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New scope for the Mars opposition.

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#26 Cbaxter

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Posted 24 June 2020 - 03:01 PM

Wow. My experience is completely different. Not saying your experience is not what you had. But it is not how it plays out for me. I have used my 10" Dob side-by-side with my Apos for a decade and yes the 10" gets more details for planets, but at an operational cost. With the 10" one looks for those "moments of best clarity of the view" as the instrument tries to deal with the seeing and its own thermal quirks. With the refractors the characterization of the views are just the opposite as the views are for the most part always completely rock steady long term. Plus, in reality, having done so many side-by-sides, quickly realized that for the most part, the seeing controls the details -- and no way everyone out there has sub-arcsecond seeing most of the time. So when you do enough observation sampling, you quickly realize the more detailed views from the larger aperture are less often than you think. If one just goes out to observe a few times a month then statistically easy to hit a stretch of better seeing evenings skewing ones perspective. And I do have a 6" f/8 Apo and it is not a beast by any means, And when you mount them on simple alt-az mounts the entire thing is no more cumbersome than my 10" Dob to move around. And finally, while larger aperture has its place where it outperforms, like on faint fuzzies, a 10" that limits you to less than 2 degrees TFOV will mean you are missing a lot of nice open clusters and larger interesting vistas. And when the seeing is limiting magnifications, can also force you to have to move to filtration to reduce the brightness of the planet as too bright obscures features. So my experience is that the act of observing a planet has a lot more going on then simply level of details. I personally find the entire process more effective and more rewarding with a smaller refractor than with a larger mirrored instrument. That's my experience. So folks should understand both your experience and my experience as it is not a slam dunk in either direction. Where it falls for them will be something that they have to figure out in the field as it can swing either way.


It sounds like you have been observing with APOs for years and I have no doubt that you are a more experienced observer than I. The 152ed was not mine and I don't own an APO that large. The dob and SCT are mine, as well as two medium sized APOs, 110mm and 127mm and several much loved achromats. I did however have near exclusive access to the larger APO for a little over a year, thanks to a very kind work colleague, and I enjoyed the view through it so much that it made me a refractor observer convert. I may be incorrect due to my less observing experience compared to you, I am by no means the expert here, perhaps I have just yet to observe under the conditions that would allow the smaller frac to outperform the larger mirror. Though I still stand by suggesting the OP a larger apature reflector vs smaller refractor for lucky imaging Mars this year, which is the OPs intent.
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#27 Jared

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Posted 24 June 2020 - 03:15 PM

Because of reduced eyesight  ( diabetes ) I will probably use a camera / lucky imaging.

 

Arne

Using a camera? Aperture, aperture, aperture.  For this specific use (not necessarily my preference for general observing), get the classical Cassegrain. 


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#28 ArneN

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Posted 24 June 2020 - 03:17 PM

That has been my conclusion also, Jared.

 

Arne


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#29 BillP

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Posted 24 June 2020 - 03:26 PM

Thanks Bill!  The OTA will be going from that weird blue + green + silver to cranberry satin in the near future...

But I LIKE that weird blue+green+silver.  Gives it that classic-historic feel.


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#30 BillP

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Posted 24 June 2020 - 03:36 PM

It sounds like you have been observing with APOs for years and I have no doubt that you are a more experienced observer than I. The 152ed was not mine and I don't own an APO that large. The dob and SCT are mine, as well as two medium sized APOs, 110mm and 127mm and several much loved achromats. I did however have near exclusive access to the larger APO for a little over a year, thanks to a very kind work colleague, and I enjoyed the view through it so much that it made me a refractor observer convert. I may be incorrect due to my less observing experience compared to you, I am by no means the expert here, perhaps I have just yet to observe under the conditions that would allow the smaller frac to outperform the larger mirror. Though I still stand by suggesting the OP a larger apature reflector vs smaller refractor for lucky imaging Mars this year, which is the OPs intent.

