Planetary filters

[RT65CB-SWL]

I have the Baader Planetarium contrast booster and neodymium filters and also the Explore Scientific CLS.

Another popular filter I use when observing Venus or Jupiter is a variable polarising filter. Often overlooked, but it works for me.

Edited December 30, 2022 by Philip R

[Giles_B]

On 19/12/2022 at 11:01, Mike Q said:

I have found that my variable polarized filter does a pretty decent job of cutting down the glare and gives me a decent image on Jupiter.  

I'd second the use of a variable polarizing filter - I've found it much more satisfactory than a Neutral density filter in cutting down brightness (an ND 0.9 makes things too dark for my eyes)

I've found a combination of variable polarizing filter plus neodymium filter brings out a lot of detail on Mars. Also consider using an IR/UV cut filter, which sometimes helps when the seeing is poor (which is the case on most warmer nights).

[BlueAstra]

What would be the best filter choice for Jupiter/Mars viewing with a Celestron 9.25” + Baader Hyperion 8/24 mm eyepiece?

[Ratlet]

If you do go for a variable polarising filter I find that holding the eyepiece to the focuser upside down let's you adjust the view to ge the brightness right, or at least close enough.

Helps dim the view for Jupiter and mars, and especially the moon which is almost painfully bright with the 130pds at most magnifications lol.

[Paul Manuell]

On 05/12/2022 at 19:25, vlaiv said:

I've found that Baader Contrast Booster works best for achromats.

It is "cross" between Neodymium and Semi APO, and reduces CA nicely while boosting contrast.

https://www.firstlightoptics.com/baader-filters/baader-contrast-booster-filter.html

Here is interesting read for those Baader filters:

https://www.firstlightoptics.com/reviews/baader-contrast-filters_US-ATT_review_0414.pdf

I second use of Wratten #8 to reduce chromatic aberration - however, it does impart distinct yellow cast on the image.

Thank you, and the review you tagged was an excellent read. It made my mind up to buy the contrast booster... but it's out of stock! It says on their site that stock is due in 1-2 days so I'll try again then

[Franklin]

20 hours ago, Paul Manuell said:

It made my mind up to buy the contrast booster..

Great choice.

[Paul Manuell]

Ok, FLO are still saying 1-2 days for the contrast booster to be available - 2 days after I first read it on their site, and 1-2 weeks for the neodymium filter - nearly 4 weeks after I first read it on their site. So rather than wait for the 1-2 days or 1-2 weeks to materialise, I found a neodymium filter in stock on Harrison's Telescopes and have just ordered one

[Paul Manuell]

Well that was a waste of 80 odd quid. Finally had the chance to try out the new neodymium filter on Jupiter tonight, but too windy for high magnification so only went to 50x

Without filter: 2 bands clearly visible

With filter: No bands visible, just a bright, featureless disc

Gutted!

[JeremyS]

7 minutes ago, Paul Manuell said:

Well that was a waste of 80 odd quid. Finally had the chance to try out the new neodymium filter on Jupiter tonight, but too windy for high magnification so only went to 50x

Without filter: 2 bands clearly visible

With filter: No bands visible, just a bright, featureless disc

Gutted!

Suggest you wait until better conditions, and certainly when you can employ much higher mags, Paul, before drawing any conclusions. Any improvement you might see will be subtle  and won’t be discernible until you can up the magnification 

[Neil_104]

Second that - definitely not a good evening for high mags with this wind (in the UK). I have the Neodymium myself and I find it useful but as Jeremy suggests, it's not transformative. It helps the GRS to stand out, which is handy given it's shrinking size currently. The filter does give quite a blue cast overall to the image, which isn't too overpowering but can be a little off-putting if you like the warm, brownish-yellow tint of the planet. It does make the image v cold looking.

Stick with it though - it's a handy filter to bring out specific features, e.g. to aid with sketching 👍

[Paul Manuell]

1 hour ago, JeremyS said:

Suggest you wait until better conditions, and certainly when you can employ much higher mags, Paul, before drawing any conclusions. Any improvement you might see will be subtle  and won’t be discernible until you can up the magnification 

 

1 hour ago, Neil_104 said:

Second that - definitely not a good evening for high mags with this wind (in the UK). I have the Neodymium myself and I find it useful but as Jeremy suggests, it's not transformative. It helps the GRS to stand out, which is handy given it's shrinking size currently. The filter does give quite a blue cast overall to the image, which isn't too overpowering but can be a little off-putting if you like the warm, brownish-yellow tint of the planet. It does make the image v cold looking.

Stick with it though - it's a handy filter to bring out specific features, e.g. to aid with sketching 👍

Ok, maybe my expectations were too high

[RT65CB-SWL]

19 hours ago, Paul Manuell said:

Well that was a waste of 80 odd quid. Finally had the chance to try out the new neodymium filter on Jupiter tonight, but too windy for high magnification so only went to 50x

Without filter: 2 bands clearly visible

With filter: No bands visible, just a bright, featureless disc

Gutted!

I see from one of your earlier replies that your 'scope is...

