Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

The Sweet Spot

  • Please log in to reply
20 replies to this topic

#1 vdog

vdog

    Viking 1

  • *****
  • topic starter
  • Posts: 747
  • Joined: 30 Aug 2018
  • Loc: California Central Valley, U.S.A.

Posted 12 May 2019 - 09:57 AM

Hello everyone,

 

I've finally found my "sweet spot" for Saturn.  I'd already found it for Jupiter.  I have yet to find it for other planets so I'm curious to find out what others think before the other planets come around again.

 

To clarify my question, I would ask that you not consider magnifications you use for particular purposes, like watching an Io transit or targeting the Encke gap. I would also ask that you assume decent / good (but not necessarily excellent) seeing. I'm also focusing on the nearest planets but feel free to add Mercury, Uranus, and Neptune if you observe them often.

 

By "sweet spot" I mean the magnification / exit pupil where you just sit and enjoy the view, drinking in just enough detail to make it a thoroughly rewarding experience.  I would also ask that you include the equipment you use as considerations like tracking and FOV will no doubt affect your answer.   Here are mine:

 

Scope:  Manual 10" dob

 

Jupiter (218x) Meade UWA 5.5

Saturn (300x) SW Nirvana 4

Mars: ???? (might consider picking up a 3.5 in 2020)

Venus: ???? (totally clueless here, is there a "sweet spot" where some cloud detail might be visible?)

 

What are your "sweet spots"?  Thanks for reading.  Thanks for playing.


Edited by vdog, 12 May 2019 - 09:59 AM.


#2 Allan Wade

Allan Wade

    Soyuz

  • *****
  • Posts: 3631
  • Joined: 27 Jan 2013
  • Loc: Newcastle, Australia

Posted 13 May 2019 - 04:34 AM

Making my all time top 3 eyepiece views was Jupiter at 909x in a 32” under an exceedingly steady Florida sky. That was a sweet spot I’ll remember forever.


  • erin and vdog like this

#3 Special Ed

Special Ed

    Voyager 1

  • *****
  • Posts: 10108
  • Joined: 18 May 2003
  • Loc: Greenbrier County, WV 38N, 80W

Posted 13 May 2019 - 11:15 AM

Making my all time top 3 eyepiece views was Jupiter at 909x in a 32” under an exceedingly steady Florida sky. That was a sweet spot I’ll remember forever.

Alan,

 

Sounds like Nirvana smile.gif  but the OP was talking about decent to good seeing--not that heavenly stuff they get in Florida.  BTW, a friend of mine was at the WSP one year and had the same experience you describe, except with Mars.

 

My sweet spot for Jupiter with my gear (observatory mounted C14 with tracking) is 244x.  Jupiter has such a large angular diameter that this gives me a good image scale.  More than that and the view gets soft and/or loses contrast under my usual conditions.

 

For Saturn it's usually 326x and occasionally 391x.  But, with the caveat that the gas giants are low for us northern hemisphere observers right now.

 

For Mars there is no sweet spot.  I just push the magnification as high as I can for the conditions on any given night.  The upper limit is usually 391x.

 

For Venus I use 200x-300x but that's in daylight or twilight with Venus at as high an altitude as possible.  Cloud variation is possible to see, especially if you employ filters

 

I don't observe the ice giants very often, but the last time I looked at Uranus I switched between 652x and 489x.  High magnification is important to get any sort of decent image scale.

 

Naturally, these high power views are made much more convenient by a tracking mount, especially since I almost always make a sketch,


Edited by Special Ed, 13 May 2019 - 11:20 AM.

  • Paul Morow, Allan Wade, happylimpet and 1 other like this

#4 vdog

vdog

    Viking 1

  • *****
  • topic starter
  • Posts: 747
  • Joined: 30 Aug 2018
  • Loc: California Central Valley, U.S.A.

Posted 13 May 2019 - 02:41 PM

Alan,

 

Sounds like Nirvana smile.gif  but the OP was talking about decent to good seeing--not that heavenly stuff they get in Florida.  BTW, a friend of mine was at the WSP one year and had the same experience you describe, except with Mars.

 

My sweet spot for Jupiter with my gear (observatory mounted C14 with tracking) is 244x.  Jupiter has such a large angular diameter that this gives me a good image scale.  More than that and the view gets soft and/or loses contrast under my usual conditions.

 

For Saturn it's usually 326x and occasionally 391x.  But, with the caveat that the gas giants are low for us northern hemisphere observers right now.