Your experiences are your experiences.  Don't sell yourself short.  You are the ONLY expert in your experiences and no one can really refute what you experience.  Why I was saying mine are in the opposite realm so the true answer obviously exists on a continuum that swings from your aperture always gives you a better experience to mine that aperture does not give a better experience especially in ease of use and for rock steady views.  So it is good for others to have both viewpoints, both just as valid.  Lets everyone know that there is no one answer and it just depends as a host of variables involved that we will all weight differently per our preferences.

 

FWIW a 152 Apo can be either a beast or just a husky, all depends on how the observers goes about things.  If they must have a triplet and can only deal with gotos and tracking to observe, then yes, what they put together will be a beast for sure.  But if they are visual only then a Doublet is sufficient and if they can star hop then an alt-az is fine.  In that configuration the entire rig is not heavy at all, maybe 35-40 lbs tops.  I lift and carry it mounted so not a big deal.  But if I had it on a GEM or something, would be too much of a hassle for me and likely not to observe much with it.  Convenience really has a big impact on the observing habit.


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#31 gnowellsct

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Posted 24 June 2020 - 04:19 PM

Sorry for my interference but Bill just suggested a formula that is almost inline with my perception of the "acceptable image brightness" in respect to the aperture size. I never estimate the exit pupil size, I use the aperture size as a guide.

 

I normally use the following relationship for my astro scopes:

- D x 1.5 = ~Max useful magnification, where D is of course the aperture size. For me the higher power for a given aperture begins to give me too dim a picture for my liking regardless of the telescope type.

 

So when using my 120 mm ED I get 120 x 1.5 = 180x (I can still push up to 200x but any further and I don't like the picture any longer). Unacceptable for me.

For 152 mm ED that would be  152 x 1.5 =~ 225x (pretty close to Bill's 234x)

 

Now, how do good people on this forum manage to run a scope at triple and even higher the aperture power? What do they see? Dim blurry smudges?

For instance I often see claims that someone runs his 120ED at 300x and even 500x. I don't get it.

I routinely ran my FS128 to 300x (on Jupiter and Saturn, not on deep sky) it most definitely was not a dim blurry smudge.  you are suggesting maximum for the FS128 should be around 192x.  

 

I am not a big fan of pushing till the view dims out.  But it wasn't an issue on bright planets.  I will grant you that I did not go *past* 300x, the exit pupil issues become ridiculous.  But at f/8.1 a 4mm is half a mm exit pupil, which is "do-able", and I would use an XW 3.5, which is a tad more but still not out of line.

 

On my AP 130 (which replaced the FS128) the 3.5 mm yields 234 x and I often find that I have a bit of magnification hunger for a bit more.  That is a bit awkward to arrange, either some kind of cumbersome thing with a power mate or else the XO 2.5 mm which is 327x and not as comfortable as the XW3.5.

 

As a general rule I use 2x per mm of aperture as the practical ceiling which is actually a pretty standard rule of thumb and where the 50x per inch ceiling in the "general wisdom" comes from.   2x per mm of aperture is always 1/2 the  ocular focal length in mm of whatever scope you are using.  And it is always exactly 0.5mm exit pupil.   So on the f/8.1 FS128 a 4mm, on the f/6.3 AP130 a 3.0 mm.  Hence the utility of a 3.5mm ocular in the XW line.  It is in the territory.  

 

the 2x per mm rule has an upper boundary 712x on a 14" aperture isn't going to work most times most places (FL being an exception).  But it's very practical for scopes under 10 inches, I would think.  

 

It is true that a 0.5 mm exit pupil is not the most comfortable but with generous eye relief (such as XO 2.5 or XW 3.5) it's pretty good and delivers a good image.  It is also the maximum value suggested by Suiter in his book on optics.  