On 05/12/2022 at 18:13, Paul Manuell said:

Celestron Astromaster 90AZ

I have a 70mm refractor [TeleVue Ranger]. I can see two equatorial bands/belts without and with my neodymium filter.
There are other things to consider, like how much light pollution? how high was it in the sky? The lower an object is to the horizon, the thicker the atmosphere and dust particulates, etc., and the photons of have to travel through that, before they reach your retina. I read somewhere [at the time posting] that one of the equatorial bands/belts is dimmer than usual too. 

[markse68]

Did you re-focus when you tried the filter Paul? You will need to if you didn't as the thickness of the glass shifts the focus outwards a little. And you need to get Jupiter early in the evening now as it gets too low and mushy later

Mark

[Paul Manuell]

On 13/01/2023 at 20:14, markse68 said:

Did you re-focus when you tried the filter Paul? You will need to if you didn't as the thickness of the glass shifts the focus outwards a little. And you need to get Jupiter early in the evening now as it gets too low and mushy later

Mark

Yes, refocussed. 

An update now though; I managed to use my highest power  (6.5mm/153x) eyepiece on Jupiter just now as it's the first clear, windless night I've had since buying the filter.

View without the filter was exceptional - 2 bands clearly visible. View with the filter and refocussed- 2 bands still clearly visible but stood out a fair bit less than without, so the total opposite of why I bought the filter in the first place. Really disappointed.

PS., anyone want to buy a hardly used neodymium filter at a bargain price? Are sales even allowed on this site?

Edited January 23, 2023 by Paul Manuell
Thought of something else after first draft

[bosun21]

That doesn’t sound right. I use my Baader Neodymium filter frequently on the planet Jupiter and have always found it beneficial. So much so that I sold my contrast booster which I bought when I owned an achromat as I didn’t like the slight yellow hue it produces. Try using the filter again, and this time point it at the star(s) and focus until they are as small as you can get them, then without touching the focuser move to Jupiter. Good luck 👍 

[dweller25]

That is an unusual result @Paul Manuell

I usually see a slight improvement in contrast when I use the Neodymium filter but have noticed it needs to be at ambient temperature for best results.

[mikeDnight]

I really like the basic Wrattan coloured filters for planetary viewing. I rarely use any filters for Jupiter, and only occasionally use them for Mars. They do help when the view is mildly turbulent and seem to steady the view a little. The most useful in my collection at W21 (orange), which enhances the darker albedo markings visible on Mars. And the W80A (blue) enhances the whites, so helps with determining more precisely the positions of clouds, mists, and polar caps. These also work well on all the planets. Also, you may find W11 to W14  (yellow) are good for Jupiter and Venus. Youll find that the larger the aperture the denser the colour needs to be to compensate for the greater ligh grasp of the telescope, so instead of a orange for Mars you may need a red.  However, filters don't improve the detail across the board. They merely enhance certain features often at the cost of blocking out others. The best view will almost always be without a filter when the seeing allows. Venus in a larger aperture scope may benefit from a variable polarizing filter to reduce the glare rather than any particular coloured filter. If you are among the lucky ones who are mildly sensitive to UV, you may see the subtle cloud top detail on Venus without the need of any filter.

[Phillyterp85]

I’ve been wondering this myself.  I’m brand new to astronomy.  I have a 90mm aperture refracting telescope.  This is the view of Jupiter I was able to get the other night.  Can’t really see detail, it just looked like a white circle.   Maybe my focus wasn’t good and that was the issue?  Or is this how it normally looks?

 

[Franklin]

On 27/01/2023 at 13:25, mikeDnight said:

If you are among the lucky ones who are mildly sensitive to UV, you may see the subtle cloud top detail on Venus without the need of any filter.

Wratten #47 Violet can help with this if the aperture is large.

[vlaiv]

On 29/01/2023 at 15:18, Phillyterp85 said:

 Can’t really see detail, it just looked like a white circle.   Maybe my focus wasn’t good and that was the issue?  Or is this how it normally looks?

You are way off with your focus there.

 

[Phillyterp85]

5 hours ago, vlaiv said:

You are way off with your focus there.

 

Ok great thanks for the feedback.   When adjusting the focus, it ranged from tiny bright dot to what is shown in the photo.   My scope is 700 mm length x 90mm aperture, and I was using a 9mm eyepiece.

So am I correct in saying that my magnification was at 78x with that setup?

I’ve googled images of Jupiter with various magnifications, and at 78x magnification it looks like Jupiter should be much smaller than what it looked like in my scope.  So I will try again and adjust the focus.

 

[vlaiv]

1 minute ago, Phillyterp85 said:

Ok great thanks for the feedback.   When adjusting the focus, it ranged from tiny bright dot to what is shown in the photo.   My scope is 700 mm length x 90mm aperture, and I was using a 9mm eyepiece.

So am I correct in saying that my magnification was at 78x with that setup?

I’ve googled images of Jupiter with various magnifications, and at 78x magnification it looks like Jupiter should be much smaller than what it looked like in my scope.  So I will try again and adjust the focus.