 

For Mars there is no sweet spot.  I just push the magnification as high as I can for the conditions on any given night.  The upper limit is usually 391x.

 

For Venus I use 200x-300x but that's in daylight or twilight with Venus at as high an altitude as possible.  Cloud variation is possible to see, especially if you employ filters

 

I don't observe the ice giants very often, but the last time I looked at Uranus I switched between 652x and 489x.  High magnification is important to get any sort of decent image scale.

 

Naturally, these high power views are made much more convenient by a tracking mount, especially since I almost always make a sketch,

Interesting.  Even with tracking, your Jupiter / Saturn sweet spots are pretty close to mine, which take into account having sufficient time to enjoy the view in between manually re-adjusting the positioning.

 

For Mars, I do plan to push the envelope.  It's pretty tiny even at opposition and the seeing in my area is usually pretty decent, so why not?  But eventually I'm going to reach a threshold where I'll just be chasing the planet so I don't know about even attempting to exceed 400x.   Maybe someday if I have a SCT.

 

What filters would you recommend for cloud detail on Venus?  I have an ND and various colors.



#5 EverlastingSky

EverlastingSky

    Viking 1

  • *****
  • Posts: 909
  • Joined: 12 Sep 2006
  • Loc: Vancouver Canada

Posted 13 May 2019 - 02:53 PM

Hello everyone,

 

I've finally found my "sweet spot" for Saturn.  I'd already found it for Jupiter.  I have yet to find it for other planets so I'm curious to find out what others think before the other planets come around again.

 

To clarify my question, I would ask that you not consider magnifications you use for particular purposes, like watching an Io transit or targeting the Encke gap. I would also ask that you assume decent / good (but not necessarily excellent) seeing. I'm also focusing on the nearest planets but feel free to add Mercury, Uranus, and Neptune if you observe them often.

 

By "sweet spot" I mean the magnification / exit pupil where you just sit and enjoy the view, drinking in just enough detail to make it a thoroughly rewarding experience.  I would also ask that you include the equipment you use as considerations like tracking and FOV will no doubt affect your answer.   Here are mine:

 

Scope:  Manual 10" dob

 

Jupiter (218x) Meade UWA 5.5

Saturn (300x) SW Nirvana 4

Mars: ???? (might consider picking up a 3.5 in 2020)

Venus: ???? (totally clueless here, is there a "sweet spot" where some cloud detail might be visible?)

 

What are your "sweet spots"?  Thanks for reading.  Thanks for playing.

 

  • Venus: Dusky albedo cloud features were visible with an old Vixen 80mm f/11.3 at around 121x with 7.5mm Celestron "Halloween" Ultima eyepiece operating at 0.66mm exit pupil. Have not really had the opportunity to view Venus since I sold these scope' however. Too many trees in the way.
  • Mercury: 2005 with Vixen 80mm f/11.3 with Radian 5mm and 6mm at 151x 182x, yellow "Lunar" like color with some hint of patchy albedo? The seeing was tranquil and the evening apparition well above the trees in a bright twilight sky. I would like to view Mercury again, but, with endless trees around it would require an expedition to a different site.
  • Mars: August 27 2003 with Vixen 80mm f/11.3 and 7.5mm Ultima yielding 121x at 0.66 exit pupil. The Great Opposition. Drank in the views. Such sights... are rubbish compared to what they see at the WSP in those mega dobs. But still, it was enough to mess up my mind grin.gif
  • Saturn: Many memorable views. Current sweet spot last 2 years has been 140x at 1mm exit pupil from a pair of 7mm Delites in a binoviewer on a TEC140. Saturn at 17 degrees altitude from up here makes for poor views generally. A pair of 5.1mm at 192x, when usable on some nights, despite the low altitude, have rendered, in my opinion, exquisite vistas. I am very sensitive to colors and find them to be, at times, overwhelmingly beautiful. When conditions allow I find Saturn conveys a type of... waxy avocado green which is an indicator of good transparency to my mind.
  • Jupiter: Same as above. That 140x in a binoviewer is potent. Relaxed viewing is usually to be had at 1mm exit pupil after all, right? Colors are rich and, at times, utterly sublime. Seeing and transparency dependant of course. When conditions allow then a pair of 5.1mm at 192x become usable. When that happens the fine filament structure and convolutions within the main belts are addictive. Pale grays transitioning to clay blue in the festoons were a big surprise at this aperture. Big grin time waytogo.gif  
  • Jupiter in small TV60 (60mm f/6): With only 360mm focal length the Nagler 2-4 Zoom was a jaw dropper on Jupiter in past years. During those clear crisp tranquil February nights I experienced very memorable views of the Moons in transit. Now this is where it gets a bit controversial: Small exit pupils ranging from the 4mm setting (90x at 0.66 exit pupil) to the 2mm setting (180x at 0.33 exit pupil) were very satisfying. No major floater problem noted. I ran out of magnification one night at 180x and still the image held. Still Ganymede was a little brown cookie crumb sat atop the cloud belts. Conclusion? 60mm is near invincible to seeing and under great nights is operating at full potential of what the aperture can show. The TEC140 has been severely handicapped by my bad seeing conditions most of the time. Just little glimpses of goodness shine through from time to time. Hints of what the instrument could be capable of under proper skies.

