Better planetary views

[Stub Mandrel]

12 minutes ago, John said:

Hmmm, I'm not convinced that the £120 investment in an ADC would deliver significatly improved views of Jupiter and Saturn in this case. I've had some very nice views of both planets lately from the UK and while their low altitude has created some challenges with seeing stability from time to time, I've not noticed the tell tale signs of atmospheric dispersion specifically affecting the views.

I suspect that the original poster might get better results by checking the collimation of the scope, ensuring that it's cooled and by observing these targets for a good period of time to allow the observing eye a chance to adjust to the contrasts and to gradually pick out more details.

At least those steps are cost free and can be put into practice on the next clear evening

 

I don't think an ADC is essential for observing as I think the eye accomodates to the dispersion after a bit.

That said, I set up my ADC for photography by using an eyepiece in place of the camera. The setting isn't super critical compared to focusing but I find the improvement easy to observe, and it's also possible to see when you have 'gone too far'.

(At the moment dispersion is very marked through a camera, but adjusting is difficult as the planet moves across the sensor when you change the setting so you end up having to make a small changes, re-centre the planet and repeat - an optical setting is just much quicker).

[StarryEyed]

It's easy to think that there are problems when in fact there are not.

You say you need to get to grips with your current scope. Then this is exactly what you need to do. This sounds like you have everything you need but one thing and that's experience in using your telescope and really good conditions.

I once owned a Sky watcher 127 Mak Cass a not so dissimilar scope. In the five years I owned it gave me bad views and good views depending on the conditions. Only on one night mid January when it was minus five and one o'clock in the morning did I get a view of the moon that was clearly outstanding. it's burnt into memory. Maybe there were a few other nights but it became clear to me that sometimes you can wait months even years for the everything to be right. There are lots of nights when this is true but you have to be out there using the scope.

A good target is the moon you will quickly see how the sky conditions effect things. You will quickly see if it worthwhile moving onto more difficult targets. Even if it's not such a good night the moon rarely disappoints. 

So get to grips with your scope, save your money and get your eldest involved.

Kevin.

Edited August 9, 2019 by StarryEyed

[A_N_other_beginner]

52 minutes ago, StarryEyed said:

It's easy to think that there are problems when in fact there are not.

You say you need to get to grips with your current scope. Then this is exactly what you need to do. This sounds like you have everything you need but one thing and that's experience in using your telescope and really good conditions.

I once owned a Sky watcher 127 Mak Cass a not so dissimilar scope. In the five years I owned it gave me bad views and good views depending on the conditions. Only on one night mid January when it was minus five and one o'clock in the morning did I get a view of the moon that was clearly outstanding. it's burnt into memory. Maybe there were a few other nights but it became clear to me that sometimes you can wait months even years for the everything to be right. There are lots of nights when this is true but you have to be out there using the scope.

A good target is the moon you will quickly see how the sky conditions effect things. You will quickly see if it worthwhile moving onto more difficult targets. Even if it's not such a good night the moon rarely disappoints. 

So get to grips with your scope, save your money and get your eldest involved.

Kevin.

That's easier said than done. There's only a small percentage of nights where the cloud cover makes it worthwhile taking the scope outside and when I am actually able to do that. Of those, the percentage of the time when I can reasonably bring a child out too is much smaller. This hobby fascinates me (and youngster) but I don't see any choice other than to look to maximise the time I have available. I accept there are no absolute shortcuts, but spending night after night looking at the moon (for the record, something I've managed a fair few times) just to get my eye in for when the conditions just isn't going to happen. And expecting a young childs interest to be held repeating the same isn't likely.

I'm not trying to blame my tools here. I'm just trying to make the most of the very limited time my eldest and I can spend together with the scope. And if I can stretch to an EP, barlow or ADC (and - whatever I consider, a collimation cap and some cleaning products for the EP's will be on the order) I do this knowing that at some point in the future that item will be used. It might not be for planets, it might be used for picking out lunar features or trying to split doubles, or something else. So I accept that the long way round is to take my time, learn the craft, learn to use what I've got - in a sense a refreshing change from the consumerism embedded into many hobbies. And I still hope to do that along the way. But I certainly don't have a problem with buying something - not in a vain hope of solving a problem, but because if I've got it I'm likely to use it. It's long been my intention to add a couple of EP's and a quality barlow, if one of those things could help with planetary viewing that is really a bonus.