 

It is very hard to depict what is seen at the eyepiece when looking at computer screen image.

First - you need to be at exactly "prescribed" distance from computer screen in order to make Jupiter image on the screen appear the same size in the eyepiece - and that will depend on pixel pitch of the screen used.

Second - there are various cognitive effects that come into play. When looking at the eyepiece - one just sees patch of the sky and a planet. There are no reference points to be able to judge size.

You are correct - 9mm eyepiece with 700mm FL gives about x78 magnification.

That is actually plenty of magnification for target like Jupiter. If current apparent diameter of Jupiter is ~36" - then x78 magnification will make it about x1.5 larger than the full moon when viewed with naked eye.

We can see some features on the full moon - and yes, you should be able to see some features on Jovian disk at x78 as well. At least main belts.

Here is handy way of knowing if you have focus right - you already know that Jupiter will look like large circle when out of focus. You can use that circle to roughly judge where is correct focus position. As you change focus (rotate focuser knob) - diameter of that circle will change - it will either grow or shrink - you should go in direction of shrinking the circle.

At some point - circle will be the smallest and if you continue rotating knob in same direction - it will start to grow again.

This point where circle is the smallest is place of actual focus. Once you reach it - pay attention to the detail on the planet and try to tease out detail - tweak the focus as needed to make features on planet sharp. Do be careful - there is spot just before perfect focus that focuses on disturbance in our atmosphere rather than planet itself - if you focus on that - you will see actual air - much like warm air over fire - distorting the planet. You don't want to focus on that - try to focus on actual planet, but do understand that atmosphere will make it difficult as everything will dance around more or less (depends how calm the atmosphere is).

[pipnina]

9 minutes ago, vlaiv said:

Do be careful - there is spot just before perfect focus that focuses on disturbance in our atmosphere rather than planet itself - if you focus on that - you will see actual air - much like warm air over fire - distorting the planet. You don't want to focus on that - try to focus on actual planet, but do understand that atmosphere will make it difficult as everything will dance around more or less (depends how calm the atmosphere is).

I didn't realise the turbulence and astronomical objects could be at different focal positions! I guess I imagined it would all be at too high an altitude or that turbulence would affect the image whether it was in focus or not.

I guess it does bring back an interesting tidbit: Apparently most of the turbulence on an average night comes from within 10 meters of the ground, I believe that was on some observatory's website but I cannot remember now.

[vlaiv]

1 minute ago, pipnina said:

I didn't realise the turbulence and astronomical objects could be at different focal positions! I guess I imagined it would all be at too high an altitude or that turbulence would affect the image whether it was in focus or not.

I guess it does bring back an interesting tidbit: Apparently most of the turbulence on an average night comes from within 10 meters of the ground, I believe that was on some observatory's website but I cannot remember now.

I particularly notice this effect in few cases - one of them is observing a planet as it moves over houses in winter that burn fuel for heating. You can unmistakably spot when planet moves over the chimney.

Another time is when there is strong jet stream over head - one can focus on jet stream disturbance.

In both cases - it is very distinct sight and resembles the most jet exhaust from an airplane

https://www.youtube.com/watch?v=PGOzLeq-JpQ

see 2:20 and onward as F-35s taxi on runway. That building in the background - just replace it with lunar feature or Jupiter.

[Phillyterp85]

30 minutes ago, vlaiv said:

It is very hard to depict what is seen at the eyepiece when looking at computer screen image.

First - you need to be at exactly "prescribed" distance from computer screen in order to make Jupiter image on the screen appear the same size in the eyepiece - and that will depend on pixel pitch of the screen used.

Second - there are various cognitive effects that come into play. When looking at the eyepiece - one just sees patch of the sky and a planet. There are no reference points to be able to judge size.

You are correct - 9mm eyepiece with 700mm FL gives about x78 magnification.

That is actually plenty of magnification for target like Jupiter. If current apparent diameter of Jupiter is ~36" - then x78 magnification will make it about x1.5 larger than the full moon when viewed with naked eye.

We can see some features on the full moon - and yes, you should be able to see some features on Jovian disk at x78 as well. At least main belts.

Here is handy way of knowing if you have focus right - you already know that Jupiter will look like large circle when out of focus. You can use that circle to roughly judge where is correct focus position. As you change focus (rotate focuser knob) - diameter of that circle will change - it will either grow or shrink - you should go in direction of shrinking the circle.

At some point - circle will be the smallest and if you continue rotating knob in same direction - it will start to grow again.

This point where circle is the smallest is place of actual focus. Once you reach it - pay attention to the detail on the planet and try to tease out detail - tweak the focus as needed to make features on planet sharp. Do be careful - there is spot just before perfect focus that focuses on disturbance in our atmosphere rather than planet itself - if you focus on that - you will see actual air - much like warm air over fire - distorting the planet. You don't want to focus on that - try to focus on actual planet, but do understand that atmosphere will make it difficult as everything will dance around more or less (depends how calm the atmosphere is).

Thank you so much for the tip on focus!  Im assuming that focusing strategy works on any object im trying to get a focus on?