Optimising contrast when observing the planets

[mikeDnight]

You could try using an off axis aperture stop. You may be able to cut a cardboard stop with a 4" or 4.5" off axis aperture to fit between the spider veins. It may sound counter intuitive, but can give great results. And choose an eyepiece that will give a mag of around 180X. If the power is too high it could kill the detail.

Edited August 16, 2023 by mikeDnight

[paulastro]

20 hours ago, mikeDnight said:

You could try using an off axis aperture stop. You may be able to cut a cardboard stop with a 4" or 4.5" off axis aperture to fit between the spider veins. It may sound counter intuitive, but can give great results. And choose an eyepiece that will give a mag of around 180X. If the power is too high it could kill the detail.

This might make the image look sharper Mike, especially if the seeing is not great, however the available resolution will be reduced to the diameter of the stop.  If the objective is to reduce any glare,  ND, polarising, or other filters would be my choice.

With my 10inch Dob (Starsense Explorer) I have seen very good detail on Jupiter and Saturn on some sessions in the last couple of weeks using the binoviewer, 24mm Orthos and a x2 barlow element - giving me  x200.  As you know yourself Mike, for many of us binoviewing itself makes a significant improvement for many observers when observing the Moon and planets.  The sharpness has been very good too - helped to some degree by hazy skies at times.

Just to state the obvious, in using filters, the effect will be different for every observer depending on their eyesight and experience, so it pays to experiment in different conditions.  Also the visibility of the GRS and other features on Jupiter (for instance) will depend on the observers green or red sensitivity - the appropriate choice of filters will help to balance this out to some degree.

Edited August 17, 2023 by paulastro
Typos

[bosun21]

2 hours ago, paulastro said:

With my 10inch Dob (Starsense Explorer) I have seen very good detail on Jupiter and Saturn on some sessions in the last couple of weeks using the binoviewer,

How do you find using your binoviewer with your dobsonian? I have been looking at using my MBII’s with my 12” dobsonian. I was wanting to buy the GPC from Baader designed for Newtonians but unfortunately they are in the process of designing a new model and no longer sell the old one. How are the aberrations off axis? Thanks.

[paulastro]

29 minutes ago, bosun21 said:

How do you find using your binoviewer with your dobsonian? I have been looking at using my MBII’s with my 12” dobsonian. I was wanting to buy the GPC from Baader designed for Newtonians but unfortunately they are in the process of designing a new model and no longer sell the old one. How are the aberrations off axis? Thanks.

bosun21  I have no problem using the binoviewer with any telescope.  I have the original Baader Maxbright and it's always worked with any barlow lens, or just a barlow element screwed straight into the binoviewer eyepiece.  With any scope I've used it always comes to focus, and this includes my 10 inch Starsense Dob. 

The barlow I use mostly is just the element component of a x2 SW Deluxe barlow screwed into the Maxbright nosepiece.  I also use 24 mm Orthoscopics usually, x200 on the 10 inch Dob.

On the Moon and planets the image stays in focus right across the width of the field to the edges.  The images are better than with any single eyepiece I have ever tried including Monos and Delos.

Just try any barlow, or just the element, you may find it's all you need.

The only downside is if you wanted to use a pair of eyepieces and use them at their native focal lengths at lower powers.  On most Newtonians, without using a barlow ( which has the affect of increasing the eyepieces magnification by x4) you will not be able to get the binoviewer to focus.  There won't be enough in-focus.

You will need the GPC for low powers with appropriate eyepieces.  No problem for me as I mostly use my binoviewer for the Moon and planets.

[bosun21]

4 minutes ago, paulastro said:

bosun21  I have no problem using the binoviewer with any telescope.  I have the original Baader Maxbright and it's always worked with any barlow lens, or just a barlow element screwed straight into the binoviewer eyepiece.  With any scope I've used it always comes to focus, and this includes my 10 inch Starsense Dob. 

The barlow I use mostly is just the element component of a x2 SW Deluxe barlow screwed into the Maxbright nosepiece.  I also use 24 mm Orthoscopics usually, x200 on the 10 inch Dob.

On the Moon and planets the image stays in focus right across the width of the field to the edges.  The images are better than with any single eyepiece I have ever tried including Monos and Delos.

Just try any barlow, or just the element, you may find it's all you need.

The only downside is if you wanted to use a pair of eyepieces and use them at their native focal lengths at lower powers.  On most Newtonians, without using a barlow ( which has the affect of increasing the eyepieces magnification by x4) you will not be able to get the binoviewer to focus.  There won't be enough in-focus.

You will need the GPC for low powers with appropriate eyepieces.  No problem for me as I mostly use my binoviewer for the Moon and planets.

Thanks Paul. I currently have all three of the GPC’s two of which screw into the binoviewer itself. I will try it with the 1.7x (which is closer to 1.5x in practice) GPC the next clear night. I am trying to think of a way to use the 2.6x GPC in the stack as this can’t be screwed into the binoviewer🤔. I at present have pairs of 32mm, 25mm, 16mm plossls, 18mm BCO’s and 10mm UFF’s. I will need to buy a 1.25” nosepiece if I need to go the barlow route. What sort of magnification factor does a 2x barlow end piece provide when screwed into the nosepiece? Sorry for rambling on.

[Paz]

Finding a location with good local seeing conditions may be of benefit, i.e. away from houses, pavements, car parks, roads, buildings etc, and preferably somewhere where the ground falls away from you so your line of sight is rising as quickly as possible away from the ground turbulence and local heat sources. I do this often for solar observing and planetary and lunar and this can make a lot of difference.