 

One issue I have noticed is that the youngster seems to struggle with the BCO (as has my wife) to actually see anything very much. I've managed okay but struggle to articulate to a child how to move your eye around to actually get the subject visible - and that's before worrying about getting it into focus. I've noticed that my 32mm Vixen NPL is the most comfortable EP I have. Would something like the SLV be easier to use compared to the BCO with regards to the issue I've described?

[Stu]

5 minutes ago, A_N_other_beginner said:

Would something like the SLV be easier to use compared to the BCO with regards to the issue I've described?

Definitely yea. The BCO has a relatively small exit lens and limited eye relief (7mm or so). The SLVs have larger exit lenses, 20mm eye relief and twist up eye cups to make it easier to position your eye and see the object properly. Makes it a sensible move I think if you want to keep your son engaged.

[John]

50 minutes ago, A_N_other_beginner said:

That's easier said than done. There's only a small percentage of nights where the cloud cover makes it worthwhile taking the scope outside and when I am actually able to do that. Of those, the percentage of the time when I can reasonably bring a child out too is much smaller. This hobby fascinates me (and youngster) but I don't see any choice other than to look to maximise the time I have available. I accept there are no absolute shortcuts, but spending night after night looking at the moon (for the record, something I've managed a fair few times) just to get my eye in for when the conditions just isn't going to happen. And expecting a young childs interest to be held repeating the same isn't likely.

I'm not trying to blame my tools here. I'm just trying to make the most of the very limited time my eldest and I can spend together with the scope. And if I can stretch to an EP, barlow or ADC (and - whatever I consider, a collimation cap and some cleaning products for the EP's will be on the order) I do this knowing that at some point in the future that item will be used. It might not be for planets, it might be used for picking out lunar features or trying to split doubles, or something else. So I accept that the long way round is to take my time, learn the craft, learn to use what I've got - in a sense a refreshing change from the consumerism embedded into many hobbies. And I still hope to do that along the way. But I certainly don't have a problem with buying something - not in a vain hope of solving a problem, but because if I've got it I'm likely to use it. It's long been my intention to add a couple of EP's and a quality barlow, if one of those things could help with planetary viewing that is really a bonus.

 

One issue I have noticed is that the youngster seems to struggle with the BCO (as has my wife) to actually see anything very much. I've managed okay but struggle to articulate to a child how to move your eye around to actually get the subject visible - and that's before worrying about getting it into focus. I've noticed that my 32mm Vixen NPL is the most comfortable EP I have. Would something like the SLV be easier to use compared to the BCO with regards to the issue I've described?

In order to see more detail on planets such as Jupiter and Saturn, you need to spend some time observing them regardless of the quality of optics employed. What I mean by this is that 30-60 minutes of observing a target will gradually allow more detail to be seen. A quick look (eg: just a few minutes) will restrict the amout of detail that will be visible generally, in Jupiters case, to the two main cloud belts. Maybe a little more under good conditions. I realise that younger observers might have a more limited attention span but the general advice of "the more you look, the more you see" applies with them as well.

There are eyepieces that are easier and more comfortable to view with than orthoscopics and a relaxed eye does help in teasing out more detail plus making observing generally a more enjoyable process.

The Vixen SLV eyepiece range is more comfortable to view through for the reasons that Stu explains and maintains a similar level of optical quality to the orthoscopic.

When you are using higher powers with a scope (ie: 100x, 150x etc, etc) you need to use a short focal length eyepiece and that has the effect of producing a small exit pupil (the illuminated disk of light that comprises the field of view) and that smaller patch of light is what newcomers to observing can find hard to pick up as they move their eye to the eyepiece. The Vixen 30mm, being a relatively low power eyepiece produces a larger exit pupil which is easier to find with the eye. I've found repeatedly this is the case from the outreach events that I've done with my astro society.

With patience and practice folks learn how to keep their head still and how to position their eye at the eyepiece and get more success at picking up, and holding, the smaller exit pupils that higher powers inevitably produce. When using a 10mm eyepiece with your scope (which I think is an F/5 newtonian ?) the exit pupil is 2mm in diameter. If you reduce that to a 5mm eyepiece for higher power, the exit pupil reduces to 1mm.

