12 replies to this topic

[oldtimer]

I have a 90mm F 8.9 Meade achro refractor. Lots of advice here on filters. However, I'm not bothered by the slight CA my scope produces what I'm interested in is seeing maximum detail. I'm only interested in opinions on filters for that purpose.

 

Gary (oldtimer)

[Dave Mitsky]

A light blue Wratten #80A filter may enhance the GRS somewhat.

[happylimpet]

A light blue Wratten #80A filter may enhance the GRS somewhat.

I was thinking along these lines. As the structure on Jupiter is primarily shades of red/brown, it has higher contrast in blue light. Also, a small scope like that probably shows better resolution in blue (larger scopes are limited by atmospherics, so are usually sharper in red).

[gstrumol]

If you can believe the marketing hype then both light blue #80A and light green #56 will increase the visibility of the GRS, and orange #21 will improve the appearance & detail in the belts, while enhancing the view of festoons and the polar regions.

[Sketcher]

With a 90mm scope, it would be best to avoid darker (lower light transmission) filters -- regardless of color.  This due to the brightness (dimness really) of your Jupiter views when sufficiently high magnifications are used.  With denser filters the image would become darkened so much that all features would become muted.

 

Yeah, a light (pale) blue would likely become your favorite -- for all the larger, higher-contrast brownish and reddish features that Jupiter tends to have.  But beware, a blue filter will decrease the contrast of the bluish Jovian features.  So, other light (high-transmission) colored filters would better reveal those features -- while lowering the contrast of all of those red/brown features.  Such is the nature of using color filters.  For any given color, some features will show improved contrast, while other features would show a reduction in contrast.

 

Get a variety of light, high-transmission colored filters and experiment.

 

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Note:  If you've not been spending an hour or thereabouts at a time with your Jupiter observations, combined with making sketches, then these two approaches would likely reveal more details than would the use of filters.

 

All too often (not necessarily in your situation) people start buying more stuff in their attempts to see more, when really they've yet to learn how to "see" when using an astronomical telescope.  Increased experience will tend to improve what one is able to see more than will the use of colored filters -- at least until one has gained sufficient experience.  The advantages of using colored filters are usually of a quite subtle nature -- so much so that many have come to the (erroneous) conclusion that colored filters are a waste of money.

 

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A filter that reduces CA would also (subtly) improve your overall planetary contrast.  I wouldn't entirely rule out the advantages of using such filters.  I rather like using a Baader 495 LongPass Yellow filter for such purposes with a 6-inch f/6.5 achromat that has more severe CA than does your fine achromat.

 

Afterall, in most cases, the advantages in the use of any of the colored filters are going to be quite subtle.  So much so that many fail to notice any of the advantages.

[oldtimer]

All good advice. When the temperature starts to warm up, I will have more patience at the eyepiece to experiment.

 

Gary (oldtimer) 

[Dave Mitsky]

If you’re willing to spend a lot more, the Baader Moon and Skyglow filter does a nice job on Jupiter and is also effective to a lesser degree on Mars.

[Sebastian_Sajaroff]

Baader Contrast Booster filter gave me some improvement on Jupiter and Mars using my 70 mm refractor.

Also enhanced the view of the Moon, planets and stars at daytime.

Of course, you still need good seeing conditions to make the most of small telescopes.

[Cpk133]

You don’t need any filters, just good astronomical seeing. 

[antarex]

Still on the subject of seeing... I imagine that even a planetary disk (any planet and not Jupiter specifically) defined, but of uniform color and without details, is due to seeing. Right?
I was just observing Mars last night at 166x (with my SC6), and although at times the planetary disk was defined, it was completely uniform (the classic orange tending towards white) and there was no trace of a polar cap to the north and dark areas to the south, as expected.

 

ps: to supplement what I wrote, I used a 9mm Celestron Plossl Omni eyepiece.
Maybe it depends on the eyepiece, and not from seeing?
Maybe with an Abbe orthoscopic, I could improve the sharpness and contrast and notice something?

Edited by antarex, 17 March 2025 - 05:42 AM.

