I spotted Jupiter and got excited when I saw one of its moons - but turned out it was a shadow from my telescope!!

[Moonfromthetrees]

Hello all,

Very newbie here!!

As the title suggests I was out last night viewing Jupiter using a very basic National Geographic Dobson telescope. After spending ages trying to get Jupiter into my field of view, I managed to eventually get there. I found it difficult to keep the telescope steady. Aside from this, i eventually managed to get a great view. I was using a 2x Barlow lens, which came with the scope. However, i found that there was a shadow of ball attached to a screw cutting across my view of the planet, which was really annoying. I presume this is not normal, but can't work out how to get rid.

 

Help much appreciated!!

 

Thank you

[Stu]

55 minutes ago, Moonfromthetrees said:

Hello all,

Very newbie here!!

As the title suggests I was out last night viewing Jupiter using a very basic National Geographic Dobson telescope. After spending ages trying to get Jupiter into my field of view, I managed to eventually get there. I found it difficult to keep the telescope steady. Aside from this, i eventually managed to get a great view. I was using a 2x Barlow lens, which came with the scope. However, i found that there was a shadow of ball attached to a screw cutting across my view of the planet, which was really annoying. I presume this is not normal, but can't work out how to get rid.

 

Help much appreciated!!

 

Thank you

It sounds very much like your scope wasn’t focused properly. When this is the case, you see the shadow of the secondary mirror in the middle of the unfocused star or planet. I would try again, and focus so that the planet appears at its smallest, then the shadow should go away.

[wookie1965]

You did have an eyepiece in the barlow didn't you, the screw should not have been in the FOV if its holding the eyepiece in.

Edited September 28, 2022 by wookie1965

[Moonfromthetrees]

Thanks for your help. From doing some online research it seems that it was probably the focus. But I enjoyed looking at the large version!! Couldn't make out much of the planet when it was at its smallest.

[Moonfromthetrees]

Yes, I had an eyepiece in the barlow. Thank you.

[AstroKeith]

20 minutes ago, Moonfromthetrees said:

Thanks for your help. From doing some online research it seems that it was probably the focus. But I enjoyed looking at the large version!! Couldn't make out much of the planet when it was at its smallest.

Hi,

Welcome to SGL. Yes you are seeing the secondary mirror on its stalk. As others have said, focus until Jupiter is the smallest.

However - expectation management needed here! With your scope planets arent the best targets, although the moons of Jupiter should be nice, and Saturn should show its rings, just. Unlikely that you will see any detail on the planets.

Your scope is better suited to larger targets like Orion Nebula, the Pleiades Andromeda Galaxy etc.

[allworlds]

Yeah, that was way out of focus.

Which scope is it (Nat Geo put their branding on a few) and what eyepieces do you have?

[Louis D]

Is your scope the National Geographic 76mm Compact Reflector Telescope?

[Moonfromthetrees]

Yes, it is. 

[Moonfromthetrees]

This is a poor picture of what I could see. It doesn't capture the shadow I'm talking about, but I was taking a photo with my phone through the eyepiece which is why only half is visible. 

[Louis D]

Yeah, that's way out of focus.  Next time, turn the focus wheel(s) forward or backward as much as needed to minimize the size of that white spot.  If you center it at best focus (smallest and sharpest image), you should see Jupiter's main equatorial belts and its 4 Galilean moons.  It should look a bit as below through your scope:

Of course, it will appear tiny to your eye:

Edited September 29, 2022 by Louis D

[allworlds]

I have a similar, though not identical, scope. When you get Jupiter in focus, with a bit of luck you might be able to see the two main belts across it, and up to 4 moons. What helped a lot for me was an aperture stop - just a piece of card with a hole, try 50-60 mm diameter, cut in it and taped to the front of the scope. This reduces the spherical aberration, a blurring at medium and high magnification that these small cheap scopes suffer from because they use spherical main mirrors. But still a scope like this will only ever show a planet as a small disc with some general markings.

[Moonfromthetrees]

Thanks for all your help people. That was really useful. Need to lower expectations! 

[JOC]

If you haven't found it take a look at this thread 

even if you only look at the pictures on the first page.  Those pictures are what you can expect to be able to see with a far larger telescope than the table top version you have. - you views won't be as good as those pictures, but I think the thread will help.  FWIW you may have been better taking advice on SGL before spending your cash as I feel sure you could have bought something much better second hand than what you've ended up with.  Unfortunately all the hype and marketting that places like Nat. Geo. are so good at means that folks like you have their expectations raised sky high and fall at the first hurdle the moment they look at their first object.   They sell you all the stuff that sounds good like 'Barlow' and 'moon filter', but many people find they don't need either - I can cope with the brightness of the moon and the barlow will probably overegg the magnification to way beyond what is useful.  In reality I doubt you will get good use out of any of it.  Let's hope it doesn't put you off life and you end up wanting some better kit 🙂

[DaveL59]

You'll also find that the supplied eyepieces aren't all that good, I have the same scope bought as it was offered for £10 and never used. A couple of reasonable Plossl's will do much better but you're always going to struggle to track as it doesn't move well on its mountings. I flocked the inside of the OTA and did some tweaks to the focuser but there's a limit to how much you can improve these, you can't collimate well as the primary mirror isn't adjustable, for example. Still, as a starter it works and if you reach a stage you want something better give a shout here for some advice 😉 

[PeterStudz]

Although I agree with what’s being said a few things from my limited experience.

It’s good to hear some enthusiasm! Don’t give up. There will be disappointments but if you stick at it great rewards.

I started off getting a telescope that was rather small and on a very wobbly tripod and mount. I later ended up getting a far better and suitably sized telescope but despite some of the things said I had lots of fun and learnt a lot from that first telescope (my daughter too) - eg I took simple smartphone pictures. Learnt to use an EQ mount. Viewed the sun using a small solar filter. Upgraded the mount and tripod in order to make it into a quick grab-and-go. The telescope is now a joy to use. Took it on holiday in an aircraft in a small suitcase to a truly dark location. Ended up seeing things that I just can’t see from my light polluted back garden even with an 8” Dob. 

And the picture above with Jupiter at 100X. Sure it’s small but remember that your eye is right up against the eyepiece. That’ll make it seem kind of larger - you’re not looking back as you are looking at it from a computer or smartphone screen.