 

[A_N_other_beginner]

44 minutes ago, John said:

In order to see more detail on planets such as Jupiter and Saturn, you need to spend some time observing them regardless of the quality of optics employed. What I mean by this is that 30-60 minutes of observing a target will gradually allow more detail to be seen. A quick look (eg: just a few minutes) will restrict the amout of detail that will be visible generally, in Jupiters case, to the two main cloud belts. Maybe a little more under good conditions. I realise that younger observers might have a more limited attention span but the general advice of "the more you look, the more you see" applies with them as well.

There are eyepieces that are easier and more comfortable to view with than orthoscopics and a relaxed eye does help in teasing out more detail plus making observing generally a more enjoyable process.

The Vixen SLV eyepiece range is more comfortable to view through for the reasons that Stu explains and maintains a similar level of optical quality to the orthoscopic.

When you are using higher powers with a scope (ie: 100x, 150x etc, etc) you need to use a short focal length eyepiece and that has the effect of producing a small exit pupil (the illuminated disk of light that comprises the field of view) and that smaller patch of light is what newcomers to observing can find hard to pick up as they move their eye to the eyepiece. The Vixen 30mm, being a relatively low power eyepiece produces a larger exit pupil which is easier to find with the eye. I've found repeatedly this is the case from the outreach events that I've done with my astro society.

With patience and practice folks learn how to keep their head still and how to position their eye at the eyepiece and get more success at picking up, and holding, the smaller exit pupils that higher powers inevitably produce. When using a 10mm eyepiece with your scope (which I think is an F/5 newtonian ?) the exit pupil is 2mm in diameter. If you reduce that to a 5mm eyepiece for higher power, the exit pupil reduces to 1mm.

 

I take it though that adding a barlow also affects the exit pupil size proportionately, so whether you 2x barlow a 10mm or just have a 5mm you're still talking the same levels of magnification and exit pupil size?

[John]

Just now, A_N_other_beginner said:

I take it though that adding a barlow also affects the exit pupil size proportionately, so whether you 2x barlow a 10mm or just have a 5mm you're still talking the same levels of magnification and exit pupil size?

Yes thats right.

 

[A_N_other_beginner]

42 minutes ago, John said:

Yes thats right.

 

Thanks.
In light of that I'm drawn to a more comfortable EP, particularly for spending more time at the scope to adjust. I've almost made my mind up. With 150x the suggested upper limit that points towards the 5mm SLV (unless the ES82 is as comfortable in use? I believe I saw some comparisons somewhere.) Whilst there is a risk that the difference will be marginal between a 5mm SLV and a barlowed BCO, having been really impressed by the eye relief on the NPL range I'm inclined to take a chance on the SLV - particularly with my target audience.

Cheers to all that have given me a steer. I am going to address the basics first such as collimation, dirt on the EP's as frankly even if they aren't an issue it's worthwhile learning a bit of basic maintenance, and who knows - it could make a significant difference. It's all a steep learning curve but I appreciate everyone taking the time to share the benefit of their experiences with me.

Edited August 9, 2019 by A_N_other_beginner

[John]

The Vixen NPL eyepieces are plossls so they have eye relief of around 50%-80% of the focal length of the eyepiece. Orthoscopics are similar in this respect. This is a feature of these designs.

So the 30mm NPL has 20mm plus of eye relief, which is nice and comfortable, but the 6mm NPL has just 3mm, which is very tight.

Today there are many eyepiece designs which offer eye relief in the 15mm - 20mm range even in the shorter focal lengths. The Vixen SLV is one of these designs.

 

 

 

[Rob Sellent]

I was viewing Jupiter this evening and wondered what might make a worth while check list. I've probably missed somethings important, but hopefully this will get you in the ball park:

Cooling: aim you scope at one of the bright stars you see (Deneb, Altair or Vega, for example). Defocus the image a little until you see concentric rings in your eyepiece. If insect/bug like things are crawling around in the image, you've probably got thermal issues. It helps when working at high power to get rid of these bugs, so allow time for cooling. My general rule of thumb is about 5 to 10 minutes per inch.

Collimation: if this defocused image in your f5 doesn't look a bit like an offset bullseye, your scope may need a little tweaking. I've read two excellent guides to doing this: Moonshane  and  Astrobaby.

Set Up: try not to observe over roofs, concrete blocks, or roads, etc. Better to view over lawns, grass or water.