 

Anyhow the FS128 and the AP 130 can both go there and have good light with reasonable color saturation on bright planets.  Mars would qualify.  But I would not choose either of them over my C14 as "planetary" scopes.  The C14 offers 1mm exit pupil, which is generous in the high magnification world, with an 11 mm eyepiece which is 356 x.  This makes for very relaxed viewing in terms of [not having] eye strain, a lot of brightness, color saturation, and contrast, and well below the 2x per mm aperture where things cap out (as a general rule).  I've used the C14 at 500x maybe a dozen times in the past 20 years.  From what I hear pushing the limit would be more common in FL, legendary for its steady skies. 

 

But refractors should fairly routinely be able to hit 2x per mm, although I would say, I'm a lot less happy with 2x per mm in 100 and 92mm aperture refractors than I am in 130 mm class refractors.  Never had a 120.  I share your skepticism of ridiculous magnification claims, and have seen in these fora dubious claims of 3x and 4x per mm, but 2x per mm does not strike me as absurd.

 

With Mars at 30 degrees expectations should be kept low no matter what scope or aperture.

 

Greg N


Edited by gnowellsct, 24 June 2020 - 04:21 PM.

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#32 Rollo

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Posted 24 June 2020 - 09:14 PM

If not then realize you might need so filtration to cut down the brightness because a too bright planetary view masks features as well.

 

This wasn't a factor for me in all those years with an 80mm F15 refractor -- except for maybe Mars at a very close opposition.  Then, I got my first 6" scope, and saw the light -- too much of it...

 

OP, I'm a CC Fan from way back -- drew up plans for my own 40+ years ago.  I'm currently restoring my antique Tinsley 6" F20 Cass for the 3 Planet Season.  And, I finally have a trans-portable EQ mount (pedestal with big casters) that can carry a 10" CC.  If you can deal with the scope, mount, & such to where you're observing with it more than maintaining it, go with the 10" Cass...

 

I love my 2017 APM 152ED, and I'll be using it on 7 / 10 or better seeing nights at 300x (Jupiter) & 400x (Mars / Saturn).  But, my vintage Meade 8" F6 Newt is much easier to set up.  I may have to push the power up on it if the planetary disks are too bright.

 

Where it falls for them will be something that they have to figure out in the field as it can swing either way.

 

That's why I like having Options:  

 

attachicon.gifAPM ED 152 S076 (Meade SF Restore).jpgattachicon.gifMeade 826 Restore S01 - Lumicon 125 HF.jpgattachicon.gifTinsley - Progress Check S02 (Assembled).jpg

 

** Is this the 10" CC you're considering:  https://agenaastro.c...truss-tube.html

Beautiful Pictures Bob !   Nice job on everything.  bow.gif


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#33 MortonH

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Posted 25 June 2020 - 02:00 AM

I routinely ran my FS128 to 300x (on Jupiter and Saturn, not on deep sky) it most definitely was not a dim blurry smudge.  you are suggesting maximum for the FS128 should be around 192x.  

 

I am not a big fan of pushing till the view dims out.  But it wasn't an issue on bright planets.  I will grant you that I did not go *past* 300x, the exit pupil issues become ridiculous.  But at f/8.1 a 4mm is half a mm exit pupil, which is "do-able", and I would use an XW 3.5, which is a tad more but still not out of line.

 

On my AP 130 (which replaced the FS128) the 3.5 mm yields 234 x and I often find that I have a bit of magnification hunger for a bit more.  That is a bit awkward to arrange, either some kind of cumbersome thing with a power mate or else the XO 2.5 mm which is 327x and not as comfortable as the XW3.5.

 

As a general rule I use 2x per mm of aperture as the practical ceiling which is actually a pretty standard rule of thumb and where the 50x per inch ceiling in the "general wisdom" comes from.   2x per mm of aperture is always 1/2 the  ocular focal length in mm of whatever scope you are using.  And it is always exactly 0.5mm exit pupil.   So on the f/8.1 FS128 a 4mm, on the f/6.3 AP130 a 3.0 mm.  Hence the utility of a 3.5mm ocular in the XW line.  It is in the territory.  

