Trouble Viewing Planets

[SpaceFinatic]

Recently I’ve bought a Meade Lightbridge 12” plus truss tube. It came with a 2” lens and has a focal length of 300mm. However, when looking at Jupiter, I can’t see it as good as I should be. I see it as if I had a 4 or 6” telescope. I thought it was because of my lens and maybe I need a smaller mm one but am not sure.

I am 62 years old and don’t understand as much as you experienced astronomers do, so any help will be appreciated!

Edited September 14, 2020 by SpaceFinatic

[johninderby]

First of all have you collimated the scope?

If you haven’t you will get poor views and not a lot of detail. The Lightbridge in particuar will need some colimation every time you assemble it.

http://www.astro-baby.com/astrobaby/help/collimation-guide-newtonian-reflector/

[SpaceFinatic]

Thank you for replying, yes I have collimated my telescope. I have a feeling it’s due to my lens. It’s a 2” one

[johninderby]

2” eyepieces are usually low power for use on DSOs etc. For planetary viewing you want 1.25” eyepieces with focal length of say 8mm or so.and perhaps 5mm on the moon.

Starguiders are good budget eyepieces.

https://www.firstlightoptics.com/search/for/starguider/

Or

https://agenaastro.com/catalogsearch/result/?q=starguider dual ed

 

 

[alex_stars]

Hi,

the 12" Lightbridge Plus has a focal length of 1524 mm, 304 mm is the aperture. You got a 26 mm 2" eyepiece along as I saw on Meade's homepage. That places you at about 58x magnification. As John above pointed out, a 8mm would give you 190x magnification, really nice for planets. 5 mm would result in about 304x magnification.

Hope that helps.

[SpaceFinatic]

Yes that helps tremendously, thank you! Would you say a barlow lens is necessary? I’ve heard my pals say it’s great for magnification but I think 190x is more than enough.

[johninderby]

Barlows are more usefull for longer focal  length eyepieces. Turning a 25mm into a 12.5mm can be very useful. Using a barlow on say a 5mm eyepiece will give an unusable magnification in most cases. 

Edited September 14, 2020 by johninderby

[Don Pensack]

A 12" f/5 can use eyepieces from 30mm down to about 2.5mm

Here is how the powers stack up:

48-120x  low power, suitable for large objects and general viewing: focal lengths 32mm down to 13mm

120-240x medium power, suitable for general viewing of most objects: focal lengths 12.5mm down to 6.4mm

240-360x high power, suitable for planets, Moon, double stars, small objects: focal lengths 6.3mm down to 4.2mm 

360x to 600x ultra high power, usable only once in a blue moon for very small targets in superb stable air seeing conditions.  Focal lengths 4.1mm down to 2.5mm

I wouldn't bother to buy an eyepiece for the ultra high powers--if needed, get a 2X Barlow and turn some medium power eyepieces into ultra high powers.

My recommendations for a set of 3 eyepieces on a 12" scope are for multiples of 70x, or 70x, 140x, and 210x.

There would be very few objects not enjoyable to view with those 3 magnifications.  You can add eyepieces as your experience grows and you find you need

a certain magnification you don't have.

On your scope, that is focal lengths of 21-22mm, 10-11mm, 6.5-7.5mm (a variation to allow for a particular model of eyepiece.

I'll let others make recommendations for brands/models/fields of view, but I always advise starting out with at least a 65° field of view so the eyepieces don't 

seem too narrow.

[SpaceFinatic]

Thank you for all the kind people who’ve helped me understand abetter about eyepieces and the steps I need to take to improve my viewing quality! 

I greatly appreciate it.
 

 

[John]

20 hours ago, SpaceFinatic said:

Recently I’ve bought a Meade Lightbridge 12” plus truss tube. It came with a 2” lens and has a focal length of 300mm. However, when looking at Jupiter, I can’t see it as good as I should be. I see it as if I had a 4 or 6” telescope. I thought it was because of my lens and maybe I need a smaller mm one but am not sure.

