help with my first telescope

[riverrik]

I bought my first telescope a few months ago, a celestron firstscope 76mm c21024.

I was viewing Jupiter the other night and started working my way through the lenses eventually getting down to my 4mm lens with the barlowx2 lens. I found it extremely hard to focus it. should I be using a different magnification lens with the barlow or is it just because my telescope is basic?The sky was really clear that night and jupiter and the milky way were an amazing sight even without the telescope! I'm hooked on this stargazing now and any advice would be greatly appreciated.

[ronin]

Way too much magnification for the scope, it just is not going to work with a 4mm and a barlow.

The scope is also f/4 and the collimation is critical.

At f/4 the eyepieces will also need to be good, by good and for f/4 many look to TV plossls at about £80 a piece. This is just too costly for that scope.

Really I would consider a 5mm or 6mm only, however they still have the problem that plossl's will not be good (generally) on an f/4 scope. Also you have to get very close to them to see anything, however you already have and use a 4mm.

Unfortunately the ultimate advice is a bigger and more advanced scope as the Celestron is intended as a first step and therefore has it's limitations.

[Marki]

Jupiter is also one of those targets where sometimes you can have too much magnification. I find sometimes that if I go above a certain level I'll actually lose the detail and the image becomes mushy. Precisely where that point is can depend on the scope itself and the seeing conditions. I wasn't seeing any more detail last night with my 5" refractor at c. x140 magnification than I was at c.x120 (and that wasn't much better than the image I was getting at x100 in my 80mm refractor), and when I pushed much above x150 the image began to degrade.

As Ronin says though, the Firstscope will have its limitations anyway.

Bet you get some lovely skies around Castle Douglas though!

[Qualia]

Just to add a little more food for thought, as a general rule of thumb the brightness of an object will decline as you up the magnification. If I up the mag twofold, say, I'm reducing the image brightness by a factor of four. If I keep on doing this eventually details just disappear and planets turn to mush. On the other hand, increasing the mag does make detail more apparent, so, as you can appreciate, we're now at a trade-off: will increasing magnification gain more detail even though I'm making the object fainter?

I've found that playing around with this trade-off - dependent on the evening's seeing (I've found that LP doesn't really affect planets) - does make a difference. Even as little as 1mm increase or decrease in the mag - about 10% to 15% difference of magnification - can be quite surprising. You'll probably find that on a decent night your sweet spot is around 140x to 160x on viewing Jupiter and you will probably only be able to push 200x plus on the most excellent of nights.

You've got a lovely 3" telescope reaching out across the universe some 675,000,000 kilometers and I'm sure - on another better evening - you will be able to see those delicate reddish-brown belts, a darker, greyer hue to the Polar regions, and so on. You'll be able to trace the movement of the Jovian moons and observe their play of shadows over Jupiter in times of transit or of their eclipses by Jupiter's own shadow. From time to time, if you want to enhance that colour of the giant maybe a light blue filter will work nicely, or a Wratten 11 or 12.

If you can, try to sit with Jupiter for a peaceful twenty minutes or so on your next observation session and I'm certain they'll be moments of great clarity and seeing. I've been following Jupiter since late July and every week it gets just that little bit better, the moons are getting brighter and more detail can be tweaked from the planet. Stay with it and as the weeks go by you will notice quite a difference. Maybe it would be nice to try your hand at a little sketch which will also help train your astro-eye.

Good luck and clear skies

[cantharis]

Just to add a little more food for thought, as a general rule of thumb the brightness of an object will decline as you up the magnification. If I up the mag twofold, say, I'm reducing the image brightness by a factor of four. If I keep on doing this eventually details just disappear and planets turn to mush.

Absolutely - the cure of course is to increase your aperture.

[riverrik]

Thanks for all the feedback and advice guys! Its much appreciated! The sky is looking clear again tonight so ill go out later and look at jupiter again using all the tips and advice that i have been given! I know my telescope is limited but it's ideal for me just starting out, then once i've got the hang of using it and navigating the night sky i will be looking to move up the telescope market and ill asking for more of your advice on what i should get! I'm so glad i stumbled upon this website. It's going to be a great help to me! Im lucky enough to live near a Dark Sky forest park which is the process of opening up a public observatory which i can't wait to go and visit! i wish i had got into this years ago! Thanks again guys!