 

the 2x per mm rule has an upper boundary 712x on a 14" aperture isn't going to work most times most places (FL being an exception).  But it's very practical for scopes under 10 inches, I would think.  

 

It is true that a 0.5 mm exit pupil is not the most comfortable but with generous eye relief (such as XO 2.5 or XW 3.5) it's pretty good and delivers a good image.  It is also the maximum value suggested by Suiter in his book on optics.  

 

Anyhow the FS128 and the AP 130 can both go there and have good light with reasonable color saturation on bright planets.  Mars would qualify.  But I would not choose either of them over my C14 as "planetary" scopes.  The C14 offers 1mm exit pupil, which is generous in the high magnification world, with an 11 mm eyepiece which is 356 x.  This makes for very relaxed viewing in terms of [not having] eye strain, a lot of brightness, color saturation, and contrast, and well below the 2x per mm aperture where things cap out (as a general rule).  I've used the C14 at 500x maybe a dozen times in the past 20 years.  From what I hear pushing the limit would be more common in FL, legendary for its steady skies. 

 

But refractors should fairly routinely be able to hit 2x per mm, although I would say, I'm a lot less happy with 2x per mm in 100 and 92mm aperture refractors than I am in 130 mm class refractors.  Never had a 120.  I share your skepticism of ridiculous magnification claims, and have seen in these fora dubious claims of 3x and 4x per mm, but 2x per mm does not strike me as absurd.

 

With Mars at 30 degrees expectations should be kept low no matter what scope or aperture.

 

Greg N

 

Agreed.  The FS-102 I owned gave great views of Mars at 287x with a Nagler zoom at 3mm.



#34 213Cobra

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Posted 25 June 2020 - 05:57 AM

For me, on planets, I see advantage to magnification up to a minimum exit pupil of 0.40mm. So on my Takahashi FSQ-106ED with QE 1.6X Extender, I get to a ~0.44mm exit pupil at ~242X with a 3.5mm Nagler.. Up to that ep point, I see more than I see on any planet than I see at lower mags @ greater ep, if seeing conditions are good.

 

If I am using my FOA-60Q as my planet bagger, my Takahashi 7mm UW yields an ep of 0.47mm @ ~129X.

 

Either one yields remarkable views of Jupiter, Saturn or Mars (given decent sky conditions and sky position) up to the limit where floaters overwhelm the possibilities of greater magnification. At that point on the FSQ I am only pushing 58X per inch of aperture. On the FOA, that ep gets me to ~55X mag per inch of aperture. Both are far within the ultimate magnification capabilities of the scopes' optics. Easy peasy; no challenge to the figure and form of the two flat field Takahashis. They are loafing it.

 

Phil 


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#35 JP-Astro

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Posted 25 June 2020 - 07:18 AM

Maybe your experience of running refractors at 2x per a mm of aperture, that is for instance 240x for a 120 aperture is associated with perfect viewing conditions?

At our location Jupiter is only at 8° at its highest point for the second season in a row. Any power above Dx1.5 makes it blurry and somewhat dim.

I see how the atmosphere badly affects sharpness of the image but honestly saying I don't know how it impairs brightness of the planets.

 

Last year when I got into astronomy I asked on this forum - what would be the reasonable minimal altitude of Jupiter for its satisfactory observation experience. No one answered my question directly that time. I figure at least 20° would be a minimum starting point and maybe 30° would be already OK but I understand that for our current 8° many experienced observers wouldn't even bother pointing their scopes at the planet.



#36 JP-Astro

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Posted 25 June 2020 - 07:30 AM

 

...

I'm a lot less happy with 2x per mm in 100 and 92mm aperture refractors than I am in 130 mm class refractors. 

...

Greg N

Greg, by the way - please explain how does aperture scaling affect useful magnification per your comment?

That is, why for a 4" refractor and below 2x per 1 m is not so good as for 5" and above?

I would expect the scaling to work proportionally but you suggest it's not a linear function.



