/ Any astronomy telescope experts in?

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The Lemming - on 20 Jan 2013
After 2-3 years mulling over the issue I finally bought a telescope and I'm very happy with it. Problem now is, like with digital cameras, I want to replace the stock eye pieces.

My question is what magnification should I go for if I want to see planets?

And what magnification should I have for seeing DSO's?

I can then use this info to calculate the size eye piece for my new toy.

Cheers
psaunders - on 20 Jan 2013
In reply to The Lemming:

As a rough guide (in my opinion):
Planets: 50 - 200x
DSOs: 25-50x

Open clusters / nebulae look great through huge 2" diameter, 30mm+ wide angle eyepieces. Planetary nebulae and globular clusters need a slightly higher magnification... around 40-50x as a rough guide.

Planetary eyepieces I have less experience with; I could never get on with the tiny eye relief of a 4mm eyepiece.

A Barlow lens is another option which increases your range of magnifications cheaper than more eyepieces, but I never found them as good as dedicated eyepieces.

Coel Hellier - on 20 Jan 2013
In reply to The Lemming:

> My question is what magnification should I go for if I want to see planets?

About 200x. Though it depends on the optical quality of the telescope and the stability of the mount; magnifying blur won't get you anywhere.

> And what magnification should I have for seeing DSO's?

About 10x to 40x. You probably want 3 eyepieces, wide-field, medium and high-magnification.
The Lemming - on 20 Jan 2013
In reply to Coel Hellier:

> About 10x to 40x. You probably want 3 eyepieces, wide-field, medium and high-magnification.

I've been doing a bit of digging on on Stargazers Lounge forum asking about magnification ranges but I mostly get eye piece sizes, which would be nice but the suggestions are from people with telescopes with different focal lengths than my telescope.

May I ask what magnifications you would suggest for wide, medium and high ranges?

I can then use this info to choose toys for my new Skywatcher Heritage 130p. Its not the Hubble but so far with the kit eye piece I've been blown away looking at Jupiter.

Cheers

Coel Hellier - on 20 Jan 2013
In reply to The Lemming:

> May I ask what magnifications you would suggest for wide, medium and high ranges?

10x, 40x, 200x.
The Lemming - on 20 Jan 2013
In reply to Coel Hellier:

Much appreciated.

Shopping time for some lovely eye pieces.
andi turner - on 20 Jan 2013
In reply to The Lemming:

Start of with something twice the focal speed of your telescope. I presume the 130p is an f5, so get a good quality 10mm eyepiece, a plossl will be good enough, the meade 4000 series are nice and a good price.

It's a nice all-rounder and should be good for centring planets and showing brighter DSOs.

Then, something wider. I like the Vixen Lanthanum eyepieces for this, a 25mm would be nice.

For planetary, the best on a budget has to be the orthoscopics. A 4mm or 6mm 2nd hand Circle T shouldn't cost you more than about 30, and you have to pay a lot more to really beat them when it comes to planetary viewing. A 6.5mm eyepiece would give you 100x magnification.

I suppose under really good condition you could barlow that to 200x, but it's not very often we get conditions that good in the UK.

So, with a 6mm, 10mm and 25mm and a 2x barlow, you also have 3mm, 5mm and 12.5mm. That should be plenty for almost everything you want. Other than that, wait for good seeing and ensure your scope has cooled down properly and is well collimated and you should be well away.
The Lemming - on 21 Jan 2013
In reply to The Lemming:

Just made a purchase on my first eye piece, a 5mm, which should give me 130x magnification. I hope it plays nicely with my barlow.

I know that at the moment I can see a tiny dot of Jupiter with a few lines accross it, and I could see better images on the web, but that's not the pint as I can see it with my own eyes in my back garden.

And next month I will buy one more for wide stuff. :-)
The Lemming - on 21 Jan 2013
In reply to Coel Hellier:
> (In reply to The Lemming)
>
> [...]
>
> 10x, 40x, 200x.