  • Lewis Cason, Paul Morow and vdog like this

#6 Special Ed

Special Ed

    Voyager 1

  • *****
  • Posts: 10108
  • Joined: 18 May 2003
  • Loc: Greenbrier County, WV 38N, 80W

Posted 13 May 2019 - 03:47 PM

Interesting.  Even with tracking, your Jupiter / Saturn sweet spots are pretty close to mine, which take into account having sufficient time to enjoy the view in between manually re-adjusting the positioning.

 

For Mars, I do plan to push the envelope.  It's pretty tiny even at opposition and the seeing in my area is usually pretty decent, so why not?  But eventually I'm going to reach a threshold where I'll just be chasing the planet so I don't know about even attempting to exceed 400x.   Maybe someday if I have a SCT.

 

What filters would you recommend for cloud detail on Venus?  I have an ND and various colors.

Yes, the Jupiter and Saturn magnifications are close but your dob is probably f/4.5?  So it has a wider field at those magnifications which helps you limit the nudge factor.  The C14 is f/11 and has a very small FOV so without tracking the object flies through the field.

 

Mars is relatively high contrast compared to the contrast of the cloudtops of the gas giants so it can take a lot of magnification so crank it as high as you comfortably can.

 

For Venus, I suggest you just experiment with your ND and color filters and see what seems to work.  I've had some luck with the Wratten 80A (lt. blue) and W11 (yellow-green) both separately and stacked.  I've also used the W23A (red).  Some use a W47 (violet) but it's pretty dark unless you have a lot of aperture. 

 

Don't forget to look without filters, too (IL).  The key is to observe Venus in daylight or early twilight when the planet is higher and glare is minimized.  I started this observation with my C8 (before I had the C14) at 200x at 8:25 PM EDT (about a half hour before local sunset).  It will give you an idea of some of the subtle contrast differences that can be detected in the Venusian cloudtops.

 

Venus_6.19.07.v1.JPG


  • Dave Mitsky, barbie and vdog like this

#7 vdog

vdog

    Viking 1

  • *****
  • topic starter
  • Posts: 747
  • Joined: 30 Aug 2018
  • Loc: California Central Valley, U.S.A.

Posted 13 May 2019 - 05:22 PM

 