#37 Rick Runcie

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Posted 25 June 2020 - 11:26 AM

I use up to 300x on my Tak DL routinely on Jupiter, Saturn and Mars. None of these objects are dim at that magnification. To be honest I was amazed at the saturation of color on Jupiter with the 4-inch at 300x. As a result I purchased an FS 152 for planetary observations hoping it would be similar. The Optics on the FS152 are outstanding. I also purchased a couple years ago anticipating this year's Mars opposition a Teeter 10 inch STS with a Zambuto quartz mirror. I've been observing for over 45 years with many different styles and types of telescopes up to and including a 20 in. I'm retired and I do chase the seeing by getting up when it's going to be average to good. Lately that has been in the early morning which is when the planets are favorably placed. Routinely if the seeing is average to good, the 10 in Zambuto shows more detail with the same clarity and contrast as the FS 152. The FS 152 is no slouch either I've had it up to 500x on several occasion with no image breakdown. I have owned and do own several reflectors up to 20 in all of them had premium mirrors in them. The difference is the quartz mirror I have in the 10" Teeter telescope. It adjusts almost simultaneously to conditions and keeps up with the temperature falling. I have never had a reflector show me the image consistently so sharp and full of contrast like the Quartz mirror. It really is refractor like and more than not it is the only telescope I set up because it blows everything else out of the water most of the time. I've used close to 700 power on planetary nebula and that has revealed more detail then less magnification. Now you would think I live in Florida or California with good seeing. Not the case, I live in New Jersey. But even in New Jersey we get decent to good seeing at times. You just have to be aware of the weather patterns. Being retired allows me the luxury to be able to observe on a moment's notice and having that 10" Quartz mirror available makes those instances more rewarding because I can be observing so quickly. I read often how people can't wait till the planets move into the evening sky to observe them. Around here unless it's right after sundown the seeing is usually the poorest at that time. I always enjoy more observing the planets in the early morning because the seeing is usually a lot better.


Edited by Rick Runcie, 25 June 2020 - 12:56 PM.

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#38 213Cobra

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Posted 25 June 2020 - 11:31 AM

Maybe your experience of running refractors at 2x per a mm of aperture, that is for instance 240x for a 120 aperture is associated with perfect viewing conditions?

At our location Jupiter is only at 8° at its highest point for the second season in a row. Any power above Dx1.5 makes it blurry and somewhat dim.

I see how the atmosphere badly affects sharpness of the image but honestly saying I don't know how it impairs brightness of the planets.

 

Last year when I got into astronomy I asked on this forum - what would be the reasonable minimal altitude of Jupiter for its satisfactory observation experience. No one answered my question directly that time. I figure at least 20° would be a minimum starting point and maybe 30° would be already OK but I understand that for our current 8° many experienced observers wouldn't even bother pointing their scopes at the planet.

Not perfect but very good to exceptional. I'm not running 2X/mm or more looking at Jupiter through a boiling sky. While I am under the Los Angeles light dome, I do get a reasonable incidence of nights with very good to exceptional seeing, which for planets is far more enabling than light pollution is disabling.

 

Phil



#39 Bomber Bob

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Posted 25 June 2020 - 11:35 AM

Beautiful Pictures Bob !   Nice job on everything.  bow.gif

Thanks!  I think this is the first 3 Planet Season where I've been over-prepared with 6" or larger scopes (my excellent '71 RV-6 isn't in the post)... so, I hope that doesn't jinx the weather!



#40 Rick Runcie

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Posted 25 June 2020 - 11:41 AM

I would probably observe planets at whatever altitude at its highest point at my latitude just to observe them. Where I live I notice a difference between 25 degrees and 30 degrees when viewing the planets. Usually the detail starts smearing and Rippling at around 25 degrees at 30 degrees the image is usually pretty steady. I imagine below 20 degrees the image would be unacceptable for any amount of detail I would be looking for most of the time. If I lived at a lower latitude though I would still observe them I just wouldn't sketch them like I normally do when they reach around 30 degrees. But those are the conditions that I am used to at my location. I see sketches from people that live far more north than I. They have better seeing than I and they produce unbelievable sketches. It has has more to do with your local conditions than anything else and you really can't generalize on that.