 

With the planets in their current positions, low down, a smaller telescope is often showing them better than a larger one.

You say that you don't think your 12 inch is showing you planets as well as it should but I wonder what you are judging that by ?

I have an excellent 12 inch dobsonian and some of the best eyepieces but the views of Jupiter and Saturn lately have not been that great with it. My smaller refractors are often showing a sharper and more contrasty view.

When the planets have been higher in the sky, the 12 inch dobsonian comes into it's own and produces superb views of them.

[Geoff Barnes]

Down here in Oz I rejoice in having the planets almost overhead (a bit too high for comfortable viewing if truth be known).

However, even with this advantage the views of them can still be pretty poor, fuzzy and shaky, lacking in detail when the seeing conditions are not good. So even when the planets are low down if you are getting very good seeing conditions you will probably be getting just as good views as I do when my seeing is poor here. Never miss a chance to get the scope out and have a look when the skies are clear, it's always worth it!  

[John]

13 minutes ago, Geoff Barnes said:

Down here in Oz I rejoice in having the planets almost overhead (a bit too high for comfortable viewing if truth be known).

However, even with this advantage the views of them can still be pretty poor, fuzzy and shaky, lacking in detail when the seeing conditions are not good. So even when the planets are low down if you are getting very good seeing conditions you will probably be getting just as good views as I do when my seeing is poor here. Never miss a chance to get the scope out and have a look when the skies are clear, it's always worth it!  

Having observed the planets when they were much higher in the sky Geoff, the impact of their low altitudes over the past few years has been fairly noticeable.

Just have to make the best of it though !

I'd love to transport my scopes and eyepieces down under for a few weeks

[mikeDnight]

20 hours ago, SpaceFinatic said:

Thank you for all the kind people who’ve helped me understand abetter about eyepieces and the steps I need to take to improve my viewing quality! 

I greatly appreciate it.
 

 

Heat plumes from buildings or proximity to tree tops can interfere with the image. You may find that you have certain sweet spots where the seeing suddenly becomes excellent, so it's worth noting these. Then again the mood swings of our general and local atmosphere can change suddenly too, so perseverance is needed. Yet another thing that some observers fail to do is to regularly refocus the scope. As a planet moves across the sky it is viewed through different depths of atmosphere and so the focus naturally and continually changes requiring regular adjustments to maintain critical focus. Very often sharp planetary detail is fleeting, and flickers in and out of view throughout the observation. Actively recording what youre seeing either by making brief notes, talking into a dictaphone, or making a sketch of a planet over a ten or fifteen minute period may reveal you're seeing more than first meets the eye.

There's another simple trick you might try. Deep sky observers will often use averted vision to detect faint detail. This requires that the light sensitive rods, which are situated around the periphery of the retina, be allowed to naturally scan the object on view. Rods too play a major part in detecting subtle planetary detail, and so if you're able to relax and let your eye naturally scan the tiny planetary disk, the rods can pick up on some very subtle detail. Staring directly at the planet can actually be counter productive. So try looking very slightly to one side of the planet while still concentrating on its disk to see if it helps. Don't force it, scanning the disk naturally is the key!

Edited September 15, 2020 by mikeDnight

[Colossal Plossl]

16 hours ago, mikeDnight said:

There's another simple trick you might try. Deep sky observers will often use averted vision to detect faint detail. This requires that the light sensitive rods, which are situated around the periphery of the retina, be allowed to naturally scan the object on view. Rods too play a major part in detecting subtle planetary detail, and so if you're able to relax and let your eye naturally scan the tiny planetary disk, the rods can pick up on some very subtle detail. Staring directly at the planet can actually be counter productive. So try looking very slightly to one side of the planet while still concentrating on its disk to see if it helps. Don't force it, scanning the disk naturally is the key!

I used this technique to good effect with the M31 Andromeda galaxy.

