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spaceman spiff

spaceman spiff

Posted
Posted

:oops: Hope you will help

Sorry if they sound daft questions, I am a beginner after all :hello2: I have read the manual but seem to be missing it each time

1 - I have the Skywatcher Explorer 130pm (only got it 2 week ago) The dust cover has a smaller viewing cap on it, why? I know I can hear you laughing why hasn't the idiot tried it, I did still couldn't fathom out why

2 - Up to what magnification eyepiece could I use with or without the Barlow Lense that comes with it?

3 - Which is the best Astro magazine for amatuers? BBC Sky at Night seems a bit to heavy at the moment

Thanks

Pete

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philsail1

philsail1

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Posted

Peter,

Hello and welcome to "Stargazers Lounge" forum! You will receive plenty of help, advice and encouragement here!!

I had a Skywatcher 130p Newtonian. Absolutely great telescope to start off with (and no reason not to keep for good! (I wish I had kept mine!!)).

The small removable round cap can have a number of uses.

1. You can remove it, swivel the main cover around until the small hole sits between the thin arms of the secondary mirror support, and then use the scope to view bright objects such as the Moon, Jupiter, Venus and perhaps a few of the brighter stars - BUT NOT THE SUN!.

2. You could make another cap to fit the hole, cover the front of the new cap with a small piece of "Baader" filter foil, fit the cap over the hole and then use your scope to view the Sun. IF YOUR SCOPE IS FITTED WITH AN "OPTICAL" FINDER SCOPE, REMOVE IT BEFORE LOOKING AT THE SUN - JUST IN CASE SOMEONE INADVERTANTLY GLANCES AT THE SUN THROUGH THE FINDERSCOPE. THERE IS A SERIOUS RISK OF PERMANENTLY DAMAGING ONES EYE.

3. if there is another "blank" fitted directly opposite the removable one, you can cut this blank out, and use the two holes as a "Hartman Mask" (you will have to look it up on the internet for details) and use your scope to more accurately focus on a planet, or brighter star.

With regards to what max magnification you can use with or without the supplied Barlow.

Well, you should have a 10mm eyepiece, and a 25mm eyepiece, and a 2x Barlow.

The scope has a focal length of 900mm so the 10mm will give you a magnification of 90x (brings whatever you are looking at 90 times closer, or makes it 90 times bigger than you would see it with the naked eye).

The 25mm will give a magnification of 36x.

Using the Barlow just doubles those magnifications. (180x with the 10mm, and 72x with the 25mm).

The usual way to calculate what maximum magnification any scope can go to is by allowing a magnification of 50x for each "inch" (or 25mm) of a telescope's aperture (size of mirror, or objective lens - front lens). So for the Skywatcher 130pm you should reach a magnification of 260x (130mm divided by 25mm = 5.2 x 50 = 260).

A magnification of 260x could only be used on the clearest and stillest of nights, and focusing would be quite tricky. You would get good views of the Moon, at that magnification, and although you would see Jupiter, Saturn and Venus bigger, getting a "crisp" image would be very difficult at that high of a magnification. (I do not often use such a high magnification even with my 8" Skywatcher!). Most times it is better to use a moderate magnification and see more detail.

Best Astro mag - I think they are all bordering on the technical really, with all of them containing a few articles for beginners.

A really good book for starting out in Astronomy is "Turn Left at Orion." It contains good clear drawings and instructions on how to find your way around the night skies, and what you are likely to be able to see with the size scope you have.

Hope this helps,

Best wishes,

philsail1

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AJSullivan

AJSullivan

Posted
Posted

I'm new to this as well, but i can answer the magnification length i think.

The length of your scope is 650mm. Unless you have VERY clear nights, I believe I read somewhere you don't really want to go over 200x magnification. Take your focal length and divide it by the length of your lens (6mm, 15mm, 25mm etc). This will give you the magnification.

Example: 650mm / 6mm = just under 110x mag (108.33.)

650mm / 15mm = 15mm = just under 45x mag (43.33.)

Hope that helps.

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philsail1

philsail1

Posted
Posted

Alex,

You are perfectly correct. The Skywatcher 130pm is indeed 650mm focal length.

I have given the wrong info - must have had a mental abberation!

I do apologise there for confusing someone just starting out.

Thank you for correcting me.

Regards,

philsail1

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algol

algol

Posted
Posted

i also have the 130pm mate and love it.

in terms of mags, i think that sky at night is the easier one to get into, more amateur friendly than astronomy now, which to me seems a bit heavier. plus S@N has the better monthly gude IMO.

i think the max you should use is 2x your aperture so 260x for this scope but as mentioned 200x is prob about the max.

so yeah, enjoy and have fun.

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Astro_Baby

Astro_Baby

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The small removable cap is useful for planets as stated. Basically what it does is increase the focal ratio ( f number ) of the scope. ie focal ration without the caps is 650( focal length) divided by 130 ( diameter of primary mirror/optic ) that gives an f ratio of f5.

With the lens cap on and the small hole removed you have an effective primary optic of probably about 40mm so you now have 650 divided by 40 giving an f ratio of about 16 ie f16.

The second 'blank' cap is what you hang the removable one on when you want to store it somewhere safe.

Hope thats of help.

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TheThing

TheThing

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You've choosen a great scope there. I also started with a 130 (the 'm' version) and rue the day I traded it in for an ETX-70!

You'll have plenty of fun with such a great all rounder.

Just remember - The most stupid question is the one never asked! Don't be afraid to ask for help!

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Astro_Baby

Astro_Baby

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Posted

I miss my 130PM as well and wish I hadnt had to sell it. I could lug the whole thing downstairs in 10 minutes. The 200 requires four trips up and down the stairs and I have found I am now relecutant to use it unless I can be guaranteed at least 2 hours of viewing or else its too much bother.

The old adage that the best telescope is the one you use most frequently is very true. A lightbucket with big apertue is all well and good but if you never use it you may as well buy some new shoes.

By the way Thing - whats wrong with the ETX70 ? Just curious.

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TheThing

TheThing

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(With apologies for hijacking the thread!)

The ETX-70 was just a pain. On the first one I had, the motor developed a serious problem within weeks of getting it. Luckily, it was just replaced.

The main problem is that, as it's an entry level scope, the database and the goto aren't up to much. No matter how hard I tried, I could never get it aligned, which rendered the goto useless! The optics were pretty good, but with no finder it was very much point and hope! Then it becomes a struggle to use, so it didn't come out all that much. Would have been better with new shoes!

Really, really wish that I hadn't traded the 130m in for it!

Still, I sold it for a pram for my little boy, then got given a 5" Helios short tube refractor which I swapped for the Tal I have now (and the Tal is as good as the Skywatcher! :cheers: )

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