#41 gnowellsct

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Posted 25 June 2020 - 05:56 PM

Greg, by the way - please explain how does aperture scaling affect useful magnification per your comment?

That is, why for a 4" refractor and below 2x per 1 m is not so good as for 5" and above?

I would expect the scaling to work proportionally but you suggest it's not a linear function.

It is non linear.  The light gathering of a four inch instrument is about 12 square inches.  A 5 inch is about 19.    19/12=1.58 or nearly a 60% increase in light gathering compared to 5/4=1.25 a 25% increase in diameter.

 

There are different kinds of strain involved.  There is a particular sort of strain that sets in with long periods at .5 mm exit pupil.   There is another kind of strain that I associate with trying to eke details out of an image that is too dim.  The FS128 at 300x gives a much brighter view and shows more detail than my former Vixen 102 at 180x.  With brightness colors come out. 

 

About 15% of the male population has red/green color blindness (to a degree).  That population includes one of my best friends and my son.  Some of the observers with diminished R/G sensitivity may be the ones reporting that they don't see loss of color on Jupiter and Saturn when they pushed to extreme magnifications.  (i.e. they never saw the color to begin with--not much of it, anyhow)

 

This is all relative of course.  The color in the FS128 did not approach the color hues in the C14. 

 

In any event there are a number of people here who love the challenge of observing in a scope 80mm and under, and I myself have masked down my 81mm to see what kinds of views were to be had at 40 mm.   But last night I had my 92mm on top of my 130 mm and the differences were rather evident.  Never mind that I saw the rings of Saturn in a 40mm.

 

To sum up, 2x per mm is a figure which scales exactly with .5 exit pupil and is thus one major threshold with relation to the organic structure of the eye.  Once you hit that .5 mm region the views improve with more aperture.  Small scopes at .5 mm exit pupils don't have a lot of light to deliver, and under 5 inches details and colors are hard to tease out.  Not impossible, but hard.  And, well, some details would be impossible.  I tried hard last night to see the same details in the 92 that I could in the 130.  It just didn't work.  And both scopes are premium glass.

 

Greg N


Edited by gnowellsct, 25 June 2020 - 05:57 PM.

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#42 JP-Astro

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Posted 25 June 2020 - 06:38 PM

Deleted and moved to a separate thread:

https://www.cloudyni...ler-refractors/


Edited by JP-Astro, 26 June 2020 - 08:09 AM.


#43 Jared

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Posted 25 June 2020 - 07:33 PM

Guys and gals, everyone keeps posting about optimum magnifications, exit pupils, and the like.  That’s certainly an interesting and worthwhile discussion normally, but did nobody notice the OP intends to use a web cam/lucky imaging for Mars viewing this opposition, not eyepieces?  In light of that, what would be your recommendation? Seems to me a 10” classical Cassegrain is likely to provide better results with even basic image processing than a 6” refractor (much as I love refractors).  Ask any planetary imager and they will take aperture above almost any other attribute. Do you disagree in light of the intended use?  Imaging, not eyeballs?



#44 Bomber Bob

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Posted 25 June 2020 - 07:56 PM

Arne is in Norway, and has an observatory... 10" or 12" Cass, even though Mars will be low from up there...

 

Down here at The Swamp, on an 8 / 10 planetary seeing night, Mars in a 10" CC would be BRIGHT -- I'd probably have to stack a couple of Moon filters to dim it...



#45 Nippon

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Posted 25 June 2020 - 08:50 PM

From my experience Mars is one object that benefits visually from a scope with extremely good color correction. Some ED doublets have a slight red shift that hinders the view of Mars. I would lean toward a good reflector, good triplet or fluorite.