[Cpk133]

Still on the subject of seeing... I imagine that even a planetary disk (any planet and not Jupiter specifically) defined, but of uniform color and without details, is due to seeing. Right?
I was just observing Mars last night at 166x (with my SC6), and although at times the planetary disk was defined, it was completely uniform (the classic orange tending towards white) and there was no trace of a polar cap to the north and dark areas to the south, as expected.

 

ps: to supplement what I wrote, I used a 9mm Celestron Plossl Omni eyepiece.
Maybe it depends on the eyepiece, and not from seeing?
Maybe with an Abbe orthoscopic, I could improve the sharpness and contrast and notice something?

In my experience, seeing effects can vary in frequency and amplitude.  Sometimes a planet can look like its on a flag, twisting and writhing too and fro.  Then there’s high frequency fuzz where things appear relatively stationary but nothing comes to sharp focus to include the limb, everything just looks blank.  The moon is one of the best subjects that reveals the true nature of seeing, but you can use any bright object / star.  Try slowly racking the focuser (CCW in a cat / extending the drawtube in a refractor) while you observe the bright object.  What this does is slowly move the focus through layers in the atmosphere getting closer to ground level as the focuser is turned.  When the seeing is bad, you can literally focus on the jet stream and it will look like a river of fluid.  If the problem is in your scope, you will eventually see the telltale plume of hot air rising from the baffle tube or worm like disturbances slowly moving through the field of view (boundary layer from a warm mirror).  Every type of optical tube has its own characteristics.  You can always just point your scope at a star. If you don’t see a diffraction pattern, the seeing isn’t good enough for that scopes potential resolving power.  
 

as far as the eyepiece goes, the difference between a plossl and ortho will be very subtle if you even notice a difference.  A binoviewer has the biggest contrast improvement of any accessory when it comes to planets IMHO.  Some people don’t get along but I think they’re worth the outlay and the little bit of added fiddle (IPD, collimation, back focus etc)

 

edit on the fuzz:  sometimes i think this effect can be caused by high altitude ice crystals aka stratus haze, just a fuzzy murk.

Edited by Cpk133, 17 March 2025 - 08:46 AM.

[JOEinCO]

If you've not been spending an hour or thereabouts at a time with your Jupiter observations, combined with making sketches, then these two approaches would likely reveal more details than would the use of filters....

 

Sage advice!   

[antarex]

In my experience, seeing effects can vary in frequency and amplitude.  Sometimes a planet can look like its on a flag, twisting and writhing too and fro.  Then there’s high frequency fuzz where things appear relatively stationary but nothing comes to sharp focus to include the limb, everything just looks blank.  The moon is one of the best subjects that reveals the true nature of seeing, but you can use any bright object / star.  Try slowly racking the focuser (CCW in a cat / extending the drawtube in a refractor) while you observe the bright object.  What this does is slowly move the focus through layers in the atmosphere getting closer to ground level as the focuser is turned.  When the seeing is bad, you can literally focus on the jet stream and it will look like a river of fluid.  If the problem is in your scope, you will eventually see the telltale plume of hot air rising from the baffle tube or worm like disturbances slowly moving through the field of view (boundary layer from a warm mirror).  Every type of optical tube has its own characteristics.  You can always just point your scope at a star. If you don’t see a diffraction pattern, the seeing isn’t good enough for that scopes potential resolving power.  
 

as far as the eyepiece goes, the difference between a plossl and ortho will be very subtle if you even notice a difference.  A binoviewer has the biggest contrast improvement of any accessory when it comes to planets IMHO.  Some people don’t get along but I think they’re worth the outlay and the little bit of added fiddle (IPD, collimation, back focus etc)

 

edit on the fuzz:  sometimes i think this effect can be caused by high altitude ice crystals aka stratus haze, just a fuzzy murk.

Thanks for the explanation and advice on the binocular viewer. But with the latter I imagine that you have to do all the adjustments that are made for binoculars... so, in addition to having to focus the telescope, also adjust the focus and diopter of the binocular viewer.
For the moment then, rather than thinking about changing the eyepiece, I will wait for better seeing and see if the problem was the latter.