[Qualia]

Thanks for all the feedback and advice guys! Its much appreciated! The sky is looking clear again tonight so ill go out later and look at jupiter again using all the tips and advice that i have been given! I know my telescope is limited but it's ideal for me just starting out

You've got a fine and lovely scope, riverrik. It looks perfect to carry where you fancy and start stargazing and is a great instrument to test the proverbial waters of this hobby, so to say, and learn a little not only of the night sky, but also of physics and optics etc. With a good few months practice if you do decide to upgrade you'll be in a lot wiser position to make that more nformed enquiry and purchase. I'm not sure if it has a finder so in the meantime you might want to get hold of a Telrad at some point. This will be a useful purchase for it'll make your evenings' hunting easier for you and you can always transfer it to another scope with ease if you decide to upgrade.

By way of suggestion, other than observing Jupiter with the 76mm (which may not always reveal its bands of colour with such a scope), while you're in that area of the sky have a look out for some open clusters such as the Double in Perseus, M 45 and Hyades in Taurus, M 35 in Gemini and M 36, M 37 and M 38 in Auriga and if possible the wonder of M 43 in Orion. These should make for some spectacular seeing. You might also want to try your hand at hunting out some of the more interesting features of the Moon's 100. I'm not a big Moon fan myself but I think its worth a little time hunting out these particular gems.

Okay, let us know how your evening's session went and look forward to hearing a new report

[bingevader]

Super advice from Qualia.

I've used a meade etx90 for over a decade, only a little bigger than yours.

The advantage of a small scope is its portability, especially at the moment when there only seem to be 30min windows in the cloud!

But obviously, unless the sky is crystal clear, your expectations need to be a little lower.

I used my 9.7mm ep lots, but only rarely managed to add the x2 barlow and get any more detail.

Yes you get a larger image, but a lot fuzzier!

I still managed to tease out a fair amount of detail without the barlow however, even the giant (?!) red spot on a few occasions.

Another skill to master is that of using averted vision.

Don't look directly at Jupiter, but slightly to the side.

You'll be using the more sensitive rods on your retina rather than the colour sensitive cones in the middle.

It's a skill that takes some acquiring, but does help.

I take my etx with me in the boot of a packed family car on holiday, I'd never manage that with my 8" scope!

Cheers

[JamesM]

In addition to the informed and encouraging information above, you might want to have a look at a little calculator from 'Sky & Telescope' which will advise you on the positions of the jovian moons at any time - you can view it here. Of particular interest is the box at the bottom which is titled, "Table of Jovian Satellite Phenomena" which will advise the times of when the moons will cross in front of Jupiter (creating a shadow across the surface) and when the moons themselves are eclipsed by Jupiter's own shadow - great stuff!

James

[riverrik]

Thanks again guys for all your advice and tips. I was out the other night and looking at Jupiter, i followed your tips and was able to get a slightly less fuzzy image of it. Regardless of how much detail i am seeing , i find it absolutely amazing that i am looking at another planet through my telescope!

The last couple of nights the weather has been bad so i haven't been able to get out. However, next week , hopefully the sky's will be clear as i am planning to head over to the Galloway woods to the dark sky area and do a bit of gazing with my friend who's also a beginner. I'm going to try and focus in on some of the messier objects that you have suggested in your reply's .

I was at a beginners night for stargazing the other week. It was a basic talk on how to navigate the night sky along with a slide show. The guy was giving examples and trying to give us an idea just how big the universe actually is. His last slide was the picture from Hubble that was recently taken of the thousands of galaxies at the outer reaches of the universe. Although i had seen the photo before , i was still amazed. There is so much to see out there and I'm glad that I've taken up this hobby! (although i may need a slightly bigger telescope to see that far! )