said:

If the moons are pinpricks, your focus is right. Lack of detail on the planet is most likely down to seeing conditions. The cure is to reduce the magnification. A small distinct image is always much better than a big indistinct one.

 

8 hours ago, Ricochet said:

I suspect it was probably the seeing conditions being unsuitable for the magnification you were using, washing out the detail of the dark regions and giving the optical illusion that it was brighter. 

Thanks for that. Just checked my pollination and the scope seems to be slightly out of alignment again as well. So a mix of both I believe  last night I took the scope out again and it was slightly better.

Edited by MrGold
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42 minutes ago, MrGold said:

Just checked my pollination

You can't be too careful 🙂

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Do you have any ND filters or color filters ? If so they help with the brightness of Jupiter . 

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Stare intently into the brightness until your eye begins to adjust and details will start to reveal themselves 👍

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41 minutes ago, Demonperformer said:

Don't you just love autocorrect!!

 

45 minutes ago, Stub Mandrel said:

You can't be too careful 🙂

Funny thing is, I spotted my mistake, corrected it and it went back to pollination again...

30 minutes ago, celestron8g8 said:

Do you have any ND filters or color filters ? If so they help with the brightness of Jupiter . 

Nopes

4 minutes ago, Red Dwarfer said:

Stare intently into the brightness until your eye begins to adjust and details will start to reveal themselves 👍

Yeah. I can see detail. Main problem is the very small focus window I get. I mean it's probably less than a millimetre on the focuser... I will collimate the scope again and see if that fixes it.

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33 minutes ago, MrGold said:

I mean it's probably less than a millimetre on the focuser

Yep, it probably is. You could fit a larger knob over the existing one to make adjustment easier.

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4 hours ago, MrGold said:

 

Funny thing is, I spotted my mistake, corrected it and it went back to pollination again...

Nopes

Yeah. I can see detail. Main problem is the very small focus window I get. I mean it's probably less than a millimetre on the focuser... I will collimate the scope again and see if that fixes it.

The 10mm kit lens has a VERY narrow depth of field and that is probably the issue and nothing to do with collimation - doesn't do any harm to give that a quick check as well - if it's badly off you would see three Jupiters as you are bringing it into focus 👍

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20 hours ago, Red Dwarfer said:

The 10mm kit lens has a VERY narrow depth of field and that is probably the issue and nothing to do with collimation - doesn't do any harm to give that a quick check as well - if it's badly off you would see three Jupiters as you are bringing it into focus 👍

Thanks for that. Yeah that eyepiece seems a bit rubbish. It says super on the box so I thought it was a super plossl but I don't think it is. Do you know what kind of eyepiece it is?

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Posted (edited)

MA - modified achromat lenses most likely ...

The lower powered kit lens , 25mm MA ( 20mm with Celestron ) are pretty decent performance wise , but very few people get on with the 10mm MA because of the narrow depth of field ...

Here is a 10mm MA beside my 10mm Super Plossl for comparison ...

F567D161-0AD8-4863-8876-0B5034770AE7.jpeg

Edited by Red Dwarfer
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Posted (edited)

That looks exactly like my lens.

Now to convince my wife I really need to spend 50 pounds on a new lense.

Can anyone put me in contact with the FLO marriage council division?

I saw somewhere that the starguider pieces are really good bang for buck. Any other recommendations?

Edited by MrGold

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Posted (edited)

Agree with the comment about enlarging the focus knob. Whilst the focus travel will not change, the distance you have to turn the knob will increase significantly giving you more control. A plastic lid off a jar stuck on top is easy. You could try blu tack or sticky velcro so as not to make it permanent. Something like a peanut butter jar lid with a wide, knurled rim is ideal, but sized to fit your focuser and scope. Scour the supermarket aisles and you will find it.

Edited by IanL

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1 hour ago, MrGold said:

That looks exactly like my lens.

Now to convince my wife I really need to spend 50 pounds on a new lense.

Can anyone put me in contact with the FLO marriage council division?

I saw somewhere that the starguider pieces are really good bang for buck. Any other recommendations?

The BST 12mm is well regarded by users on SGL - Sky’s The Limit eBay shop has them £10 less than FLO at the moment at £39.99 ...

EB661D30-664F-4564-9B03-6EC8D0C06522.jpeg

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42 minutes ago, IanL said:

Agree with the comment about enlarging the focus knob. Whilst the focus travel will not change, the distance you have to turn the knob will increase significantly giving you more control. A plastic lid off a jar stuck on top is easy. You could try blu tack or sticky velcro so as not to make it permanent. Something like a peanut butter jar lid with a wide, knurled rim is ideal, but sized to fit your focuser and scope. Scour the supermarket aisles and you will find it.

The alternative is a brother, a workshop, a lathe and chunk of aluminium from ebay for about £4 and you can miraculously become the owner of one these oversized focus knobs, isn't it smart?!:

IMG_4112a.jpg

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They also have the 8mm. Which one would you recommend as a planetary lense for a 130/650 scope? 

With 2.25 barlow I would get around 180x with the 8mm and 123x with the 12 mm.

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3 minutes ago, JOC said:

The alternative is a brother, a workshop, a lathe and chunk of aluminium from ebay for about £4 and you can miraculously become the owner of one these oversized focus knobs, isn't it smart?!:

IMG_4112a.jpg

Those look amazing. But so far i can focus it. It just feels easy to overshoot. If I am about to get a better eyepiece i might postpone DYI. 

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My telescope is from a similar stable, just a bit bigger and F6.  I have a 8mm BST and it works well for my setup.  However, strange though it may sound looking at the list of lovely EP's in signature what I have certain liking for is my 14mm Meade 4000 in my x2 SW Barlow.  By rights amd in theory I have far better single EPs to use, but it just seems to work well for me, so sometimes it isn't about the best sounding EP.  The other thing to remember is that Jupiter doesn't have solid edges like the moon,  it isn't a 'chunk of rock' and so will never look solidly 'crisp' around the edges no matter how good the EP.

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