Eye pieces & filters for Celestron Travelscope

[Appleblossom]

Hi, I have asked this before but am SO thick that I need to ask again... I have been told that to see Saturn, etc I need a 2x Barlow lens? I am going soon to an area where there is very little light pollution & thought I would take this opportunity to use my telescope. Can anyone provide me with any links to places that sell reputable lenses as I am finding it is a bit of a minefield & I do not have 'money to burn'... While I am here, what about filters too? Are solar filters for a telescope as safe as they say they are? TIA

[Stu]

6 minutes ago, Appleblossom said:

Hi, I have asked this before but am SO thick that I need to ask again... I have been told that to see Saturn, etc I need a 2x Barlow lens? I am going soon to an area where there is very little light pollution & thought I would take this opportunity to use my telescope. Can anyone provide me with any links to places that sell reputable lenses as I am finding it is a bit of a minefield & I do not have 'money to burn'... While I am here, what about filters too? Are solar filters for a telescope as safe as they say they are? TIA

Is yours the 70mm Travelscope? If so it has a 400mm focal length and is not ideal for planetary observing but it is still possible.

In theory, your scope will cope with up to around x140, but I suggest sticking to x80 to x100 or so. A x2 Barlow would help in terms of effectively increasing the focal length and reducing some of the aberrations you get. I would combine it with a good quality eyepiece if possible, say a 10mm or an 8mm to give x80 or x100.

What sort of budget do you have in mind?

Our sponsors are a good place to start looking

www.firstlightoptics.com

cheers,

Stu

[rockystar]

is it the 70mm travel scope you have? what eyepieces have you currently got?

if it is the 70mm, then your scopes focal ratio is f/5.7, so a 5.7mm eyepiece will give you x70 magnification (you won't be able to get a 5.7, so 5mm will give you x80). If you add a 2x Barlow to this, this will double the magnification to x140 which will be the limit for your scope. This will give you a good view of Saturn.

if you have a 10mm eyepiece, you will get x40 mag, and you can Barlow this to x80, you will be able to see the rings at this mag, but probably won't see a gap between them and the planet.

And I've written almost exactly the same as Stu!

[Appleblossom]

Thank you both, I get SO confused... I currently have 10mm & 20mm, so a Barlow lens x2 will give me 20mm & 40mm? Is that correct? Which is still way off my max? Or am I not understanding this right?

[DRT]

2 minutes ago, Appleblossom said:

Thank you both, I get SO confused... I currently have 10mm & 20mm, so a Barlow lens x2 will give me 20mm & 40mm? Is that correct? Which is still way off my max? Or am I not understanding this right?

It's the other way around. The x2 barlow will double the magnification so effectively turn your 10mm and 20mm eyepieces into 5mm and 10mm.

If you haven't use this set-up much it might be easier pointing at the Moon first. It's much easier to find than anything else in the night sky and would allow you to easily see the effects of using the various combinations of eyepieces and barlow that you already have. Even with your 10mm and barlow Saturn is going to be very small in your scope due to the short focal length.

[rwilkey]

Hi there, a 2x Barlow Lens would shorten the focal lengths of your ep's making the 20mm and the 10mm a 10mm and a 5mm respectively, so you can see already that there is some duplication with your current set up, best mag at 80x with a 5mm ep.  80x is probably the best you can expect with a 70mm scope.

[Dave In Vermont]

It goes the other way: A 2X Barlow would give you the equivalent of 5mm & 10mm.

Here's a formula to use to know the magnification of eyepieces in telescopes:

Your scope has a Focal-Length(F.L.) of 400mm. So you divide 400mm by the Focal-Length of the eyepiece - say 10mm. Like this:

400mm / 10mm = 40X

Just plug in the numbers!

Have fun -

Dave

 

[Appleblossom]

On the advice of Stu I have had a look at the Barlow Lens on the site that sponsors here:

https://www.firstlightoptics.com/all-eyepieces-barlows/celestron-x-cel-barlow.html

Will this suffice for what I need?