  • Venus: Dusky albedo cloud features were visible with an old Vixen 80mm f/11.3 at around 121x with 7.5mm Celestron "Halloween" Ultima eyepiece operating at 0.66mm exit pupil. Have not really had the opportunity to view Venus since I sold these scope' however. Too many trees in the way.
  • Mercury: 2005 with Vixen 80mm f/11.3 with Radian 5mm and 6mm at 151x 182x, yellow "Lunar" like color with some hint of patchy albedo? The seeing was tranquil and the evening apparition well above the trees in a bright twilight sky. I would like to view Mercury again, but, with endless trees around it would require an expedition to a different site.
  • Mars: August 27 2003 with Vixen 80mm f/11.3 and 7.5mm Ultima yielding 121x at 0.66 exit pupil. The Great Opposition. Drank in the views. Such sights... are rubbish compared to what they see at the WSP in those mega dobs. But still, it was enough to mess up my mind grin.gif
  • Saturn: Many memorable views. Current sweet spot last 2 years has been 140x at 1mm exit pupil from a pair of 7mm Delites in a binoviewer on a TEC140. Saturn at 17 degrees altitude from up here makes for poor views generally. A pair of 5.1mm at 192x, when usable on some nights, despite the low altitude, have rendered, in my opinion, exquisite vistas. I am very sensitive to colors and find them to be, at times, overwhelmingly beautiful. When conditions allow I find Saturn conveys a type of... waxy avocado green which is an indicator of good transparency to my mind.
  • Jupiter: Same as above. That 140x in a binoviewer is potent. Relaxed viewing is usually to be had at 1mm exit pupil after all, right? Colors are rich and, at times, utterly sublime. Seeing and transparency dependant of course. When conditions allow then a pair of 5.1mm at 192x become usable. When that happens the fine filament structure and convolutions within the main belts are addictive. Pale grays transitioning to clay blue in the festoons were a big surprise at this aperture. Big grin time waytogo.gif  
  • Jupiter in small TV60 (60mm f/6): With only 360mm focal length the Nagler 2-4 Zoom was a jaw dropper on Jupiter in past years. During those clear crisp tranquil February nights I experienced very memorable views of the Moons in transit. Now this is where it gets a bit controversial: Small exit pupils ranging from the 4mm setting (90x at 0.66 exit pupil) to the 2mm setting (180x at 0.33 exit pupil) were very satisfying. No major floater problem noted. I ran out of magnification one night at 180x and still the image held. Still Ganymede was a little brown cookie crumb sat atop the cloud belts. Conclusion? 60mm is near invincible to seeing and under great nights is operating at full potential of what the aperture can show. The TEC140 has been severely handicapped by my bad seeing conditions most of the time. Just little glimpses of goodness shine through from time to time. Hints of what the instrument could be capable of under proper skies.

 

Thank you for the extremely detailed response.   I hear so many good things about planets and binoviewing.  Will have to try someday if / when I can afford the necessary gear.



#8 vdog

vdog

    Viking 1

  • *****
  • topic starter
  • Posts: 747
  • Joined: 30 Aug 2018
  • Loc: California Central Valley, U.S.A.

Posted 13 May 2019 - 05:34 PM

Yes, the Jupiter and Saturn magnifications are close but your dob is probably f/4.5?  So it has a wider field at those magnifications which helps you limit the nudge factor.  The C14 is f/11 and has a very small FOV so without tracking the object flies through the field.

 

Mars is relatively high contrast compared to the contrast of the cloudtops of the gas giants so it can take a lot of magnification so crank it as high as you comfortably can.

 

For Venus, I suggest you just experiment with your ND and color filters and see what seems to work.  I've had some luck with the Wratten 80A (lt. blue) and W11 (yellow-green) both separately and stacked.  I've also used the W23A (red).  Some use a W47 (violet) but it's pretty dark unless you have a lot of aperture. 

 

Don't forget to look without filters, too (IL).  The key is to observe Venus in daylight or early twilight when the planet is higher and glare is minimized.  I started this observation with my C8 (before I had the C14) at 200x at 8:25 PM EDT (about a half hour before local sunset).  It will give you an idea of some of the subtle contrast differences that can be detected in the Venusian cloudtops.

 

attachicon.gif Venus_6.19.07.v1.JPG

f/4.7

 

I tried 400x last year on Mars but that EP (an Orion Edge-on) had too narrow a field so I was never able to get comfortable at that magnification.  Next year, I might try to pick up a used 3.5 Nagler for Mars and maybe Uranus / Neptune as well.

 

Thank you for the suggestions on Venus.   I haven't been able to see anything but a phased disk so far, so I'm looking forward to trying them out.



#9 Rich (RLTYS)

Rich (RLTYS)

    Fly Me to the Moon

  • *****
  • Posts: 6651
  • Joined: 18 Dec 2004
  • Loc: Mayo (Maryland)

Posted 14 May 2019 - 06:22 AM

The sweet spot with my 10" refl is 254x. This is the magnification I always start with.



#10 vdog

vdog

    Viking 1

  • *****
  • topic starter
  • Posts: 747
  • Joined: 30 Aug 2018
  • Loc: California Central Valley, U.S.A.

Posted 14 May 2019 - 11:59 AM

The sweet spot with my 10" refl is 254x. This is the magnification I always start with.

That used to be my go-to magnification for Saturn, but it left me wanting a bit more, so I got a 4mm EP.

 

Jupiter seems a bit too much "in my face" at that magnification so I actually prefer 218x for Jupiter.  I may use the higher magnifications next time the Great Red Spot is out to take a closer look at that feature, though.


Edited by vdog, 14 May 2019 - 01:30 PM.


