Telescope and stuff help

[Denni]

Hi all,

I have hijacked my friends telescope for 2 months and as he is away, he has let me use his SGL log in to ask a few questions, so please bear with me as I have only used a telescope for the last 2 weeks

He has a Skywatcher 705. So far, I have had great views of the moon and I have seen Jupiter and its moons albeit a bit blurry depending on which EP i have used.  He has the standard EP's that come with most telescopes (10 and 25mm), a x 2 barlow and a 17 mm Antares Plossl EP which I have been using most of the time.

Now here are the questions!  So it has a 70mm aperture with a focal length of 500mm and I have been using the barlow and changing between the EP's to try and get better views. Can someone suggest what EP's  I could buy, either bigger or smaller mm, to better enhance my views of planets and the moon as I realise most telescopes have their limits and I have no idea what EP/barlow combo would make it better or worse on this specification telescope.  Also, would it be better without the barlow lens sometimes? 

Secondly, the 45 degree viewer supplied is really good but I have already realised, tonight especially looking at Jupiter, that it could do with a 90 degree viewer. Can somene recommend a reasonably priced star diagonal that corrects both up and down and if possible, the left to right view?

Lastly I promise, when people talk about magnification, do they mean the movement of the tube by the wheels and if that is the case, for example, 50 x magnification would mean the tube would be half out? I know nothing about telescopes at all but I am really enjoying looking at things both night and day and am getting up early to have a look at Saturn!

Anyway, really sorry for the basic questions but I could do with some help and greatly appreciate your time and efforts.

Elsie

[Langy]

Hello Dennis friend.

My first query really is that if you are only borrowing the scope for two months then why go out and buy more EP unless you intend to keep these for when you buy your own scope? If you want something descent to add to the collection then they will not be cheap,

Someone better will advise on the equipment but I can give a little help on the magnification. To calculate the magnification take the focal length of the scope and divide the EP length into it. For example you say it has a 500mm focal length and using the 10mm EP will give 50x magnification, 25mm will be 20x.

Hope I've been of some help.

[ScottS]

When you say "the movement of the tube by the wheels", that would be the focuser that the eyepiece sits in, and it does just that, simply focuses the image. The magnification is supplied via the actual eyepiece and is calculated as above.

[Denni]

Hi Paul and Scott,

thanks for the replies, really appreciate it. Yup, that is the focuser then on the wheels! and thanks for the heads up on the magnification, makes sense when you know.

I am intending to buy the same telescope and will keep the EP's for myself so just wanted to know if I should buy some bigger ones or some smaller ones to help me get a better more detailed view.

I understand the magnification now but  i'm presuming the telescope will have a certain EP size  limit because of it's focal length?

Thanks again, fascinating stuff!

Elsie

[ScottS]

If you haven't already, have a read of this thread. It may be useful to you regarding eyepiece choice.

[Langy]

Your welcome Elsie

I don't know anything about the scope as I'm new here too. What I have found out though is that it's more important on finding what's out there and how to find it first. Eventually you can decide on what you want to find, if you want to do AstroPhotography and that all helps with what you decide to buy.

Most stock EP tend to not be very good quality, for example on my cheap scope I have the 20mm and 10mm where I am very pleased with the 20mm as it's so nice to view items like the moon and Pleiades (seven sisters) as well as panning around the sky. The 10mm I've not been very happy with as I wear glasses and the EP is not very favorable for the specs wearer, so I bought an 8mm in a range that was recommended to me of which due to weather I still have to try out. Overall magnification isn't the thing you need to worry too much about, but there will be times when you need more and sometimes less.

If I was in your position I would have a few sessions with the current kit, have a read around the forums for what people do, oh and as I'm sure you will get hooked on this hobby create your own SGL account, especially as it's free and you can easily look back for your posts etc when you need to look them up.

Good luck I'm sure this post will soon get a lot of replies from the very friendly bunch on here.

[NGC 1502]

Hi Elsie.  Perhaps you could give an idea what your budget is for eyepieces ?    The supplied eyepieces are ok to get you going, but if upgraded the view usually improves.

Best not to over magnify, better a smaller but sharper view than bigger but fuzzier.  A 5mm eyepiece would give 100x and give nice planetary and lunar views.

Don't forget that a nice low power gives good views of large objects like the Pleiades star cluster. A 25mm will give 20x, just right for that.

If you get a standard 90 degree star diagonal, it will give a right way up but left / right reversed view. That's normal for a refractor.

"Correct image" diagonals are available, but best avoided as most degrade the view.

HTH, Ed.

[Denni]

Hi folks,

thanks again and appreciate the link to the very long and informative thread on EP's, that needs a cup of tea and a packet of digestives to read!

Ed, thanks for the advice, I was going to spend about £25-30 on a 90 degree viewer and I was looking at a 5mm Ostara plossl which is £20. I was also contemplating getting a medium sized plossl, a 10mm one which is also an Ostara model again at £20.  So maybe about £60-70 in total but I have this in my paypal account waiting for me to spend it after selling some old ski kit :0)

With the EP's above, would a barlow lens compliment them or make the view worse with the doubled magnification? The one Denni has is a bog standard  but I think good quality x2 barlow and I've been using it with the 17mm Antares plossl that he has and his moon filter with decent results.  Also, I wear glasses so does it matter what EP to use or does wearing glasses make viewing worse?

One thing I have noticed is that his standard EP's have a fairly large lens area and the Antares plossl one has a small pinpoint lens, does any of this make a difference?

Thanks again, Elsie

PS, Just had a grand view of the moon again and Jupiter with its moons although I need to invest in that 90 degree viewer fairly sharpish as I was nearly lying on the floor! Also, I have just been playing with a camera mount from Astro engineering that Den has and is very simple to use but I'm having problems focusing the moon correctly and getting my camera lens centred exactly in the EP lens. Best to try it out in the daylight I reckon. It is one of these:

http://www.scopesnskies.com/prod/Astro-Engineering/Ultra/PH047.html

[Langy]

Hello again Elsie

The link below is what I created a little while ago about getting a new EP in one of my options. You can see that I was advised against the Plossi as their eye relief distance reduces with the magnification of the EP. As I said, I'm new so have a read of that topic first and ask some more questions, you may need to end up creating a new topic for specific questions and you may get more answers from people who know more about a particular subject.

The 8mm I have bought has a really wide opening, that did cost £49 but if you just compare it to the stock EP and I haven't used it yet the weight is far more, it's a lot wider at the eye end and the EP lens for where you put your eye to is really wide, ideal for a specs wearer. I would rather pay that money on one EP and get the quality from it rather than 2 items which later I will be disappointed with.

http://stargazerslounge.com/topic/207982-what-upgrade-next/

[Denni]

Good advice Paul and thanks for the link, will have a look at that. 

I was told that Plossl EP's were generally better so I suppose if I could get one with a big lens area that would help?

I'm happy to take advice and spend more on a better more suited EP rather than buy a couple :0)