[sputniksteve]

I've recently bought a used Skymax 127, and even with the mediocre eyepieces* that I got with it, the view of Saturn feels better than it ever did with my 12" Lightbridge - even with the 7mm Televue plossl that I used to own (and stupidly sold with the Lightbridge). I acknowledge that it's some years ago that I last looked through the 12", and my eye is probably better trained now too.

*There's a 12.5mm one labelled as Series 500, but no manufacturer. With the stock barlow, this is producing a nice view of Saturn. I can't wait to get hold of a good eyepiece!

Edited September 19, 2020 by sputniksteve

[Louis D]

On 19/09/2020 at 04:08, sputniksteve said:

I've recently bought a used Skymax 127, and even with the mediocre eyepieces* that I got with it, the view of Saturn feels better than it ever did with my 12" Lightbridge - even with the 7mm Televue plossl that I used to own (and stupidly sold with the Lightbridge). I acknowledge that it's some years ago that I last looked through the 12", and my eye is probably better trained now too.

*There's a 12.5mm one labelled as Series 500, but no manufacturer. With the stock barlow, this is producing a nice view of Saturn. I can't wait to get hold of a good eyepiece!

That 12" must have been miscollimated or had a terrible mirror.  My most memorable views of Jupiter were through a 12.5" Mag1 Instruments PortaBall with a Zambuto mirror on an Osypowski equatorial platform at a star party.  I could make out all sorts of festoons and barges in the belts with ease.

[sputniksteve]

9 minutes ago, Louis D said:

That 12" must have been miscollimated or had a terrible mirror.  My most memorable views of Jupiter were through a 12.5" Mag1 Instruments PortaBall with a Zambuto mirror on an Osypowski equatorial platform at a star party.  I could make out all sorts of festoons and barges in the belts with ease.

It's probably my memory tbh. It was well collimated and a great mirror. 

I'd also suggest that seeing and sky quality etc would have made a difference. I'm in Bortle 5. 

I've not yet a good view of Jupiter with the 127. I do recall that looking great through the 12" though.

Edited September 20, 2020 by sputniksteve

[Pixies]

1 minute ago, sputniksteve said:

It's probably my memory tbh. It was well collimated and a great mirror. 

What altitude was Jupiter at the time, can you recall? I imagine that Texas is a little further south than you are.

Big apertures suffer more under poor seeing, don't they?

[sputniksteve]

It would have been pretty low. I recall having to really squeeze the break tight to stop the tube dropping. Although - I had that scope for a few years and pretty sure I can remember views of Saturn and Jupiter higher up. But my memory of stuff is generally shot to pieces.

[John]

2 hours ago, Louis D said:

That 12" must have been miscollimated or had a terrible mirror.  My most memorable views of Jupiter were through a 12.5" Mag1 Instruments PortaBall with a Zambuto mirror on an Osypowski equatorial platform at a star party.  I could make out all sorts of festoons and barges in the belts with ease.

I agree. When they are higher in the sky my 12 inch dob has shown spectacular views of Jupiter and Saturn. Similar Jovian details to the ones you describe. Strings of eddies around the GRS, white ovals, that sort of stuff.

 

[niallk]

I use a 15" scope when observing planets - I check the jetstream forecast before setting up, and I allow about 3 hours with fan cooling to get the best views.  Heat plumes from surroundings can destroy things, and collimation has to be spot on.  And some nights, the views just aren't great.  On a decent night though, when the scope is really well cooled, the views are beautiful & sharp, and really worth the effort of throwing the scope out early to cool down.

[Don Pensack]

On 20/09/2020 at 07:01, sputniksteve said:

It's probably my memory tbh. It was well collimated and a great mirror. 

I'd also suggest that seeing and sky quality etc would have made a difference. I'm in Bortle 5. 

I've not yet a good view of Jupiter with the 127. I do recall that looking great through the 12" though.

A Bortle Class 9 is fine for planets.

What matters is the seeing.  And that is estimable by this:

http://www.damianpeach.com/pickering.htm