Using various contraptions to dim the image to the optimum brightness works well, I have had great results in the last couple of years doing this. 

I find an ADC can be of help on Jupiter, Mars, and Saturn, but I find it not so much help on Venus where the benefit of colour correction is offset by the additional scatter.

Stopping down the aperture to tune it in to the conditions both in terms of dimming the image, getting underneath the seeing, and slowing the focal ratio of a scope can sometimes help.

 

[globular]

1 hour ago, bosun21 said:

How do you find using your binoviewer with your dobsonian? I have been looking at using my MBII’s with my 12” dobsonian. I was wanting to buy the GPC from Baader designed for Newtonians but unfortunately they are in the process of designing a new model and no longer sell the old one. How are the aberrations off axis? Thanks.

You may have seen this from the baader binoviewer documantation:
Baader's figures are not super accurate - but they give a good idea about how much extra focus movement you'll need.
e.g. if you have 44mm of focus travel left when using an eyepiece on it's own, then it should work in the bino with the 2.6x gpc.  See how much travel you have and them pick the lowest power GPC that is below that figure.
The newt version gives a bit more travel than even the 2.6x GPC, and at less magnification - which can be useful.  But if you can get it to work with one of your existing GPCs then I'd stick with that.

I personally always use a GPC rather than a barlow with my MBII - they seems a little more 'invisible' to my eyes.

p.s. the 2.6x GPC screws into baader nosepieces.   They do 1.25" and 2" versions.  So you go baader nosepiece, 2.6x GPC, binoviewer, eyepiece(s).

[bosun21]

4 minutes ago, globular said:

p.s. the 2.6x GPC screws into baader nosepieces.   They do 1.25" and 2" versions.  So you go baader nosepiece, 2.6x GPC, binoviewer, eyepiece(s).

As the convex side of the 2.6x GPC must point to the sky and can’t simply be opened up and the cemented lens doublet reversed like the other two, if screwed into the nosepiece it would be in the incorrect orientation for the 2.6x GPC. This is what I’m trying to work out.

[globular]

10 minutes ago, bosun21 said:

As the convex side of the 2.6x GPC must point to the sky and can’t simply be opened up and the cemented lens doublet reversed like the other two, if screwed into the nosepiece it would be in the incorrect orientation for the 2.6x GPC. This is what I’m trying to work out.

Screwing the 2.6x into the nosepiece does result in the correct orientation. 

If you screw it into the binoviewer then it's pointing at your eye, not the sky.

The 1.25x and 1.7x can, as you say, be reconfigured to work in either position - but the 2.6x has to go into the nosepiece (or diagonal if you're using one) and not the binoviewer.

[bosun21]

I thought you meant screwing it into the 1.25” nosepiece telescope end in which case it’s in the wrong orientation. Does the nosepiece you are using have threads all the way up to allow the GPC to be screwed in from the binoviewer side? The one I previously owned only had threads half way up the nosepiece barrel. In that case it’s problem solved. I think we were talking about the same outcome all along. Thanks again.

[Franklin]

All the non-Z GPC's can be placed after or before the diagonal, in the latter case there is an increase in magnification. They're not screwed into the nosepiece end, like a filter but placed inside the nosepiece from the diagonal end. This is what the supplied plastic ring is for, to centralize the GPC in the nosepiece.

[globular]

[we're off topic - sorry OP 😇]

Edited August 17, 2023 by globular

[paulastro]

1 hour ago, bosun21 said:

Thanks Paul. I currently have all three of the GPC’s two of which screw into the binoviewer itself. I will try it with the 1.7x (which is closer to 1.5x in practice) GPC the next clear night. I am trying to think of a way to use the 2.6x GPC in the stack as this can’t be screwed into the binoviewer🤔. I at present have pairs of 32mm, 25mm, 16mm plossls, 18mm BCO’s and 10mm UFF’s. I will need to buy a 1.25” nosepiece if I need to go the barlow route. What sort of magnification factor does a 2x barlow end piece provide when screwed into the nosepiece? Sorry for rambling on.

 No problem.  It depends on the binoviewrs light path, but with a x2 barlow,  just divide the eyepiece fl by 4.  So a pair of 24mm ep will effectively be 6mm.

[bosun21]

Sorry for going off topic Paul. @globular and @Franklin has explained it clearly showing the 2.6x insertion with the plastic ring (good job I held onto them). I will now give my MBII’s a go in my 12” dobsonian. Back to topic everyone.

Edited August 17, 2023 by bosun21
Typo

[paulastro]

Just now, bosun21 said:

Sorry for going off topic Paul. Tim has explained it clearly showing the 2.6x insertion with the plastic ring (good job I held onto them). I will now give my MBII’s a go in my 12” dobsonian. Back to topic everyone.

No apology necessary, I'm pleased someone else is able to help you out.  I've never used GPCs, only barlows 😊.

[Chaz2b]

I've recently purchased a 8"skywatcher to which I have dismantled, blackened the edges to the primary and secondary. Next job is to flock it, I'm an old flocker so not too hard 😲

I've 3d printed a bottom plate to take a 5" cooling fan.

I'm all out to increase contrast wherever I can, which includes blackening the part of the focuser that enters the tube. Not only the tube gets the treatment but my eyepieces too!

Chaz