#11 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 76117
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 14 May 2019 - 02:30 PM

Yes, the Jupiter and Saturn magnifications are close but your dob is probably f/4.5?  So it has a wider field at those magnifications which helps you limit the nudge factor.  The C14 is f/11 and has a very small FOV so without tracking the object flies through the field.

 

 

The true field of view depends on the AFoV and the magnification, focal ratio is not a factor. An 80 degree AFoV eyepiece at 400x is always 80 deg /400 = 0.2 deg TFoV.

 

The sweet spot, as I think of it, is the region of the field of view that is essentially perfect, outside of the sweet spot, the view of a planet degrades.

 

Jon

 

Jon



#12 Special Ed

Special Ed

    Voyager 1

  • *****
  • Posts: 10108
  • Joined: 18 May 2003
  • Loc: Greenbrier County, WV 38N, 80W

Posted 15 May 2019 - 06:39 AM

The true field of view depends on the AFoV and the magnification, focal ratio is not a factor. An 80 degree AFoV eyepiece at 400x is always 80 deg /400 = 0.2 deg TFoV.

 

The sweet spot, as I think of it, is the region of the field of view that is essentially perfect, outside of the sweet spot, the view of a planet degrades.

Jon,

 

Of course, you are correct--my mistake.  I guess I was thinking about those widefield views you can get with a focal ratio like f/4.5 or 4.7.  But that would be at lower magnification than what we were discussing.  And the field would be the same with the same AFOV and magnification no matter what the f/r as you point out.

 

I agree with your definition of the sweet spot in an eyepiece field.  The PST for instance has a very well defined sweet spot.  The OP described what he meant by "sweet spot" in his first post.


Edited by Special Ed, 15 May 2019 - 08:19 AM.

  • Jon Isaacs likes this

#13 vdog

vdog

    Viking 1

  • *****
  • topic starter
  • Posts: 747
  • Joined: 30 Aug 2018
  • Loc: California Central Valley, U.S.A.

Posted 15 May 2019 - 11:33 AM

I think both definitions of "sweet spot" can certainly apply.  Mine applies to the observer, Jon's to the tool.

 

I suppose it may be a result of my inexperience (if so, then ignorance is bliss), but I don't really notice any eyepiece aberrations when observing planets. 

 

Of course, now that I understand what field curvature and astigmatism are, I can't help but notice them when I observe stars.  Maybe I shouldn't have read all those threads on the eyepiece forum. foreheadslap.gif



#14 dscarpa

dscarpa

    Soyuz

  • *****
  • Posts: 3605
  • Joined: 15 Mar 2008
  • Loc: San Diego Ca.

Posted 15 May 2019 - 09:28 PM

 I  use 275X-350X  most often on all planets and the Moon with my C9.25, IM 715D and WO ZS110.  I used to use less magnification with my refractor but recently started pushing and the performance gap between it and my cats narrowed.   I've seen cloud detail on Venus without filters  with all my scopes, the mak shows it best.  No tracking and I use premium 65*-100* eyepieces except for a barlowed 5 XO sometimes in the WO ZS110. I really have to give my Brandons  more scope time. David


Edited by dscarpa, 16 May 2019 - 09:44 AM.

  • vdog likes this

#15 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 76117
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 16 May 2019 - 07:00 AM

I think both definitions of "sweet spot" can certainly apply.  Mine applies to the observer, Jon's to the tool.

 

I suppose it may be a result of my inexperience (if so, then ignorance is bliss), but I don't really notice any eyepiece aberrations when observing planets. 

 

Of course, now that I understand what field curvature and astigmatism are, I can't help but notice them when I observe stars.  Maybe I shouldn't have read all those threads on the eyepiece forum. foreheadslap.gif

 

Those same aberrations are there and affect the view of the planets.  Coma doesn't show itself as tails on the planet, it shows itself as a softer view, reduced contrast.  

 

The "coma free", diffraction limited field of a 10 inch F/4.7 is 0.11 degrees or  about 6.5 arcminutes.  At 200x, that is 22 degrees AFoV.  Without a coma corrector, the planet will be sharpest in the very center of the field and there will be a "sweet spot" where the view seems clean and sharp but as it drifts, the image will not be as sharp and clean.  

 

In terms of magnification, on a good night, I generally use around 400x for viewing the planets in either the 10 inch F/5 or the 13.1 inch F/5.5.  I make the judgment based on the crispness of the view.  

 

Jon



#16 vdog

vdog

    Viking 1

  • *****
  • topic starter
  • Posts: 747
  • Joined: 30 Aug 2018
  • Loc: California Central Valley, U.S.A.