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#46 gnowellsct

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Posted 25 June 2020 - 11:17 PM

Guys and gals, everyone keeps posting about optimum magnifications, exit pupils, and the like.  That’s certainly an interesting and worthwhile discussion normally, but did nobody notice the OP intends to use a web cam/lucky imaging for Mars viewing this opposition, not eyepieces?  In light of that, what would be your recommendation? Seems to me a 10” classical Cassegrain is likely to provide better results with even basic image processing than a 6” refractor (much as I love refractors).  Ask any planetary imager and they will take aperture above almost any other attribute. Do you disagree in light of the intended use?  Imaging, not eyeballs?

The kind of results Damian Peach gets with a C14.  It is true that in the last year or two he has had access to something like a 40 inch aperture, but the bulk of his work over two decades has been with a C14.

 

http://damianpeach.com/mars1314.htm


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#47 Daniel Mounsey

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Posted 26 June 2020 - 01:03 AM

Guys and gals, everyone keeps posting about optimum magnifications, exit pupils, and the like.  That’s certainly an interesting and worthwhile discussion normally, but did nobody notice the OP intends to use a web cam/lucky imaging for Mars viewing this opposition, not eyepieces?  In light of that, what would be your recommendation? Seems to me a 10” classical Cassegrain is likely to provide better results with even basic image processing than a 6” refractor (much as I love refractors).  Ask any planetary imager and they will take aperture above almost any other attribute. Do you disagree in light of the intended use?  Imaging, not eyeballs?

Jared,

Glad you're staying on topic. Not trying to be hard but what classical cass are we talking about and what did the OP say about imaging? Nobody is making a good classical cass these days. The design is a nightmare to do properly. All this talk about classical cass's and nobody is even sharing a review. Also, imaging and visual are black & white issues and do not belong in the same discussions. I would share reviews on the design but I CAN'T. I'm a vendor. 


Edited by Daniel Mounsey, 26 June 2020 - 01:05 AM.

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#48 ArneN

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Posted 26 June 2020 - 01:56 AM

To me, a refractor guy, any mirror- based scope will be a challenge re collimation. But the reviews the new GSO CCs have got here at CN plus Dennis´ in S&T are great.

So I have narrowed it to either a 10 inch CC or a Celestron 9,25 SCT.

I have this summer to think while I am building my RR.

And then there is the mount..........

 

Arne


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#49 ArneN

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Posted 26 June 2020 - 04:55 AM

And I wonder what the opinions would have been if I raised this same question in the Cat/Cass forum?
 

Arne



#50 BillP

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Posted 26 June 2020 - 06:17 AM

That has been my conclusion also, Jared.

 

Arne

What does "using a camera" mean exactly? 

  1. Are you going to hold your iPhone up to the eyepiece and snap a pix? 
  2. Or are you going to mount a digital camera on an eyepiece like a Hyperion to shoot pix? 
  3. Or are you going to get a dedicated astro-imaging camera and stack images and do lots of post processing? 

1 and 2 do not really require must skill, and can get away with any mount when taking pics of bright objects.  3 though requires skill and a rock-solid and very expensive tracking mount for any large instrument, plus lots of time at the computer doing post processing.  Are you already adept at doing #3 or will this be new to you?  And what is your primary desire for using a camera -- shoot pics of Moon, planets, closeup DSO, widefield DSO?  Anyway, kind of need to know where you are coming from with the "use a camera" to make reasonable recommendations.

 

And if #3 is the primary intent, then not sure an f/12 CC would be the wisest choice unless one can get a strong reducer to get the focal ratio for a more reasonable for imaging number.  Otherwise your exposures will need to be long which means the mount needs to be be much more precise.  Many refractors have dedicated reducer/flatteners.  But if imaging is the primary and the plan is to go deep rather than wide, then C8, C9.25, C11, C14 would be more convenient and imaging accessory-laden platforms, especially with Faststar.  If planetary the primary then C11 of not C14.


Edited by BillP, 26 June 2020 - 06:33 AM.



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