Better planetary views

[A_N_other_beginner]

I've got a Celestron C6N that I really need to get to grips with. I appreciate it's not the best time of year necessarily for Saturn/Jupiter, but I had a glimpse of Saturn's rings the other night and would really like to be able to show as much as I can to my eldest, the interest is clearly there.

Firstly - maintenance issue. I had Jupiter centred last night, and when well out of focus (but with the light of Jupiter to make the mirror visible through the EP), the donut shaped light looked like a science textbook of bacteria on a petri dish. Is that normal or a sign of dirt/something that needs rectifying? It's been a few months since I used the scope and when I did I had frosting issues, my concern is if this is a sign of mould.

Secondly: my EP collection is limited and needs to grow. I've had a look at Jupiter with a mix of 10mm BCO and a cheap Vixen 2X barlow that I mainly purchased for attaching my DSLR for lunar photography - so not ideal. But 150x, which I gather is in the right ballpark for Jupiter? All I could make out was the faintest of banding. I appreciate the needs may be different for Jupiter vs. Saturn, but I'm considering either a better barlow (Televue 2x?) or something like a Vixen SLV 5mm or push it up to 187x with a 4mm. I've got a budget of about £100, where would I gain the greatest benefit - either of those options, or something else?

Edited August 7, 2019 by A_N_other_beginner

[George Jones]

12 minutes ago, A_N_other_beginner said:

IFirstly - maintenance issue. I had Jupiter centred last night, and when well out of focus (but with the light of Jupiter to make the mirror visible through the EP), the donut shaped light looked like a science textbook of bacteria on a petri dish. Is that normal or a sign of dirt/something that needs rectifying?

Sorry, I don't know what bacteria on petri dishes look like. 😀  Point your C5 at a brightish star, and take the star out of focus. You should see an image with a dark circular disk in the centre with the disk surround by a concentric bright circular band. If you don't see circles, then your scope needs collimating.

[Ricochet]

1 hour ago, A_N_other_beginner said:

the donut shaped light looked like a science textbook of bacteria on a petri dish

Probably hairs/fibres on your eyepiece lenses. 

1 hour ago, A_N_other_beginner said:

I've had a look at Jupiter with a mix of 10mm BCO and a cheap Vixen 2X barlow

The 10mm BCO is very good and the Vixen barlow will also be good. I don't think there will really be anything to gain optically by changing the barlow or by buying any of the eyepieces in your price range. If you were to switch to the SLV you would gain eye relief which should be more comfortable and might help your observing. 

The atmosphere really is the limiting factor this year so you will probably be best off not duplicating a focal length that is covered by your existing eyepiece and barlow. Given that you effectively have a 10 and a 5mm, a 7mm (or 14mm) would split them nicely. 

[A_N_other_beginner]

33 minutes ago, Ricochet said:

Probably hairs/fibres on your eyepiece lenses. 

The 10mm BCO is very good and the Vixen barlow will also be good. I don't think there will really be anything to gain optically by changing the barlow or by buying any of the eyepieces in your price range. If you were to switch to the SLV you would gain eye relief which should be more comfortable and might help your observing. 

The atmosphere really is the limiting factor this year so you will probably be best off not duplicating a focal length that is covered by your existing eyepiece and barlow. Given that you effectively have a 10 and a 5mm, a 7mm (or 14mm) would split them nicely. 

I'm surprised to hear the Vixen Barlow referred to as good - it's a £20 jobby, I didn't actually buy it for use as a barlow.

https://www.vixenoptics.com/Vixen-2x-Barlow-Lens-T-31-7mm-p/3907.htm

[Rob Sellent]

When it comes to observing Jupiter and Saturn, I don't enjoy an exit pupil any lower than about 0.6mm. At this stage the image of the planets is already quite dim for me and floaters are drifting more often in front of detail. As such, 0.6mm is a working limit on these two gas giants.

However, I've also found that 25x - 40x per inch of aperture is a decent general guide for maximum magnification for me when viewing Jupiter and Saturn. I know folk observe the two gas giants over this limit but not all my scopes can handle this and just as importantly floaters are becoming ever more apparent and the atmospheric conditions where I live generally don't support higher per inch magnifications.

Along this lines, I've found that seeing - atmospheric turbulence - starts to raise its ugly head from about 100x and really starts to interfere with my observations from around 180x to 200x. Unless I have very steady skies I can rarely observe Jupiter and Saturn over these higher magnifications.

Finally, I also need to take into account things like the scopes collimation, cooling, my own fatigue and so on.

So, as you'll appreciate, when it comes to observing Jupiter and Saturn there's a little bit of compromising going on: a) the quality of my eyes b) the quality of my optics c) the quality of the seeing and d) the 3 Cs: quality of collimation, cooling and personal conditions.

If we take these ideas and apply them to you 6" f5 reflector, I think we can come to some conservative estimates.