Posted 16 May 2019 - 10:05 AM

In terms of magnification, on a good night, I generally use around 400x for viewing the planets in either the 10 inch F/5 or the 13.1 inch F/5.5.  I make the judgment based on the crispness of the view.  

 

Jon

I've noticed that, even here in the Central Valley, the seeing in California generally seems to be better than what I hear reported from CN members in other parts of the country who say they rarely exceed 250x. 

 

I really didn't expect 300x to look as good as it did, so, sweet spot or no, I think I'm going to look to push the envelope further (for ring and band detail, Mars, Uranus and Neptune, etc.).



#17 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 14838
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 16 May 2019 - 10:49 AM

I interpret sweet spot to be optimal magnification, but it makes sense Jupiter should be as aberration free as possible.

My sweet spot for Jove is about 240x or 0.6mm exit pupil. Above that, Jove begins to dim at smaller exit pupils and larger image scales.

Saturn and the moon get a little over 300x or 0.5mm exit pupil. I've gone higher in the moon with no real improvement, but have not tried higher on Saturn.

Mars and Ganymede can take upwards of 400x or 0.4mm exit pupil and a bit more to good effect.

I rarely observe Venus, so no idea. Never seen any markings, just a bright crescent mostly.

The outer giants, I agree with others, as much magnification as I can comfortably give them. Same with double stars with magnification upwards of 500x or 0.3mm exit pupil.

For the sake of completeness, small bright galaxies between 100x and 150x or 1.x mm exit pupils, and small bright planetaries upards of 300x and 0.5mm exit pupil. Most others vary quite a bit.
  • Pinbout and vdog like this

#18 barbie

barbie

    Viking 1

  • *****
  • Posts: 823
  • Joined: 28 Jan 2013
  • Loc: Northeast Ohio

Posted 16 May 2019 - 09:52 PM

I rarely exceed 250x here in N.E. Ohio and mostly use between 185x and 220x.  My sweet spot usually lies half way between these two magnifications.  There are rare exceptions where > 235X is excellent(like last summer) and I do have an eyepiece ready in the "stable" for just such a night!!



#19 vdog

vdog

    Viking 1

  • *****
  • topic starter
  • Posts: 747
  • Joined: 30 Aug 2018
  • Loc: California Central Valley, U.S.A.

Posted 18 May 2019 - 04:20 PM

I rarely exceed 250x here in N.E. Ohio and mostly use between 185x and 220x.  My sweet spot usually lies half way between these two magnifications.  There are rare exceptions where > 235X is excellent(like last summer) and I do have an eyepiece ready in the "stable" for just such a night!!

I'm going to count myself blessed even with the other observational challenges I face in my location.  The seeing was just ok this morning, but I was still able to use 218-300x with some success on Jupiter and Saturn. 



#20 vdog

vdog

    Viking 1

  • *****
  • topic starter
  • Posts: 747
  • Joined: 30 Aug 2018
  • Loc: California Central Valley, U.S.A.

Posted 18 May 2019 - 04:28 PM

For Venus, I suggest you just experiment with your ND and color filters and see what seems to work.  I've had some luck with the Wratten 80A (lt. blue) and W11 (yellow-green) both separately and stacked.  I've also used the W23A (red).  Some use a W47 (violet) but it's pretty dark unless you have a lot of aperture.

So, I went ahead and ordered a #47.  I know I won't have an angle on Venus for awhile, but my "buy new gear" itch needed to be scratched and it wasn't that expensive.  I already have green, blue, red, and yellow (although I'm not sure which ones since my cheapie color set doesn't display the Wratten numbers).

 

If it's dark that will be fine since Venus is ridiculously bright anyway.  Maybe I won't have to stack it with the ND like I usually do.


  • Special Ed likes this

#21 contrailmaker

contrailmaker

    Surveyor 1

  • -----
  • Posts: 1639
  • Joined: 02 Jan 2009

Posted 19 May 2019 - 03:30 AM

From my current location I have found two magnification ”sweet spots” that produce consistently good planetary observing. The first one is at 271x, and the other at 380x. When these conditions exist I use my 180mm MCT or AP GTX refractor equipped with Denk binoviewer and Pentax XLs. 

 

These are very satisfying sweet spots as they produce a good image scale with lots of planetary detail during opposition and a very relaxed exit pupil size.

 

CM


  • vdog likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics