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Some thoughts as I wait for my scope to arrive...


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Hello all - I'm a newbie to telescopes but a longtime lover of all things astronomy.  My fiancée and I have bought a Skywatcher Heritage 130p (thanks in no small part to the advice I found on these very pages when I was Googling for reviews/advice, etc. - thanks!) and we're just waiting for it to arrive in the post. 

I have been reading up on how best to start stargazing and what gear is best to begin with; aside from the scope itself, would you recommend anything else?  Would a copy of Turn Left at Orion or Philip's Stargazing 2014 help us as complete beginners to the hobby?  I have the Google Sky Map app on my Android phone which I would imagine would come in handy, but I'm not sure whether it'll actually assist me get to grips with the whole experience.

I've also been reading masses of information and opinions about Barlow lenses and supplementary eyepieces for the scope (the Heritage comes with 10mm and 25mm eyepieces); would it be worth my while investing in a 2x Barlow or a 6.5mm eyepiece as well, for example?

Or alternatively, would it just be best to wait patiently (never was my strongest point...) until the scope arrives and try it out on our own with a few bottles of red wine and big coats on some night, and see how we get on unaided?

If anyone can throw out some thoughts on these questions it would be much appreciated.  Best wishes from chilly Ireland!

Réaltóg

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Hello all - I'm a newbie to telescopes but a longtime lover of all things astronomy.  My fiancée and I have bought a Skywatcher Heritage 130p (thanks in no small part to the advice I found on these very pages when I was Googling for reviews/advice, etc. - thanks!) and we're just waiting for it to arrive in the post. 

I have been reading up on how best to start stargazing and what gear is best to begin with; aside from the scope itself, would you recommend anything else?  Would a copy of Turn Left at Orion or Philip's Stargazing 2014 help us as complete beginners to the hobby?  I have the Google Sky Map app on my Android phone which I would imagine would come in handy, but I'm not sure whether it'll actually assist me get to grips with the whole experience.

I've also been reading masses of information and opinions about Barlow lenses and supplementary eyepieces for the scope (the Heritage comes with 10mm and 25mm eyepieces); would it be worth my while investing in a 2x Barlow or a 6.5mm eyepiece as well, for example?

Or alternatively, would it just be best to wait patiently (never was my strongest point...) until the scope arrives and try it out on our own with a few bottles of red wine and big coats on some night, and see how we get on unaided?

If anyone can throw out some thoughts on these questions it would be much appreciated.  Best wishes from chilly Ireland!

Réaltóg

Realtog.........Hi, Try it all out first, but you will probably want to better your lowest focal length eyepiece at some stage, to get a brighter and wider field of view. Also have you downloaded Stellarium. its F R E E. It works in real time, so you can plan ahead, even print star charts, test lenses for fields of view. Try the scope first on its own merit. But get the freebie if you haven't already.

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Charic, thanks for the input!  Stellarium is downloading and installing as we speak, looking forward to trying it out.  It's pretty sunny and cloud-free here where I am at the minute, so hopefully the scope arrives today and I can try it out this evening :laugh:

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TLAO is by far the book I use more than others and I have bought many a book for reference...

For me its the most complete book to give you a basic insight into the whole 'stargazing' journey....based on what you will see and find in practice....I could almost put my others in the bin for what I use them...

It helps avoid the dissapointment you would get form imagining you will see HUbble like images, to give you what a different eyepiece or scope should be seeing for the majority of the DSO/clusters etc you will want to look for...

Enjoy the new scope.......

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I'd agree with Charic - I got a 5mm BST EP for planets as my first extra eyepiece. This was a mistake; the lowest magnification is much more useful. The 5mm is good, but I just don't use it very often. I use a 30mm Vixen NPL, but a 25mm BST would give a very similar actual field of view. 

I find chances to use more than x130 - what the 5mm gives - with the 130p are limited, and I only do that with splitting double stars really.

And I thought TLAO was a very good introduction - and the drawings really help you figure out what you're looking at.

Going out andusing the Mark I Eyeball is a good idea if you've got a sky dark enough. Last weekend I was able to spot the Andromeda Galaxy, Double Cluster and Beehive Cluster from a not-very-dark location, and that was quite fun. Wrap up warm though!

Edited by AndyWB
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Tell me about it Andy - it's brass monkey balls weather here at the minute, especially at night.

Re eyepieces, every time I think I understand the concepts of magnification, eye relief, high/low power, etc., etc., I get lost again.  Am I right in thinking that the likes of a 5mm eyepiece will give high magnification but a small field of view and low eye relief?  If so what would a 5mm, 6.5mm, etc., realistically be useful for on my 130p dob?  Lunar and planetary viewing?

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Welcome to SGL Realtog!

From the info & advice I've gained from other users, I'm probably going to go for a 5mm myself at some point - for lunar & planetary. Having said that, I still find the choices pretty confusing. Relying on the knowledgable people on here to keep me right. The EPs with my own scope were basic but certainly enough to get me up & running. I have an Explorer 130m - first sight of the moon through it was a BIG improvement over the binos.

As advice above, just try the scope as it is. If you're anything like me it will be more than enough to keep you busy for a while!

Let me know what you decide regarding the eyepieces.

Tom

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Hi Realtog,

Rule for calculating Magnification is: Focal Lencth of the scope in mm (should be printed somewhere in the scope)/Focal length of the eyepiece in mm. 

For example, my Celestron 127 Mak has a focal length of 1500 mm, so with my 25mm eyepiece, I get 1500mm/25mm = 60x magnification.

So the smaller the focal length of the eyepiece, the greater the magnification, although it's probably also worth considering that the maximum practical magnification is 40-50x per inch of aperture, so for my Mak, this is approx 250x.

The actual field of view you get is determined by the apparent field of view (specific to the eyepiece)/Magnification.

So for the 25mm plossl eyepiece above, which has an AFOV of 50 degrees, my true field of view would be 50/60 = 0.83 degrees. 

Therefore the field of view will vary depending upon the magnification, which in turn depends upon the focal length of the scope - in broad terms, the shorter the focal length of either the scope or the eyepiece, then the wider the true field of view will be, but the FOV of the eyepiece itself is part of the calculation.

Hope this helps.

CJ

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Am I right in thinking that the likes of a 5mm eyepiece will give high magnification but a small field of view and low eye relief?  If so what would a 5mm, 6.5mm, etc., realistically be useful for on my 130p dob?  Lunar and planetary viewing?

Yup, that's right - high mag, small field of view. And yes, 5mm is perfectly usable - indeed, it's my primary planetary EP in the Heritage 130p. It gives x130 magnification. Often you'll have to wait a bit for moments of good seeing, and the focus needs to be accurate, but it works nicely. I also use it for double splitting a fair bit. The 5mm with a x2 Barlow, though, is too much - you'll never get the focus right, and on the moon all I see are the floaters in my eye.

I also use an 8mm a fair bit too - more than the 5mm - so a 6.5 might be a nice split between them. Or get one and then the other in time...

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The 130p arrived today and we took it out an hour ago...wow. The moon through both 25mm and 10mm was brilliant, and Jupiter with 4 moons through the 10mm was simply breathtaking. Unfortunately the clouds marched in so we're back indoors beside the fire, but I've just ordered a 2x Barlow and a 4mm eyepiece to go with it. Delighted so far and can't thank you all enough for the help and friendly advice to get us started!

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realtog.........Hi, Your 4mm may be pushing the practical limits?