25x per inch represents an exit pupil of 1mm. In your own case, you'll get about 150x with a 5mm eyepiece. This 150x, 1mm exit pupil I'd set for the moment as a high power for your 6". This doesn't mean you can't go higher. Of course you can, but exit pupil will become tighter perhaps giving rise to floaters, it'll cause further dimming of the object and decent seeing conditions will be more limited as you push the magnification.

I feel this is good news, for you already have a 10mm eyepiece and a x2 Barlow, so you really don't need to spend the money . So much depends on atmospheric conditions when it comes to magnification and planetary observation. Perfect conditions are rare, especially this season with Jupiter and Saturn being so low.

Personally, then, I'd sit it out. I'd advise you to not spend your cash on a lower exit pupil eyepiece and instead limit yourself to this 150x for this season with Jupiter and Saturn and see where you are in terms of scope, experience and disposition next year.

Other than that, it might be an idea to invest in a decent zoom and overtime you'll be able to work out what maginifications work with your scope, skies and eye and of course perhaps the most important factor, to just sit calmly with the planets, spend some time at the eyepiece with them and let the seeing, turbulence and your own dispositions make the features more then less then more observable. I also think its a good idea from time to ime to sketch what we are observing. I feel this also strengthens observing skills.

[Stu]

Wise words from @Rob Sellent which make alot of sense. At present the planets are not taking alot of magnification due to their low altitudes so less is more often turns out to be the right approach.

My only reservation is the Barlow. Vixen products are usually very good, but barlows can reduce the quality of views if not top notch so I may be tempted to get a 5mm at some point to see whether it sharpens things up at all. A used 5 mm ortho could be bought and sold for little or no loss at £40 to £50 max (just postage really) so could allow you to have a try, providing you can manage with the short eye relief, otherwise the SLV mentioned would be a good option.

[Saganite]

26 minutes ago, Stu said:

Wise words from @Rob Sellent which make alot of sense. At present the planets are not taking alot of magnification due to their low altitudes so less is more often turns out to be the right approach.

My only reservation is the Barlow. Vixen products are usually very good, but barlows can reduce the quality of views if not top notch so I may be tempted to get a 5mm at some point to see whether it sharpens things up at all. A used 5 mm ortho could be bought and sold for little or no loss at £40 to £50 max (just postage really) so could allow you to have a try, providing you can manage with the short eye relief, otherwise the SLV mentioned would be a good option.

Just to add to what has been said so far, I was able to see the main bands with  small amounts of detail and the Great Red Spot at just 74x in my 4" refractor, two nights ago.

Edited August 8, 2019 by Saganite

[Owmuchonomy]

Very thorough advice above. The juicy planets are poorly placed for a few years. As part of your need is to keep the interest of others then I found that showing the moons of both Jupiter and Saturn and explaining their movement and positions to be an option. Your C6 should show the major moons. The views of Saturn’s moons through my 9.25 were very good the other day. As above, check your collimating is spot on.

[Alfian]

Regarding a 5mm EP if funds will not stretch to an SLV, a very nice EP, then the BST Starguider is a good cheaper alternative.

[Rob]

32 minutes ago, Alfian said:

Regarding a 5mm EP if funds will not stretch to an SLV, a very nice EP, then the BST Starguider is a good cheaper alternative.

Additionally these are good option. Nice performers and price tbh. Love my 6mm

https://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-uwa-planetary-eyepieces.html

Rob

[Geoff Barnes]

+1 for the Skywatcher Planetary EP's, amazing quality for the price. I would have a 4mm or 5mm for Saturn and a 5mm or 6mm for Jupiter for the best high power views. Easily within your budget.

[John]

I think eyepieces are well down the list of things that could be restricting the quality of your planetary views to be honest with you. Your Baader Classic Ortho 10mm will probanbly be delivering as good a view of Jupiter and Saturn as the scope and conditions will allow.

Have a look at this article from an experienced observer and especially the section called "The Wobbly Stack":

http://www.scopeviews.co.uk/Eyepieces for Planets.htm

Note how far down the list of factors the eyepiece is.

[Rob]

28 minutes ago, John said:

I think eyepieces are well down the list of things that could be restricting the quality of your planetary views to be honest with you. Your Baader Classic Ortho 10mm will probanbly be delivering as good a view of Jupiter and Saturn as the scope and conditions will allow.

Have a look at this article from an experienced observer and especially the section called "The Wobbly Stack":

http://www.scopeviews.co.uk/Eyepieces for Planets.htm

Note how far down the list of factors the eyepiece is.

Getting myself back on topic. Fully agree John. There are so many factors involved before tackling equipment. The The Planets position right now is tricky, and UK skies are not helpful. Once we get height mag's can be pushed to an amazing level, holding contrast and steadiness too.

Rob

Edited August 8, 2019 by Rob

[Geoff Barnes]

Fully realise planets are in terrible positions for you folks in the UK, but no harm in planning for the future when, in 3 or 4 years time, they will be at good altitudes to allow much better seeing and you will get the full benefit of having good quality eyepieces.