So much for Jessops, they told me it doubled the mag Dave in Vermont, shows what they know or DON'T know... thank you for your helpful calculation

[Moonshane]

A 2x barlow does double the magnification but the smaller the focal length of the eyepiece in mm the higher the magnification. So a 10mm eyepiece (or equivalent e.g. 20mm with 2x barlow is the same thing really) gives half the magnification of a 5mm eyepiece with the same scope. To get 100x in your 400mm focal length scope, you would need the equivalent of a 4mm eyepiece or an 8mm with a 2x barlow.

[Stu]

I'm just thinking that a Barlow effectively doubles the focal length of the scope so may improve the performance of cheaper eyepieces. Might be a better route than the shorter f/l eyepiece but the budget question still stands?

[LukeSkywatcher]

I'm thinking that no matter what EP or barlow is used with the 70mm travelscope that the view of planets will not be any better than with 10x50 bins. Ive tried. The main problem is the tripod supplied. Its rubbish. If you use a better tripod you may have better luck. Its a nice little scope and well made. It performs best as a wide field scope for observing clusters,star fields and the Moon. It even makes a great solar scope (ONLY when used with the proper safety filters).

 

[Appleblossom]

1 hour ago, Stu said:

I'm just thinking that a Barlow effectively doubles the focal length of the scope so may improve the performance of cheaper eyepieces. Might be a better route than the shorter f/l eyepiece but the budget question still stands?

I have Celestron eye pieces so I don't want to buy anything cheap & nasty, seen a Celestron Barlow x2 for £68, I think...?

[John]

5 hours ago, Appleblossom said:

I have Celestron eye pieces so I don't want to buy anything cheap & nasty, seen a Celestron Barlow x2 for £68, I think...?

I doubt anyone will recommend anything cheap and nasty here. Many of the Celestron eyepieces are just the same as Skywatcher or other brands but with the Celestron name printed on them. The company that owns and makes Skywatcher also owns and makes Celestron stuff now.

One of the best quality barlows that I've used that did not cost too much is the Revelation 2.5.x barlow:

http://www.telescopehouse.com/barlows/revelation-barlows/revelation-astro-2-5x-barlow-lens.html

Revelation stuff is made by GSO - another manufacturer who's stuff you see under many other brandings as well !.

 

 

[Appleblossom]

On Wednesday, May 11, 2016 at 23:14, John said:

I doubt anyone will recommend anything cheap and nasty here. Many of the Celestron eyepieces are just the same as Skywatcher or other brands but with the Celestron name printed on them. The company that owns and makes Skywatcher also owns and makes Celestron stuff now.

One of the best quality barlows that I've used that did not cost too much is the Revelation 2.5.x barlow:

http://www.telescopehouse.com/barlows/revelation-barlows/revelation-astro-2-5x-barlow-lens.html

Revelation stuff is made by GSO - another manufacturer who's stuff you see under many other brandings as well !.

 

 

Sorry didn't mean 'cheap & nasty' as a slight on this site at all... ? would this Barlow lens that you have recommended fit my Celestron Travelscope 70 though?

[John]

15 hours ago, Appleblossom said:

Sorry didn't mean 'cheap & nasty' as a slight on this site at all... ? would this Barlow lens that you have recommended fit my Celestron Travelscope 70 though?

If it has a 1.25" eyepiece fitting then any 1.25" accessory should fit.

Edit:

With your current eyepieces (20mm and 10mm I think ?) the 2.5x barlow would give you the equivilent of 8mm and 4mm eyepieces. With the Celestron Travelscope 70 those eyepiece focal lengths work out as follows in terms of magnification:

20mm = 20x

10mm = 40x

8mm = 50x

4mm = 100x

I'd say that 100x would be the practical useful maximum that you can get from the scope and then the conditions and target would need to be suitable to use this. The Moon, Saturn and Mars would fall into that.

You should be able to see that Saturn has a ring system at 40x, maybe even 20x and also Saturn's brightest moon, Titan. At 100x under good seeing conditions and with some experience you may be able to see the Cassini Division in the rings.

The Moon will show loads of detail at all the magnfications but 100x should reveal interesting features such as the "Straight Wall" (Rupes Recta) when the Moon is at a suitable phase.

Mars is always a tricky target but you should be able to make out some darker markings on the disk and maybe one of the pole caps at 100x