Your telescope specifications are F-650mm D-130 = f/5? Meaning F= the distance from the telescopes objective/mirror to the image, D= the diameter across the objective /mirror and f= the ratio between F + D 
f/5 Focal ratio, Not too important for visual use, as it describes the speed of a lens for photographic values, but for visual use, it does show something. The F/5 is the ratio of the  telescopes focal length to diameter of the telescopes objective/mirror. you can try this on a piece of A4 paper? 
Draw six touching circles in a straight line, about the size of a 2p piece. you then draw a straight line from the 12 o'clock position of the first left hand circle to the 3 o'clock position of the last circle, then draw a line from here back to the 6 o'clock position of the first circle.
Do the same again with another line of identical sized touching circles, but this time, only draw 4 circles. Then mark the same way as above from the first circles 12 o'clock position, to the last circles 3 o'clock then back to the 6 o'clock position of the first circle. Then compare the two images?
If you have drawn correctly, what you should see is two tapering cones, widest at the left, tapering  to a point on the right. The 6 circles represent f/6 and the 4 circles represent f/4. You should see that the cones are tapered differently between the two drawings. The point of the cone is where your Eyepiece fits. you'll  often hear mention of fast scopes needing more expensive lenses because of the higher f/ numbers. Well its all to do with the angle of this cone of light. f/6 to say f/4 are the faster telescopes, and require some considerations in EP(eyepiece)  choices. whereas lower focal ratios of say f/8 to f/6 are less than critical and will tolerate a wider choice of EP's at less expense.
Your telescope also has limits to its use, by the very nature of its build and quality. The EP's that you install wont make the image any better than what the telescope can provide to the EP. The EP only magnifies the image at the focal point. So correct alignment (collimation) of the mirrors, living in a vacuum, and no atmosphere to peer through, you could achieve perfect results up to the physical limits of the telescope. Still with me!
Your telescope is capable under those conditions to achieve 260x power/magnification using a 2.5mm EP and you could quite easily go to 41mm for your low power views. But  limits vs practical, practical wins!
Your supplied 10 &25mm lenses are most probably Kellner Modified achromat designs. Good in their original Days, but can be bettered today, hence the extremely busy market for telescope accessories including better lenses. and you pay for what you get. As you can see from my signature, and in order of purchase, I've invested in the BST Starguider range of EP's Their very good, great value, good eye relief and AFOV of 60°.
My recommendations for you are to get an 8mm BST and the 15mm BST available from Skies_unlimited. If you don't like one or the other or both, you can refund, speak with Alan first! I'm sure you will like them both. That would give you  8, 10, 15 & 25 mm collection, then possibly a wider EP later. BST's only go to 25mm.
Take your aperture and double it. 130 * 2 = 260 .... 260X is the theoretical power limit of your telescope. I have a 200mm aperture giving 400x. but I wont be using 400x ( due to practical issues, such as UK WEATHER and ATMOSPHERICS)
260x power on your telescope is with a 2.5mm lens. That's pushing the limits, and the lens will be difficult to use. A 5mm BST would work, and if you 2xBarlow the 5mm it would save you having to buy a 2.5mm, plus the Barlowed 5mm would have better eye relief. But No, I would suggest get the 8 & 15mm BST's.
The BST's have good eye relief, nice and bright, fairly flat across the image and wide views. If BST were to make a 10mm then the TFOV (True or Telescope Field Of View would be 0.92° against  your 10mm's 0.76° and if using your 25mm giving 1.92° the BST gives 2.30° So the views are visually wider, brighter, and better than the supplied EP's. Everything has a sweet spot, so does your telescope? That is about 65x - 33x power/magnification which equates to somewhere between 10mm and 20mm EP so your middle ground there would be the 15mm BST, but the 18mm is very good too! And when you want to go wider, I would suggest a 32mm lens ( Anther brand as BST's  stop at 25mm at present?)
The 2xBarlow you have bought multiplies the physical length of the telescopes focal length, VIRTUALLY? so your F-650 becomes F-1300 [Effecting that cone of light?]  Multiplying the Focal length by the EP focal length gives you the magnification. Fitting the 8mm gives you 81.25x Power/magnification. Fitting the Barlow now produces the same 8mm lens, but at a higher magnification, and better eye relief than fitting a 4mm lens alone. so the 8mm now produces 162.6X power/magnification from the 8mm. Often described as reducing the Eyepiece or halving the eyepiece, but whatever eyepiece you install, its still the eyepiece you install, only at a higher magnification, due to the Barlow effect on the telescopes focal length. Also the higher the magnification (EP Lower [smaller] numbers) the narrower and slightly darker the views, conversely the lower the magnification (EP Higher [larger] numbers) the wider, brighter the views.
If you purchased the 5mm BST it would give you  130x power, but if 2xBarlowed would hit 260x power as I mentioned earlier. This could be achievable on those special nights that sometimes pass by.
I wish I had a £1 for every BST EP that's bought, but I have no affiliation whatsoever. But I do like the guy (Alan) Very pleasant to do business with, always seems to have time to talk. Others recommend too.
Hope this short note  helps a little.
Edited by Charic
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Hmm. The 4mm might be a bit optimistic. I do sometimes barlow my 8mm to achieve the same magnification - but it's very fussy on focusing, and needs excellent conditions to be usable. Still, my best view of the Great Red Spot was at x160, in such excellent conditions!

Personally, I never barlow my 5mm - x260 is too much for my scope.

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Charic and Andy, once again thanks for the great input.  Before reading your posts I had already ordered the 2x Barlow along with a 6.5mm eyepiece (changed my mind last minute from the 4mm, and after reading these posts I'm glad I did that).  I'll try these out when they arrive and be sure to post back.

I collimated the scope this morning, but during the process had a bit of a Laurel & Hardy moment - the primary mirror fell out!!  If only some of the more seasoned astronomers here could have seen me, in my prime on the living room floor, trying to secure it back into place (nightmare job).  I imagine, as a guitarist, that I would have looked like the equivalent of someone who has never held a guitar before, having just bought their first serious model and trying to tune it by ear.

Once I stopped laughing I got it sorted, no damage done at all, and I tested it on some local birds (the feathery, winged type...) with the 25mm and all looked great.

I'm gigging this evening (the weather here is dismal anyway) so I won't get a chance to try it at night until tomorrow/Sunday, weather permitting.

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I've only just used my new bst 4mm wa ep out on the moon the other night with my heritage. This gives me 163x and my view was amazing,the closest I've managed with this scope. I got this ep,specifically for the moon.

Clear skies to you all :-)

can you let us know how you get on with the 4mm on Jupiter/Saturn as I'm thinking off getting that size, instead of barlowing my 10mm to 5mm for better image quality.

Thanks

Sent from my iPhone using Tapatalk

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