Seeing: if the stars are twinkling, seeing is probably not good. If they are steady, seeing might be okay. The thing is there's no real guarantee of seeing just by looking at the sky. Seeing is an elusive sprite. There are moments when everything is good, other times when it's hard to see much at all and all this could be in the same five minutes.

Magnification: simply put, seeing affects magnification. Unless your lower power view of Jupiter is steady and sharp, increasing magnification isn't going to help. Indeed, its not always necessary to throw magnification at Jupiter to get some pretty decent views. In my little 3" frac, I often observe Jupiter between 60x to 100x and don't feel I'm missing too much.

Experience: even if cooling, collimation, set up and seeing are spot on, planetary details may still be missing that are more than obvious to other observers. The only solution to this problem is experience.

Let us know how you get along. It'll be a pleasure to read about your own and your son's adventures 🙂

 

[A_N_other_beginner]

I'm going to check the collimation tonight all being well, and have ordered a collimation cap to have standing by.
I did go out with it for awhile last night and left it to cool, I didn't notice quite the same issues with the 'bug on lens' effect but it was still there to an extent. I tried cleaning the eye piece (with a tool I use for DSLR lenses) which may have helped, or it may have been the cooling but I've got some optical cleaning fluid en route too.

I did try a comparison in clarity between the 10mm BCO with and w/o barlow; Jupiter was still similar to the other night in both cases. Conditions weren't bad, the wind meant any cloud cover was moved quickly.

One thing I have noticed is that there's some slight vibration/wobbling currently. I'm not sure if that's just the magnification showing up everything, effect of a breeze on the scope or something else. Is there any benefit to adding counterweights? The mount is a SW AZ4.

[Alan64]

I have an Orion 150mm f/5 Newtonian, and here upon an alt-azimuth that's quite comparable to your own...

Both of our telescopes are produced by Synta, as are those branded "Sky-Watcher".  This is the collimation scene of my own upon its arrival in 2012, and well-collimated at that; almost perfect, but I can't take the credit...

Note the lighter circle with the "bull's eye".  That's the reflective underside of the collimation-cap, and that came with the telescope.  Outside of that, the black circle which is the shadow of the secondary-mirror.  You see it as a shadow because it is hosting the scene.  The much larger white area beyond that is the main, primary mirror, and with its rubber retaining-clips.  Then, note how the lighter circle there in the center, with the "bull's eye", is not quite centered within the secondary-mirror's shadow.  That is known as the "secondary off-setting".  It is necessary for shorter, faster Newtonians.  Fortunately, the off-setting occurs automatically when collimating...

https://www.skyandtelescope.com/astronomy-equipment/offsetting-your-secondary-mirror/

The purpose of the off-setting is quite simple, and to ensure that all of the light gathered by the primary-mirror reaches the eye.  Again, the off-setting occurs automatically, although there are advanced users who like to tweak it further.  

If the telescope is collimated to near perfection, you can conceivably realise up to at least 50x per inch, which translates to a power of 300x, particularly whilst observing the Moon, as the body is quite close to Earth...

750mm ÷ 300x =  a 2.5mm eyepiece

Such dedicated eyepieces do exist, although, granted, even though the opportunity to employ such a high power is rare, it may occur nonetheless, and then to see with your own eyes what very few people have seen before.

I use a 12mm wide-angle eyepiece combined with a 3x barlow, and for a simulated 4mm.  For a simulated 3mm, a 9mm combined with a 3x barlow; an 8mm, then a 2.6mm is realised.

Generally all of the wide-angle, short focal-length eyepieces that are vended online have barlowing lens-elements integrated, therefore no need for a barlow; for example...

https://www.firstlightoptics.com/bst-starguider-eyepieces/bst-starguider-60-32mm-ed-eyepiece.html (234x)

Would a mere 234x seem insurmountable?  Not too long ago, and after I had collimated it, I took this afocal shot of the Moon, through the bundled 4mm Ramsden(?) eyepiece with a small point-and-shoot camera, at 250x, and with a Celestron 5" reflector...

The live view was tack-sharp.  I had to deal with a shaky mount whilst taking that shot with the camera.

The ultimate goal in collimating a Newtonian, and as spot-on as possible, is to make practical use of a great capability hidden within.  It's there, waiting. 

Edited August 11, 2019 by Alan64

[Stub Mandrel]

2 hours ago, A_N_other_beginner said:

Is there any benefit to adding counterweights?

A bag of rocks hanging from the tripod may help.