With Jupiter and Saturn at 75 degrees altitude here I have had amazing views this year (before winter gloom descended).

[Cosmic Geoff]

I struggled to see much detail on the planets with visual observation.  For me the answer was to try planetary imaging.  Almost the first time I tried imaging Jupiter with my 127mm Mak, I secured an image that clearly showed the Great Red Spot, and much more detail than I had ever seen visually. 

[russ]

I was out yesterday evening with the 200P and found the best view came from using the 12mm TV plossl working at 83x. The atmosphere was degrading the image badly above 100x.

It could be your C6N needs collimating but much more likely its simply the atmospheric conditions that are holding you back. And the Baader BCO 10mm is simply top notch optically, so you're really not going to get something that much better even if you spent hundreds. You are well into the realms of diminishing returns going beyond the 10mm BCO. It will be more about buying an eyepiece that is easier and nicer to use, rather than optically better.  

[Erling G-P]

For your budget, I would look at an ADC (Atmospheric Dispersion Corrector):

https://www.firstlightoptics.com/zwo-accessories/zwo-125-atmospheric-dispersion-corrector-adc.html

I got one recently, and while it doesn't perform miracles, it has improved my views.  Do note that it's designed to be used with a barlow - I couldn't reach focus without one.

 

Regards,

Erling G-P

[A_N_other_beginner]

A bit of a mix of replies, although I fully accept the one constant that planetary viewing conditions aren't currently ideal.
In relation to EP's etc, I'm completely happy with the quality of the BCO but my reservation comes from the barlow - it's a cheap thing. My background is photography and I've no idea how much this transfers over, but the rule was often that putting bad glass in front of good glass is not a recipe for the best capture - is that true here?

I will definitely look into collimation, and it's pleasant to see some suggestions that don't involve spending money. However I do have a bit of cash earmarked for something, so even if it's not something that's specifically going to help with Jupiter and Saturn currently I'm happy to spend it to just have more tools at my disposal. If the existing  cheap 2x barlow is better than I'm giving it credit for, then an EP that'll help with DSO viewing or something else is fine. Flexibility is never a bad thing.

[PH-R]

23 hours ago, Erling G-P said:

For your budget, I would look at an ADC (Atmospheric Dispersion Corrector):

https://www.firstlightoptics.com/zwo-accessories/zwo-125-atmospheric-dispersion-corrector-adc.html

I got one recently, and while it doesn't perform miracles, it has improved my views.  Do note that it's designed to be used with a barlow - I couldn't reach focus without one.

 

Regards,

Erling G-P

I would go with this option.

[A_N_other_beginner]

2 hours ago, PH-R said:

I would go with this option.

Even though it'd mean a stack including a cheap and basic barlow?
I can see the value of an ADC, but in a combination including a good and a basic (and presumably optically inferior?) barlow I'm wondering how much the benefit of the ADC would be offset by that cheaper piece of glass in the middle. Am I barking up the wrong tree regarding the barlow?
If I already had the barlow I'm considering (Televue 2x) I'd not be thinking about the weak link quite so much, but I genuinely don't know what sort of difference there is between a £20 barlow and a £100 one.

[Stub Mandrel]

On 08/08/2019 at 07:21, Saganite said:

Just to add to what has been said so far, I was able to see the main bands with  small amounts of detail and the Great Red Spot at just 74x in my 4" refractor, two nights ago.

On the night of the recent eclipse I could see two bands on Jupiter in my 2" Tasco scope 🙂

My C90 Mak easily revealed the Red Spot and Io's shadow recently as well at 40x.

[Stub Mandrel]

25 minutes ago, A_N_other_beginner said:

Even though it'd mean a stack including a cheap and basic barlow?
I can see the value of an ADC, but in a combination including a good and a basic (and presumably optically inferior?) barlow I'm wondering how much the benefit of the ADC would be offset by that cheaper piece of glass in the middle. Am I barking up the wrong tree regarding the barlow?
If I already had the barlow I'm considering (Televue 2x) I'd not be thinking about the weak link quite so much, but I genuinely don't know what sort of difference there is between a £20 barlow and a £100 one.

Consider the Rvelation Astro ED Barlows for plenty of quality for rather less than £100.

[John]

The best low cost (well, lowish) barlow that I've come across is the Baader Q-Turret 2.25x. Simple build but good glass

 

 

 

[PH-R]

1 hour ago, A_N_other_beginner said:

Even though it'd mean a stack including a cheap and basic barlow?
I can see the value of an ADC, but in a combination including a good and a basic (and presumably optically inferior?) barlow I'm wondering how much the benefit of the ADC would be offset by that cheaper piece of glass in the middle. Am I barking up the wrong tree regarding the barlow?
If I already had the barlow I'm considering (Televue 2x) I'd not be thinking about the weak link quite so much, but I genuinely don't know what sort of difference there is between a £20 barlow and a £100 one.

Yes I would go for that now and save up for the powermate or barlow. 

[John]

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