Silly question, or I think it is, but wouldn't a pair of binoculars cover the 10x magnification?
andi turner - on 22 Jan 2013
In reply to The Lemming: Yes they would. A pair of 10x50 are great, but your scope will give you 10x130. That will be much brighter.
Coel Hellier - on 22 Jan 2013
In reply to The Lemming:

As Andi says, the point about telescopes is as much about light-gathering (making things look brighter) as magnification. Indeed more magnification will make things look fainter (in terms of light per portion of image) and thus faint nebulae can be harder to see. That's not a problem for planets, but there is also no point in magnifying beyond the quality of your image (set by optical quality of the telescope, stability of the mount, atmospheric seeing etc), since you'll only magnify blur and make things look worse.
The Lemming - on 23 Jan 2013
In reply to Coel Hellier:


Well I have learnt a valuable lesson tonight about 5mm eye pieces and aiming them at Jupiter.

They don't go well with budget 130mm mirrors and 2x Barlow's. I did get to see a grey blob and three bright dots though. :-(

I may be pushing the limits of my optics too far just to get a better view of Jupiter.

Live and learn.
richyfenn on 24 Jan 2013
In reply to The Lemming:

With that scope you should see at least a grey disc and probably some cloud bands, not blob. There's four reasons why you may be seeing a 'blob'.

1) You not focusing properly. - Unlikely.
2) The mirrors are not aligned properly. - Likely if new and has been knocked around a little.
3) Poor atmospheric conditions. - Also likely, did you notice if the stars were twinkling a lot? That would make for poor "seeing" and magnification levels will need to be kept low for best results.
4) Scope not cool enough. - Has the same results as 3, if the scope is warm then the mixing of warm and cold air in the tube will disrupted the path of light, just like heat haze rising from a hot road. Try to leave the scope outside to cool for at least half an hour before going for high magnifications.

I have a 200mm scope with a focal length of 1.2m. With a 6.7mm eyepiece and a 2x barlow I can get 358x out of it, but only good results come when all four points above are spot on.

Look up "Collimating a telescope" to check your mirror alignment, like here:
http://www.skyandtelescope.com/howto/diy/3306876.html

Don't disregard low magnification, high mag's often give diminishing returns, which then makes you want to by a bigger scope ;-)
The Lemming - on 24 Jan 2013
In reply to richyfenn:

Thanks for the reply. My scope is collimated to the best of my abilities with a Cheshire thingie. :-)

As for the sky last night, it was clear of clouds, however there was possibly a crystal haze high up. It was fooking cold and I'd been out for almost 2 hours playing in my garden. Not a dark place by any stretch of the imagination.

Yes I did get a grey disc, rather than a blob which dampened my enthusiasm quite a lot. Focusing was very tricky indeed however I've been given some advice to use plumber's tape to go around the thread of the mechanism to make focusing more smooth.

I think that I'm asking too much from a small telescope in a small garden with a lot of light pollution. So the 5mm is going back and I'm replacing it with a 15mm.

Looking at the moon last night with my two kit lenses was breath taking. :-)

Live and learn. Once again the UKC collective is the font of all knowledge.

Cheers dudes
richyfenn on 24 Jan 2013
In reply to The Lemming:

Glad to hear you got the collimation down :)

The rule of thumb is "twice the diameter of the primary mirror in millimetres is the max magnification".

So for you this would be 260x, which is what you were pushing with the 5mm + barlow. Without perfect conditions it wouldn't be great, but the eyepiece on its own (130x) should have shown detail.

I found a review on www.telescopereviewsuk.wordpress.com,
"Now with a nice cold scope back to Jupiter, the reward for letting the scope cool was a view of Jupiter that was not only sharp but full of detail. At only 65x well-defined cloud bands with irregular edges could be seen on the planet in moments of good steady air."

I think you have been unlucky with the weather. If you definitely want to swap the eyepiece, maybe go for a 5.5mm giving you a mag of 118x and 236x with barlow, this'll mean you hit the magnification barrier less often.
The Lemming - on 24 Jan 2013
In reply to richyfenn:

Thanks for the suggestion, however Jupiter won't be in the sky for ever and I think that I will get more use out of a 43x magnification 15mm eye piece. Mr Barlow can always come out to play when the need arises.

Cheers
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richyfenn on 24 Jan 2013
In reply to The Lemming:

Fair enough, but bear in mind that Saturn will be up and about at midnight in a couple of months (but quite low). If you not seen that through a scope yet, just you wait.

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